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Sample records for macroinvertebrates dissolved oxygen

  1. Dissolved oxygen

    National Research Council Canada - National Science Library

    1981-01-01

    Dissolved oxygen concentrations in the waters of Botany Bay and Georges and Cooks Rivers vary mainly as a result of tidal water movements, algal and macrophytic growth and decay, and effects of storms...

  2. Are macroinvertebrates in high altitude streams affected by oxygen deficiency?

    DEFF Research Database (Denmark)

    Jacobsen, Dean; Rostgaard, S.; Vásconez, J. J.

    2003-01-01

    conditions. However, this fails to take into account that oxygen solubility declines with decreasing atmospheric pressure, which may be of importance at high altitudes. 2. Based on samples of macroinvertebrate benthos and in situ measurements of respiratory oxygen demand of macroinvertebrates in small...

  3. Understanding Your Watershed Fact Sheet: Dissolved Oxygen

    OpenAIRE

    Mesner, Nancy; Geiger, John

    2010-01-01

    Dissolved oxygen describes oxygen molecules which have actually dissolved in water. Sometimes people confuse bubbles in water with dissolved oxygen, but in reality the dissolved form of oxygen cannot be seen.

  4. The Measurement of Dissolved Oxygen

    Science.gov (United States)

    Thistlethwayte, D.; And Others

    1974-01-01

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

  5. Low oxygen pressure as a driving factor for the altitudinal decline in taxon richness of stream macroinvertebrates

    DEFF Research Database (Denmark)

    Jacobsen, Dean

    2008-01-01

    with increasing altitude is mainly caused by a decrease in oxygen saturation rather than by a decrease in temperature. Levels of oxygen saturation such as those found at high altitudes do not appear to be lethal to any species, but could affect macroinvertebrates through long-term, sub-lethal effects. I suggest......'s alpha index and rarefied richness) decreased with increasing altitude. The MDE null model, water temperature and dissolved oxygen also decreased with altitude, while other measured variables were uncorrelated with altitude. Minimum oxygen saturation had the highest explanatory power of the density...... and only significant effect on density-corrected richness. The relationship between richness and oxygen corrected for the effect of altitude (using analyses of double residuals) was significant, whereas that of richness versus temperature was not. The results indicate that the decrease in richness...

  6. Purging dissolved oxygen by nitrogen bubble aeration

    Science.gov (United States)

    Yamashita, Tatsuya; Ando, Keita

    2016-11-01

    We apply aeration with nitrogen microbubbles to water in order to see whether oxygen gas originally dissolved in the water at one atmosphere is purged by the aeration. The concentration of dissolved oxygen (DO) is detected by a commercial DO meter. To detect the dissolved nitrogen (DN) level, we observe the growth of millimetre-sized bubbles nucleated at glass surfaces in contact with the aerated water and compare it with the Epstein-Plesset theory that accounts for DO/DN diffusions and the presence of the glass surfaces. Comparisons between the experiment and the theory suggest that the DO in the water are effectively purged by the aeration.

  7. Modeling Fish Growth in Low Dissolved Oxygen

    Science.gov (United States)

    Neilan, Rachael Miller

    2013-01-01

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

  8. Water quality: determination of dissolved oxygen : electrochemical probe method

    National Research Council Canada - National Science Library

    2012-01-01

    ISO 5814:2012 specifies an electrochemical method for the determination of dissolved oxygen in water by means of an electrochemical cell which is isolated from the sample by a gas permeable membrane...

  9. Diurnal fluctuations in root oxygen release rate and dissolved oxygen budget in wetland mesocosm

    OpenAIRE

    Dong, C.; Zhu, W; Zhao, Y. Q.; Gao, M

    2011-01-01

    To assess the role of plants for oxygen offering in constructed wetlands, this study experimentally evaluated the amount of root oxygen release rate using mass balance method. The mass balance calculation is based on the following components: respiratory oxygen consumption of the roots; oxygen required for degradation of the organic matters; oxygen required for nitrification; and the amount of dissolved oxygen in the influent, effluent and substrate water. Experimental results have demonstrat...

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

    Directory of Open Access Journals (Sweden)

    Nader Shehata

    2015-08-01

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

  11. Continuous Dissolved Oxygen Measurements and Modelling Metabolism in Peatland Streams

    OpenAIRE

    2016-01-01

    Stream water dissolved oxygen was monitored in a 3.2km2 moorland headwater catchment in the Scottish Highlands. The stream consists of three 1st order headwaters and a 2nd order main stem. The stream network is fringed by peat soils with no riparian trees, though dwarf shrubs provide shading in the lower catchment. Dissolved oxygen (DO) is regulated by the balance between atmospheric re-aeration and the metabolic processes of photosynthesis and respiration. DO was continuously measured for >1...

  12. Dissolved oxygen concentration affects hybrid striped bass growth

    Science.gov (United States)

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

  13. Investigating Factors that Affect Dissolved Oxygen Concentration in Water

    Science.gov (United States)

    Jantzen, Paul G.

    1978-01-01

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

  14. Dissolved oxygen imaging to investigate biodegradation at lab scale

    Science.gov (United States)

    Lerner, D. N.; Rees, H.; Huang, W. E.; Smith, C. C.; Oswald, S. E.

    2003-04-01

    A novel combination of a non-invasive imaging method with an oxygen sensitive fluorescent indicator was developed to investigate the biodegradation processes occurring at the fringe of a solute plume. A thin transparent porous matrix was made from quartz plates and quartz sand and acetate was continuously injected in the uniform flow field containing dissolved oxygen. Ruthenium (II)-dichlorotris(1,10-phenanthroline) (Ru(phen)3Cl2), a water soluble fluorescent dye, was used as an indicator of dissolved oxygen concentration as its fluorescence intensity is dependent on the concentration of oxygen. The oxygen distribution within the matrix was interpreted from images recorded by a CCD camera. These two-dimensional experimental results show quantitatively how the oxygen concentrations decrease strongly at the narrow plume fringe and that oxygen was exhausted at the core of the plume. Separately, dispersivity was measured in a series of non-reactive transport experiments, and biodegradation parameters were evaluated by batch experiments. This measurement method provides a novel approach to investigate details of behavior of solute transport and biodegradation in porous media.

  15. Ion fluxes in silver catfish (Rhamdia quelen) juveniles exposed to different dissolved oxygen levels

    OpenAIRE

    Felipe Link de Rosso; Keidi C. S. Bolner; Bernardo Baldisserotto

    2006-01-01

    Low dissolved oxygen levels in the water (hypoxia) can be provoked by oxygen consumption by fish and other organisms, organic matter decomposition, phytoplankton blooms, and temperature increase. The objective of the present study was to investigate Na+, Cl-, K+, and ammonia fluxes in silver catfish (Rhamdia quelen) exposed to different dissolved oxygen levels. Juveniles (9 ± 1g) maintained at 6.0 mg.L-1 dissolved oxygen were transferred to four 40 L aquaria with different dissolved oxygen le...

  16. Modeling impact of storage zones on stream dissolved oxygen

    Science.gov (United States)

    Chapra, S.C.; Runkel, R.L.

    1999-01-01

    The Streeter-Phelps dissolved oxygen model is modified to incorporate storage zones. A dimensionless number reflecting enhanced decomposition caused by the increased residence time of the biochemical oxygen demand in the storage zone parameterizes the impact. This result provides a partial explanation for the high decomposition rates observed in shallow streams. An application suggests that the storage zone increases the critical oxygen deficit and moves it closer to the point source. It also indicates that the storage zone should have lower oxygen concentration than the main channel. An analysis of a dimensionless enhancement factor indicates that the biochemical oxygen demand decomposition in small streams could be up to two to three times more than anticipated based on the standard Streeter-Phelps model without storage zones. For larger rivers, enhancements of up to 1.5 could occur.The Streeter-Phelps dissolved oxygen model is modified to incorporate storage zones. A dimensionless number reflecting enhanced decomposition caused by the increased residence time of the biochemical oxygen demand in the storage zone parameterizes the impact. This result provides a partial explanation for the high decomposition rates observed in shallow streams. An application suggests that the storage zone increases the critical oxygen deficit and moves it closer to the point source. It also indicates that the storage zone should have lower oxygen concentration than the main channel. An analysis of a dimensionless enhancement factor indicates that the biochemical oxygen demand decomposition in small streams could be up to two to three times more than anticipated based on the standard Streeter-Phelps model without storage zones. For larger rivers, enhancements of up to 1.5 could occur.

  17. Improved arterial blood oxygenation following intravenous infusion of cold supersaturated dissolved oxygen solution.

    Science.gov (United States)

    Grady, Daniel J; Gentile, Michael A; Riggs, John H; Cheifetz, Ira M

    2014-01-01

    One of the primary goals of critical care medicine is to support adequate gas exchange without iatrogenic sequelae. An emerging method of delivering supplemental oxygen is intravenously rather than via the traditional inhalation route. The objective of this study was to evaluate the gas-exchange effects of infusing cold intravenous (IV) fluids containing very high partial pressures of dissolved oxygen (>760 mm Hg) in a porcine model. Juvenile swines were anesthetized and mechanically ventilated. Each animal received an infusion of cold (13 °C) Ringer's lactate solution (30 mL/kg/hour), which had been supersaturated with dissolved oxygen gas (39.7 mg/L dissolved oxygen, 992 mm Hg, 30.5 mL/L). Arterial blood gases and physiologic measurements were repeated at 15-minute intervals during a 60-minute IV infusion of the supersaturated dissolved oxygen solution. Each animal served as its own control. Five swines (12.9 ± 0.9 kg) were studied. Following the 60-minute infusion, there were significant increases in PaO2 and SaO2 (P dissolved oxygen solution may be intravenously administered to improve arterial blood oxygenation and ventilation parameters and induce a mild therapeutic hypothermia in a porcine model.

  18. Functional State Modelling of Cultivation Processes: Dissolved Oxygen Limitation State

    Directory of Open Access Journals (Sweden)

    Olympia Roeva

    2015-04-01

    Full Text Available A new functional state, namely dissolved oxygen limitation state for both bacteria Escherichia coli and yeast Saccharomyces cerevisiae fed-batch cultivation processes is presented in this study. Functional state modelling approach is applied to cultivation processes in order to overcome the main disadvantages of using global process model, namely complex model structure and a big number of model parameters. Alongwith the newly introduced dissolved oxygen limitation state, second acetate production state and first acetate production state are recognized during the fed-batch cultivation of E. coli, while mixed oxidative state and first ethanol production state are recognized during the fed-batch cultivation of S. cerevisiae. For all mentioned above functional states both structural and parameter identification is here performed based on experimental data of E. coli and S. cerevisiae fed-batch cultivations.

  19. Biogeochemical modelling of dissolved oxygen in a changing ocean.

    Science.gov (United States)

    Andrews, Oliver; Buitenhuis, Erik; Le Quéré, Corinne; Suntharalingam, Parvadha

    2017-09-13

    Secular decreases in dissolved oxygen concentration have been observed within the tropical oxygen minimum zones (OMZs) and at mid- to high latitudes over the last approximately 50 years. Earth system model projections indicate that a reduction in the oxygen inventory of the global ocean, termed ocean deoxygenation, is a likely consequence of on-going anthropogenic warming. Current models are, however, unable to consistently reproduce the observed trends and variability of recent decades, particularly within the established tropical OMZs. Here, we conduct a series of targeted hindcast model simulations using a state-of-the-art global ocean biogeochemistry model in order to explore and review biases in model distributions of oceanic oxygen. We show that the largest magnitude of uncertainty is entrained into ocean oxygen response patterns due to model parametrization of pCO2-sensitive C : N ratios in carbon fixation and imposed atmospheric forcing data. Inclusion of a pCO2-sensitive C : N ratio drives historical oxygen depletion within the ocean interior due to increased organic carbon export and subsequent remineralization. Atmospheric forcing is shown to influence simulated interannual variability in ocean oxygen, particularly due to differences in imposed variability of wind stress and heat fluxes.This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'. © 2017 The Author(s).

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

    Science.gov (United States)

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

    2012-10-01

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

  1. Effect of correlated inputs on DO (dissolved oxygen) uncertainty

    Energy Technology Data Exchange (ETDEWEB)

    Brown, L.C.; Song, Q.

    1988-06-01

    Although uncertainty analysis has been discussed in recent water-quality-modeling literature, much of the work has assumed that all input variables and parameters are mutually independent. The objective of this paper is to evaluate the importance of correlation among the model inputs in the study of model-output uncertainty. The model used for demonstrating the influence of input-variable correlation is the Streeter-Phelps dissolved oxygen equation. The model forms the basis of many of the water-quality models currently in use and the relationships between model inputs and output-state variables are well understood.

  2. Measurement and simulation of dissolved oxygen in Zayandehrood river

    Directory of Open Access Journals (Sweden)

    Ahmad Reza Rahsepar

    2012-01-01

    Full Text Available Aims: This study aims to simulate dissolved oxygen of Zayandehrood river from regulating dam to Polle-Kalleh bridge using MIKE11 software that is a hydrodynamics and water quality model. Materials and Methods: During 5 months the samples were taken from four hydrometric stations and water quality parameters such as dissolved oxygen, pH, BOD (1 day, 3 days, 5 days, and 7 days, NH 4 , NO 3 - phosphate (PO4 3- , and temperature were measured. Morphological and hydrological data were provided and introduced into the model. The model was calibrated and its accuracy was investigated. Results: The results indicated that concentration of PO4 3- , BOD5 , COD, NH 4 , and NO3 - exceeded surface water standards from regulating dam to Pole-Kalleh bridge. The results of the prediction for the next 25 years indicated that due to growth of population and industries along the river, concentration of some pollutants will be increased. Conclusions: The results indicated that although the current DO level is suitable for aquatic environment, this is not adequate for fish reproduction and migration. Prediction of the river water quality parameters for the future conditions showed that discharge of urban and rural wastewater to river should be avoided. In situations where release of effluent into the river is inevitable, nitrification process should be added to wastewater treatment processes.

  3. Simultaneous nitrogen and phosphorus removal under low dissolved oxygen conditions

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A full-scale test was operated by using low dissolved oxygen activated sludge process to enhance biological nitrogen and phosphorus removal. When the influent concentrations of CODCr, TN and TP varied in a range of 352.9 mg/L-1338.2 mg/L, 34.4 mg/L-96.3 mg/L, and 2.21 mg/L-24.0 mg/L, the average removal efficiencies were 94.9%, 86.7% and 93.0%, respectively. During the test period of two months, effluent meas of CODCr, BOD5, NH3-N, TN and TP were below 50 mg/L, 25 mg/L, 10 mg/L and 1.0 mg/L, respectively. The low dissolved oxygen activated sludge process has a simple flow sheet, fewer facilities and high N and P removal efficiency. It is very convenient to retrofit the conventional activated sludge process with the above process.

  4. Photoacoustic lifetime imaging of dissolved oxygen using methylene blue

    Science.gov (United States)

    Ashkenazi, Shai

    2010-07-01

    Measuring distribution of dissolved oxygen in biological tissue is of prime interest for cancer diagnosis, prognosis, and therapy optimization. Tumor hypoxia indicates poor prognosis and resistance to radiotherapy. Despite its major clinical significance, no current imaging modality provides direct imaging of tissue oxygen. We present preliminary results demonstrating the potential of photoacoustic lifetime imaging (PALI) for noninvasive, 3-D imaging of tissue oxygen. The technique is based on photoacoustic probing of the excited state lifetime of methylene blue (MB) dye. MB is an FDA-approved water soluble dye with a peak absorption at 660 nm. A double pulse laser system (pump probe) is used to excite the dye and probe its transient absorption by detecting photoacoustic emission. The relaxation rate of MB depends linearly on oxygen concentration. Our measurements show high photoacoustic signal contrast at a probe wavelength of 810 nm, where the excited state absorption is more than four times higher than the ground state absorption. Imaging of a simple phantom is demonstrated. We conclude by discussing possible implementations of the technique in clinical settings and combining it with photodynamic therapy (PDT) for real-time therapy monitoring.

  5. Influence of dissolved oxygen convection on well sampling

    Science.gov (United States)

    Vroblesky, D.A.; Casey, C.C.; Lowery, M.A.

    2007-01-01

    Convective transport of dissolved oxygen (D.O.) from shallow to deeper parts of wells was observed as the shallow water in wells in South Carolina became cooler than the deeper water in the wells due to seasonal changes. Wells having a relatively small depth to water were more susceptible to thermally induced convection than wells where the depth to water was greater because the shallower water levels were more influenced by air temperature. The potential for convective transport of D.O. to maintain oxygenated conditions in a well screened in an anaerobic aquifer was diminished as ground water exchange through the well screen increased and as oxygen demand increased. Transport of D.O. to the screened interval can adversely affect the ability of passive samplers to produce accurate concentrations of oxygen-sensitive solutes such as iron, other redox indicators, and microbiological data. A comparison of passive sampling to low-flow sampling in a well undergoing convection, however, showed general agreement of volatile organic compound concentrations. During low-flow sampling, the pumped water may be a mixture of convecting water from within the well casing and aquifer water moving inward through the screen. This mixing of water during low-flow sampling can substantially increase equilibration times, can cause false stabilization of indicator parameters, can give false indications of the redox state, and can provide microbiological data that are not representative of the aquifer conditions. Data from this investigation show that simple in-well devices can effectively mitigate convective transport of oxygen. The devices can range from inflatable packers to simple, inexpensive baffle systems. ?? 2007 National Ground Water Association.

  6. Uncertainty analysis in dissolved oxygen modeling in streams.

    Science.gov (United States)

    Hamed, Maged M; El-Beshry, Manar Z

    2004-08-01

    Uncertainty analysis in surface water quality modeling is an important issue. This paper presents a method based on the first-order reliability method (FORM) to assess the exceedance probability of a target dissolved oxygen concentration in a stream, using a Streeter-Phelps prototype model. Basic uncertainty in the input parameters is considered by representing them as random variables with prescribed probability distributions. Results obtained from FORM analysis compared well with those of the Monte Carlo simulation method. The analysis also presents the stochastic sensitivity of the probabilistic outcome in the form of uncertainty importance factors, and shows how they change with changing simulation time. Furthermore, a parametric sensitivity analysis was conducted to show the effect of selection of different probability distribution functions for the three most important parameters on the design point, exceedance probability, and importance factors.

  7. Climate cycles and dissolved oxygen variability off eastern Luzon, Philippines

    Science.gov (United States)

    Escobar, M.; San Diego-McGlone, M.; Jacinto, G.; Siringan, F.; Villanoy, C.; Gordon, A. L.

    2013-12-01

    We assess the effect of El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) on the variability of dissolved oxygen off eastern Luzon, Philippines. In this area, bifurcation of the North Equatorial Current (NEC) into the Kuroshio and Mindanao Currents occurs. Hydrographic parameters and sediment cores obtained during the oceanographic cruises in 2011 and 2012, and data from the World Ocean Atlas 2009 (WOA09) were used in the study. Variability in dissolved oxygen (DO) concentration was observed from surface to the thermocline between the neutral (2011) and La Niña (2012) phase. Based on optimum multiparameter analysis, there was a change in the fraction of water masses in the area. Under neutral conditions, waters off eastern Luzon consist mainly of water (NPSW) from the Kuroshio recirculation gyre that contain higher DO. In contrast, during La Niña conditions the North Equatorial Current becomes stronger bringing in water (NPTW) with lower DO. Thus, variability in DO off eastern Luzon is influenced by the change in the source of the water mass arising from the shift in bifurcation latitude that is linked to ENSO. Longer-term variability in DO was examined using a 2.15m sediment core taken in the shelf off eastern Luzon. The sediment record was used to reconstruct the depositional redox environment in the last 1000 years. The elements V, Ni, Cr, Mn and Fe were normalized to Ti and used as chemical proxies to track DO variability. Results show that DO fluctuations have occurred in the past, and these changes are in agreement with DO variability driven by the Pacific Decadal Oscillation.

  8. Consumption and diffusion of dissolved oxygen in sedimentary rocks.

    Science.gov (United States)

    Manaka, M; Takeda, M

    2016-10-01

    Fe(II)-bearing minerals (e.g., biotite, chlorite, and pyrite) are a promising reducing agent for the consumption of atmospheric oxygen in repositories for the geological disposal of high-level radioactive waste. To estimate effective diffusion coefficients (De, in m(2)s(-1)) for dissolved oxygen (DO) and the reaction rates for the oxidation of Fe(II)-bearing minerals in a repository environment, we conducted diffusion-chemical reaction experiments using intact rock samples of Mizunami sedimentary rock. In addition, we conducted batch experiments on the oxidation of crushed sedimentary rock by DO in a closed system. From the results of the diffusion-chemical reaction experiments, we estimated the values of De for DO to lie within the range 2.69×10(-11)concentration of reactive sites was about 10(-4)molm(-2) from batch experiments. In contrast, the value of reactive sites estimated from the physical surface area was about 10(-8)molm(-2), indicating that the reaction within intact rock is limited to the sites that originally existed with accessible porosity for O2(aq). This difference arises because the batch experiments used powdered samples, meaning that new sites which formed during milling were added to the original reaction sites. On the basis of these observations and interpretations, diffusion-chemical reaction experiments make it possible to determine the values of the kinetic parameter and diffusivity for an intact rock sample simultaneously. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Dissolved oxygen saturation controls PAH biodegradation in freshwater estuary sediments.

    Science.gov (United States)

    Boyd, T J; Montgomery, M T; Steele, J K; Pohlman, J W; Reatherford, S R; Spargo, B J; Smith, D C

    2005-02-01

    Polycyclic aromatic hydrocarbons (PAHs) are common contaminants in terrestrial and aquatic environments and can represent a significant constituent of the carbon pool in coastal sediments. We report here the results of an 18-month seasonal study of PAH biodegradation and heterotrophic bacterial production and their controlling biogeochemical factors from 186 sediment samples taken in a tidally influenced freshwater estuary. For each sampling event, measurements were averaged from 25-45 stations covering approximately 250 km(2). There was a clear relationship between bacterial production and ambient temperature, but none between production and bottom water dissolved oxygen (DO) % saturation or PAH concentrations. In contrast with other studies, we found no effect of temperature on the biodegradation of naphthalene, phenanthrene, or fluoranthene. PAH mineralization correlated with bottom water DO saturation above 70% (r(2) > 0.99). These results suggest that the proportional utilization of PAH carbon to natural organic carbon is as much as three orders of magnitude higher during cooler months, when water temperatures are lower and DO % saturation is higher. Infusion of cooler, well-oxygenated water to the water column overlying contaminated sediments during the summer months may stimulate PAH metabolism preferentially over non-PAH organic matter.

  10. Effect of Dissolved Oxygen on Operation of EGSB

    Institute of Scientific and Technical Information of China (English)

    LI Hui-li; L(U) Bing-nan; LI Qing-wei

    2007-01-01

    An expanded granular sludge bed (EGSB) reactor was adopted to study the dissolved oxygen (DO) effect on the operation. With the chemical oxygen demand (COD) 800-1800mg/L, pH6.0-7.3, volume loading rate (VLR) 5.4-11.5kg COD/(m3·d), the operational behaviors of EGSB reactor was researched. And the max DO concentration which influenced steady operation of EGSB reactor was determined by contrasting the changes due to different concentrations of the influent DO. With the COD 1200-2000mg/L, VLR 7.2-12.0kg COD/(m3·d), the operational characteristic of EGSB reactor was researched by aerating the recycle effluent. The results was: when the DO concentration of influent was under 3.0mg/L, the removal efficiency of COD was 82%-90% and the operation of the EGSB reactor was steady; when the DO concentration of influent was over 3.0mg/L, the oxidationreduction potential (ORP) fluctuated greatly and the operation of the EGSB reactor was instable; the acidified wastewater of saccharide whose pH value was 5.1-6.5 could be treated by aerating the recycle effluent and the efficiency of COD was up to 85%-92%.

  11. Modelling Dissolved Oxygen/Sediment Oxygen Demand under Ice in a Shallow Eutrophic Prairie Reservoir

    Directory of Open Access Journals (Sweden)

    Julie A. Terry

    2017-02-01

    Full Text Available Dissolved oxygen is an influential factor of aquatic ecosystem health. Future predictions of oxygen deficits are paramount for maintaining water quality. Oxygen demands depend greatly on a waterbody’s attributes. A large sediment–water interface relative to volume means sediment oxygen demand has greater influence in shallow systems. In shallow, ice-covered waterbodies the potential for winter anoxia is high. Water quality models offer two options for modelling sediment oxygen demand: a zero-order constant rate, or a sediment diagenesis model. The constant rate is unrepresentative of a real system, yet a diagenesis model is difficult to parameterise and calibrate without data. We use the water quality model CE-QUAL-W2 to increase the complexity of a zero-order sediment compartment with limited data. We model summer and winter conditions individually to capture decay rates under-ice. Using a semi-automated calibration method, we find an annual pattern in sediment oxygen demand that follows the trend of chlorophyll-a concentrations in a shallow, eutrophic Prairie reservoir. We use chlorophyll-a as a proxy for estimation of summer oxygen demand and winter decay. We show that winter sediment oxygen demand is dependent on the previous summer’s maximum chlorophyll-a concentrations.

  12. Influence of dissolved oxygen concentration on the pharmacokinetics of alcohol in humans.

    Science.gov (United States)

    Baek, In-hwan; Lee, Byung-yo; Kwon, Kwang-il

    2010-05-01

    Ethanol oxidation by the microsomal ethanol oxidizing system requires oxygen for alcohol metabolism, and a higher oxygen uptake increases the rate of ethanol oxidation. We investigated the effect of dissolved oxygen on the pharmacokinetics of alcohol in healthy humans (n = 49). The concentrations of dissolved oxygen were 8, 20, and 25 ppm in alcoholic drinks of 240 and 360 ml (19.5% v/v). Blood alcohol concentrations (BACs) were determined by converting breath alcohol concentrations. Breath samples were collected every 30 min when the BAC was higher than 0.015%, 20 min at BAC dissolved oxygen groups (20, 25 ppm) descended to 0.000% and 0.050% BAC faster than the normal dissolved oxygen groups (8 ppm; p oxygen groups were lower than in the normal oxygen group, while C(max) and T(max) were not significantly affected. In a Monte Carlo simulation, the lognormal distribution of mean values of AUC(inf) and t(1/2) was expected to be reduced in the high oxygen group compared to the normal oxygen group. In conclusion, elevated dissolved oxygen concentrations in alcoholic drinks accelerate the metabolism and elimination of alcohol. Thus, enhanced dissolved oxygen concentrations in alcohol may have a role to play in reducing alcohol-related side effects and accidents.

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

    Science.gov (United States)

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

    1996-01-01

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

  14. The dynamics of dissolved oxygen concentration for water quality monitoring and assessment in polder ditches

    NARCIS (Netherlands)

    Veeningen, R.

    1983-01-01

    This study deals with the use of the dynamics of dissolved oxygen concentration for water quality assessment in polder ditches. The dynamics of the dissolved oxygen concentration, i.e. the temporal and spatial variations in a few polder ditches under a range of natural, pollution and management

  15. Artificial neural network modeling of dissolved oxygen in reservoir.

    Science.gov (United States)

    Chen, Wei-Bo; Liu, Wen-Cheng

    2014-02-01

    The water quality of reservoirs is one of the key factors in the operation and water quality management of reservoirs. Dissolved oxygen (DO) in water column is essential for microorganisms and a significant indicator of the state of aquatic ecosystems. In this study, two artificial neural network (ANN) models including back propagation neural network (BPNN) and adaptive neural-based fuzzy inference system (ANFIS) approaches and multilinear regression (MLR) model were developed to estimate the DO concentration in the Feitsui Reservoir of northern Taiwan. The input variables of the neural network are determined as water temperature, pH, conductivity, turbidity, suspended solids, total hardness, total alkalinity, and ammonium nitrogen. The performance of the ANN models and MLR model was assessed through the mean absolute error, root mean square error, and correlation coefficient computed from the measured and model-simulated DO values. The results reveal that ANN estimation performances were superior to those of MLR. Comparing to the BPNN and ANFIS models through the performance criteria, the ANFIS model is better than the BPNN model for predicting the DO values. Study results show that the neural network particularly using ANFIS model is able to predict the DO concentrations with reasonable accuracy, suggesting that the neural network is a valuable tool for reservoir management in Taiwan.

  16. Nonlinear stochastic modeling of river dissolved-oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Tabios, G.Q. III.

    1984-01-01

    An important aspect of water quality modeling is forecasting water quality variables for real-time management and control applications to enhance, maintain and sustain desirable water qualities. The major objective of this research is to develop daily time series models for forecasting river dissolved-oxygen (DO). The modeling approach adopted herein combines deterministic and stochastic concepts for determining properties of the DO process based on time series data and dynamic mechanisms governing the said process. This is accomplished by deriving a general DO stochastic model structure based on a modified Streeter-Phelps DO-BOD dynamic model. Then some types of nonlinear models namely, self-exciting threshold autoregressive-moving average (SETARMA), amplitude-dependent autoregressive (ADAR) and bilinear (BL) models, and the class of linear autoregressive-moving average (ARMA) models are adopted for model identification and parameter estimation. Six stream-water quality gaging stations located in the eastern portion of the continental U.S.A. are utilized in this study. Various orders of ARMA, SETARMA, ADAR and BL models are fitted to the data. Results obtained indicated that ADAR and BL models are superior for one-step ahead forecasts, while SETARMA models are better for forecasts of longer lead times. In general, the SETARMA, ADAR and BL models show promise as alternative models for river DO time series modeling and forecasting with unique advantages in each.

  17. Using 18O as a Tracer of Oxygen in the Photochemical Alteration of Dissolved Organic Matter

    Science.gov (United States)

    Davis, J. A.; Stubbins, A.; Helms, J.; Dias, R. F.; Mopper, K.

    2006-12-01

    The biogeochemical cycling of dissolved organic matter (DOM) in natural waters is affected by numerous processes, including photochemical alteration. Photochemical processes result in the net oxidation and mineralization of DOM concomitant with dissolved oxygen consumption and production of dissolved inorganic carbon (DIC; principally CO2). The photochemical oxygen budget is not well constrained while DIC production accounts for nearly all the dissolved oxygen consumed, conflicting data suggests that more than half of the oxygen consumed is required to account for observed DOM oxidation and hydrogen peroxide production. An alternate source of oxygen is required to balance this budget; water itself may provide the answer. In order to determine the source of oxygen, a number of time series irradiations were performed using Great Dismal Swamp water (southeast Virginia) with 18O enrichments as either dissolved oxygen or water. Early results, upon irradiation in a UV solar simulator, show significant incorporation of 18O-enriched oxygen into high molecular weight (HMW) DOM from both sources. While the majority of the incorporated oxygen originated from the dissolved oxygen, at least 5 percent originated from water. Data will be presented showing the rate and degree of incorporation of 18O-enriched oxygen from both sources as well as the production of 18O-enriched carbon dioxide. The movement of 18O label will be discussed in relation to shifts in spectral qualities, including photobleaching and spectral slope, of the irradiated samples and selective incorporation as detailed by FT-ICRMS.

  18. Interannual variability of Dissolved Oxygen values around the Balearic Islands

    Science.gov (United States)

    Balbín, R.; Aparicio, A.; López-Jurado, J. L.; Flexas, M. M.

    2012-04-01

    Periodic movements of the trawl fishing fleet at Mallorca Island suggest a seasonal variability of the demersal resources, associated with hydrodynamic variability. The area where these commercial fisheries operate extends from the north to the southeast of Mallorca channel, between Mallorca and Ibiza Islands. It is thus affected by the different hydrodynamic conditions of the two sub-basins of the western Mediterranean (the Balearic and the Algerian sub-basins), with different geomorphologic and hydrodynamic characteristics. To characterize this hydrodynamic variability, hydrographic data collected around the Balearic Islands since 2001 with CTDs were analized [1]. Hydrographic parameters were processed according to the standard protocols. Dissolved oxygen (DO) was calibrated onboard using the winkler method. Temperature and salinity were used to characterize the different water masses. At the Western Mediterranean, the maximum values of DO in the water column are observed in the sur- face waters during winter (> 6.0 ml /l), when these water in contact with the atmosphere absorb large amount of oxygen, favored by low winter temperatures and notable turbulence. Later in the spring, the gradual increase of temperature, and the beginning of stratification and biological activity, lead to a decrease of oxygen concentration mainly in surface waters. During summer, these values continue to reduce in the surface mixed layer. Below it, and due to the biological activity, an increase is observed, giving rise to the absolute maximum of this parameter (> 6.5 ml /l). During autumn, the atmospheric forcing breaks the stratification producing a homogenization of surface water. At this moment, DO shows intermediate values. Below the surface waters, about 200 m, a relative maximum corresponding to the seasonal Winter Intermediate Waters (WIW) can be observed. Intermediate waters, between 400 and 600 m, reveal an oxygen minimum (4.0 ml /l) associated to the Levantine Intermediate

  19. Influence of dissolved oxygen on the protectiveness and morphological characteristics of calcareous deposits with galvanostatic polarization

    Science.gov (United States)

    Li, Chengjie; Du, Min; Gao, Rongjie

    2017-04-01

    The influence of dissolved oxygen on calcareous deposits formed under galvanostatic polarization mode was studied. When the dissolved oxygen concentration was less than 7 mg L-1, the cathodic protection potential showed a plateau at the initial polarization, and then quickly shifted negatively. While the dissolved oxygen was more than 9 mg L-1, the potential shifted negatively in a linear form. After 168 h of polarization, the final protection potential shifted negatively with the decreasing dissolved oxygen concentration. The deposition progress was monitored by electrochemical impedance spectroscopy, and only one single loop was found in Nyquist diagram, indicating deposits of ineffective protectiveness precipitation under the experimental conditions. The protection factor of deposits increased with the decreasing dissolved oxygen concentration which was detected by linear polarization resistance technique. The cathodic electrochemical reaction could change very shortly from oxygen reduction to hydrogen evolution after cathodic protection under very low dissolved oxygen concentration, such as 1 mg L-1, resulting in the hydrogen bubbling from the metallic surface and the decrease of deposits protection factor. Observation by scanning electron microscopy and X-ray diffraction analysis demonstrated that the deposits were mainly of calcite under the experimental conditions, and that dissolved oxygen had no effect on the crystalline types of calcium carbonate.

  20. Regulatory approaches for addressing dissolved oxygen concerns at hydropower facilities

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, Mark J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Cada, Glenn F. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Sale, Michael J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Eddlemon, Gerald K. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2003-03-01

    Low dissolved oxygen (DO) concentrations are a common water quality problem downstream of hydropower facilities. At some facilities, structural improvements (e.g. installation of weir dams or aerating turbines) or operational changes (e.g., spilling water over the dam) can be made to improve DO levels. In other cases, structural and operational approaches are too costly for the project to implement or are likely to be of limited effectiveness. Despite improvements in overall water quality below dams in recent years, many hydropower projects are unable to meet state water quality standards for DO. Regulatory agencies in the U.S. are considering or implementing dramatic changes in their approach to protecting the quality of the Nation’s waters. New policies and initiatives have emphasized flexibility, increased collaboration and shared responsibility among all parties, and market-based, economic incentives. The use of new regulatory approaches may now be a viable option for addressing the DO problem at some hydropower facilities. This report summarizes some of the regulatory-related options available to hydropower projects, including negotiation of site-specific water quality criteria, use of biological monitoring, watershed-based strategies for the management of water quality, and watershed-based trading. Key decision points center on the health of the local biological communities and whether there are contributing impacts (i.e., other sources of low DO effluents) in the watershed. If the biological communities downstream of the hydropower project are healthy, negotiation for site-specific water quality standards or biocriteria (discharge performance criteria based on characteristics of the aquatic biota) might be pursued. If there are other effluent dischargers in the watershed that contribute to low DO problems, watershed-scale strategies and effluent trading may be effective. This report examines the value of regulatory approaches by reviewing their use in

  1. Temporal Dynamics of Dissolved Oxygen Concentrations in the Hyporheic Zone.

    Science.gov (United States)

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

    2016-12-01

    Dissolved oxygen (DO) concentration profiles and DO consumption rates are primary indicators of the redox state of porewaters in the hyporheic zone (HZ). Previous studies (mostly numeric) of reactive solute transport, in the HZ, are steady state and give a fixed, in time, view of the biogeochemical activity and redox state of the HZ. Through the use of a novel, multichannel fiber optic DO measurement system and a robotic surface probe system in a large flume experiment, we have been able to track DO concentration, in the HZ, over time and at high spatial and temporal resolutions never achieved before. Our research shows that in carbon-limited systems (i.e., ones in which organic carbon replenishment is largely episodic), DO concentration profiles and consumption rates will vary as a function of time. As the most readily available organic carbon is consumed, (first near the bed surface/water interface) respiration rates, in that area, will drop and DO will be transported deeper into the HZ. Over time, and lacking either an external source of bioavailable carbon or an alternate electron donor substrate, microbial metabolic activity will slow substantially and the majority of the HZ will be rendered oxic. Hyporheic fluxes affect the time scale of biological reactions resulting in faster growth of the aerobic zone in high-flux systems. While this temporal variability can result in a multitude of DO consumption curves (DO vs. residence time), the careful application of dimensional analysis can collapse the consumption curves to a single characteristic curve that accounts for a wide range of morphology and reactivity.

  2. A highly accurate method for determination of dissolved oxygen: Gravimetric Winkler method

    Energy Technology Data Exchange (ETDEWEB)

    Helm, Irja; Jalukse, Lauri [University of Tartu, Institute of Chemistry, 14a Ravila str., 50411 Tartu (Estonia); Leito, Ivo, E-mail: ivo.leito@ut.ee [University of Tartu, Institute of Chemistry, 14a Ravila str., 50411 Tartu (Estonia)

    2012-09-05

    Highlights: Black-Right-Pointing-Pointer Probably the most accurate method available for dissolved oxygen concentration measurement was developed. Black-Right-Pointing-Pointer Careful analysis of uncertainty sources was carried out and the method was optimized for minimizing all uncertainty sources as far as practical. Black-Right-Pointing-Pointer This development enables more accurate calibration of dissolved oxygen sensors for routine analysis than has been possible before. - Abstract: A high-accuracy Winkler titration method has been developed for determination of dissolved oxygen concentration. Careful analysis of uncertainty sources relevant to the Winkler method was carried out and the method was optimized for minimizing all uncertainty sources as far as practical. The most important improvements were: gravimetric measurement of all solutions, pre-titration to minimize the effect of iodine volatilization, accurate amperometric end point detection and careful accounting for dissolved oxygen in the reagents. As a result, the developed method is possibly the most accurate method of determination of dissolved oxygen available. Depending on measurement conditions and on the dissolved oxygen concentration the combined standard uncertainties of the method are in the range of 0.012-0.018 mg dm{sup -3} corresponding to the k = 2 expanded uncertainty in the range of 0.023-0.035 mg dm{sup -3} (0.27-0.38%, relative). This development enables more accurate calibration of electrochemical and optical dissolved oxygen sensors for routine analysis than has been possible before.

  3. Freshwater Macroinvertebrates.

    Science.gov (United States)

    Nalepa, T. F.

    1978-01-01

    Presents a literature review of freshwater biology particularly freshwater macroinvertebrates and their effect on water pollution, covering publications of 1976-77. A list of 158 references is also presented. (HM)

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

    Science.gov (United States)

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

    1990-01-01

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

  5. Use of a novel acoustic dissolved oxygen transmitter for fish telemetry

    DEFF Research Database (Denmark)

    Svendsen, Jon Christian; Aarestrup, Kim; Steffensen, J.F.

    2006-01-01

    The multiple responses of fishes to changes in dissolved oxygen saturations have been studied widely in the laboratory. In contrast only few studies have included field observations. The objective of the present study was to evaluate the performance of a novel acoustic dissolved oxygen transmitter...... for field biotelemetry. The results demonstrated that the output of the transmitter was unaffected by three different temperatures (10 to 30 degrees C) and described the dissolved oxygen saturation with high accuracy (r(2) > 0.99) over the entire range of 0 to 191% saturation. The response time (>= 90......% of end value) of the transmitter was 12 s both in terms of decreasing (100 to 0%) and increasing (0 to 100%) oxygen saturations. When externally attached to fishes the present findings support the use of the transmitter for reliable dissolved oxygen measurements on individuals living in environments...

  6. Variations of dissolved oxygen in Mandovi and Zuari estuaries

    Digital Repository Service at National Institute of Oceanography (India)

    DeSousa, S.N.; SenGupta, R.

    and bottom water very low concentration. The stations at the freshwater end showed relatively higher oxygen concentration than the stations at the sea-end. Plots of oxygen against salinity showed peaks at the extreme ends (freshwater and seawater). Another...

  7. Bottom Dissolved Oxygen Maps From SEAMAP Summer Groundfish/Shrimp Surveys

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Bottom dissolved oxygen (DO) data was extracted from environmental profiles acquired during the Southeast Fisheries Science Center Mississippi Laboratories summer...

  8. Predictive Control of Dissolved Oxygen Concentration in Cynoglossus Semilaevis Industrial Aquaculture

    National Research Council Canada - National Science Library

    Hongjing Liu; Yaoguang Wei; Chunhong Liu; Yingyi Chen

    2014-01-01

    .... The changing process of dissolved oxygen concentration contains nonlinearities and big time-delay because it is restricted by multiple factors, so traditional control methods are difficult to control...

  9. Changes in nutrient, dissolved oxygen and total suspended matter during simulated placer mining

    Digital Repository Service at National Institute of Oceanography (India)

    Sijinkumar, A.V.; Naik, T.; Nath, B.N.; Sharma, R.

    characteristics such as Total Suspended Matter (TSM), Dissolved Oxygen (DO) and nutrients (phosphate, nitrite, nitrate and silicate) were studied in different stages of the experiment (pre mining, during mining, post mining) in view of their essential nature...

  10. Linear Active Disturbance Rejection Control of Dissolved Oxygen Concentration Based on Benchmark Simulation Model Number 1

    Directory of Open Access Journals (Sweden)

    Xiaoyi Wang

    2015-01-01

    Full Text Available In wastewater treatment plants (WWTPs, the dissolved oxygen is the key variable to be controlled in bioreactors. In this paper, linear active disturbance rejection control (LADRC is utilized to track the dissolved oxygen concentration based on benchmark simulation model number 1 (BSM1. Optimal LADRC parameters tuning approach for wastewater treatment processes is obtained by analyzing and simulations on BSM1. Moreover, by analyzing the estimation capacity of linear extended state observer (LESO in the control of dissolved oxygen, the parameter range of LESO is acquired, which is a valuable guidance for parameter tuning in simulation and even in practice. The simulation results show that LADRC can overcome the disturbance existing in the control of wastewater and improve the tracking accuracy of dissolved oxygen. LADRC provides another practical solution to the control of WWTPs.

  11. Gulf of Mexico Hypoxia Watch Bottom Dissolved Oxygen Contours for SEAMAP Cruises of 2001 - 2016

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Hypoxia Watch project provides near-real-time, web-based maps of dissolved oxygen near the sea floor over the Texas-Louisiana-Florida continental shelf...

  12. Effects of dissolved oxygen on electrochemical and semiconductor properties of 316L stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Feng Zhicao [Corrosion and Protection Center, University of Science and Technology Beijing, Beijing 100083 (China); Cheng Xuequn, E-mail: chxq2000@hotmail.co [Corrosion and Protection Center, University of Science and Technology Beijing, Beijing 100083 (China); Dong Chaofang; Xu Lin [Corrosion and Protection Center, University of Science and Technology Beijing, Beijing 100083 (China); Li Xiaogang, E-mail: lixiaogang99@263.ne [Corrosion and Protection Center, University of Science and Technology Beijing, Beijing 100083 (China)

    2010-12-31

    The effects of dissolved oxygen on the electrochemical behavior and semiconductor properties of passive film formed on 316L SS in three solutions with different dissolved oxygen were studied by using polarization curve, Mott-Schottky analysis and the point defect model (PDM). The results show that higher dissolved oxygen accelerates both anodic and cathodic process. Based on Mott-Schottky analysis and PDM, the key parameters for passive film, donor density N{sub d}, flat-band potential E{sub fb} and diffusivity of defects D{sub 0} were calculated. The results display that N{sub d}(1-7 x 10{sup 27}m{sup -3}) and D{sub 0}(1-18 x 10{sup -16}cm{sup 2}/s) increase and E{sub fb} value reduces with the dissolved oxygen in solution.

  13. Field comparison of optical and clark cell dissolved-oxygen sensors

    Science.gov (United States)

    Fulford, J.M.; Davies, W.J.; Garcia, L.

    2005-01-01

    Three multi-parameter water-quality monitors equipped with either Clark cell type or optical type dissolved-oxygen sensors were deployed for 30 days in a brackish (salinity biofouling. The dissolved-oxygen sensors compared periodically to a hand-held dissolved oxygen sensor, but were not serviced or cleaned during the deployment. One of the Clark cell sensors and the optical sensor performed similarly during the deployment. The remaining Clark cell sensor was not aged correctly prior to deployment and did not perform as well as the other sensors. All sensors experienced substantial biofouling that gradually degraded the accuracy of the dissolved-oxygen measurement during the last half of the deployment period. Copyright ASCE 2005.

  14. Supplement and Consumption of Dissolved Oxygen and Their Seasonal Variations in Shrimp Pond

    Institute of Scientific and Technical Information of China (English)

    孙耀; 张淑芳; 陈聚法; 宋云利

    2001-01-01

    On the basis of the research of DO budget or kinetics in shrimp pond, the main influence process of DO and its seasonal variations are quantitatively described through redividing the budget process and modifying the quantitative method of the process. The percentages of oxygen demand of various processes in the total oxygen demand are different in shrimp cultivation seasons. It is showed that the dissolved oxygen demand of mini-organisms is the major affected factor of DO in this environment and approximately accounts for 64.1~74.1% of the total oxygen demand. In the early period of shrimp culture, the dissolved oxygen demand of allotrophic bacteria degrading organic matters is much lower than that of phytoplankton respiration. But in the midterrn and later period, it is about 50% of the total oxygen demand because of the higher water temperature and more serious self-pollution. The dissolved oxygen demand of sediment is lower and just 19.1~28.8%, while the percentage of shrimp oxygen demand is lower. The effect of phytoplankton on DO in shrimp culturing water has dualism. One is the oxygen producing process of photosynthesis and the other is the oxygen consumption process of respiration. It is estimated that the dissolved oxygen demand of phytoplankton respiration is approximately one-fifth of the oxygen produced by photosynthesis under normal illumination conditions. The dissolved oxygen demand of al lotrophic bacteria degrading organic matters and the total oxygen demand of sediment increase 4 times and 1.7 times respectively from the early period to the midterm and later period.Obviously, the DO of culturing water can be also greatly improved by controlling the selfpollution of organic matters during shrimp culture.

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

    Science.gov (United States)

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

  16. Techniques for the conversion to carbon dioxide of oxygen from dissolved sulfate in thermal waters

    Science.gov (United States)

    Nehring, N.L.; Bowen, P.A.; Truesdell, A.H.

    1977-01-01

    The fractionation of oxygen isotopes between dissolved sulfate ions and water provides a useful geothermometer for geothermal waters. The oxygen isotope composition of dissolved sulfate may also be used to indicate the source of the sulfate and processes of formation. The methods described here for separation, purification and reduction of sulfate to prepare carbon dioxide for mass spectrometric analysis are modifications of methods by Rafter (1967), Mizutani (1971), Sakai and Krouse (1971), and Mizutani and Rafter (1969). ?? 1976.

  17. Relationships between secchi disk visibility, water temperature and dissolved oxygen in freshwater fishpond

    OpenAIRE

    M. H. Ali; Cagauan, A.G.

    2007-01-01

    A study was conducted to determine the relationships between secchi disk variability, water temperature and dissolved oxygen in fish ponds. Multiple regression correlation analysis was done to evaluate the relationships between the variables. Results indicated that the ranges of secchi disk visibility, water temperature and dissolved oxygen in the study ponds were just within the ranges of the variables for tilapia culture. Multiple regression correlation showed no (or insignificant) relation...

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

    Science.gov (United States)

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

    2014-12-01

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

  19. An Optical Oxygen Sensor for Long-Term Continuous Monitoring of Dissolved Oxygen in Perfused Bioreactors

    Science.gov (United States)

    Gao, F. G.; Jeevarajan, A. S.; Anderson, M. M.

    2002-01-01

    For long-term growth of man1ITlalian cells in perfused bioreactors, it is essential to monitor the concentration of dissolved oxygen (DO) present in the culture medium to quantitate and control level of DO. Continuous measurement of the amount of DO in the cell culture medium in-line under sterile conditions in NASA's perfused bioreactor requires that the oxygen sensor provide increased sensitivity and be sterilizable and nontoxic. Additionally, long-term cell culture experiments require that the calibration be maintained several weeks or months. Although there are a number of sensors for dissolved oxygen on the market and under development elsewhere, very few meet these stringent conditions. An optical oxygen sensor (BOXY) based on dynamic fluorescent quenching and a pulsed blue LED light source was developed in our laboratory to address these requirements. Tris( 4,7 -diphenyl-l, 1 O-phenanthroline )ruthenium(II) chloride is employed as the fluorescent dye indicator. The sensing element consists of a glass capillary (OD 4.0 mm; ID 2.0 mm) coated internally with a thin layer of the fluorescent dye in silicone matrix and overlayed with a black shielding layer. Irradiation of the sensing element with blue light (blue LED with emission maximum at 475 nm) generates a red fluorescence centered at 626 nm. The fluorescence intensity is correlated to the concentration of DO present in the culture medium, following the modified non-linear Stern-Volmer equation. By using a pulsed irradiating light source, the problem of dye-bleaching, which is often encountered in long-term continuous measurements of tIns type, 'is minimized. To date we achieved sensor resolution of 0.3 mmHg at 50 mmHg p02, and 0.6 mmHg at 100 mmHg p02, with a response time of about one minute. Calibration was accomplished in sterile phosphate-buffered saline with a blood-gas analyzer (BGA) measurement as reference. Stand-alone software was also developed to control the sensor and bioreactor as well as to

  20. A New Optical Oxygen Sensor Reveals Spatial and Temporal Variations of Dissolved Oxygen at Ecohydrological Interfaces

    Science.gov (United States)

    Brandt, T.; Schmidt, C.; Fleckenstein, J. H.; Vieweg, M.; Harjung, A.

    2015-12-01

    The spatial and temporal distribution of dissolved oxygen (DO) at highly reactive aquatic interfaces, e.g. in the hyporheic zone (HZ), is a primary indicator of redox and interlinked biogeochemical zonations. However, continuous measuring of DO over time and depths is challenging due to the dynamic and potentially heterogenic nature of the HZ. We further developed a novel technology for spatially continuous in situ vertical oxygen profiling based on optical sensing (Vieweg et al, 2013). Continuous vertical measurements to a depth of 50 cm are obtained by the motor-controlled insertion of a side-firing Polymer Optical Fiber (POF) into tubular DO probes. Our technology allows minimally invasive DO measurements without DO consumption at high spatial resolution in the mm range. The reduced size of the tubular probe (diameter 5 mm) substantially minimizes disturbance of flow conditions. We tested our technology in situ in the HZ of an intermittent stream during the drying period. Repeated DO measurements were taken over a total duration of six weeks at two locations up- and downstream of a pool-cascade sequence. We were able to precisely map the spatial DO distribution which exhibited sharp gradients and rapid temporal changes as a function of changing hydrologic conditions. Our new vertical oxygen sensing technology will help to provide new insights to the coupling of transport of DO and biogeochemical reactions at aquatic interfaces. Vieweg, M., Trauth, N., Fleckenstein, J. H., Schmidt, C. (2013): Robust Optode-Based Method for Measuring in Situ Oxygen Profiles in Gravelly Streambeds. Environmental Science & Technology. doi:10.1021/es401040w

  1. THE INFLUENCE OF PONDS ON DISSOLVED OXYGEN IN SMALL RIVERS OF BERRY (FRANCE

    Directory of Open Access Journals (Sweden)

    Abdelhamid AZAROUAL

    2012-03-01

    Full Text Available The influence of ponds on dissolved oxygen in small rivers of Berry (France. Water temperature and oxygen saturation are two major indicators of water quality in surface hydrology. Geographical and cartographic studies about ponds of Central France did no exist until now. During two years, we measured dissolved oxygen using a hand oximeter upstream and downstream of three ponds in the headwaters of the Loire basin. Our results show that oxygen saturation depends on equipments located before and behind the dam, and upstream and downstream: spillways, outlets with a monk, diversion channel, artificial reoxygenation weirs and so on. In some cases (low water quality upstream, existence of weir, relative and absolute saturation of dissolved oxygen increases downstream of ponds.

  2. Dissolved oxygen and water temperature dynamics in lowland rivers over various timescales

    Directory of Open Access Journals (Sweden)

    Rajwa-Kuligiewicz Agnieszka

    2015-12-01

    Full Text Available The impact of floodplain hydrology on the in-stream dissolved oxygen dynamics and the relation between dissolved oxygen and water temperature are investigated. This has been done by examining the time series of dissolved oxygen and water temperature coupled with meteorological and hydrological data obtained from two lowland rivers having contrasting hydrological settings. Spectral analysis of long-term oxygen variations in a vegetated river revealed a distinct scaling regime with slope ‘–1’ indicating a self-similar behaviour. Identical slopes were obtained for water temperature and water level. The same power-law behaviour was observed for an unvegetated river at small timescales revealing the underlying scaling behaviour of dissolved oxygen regime for different types of rivers and over various time scales. The results have shown that the oxygenation of a vegetated river is strongly related to its thermal regime and flow conditions. Moreover, analysis of short-term fluctuations in the unvegetated river demonstrated that physical factors such as rainfall and backwaters play a substantial role in the functioning of this ecosystem. Finally, the results show that the relation between water temperature and dissolved oxygen concentration at the diurnal timescale exhibits a looping behaviour on the variable plot. The findings of this study provide an insight into the sensitivity of rivers to changing hydro-physical conditions and can be useful in the assessment of environmental variability.

  3. Remote Sensing of Dissolved Oxygen and Nitrogen in Water using Raman Spectroscopy

    Science.gov (United States)

    De Young, R.; Ganoe, R.

    2013-12-01

    The health of an estuarine ecosystem is largely driven by the abundance of dissolved oxygen and nitrogen available for maintenance of plant and animal life. An investigation was conducted to quantify the concentration of dissolved molecular oxygen and nitrogen in water by means of Raman spectroscopy. This technique is proposed for the remote sensing of dissolved oxygen in the Chesapeake Bay, which will be utilized by aircraft in order to survey large areas in real-time. A proof of principle experiment has demonstrated the ability to remotely detect dissolved oxygen and nitrogen in pure water (also Chesapeake Bay water) using a 355nm Nd:YAG laser and a simple monochromater to detect the shifted Raman oxygen and nitrogen backscattered signals at 376.2 and 387.5 nm respectively. The theoretical basis for the research, components of the experimental system, and key findings are presented. A 1.3-m water cell had an attached vertical column to house a Troll 9500 dissolved oxygen in-situ monitor (In-Situ Inc Troll 9500). The Raman oxygen signal could be calibrated with this devise. While Raman backscattered water signals are low a potential aircraft remote system was designed and will be presented.

  4. Effects of Environmental Oxygen Content and Dissolved Oxygen on the Surface Tension and Viscosity of Liquid Nickel

    Science.gov (United States)

    SanSoucie, M. P.; Rogers, J. R.; Kumar, V.; Rodriguez, J.; Xiao, X.; Matson, D. M.

    2016-07-01

    The NASA Marshall Space Flight Center's electrostatic levitation (ESL) laboratory has recently added an oxygen partial pressure controller. This system allows the oxygen partial pressure within the vacuum chamber to be measured and controlled in the range from approximately 10^{-28} {to} 10^{-9} bar, while in a vacuum atmosphere. The oxygen control system installed in the ESL laboratory's main chamber consists of an oxygen sensor, oxygen pump, and a control unit. The sensor is a potentiometric device that determines the difference in oxygen activity in two gas compartments (inside the chamber and the air outside of the chamber) separated by an electrolyte. The pump utilizes coulometric titration to either add or remove oxygen. The system is controlled by a desktop control unit, which can also be accessed via a computer. The controller performs temperature control for the sensor and pump, has a PID-based current loop and a control algorithm. Oxygen partial pressure has been shown to play a significant role in the surface tension of liquid metals. Oxide films or dissolved oxygen may lead to significant changes in surface tension. The effects on surface tension and viscosity by oxygen partial pressure in the surrounding environment and the melt dissolved oxygen content will be evaluated, and the results will be presented. The surface tension and viscosity will be measured at several different oxygen partial pressures while the sample is undercooled. Surface tension and viscosity will be measured using the oscillating droplet method.

  5. Microfluidic dissolved oxygen gradient generator biochip as a useful tool in bacterial biofilm studies

    DEFF Research Database (Denmark)

    Skolimowski, Maciej; Weiss Nielsen, Martin; Emnéus, Jenny

    2010-01-01

    A microfluidic chip for generation of gradients of dissolved oxygen was designed, fabricated and tested. The novel way of active oxygen depletion through a gas permeable membrane was applied. Numerical simulations for generation of O-2 gradients were correlated with measured oxygen concentrations....... The developed microsystem was used to study growth patterns of the bacterium Pseudomonas aeruginosa in medium with different oxygen concentrations. The results showed that attachment of Pseudomonas aeruginosa to the substrate changed with oxygen concentration. This demonstrates that the device can be used...... for studies requiring controlled oxygen levels and for future studies of microaerobic and anaerobic conditions....

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

    Science.gov (United States)

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

  7. The river Mesta case study: A qualitative model of dissolved oxygen in aquatic ecosystems

    NARCIS (Netherlands)

    Nakova, E.; Linnebank, F.E.; Bredeweg, B.; Salles, P.; Uzunov, Y.

    2009-01-01

    The dynamics of the dissolved oxygen in water bodies is the result of complex interactions involving physical and biological processes. Understanding how the balance of these influences determines the amount of oxygen available for living organisms is a key factor to interpret the water body

  8. Water-immiscible dissolved oxygen carriers in combination with ...

    African Journals Online (AJOL)

    STORAGESEVER

    2010-02-22

    Feb 22, 2010 ... 2Department of Chemical Engineering, Faculty of Engineering, Cape Peninsula University of Technology, ... As oxygen has a low solubility in aqueous medium, DO ..... A dynamic light ... a model perfluorocarbon emulsion.

  9. Quantifying consumption rates of dissolved oxygen along bed forms

    Science.gov (United States)

    Boano, Fulvio; De Falco, Natalie; Arnon, Shai

    2016-04-01

    Streambed interfaces represent hotspots for nutrient transformations because they host different microbial species, and the evaluation of these reaction rates is important to assess the fate of nutrients in riverine environments. In this work we analyze a series of flume experiments on oxygen demand in dune-shaped hyporheic sediments under losing and gaining flow conditions. We employ a new modeling code to quantify oxygen consumption rates from observed vertical profiles of oxygen concentration. The code accounts for transport by molecular diffusion and water advection, and automatically determines the reaction rates that provide the best fit between observed and modeled concentration values. The results show that reaction rates are not uniformly distributed across the streambed, in agreement with the expected behavior predicted by hyporheic exchange theory. Oxygen consumption was found to be highly influenced by the presence of gaining or losing flow conditions, which controlled the delivery of labile DOC to streambed microorganisms.

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

    Science.gov (United States)

    Dmitrieva, E V

    2015-01-01

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

  11. A highly accurate method for determination of dissolved oxygen: gravimetric Winkler method.

    Science.gov (United States)

    Helm, Irja; Jalukse, Lauri; Leito, Ivo

    2012-09-05

    A high-accuracy Winkler titration method has been developed for determination of dissolved oxygen concentration. Careful analysis of uncertainty sources relevant to the Winkler method was carried out and the method was optimized for minimizing all uncertainty sources as far as practical. The most important improvements were: gravimetric measurement of all solutions, pre-titration to minimize the effect of iodine volatilization, accurate amperometric end point detection and careful accounting for dissolved oxygen in the reagents. As a result, the developed method is possibly the most accurate method of determination of dissolved oxygen available. Depending on measurement conditions and on the dissolved oxygen concentration the combined standard uncertainties of the method are in the range of 0.012-0.018 mg dm(-3) corresponding to the k=2 expanded uncertainty in the range of 0.023-0.035 mg dm(-3) (0.27-0.38%, relative). This development enables more accurate calibration of electrochemical and optical dissolved oxygen sensors for routine analysis than has been possible before.

  12. Dissolved oxygen content prediction in crab culture using a hybrid intelligent method

    Science.gov (United States)

    Yu, Huihui; Chen, Yingyi; Hassan, Shahbazgul; Li, Daoliang

    2016-06-01

    A precise predictive model is needed to obtain a clear understanding of the changing dissolved oxygen content in outdoor crab ponds, to assess how to reduce risk and to optimize water quality management. The uncertainties in the data from multiple sensors are a significant factor when building a dissolved oxygen content prediction model. To increase prediction accuracy, a new hybrid dissolved oxygen content forecasting model based on the radial basis function neural networks (RBFNN) data fusion method and a least squares support vector machine (LSSVM) with an optimal improved particle swarm optimization(IPSO) is developed. In the modelling process, the RBFNN data fusion method is used to improve information accuracy and provide more trustworthy training samples for the IPSO-LSSVM prediction model. The LSSVM is a powerful tool for achieving nonlinear dissolved oxygen content forecasting. In addition, an improved particle swarm optimization algorithm is developed to determine the optimal parameters for the LSSVM with high accuracy and generalizability. In this study, the comparison of the prediction results of different traditional models validates the effectiveness and accuracy of the proposed hybrid RBFNN-IPSO-LSSVM model for dissolved oxygen content prediction in outdoor crab ponds.

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

    Science.gov (United States)

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

    2014-12-01

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

  14. Macroinvertebrate assemblages in agricultural, mining, and urban tropical streams: implications for conservation and management.

    Science.gov (United States)

    Mwedzi, Tongayi; Bere, Taurai; Mangadze, Tinotenda

    2016-06-01

    The study evaluated the response of macroinvertebrate assemblages to changes in water quality in different land-use settings in Manyame catchment, Zimbabwe. Four land-use categories were identified: forested commercial farming, communal farming, Great Dyke mining (GDM) and urban areas. Macroinvertebrate community structure and physicochemical variables data were collected in two seasons from 41 sites following standard methods. Although not environmentally threatening, urban and GDM areas were characterised by higher conductivity, total dissolved solids, salinity, magnesium and hardness. Chlorides, total phosphates, total nitrogen, calcium, potassium and sodium were significantly highest in urban sites whilst dissolved oxygen (DO) was significantly higher in the forested commercial faming and GDM sites. Macroinvertebrate communities followed the observed changes in water quality. Macroinvertebrates in urban sites indicated severe pollution (e.g. Chironomidae) whilst those in forested commercial farming sites and GDM sites indicated relatively clean water (e.g. Notonemouridae). Forested watersheds together with good farm management practices are important in mitigating impacts of urbanisation and agriculture. Strategies that reduce oxygen-depleting substances must be devised to protect the health of Zimbabwean streams. The study affirms the wider applicability of the South African Scoring System in different land uses.

  15. Modelling nitrogen and phosphorus cycles and dissolved oxygen in the Zhujiang Estuary Ⅰ. Model development

    Institute of Scientific and Technical Information of China (English)

    Guan Weibing; Wong Lai-Ah; Xu Dongfeng

    2001-01-01

    An ecosystem-based water quality model was designed to estimate the biochemical reaction of nutrient and dissolved oxygen in conjunction with a three-dimensional hydrodynamic and sediment model. As both phosphorus and nitrogen successively limit phytoplankton growth in many estuaries, the model simulates both these nutrient cycles each using five variables, namely, dissolved inorganic nutrient, detritic organic matter, benthic matter, phytoplankton and zooplankton.

  16. Simulation of Temperature, Nutrients, Biochemical Oxygen Demand, and Dissolved Oxygen in the Catawba River, South Carolina, 1996-97

    Science.gov (United States)

    Feaster, Toby D.; Conrads, Paul A.; Guimaraes, Wladmir B.; Sanders, Curtis L.; Bales, Jerad D.

    2003-01-01

    Time-series plots of dissolved-oxygen concentrations were determined for various simulated hydrologic and point-source loading conditions along a free-flowing section of the Catawba River from Lake Wylie Dam to the headwaters of Fishing Creek Reservoir in South Carolina. The U.S. Geological Survey one-dimensional dynamic-flow model, BRANCH, was used to simulate hydrodynamic data for the Branched Lagrangian Transport Model. Waterquality data were used to calibrate the Branched Lagrangian Transport Model and included concentrations of nutrients, chlorophyll a, and biochemical oxygen demand in water samples collected during two synoptic sampling surveys at 10 sites along the main stem of the Catawba River and at 3 tributaries; and continuous water temperature and dissolved-oxygen concentrations measured at 5 locations along the main stem of the Catawba River. A sensitivity analysis of the simulated dissolved-oxygen concentrations to model coefficients and data inputs indicated that the simulated dissolved-oxygen concentrations were most sensitive to watertemperature boundary data due to the effect of temperature on reaction kinetics and the solubility of dissolved oxygen. Of the model coefficients, the simulated dissolved-oxygen concentration was most sensitive to the biological oxidation rate of nitrite to nitrate. To demonstrate the utility of the Branched Lagrangian Transport Model for the Catawba River, the model was used to simulate several water-quality scenarios to evaluate the effect on the 24-hour mean dissolved-oxygen concentrations at selected sites for August 24, 1996, as simulated during the model calibration period of August 23 27, 1996. The first scenario included three loading conditions of the major effluent discharges along the main stem of the Catawba River (1) current load (as sampled in August 1996); (2) no load (all point-source loads were removed from the main stem of the Catawba River; loads from the main tributaries were not removed); and (3

  17. Remote Sensing of Dissolved Oxygen and Nitrogen in Water Using Raman Spectroscopy

    Science.gov (United States)

    Ganoe, Rene; DeYoung, Russell J.

    2013-01-01

    The health of an estuarine ecosystem is largely driven by the abundance of dissolved oxygen and nitrogen available for maintenance of plant and animal life. An investigation was conducted to quantify the concentration of dissolved molecular oxygen and nitrogen in water by means of Raman spectroscopy. This technique is proposed for the remote sensing of dissolved oxygen in the Chesapeake Bay, which will be utilized by aircraft in order to survey large areas in real-time. A proof of principle system has been developed and the specifications are being honed to maximize efficiency for the final application. The theoretical criteria of the research, components of the experimental system, and key findings are presented in this report

  18. Measuring Flow Rate in Crystalline Bedrock Wells Using the Dissolved Oxygen Alteration Method.

    Science.gov (United States)

    Vitale, Sarah A; Robbins, Gary A

    2017-03-22

    Determination of vertical flow rates in a fractured bedrock well can aid in planning and implementing hydraulic tests, water quality sampling, and improving interpretations of water quality data. Although flowmeters are highly accurate in flow rate measurement, the high cost and logistics may be limiting. In this study the dissolved oxygen alteration method (DOAM) is expanded upon as a low-cost alternative to determine vertical flow rates in crystalline bedrock wells. The method entails altering the dissolved oxygen content in the wellbore through bubbler aeration, and monitoring the vertical advective movement of the dissolved oxygen over time. Measurements were taken for upward and downward flows, and under ambient and pumping conditions. Vertical flow rates from 0.06 to 2.30 Lpm were measured. To validate the method, flow rates determined with the DOAM were compared to pump discharge rates and found to be in agreement within 2.5%.

  19. Reaction of erythromycin with dissolved oxygen on gold nanoparticle-modified glassy carbon electrodes

    Institute of Scientific and Technical Information of China (English)

    LI Xue; FU Ying; WANG Jian-xiu; L(U) Hui-dan; XU Mao-tian

    2008-01-01

    Cyclic voltammetry was used to investigate the reaction of erythromycin (EM) with dissolved oxygen on gold nanoparticle-modified electrodes prepared via electrodeposition. A well-defined reduction peak at -0.420 V and a reoxidation peak at -0.055V were observed. With the addition of EM into the NaOH solution containing dissolved oxygen, the oxidation peak at -0.055 V was still indiscernible. However, a new oxidation peak at 0.200V appeared, which suggests the interaction between EM and dissolved oxygen. Therefore, this method can be used for the analysis of EM in tablets. The present method is simple, reproducible,and does not require complex analytical instruments.

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

    Science.gov (United States)

    Kita, Yoshito; Nishikawa, Hiroshi; Takemoto, Tadashi

    2006-07-25

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

  1. Effects of Dissolved Oxygen on Nitrogen Release from Jialu River Sediment

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    [Objective] The aim was to study the effects of dissolved oxygen(DO) on nitrogen release from Jialu River sediment.[Method] Based on the present pollution of Jialu River(in Zhengzhou),the effects of dissolved oxygen on nitrogen transformation in Jialu River sediment were analyzed through simulation test of original columnar sediment.[Result] DO was the main impact factor of nitrogen transformation in Jialu River sediment,and DO with different concentrations had various effects on the transformation time and...

  2. A dissolved cobalt plume in the oxygen minimum zone of the eastern tropical South Pacific

    Science.gov (United States)

    Hawco, Nicholas J.; Ohnemus, Daniel C.; Resing, Joseph A.; Twining, Benjamin S.; Saito, Mak A.

    2016-10-01

    Cobalt is a nutrient to phytoplankton, but knowledge about its biogeochemical cycling is limited, especially in the Pacific Ocean. Here, we report sections of dissolved cobalt and labile dissolved cobalt from the US GEOTRACES GP16 transect in the South Pacific. The cobalt distribution is closely tied to the extent and intensity of the oxygen minimum zone in the eastern South Pacific with highest concentrations measured at the oxycline near the Peru margin. Below 200 m, remineralization and circulation produce an inverse relationship between cobalt and dissolved oxygen that extends throughout the basin. Within the oxygen minimum zone, elevated concentrations of labile cobalt are generated by input from coastal sources and reduced scavenging at low O2. As these high cobalt waters are upwelled and advected offshore, phytoplankton export returns cobalt to low-oxygen water masses underneath. West of the Peru upwelling region, dissolved cobalt is less than 10 pM in the euphotic zone and strongly bound by organic ligands. Because the cobalt nutricline within the South Pacific gyre is deeper than in oligotrophic regions in the North and South Atlantic, cobalt involved in sustaining phytoplankton productivity in the gyre is heavily recycled and ultimately arrives from lateral transport of upwelled waters from the eastern margin. In contrast to large coastal inputs, atmospheric deposition and hydrothermal vents along the East Pacific Rise appear to be minor sources of cobalt. Overall, these results demonstrate that oxygen biogeochemistry exerts a strong influence on cobalt cycling.

  3. Effect of dissolved oxygen in alcoholic beverages and drinking water on alcohol elimination in humans.

    Science.gov (United States)

    Rhee, Su-jin; Chae, Jung-woo; Song, Byung-jeong; Lee, Eun-sil; Kwon, Kwang-il

    2013-02-01

    Oxygen plays an important role in the metabolism of alcohol. An increased dissolved oxygen level in alcoholic beverages reportedly accelerates the elimination of alcohol. Therefore, we evaluated the effect of dissolved oxygen in alcohol and the supportive effect of oxygenated water on alcohol pharmacokinetics after the excessive consumption of alcohol, i.e., 540 ml of 19.5% alcohol (v/v). Fifteen healthy males were included in this randomized, 3 × 3 crossover study. Three combinations were tested: X, normal alcoholic beverage and normal water; Y, oxygenated alcoholic beverage and normal water; Z, oxygenated alcoholic beverage and oxygenated water. Blood alcohol concentrations (BACs) were determined by conversion of breath alcohol concentrations. Four pharmacokinetic parameters (C(max), T(max), K(el), and AUCall) were obtained using non-compartmental analysis and the times to reach 0.05% and 0.03% BAC (T(0.05%) and T(0.03%)) were compared using one-way analysis of variance (ANOVA) and Duncan's post hoc test. With combination Z, the BAC decreased to 0.05% significantly faster (p water augments the effect of oxygen in the alcoholic beverage in alcohol elimination. Therefore, it is necessary to investigate the supportive effect of ingesting additional oxygenated water after heavy drinking of normal alcoholic beverages.

  4. A novel isotopic fractionation during dissolved oxygen consumption in mesopelagic waters inferred from observation and model simulation of dissolved oxygen δ18O in open oceanic regions

    Science.gov (United States)

    Nakayama, N.; Oka, A.; Gamo, T.

    2012-12-01

    Oxygen isotopic ratio (δ18O) of dissolved oxygen is a useful for bioactive tracer of the subsurface aphotic (mesopelagic) ocean since it varies nonlinearly related to oxygen consumption via stoichiometry of organic matter decomposition. Therefore, along with global circulation model (GCM), observed δ18O and their vertical/geographical distribution can be effectively used to quantitatively determine how marine biological and ocean physical processes contribute to varying dissolved oxygen (DO) concentration in the ocean, in particular mesopelagic zone where pronounced biological activity alters DO concentration significantly. In the central north Pacific Ocean and Indian Ocean, including Arabian Sea, one of the few regions in the open ocean which has oxygen minimum zone (OMZ, a layer with severely depleted DO), vertical profiles of DO and δ18O were observed. These observed data are compared with a GCM simulation in which a constant isotopic fractionation factor of DO by marine biological respiration and a fixed Redfield molar ratio between P and O are assumed. Even in the Arabian Sea OMZ, relationship between DO and δ18O was found to be similar to those observed in other open oceans, indicating that no specific oxygen consumption process occurred in the OMZ. Using the GCM model, we attempted to reproduce the observed overall relationship between DO and δ18O, but it failed when we adopted the previously reported isotopic fractionation factor: Discrepancy became larger when oxygen saturation level decreased, in particular in thermocline water (at 20% oxygen saturation level, modeled δ18O was heavier than observed values by +7‰). Sensitivity simulations with the GCM model revealed that (1) simply changing the intensity of oxygen consumption by respiration/organic matter decomposition nor physical processes (diffusion and/or advection) could explain the observed relationship between DO and δ18O, (2) applying a smaller isotopic fractionation for deep waters

  5. High-pressure injection of dissolved oxygen for hydrocarbon remediation in a fractured dolostone aquifer

    Science.gov (United States)

    Greer, K. D.; Molson, J. W.; Barker, J. F.; Thomson, N. R.; Donaldson, C. R.

    2010-10-01

    A field experiment was completed at a fractured dolomite aquifer in southwestern Ontario, Canada, to assess the delivery of supersaturated dissolved oxygen (supersaturated with respect to ambient conditions) for enhanced bioremediation of petroleum hydrocarbons in groundwater. The injection lasted for 1.5 h using iTi's gPro® oxygen injection technology at pressures of up to 450 kPa and at concentrations of up to 34 mg O 2/L. A three-dimensional numerical model for advective-dispersive transport of dissolved oxygen within a discretely-fractured porous medium was calibrated to the observed field conditions under a conservative (no-consumption) scenario. The simulation demonstrated that oxygen rapidly filled the local intersecting fractures as well as the porous matrix surrounding the injection well. Following injection, the local fractures were rapidly flushed by the natural groundwater flow system but slow back-diffusion ensured a relatively longer residence time in the matrix. A sensitivity analysis showed significant changes in behaviour with varying fracture apertures and hydraulic gradients. Applying the calibrated model to a 7-day continuous injection scenario showed oxygen residence times (at the 3 mg/L limit), within a radius of 2-4 m from the injection well, of up to 100 days. This study has demonstrated that supersaturated dissolved oxygen can be effectively delivered to this type of a fractured and porous bedrock system at concentrations and residence times potentially sufficient for enhanced aerobic biodegradation.

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

    Science.gov (United States)

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

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

    Science.gov (United States)

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

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

    Science.gov (United States)

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

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

    Science.gov (United States)

    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, ...

  10. Feed intake, growth and metabolism of Nile tilapia (Oreochromis niloticus) in relation to dissolved oxygen concentration

    NARCIS (Netherlands)

    Tran-Duy, A.; Dam, van A.A.; Schrama, J.W.

    2012-01-01

    The objectives of the present study were to determine, for Nile tilapia of different body weights and fed to satiation, (1) the incipient dissolved oxygen (DO) concentration at which feed intake starts to level off and (2) the effect of DO on nitrogen and energy balances. Two successive experiments

  11. Effect of Dissolved Oxygen Concentration on Development and Hatching of Channel Catfish Ictalurus punctatus Eggs

    Science.gov (United States)

    Recommendations on required dissolved oxygen (DO) concentrations in channel catfish hatcheries vary widely. This study was conducted to determine effects of DO concentration on development and hatching success of channel catfish eggs. Five channel catfish spawns were collected from a pond at the T...

  12. DISSOLVED OXYGEN MODELLING USING ARTIFICIAL NEURAL NETWORK: A CASE OF RIVER NZOIA, LAKE VICTORIA BASIN, KENYA

    Directory of Open Access Journals (Sweden)

    Edwin Kimutai Kanda

    2016-11-01

    Full Text Available River Nzoia in Kenya, due to its role in transporting industrial and municipal wastes in addition to agricultural runoff to Lake Victoria, is vulnerable to pollution. Dissolved oxygen is one of the most important indicators of water pollution. Artificial neural network (ANN has gained popularity in water quality forecasting. This study aimed at assessing the ability of ANN to predict dissolved oxygen using four input variables of temperature, turbidity, pH and electrical conductivity. Multilayer perceptron network architecture was used in this study. The data consisted of 113 monthly values for the input variables and output variable from 2009–2013 which were split into training and testing datasets. The results obtained during training and testing were satisfactory with R2 varying from 0.79 to 0.94 and RMSE values ranging from 0.34 to 0.64 mg/l which imply that ANN can be used as a monitoring tool in the prediction of dissolved oxygen for River Nzoia considering the non-correlational relationship of the input and output variables. The dissolved oxygen values follow seasonal trend with low values during dry periods.

  13. EQUILIBRIUM AND KINETIC NITROGEN AND OXYGEN-ISOTOPE FRACTIONATIONS BETWEEN DISSOLVED AND GASEOUS N2O

    NARCIS (Netherlands)

    INOUE, HY; MOOK, WG

    1994-01-01

    Experiments were performed to determine the equilibrium as well as kinetic stable nitrogen and oxygen isotope fractionations between aqueous dissolved and gaseous N2O. The equilibrium fractionations, defined as the ratio of the isotopic abundance ratios (15R and 18R, respectively) of gaseous and

  14. A Simplified and Inexpensive Method for Measuring Dissolved Oxygen in Water.

    Science.gov (United States)

    Austin, John

    1983-01-01

    A modified Winkler method for determining dissolved oxygen in water is described. The method does not require use of a burette or starch indicator, is simple and inexpensive and can be used in the field or laboratory. Reagents/apparatus needed and specific procedures are included. (JN)

  15. Rainbow trout responses to water temperature and dissolved oxygen stress in two southern California stream pools

    Science.gov (United States)

    K.R. Matthews; N.H. Berg

    1997-01-01

    Habitat use by rainbow trout Oncorhynchus mykiss is described for a southern California stream where the summer water temperatures typically exceed the lethal limits for trout (>25) C). During August 1994, water temperature, dissolved oxygen (DO), and trout distribution were monitored in two adjacent pools in Sespe Creek, Ventura County, where summer water...

  16. Miniature dissolved oxygen and turbulence optical sensor for river and coastal environmental applications

    Science.gov (United States)

    Carapezza, Edward M.; Lombardi, Gabrial; Butman, Jerry; Babb, Ivar

    2009-09-01

    This paper describes an innovative miniature optical sensor for predicting dissolved oxygen concentrations and measuring turbulence in river and littoral water columns. The dissolved oxygen and turbulence sensor consists of a single-frequency laser transmitter and a photodetector on which the scattered light from the turbulent water at the base of a dam or spillway is coherently mixed with a sample of the transmitted beam. This miniature sensor could be used both upstream and downsteam of dams and weirs to predict the amount of dissolved oxygen and turbulence in these waters. It could also be used on mobile platforms, such as unmanned underwater vehicles (UUV's), to monitor the edges of biological or chemical plumes or for wake follow platforms, schools of fish or marine mammals or on stationary unattended underwater sensors to monitor natural aeration and turbulence in littoral and riverine waters. Arrays of fixed unattended sensors could be used to detect the wake of transiting submerged vehicles, scuba divers, marine mammals or large schools of fish. A mobile platform equipped with a miniature sensor could to be cued to the general location and depth of an underwater target and then the platform could use this small aperture sensor to acquire and follow the wake. This dissolved oxygen and turbulence sensor system could be miniaturized and packaged into a very small volume; approximately the size of a wristwatch.

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

    Science.gov (United States)

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

  18. The significance of the activity of dissolved oxygen, and other gases, enhanced by high hydrostatic pressure.

    Science.gov (United States)

    Ludwig, Horst; Macdonald, Alister G

    2005-04-01

    The partial pressure of oxygen and other gases dissolved in water and subjected to high hydrostatic pressure is increased. Although this was established many years ago it remains a problematical phenomenon. The review deals with some of the underlying theoretical difficulties and discusses the kinetic and environmental implications of the pressure-enhanced partial pressures.

  19. DISSOLVED OXYGEN AND METHANE IN WATER BY A GC HEADSPACE EQUILIBRATION TECHNIQUE

    Science.gov (United States)

    An analytical procedure is described for the determination of dissolved oxygen and methane in groundwater samples. The method consists of generating a helium gas headspace in a water filled bottle, and analysis of the headspace by gas chromatography. Other permanent gases such as...

  20. Influence of arterial dissolved oxygen level on venous oxygen saturation: don't forget the PaO2!

    Science.gov (United States)

    Legrand, Matthieu; Vallée, Fabrice; Mateo, Joaquim; Payen, Didier

    2014-06-01

    Dissolved oxygen (i.e., unbound to hemoglobin) is often neglected as a determinant of central venous oxygen saturation (ScvO2) in review articles and textbooks. These statements may lead to potential misinterpretation of SCvO2 value across FiO2 changes. In this study, we aimed to explore the influence of PaO2 and FiO2 on ScvO2 in ventilated critically ill patients. This was a prospective observational study in two surgical intensive care units. Mechanically ventilated and sedated patients with cardiac output and ScvO2 monitoring and PaO2/FiO2 > 200 with inspiratory oxygen (FiO2) ≤ 0.5 were enrolled (cohort [ScvO2]). A second cohort of brain-injured patients with jugular venous oxygen saturation monitoring was studied to assess the application of the results to regional circulation (cohort [SjvO2]). Central venous oxygen saturation was measured at baseline FiO2 and at FiO2 = 1. We finally estimated the participation of the dissolved oxygen (PadissolvO2) to the ScvO2 variations. Twenty patients formed the cohort ScvO2 and eight formed the cohort SjvO2. Central venous oxygen saturation rose from 71% (69%-76%) to 84% (78%-88%) after increasing FiO2, whereas PaO2 rose from 100 (85-124) mmHg to 387 (360-449) mmHg. The rise of ScvO2 was mostly ascribable to the dissolved oxygen. The increase of ScvO2 was not explained by changes in cardiac output or hemoglobin levels. Jugular venous oxygen saturation rose from 71% (58%-78%) to 83% (78%-89%) after increasing FiO2. Arterial dissolved oxygen level can significantly influence the ScvO2 value. Therefore, PaO2 should not be overlooked while considering the ScvO2 value as a therapeutic goal. Interpretation of ScvO2 variations in response to a therapeutic challenge (i.e., fluid challenge, inotropic drug initiation) should be performed at constant FiO2.

  1. Dissolved Oxygen Availability on Traditional Pond Using Silvofishery Pattern in Mahakam Delta

    Directory of Open Access Journals (Sweden)

    Ismail Fahmy Almadi

    2013-06-01

    Full Text Available The development of aquaculture system should meet the community’s basic need economically by taking into account the carrying capacity and environmental sustainability. The development of the environmentally friendly system such as silvofishery is being promoted by government however its yield has not reached the target yet. Dissolved oxygen availability is an important indicator which determines the success of the aquaculture system. The objective of the research was to determine dissolved oxygen availability on traditional pond systems using silvofishery pattern. Time series data collection was conducted once in 14 days with 2 measuring times; in the morning (06.00 am and in the evening (06.00 pm for 112 days. The research was conducted at four different silvofishery pond patterns, Pond Pattern 1 (0% mangrove canopy covered, Pond Pattern 2 (35% mangrove canopy covered, Pond Pattern 3 (67% mangrove canopy covered, and Pond Pattern 4 (75% mangrove canopy covered. Measurement was observed openly in the pond (in situ with parameters: dissolved oxygen, temperature, Water pH, Salinity, Transparency, Wind Speed, and Depth of Water Table, while chlorofil-a was ex-situ measured. The result from each parameter was compared to optimum concentration rate for shrimp growth. From the experiment, Pond Pattern 1 showed the most satisfaction results. Its dissolved oxygen availability during the research was ≥ 4 mg/L which was 5.88 mg/L ±0.48 mg/L in the evening (06.00 pm and 4.33 mg/L ±1.24 mg/L in the morning (06.00 am. It was also supported by optimum condition of other parameters such as temperature, Water pH, Salinity, Wind Speed, and Depth of Water Table. However, it was not supported by fertility and transparency of water. Thus, the traditional pattern of conservation still needs additional technology to maintain adequate dissolved oxygen availability for optimum shrimp growth.

  2. Oxygen isotope fractionation in phosphates: the role of dissolved complex anions in isotope exchange.

    Science.gov (United States)

    Zheng, Yong-Fei

    2016-01-01

    Oxygen isotope fractionation factors for phosphates were calculated by means of the increment method. The results suggest that Ag3PO4 and BiPO4 are enriched in (18)O relative to AgPO4, and the three phosphates are consistently depleted in (18)O relative to Ba3[PO4]2; fluorapatite and chlorapatite exhibit a similar behaviour of oxygen isotope fractionation with consistent enrichment of (18)O relative to hydroxyapatite. The valence, radii and coordination of metal cations play a quantitative role in dictating the (18)O/(16)O partitioning in these phosphates of different compositions. The calculated fractionation factors for the Ag3PO4-H2O system are in agreement with experimental determinations derived from enzyme-catalysed isotope exchange between dissolved inorganic phosphate and water at the longest reaction durations at low temperatures. This demonstrates that the precipitated Ag3PO4 has completely captured the oxygen isotope fractionation in the dissolved inorganic phosphate. The calculated fractionation factors for the F/Cl-apatite-water systems are in agreement with the enzyme-catalysed experimental fractionations for the dissolved phosphate-water system at the longest reaction durations but larger than fractionations derived from bacteria-facilitated exchange and inorganic precipitation experiments as well as natural observations. For the experimental calibrations of oxygen isotope fractionation involving the precipitation of dissolved phosphate species from aqueous solutions, the fractionation between precipitate and water is primarily dictated by the isotope equilibration between the dissolved complex anions and water prior to the precipitation. Therefore, the present results provide a quantitative means to interpret the temperature dependence of oxygen isotope fractionation in inorganic and biogenic phosphates.

  3. Effect of dissolved oxygen concentration on nitrite accumulation in nitrifying sequencing batch reactor.

    Science.gov (United States)

    Sánchez, Omar; Bernet, Nicolas; Delgenès, Jean-Philippe

    2007-08-01

    A mathematical model based on Activated Sludge Model No. 3 (International Water Association, London) and laboratory-scale experiments were used to investigate ammonia conversion by nitrification in a sequencing batch reactor (SBR). The purpose of the study was to assess the effect of dissolved oxygen concentration on nitrite accumulation in the SBR. As the dissolved oxygen concentration in the SBR depends on the balance between oxygen consumption and oxygen transfer rates, ammonium conversion was measured for different air flowrate values to obtain different dissolved oxygen concentration profiles during the cycle. The ammonia concentration in the feeding medium was 500 mg ammonium as nitrogen (N-NH4(+))/L, and the maximum nitrite concentration achieved during a cycle was approximately 50 mg nitrite as nitrogen (N-NO2)/L. The air flow supplied to the reactor was identified as a suitable parameter to control nitrite accumulation in the SBR. This identification was carried out based on experimental results and simulation with a calibrated model. At a low value of the volumetric mass-transfer coefficient (kLa), the maximum nitrite concentration achieved during a cycle depends strongly on k(L)a, whereas, at a high value of k(L)a, the maximum nitrite concentration was practically independent of kL(a).

  4. Optimizations on supply and distribution of dissolved oxygen in constructed wetlands: A review.

    Science.gov (United States)

    Liu, Huaqing; Hu, Zhen; Zhang, Jian; Ngo, Huu Hao; Guo, Wenshan; Liang, Shuang; Fan, Jinlin; Lu, Shaoyong; Wu, Haiming

    2016-08-01

    Dissolved oxygen (DO) is one of the most important factors that can influence pollutants removal in constructed wetlands (CWs). However, problems of insufficient oxygen supply and inappropriate oxygen distribution commonly exist in traditional CWs. Detailed analyses of DO supply and distribution characteristics in different types of CWs were introduced. It can be concluded that atmospheric reaeration (AR) served as the promising point on oxygen intensification. The paper summarized possible optimizations of DO in CWs to improve its decontamination performance. Process (tidal flow, drop aeration, artificial aeration, hybrid systems) and parameter (plant, substrate and operating) optimizations are particularly discussed in detail. Since economic and technical defects are still being cited in current studies, future prospects of oxygen research in CWs terminate this review.

  5. Derivation of habitat-specific dissolved oxygen criteria for Chesapeake Bay and its tidal tributaries

    Science.gov (United States)

    Batiuk, R.A.; Breitburg, D.L.; Diaz, R.J.; Cronin, T. M.; Secor, D.H.; Thursby, G.

    2009-01-01

    The Chesapeake 2000 Agreement committed its state and federal signatories to "define the water quality conditions necessary to protect aquatic living resources" in the Chesapeake Bay (USA) and its tidal tributaries. Hypoxia is one of the key water quality issues addressed as a result of the above Agreement. This paper summarizes the protection goals and specific criteria intended to achieve those goals for addressing hypoxia. The criteria take into account the variety of Bay habitats and the tendency towards low dissolved oxygen in some areas of the Bay. Stressful dissolved oxygen conditions were characterized for a diverse array of living resources of the Chesapeake Bay by different aquatic habitats: migratory fish spawning and nursery, shallow-water, open-water, deep-water, and deep-channel. The dissolved oxygen criteria derived for each of these habitats are intended to protect against adverse effects on survival, growth, reproduction and behavior. The criteria accommodate both spatial and temporal aspects of low oxygen events, and have been adopted into the Chesapeake Bay states - Maryland, Virginia, and Delaware - and the District of Columbia's water quality standards regulations. These criteria, now in the form of state regulatory standards, are driving an array of land-based and wastewater pollution reduction actions across the six-watershed.

  6. Simulations of dissolved oxygen concentration in CMIP5 Earth system models

    Institute of Scientific and Technical Information of China (English)

    BAO Ying; LI Yangchun

    2016-01-01

    The climatologies of dissolved oxygen concentration in the ocean simulated by nine Earth system models (ESMs) from the historical emission driven experiment of CMIP5 (Phase 5 of the Climate Model Inter-comparison Project) are quantitatively evaluated by comparing the simulated oxygen to the WOA09 observation based on common statistical metrics. At the sea surface, distribution of dissolved oxygen is well simulated by all nine ESMs due to well-simulated sea surface temperature (SST), with both globally-averaged error and root mean square error (RMSE) close to zero, and both correlation coefficients and normalized standard deviation close to 1. However, the model performance differs from each other at the intermediate depth and deep ocean where important water masses exist. At the depth of 500 to 1 000 m where the oxygen minimum zones (OMZs) exist, all ESMs show a maximum of globally-averaged error and RMSE, and a minimum of the spatial correlation coefficient. In the ocean interior, the reason for model biases is complicated, and both the meridional overturning circulation (MOC) and the particulate organic carbon flux contribute to the biases of dissolved oxygen distribution. Analysis results show the physical bias contributes more. Simulation bias of important water masses such as North Atlantic Deep Water (NADW), Antarctic Bottom Water (AABW) and North Pacific Intermediate Water (NPIW) indicated by distributions of MOCs greatly affects the distributions of oxygen in north Atlantic, Southern Ocean and north Pacific, respectively. Although the model simulations of oxygen differ greatly from each other in the ocean interior, the multi-model mean shows a better agreement with the observation.

  7. Episodes of low dissolved oxygen indicated by ostracodes and sediment geochemistry at Crystal Lake, Illinois, USA

    Science.gov (United States)

    Curry, B. Brandon; Filippelli, G.M.

    2010-01-01

    Low dissolved oxygen during the summer and early fall controls profundal continental ostracode distribution in Crystal Lake (McHenry County), Illinois, favoring Cypria ophthalmica and Physocypria globula at water depths from 6 to 13 m. These species also thrived in the lake's profundal zone from 14,165 to 9600 calendar year before present (cal yr b.p.) during the late Boiling, Allerod, and Younger Dryas chronozones, and early Holocene. Characterized by sand, cemented tubules, large aquatic gastropod shells, and littoral ostracode valves, thin (1-6 cm) tempestite deposits punctuate thicker deposits of organic gyttja from 16,080 to 11,900 cal yr b.p. The succeeding 2300 yr (11,900-9600 cal yr b.p.) lack tempestites, and reconstructed water depths were at their maximum. Deposition of marl under relatively well-oxygenated conditions occurred during the remainder of the Holocene until the arrival of Europeans, when the lake returned to a pattern of seasonally low dissolved oxygen. Such conditions are also indicated in the lake sediment by the speciation of phosphorus, high concentrations of organic carbon, and abundant iron and manganese occluded to mineral grains. Initial low dissolved oxygen was probably caused by the delivery of dissolved P and Fe in shallow groundwater, the chemistry of which was influenced by Spodosol pedogenesis under a spruce forest. The triggering may have been regionally warm and wet conditions associated with retreat of the Lake Michigan lobe (south-central Laurentide Ice Sheet). ?? 2010, by the American Society of Limnology and Oceanography Inc.

  8. THE STRENGTH OF THE DISSOLVED OXYGEN MAXIMUM IN THE VERTICAL DISTRIBUTION OF N ANSHA ISLANDS WATERS

    Institute of Scientific and Technical Information of China (English)

    林洪瑛; 程赛伟; 韩舞鹰

    2002-01-01

    Observation data from a cruise in the Nansha Islands, in May to June 1990, Decem ber, 1993, September to October 1994, and July, 1999, respectively, were used to develop the method presented here to indicate the existing strength of the diss ol ved oxygen maximum in the vertical distribution of Nansha Islands waters. Its se asonal variation and regional distribution are discussed in this paper. Analysis results showed that the distribution of the strength of dissolved oxygen maximum (Domax-Dosur) was closely related to the upper layer circulation and the bioactivity of Nansha Islands seawater.

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

    Science.gov (United States)

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

    2016-03-01

    In vitro cell culture has provided a useful model to study the effects of oxygen on cellular behavior. However, it remains unknown whether the in vitro operations themselves affect the medium oxygen levels and the living states of cells. In addition, a prevailing controversy is whether reactive oxygen species (ROS) production is induced by continuous hypoxia or reoxygenation. In this study, we have measured the effects of different types of cell culture containers and the oxygen environment where medium replacement takes place on the actual oxygen tension in the medium. We found that the deviations of oxygen concentrations in the medium are much greater in 25-cm(2) flasks than in 24-well plates and 35-mm dishes. The dissolved oxygen concentrations in the medium were increased after medium replacement in normoxia, but remained unchanged in glove boxes in which the oxygen tension remained at a low level (11.4, 5.7, and 0.5% O2 ). We also found that medium replacement in normoxia increased the number of ROS-positive cells and reduced the cell viability; meanwhile, medium replacement in a glove box did not produce the above effects. Therefore, we conclude that the use of 25-cm(2) flasks should be avoided and demonstrate that continuous hypoxia does not produce ROS, whereas the reoxygenation that occurs during the harvesting of cells leads to ROS and induces cell death. © 2015 International Federation for Cell Biology.

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

    Science.gov (United States)

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

    2015-06-01

    Controlling local dissolved oxygen concentration (DO) in media is critical for cell or tissue cultures. Various biomaterials and culture methods have been developed to modulate DO. Direct measurement of local DO in cultures has not been validated as a method to test DO modulation. In the present study we developed a DO measurement system equipped with a Clark-type oxygen microelectrode manipulated with 1 μm precision in three-dimensional space to explore potential applications for tissue engineering. By determining the microelectrode tip position precisely against the bottom plane of culture dishes with rat or human cardiac cells in static monolayer culture, we successfully obtained spatial distributions of DO in the medium. Theoretical quantitative predictions fit the obtained data well. Based on analyses of the variance between samples, we found the data reflected "local" oxygen consumption in the vicinity of the microelectrode and the detection of temporal changes in oxygen consumption rates of cultured cells was limited by the diffusion rate of oxygen in the medium. This oxygen measuring system monitors local oxygen consumption and production with high spatial resolution, and can potentially be used with recently developed oxygen modulating biomaterials to design microenvironments and non-invasively monitor local DO dynamics during culture. © 2015 Wiley Periodicals, Inc.

  11. Aquatic macroinvertebrates associated with Eichhornia azurea (Swartz Kunth and relationships with abiotic factors in marginal lentic ecosystems (São Paulo, Brazil

    Directory of Open Access Journals (Sweden)

    CV. Silva

    Full Text Available Marginal lakes are characterised by their having high biological diversity due to the presence of aquatic macrophytes in their coastal zones, providing habitats for refuge and food for animal community members. Among the fauna components associated with macrophytes, aquatic macroinvertebrates are important because they are an energy source for predators and fish. In six lakes and two different seasons (March and August 2009, the ecological attributes of aquatic macroinvertebrate community associated with Eichhornia azurea were compared and the controlling environmental factors were identified. Since the attributes of macroinvertebrate community are strictly associated with abiotic variables of each distinct habitat, our hypothesis was that each site associated with the same floating aquatic macrophyte (E. azurea should have a typical composition and density of organisms. We identified 50 taxa of macroinvertebrates, with greater taxa richness for aquatic insects (37 taxa divided into eight orders; the order Diptera being the most abundant in the two study periods. On the other hand, higher values of total taxa richness were recorded in August. Dissolved oxygen and pH presented the greatest number of significant positive correlations with the different taxa. The animals most frequently collected in the six lakes in March and August 2009 were Hirudinea, Oligochaeta, Hydrachnidae, Conchostraca, Ostracoda, Noteridae, Ceratopogonidae, Chironomidae, Culicidae, Caenidae, Pleidae, Aeshnidae, Libellulidae, Coenagrionidae and Nematoda. Only densities of Trichoptera, Ostracoda and Conchostraca presented the highest significant differences between lakes in both study periods and considering the composition of macroinvertebrates no significant differences were registered for macroinvertebrate composition.

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

    Science.gov (United States)

    Ebbert, J.C.

    2002-01-01

    The U.S. Geological Survey, Washington State Department of Ecology, and Puyallup Tribe of Indians conducted a study in August and September 2001 to assess factors affecting concentrations of dissolved oxygen in the lower Puyallup and White Rivers, Washington. The study was initiated because observed concentrations of dissolved oxygen in the lower Puyallup River fell to levels ranging from less than 1 milligram per liter (mg/L) to about 6 mg/L on several occasions in September 2000. The water quality standard for the concentration of dissolved oxygen in the Puyallup River is 8 mg/L.This study concluded that inundation of the sensors with sediment was the most likely cause of the low concentrations of dissolved oxygen observed in September 2000. The conclusion was based on (1) knowledge gained when a dissolved-oxygen sensor became covered with sediment in August 2001, (2) the fact that, with few exceptions, concentrations of dissolved oxygen in the lower Puyallup and White Rivers did not fall below 8 mg/L in August and September 2001, and (3) an analysis of other mechanisms affecting concentrations of dissolved oxygen.The analysis of other mechanisms indicated that they are unlikely to cause steep declines in concentrations of dissolved oxygen like those observed in September 2000. Five-day biochemical oxygen demand ranged from 0.22 to 1.78 mg/L (mean of 0.55 mg/L), and river water takes only about 24 hours to flow through the study reach. Photosynthesis and respiration cause concentrations of dissolved oxygen in the lower Puyallup River to fluctuate as much as about 1 mg/L over a 24-hour period in August and September. Release of water from Lake Tapps for the purpose of hydropower generation often lowered concentrations of dissolved oxygen downstream in the White River by about 1 mg/L. The effect was smaller farther downstream in the Puyallup River at river mile 5.8, but was still observable as a slight decrease in concentrations of dissolved oxygen caused by

  13. An evaluation of the relative quality of dike pools for benthic macroinvertebrates in the Lower Missouri River, USA

    Science.gov (United States)

    Poulton, B.C.; Allert, A.L.

    2012-01-01

    A habitat-based aquatic macroinvertebrate study was initiated in the Lower Missouri River to evaluate relative quality and biological condition of dike pool habitats. Water-quality and sediment-quality parameters and macroinvertebrate assemblage structure were measured from depositional substrates at 18 sites. Sediment porewater was analysed for ammonia, sulphide, pH and oxidation-reduction potential. Whole sediments were analysed for particle-size distribution, organic carbon and contaminants. Field water-quality parameters were measured at subsurface and at the sediment-water interface. Pool area adjacent and downstream from each dike was estimated from aerial photography. Macroinvertebrate biotic condition scores were determined by integrating the following indicator response metrics: % of Ephemeroptera (mayflies), % of Oligochaeta worms, Shannon Diversity Index and total taxa richness. Regression models were developed for predicting macroinvertebrate scores based on individual water-quality and sediment-quality variables and a water/sediment-quality score that integrated all variables. Macroinvertebrate scores generated significant determination coefficients with dike pool area (R2=0.56), oxidation–reduction potential (R2=0.81) and water/sediment-quality score (R2=0.71). Dissolved oxygen saturation, oxidation-reduction potential and total ammonia in sediment porewater were most important in explaining variation in macroinvertebrate scores. The best two-variable regression models included dike pool size + the water/sediment-quality score (R2=0.84) and dike pool size + oxidation-reduction potential (R2=0.93). Results indicate that dike pool size and chemistry of sediments and overlying water can be used to evaluate dike pool quality and identify environmental conditions necessary for optimizing diversity and productivity of important aquatic macroinvertebrates. A combination of these variables could be utilized for measuring the success of habitat enhancement

  14. Influence of the dissolved oxygen concentration on the penicillin biosynthetic pathway in steady-state cultures of Penicillium chrysogenum

    DEFF Research Database (Denmark)

    Henriksen, Claus Maxel; Nielsen, Jens Bredal; Villadsen, John

    1997-01-01

    The influence the of dissolved oxygen concentration on penicillin biosynthesis was studied in steady-state continuous cultures of a high-yielding strain of Penicillium chrysogenum operated at a dilution rate of 0.05 h-l. The dissolved oxygen concentration was varied between 0.019 and 0.344 mM (co...... and cysteine decreased at low dissolved oxygen concentrations. On the basis of the intracellular pool measurements, metabolic control analysis is performed, and the flux control coefficients for the first two enzymes in the penicillin biosynthetic pathway, i.e., delta......The influence the of dissolved oxygen concentration on penicillin biosynthesis was studied in steady-state continuous cultures of a high-yielding strain of Penicillium chrysogenum operated at a dilution rate of 0.05 h-l. The dissolved oxygen concentration was varied between 0.019 and 0.344 m......M (corresponding to 7% and 131% air saturation at 1 bar) solely through manipulations of the inlet gas composition. At dissolved oxygen concentrations above 0.06-0.08 mM, a constant specific penicillin productivity of around 22 (mu mol/g of DW)/h is maintained. At lower oxygen concentrations, the specific...

  15. Comparison of the abiotic preferences of macroinvertebrates in tropical river basins.

    Directory of Open Access Journals (Sweden)

    Gert Everaert

    Full Text Available We assessed and compared abiotic preferences of aquatic macroinvertebrates in three river basins located in Ecuador, Ethiopia and Vietnam. Upon using logistic regression models we analyzed the relationship between the probability of occurrence of five macroinvertebrate families, ranging from pollution tolerant to pollution sensitive, (Chironomidae, Baetidae, Hydroptilidae, Libellulidae and Leptophlebiidae and physical-chemical water quality conditions. Within the investigated physical-chemical ranges, nine out of twenty-five interaction effects were significant. Our analyses suggested river basin dependent associations between the macroinvertebrate families and the corresponding physical-chemical conditions. It was found that pollution tolerant families showed no clear abiotic preference and occurred at most sampling locations, i.e. Chironomidae were present in 91%, 84% and 93% of the samples taken in Ecuador, Ethiopia and Vietnam. Pollution sensitive families were strongly associated with dissolved oxygen and stream velocity, e.g. Leptophlebiidae were only present in 48%, 2% and 18% of the samples in Ecuador, Ethiopia and Vietnam. Despite some limitations in the study design, we concluded that associations between macroinvertebrates and abiotic conditions can be river basin-specific and hence are not automatically transferable across river basins in the tropics.

  16. Comparison of the abiotic preferences of macroinvertebrates in tropical river basins.

    Science.gov (United States)

    Everaert, Gert; De Neve, Jan; Boets, Pieter; Dominguez-Granda, Luis; Mereta, Seid Tiku; Ambelu, Argaw; Hoang, Thu Huong; Goethals, Peter L M; Thas, Olivier

    2014-01-01

    We assessed and compared abiotic preferences of aquatic macroinvertebrates in three river basins located in Ecuador, Ethiopia and Vietnam. Upon using logistic regression models we analyzed the relationship between the probability of occurrence of five macroinvertebrate families, ranging from pollution tolerant to pollution sensitive, (Chironomidae, Baetidae, Hydroptilidae, Libellulidae and Leptophlebiidae) and physical-chemical water quality conditions. Within the investigated physical-chemical ranges, nine out of twenty-five interaction effects were significant. Our analyses suggested river basin dependent associations between the macroinvertebrate families and the corresponding physical-chemical conditions. It was found that pollution tolerant families showed no clear abiotic preference and occurred at most sampling locations, i.e. Chironomidae were present in 91%, 84% and 93% of the samples taken in Ecuador, Ethiopia and Vietnam. Pollution sensitive families were strongly associated with dissolved oxygen and stream velocity, e.g. Leptophlebiidae were only present in 48%, 2% and 18% of the samples in Ecuador, Ethiopia and Vietnam. Despite some limitations in the study design, we concluded that associations between macroinvertebrates and abiotic conditions can be river basin-specific and hence are not automatically transferable across river basins in the tropics.

  17. Comparison of the Abiotic Preferences of Macroinvertebrates in Tropical River Basins

    Science.gov (United States)

    Everaert, Gert; De Neve, Jan; Boets, Pieter; Dominguez-Granda, Luis; Mereta, Seid Tiku; Ambelu, Argaw; Hoang, Thu Huong; Goethals, Peter L. M.; Thas, Olivier

    2014-01-01

    We assessed and compared abiotic preferences of aquatic macroinvertebrates in three river basins located in Ecuador, Ethiopia and Vietnam. Upon using logistic regression models we analyzed the relationship between the probability of occurrence of five macroinvertebrate families, ranging from pollution tolerant to pollution sensitive, (Chironomidae, Baetidae, Hydroptilidae, Libellulidae and Leptophlebiidae) and physical-chemical water quality conditions. Within the investigated physical-chemical ranges, nine out of twenty-five interaction effects were significant. Our analyses suggested river basin dependent associations between the macroinvertebrate families and the corresponding physical-chemical conditions. It was found that pollution tolerant families showed no clear abiotic preference and occurred at most sampling locations, i.e. Chironomidae were present in 91%, 84% and 93% of the samples taken in Ecuador, Ethiopia and Vietnam. Pollution sensitive families were strongly associated with dissolved oxygen and stream velocity, e.g. Leptophlebiidae were only present in 48%, 2% and 18% of the samples in Ecuador, Ethiopia and Vietnam. Despite some limitations in the study design, we concluded that associations between macroinvertebrates and abiotic conditions can be river basin-specific and hence are not automatically transferable across river basins in the tropics. PMID:25279673

  18. Gulf of Mexico Hypoxia Watch Bottom Dissolved Oxygen Contours for June and July SEAMAP Cruise of 2006

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Hypoxia Watch project provides near-real-time, web-based maps of dissolved oxygen near the sea floor over the Texas-Louisiana continental shelf during a...

  19. Gulf of Mexico Hypoxia Watch Bottom Dissolved Oxygen Contours for June and July SEAMAP Cruise of 2002

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Hypoxia Watch project provides near-real-time, web-based maps of dissolved oxygen near the sea floor over the Texas-Louisiana continental shelf during a...

  20. Gulf of Mexico Hypoxia Watch Bottom Dissolved Oxygen Contours for June and July SEAMAP Cruise of 2003

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Hypoxia Watch project provides near-real-time, web-based maps of dissolved oxygen near the sea floor over the Texas-Louisiana continental shelf during a...

  1. Gulf of Mexico Hypoxia Watch Bottom Dissolved Oxygen Contours for June and July SEAMAP Cruise of 2005

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Hypoxia Watch project provides near-real-time, web-based maps of dissolved oxygen near the sea floor over the Texas-Louisiana continental shelf during a...

  2. Gulf of Mexico Hypoxia Watch Bottom Dissolved Oxygen Contours for June and July SEAMAP Cruise of 2009

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Hypoxia Watch project provides near-real-time, web-based maps of dissolved oxygen near the sea floor over the Texas-Louisiana continental shelf during a...

  3. Gulf of Mexico Hypoxia Watch Bottom Dissolved Oxygen Contours for June and July SEAMAP Cruise of 2012

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Hypoxia Watch project provides near-real-time, web-based maps of dissolved oxygen near the sea floor over the Texas-Louisiana continental shelf during a...

  4. Gulf of Mexico Hypoxia Watch Bottom Dissolved Oxygen Contours for June and July SEAMAP Cruise of 2004

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Hypoxia Watch project provides near-real-time, web-based maps of dissolved oxygen near the sea floor over the Texas-Louisiana continental shelf during a...

  5. Gulf of Mexico Hypoxia Watch Bottom Dissolved Oxygen Contours for June and July SEAMAP Cruise of 2013

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Hypoxia Watch project provides near-real-time, web-based maps of dissolved oxygen near the sea floor over the Texas-Louisiana continental shelf during a...

  6. Gulf of Mexico Hypoxia Watch Bottom Dissolved Oxygen Contours for June and July SEAMAP Cruise of 2008

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Hypoxia Watch project provides near-real-time, web-based maps of dissolved oxygen near the sea floor over the Texas-Louisiana continental shelf during a...

  7. Gulf of Mexico Hypoxia Watch Bottom Dissolved Oxygen Contours for June and July SEAMAP Cruise of 2015

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Hypoxia Watch project provides near-real-time, web-based maps of dissolved oxygen near the sea floor over the Texas-Louisiana continental shelf during a...

  8. Gulf of Mexico Hypoxia Watch Bottom Dissolved Oxygen Contours for October and November SEAMAP Cruise of 2008

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Hypoxia Watch project provides near-real-time, web-based maps of dissolved oxygen near the sea floor over the Texas-Louisiana continental shelf during a...

  9. Gulf of Mexico Hypoxia Watch Bottom Dissolved Oxygen Contours for June and July SEAMAP Cruise of 2011

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Hypoxia Watch project provides near-real-time, web-based maps of dissolved oxygen near the sea floor over the Texas-Louisiana continental shelf during a...

  10. Gulf of Mexico Hypoxia Watch Bottom Dissolved Oxygen Contours for June and July SEAMAP Cruise of 2001

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Hypoxia Watch project provides near-real-time, web-based maps of dissolved oxygen near the sea floor over the Texas-Louisiana continental shelf during a...

  11. Gulf of Mexico Hypoxia Watch Bottom Dissolved Oxygen Contours for June and July SEAMAP Cruise of 2007

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Hypoxia Watch project provides near-real-time, web-based maps of dissolved oxygen near the sea floor over the Texas-Louisiana continental shelf during a...

  12. Gulf of Mexico Hypoxia Watch Bottom Dissolved Oxygen Contours for June and July SEAMAP Cruise of 2014

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Hypoxia Watch project provides near-real-time, web-based maps of dissolved oxygen near the sea floor over the Texas-Louisiana continental shelf during a...

  13. Gulf of Mexico Hypoxia Watch Bottom Dissolved Oxygen Contours for June and July SEAMAP Cruise of 2010

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Hypoxia Watch project provides near-real-time, web-based maps of dissolved oxygen near the sea floor over the Texas-Louisiana continental shelf during a...

  14. PHOTOGENERATION OF SINGLET OXYGEN AND FREE RADICALS IN DISSOLVED ORGANIC MATTER ISOLATED FROM THE MISSISSIPPI AND ATCHAFALAYA RIVER PLUMES

    Science.gov (United States)

    The photoreactivity to UV light of ultrafiltered dissolved organic matter (DOM) collected during cruises along salinity transects in the Mississippi and Atchafalaya River plumes was examined by measuring photogenerated free radicals and singlet molecular oxygen (1O2) photosensiti...

  15. Bottom Dissolved Oxygen Maps From SEAMAP Summer and Fall Groundfish/Shrimp Surveys from 1982 to 1998 (NCEI Accession 0155488)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Bottom dissolved oxygen (DO) data was extracted from environmental profiles acquired during the Southeast Fisheries Science Center Mississippi Laboratories summer...

  16. Characterization of water quality and simulation of temperature, nutrients, biochemical oxygen demand, and dissolved oxygen in the Wateree River, South Carolina, 1996-98

    Science.gov (United States)

    Feaster, Toby D.; Conrads, Paul A.

    2000-01-01

    In May 1996, the U.S. Geological Survey entered into a cooperative agreement with the Kershaw County Water and Sewer Authority to characterize and simulate the water quality in the Wateree River, South Carolina. Longitudinal profiling of dissolved-oxygen concentrations during the spring and summer of 1996 revealed dissolved-oxygen minimums occurring upstream from the point-source discharges. The mean dissolved-oxygen decrease upstream from the effluent discharges was 2.0 milligrams per liter, and the decrease downstream from the effluent discharges was 0.2 milligram per liter. Several theories were investigated to obtain an improved understanding of the dissolved-oxygen dynamics in the upper Wateree River. Data suggest that the dissolved-oxygen concentration decrease is associated with elevated levels of oxygen-consuming nutrients and metals that are flowing into the Wateree River from Lake Wateree. Analysis of long-term streamflow and water-quality data collected at two U.S. Geological Survey gaging stations suggests that no strong correlation exists between streamflow and dissolved-oxygen concentrations in the Wateree River. However, a strong negative correlation does exist between dissolved-oxygen concentrations and water temperature. Analysis of data from six South Carolina Department of Health and Environmental Control monitoring stations for 1980.95 revealed decreasing trends in ammonia nitrogen at all stations where data were available and decreasing trends in 5-day biochemical oxygen demand at three river stations. The influence of various hydrologic and point-source loading conditions on dissolved-oxygen concentrations in the Wateree River were determined by using results from water-quality simulations by the Branched Lagrangian Transport Model. The effects of five tributaries and four point-source discharges were included in the model. Data collected during two synoptic water-quality samplings on June 23.25 and August 11.13, 1997, were used to calibrate

  17. Dissolved oxygen control and monitoring implementation in the liquid lead bismuth eutectic loop: HELIOS

    Science.gov (United States)

    Nam, Hyo On; Lim, Jun; Han, Dong Yoon; Hwang, Il Soon

    2008-06-01

    A 12 m tall LBE coolant loop, named as HELIOS, has been developed by thermal-hydraulic scaling of the PEACER-300MWe. Thermo-hydraulic experiment and materials test are the principal purposes of HELIOS operation. In this study, an yttria stabilized zirconia (YSZ) based oxygen sensor that was hermetically sealed for long-term applications using the electromagnetically swaged metal-ceramic joining method, have been developed for high temperature oxygen control application over a long period of time. The rugged electrode design has been calibrated to absolute metal-oxide equilibrium by using a first principle of detecting pure metal-oxide transition using electrochemical impedance spectroscopy (EIS). During the materials tests in HELIOS, dissolved oxygen concentration was administered at the intended condition of 10 -6 wt% by direct gas bubbling with Ar + 4%H 2, Ar + 5%O 2 and/or pure Ar while corrosion tests were conducted for up to 1000 h with inspection after each 333 h. During the total 1000 h corrosion test, oxygen concentration was measured by oxygen sensor. The result confirmed that the direct gas bubbling method is a viable and practical option for controlling oxygen concentration in large loops including HELIOS.

  18. Oxygen transfer dynamics and activated sludge floc structure under different sludge retention times at low dissolved oxygen concentrations.

    Science.gov (United States)

    Fan, Haitao; Liu, Xiuhong; Wang, Hao; Han, Yunping; Qi, Lu; Wang, Hongchen

    2017-02-01

    In activated sludge systems, the aeration process consumes the most energy. The energy cost can be dramatically reduced by decreasing the operating dissolved oxygen (DO) concentration. However, low DO may lead to incomplete nitrification and poor settling performance of activated sludge flocs (ASFs). This study investigates oxygen transfer dynamics and settling performances of activated sludge under different sludge retention times (SRTs) and DO conditions using microelectrodes and microscopic techniques. Our experimental results showed that with longer SRTs, treatment capacity and settling performances of activated sludge improved due to smaller floc size and less extracellular polymeric substances (EPS). Long-term low DO conditions produced larger flocs and more EPS per unit sludge, which produced a more extensive anoxic area and led to low oxygen diffusion performance in flocs. Long SRTs mitigated the adverse effects of low DO. According to the microelectrode analysis and fractal dimension determination, smaller floc size and less EPS in the long SRT system led to high oxygen diffusion property and more compact floc structure that caused a drop in the sludge volume index (SVI). In summary, our results suggested that long SRTs of activated sludge can improve the operating performance under low DO conditions. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Impact of dissolved oxygen concentration on some key parameters and production of rhG-CSF in batch fermentation.

    Science.gov (United States)

    Krishna Rao, Dasari V; Ramu, Chatadi T; Rao, Joginapally V; Narasu, Mangamoori L; Bhujanga Rao, Adibhatla Kali S

    2008-09-01

    The impact of different levels of agitation speed, carbondioxide and dissolved oxygen concentration on the key parameters and production of rhG-CSF in Escherichia coli BL21(DE3)PLysS were studied. Lower carbondioxide concentrations as well as higher agitation speeds and dissolved oxygen concentrations led to reduction in the acetate concentrations, and enhanced the cell growth, but inhibited plasmid stability and rhG-CSF expression. Similarly, higher carbondioxide concentrations and lower agitation speeds as well as dissolved oxygen concentrations led to enhanced acetate concentrations, but inhibited the cell growth and protein expression. To address the bottlenecks, a two-stage agitation control strategy (strategy-1) and two-stage dissolved oxygen control strategy (strategy-2) were employed to establish the physiological and metabolic conditions, so as to improve the expression of rhG-CSF. By adopting strategy-1 the yields were improved 1.4-fold over constant speed of 550 rpm, 1.1-fold over constant dissolved oxygen of 45%, respectively. Similarly, using strategy-2 the yields were improved 1.6-fold over constant speed of 550 rpm, 1.3-fold over constant dissolved oxygen of 45%, respectively.

  20. Detection of phosphohydrolytic enzyme activity through the oxygen isotope composition of dissolved phosphate

    Science.gov (United States)

    Colman, A. S.

    2016-02-01

    Phosphohydrolytic enzymes play an important role in phosphorus remineralization. As they release phosphate (Pi) from various organophosphorus compounds, these enzymes facilitate the transfer of oxygen atoms from water to the phosphoryl moieties. Most such enzymatic reactions impart a significant isotopic fractionation to the oxygen transferred. If this reaction occurs within a cell, then the resultant oxygen isotope signal is overprinted by continued recycling of the Pi. However, if this reaction occurs extracellularly, then the isotopic signal will be preserved until the Pi is transported back into a cell. Thus, the oxygen isotope composition of Pi (δ18Op) in an aquatic ecosystem can serve as a useful indicator of the mechanisms by which P is remineralized. We develop a time-dependent model illustrating the sensitivity of the δ18O of dissolved phosphate to various modes of P remineralization. The model is informed by cell lysis experiments that reveal the relative proportions of P­i that are directly liberated from cytosol vs. regenerated from co-liberated dissolved organic phosphorus compounds via extracellular hydrolysis. By incorporating both cellular uptake and release fluxes of P, we show that the degree of isotopic disequilibrium in an aquatic ecosystem can be a strong indicator of P remineralization mode. Apparent oxygen isotope equilibrium between Pi and water arises in this model as a steady-state scenario in which fractionation upon cellular uptake of Pi counterbalances the hydrolytic source flux of disequilibrated Pi. Low and high rates of extracellular phosphohydrolase activity are shown to produce steady-state δ18Op values that are respectively above or below thermodynamic equilibrium compositions.

  1. Modelling nitrogen and phosphorus cycles and dissolved oxygen in the Zhujiang Estuary Ⅱ. Model results

    Institute of Scientific and Technical Information of China (English)

    Guan Weibing; Wong Lai-Ah; Xu Dongfeng

    2001-01-01

    In the present study, the ecosystem-based water quality model was applied to the Pearl River (Zhujiang) Estuary. The model results successfully represent the distribution trend of nutrients and dissolved oxygen both in the horizontal and vertical planes during the flood season, and it shows that the model has taken into consideration the key part of the dynamical, chemical and biological processes existing in the Zhujiang Estuary. The further studies illustrate that nitrogen is in plenty while phosphorus and light limit the phytoplankton biomass in the Zhujiang Estuary during the flood season.

  2. Methods of deoxygenating metals having oxygen dissolved therein in a solid solution

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Ying; Fang, Zhigang Zak; Sun, Pei; Xia, Yang; Zhou, Chengshang

    2017-06-06

    A method of deoxygenating metal can include forming a mixture of: a metal having oxygen dissolved therein in a solid solution, at least one of metallic magnesium and magnesium hydride, and a magnesium-containing salt. The mixture can be heated at a deoxygenation temperature for a period of time under a hydrogen-containing atmosphere to form a deoxygenated metal. The deoxygenated metal can then be cooled. The deoxygenated metal can optionally be subjected to leaching to remove by-products, followed by washing and drying to produce a final deoxygenated metal.

  3. Final Evaluation Memorandum: Strategies for Resolving Low Dissolved Oxygen and Methylmercury Events in Northern Suisun Marsh

    OpenAIRE

    Siegel, Stuart; Bachand, Philip; Gillenwater, Dan; Chappell, Steve; Wickland, Bruce; Rocha, Orlando; Stephenson, Mark; Heim, Wesley; Enright, Chris; Moyle, Peter; Crain, Patrick; Downing, Bryan; Bergamaschi, Brian

    2011-01-01

    The purpose of the project is to improve our understanding about best management practices that can be utilized on diked managed wetlands in Suisun Marsh for reducing the occurrence of low dissolved oxygen (DO) and high methylmercury (MeHg) events associated primarily with fall flood-up practices. Low DO events are of concern because they can lead to undue stress and even mortality of sensitive aquatic organisms. Elevated MeHg levels are of concern because MeHg is a neurotoxin that bio-magnif...

  4. Assessment of Constructed Wetland Biological Integrity Using Aquatic Macroinvertebrates

    Directory of Open Access Journals (Sweden)

    C. Galbrand

    2007-01-01

    Full Text Available A surface flow constructed wetland consisting of seven cells was used to treat the leachates from a decommissioned landfill. Wetland monitoring was performed by evaluating the treatment efficiency of the landfill leachate and the wetland biological integrity of the wetland. The water quality samples were analyzed for iron, manganese, phosphorus (orthophosphate, pH, dissolved oxygen (DO, nitrogen (ammonia, nitrate, nitrite and TKN, chemical oxygen demand (COD, total suspended solids (TSS and total dissolved solids (TDS. Aquatic macroinvertebrates were examined using Average Score per Taxon (ASPT via the Biological Monitoring Working Party (BMWP biotic index, the Ephemeroptera, Trichoptera, Sphaeriidae and Odonata (ETSD biotic index, abundance of mayflies and trophic structure. Reductions of 49.66, 66.66, 1.91, 46.37 and 8.33% were obtained for manganese, orthophosphate, TSS, TDS and COD, respectively. The nitrite, dissolved oxygen and iron concentrations were not in accordance with the water quality guidelines for aquatic life. ASPT, ETSD, percent abundance of mayflies and trophic structure represented moderate to moderately-poor water quality in comparison to a high quality reference site. Iron had most adverse effect on the biological system of the wetland.

  5. Metabolomics analysis of the effect of dissolved oxygen on spinosad production by Saccharopolyspora spinosa.

    Science.gov (United States)

    Lu, Chunzhe; Yin, Jing; Zhao, Fanglong; Li, Feng; Lu, Wenyu

    2017-05-01

    Spinosad, a universal bio-pesticide, is obtained from the soil actinomycete Saccharopolyspora spinosa. Dissolved oxygen, an important contributing factor in aerobic microbial fermentation, however, is not always available in sufficient amounts. To alleviate oxygen limitation in spinosad production, three different oxygen vectors, namely oleic acid, toluene, and n-dodecane, were added into early fermentation. Results indicated that n-dodecane was the optimal oxygen vector. Spinosad yield was increased by 44.2% compared to that in the control group in the presence of 0.5% n-dodecane, added after 120 h of incubation. Yields of the test group reached 6.52 mg/g dry cell weight (DCW), while that of the control group was limited to 4.52 mg/g DCW. Metabolomics analysis by gas chromatography coupled to mass spectrometry was performed to demonstrate the metabolism mechanism in the presence and absence of oxygen vector. In total, 78 principal intracellular metabolites in S. spinosa were detected and quantified in the presence and absence of n-dodecane. Levels of some metabolites that were related to the tricarboxylic acid cycle and pentose phosphate pathway varied significantly. Aspartic acid and glucose-1-phosphate levels varied significantly and contributed most in the distinction of the fermentation conditions and phases. The above findings give new insights into the improvement and the metabolomic characteristics of industrial spinosad production.

  6. Rapid integrated water quality evaluation of Mahisagar river using benthic macroinvertebrates.

    Science.gov (United States)

    Bhadrecha, M H; Khatri, Nitasha; Tyagi, Sanjiv

    2016-04-01

    The water quality of Mahisagar river, near Galteshwar in Kheda district of Gujarat, India, was assessed through a rapid integrated technique by physicochemical parameters as well as benthic macroinvertebrates. Physicochemical parameters retrieved were pH, color, conductivity, total solids, total suspended solids, total dissolved solids, chlorides, total hardness, calcium hardness, magnesium hardness, alkalinity, turbidity, ammoniacal nitrogen, chemical oxygen demand, biochemical oxygen demand, dissolved oxygen, sulfates, and nitrates. The biological indices calculated were BMWP (Bio Monitoring Working Party) score or saprobic score and sequential comparison index or diversity score. In total, 37 families were encountered along the studied river stretch. The findings indicate that the water quality of Mahisagar river at sampled locations is “slightly polluted.” Moreover, the results of physicochemical analysis are also in consonance with the biological water quality criteria developed by Central Pollution Control Board.

  7. Effect of dissolved oxygen on nitrogen fixation by A. vinelandii. II. Ionically adsorbed cells.

    Science.gov (United States)

    Diluccio, R C; Kirwan, D J

    1984-01-01

    Continuous culture studies of Azotobacter vinelandii cells immobilized by ionic adsorption to Cellex E anion exchange resin were conducted under oxygen-limited conditions for comparison to free-cell cultures. Immobilization had little effect upon the specific respiration and sucrose consumption rates as compared to free cells. However, maxima in specific nitrogen fixation rate and nitrogenase activity as a function of dissolved oxygen occurred at a C(O(2) ) value of approximately 0.005 mM as opposed to 0.02 mM for free cells. Further, in contrast to free-cell culture, most of the fixed nitrogen appeared in the medium rather than within intact cells. There were strong indications that reproduction of bound cells often resulted in cell lysis accounting for the fixed nitrogen content in solution.

  8. [Dynamic variance of intracellular metabolic energies under rhythmical control for dissolved oxygen in PHB mixed cultivation].

    Science.gov (United States)

    Qian, Z W; Tohyama, M; Hua, Q; Shimizu, K

    2001-07-01

    The mixed cultivation using cheaper carbon source-wasted food material contained glucose and lactate at the same time was conducted in 5L fermentor, within which glucose was converted to lactate by L. delbrueckii in anaerobic condition and the lactate was converted to PHB by R. eutropha in aerobic condition. Considering dissolved oxygen concentration may affect the level of intracellular ATP and NADPH of the metabolic pathways for R. eutropha in lactate under autotrophy or heterotrophy, rhythmical oscillated control for DO based on chaos control method was consequently presented. This method was employed to satisfy two strains for opposite oxygen preferences, moreover, excite the intracellular metabolic energy simultaneously. The values examined through spectrophotofluorimetry represented that both ATP and NADPH exhibited fluctuations in accordance with the DO rhythm. By means of this control design, the concentration of PHB can be doubled than the usual under stable DO control.

  9. Increasing dissolved-oxygen disrupts iron homeostasis in production cultures of Escherichia coli.

    Science.gov (United States)

    Baez, Antonino; Shiloach, Joseph

    2017-01-01

    The damaging effect of high oxygen concentration on growth of Escherichia coli is well established. Over-oxygenation increases the intracellular concentration of reactive oxygen species (ROS), causing the destruction of the [4Fe-4S] cluster of dehydratases and limiting the biosynthesis of both branched-chain amino acids and nicotinamide adenine dinucleotide. A key enzyme that reduces the damaging effect of superoxide is superoxide dismutase (SOD). Its transcriptional regulation is controlled by global transcription regulators that respond to changes in oxygen and iron concentrations and pH. Production of biological compounds from E. coli is currently achieved using cultures grown to high cell densities which require oxygen-enriched air supply. It is, therefore, important to study the effect of over-oxygenation on E. coli metabolism and the bacterial protecting mechanism. The effect of over-oxygenation on the superoxide dismutase regulation system was evaluated in cultures grown in a bioreactor by increasing the oxygen concentration from 30 to 300 % air saturation. Following the change in the dissolved oxygen (DO), the expression of sodC, the periplasmic CuZn-containing SOD, and sodA, the cytosolic Mn-containing SOD, was higher in all the tested strains, while the expression of the sodB, the cytosolic Fe-containing SOD, was lower. The down-regulation of the sodB was found to be related to the activation of the small RNA RyhB. It was revealed that iron homeostasis, in particular ferric iron, was involved in the RyhB activation and in sodB regulation but not in sodA. Supplementation of amino acids to the culture medium reduced the intracellular ROS accumulation and reduced the activation of both SodA and SodC following the increase in the oxygen concentration. The study provides evidence that at conditions of over-oxygenation, sodA and sodC are strongly regulated by the amount of ROS, in particular superoxide; and sodB is regulated by iron availability through the

  10. Qualified temperature, salinity and dissolved oxygen climatologies in a changing Adriatic Sea

    Directory of Open Access Journals (Sweden)

    M. Lipizer

    2014-02-01

    Full Text Available An updated climatology, based on a comprehensive dataset (1911–2009 of temperature, salinity and dissolved oxygen, has been produced for the whole Adriatic Sea with the Variational Inverse Method using the DIVA software. Climatological maps were produced at 26 levels and validated with Ordinary Cross Validation and with real vs. synthetic Temperature–Salinity diagram intercomparison. The concept of Climatology–Observation Misfit (COM has been introduced as an estimate of the physical variability associated with the climatological structures. In order to verify the temporal stability of the climatology, long-term variability has been investigated in the Mid Adriatic and the South Adriatic Pits, regarded as the most suitable records of possible long-term changes. Compared with previous climatologies, this study reveals a surface temperature rise (up to 2 °C, a clear deep dissolved oxygen minimum in the South Adriatic Gyre and a bottom summer oxygen minimum in the North Adriatic. Below 100 m all properties profoundly differ between the Middle and the South Adriatic. The South Adriatic Pit clearly shows the remote effects of the Eastern Mediterranean Transient, while no effect is observed in Middle Adriatic Pits. The deepest part of the South Adriatic seems now to be significantly saltier (+0.18 since the period 1911–1914, with an increase of +0.018 decade−1 since the late 1940s and warmer (+0.54 °C since 1911–1914, even though a long-term temperature trend could not be statistically demonstrated. Conversely, the Middle Adriatic Pits present a long-term increase in apparent oxygen utilisation (+0.77 mL L−1 since 1911–1914, with a constant increase of +0.2 mL L−1 decade−1 after the 1970s.

  11. Stability of single dispersed silver nanoparticles in natural and synthetic freshwaters: Effects of dissolved oxygen.

    Science.gov (United States)

    Zou, Xiaoyan; Li, Penghui; Lou, Jie; Fu, Xiaoyan; Zhang, Hongwu

    2017-11-01

    Silver nanoparticles (AgNPs) are increasingly used in various commercial products. This increased use raises ecological concerns because of the large release of AgNPs into the environment. Once released, the local water chemistry has the potential to influence the environmental fates and behaviors of AgNPs. The impacts of dissolved oxygen and natural organic matter (NOM) on the dissolution and stability of AgNPs were investigated in synthetic and natural freshwaters for 7 days. In synthetic freshwater, the aggregation of AgNPs occurred due to the compression of the electric double layer, accompanied by the dissolution of AgNPs. However, once oxygen was removed, the highest dissolved Ag (Agdis) concentration decreased from 356.5 μg/L to 272.1 μg/L, the pH of the AgNP suspensions increased from less than 7.6 to more than 8.4, and AgNPs were regenerated by the reduction of released Ag(+) by citrate. The addition of NOM mitigated aggregation, inhibited oxidative dissolution and induced the transformation of AgNPs into Ag2S due to the formation of NOM-adsorbed layers, the reduction of Ag(+) by NOM, and the high affinity of sulfur-enriched species in NOM for Ag. Likewise, in oxygen-depleted natural freshwaters, the inhibition of oxidative dissolution was obtained in comparison with oxygenated freshwaters, showing a decrease in the maximum Agdis concentration from 137.6 and 57.0 μg/L to 83.3 and 42.4 μg/L from two natural freshwater sites. Our results suggested that aggregation and dissolution of AgNPs in aquatic environments depend on the chemical composition, where oxygen-depleted freshwaters more significantly increase the colloidal stability. In comparison with oxic conditions, anoxic conditions were more favorable to the regeneration of AgNPs by reducing species (e.g., citrate and NOM) and enhanced the stability of nanoparticles. This indicates that some AgNPs will be more stable for long periods in oxygen-deprived freshwaters, and pose more serious

  12. Fast Oxidation Processes in a Naturally Reduced Aquifer Zone Caused by Dissolved Oxygen

    Science.gov (United States)

    Davis, J. A.; Jemison, N. E.; Williams, K. H.; Hobson, C.; Bush, R. P.

    2014-12-01

    The occurrence of naturally reduced zones is quite common in alluvial aquifers in the western U.S.A. due to the burial of woody debris in flood plains. The naturally reduced zones are heterogeneously dispersed in such aquifers and are characterized by high concentrations of organic carbon and reduced phases, including iron sulfides and reduced forms of metals, including uranium(IV). The persistence of high concentrations of dissolved uranium(VI) at uranium-contaminated aquifers on the Colorado Plateau has been attributed to slow oxidation of insoluble uranium(IV) mineral phases that are found in association with these natural reducing zones, although there is little understanding of the relative importance of various potential oxidants. Three field experiments were conducted within an alluvial aquifer adjacent to the Colorado River near Rifle, CO wherein groundwater associated with naturally reduced zones was pumped into a gas-impermeable tank, mixed with a conservative tracer (Br-), bubbled with a gas phase composed of 97% O2 and 3% CO2, and then returned to the subsurface in the same well from which it was withdrawn. Within minutes of re-injection of the oxygenated groundwater, dissolved uranium(VI) concentrations increased from less than 1 μM to greater than 2.5 μM, demonstrating that oxygen can be an important oxidant for uranium in these field systems if supplied to the naturally reduced zones. Small concentrations of nitrate were also observed in the previously nitrate-free groundwater, and Fe(II) decreased to the detection limit. These results contrast with other laboratory and field results in which oxygen was introduced to systems containing high concentrations of mackinawite (FeS) rather than the more crystalline iron sulfides found in aged, naturally reduced zones. The flux of oxygen to the naturally reduced zones in the alluvial aquifers occurs mainly through interactions between groundwater and gas phases at the water table, and seasonal variations

  13. In Situ Bioreduction of Uranium (VI) to Submicromolar Levels and Reoxidation by Dissolved Oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Weimin [ORNL; Carley, Jack M [ORNL; Luo, Jian [Stanford University; Ginder-Vogel, Matthew A. [Stanford University; Cardenas, Erick [Michigan State University, East Lansing; Leigh, Mary Beth [Michigan State University, East Lansing; Hwang, Chaichi [Miami University, Oxford, OH; Kelly, Shelly D [Argonne National Laboratory (ANL); Ruan, Chuanmin [ORNL; Wu, Liyou [University of Oklahoma, Norman; Van Nostrand, Joy [University of Oklahoma, Norman; Gentry, Terry J [ORNL; Lowe, Kenneth Alan [ORNL; Mehlhorn, Tonia L [ORNL; Carroll, Sue L [ORNL; Luo, Wensui [ORNL; Fields, Matthew Wayne [Miami University, Oxford, OH; Gu, Baohua [ORNL; Watson, David B [ORNL; Kemner, Kenneth M [Argonne National Laboratory (ANL); Marsh, Terence [Michigan State University, East Lansing; Tiedje, James [Michigan State University, East Lansing; Zhou, Jizhong [University of Oklahoma, Norman; Fendorf, Scott [Stanford University; Kitanidis, Peter K. [Stanford University; Jardine, Philip M [ORNL; Criddle, Craig [ORNL

    2007-01-01

    Groundwater within Area 3 of the U.S. Department of Energy (DOE) Environmental Remediation Sciences Program (ERSP) Field Research Center at Oak Ridge, TN (ORFRC) contains up to 135 {micro}M uranium as U(VI). Through a series of experiments at a pilot scale test facility, we explored the lower limits of groundwater U(VI) that can be achieved by in-situ biostimulation and the effects of dissolved oxygen on immobilized uranium. Weekly 2 day additions of ethanol over a 2-year period stimulated growth of denitrifying, Fe(III)-reducing, and sulfate-reducing bacteria, and immobilization of uranium as U(IV), with dissolved uranium concentrations decreasing to low levels. Following sulfite addition to remove dissolved oxygen, aqueous U(VI) concentrations fell below the U.S. Environmental Protection Agency maximum contaminant limit (MCL) for drinking water (<30 {micro}g L{sup -1} or 0.126 {micro}M). Under anaerobic conditions, these low concentrations were stable, even in the absence of added ethanol. However, when sulfite additions stopped, and dissolved oxygen (4.0-5.5 mg L{sup -1}) entered the injection well, spatially variable changes in aqueous U(VI) occurred over a 60 day period, with concentrations increasing rapidly from <0.13 to 2.0 {micro}M at a multilevel sampling (MLS) well located close to the injection well, but changing little at an MLS well located further away. Resumption of ethanol addition restored reduction of Fe(III), sulfate, and U(VI) within 36 h. After 2 years of ethanol addition, X-ray absorption near-edge structure spectroscopy (XANES) analyses indicated that U(IV) comprised 60-80% of the total uranium in sediment samples. At the completion of the project (day 1260), U concentrations in MLS wells were less than 0.1 {micro}M. The microbial community at MLS wells with low U(VI) contained bacteria that are known to reduce uranium, including Desulfovibrio spp. and Geobacter spp., in both sediment and groundwater. The dominant Fe(III)-reducing species

  14. Visualizing dissolved oxygen transport for liquid ventilation in an in vitro model of the human airways

    Science.gov (United States)

    Janke, T.; Bauer, K.

    2017-04-01

    Up until to now, the measurement of dissolved oxygen concentrations during liquid ventilation is limited to the determination of averaged concentrations of the liquid entering or leaving the body. The work presented in this paper aims to extend the possible measurement techniques in the research of liquid ventilation. Therefore optical measurements of the dissolved oxygen concentration, using a luminescent sensor dye, are performed. The preparation of a suitable sensor liquid, based on the metal complex Dichlorotris(1,10)-(phenanthroline)ruthenium(II), is presented. A transparent simplified human lung geometry is used for conducting the experiments. Inspiratory as well as expiratory flow at three different constant flow rates is investigated, covering the flow regimes \\text{Re}=83 -333 and \\text{Pe}=33 300 -133 000. The applied measurement technique is capable to reveal distinctive concentration patterns during inspiration and expiration caused by the laminar flow characteristics. Allowing a sufficiently long flow duration, local concentration inhomogeneities disappear and an exponential rise and decay of the mean values can be observed for inspiration and expiration.

  15. Enzymatic scavenging of oxygen dissolved in water: Application of response surface methodology in optimization of conditions

    Directory of Open Access Journals (Sweden)

    Karimi Afzal

    2012-01-01

    Full Text Available In this work, removal of dissolved oxygen in water through reduction by glucose, which was catalyzed by glucose oxidase – catalase enzyme, was studied. Central composite design (CCD technique was applied to achieve optimum conditions for dissolved oxygen scavenging. Linear, square and interactions between effective parameters were obtained to develop a second order polynomial equation. The adequacy of the obtained model was evaluated by the residual plots, probability-value, coefficient of determination, and Fisher’s variance ratio test. Optimum conditions for activity of two enzymes in water deoxygenation were obtained as follows: pH=5.6, T=40°C, initial substrate concentration [S] = 65.5 mmol/L and glucose oxidase activity [E] = 252 U/Lat excess amount of catalase. The deoxygenation process during 30 seconds, in the optimal conditions, was predicted 98.2%. Practical deoxygenation in the predicted conditions was achieved to be 95.20% which was close to the model prediction.

  16. Simulating the effects of fluctuating dissolved oxygen on growth, reproduction, and survival of fish and shrimp.

    Science.gov (United States)

    Miller Neilan, Rachael; Rose, Kenneth

    2014-02-21

    Individuals are commonly exposed to fluctuating levels of stressors, while most laboratory experiments focus on constant exposures. We develop and test a mathematical model for predicting the effects of low dissolved oxygen (hypoxia) on growth, reproduction, and survival using laboratory experiments on fish and shrimp. The exposure-effects model simulates the hourly reductions in growth and survival, and the reduction in reproduction (fecundity) at times of spawning, of an individual as it is exposed to constant or hourly fluctuating dissolved oxygen (DO) concentrations. The model was applied to seven experiments involving fish and shrimp that included constant and fluctuating DO exposures, with constant exposures used for parameter estimation and the model then used to simulate the growth, reproduction, and survival in the fluctuating treatments. Cumulative effects on growth, reproduction, and survival were predicted well by the model, but the model did not replay the observed episodic low survival days. Further investigation should involve the role of acclimation, possible inclusion of repair effects in reproduction and survival, and the sensitivity of model predictions to the shape of the immediate effects function. Additional testing of the model with other taxa, different patterns of fluctuating exposures, and different stressors is needed to determine the model's generality and robustness.

  17. Time Series Stream Temperature And Dissolved Oxygen Modeling In The Lower Flint River Basin

    Science.gov (United States)

    Li, G.; Jackson, C. R.

    2004-12-01

    The tributaries of the Lower Flint River Basin (LFRB) are incised into the upper Floridan semi-confined limestone aquifer, and thus seepage of relatively old groundwater sustains baseflows and provides some control over temperature and dissolved oxygen fluctuations. This hydrologic and geologic setting creates aquatic habitat that is unique in the state of Georgia. Groundwater withdrawals and possible water supply reservoirs threaten to exacerbate low flow conditions during summer droughts, which may force negative impacts to stream temperature and dissolved oxygen (DO). To evaluate the possible effects of human modifications to stream habitat, summer time series (in 15 min interval) of stream temperature and DO were monitored over the last three years along these streams, and a Continuously Stirred Tank Reactor (CSTR) model was developed and calibrated with these data. The driving forces of the diel trends and the overall levels of stream temperature and DO were identified by this model. Simulations were conducted with assumed managed flow conditions to illustrate potential effects of various stream flow regimes on stream temperature and DO time series. The goal of this research is to provide an accurate simulation tool to guide management decisions.

  18. Influence of Temperature and Dissolved Oxygen on Nitrogen and Phosphorus Removal of Integrated Bioreactor

    Directory of Open Access Journals (Sweden)

    Chunying Wu

    2017-06-01

    Full Text Available An integrated biological membrane sewage treatment device has been designed based on the mechanism of microorganism nitrogen and phosphorus removal and the influence of temperature and dissolved oxygen on nitrogen and phosphorus removal of integrated bioreactor with adoption of this sewage treatment device. The research results shows that the optimal temperature range of microorganism nitrogen and phosphorus removal is 20-30 °C, and the effluent COD removal rate within this range maintains at over 90%; NH4^+-N removal rate is between 95% and 97%. TN removal rate is approximately 81%. In practical production, the internal temperature environment of the sewage reactor should be maintained at above 15 °C, to decrease the inhibition of low-temperature environment on growth and reaction speed of nitrobacteria. In various concentrations of DO in the reactor, there is little change in the effluent COD concentration and effluent COD concentration is influenced by temperature. With the increasing of DO concentration, both effluent TN and TP concentrations present changing features of initially decreasing then increasing. The analysis of the influence of comprehensive dissolved oxygen on microorganism nitrogen and phosphorus removal reveals that when the concentration of DO maintains within the range of 1.0-1.5 mg/L, the sewage purification system can attain a higher nitrogen and phosphorus removal effect.

  19. Time dependent intrinsic correlation analysis of temperature and dissolved oxygen time series using empirical mode decomposition

    CERN Document Server

    Huang, Y X

    2014-01-01

    In the marine environment, many fields have fluctuations over a large range of different spatial and temporal scales. These quantities can be nonlinear \\red{and} non-stationary, and often interact with each other. A good method to study the multiple scale dynamics of such time series, and their correlations, is needed. In this paper an application of an empirical mode decomposition based time dependent intrinsic correlation, \\red{of} two coastal oceanic time series, temperature and dissolved oxygen (saturation percentage) is presented. The two time series are recorded every 20 minutes \\red{for} 7 years, from 2004 to 2011. The application of the Empirical Mode Decomposition on such time series is illustrated, and the power spectra of the time series are estimated using the Hilbert transform (Hilbert spectral analysis). Power-law regimes are found with slopes of 1.33 for dissolved oxygen and 1.68 for temperature at high frequencies (between 1.2 and 12 hours) \\red{with} both close to 1.9 for lower frequencies (t...

  20. The oxygen isotope composition of dissolved anthropogenic phosphates: a new tool for eutrophication research?

    Science.gov (United States)

    Gruau, Gérard; Legeas, Michèle; Riou, Christine; Gallacier, Eve; Martineau, François; Hénin, O

    2005-01-01

    High-precision oxygen isotope analyses were carried out on dissolved phosphate extracted from discharge waters from three wastewater treatment plants (WTP) located in western France, as well as on the different phosphate-based fertilizers applied by farmers in the same region. Measured delta(18)O values of phosphate from chemical fertilizers range from 19.6 to 23.1 per thousand, while those of phosphate from WTP discharge waters are more tightly grouped between 17.7 and 18.1 per thousand. The variability in delta(18)O values of phosphate fertilizers is attributed to oxygen isotope variations of the phosphorite deposits from which France's fertilizers are manufactured. The significance of the delta(18)O values of phosphate from WTP discharge waters is less straightforward. At present, it is not clear whether these values are primary isotopic compositions corresponding, e.g., to the oxygen isotope composition of phosphate builders included in detergents (delta(18)O(P)=17.9 per thousand), or represent secondary values reflecting biological recycling of the phosphate in equilibrium with ambient WTP water The restricted difference in isotopic composition obtained between phosphate from fertilizers and phosphate from WTP discharge waters (isotopic variability observed in both end-members (>/=1.5 per thousand), cast doubt about the possibility that the oxygen isotope composition could serve as a tracer for the source of anthropogenic phosphates in waters.

  1. Under-ice eddy covariance flux measurements of heat, salt, momentum, and dissolved oxygen in an artificial sea ice pool

    DEFF Research Database (Denmark)

    Else, B. G T; Rysgaard, S.; Attard, K.

    2015-01-01

    Turbulent exchanges under sea ice play a controlling role in ice mass balance, ice drift, biogeochemistry, and mixed layer modification. In this study, we examined the potential to measure under-ice turbulent exchanges of heat, salt, momentum, and dissolved oxygen using eddy covariance...... as ice grew from 5 to 25 cm thick. Heat, momentum, and dissolved oxygen fluxes were all successfully derived. Quantification of salt fluxes was unsuccessful due to noise in the conductivity sensor, a problem which appears to be resolved in a subsequent version of the instrument. Heat fluxes during...... initial ice growth were directed upward at 10 to 25 W m−2. Dissolved oxygen fluxes were directed downward at rates of 5 to 50mmolm−2 d−1 throughout the experiment, at times exceeding the expected amount of oxygen rejected with the brine during ice growth. Bubble formation and dissolution was identified...

  2. Simulation of oil bioremediation in a tidally influenced beach: Spatiotemporal evolution of nutrient and dissolved oxygen

    Science.gov (United States)

    Geng, Xiaolong; Pan, Zhong; Boufadel, Michel C.; Ozgokmen, Tamay; Lee, Kenneth; Zhao, Lin

    2016-04-01

    Numerical experiments of oil bioremediation of tidally influenced beach were simulated using the model BIOMARUN. Nutrient and dissolved oxygen were assumed present in a solution applied on the exposed beach face, and the concentration of these amendments was tracked throughout the beach for up to 6 months. It was found that, in comparison to natural attenuation, bioremediation increased the removal efficiency by 76% and 65% for alkanes and aromatics, respectively. Increasing the nutrient concentration in the applied solution did not always enhance biodegradation as oxygen became limiting even when the beach was originally oxygen-rich. Therefore, replenishment of oxygen to oil-contaminated zone was also essential. Stimulation of oil biodegradation was more evident in the upper and midintertidal zone of the beach, and less in the lower intertidal zone. This was due to reduced nutrient and oxygen replenishment, as very little of the amendment solution reached that zone. It was found that under continual application, most of the oil biodegraded within 2 months, while it persisted for 6 months under natural conditions. While the difference in duration suggests minimal long-term effects, there are situations where the beach would need to be cleaned for major ecological functions, such as temporary nesting or feeding for migratory birds. Biochemical retention time map (BRTM) showed that the duration of solution application was dependent upon the stimulated oil biodegradation rate. By contrast, the application rate of the amendment solution was dependent upon the subsurface extent of the oil-contaminated zone. Delivery of nutrient and oxygen into coastal beach involved complex interaction among amendment solution, groundwater, and seawater. Therefore, approaches that ignore the hydrodynamics due to tide are unlikely to provide the optimal solutions for shoreline bioremediation.

  3. Effects of bottom water dissolved oxygen variability on copper and lead fractionation in the sediments across the oxygen minimum zone, western continental margin of India.

    Science.gov (United States)

    Chakraborty, Parthasarathi; Chakraborty, Sucharita; Jayachandran, Saranya; Madan, Ritu; Sarkar, Arindam; Linsy, P; Nath, B Nagender

    2016-10-01

    This study describes the effect of varying bottom-water oxygen concentration on geochemical fractionation (operational speciation) of Cu and Pb in the underneath sediments across the oxygen minimum zone (Arabian Sea) in the west coast of India. Both, Cu and Pb were redistributed among the different binding phases of the sediments with changing dissolved oxygen level (from oxic to hypoxic and close to suboxic) in the bottom water. The average lability of Cu-sediment complexes gradually decreased (i.e., stability increased) with the decreasing dissolved oxygen concentrations of the bottom water. Decreasing bottom-water oxygen concentration increased Cu association with sedimentary organic matter. However, Pb association with Fe/Mn-oxyhydroxide phases in the sediments gradually decreased with the decreasing dissolved oxygen concentration of the overlying bottom water (due to dissolution of Fe/Mn oxyhydroxide phase). The lability of Pb-sediment complexes increased with the decreasing bottom-water oxygen concentration. This study suggests that bottom-water oxygen concentration is one of the key factors governing stability and lability of Cu and Pb complexes in the underneath sediment. Sedimentary organic matter and Fe/Mn oxyhydroxide binding phases were the major hosting phases for Cu and Pb respectively in the study area. Increasing lability of Pb-complexes in bottom sediments may lead to positive benthic fluxes of Pb at low oxygen environment. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Responses of epibenthic and nektonic macroinvertebrate communities to a gradient of fish size in ponds

    Directory of Open Access Journals (Sweden)

    Marek Nieoczym

    2014-07-01

    Full Text Available Size relationships between fish and organisms from adjacent trophic levels are crucial for predicting the structure and dynamics of aquatic ecosystems. We compared macroinvertebrate communities along a fish-size gradient created by separate stocking of three age cohorts of common carp Cyprinus carpio in semi-natural ponds. The specific size range of fish (small, medium and large corresponding to fish age in ponds was the factor most strongly associated with macroinvertebrate composition. The other significant habitat variables were dissolved oxygen concentration in the water and submerged vegetation abundance in the open-water zone. Among the most numerous taxa in the ponds, relative abundances of Hirudinea, Gastropoda, Odonata and Coleoptera were larger in the presence of small-sized than of larger-sized carp. However, fish size effect was not linear, in that macroinvertebrate assemblages were less similar between ponds containing medium- vs large-sized fish than between ponds with small- vs large-sized fish. The dissimilarity patterns were mainly determined by disparities in abundance of Corixidae, which unlike other taxa common in the ponds occurred in the greatest numbers in the presence of large-sized carp. Macroinvertebrate diversity was greatest in ponds with small-sized fish and was positively related to emergent macrophyte cover. Enhancement of emergent vegetation is recommended as the most effective management strategy to buffer adverse impacts of fish on macroinvertebrates. If fish are present in the system, assessment of the size structure of fish populations can be advantageous in unravelling the essential processes driving the variation in pond communities.

  5. Evaluating the effect of dissolved oxygen on simultaneous nitrification and denitrification in polyurethane foam contact oxidation reactors.

    Science.gov (United States)

    Tan, Chong; Ma, Fang; Li, Ang; Qiu, Shan; Li, Jianzheng

    2013-03-01

    The effects of dissolved oxygen on simultaneous nitrification and denitrification were evaluated in polyurethane foam contact oxidation reactors in a municipal wastewater treatment process. It was observed that nitrate could be removed at low dissolved oxygen levels, but the removal rate was gradually reduced as the dissolved oxygen concentration increased to a higher level of 6.0 mg/L. Nitrogen removal remained optimal within the dissolved oxygen range of 0.5 to 1.0 mg/L. Denaturing gradient gel electrophoresis (DGGE) analysis revealed that the diversity of the microbial community changed accompanying dissolved oxygen values of 0.5 to 1.0 mg/L, 2.5 to 3.5 mg/L, 6.0 to 6.5 mg/L, and 10.0 to 12.0 mg/L, in turn, which was supported by the Shannon-Wiener index of 1.56, 1.71, 1.43, and 1.56, accordingly. Both DGGE profiling and phylogenetic analysis confirmed that the nitrifiers in reactors that are responsible for nitrification during the experiment include Nitrosospira sp., Nitrosomonas sp., and Nitrospira sp.

  6. Disentangling dissolved oxygen sources in shallow riparian groundwater by stable isotope analysis

    Science.gov (United States)

    Mader, Michael; Porst, David; Schmidt, Christian; van Geldern, Robert; Barth, Johannes

    2017-04-01

    Dissolved oxygen (DO) is one of the strongest oxidation agents in aquatic environments. Besides gas-water-exchange, mixing and mineral oxidation, it is a key player in fundamental biogeochemical processes such as respiration and photosynthesis. These processes also systematically influence stable isotope ratios of DO and of dissolved inorganic carbon (DIC). Simultaneous measurements of DO and DIC concentrations in conjunction with their stable isotope ratios (δ18ODO and δ13CDIC) can thus provide useful tools to quantify oxygen and carbon sources and sinks in natural waters. This study focused on the Selke River in the Harz Mountains (Germany) with steep DO gradients between the stream water and the shallow, adjacent groundwater and associated stable isotope shifts. δ13CDIC values decreased from -13 ‰ to -18 ‰ versus the Vienna Pee Dee Belemnite standard (VPDB) from May to November 2016 and indicated the dominant influence of microbial respiration on the observed DO gradients. With such respiration dominance, we have expected a simultaneous enrichment of δ18ODOto values higher than the one of atmospheric O2 (+23.9 ‰ versus Vienna Standard Mean Ocean Water standard - VSMOW). However, our measurements revealed anomalously low δ18ODO values between +22 ‰ and +18 ‰ versus VSMOW for the same time period. These δ18ODO values were lower than those found in the river. Latter were close to equilibrium with the atmosphere (24.9 ‰ versus VSMOW). The observed δ18ODO ratios in the shallow groundwater can be explained with DO from the river that is subject to fractionation by microbial respiration with a typical fractionation factor (αr) of 0.995. In addition, mass balances revealed that this oxygen pool receives contributions of up to 25 % by diffused oxygen from the vadose zone. Consequently, isotope shifts by respiration and admixture with surface water are masked by diffusion effects that result in a decoupling of carbon and oxygen isotope systematics in

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

    Science.gov (United States)

    Goh, Fernie; Sambanis, Athanassios

    2011-09-01

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

  8. Methods and Best Practice to Intercompare Dissolved Oxygen Sensors and Fluorometers/Turbidimeters for Oceanographic Applications.

    Science.gov (United States)

    Pensieri, Sara; Bozzano, Roberto; Schiano, M Elisabetta; Ntoumas, Manolis; Potiris, Emmanouil; Frangoulis, Constantin; Podaras, Dimitrios; Petihakis, George

    2016-01-01

    In European seas, ocean monitoring strategies in terms of key parameters, space and time scale vary widely for a range of technical and economic reasons. Nonetheless, the growing interest in the ocean interior promotes the investigation of processes such as oxygen consumption, primary productivity and ocean acidity requiring that close attention is paid to the instruments in terms of measurement setup, configuration, calibration, maintenance procedures and quality assessment. To this aim, two separate hardware and software tools were developed in order to test and simultaneously intercompare several oxygen probes and fluorometers/turbidimeters, respectively in the same environmental conditions, with a configuration as close as possible to real in-situ deployment. The chamber designed to perform chlorophyll-a and turbidity tests allowed for the simultaneous acquisition of analogue and digital signals of several sensors at the same time, so it was sufficiently compact to be used in both laboratory and onboard vessels. Methodologies and best practice committed to the intercomparison of dissolved oxygen sensors and fluorometers/turbidimeters have been used, which aid in the promotion of interoperability to access key infrastructures, such as ocean observatories and calibration facilities. Results from laboratory tests as well as field tests in the Mediterranean Sea are presented.

  9. Methods and Best Practice to Intercompare Dissolved Oxygen Sensors and Fluorometers/Turbidimeters for Oceanographic Applications

    Directory of Open Access Journals (Sweden)

    Sara Pensieri

    2016-05-01

    Full Text Available In European seas, ocean monitoring strategies in terms of key parameters, space and time scale vary widely for a range of technical and economic reasons. Nonetheless, the growing interest in the ocean interior promotes the investigation of processes such as oxygen consumption, primary productivity and ocean acidity requiring that close attention is paid to the instruments in terms of measurement setup, configuration, calibration, maintenance procedures and quality assessment. To this aim, two separate hardware and software tools were developed in order to test and simultaneously intercompare several oxygen probes and fluorometers/turbidimeters, respectively in the same environmental conditions, with a configuration as close as possible to real in-situ deployment. The chamber designed to perform chlorophyll-a and turbidity tests allowed for the simultaneous acquisition of analogue and digital signals of several sensors at the same time, so it was sufficiently compact to be used in both laboratory and onboard vessels. Methodologies and best practice committed to the intercomparison of dissolved oxygen sensors and fluorometers/turbidimeters have been used, which aid in the promotion of interoperability to access key infrastructures, such as ocean observatories and calibration facilities. Results from laboratory tests as well as field tests in the Mediterranean Sea are presented.

  10. The role of reactive oxygen species in the degradation of lignin derived dissolved organic matter

    Science.gov (United States)

    Waggoner, Derek C.; Wozniak, Andrew S.; Cory, Rose M.; Hatcher, Patrick G.

    2017-07-01

    Evidence suggests that reactive oxygen species (ROS) are important in transforming the chemical composition of the large pool of terrestrially-derived dissolved organic matter (DOM) exported from land to water annually. However, due to the challenges inherent in isolating the effects of individual ROS on DOM composition, the role of ROS in the photochemical alteration of DOM remains poorly characterized. In this work, terrestrial DOM was independently exposed to singlet oxygen (1O2), and superoxide (O2-rad under controlled laboratory conditions). Using ultra-high resolution mass spectrometry to track molecular level alterations of DOM by ROS, these findings suggest exposure to 1O2 (generated using Rose Bengal and visible light) removed formulas with an O/C > 0.3, and primarily resulted in DOM comprised of formulas with higher oxygen content, while O2-rad exposure (from KO2 in DMSO) removed formulas with O/C 1.5). Comparison of DOM altered by ROS in this study to riverine and coastal DOM showed that (20-80%) overlap in formulas, providing evidence for the role of ROS in shaping the composition of DOM exported from rivers to oceans.

  11. Identification and control of dissolved oxygen in hybridoma cell culture in a shear sensitive environment.

    Science.gov (United States)

    Simon, L; Karim, M N

    2001-01-01

    The productivity of mammalian cells can be enhanced by facilitating adequate oxygen transfer into the cultivation medium. However, current methods of controlling dissolved oxygen (DO) fail to account for alterations in medium composition during the course of the fermentation. These changes, which directly affect gas solubility and overall mass transfer coefficient, may be significant and deteriorate controller's performance in the long run. In this paper, the applications of Generalized Predictive Controllers (GPC) to DO control were investigated in a shear sensitive environment and compared to PID and Model Predictive Controllers (MPC). Input and output data for system identification were initially generated by varying the composition of oxygen fed into the bioreactor from 0 to 0.21 mol % while keeping the total inlet gas flow rate at 8.75 vvm. The process was identified using an AutoRegressive model with eXogeneous inputs (ARX) model and tested on different data sets. The model parameters were then correlated with the overall mass transfer coefficients. In simulation tests, the output of the PID controller switched from minimum to maximum values while more continuous control signals were obtained with the MPC and GPC controllers. When tested in a cell-free medium, all three controllers were able to track setpoint changes with some chattering observed in the control signals. The GPC outperformed the MPC and PID controllers when applied to the cultivation of hybridoma cells.

  12. Tilapia cage culture and the dissolved oxygen trends in Sampaloc Lake, the Philippines.

    Science.gov (United States)

    Santiago, A E; Arcilla, R P

    1993-02-01

    The 28-hectare tilapia cage culture that occupied the 104-hectare Sampaloc Lake, a crater lake, shifted to intensive method in 1986 when tilapia growth slowed done at the beginning of 1982. Thus, commercial feeds became the main source of allochthonous organic matter in the lake. Total feeds given annually for the 28-hectare cage culture at 3 croppings per year amounted to 5250 tons. At feed conversion ratio of 1 : 2 a significant portion of the feeds given ended as organic wastes in the lake. In 1988, tilapia cage operators began experiencing their worst occurrences of fishkill, worth millions of pesos. An assessment of the dissolved oxygen condition of Sampaloc lake in late 1989, 1990 and mid-1991 showed ominous trends which might adversely affect the use of Sampaloc lake for fishery.

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

    Science.gov (United States)

    Cheng, Xiangju; Chen, Xuewei

    2013-05-01

    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.

  14. Dissolved-oxygen and algal conditions in selected locations of the Willamette River basin, Oregon

    Science.gov (United States)

    Rinella, F.A.; McKenzie, S.W.; Wille, S.A.

    1981-01-01

    During July and August 1978, the U.S. Geological Survey, in cooperation with the Oregon Department of Enviromental Quality, made three intensive river-quality dissolved-oxygen studies in the upper Willamette River basin. Two studies were made on the upper Willamette River and one was made on the Santiam River, a Willamette River tributary. Nitrification, occurring in both the upper Willamette and South Santiam Rivers, accounted for about 62% and 92% of the DO sag in the rivers, respectively. Rates of nitrification were found to be dependent on ammonia concentrations in the rivers. Periphyton and phytoplankton algal samples were collected on the main stem Willamette River and selected tributaries during August 1978. Diatoms were the dominant group in both the periphyton and phytoplankton samples. The most common diatom genera were Melosira, Stephanodiscus, Cymbella, Achnanthes, and Nitzschia. Comparisons with historical data indicate no significant difference from previous years in the total abundance or diversity of the algae. (USGS)

  15. Forest clearfelling effects on dissolved oxygen and metabolism in peatland streams.

    Science.gov (United States)

    O'Driscoll, Connie; O'Connor, Mark; Asam, Zaki-Ul-Zaman; de Eyto, Elvira; Brown, Lee E; Xiao, Liwen

    2016-01-15

    Peatlands cover ∼3% of the world's landmass and large expanses have been altered significantly as a consequence of land use change. Forestry activities are a key pressure on these catchments increasing suspended sediment and nutrient export to receiving waters. The aim of this study was to investigate stream dissolved oxygen (DO) and metabolic activity response following clearfelling of a 39-year-old lodgepole pine and Sitka spruce forestry in an upland peat catchment. Significant effects of clearfelling on water temperature, flows, DO and stream metabolic (photosynthesis, respiration) rates were revealed. Stream temperature and discharge significantly increased in the study stream following clearfelling. Instream ecosystem respiration increased significantly following clearfelling, indicating an increase in the net consumption of organic carbon.

  16. Dissolved oxygen detection by galvanic displacement-induced graphene/silver nanocomposite

    Indian Academy of Sciences (India)

    Li Fu; Yuhong Zheng; Zhuxian Fu; Aiwu Wang; Wen Cai

    2015-06-01

    This paper proposed a simple, efficient and sensitive electrochemical sensor for dissolved oxygen (DO) detection based on a galvanic displacement synthesized reduced graphene oxide–silver nanoparticles (RGO/Ag) composite modified grassy carbon electrode (GCE). The synthesized RGO/Ag nanocomposite was characterized by UV–vis spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicate the graphene oxide (GO) has been successfully reduced during the galvanic displacement process and the average size of Ag nanoparticle is 52 nm. The RGO/Ag nanocomposite-modified GCE showed a significant enhancement of DO detection compared with bare and RGO-modified GCEs. Moreover, the proposed DO sensor also exhibited an excellent repeatability, reproducibility and anti-interference ability

  17. Contribution of Dissolved Oxygen to Methylene Blue Decomposition by Hybrid Advanced Oxidation Processes System

    Directory of Open Access Journals (Sweden)

    Heon Lee

    2012-01-01

    Full Text Available Experimental results of photocatalysis under high dissolved oxygen (DO concentration conditions are reported. Methylene blue was used as the organic pollutant to be degraded by a novel microwave/UV/DO/TiO2 photocatalyst hybrid system. The degradation rate increased with TiO2 nanoparticle dosages and DO concentration. However, inhibition of photocatalysis due to bubbles produced by DO generator was also observed. When the DO generator was used to increase the DO concentration in the pollutant solution treated by the microwave-assisted UV-TiO2 photocatalysis, the decomposition rate constant was highest among all the experimental conditions tested in this study. This result demonstrated that high concentration of DO can enhance the photocatalytic reaction rate by causing a synergistic effect of constituent techniques.

  18. Removal of dissolved oxygen from water using a Pd-resin based catalytic reactor

    Institute of Scientific and Technical Information of China (English)

    Wenxin SHI; Chongwei CUI; Liye ZHAO; Shuili YU; Xia YUN

    2009-01-01

    The removal of dissolved oxygen (DO) from water was studied experimentally in a Pd-resin base catalyst reactor using purified hydrogen gas as a reducing agent. The effects of various operating conditions, such as hydrogen and water flow rates, height of the catalytic resin bed, temperature, pH value and nan time, on the removal of DO, had been studied extensively. The results shows that DO could be removed by the reactor from ppm to ppb levels at ambient temperature. Increases of temperature, H2gas rate and the height of the catalytic resin were helpful to improve the DO removal rate. The change of pH value fom 4 to 12 resulted in no effect on DO removal. Reaction time was the key factor to control the DO removal efficiency. Only when the reaction time was longer than 2.3 minutes under the experimental conditions, could a very low DO level be achieved.

  19. [Effect of dissolved oxygen on microbial community in simultaneous removal of carbon, nitrogen and sulfur process].

    Science.gov (United States)

    Yu, Hao; Chen, Chuan; Zhang, Li; Wang, Ai-Jie

    2013-06-01

    In order to investigate the effect of dissolved oxygen (DO) on microbial community in simultaneous removal of carbon, nitrogen and sulfur process and reveal the mechanism of high elemental sulfur conversion rate under aerobic condition, GeoChip was employed to characterize the structure of microbial community. The results indicated that the microbial community structure significantly changed with different aerobic conditions (P bacteria (SRB) with the changing DO. The relative abundance of sox gene showed significant difference between aeration rate of 20 mL x min(-1) and aeration rate of 0 mL x min(-1), which might suggest that the activity of sulfur-oxidizing bacteria (SOB) was obviously improved by DO. Moreover, cluster analysis of sox gene confirmed this suggestion, with higher signal intensity found in numbers of probes derived from SOB under such aerobic conditions. Overall, the results revealed a positive effect of micro-aerobic conditions on the simultaneous removal of carbon, nitrogen and sulfur process.

  20. Dissolved oxygen prediction using a possibility theory based fuzzy neural network

    Science.gov (United States)

    Khan, Usman T.; Valeo, Caterina

    2016-06-01

    A new fuzzy neural network method to predict minimum dissolved oxygen (DO) concentration in a highly urbanised riverine environment (in Calgary, Canada) is proposed. The method uses abiotic factors (non-living, physical and chemical attributes) as inputs to the model, since the physical mechanisms governing DO in the river are largely unknown. A new two-step method to construct fuzzy numbers using observations is proposed. Then an existing fuzzy neural network is modified to account for fuzzy number inputs and also uses possibility theory based intervals to train the network. Results demonstrate that the method is particularly well suited to predicting low DO events in the Bow River. Model performance is compared with a fuzzy neural network with crisp inputs, as well as with a traditional neural network. Model output and a defuzzification technique are used to estimate the risk of low DO so that water resource managers can implement strategies to prevent the occurrence of low DO.

  1. Modelling geochemical and microbial consumption of dissolved oxygen after backfilling a high level radiactive waste repository.

    Science.gov (United States)

    Yang, Changbing; Samper, Javier; Molinero, Jorge; Bonilla, Mercedes

    2007-08-15

    Dissolved oxygen (DO) left in the voids of buffer and backfill materials of a deep geological high level radioactive waste (HLW) repository could cause canister corrosion. Available data from laboratory and in situ experiments indicate that microbes play a substantial role in controlling redox conditions near a HLW repository. This paper presents the application of a coupled hydro-bio-geochemical model to evaluate geochemical and microbial consumption of DO in bentonite porewater after backfilling of a HLW repository designed according to the Swedish reference concept. In addition to geochemical reactions, the model accounts for dissolved organic carbon (DOC) respiration and methane oxidation. Parameters for microbial processes were derived from calibration of the REX in situ experiment carried out at the Aspö underground laboratory. The role of geochemical and microbial processes in consuming DO is evaluated for several scenarios. Numerical results show that both geochemical and microbial processes are relevant for DO consumption. However, the time needed to consume the DO trapped in the bentonite buffer decreases dramatically from several hundreds of years when only geochemical processes are considered to a few weeks when both geochemical reactions and microbially-mediated DOC respiration and methane oxidation are taken into account simultaneously.

  2. Variability of dissolved oxygen over the last millennium and the 21st century in CESM

    Science.gov (United States)

    Hameau, Angélique; Joos, Fortunat; Mignot, Juliette; Keller, Kathrin

    2017-04-01

    The earth system models simulate a depletion of the oxygen content in the ocean under global warming conditions (Cocco et al. 2012, Frölicher et al. 2009). The response to external forcing and mechanism underlying this evolution are not completely understood. Physical and biogeochemical processes are involved and tangled up to each other leading to a decrease of the global mean concentration of O2 in the ocean with the increase of the ocean temperature. This result is supported by experimental and observational studies in Atlantic and Pacific oceans (Stramma et al. 2008, Brandt et al. 2010). Here, we study the evolution of dissolved oxygen in a climate simulation of the Community Earth System Model (CESM) covering the last millennium and the 21st century. This long period allows us to identify the natural variability of the climate in this system, and therefore analyse the time of emergence (ToE) of the anthropogenic signal under the RCP8.5 scenario. Based on Keller et al. 2014, the time of emergence is defined as the point in time when the trend signal reaches twice the standard deviation of the signal during the preindustrial period (1000 years). The ToE of oxygen and of temperature present an offset. We show that the anthropogenic emissions are seen in a first hand by the oxygen and only then by the temperature. We also look at the OMZ response. The oxygen minimum zones result from a combination of weak ventilation and sustained respiration by the microorgamisms. With a global decrease of the oceanic oxygen content, the OMZ may therefore expand impacting the environment of marine species. But this statement is questioned by Deutsch et al 2014, who relates the variations of Pacific OMZ to the variations of the tropical Walker circulation. The CESM climate model predicts an expansion of the oxygen low zones and the emergence of new ones over the last century. Magnitude and timescales of these responses will be discussed and compared to natural variability.

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

    Science.gov (United States)

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

    2014-12-01

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

  4. Non-Linear Time Series Analysis of Dissolved Oxygen in Five Diverse Aquatic Environments

    Science.gov (United States)

    Simpson, K. E.; Barton, C. C.; Smigelski, J. R.; Tebbens, S. F.

    2008-12-01

    Temporal variations in the concentration of Dissolved oxygen (DO) can create catastrophic conditions for organisms that rely on aerobic metabolic processes for survival. Dissolved oxygen (DO) is an aquatic parameter whose concentration is controlled by physical, biological, and chemical processes. The concentration of DO in an aquatic system is important to organisms that rely on aerobic metabolic processes for survival. A power-spectral-density analysis of time series of DO concentration is used to quantify persistence (the degree of internal correlation) over durations of 3 months to 19 years. The interval between data points was either 15 minutes or one hour. The data are from ten different water bodies throughout the United States. Four of these sites are large, slow moving bodies of water including three estuaries: Chesapeake Bay (Virginia), Winyah Bay (North Carolina) and Elkhorn Slough (California); and one reservoir: the Cheney Reservoir in Kansas. The other six sites are small, fast moving water bodies. They included four rivers: Christina River (Delaware), St. Croix River (Maine), Ramapo River (New Jersey), and Passaic River, New Jersey; one stream: Green Pond Brook (New Jersey); and one man-made channel: Reynolds Channel (New York). The analysis quantifies persistence as the power scaling exponent (β), which for all ten water bodies β ranges between 1.2 and 1.6 meaning that the signal is persistent and non-stationary. Rivers and streams, exhibit higher β-values of 1.5 < β<1.6 (greater persistence) than estuaries and lakes, which have β-values of 1.2< β <1.4t.

  5. Relationship between ecosystem respiration and aeration constant in open channel dissolved oxygen analysis

    Science.gov (United States)

    Parker, S. J.; Butler, A. P.; Heppell, C. M.

    2015-12-01

    Using the open channel diel method of Odum (1956) and the night-time regression method (Hornberger and Kelly, 1985), we analysed a time series of dissolved oxygen (DO) in two slow flowing streams for a two month period in summer 2014 and obtained values for ecosystem respiration and the aeration constant for each day in the period. We then used the standard dissolved oxygen lumped model to generate a DO time series behaviour for one of those rivers selecting respiration and aeration parameters by randomly sampling from the values obtained from the data. Two synthetic time series were created, one where respiration and aeration were independent of temperature and a second where respiration and aeration were affected by temperature according to the modified Arrhenius relationship. With these two synthetic time series, we again recovered the respiration and aeration input parameters using the night- time regression method and compared those recovered parameters with the input parameters. Because the simulations were conducted with parameters that were known, the values recovered using the night-time regression method (i.e post-simulation) could be compared with parameters driving the simulation (i.e. pre-simulation input values). For values based on data, we found a strong correlation between the aeration constant and respiration for both rivers. For the synthetic time series, no such correlation was found, either with the temperature independent or temperature dependent time series. The night-time regression method also recovered perfectly the input parameters, so the correlation was not brought about as a result of implementing the method itself. We are currently investigating the cause of the correlation.

  6. Mechanism of the cathodic process coupled to the oxidation of iron monosulfide by dissolved oxygen.

    Science.gov (United States)

    Duinea, Mădălina I; Costas, Andreea; Baibarac, Mihaela; Chiriță, Paul

    2016-04-01

    This study investigated the mechanism of iron monosulfide (FeS) oxidation by dissolved oxygen (O2(aq)). Synthetic FeS was reacted with O2(aq) for 6days and at 25°C. We have characterized the initial and reacted FeS surface using Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM/EDX) analysis, Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). It was found that during the aqueous oxidation of FeS new solid phases (disulfide, polysulfide, elemental sulfur, ferric oxyhydroxides and Fe3O4) develop on the mineral surface. The results of potentiodynamic polarization experiments show that after 2days of FeS electrode immersion in oxygen bearing solution (OBS) at initial pH 5.1 and 25°C the modulus of cathodic Tafel slopes dramatically decreases, from 393mV/dec to 86mV/dec. This decrease is ascribed to the change of the mechanism of electron transfer from cathodic sites to O2 (mechanism of cathodic process). The oxidation current densities (jox) indicate that mineral oxidative dissolution is not inhibited by pH increase up to 6.7. Another conclusion, which emerges from the analysis of jox, is that the dissolved Fe(3+) does not intermediate the aqueous oxidation of FeS. The results of electrochemical impedance spectroscopy (EIS) show that after 2days of contact between electrode and OBS the properties of FeS/water interface change. From the analysis of the EIS, FTIR spectroscopy, Raman spectroscopy and SEM/EDX data we can conclude that the change of FeS/water interface properties accompanies the formation of new solid phases on the mineral surface. The new characteristics of the surface layer and FeS/water interface do not cause the inhibition of mineral oxidation.

  7. Hyperosmotic Agents and Antibiotics Affect Dissolved Oxygen and pH Concentration Gradients in Staphylococcus aureus Biofilms.

    Science.gov (United States)

    Kiamco, Mia Mae; Atci, Erhan; Mohamed, Abdelrhman; Call, Douglas R; Beyenal, Haluk

    2017-03-15

    Biofilms on wound surfaces are treated topically with hyperosmotic agents, such as medical-grade honey and cadexomer iodine; in some cases, these treatments are combined with antibiotics. Tissue repair requires oxygen, and a low pH is conducive to oxygen release from red blood cells and epithelialization. We investigated the variation of dissolved oxygen concentration and pH with biofilm depth and the variation in oxygen consumption rates when biofilms are challenged with medical-grade honey or cadexomer iodine combined with vancomycin or ciprofloxacin. Dissolved oxygen and pH depth profiles in Staphylococcus aureus biofilms were measured using microelectrodes. The presence of cadexomer iodine with vancomycin or ciprofloxacin on the surface of the biofilm permitted a measurable concentration of oxygen at greater biofilm depths (101.6 ± 27.3 μm, P = 0.02; and 155.5 ± 27.9 μm, P = 0.016, respectively) than in untreated controls (30.1 μm). Decreases in pH of ∼0.6 and ∼0.4 units were observed in biofilms challenged with medical-grade honey alone and combined with ciprofloxacin, respectively (P dissolved oxygen concentration and penetration depth into the biofilm, while medical-grade honey was associated with a lower pH; not all treatments established a bactericidal effect in the time frame used in the experiments.IMPORTANCE Reports about using hyperosmotic agents and antibiotics against wound biofilms focus mostly on killing bacteria, but the results of these treatments should additionally be considered in the context of how they affect physiologically important parameters, such as oxygen concentration and pH. We confirmed that the combination of a hyperosmotic agent and an antibiotic results in greater dissolved oxygen and reduced pH within an S. aureus biofilm. Copyright © 2017 American Society for Microbiology.

  8. Hyporheic flow and dissolved oxygen distribution in fish nests: The effects of open channel velocity, permeability patterns, and groundwater upwelling

    Science.gov (United States)

    Cardenas, M. Bayani; Ford, Aimee E.; Kaufman, Matthew H.; Kessler, Adam J.; Cook, Perran L. M.

    2016-12-01

    Many fish lay their eggs in nests, or redds, which they construct in sediment. The viability of eggs depends on many factors, particularly their oxygenation. Because dissolved oxygen is typically saturated within the stream channel, the dissolved oxygen distribution within the redd depends on whether or not hyporheic flow and transport occur within the sediment. We conducted a series of flume and numerical flow and age transport modeling experiments with the aim of understanding the effects of salmonid redds on the hyporheic transport of young oxygenated water. Hyporheic flow was visualized directly through dye injections. Dissolved oxygen throughout the fish nest was measured using a planar optode. Experiments were conducted at various open channel flow velocities in order to understand their effect on dissolved oxygen, and computational simulations considered various sediment textures and ambient groundwater upwelling rates to add process-level insight. We found that, as also shown by previous studies, the redd topography induces multiscale hyporheic flow that effectively flushes the egg pocket location with younger presumably oxygenated water; older water upwells and forms anoxic zones. This pattern persists even at the lowest channel flow rates and at small upwelling velocities of older ambient groundwater which splits the multiscale hyporheic flow cells into isolated pockets. Large groundwater upwelling rates can shut down all the hyporheic flushing. The relatively coarse texture of the redd further promotes hyporheic flushing of the redd sediment with oxygenated water. Thus, redd morphology and sediment texture optimally combine to induce hyporheic exchange flow that delivers young oxygenated water to the egg pocket.

  9. INVESTIGATION OF DISSOLVED SULPHATE IN VARIOUS GEOTHERMAL FIELDS OF SUMATRA USING OXYGEN AND SULPHUR ISOTOPES

    Directory of Open Access Journals (Sweden)

    E. Ristin Pujiindiyati

    2010-06-01

    Full Text Available There are at least 30 high temperature systems; eleven active volcanoes, five degassing volcanoes and one caldera volcano controlled by Sumatra Fault Zone over a length of 1700 km. To understand this geothermal field system, some information about geochemistry including isotope composition in its fluid is needed. Sulphur-34 and oxygen-18 isotopes in dissolved sulphate pair have been used to determine the origin of acidic fluid of sulphate and to evaluate the process involved. The fluids from eight hot springs, two fumaroles, four deep wells and crater have been collected in along Sumatra geothermal fields. Sulphur-34 (d 34S (SO4, 0/00 CDT and oxygen-18 (d 18O (SO4, 0/00 SMOW in sulphate is analyzed according to Robinson-Kusakabe and Rafter method, respectively. The d 34S (SO4 values from Sibayak wells are more enriched of 16.8 0/00 to 18.2 0/0 that may indicate the dissolution of anhydrite minerals or isotope partitioning in hydration of SO2. The d 34S (SO4 values from two fumaroles (Pusuk Bukit - North Sumatra and Rantau Dadap - South Sumatra are at depleted value of -0.150/00 and 1.80/00, those are close to d 34S from magmatic sulphur.  In general, the d 34S (SO4 of springs spread in a wide range of 5.250/00 to14.20/00 and show a mixing process between atmospheric sulphate and sulphate from deep wells. The d 18O (SO4 from wells exhibits depleted value around -3.60/00 suggesting that 87.5% of sulphate oxygen is derived from groundwater oxygen and 12.5% is derived from atmospheric molecular oxygen in sulphide oxidation reaction. In the other hand, hot springs (except Semurup, crater and fumaroles have enriched value of d 18O (SO4. These enriched values suggest that a higher percentage of atmospherically derived oxygen compared to those from the depth.   Keywords: isotope, geothermal, Sumatra

  10. Extreme diel dissolved oxygen and carbon cycles in shallow vegetated lakes.

    Science.gov (United States)

    Andersen, Mikkel R; Kragh, Theis; Sand-Jensen, Kaj

    2017-09-13

    A common perception in limnology is that shallow lakes are homogeneously mixed owing to their small water volume. However, this perception is largely gained by downscaling knowledge from large lakes to their smaller counterparts. Here we show that shallow vegetated lakes (less than 0.6 m), in fact, undergo recurring daytime stratification and nocturnal mixing accompanied by extreme chemical variations during summer. Dense submerged vegetation effectively attenuates light and turbulence generating separation between warm surface waters and much colder bottom waters. Photosynthesis in surface waters produces oxygen accumulation and CO2 depletion, whereas respiration in dark bottom waters causes anoxia and CO2 accumulation. High daytime pH in surface waters promotes precipitation of CaCO3 which is re-dissolved in bottom waters. Nocturnal convective mixing re-introduces oxygen into bottom waters for aerobic respiration and regenerated inorganic carbon into surface waters, which supports intense photosynthesis. Our results reconfigure the basic understanding of local environmental gradients in shallow lakes, one of the most abundant freshwater habitats globally. © 2017 The Author(s).

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

    Science.gov (United States)

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

    2015-04-15

    The monochloroacetic, dichloroacetic and trichloroacetic acid (MCAA, DCAA and TCAA) removed by metallic iron under controlled dissolved oxygen conditions (0, 0.75, 1.52, 2.59, 3.47 or 7.09 mg/L DO) was investigated in well-mixed batch systems. The removal of CAAs increased first and then decreased with increasing DO concentration. Compared with anoxic condition, the reduction of MCAA and DCAA was substantially enhanced in the presence of O2, while TCAA reduction was significantly inhibited above 2.59 mg/L. The 1.52 mg/L DO was optimum for the formation of final product, acetic acid. Chlorine mass balances were 69-102%, and carbon mass balances were 92-105%. With sufficient mass transfer from bulk to the particle surface, the degradation of CAAs was limited by their reduction or migration rate within iron particles, which were dependent on the change of reducing agents and corrosion coatings. Under anoxic conditions, the reduction of CAAs was mainly inhibited by the available reducing agents in the conductive layer. Under low oxic conditions, the increasing reducing agents and thin lepidocrocite layer were favorable for CAA dechlorination. Under high oxic conditions, the redundant oxygen competing for reducing agents and significant lepidocrocite growth became the major restricting factors. Various CAA removal mechanisms could be potentially applied to explaining the effect of DO concentration on iron efficiency for contaminant reduction in water and wastewater treatment. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Assessment of the uncertainty budget for the amperometric measurement of dissolved oxygen.

    Science.gov (United States)

    Fisicaro, Paola; Adriaens, Annemie; Ferrara, Enzo; Prenesti, Enrico

    2007-07-30

    This work aimed at identifying the main sources of uncertainty for the measurement of dissolved oxygen concentration in aqueous solutions. The experimental apparatus consists of an amperometric cell based on the Clark-type sensor. The corresponding uncertainty budget was assessed, this being a fundamental step for the validation of a measurement method. The principle of the measurement, as well as the procedure for the set-up and the characterisation of the cell, are described. The measurement equation was defined as a combination of Faraday's and Fick's laws, and a method was worked out for the empirical determination of the diffusivity parameter. In this connection, the solutions of oxygen were standardised by way of the Winkler's titration, as suggested by the ISO Guide 5813 and 5814. With this approach we aimed at contributing to the development of a potential primary method of measurement. A discussion of all the contributions to the overall uncertainty is reported, allowing operators to locate the largest ones and plan specific improvements.

  13. Multi-pollutant treatment of crystalline cellulosic effluent: Function of dissolved oxygen on process control.

    Science.gov (United States)

    Shanthi Sravan, J; Naresh Kumar, A; Venkata Mohan, S

    2016-10-01

    Treatment of crystalline cellulose based wastewater was carried out in periodic discontinuous batch reactor (PDBR). Specific influence of dissolved oxygen on treatment of crystalline cellulosic (CC) wastewater was evaluated in three different microenvironments such as aerobic, anoxic and anaerobic. PDBR-aerobic biosystem documented relatively higher substrate degradation [2.63kgCOD/m(3)-day (92%)] in comparison to PDBR-anoxic [2.12kgCOD/m(3)-day (71%)] and PDBR-anaerobic [1.81kgCOD/m(3)-day (63%)], which is in accordance with the observed DO levels. Similarly, multipollutants viz., phosphates and nitrates removal was observed to be higher in aerobic followed by anoxic and anaerobic operations. Higher nitrate removal in aerobic operation might be attributed to the efficient denitrification carried out by the biocatalyst, which utilizes both nitrates and oxygen as oxidizing agents. Multiscan spectral profiles depicted reduction in color intensity in all three microenvironments that correlated with the substrate degradation observed. Despite the high organic load, PDBR functioned well without exhibiting process inhibition.

  14. Variation in oxygen isotope ratio of dissolved orthophosphate induced by uptake process in natural coral holobionts

    Science.gov (United States)

    Ferrera, Charissa M.; Miyajima, Toshihiro; Watanabe, Atsushi; Umezawa, Yu; Morimoto, Naoko; San Diego-McGlone, Maria Lourdes; Nadaoka, Kazuo

    2016-06-01

    A model incubation experiment using natural zooxanthellate corals was conducted to evaluate the influence of phosphate uptake by coral holobionts on oxygen isotope ratio of dissolved PO4 3- (δ18Op). Live coral samples of Acropora digitifera, Porites cylindrica, and Heliopora coerulea were collected from coral reefs around Ishigaki Island (Okinawa, Japan) and Bolinao (northern Luzon, Philippines) and incubated for 3-5 d after acclimatization under natural light conditions with elevated concentrations of PO4 3-. Phosphate uptake by corals behaved linearly with incubation time, with uptake rate depending on temperature. δ18Op usually increased with time toward the equilibrium value with respect to oxygen isotope exchange with ambient seawater, but sometimes became higher than equilibrium value at the end of incubation. The magnitude of the isotope effect associated with uptake depended on coral species; the greatest effect was in A. digitifera and the smallest in H. coerulea. However, it varied even within samples of a single coral species, which suggests multiple uptake processes with different isotope effects operating simultaneously with varying relative contributions in the coral holobionts used. In natural environments where concentrations of PO4 3- are much lower than those used during incubation, PO4 3- is presumably turned over much faster and the δ18Op easily altered by corals and other major primary producers. This should be taken into consideration when using δ18Op as an indicator of external PO4 3- sources in coastal ecosystems.

  15. Influences of dissolved oxygen concentration on biocathodic microbial communities in microbial fuel cells.

    Science.gov (United States)

    Rago, Laura; Cristiani, Pierangela; Villa, Federica; Zecchin, Sarah; Colombo, Alessandra; Cavalca, Lucia; Schievano, Andrea

    2017-08-01

    Dissolved oxygen (DO) at cathodic interface is a critical factor influencing microbial fuel cells (MFC) performance. In this work, three MFCs were operated with cathode under different DO conditions: i) air-breathing (A-MFC); ii) water-submerged (W-MFC) and iii) assisted by photosynthetic microorganisms (P-MFC). A plateau of maximum current was reached at 1.06±0.03mA, 1.48±0.06mA and 1.66±0.04mA, increasing respectively for W-MFC, P-MFC and A-MFC. Electrochemical and microbiological tools (Illumina sequencing, confocal microscopy and biofilm cryosectioning) were used to explore anodic and cathodic biofilm in each MFC type. In all cases, biocathodes improved oxygen reduction reaction (ORR) as compared to abiotic condition and A-MFC was the best performing system. Photosynthetic cultures in the cathodic chamber supplied high DO level, up to 16mgO2L(-1), which sustained aerobic microbial community in P-MFC biocathode. Halomonas, Pseudomonas and other microaerophilic genera reached >50% of the total OTUs. The presence of sulfur reducing bacteria (Desulfuromonas) and purple non-sulfur bacteria in A-MFC biocathode suggested that the recirculation of sulfur compounds could shuttle electrons to sustain the reduction of oxygen as final electron acceptor. The low DO concentration limited the cathode in W-MFC. A model of two different possible microbial mechanisms is proposed which can drive predominantly cathodic ORR. Copyright © 2017 Elsevier B.V. All rights reserved.

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

    Science.gov (United States)

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

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

    Science.gov (United States)

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

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

    Science.gov (United States)

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

  19. The Effect of Increased Temperatures and Ultraviolet Radiation on Dissolved Oxygen in Ecosystems Primarily Comprised of "Euglena"

    Science.gov (United States)

    Carpenter, Matt

    2009-01-01

    The purpose of this study was to determine whether increased levels of UV radiation and temperatures from global warming have a significant impact on dissolved oxygen (DO) output from the alga, "Euglena," which affects other organisms in the ecosystem. The original hypothesis stated that if temperature was increased along with exposure time to…

  20. Rapid depletion of dissolved oxygen in 96 well microtitre plate Staphylococcus epidermidis biofilm assays promotes biofilm development and is influenced by inoculum cell concentration

    OpenAIRE

    Cotter, John J.; O'Gara, James P.; Casey, Eoin

    2009-01-01

    Biofilm-related research using 96-well microtiter plates involves static incubation of plates indiscriminate of environmental conditions, making oxygen availability an important variable which has not been considered to date. By directly measuring dissolved oxygen concentration over time we report here that dissolved oxygen is rapidly consumed in Staphylococcus epidermidis biofilm cultures grown in 96-well plates irrespective of the oxygen concentration in the gaseous environment in which the...

  1. Effects of resuspension on benthic fluxes of oxygen, nutrients, dissolved inorganic carbon, iron and manganese in the Gulf of Finland, Baltic Sea

    NARCIS (Netherlands)

    Almroth, E.; Tengberg, A.; Andersson, J.H.; Pakhomova, S.; Hall, P.O.J.

    2009-01-01

    The effect of resuspension on benthic fluxes of oxygen (O2), ammonium (NH4+), nitrate (NO3-), phosphate (PO43-), silicate (Si(OH)4), dissolved inorganic carbon (DIC), total dissolved iron (Fe) and total dissolved manganese (Mn) was studied at three different stations in the Gulf of Finland (GoF),

  2. Variability and Dynamics of Dissolved Oxygen in the Transition Zone of the North Sea and the Baltic Sea

    DEFF Research Database (Denmark)

    Jonasson, Lars

    the estimated oxygen consumption trends and the concentration of dissolved inorganic nitrogen. This study highlights the necessity to consider the combined effect of climate change and eutrophication on the oxygen conditions when assessing the nutrient reduction efforts. Climatic changes have lowered the oxygen...... oxygen. Though hypoxia occurs naturally, the frequency and the duration of these events have increased considerably during the second half of the last century in response to a long-term eutrophication trend. Several legislative actions have been implemented to reduce the land based nutrient load......, but these efforts have not yet been accompanied with improved oxygen conditions. However, both anthropogenic and natural processes influence the oxygen concentrations, and it is crucial to understand the dynamics and interplay of these processes to effectively improve the water quality. This thesis provides new...

  3. Manipulation of Microenvironment with a Built-in Electrochemical Actuator in Proximity of a Dissolved Oxygen Microsensor

    Science.gov (United States)

    Kim, Chang-Soo; Lee, Cae-Hyang; Fiering, Jason O.; Ufer, Stefan; Scarantino, Charles W.; Nagle, H. Troy; Fiering, Jason O.; Ufer, Stefan; Nagle, H. Troy; Scarantino, Charles W.

    2004-01-01

    Abstract - Biochemical sensors for continuous monitoring require dependable periodic self- diagnosis with acceptable simplicity to check its functionality during operation. An in situ self- diagnostic technique for a dissolved oxygen microsensor is proposed in an effort to devise an intelligent microsensor system with an integrated electrochemical actuation electrode. With a built- in platinum microelectrode that surrounds the microsensor, two kinds of microenvironments, called the oxygen-saturated or oxygen-depleted phases, can be created by water electrolysis depending on the polarity. The functionality of the microsensor can be checked during these microenvironment phases. The polarographic oxygen microsensor is fabricated on a flexible polyimide substrate (Kapton) and the feasibility of the proposed concept is demonstrated in a physiological solution. The sensor responds properly during the oxygen-generating and oxygen- depleting phases. The use of these microenvironments for in situ self-calibration is discussed to achieve functional integration as well as structural integration of the microsensor system.

  4. Estimation and application of indicator values for common macroinvertebrate genera and families of the United States

    Science.gov (United States)

    Carlisle, D.M.; Meador, M.R.; Moulton, S.R.; Ruhl, P.M.

    2007-01-01

    Tolerance of macroinvertebrate taxa to chemical and physical stressors is widely used in the analysis and interpretation of bioassessment data, but many estimates lack empirical bases. Our main objective was to estimate genus- and family-level indicator values (IVs) from a data set of macroinvertebrate communities, chemical, and physical stressors collected in a consistent manner throughout the United States. We then demonstrated an application of these IVs to detect alterations in benthic macroinvertebrate assemblages along gradients of urbanization in New England and Alabama. Principal components analysis (PCA) was used to create synthetic gradients of chemical stressors, for which genus- and family-level weighted averages (WAs) were calculated. Based on results of PCA, WAs were calculated for three synthetic gradients (ionic concentration, nutrient concentration, and dissolved oxygen/water temperature) and two uncorrelated physical variables (suspended sediment concentration and percent fines). Indicator values for each stress gradient were subsequently created by transforming WAs into ten ordinal ranks based on percentiles of values across all taxa. Mean IVs of genera and families were highly correlated to road density in Alabama and New England, and supported the conclusions of independent assessments of the chemical and physical stressors acting in each geographic area. Family IVs were nearly as responsive to urbanization as genus IVs. The limitations of widespread use of these IVs are discussed.

  5. Predicting Impact of Climate Change on Water Temperature and Dissolved Oxygen in Tropical Rivers

    Directory of Open Access Journals (Sweden)

    Al-Amin Danladi Bello

    2017-07-01

    Full Text Available Predicting the impact of climate change and human activities on river systems is imperative for effective management of aquatic ecosystems. Unique information can be derived that is critical to the survival of aquatic species under dynamic environmental conditions. Therefore, the response of a tropical river system under climate and land-use changes from the aspects of water temperature and dissolved oxygen concentration were evaluated. Nine designed projected climate change scenarios and three future land-use scenarios were integrated into the Hydrological Simulation Program FORTRAN (HSPF model to determine the impact of climate change and land-use on water temperature and dissolved oxygen (DO concentration using basin-wide simulation of river system in Malaysia. The model performance coefficients showed a good correlation between simulated and observed streamflow, water temperature, and DO concentration in a monthly time step simulation. The Nash–Sutcliffe Efficiency for streamflow was 0.88 for the calibration period and 0.82 for validation period. For water temperature and DO concentration, data from three stations were calibrated and the Nash–Sutcliffe Efficiency for both water temperature and DO ranged from 0.53 to 0.70. The output of the calibrated model under climate change scenarios show that increased rainfall and air temperature do not affects DO concentration and water temperature as much as the condition of a decrease in rainfall and increase in air temperature. The regression model on changes in streamflow, DO concentration, and water temperature under the climate change scenarios illustrates that scenarios that produce high to moderate streamflow, produce small predicted change in water temperatures and DO concentrations compared with the scenarios that produced a low streamflow. It was observed that climate change slightly affects the relationship between water temperatures and DO concentrations in the tropical rivers that we

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1982-01-01

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

  7. Effect of dissolved oxygen, temperature, initial cell count, and sugar concentration on the viability of Saccharomyces cerevisiae in rapid fermentations.

    Science.gov (United States)

    Nagodawithana, T W; Castellano, C; Steinkraus, K H

    1974-09-01

    By using 7 x 10(8) cells of Saccharomyces cerevisiae per ml with which 25 degrees Brix honey solutions were fermented to 9.5% (wt/vol; 12% vol/vol) ethanol in 2.5 to 3 h at 30 C, i.e., rapid fermentation, the death rate was found to be high, with only 2.1% of the yeast cells surviving at the end of 3 h under anaerobic conditions. As the dissolved oxygen in the medium was increased from 0 to 13 to 20 to 100% in rapid fermentations at 30 C, there was a progressive increase in the percentage of cells surviving. The ethanol production rate and total were not seriously affected by a dissolved oxygen concentration of 13%, but fermentation was retarded by 20% dissolved oxygen and still further decreased as the dissolved oxygen content reached 100%. When the fermentation temperature was decreased to 15 C (at 13% dissolved oxygen), the rate of fermentation decreased, and the fermentation time to 9.5% ethanol (wt/vol) increased to 6 h. It was found that the higher the temperature between 15 and 30 C, the greater the rate of death as initial cell counts were increased from 1.1 x 10(7) to 7.8 x 10(8) cells per ml. At the lowest level of inoculum, 1.1 x 10(7) cells per ml, there was actual multiplication, even at 30 C; however, the fermentation was no longer rapid. The addition of 15% sugar, initially followed after an hour by the remaining 10%, or addition of the sugar in increments of 2.5 or 5% yielded a better survival rate of yeast cells than when the fermentation was initiated with 25% sugar.

  8. Modeling chlorophyll-a and dissolved oxygen concentration in tropical floodplain lakes (Paraná River, Brazil).

    Science.gov (United States)

    Rocha, R R A; Thomaz, S M; Carvalho, P; Gomes, L C

    2009-06-01

    The need for prediction is widely recognized in limnology. In this study, data from 25 lakes of the Upper Paraná River floodplain were used to build models to predict chlorophyll-a and dissolved oxygen concentrations. Akaike's information criterion (AIC) was used as a criterion for model selection. Models were validated with independent data obtained in the same lakes in 2001. Predictor variables that significantly explained chlorophyll-a concentration were pH, electrical conductivity, total seston (positive correlation) and nitrate (negative correlation). This model explained 52% of chlorophyll variability. Variables that significantly explained dissolved oxygen concentration were pH, lake area and nitrate (all positive correlations); water temperature and electrical conductivity were negatively correlated with oxygen. This model explained 54% of oxygen variability. Validation with independent data showed that both models had the potential to predict algal biomass and dissolved oxygen concentration in these lakes. These findings suggest that multiple regression models are valuable and practical tools for understanding the dynamics of ecosystems and that predictive limnology may still be considered a powerful approach in aquatic ecology.

  9. Rapid depletion of dissolved oxygen in 96-well microtiter plate Staphylococcus epidermidis biofilm assays promotes biofilm development and is influenced by inoculum cell concentration.

    Science.gov (United States)

    Cotter, John J; O'Gara, James P; Casey, Eoin

    2009-08-01

    Biofilm-related research using 96-well microtiter plates involves static incubation of plates indiscriminate of environmental conditions, making oxygen availability an important variable which has not been considered to date. By directly measuring dissolved oxygen concentration over time we report here that dissolved oxygen is rapidly consumed in Staphylococcus epidermidis biofilm cultures grown in 96-well plates irrespective of the oxygen concentration in the gaseous environment in which the plates are incubated. These data indicate that depletion of dissolved oxygen during growth of bacterial biofilm cultures in 96-well plates may significantly influence biofilm production. Furthermore higher inoculum cell concentrations are associated with more rapid consumption of dissolved oxygen and higher levels of S. epidermidis biofilm production. Our data reveal that oxygen depletion during bacterial growth in 96-well plates may significantly influence biofilm production and should be considered in the interpretation of experimental data using this biofilm model.

  10. Influence of dissolved oxygen on silver nanoparticle mobility and dissolution in water-saturated quartz sand

    Energy Technology Data Exchange (ETDEWEB)

    Mittelman, Anjuliee M.; Taghavy, Amir; Wang, Yonggang; Abriola, Linda M.; Pennell, Kurt D., E-mail: kurt.pennell@tufts.edu [Tufts University, Department of Civil and Environmental Engineering (United States)

    2013-07-15

    The influence of dissolved oxygen (DO) on the transport behavior and dissolution kinetics of silver nanoparticles (nAg) was explored through a combination of experimental and mathematical modeling studies. One-dimensional column experiments were conducted with water-saturated 40-50 mesh Ottawa sand, operated at pH 4 or 7 under three DO conditions (8.9, 2, or <0.2 mg/L). The experimental protocol consisted of a nAg deposition phase, designed to assess nanoparticle mobility as a function of DO level, followed by a dissolution phase, to evaluate the release of Ag{sup +} from retained nanoparticles. Experimental observations revealed that the mobility of nAg increased by 15 % when the DO level was reduced from 8.9 to <0.2 mg/L at pH 4, and that, once retained by the quartz sand, the fraction of nAg mass eluted as Ag{sup +} decreased from 21.6 to 13.5 to 11.3 % with decreasing oxygen level (8.9, 2, and <0.2 mg/L, respectively). In both batch and column studies, rates of nAg dissolution decreased over time, behavior attributed to aging of the nanoparticle surface due to oxidation. A hybrid Eulerian-Lagrangian nanoparticle transport model was developed and implemented to simulate the mobility of nAg, subject to DO-dependent dissolution kinetics and particle aging. Model simulations accurately captured nAg transport and dissolution as a function of pH and DO level, and demonstrate the importance of considering nanoparticle surface aging to accurately predict Ag{sup +} release over time.

  11. Preferential flow characterization in fractured aquifer by injecting dissolved oxygen in boreholes

    Science.gov (United States)

    Vurro, Michele; Donnaloia, Mietta; Masciopinto, Costantino; Pennetta, Luigi; Robbins, Gary; Vitale, Sarah

    2016-04-01

    A new approach to identify contributing fractures and wellbore flow in fractured and karst aquifers is presented. It is time efficient, low cost and based on a benign tracer: the dissolved oxygen (DO). The method was already applied by other scientists to test fractured crystalline rock wells. The DO method consists in elevating water DO concentration in a borehole by bubbling air at assigned water depths using a porous polypropylene tube (bubbler) connected to a compressed air tank with tubing. After the aeration, the resulting profile should be a linear increase in DO with depth due to the effects of water pressure on oxygen solubility. Any changes in the DO profile will be then observed when water flows into and through the well. DO dilution can be used to locate inflowing fractures and to define active flow zones in wells. If there is no change in the DO profile, a "dead zones" in the well is present, that is to say no flow is taking place or can be identified. The DO tests in this work have been carried out in the industrial area of Bari, at the experimental station, constituted by five wells drilled at the CNR-IRSA. The wells penetrate karstic limestone. Results show enhanced flow through at depths between 32 and 37 meters below the water level: DO concentrations decrease until they reach values close to 0 mg/l. DO curves show also the presence of inflowing fractures, as testified by the decrease in the DO concentrations due to the effects of water dilution, at depths of 4 and 9 meters (below the water table) in the north well, at 4 and 10 meters in the central well, and at 30 meters in the south well. The benefits of utilizing DO as a tracer include ease of accessibility, low cost and time-efficiency as well as non-toxic nature of the tracer and no impact on flow conditions.

  12. Integrating the pulse of the riverscape and landscape: modelling stream metabolism using continuous dissolved oxygen measurements

    Science.gov (United States)

    Soulsby, C.; Birkel, C.; Malcolm, I.; Tetzlaff, D.

    2013-12-01

    Stream metabolism is a fundamental pulse of the watershed which reflects both the in-stream environment and its connectivity with the wider landscape. We used high quality, continuous (15 minute), long-term (>3 years) measurement of stream dissolved oxygen (DO) concentrations to estimate photosynthetic productivity (P) and system respiration (R) in forest and moorland reaches of an upland stream with peaty soils. We calibrated a simple five parameter numerical oxygen mass balance model driven by radiation, stream and air temperature, stream depth and re-aeration capacity. This used continuous 24-hour periods for the whole time series to identify behavioural simulations where DO simulations were re-produced sufficiently well to be considered reasonable representations of ecosystem functioning. Results were evaluated using a seasonal Regional Sensitivity Analysis and a co-linearity index for parameter sensitivity. This showed that >95 % of the behavioural models for the moorland and forest sites were identifiable and able to infer in-stream processes from the DO time series for almost half of all measured days at both sites. Days when the model failed to simulate DO levels successfully provided invaluable insight into time periods when other factors are likely to disrupt in-stream metabolic processes; these include (a) flood events when scour reduces the biomass of benthic primary producers, (b) periods of high water colour in higher summer/autumn flows and (c) low flow periods when hyporheic respiration is evident. Monthly P/R ratios tree cover is likely to be a much larger source of carbon to the atmosphere (122 mmol C m-2 d-1) compared to the forested reach (64 mmol C m-2 d-1). The study indicates the value of integrating field and modelling studies of stream metabolism as a means of understanding the dynamic interactions of the riverscape and its surrounding landscape.

  13. Short-term covariation of dissolved oxygen and phytoplankton photosynthesis in a coastal fish aquaculture site

    Science.gov (United States)

    Yoshikawa, Takashi; Murata, Osamu; Furuya, Ken; Eguchi, Mitsuru

    2007-09-01

    The influence of phytoplankton photosynthesis (PP) on dissolved oxygen (DO) dynamics was evaluated in a red sea bream ( Pagrus major) aquaculture site. The surface PP was monitored continuously by a natural fluorescence sensor for 2-3 weeks during all seasons, except spring. In summer, when the daily PP was low during cloudy weather, DO at the surface markedly decreased below the critical level (5.7 mg O 2 L -1), which is needed for normal fish growth. However, on the subsequent clear day, active PP restored the DO back to above the critical level. In fall, under cloudy skies, the surface DO also decreased below the critical level and remained there, even when the subsequent days were clear. In winter, DO remained at high levels throughout the water column due to an active supply from the air and vertical mixing. Besides seasonal changes, surface DO showed a diel cycle with a minimum early in the morning and maximum in the evening. This diel cycle was also regulated by planktonic photosynthesis. This was most obvious and its amplitude was largest in summer, as PP was very high and thermal stratification prevented diffusion of DO from the surface to deeper water. The present study is the first detailed report on the close coupling of DO with PP in coastal waters, even under non-bloom conditions. Cloudy weather and early mornings were found to be the most critical periods in oxygen supply to cultured fish and other pelagic organisms in a fish culture site and other eutrophic coastal area.

  14. Estimation of Biochemical Oxygen Demand Based on Dissolved Organic Carbon, UV Absorption, and Fluorescence Measurements

    Directory of Open Access Journals (Sweden)

    Jihyun Kwak

    2013-01-01

    Full Text Available Determination of 5-d biochemical oxygen demand (BOD5 is the most commonly practiced test to assess the water quality of surface waters and the waste loading. However, BOD5 is not a good parameter for the control of water or wastewater treatment processes because of its long test period. It is very difficult to produce consistent and reliable BOD5 results without using careful laboratory quality control practices. This study was performed to develop software sensors to predict the BOD5 of river water and wastewater. The software sensors were based on the multiple regression analysis using the dissolved organic carbon (DOC concentration, UV light absorbance at 254 nm, and synchronous fluorescence spectra. River water samples and wastewater treatment plant (WWTP effluents were collected at 1-hour interval to evaluate the feasibility of the software sensors. In short, the software sensors developed in this study could well predict the BOD5 of river water (r=0.78 and for the WWTP effluent (r=0.90.

  15. Versatile common instrumentation for optical detection of pH and dissolved oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Sardesai, Neha [Department of Computer Science and Electrical Engineering, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250 (United States); Rao, Govind [Center for Advanced Sensor Technology and Department of Chemical, Biochemical, and Environmental Engineering, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250 (United States); Kostov, Yordan, E-mail: kostov@umbc.edu [Department of Computer Science and Electrical Engineering, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250 (United States); Center for Advanced Sensor Technology and Department of Chemical, Biochemical, and Environmental Engineering, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250 (United States)

    2015-07-15

    The recent trend toward use of disposable and miniature bioreactors requires the use of appropriate sensors. pH and dissolved oxygen (DO) are often measured using optical chemical sensors due to their small form factor and convenience in use. These sensors are often interrogated using a specialized opto-electronic transducer that is designed around the optical sensor. In this contribution, we are presenting a new class of opto-electronic transducers that are usable with several different chemical sensors without the need to switch the optics or hardware when changing the type of the chemical sensor. This allows flexibility closer to the lab-grade devices while the size is closer to a dedicated sensor. This versatile instrumentation is capable of seamlessly switching between the pH and DO measurement modes and is capable of auto recognition of the sensor type. The principle of ratiometric fluorescence is used for pH measurements, and that of fluorescence lifetime for DO measurements. An approach to obtain identical calibrations between several devices is also presented. The described hardware constitutes common instrumentation for measuring either pH or DO and has been tested in actual bioprocesses. It has been found adequate for continuous bioprocess monitoring.

  16. Dissolved oxygen transfer to sediments by sweep and eject motions in aquatic environments

    Science.gov (United States)

    O'Connor, B.L.; Hondzo, Miki

    2008-01-01

    Dissolved oxygen (DO) concentrations were quantified near the sediment-water interface to evaluate DO transfer to sediments in a laboratory recirculating flume and open channel under varying fluid-flow conditions. DO concentration fluctuations were observed within the diffusive sublayer, as defined by the time-averaged DO concentration gradient near the sediment-water interface. Evaluation of the DO concentration fluctuations along with detailed fluid-flow characterizations were used to quantify quasi-periodic sweep and eject motions (bursting events) near the sediments. Bursting events dominated the Reynolds shear stresses responsible for momentum and mass fluctuations near the sediment bed. Two independent methods for detecting bursting events using DO concentration and velocity data produced consistent results. The average time between bursting events was scaled with wall variables and was incorporated into a similarity model to describe the dimensionless mass transfer coefficient (Sherwood number, Sh) in terms of the Reynolds number, Re, and Schmidt number, Sc, which described transport in the flow. The scaling of bursting events was employed with the similarity model to quantify DO transfer to sediments and results showed a high degree of agreement with experimental data. ?? 2008, by the American Society of Limnology and Oceanography, Inc.

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

    Science.gov (United States)

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

    2014-05-01

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

  18. Performance of completely autotrophic nitrogen removal over nitrite process under different aeration modes and dissolved oxygen

    Institute of Scientific and Technical Information of China (English)

    Jinsong GUO; Guohong YANG; Fang FANG; Yu QIN

    2008-01-01

    In this study, three sequential batch biofilm reactors (SBBRs) were operated for 155 days to evaluate the performance of completely autotrophic nitrogen removal over nitrite (CANON) process under different aeration modes and dissolved oxygen (DO). Synthetic wastewater with 160-mg NH4+-N/L was fed into the reac-tors. In the continuously-aerated reactor, the efficiency of the ammonium nitrogen conversion and total nitrogen (TN) removal reached 80% and 70%, respectively, with DO between 0.8-1.0 mg/L. Whereas in the intermit-tently-aerated reactor, at the aeration/non-aeration ratio of 1.0, ammonium was always under the detection limit and 86% of TN was removed with DO between 2.0 2.5 mg/L during the aeration time. Results show that CANON could be achieved in both continuous and inter-mittent aeration pattern. However, to achieve the same nitrogen removal efficiency, the DO needed in the inter-mittently-aerated sequential batch biofilm reactor (SBBR) during the aeration period was higher than that in the continuously-aerated SBBR. In addition, the DO in the CANON system should be adjusted to the aeration mode, and low DO was not a prerequisite to CANON process.

  19. The influence of dissolved oxygen level and medium on biofilm formation by Campylobacter jejuni.

    Science.gov (United States)

    Teh, Amy Huei Teen; Lee, Sui Mae; Dykes, Gary A

    2017-02-01

    Campylobacter jejuni survival in aerobic environments has been suggested to be mediated by biofilm formation. Biofilm formation by eight C. jejuni strains under both aerobic and microaerobic conditions in different broths (Mueller-Hinton (MH), Bolton and Brucella) was quantified. The dissolved oxygen (DO) content of the broths under both incubation atmospheres was determined. Biofilm formation for all strains was highest in MH broth under both incubation atmospheres. Four strains had lower biofilm formation in MH under aerobic as compared to microaerobic incubation, while biofilm formation by the other four strains did not differ under the 2 atm. Two strains had higher biofilm formation under aerobic as compared to microaerobic atmospheres in Bolton broth. Biofilm formation by all other strains in Bolton, and all strains in Brucella broth, did not differ under the 2 atm. Under aerobic incubation DO levels in MH > Brucella > Bolton broth. Under microaerobic conditions levels in MH = Brucella > Bolton broth. Levels of DO in MH and Brucella broth were lower under microaerobic conditions but those of Bolton did not differ under the 2 atm. Experimental conditions and especially the DO of broth media confound previous conclusions drawn about aerobic biofilm formation by C. jejuni.

  20. Predicting Late Winter Dissolved Oxygen Levels in Arctic Lakes Using Morphology and Landscape Metrics

    Science.gov (United States)

    Leppi, Jason C.; Arp, Christopher D.; Whitman, Matthew S.

    2016-02-01

    Overwintering habitat for Arctic freshwater fish is essential, such that understanding the distribution of winter habitat quality at the landscape-scale is warranted. Adequate dissolved oxygen (DO) is a major factor limiting habitat quality in the Arctic region where ice cover can persist for 8 months each year. Here we use a mixed-effect model developed from 20 lakes across northern Alaska to assess which morphology and landscape attributes can be used to predict regional overwintering habitat quality. Across all lakes, we found that the majority of the variations in late winter DO can be explained by lake depth and littoral area. In shallow lakes (cover duration, and snow depth were associated with DO regimes. Low DO regimes were most typical of shallow lakes with large littoral areas and lakes that had high DO regimes often were lakes with limited littoral areas and deeper water. Our analysis identifies metrics that relate to late winter DO regimes in Arctic lakes that can aid managers in understanding which lakes will likely provide optimum DO for overwintering habitat. Conversely, lakes which predicted to have marginal winter DO levels may be vulnerable to disturbances that could lower DO below critical thresholds to support sensitive fish. In regions where lakes are also used by humans for industrial winter water supply, such as ice-road construction for oil and gas development, these findings will be vital for the management of resources and protection of Arctic fish.

  1. An Intelligent Optical Dissolved Oxygen Measurement Method Based on a Fluorescent Quenching Mechanism

    Directory of Open Access Journals (Sweden)

    Fengmei Li

    2015-12-01

    Full Text Available Dissolved oxygen (DO is a key factor that influences the healthy growth of fishes in aquaculture. The DO content changes with the aquatic environment and should therefore be monitored online. However, traditional measurement methods, such as iodometry and other chemical analysis methods, are not suitable for online monitoring. The Clark method is not stable enough for extended periods of monitoring. To solve these problems, this paper proposes an intelligent DO measurement method based on the fluorescence quenching mechanism. The measurement system is composed of fluorescent quenching detection, signal conditioning, intelligent processing, and power supply modules. The optical probe adopts the fluorescent quenching mechanism to detect the DO content and solves the problem, whereas traditional chemical methods are easily influenced by the environment. The optical probe contains a thermistor and dual excitation sources to isolate visible parasitic light and execute a compensation strategy. The intelligent processing module adopts the IEEE 1451.2 standard and realizes intelligent compensation. Experimental results show that the optical measurement method is stable, accurate, and suitable for online DO monitoring in aquaculture applications.

  2. Versatile common instrumentation for optical detection of pH and dissolved oxygen

    Science.gov (United States)

    Sardesai, Neha; Rao, Govind; Kostov, Yordan

    2015-07-01

    The recent trend toward use of disposable and miniature bioreactors requires the use of appropriate sensors. pH and dissolved oxygen (DO) are often measured using optical chemical sensors due to their small form factor and convenience in use. These sensors are often interrogated using a specialized opto-electronic transducer that is designed around the optical sensor. In this contribution, we are presenting a new class of opto-electronic transducers that are usable with several different chemical sensors without the need to switch the optics or hardware when changing the type of the chemical sensor. This allows flexibility closer to the lab-grade devices while the size is closer to a dedicated sensor. This versatile instrumentation is capable of seamlessly switching between the pH and DO measurement modes and is capable of auto recognition of the sensor type. The principle of ratiometric fluorescence is used for pH measurements, and that of fluorescence lifetime for DO measurements. An approach to obtain identical calibrations between several devices is also presented. The described hardware constitutes common instrumentation for measuring either pH or DO and has been tested in actual bioprocesses. It has been found adequate for continuous bioprocess monitoring.

  3. Effect of dissolved oxygen concentration on lettuce growth in floating hydroponics.

    Science.gov (United States)

    Goto, E; Both, A J; Albright, L D; Langhans, R W; Leed, A R

    1996-12-01

    Lettuce (Lactuca sativa L., cv. Ostinata) growth experiments were carried out to study the effect of dissolved oxygen (DO) concentration on plant growth in a floating hydroponic system. Pure O2 and N2 gas were supplied to the hydroponic system for precise DO control. This system made it easy to increase the DO concentration beyond the maximum (or saturation) concentration possible when bubbling air into water. Eleven day old lettuce seedlings were grown for 24 days under various DO concentrations: sub-saturated, saturated, and super-saturated. There was no significant difference in fresh weight, shoot and root dry weights among the DO concentrations: 2.1 (25% of saturated at 24 degrees C), 4.2 (50%), 8.4 (saturated), and 16.8 (200%) mg/L. The critical DO concentration for vigorous lettuce growth was considered to be lower than 2.1 mg/L. Neither root damage nor delay of shoot growth was observed at any of the studied DO concentrations.

  4. Correlations between dissolved organic matter optical properties and quantum yields of singlet oxygen and hydrogen peroxide.

    Science.gov (United States)

    Dalrymple, Renée M; Carfagno, Amy K; Sharpless, Charles M

    2010-08-01

    Various aquatic dissolved organic matter (DOM) samples produce singlet oxygen (1O2) and hydrogen peroxide (H2O2) with quantum yields of 0.59 to 4.5% (1O2 at 365 nm) and 0.017 to 0.053% (H2O2, 300-400 nm integrated). The two species' yields have opposite pH dependencies and strong, but opposite, correlations with the E2/E3 ratio (A254 divided by A365). Linear regressions allow prediction of both quantum yields from E2/E3 in natural water samples with errors ranging from -3% to 60%. Experimental evidence and kinetic calculations indicate that less than six percent of the H2O2 is produced by reaction between 1O2 and DOM. The inverse relationship between the 1O2 and H2O2 yields is thus best explained by a model in which precursors to these species are populated competitively. A model is presented, which proposes that important precursors to H2O2 may be either charge-transfer or triplet states of DOM.

  5. Enhanced nitrogen removal in constructed wetlands: effects of dissolved oxygen and step-feeding.

    Science.gov (United States)

    Li, Fengmin; Lu, Lun; Zheng, Xiang; Ngo, Huu Hao; Liang, Shuang; Guo, Wenshan; Zhang, Xiuwen

    2014-10-01

    Four horizontal subsurface flow constructed wetlands (HSFCWs), named HSFCW1 (three-stage, without step-feeding), HSFCW2 (three-stage, with step-feeding), HSFCW3 (five-stage, without step-feeding) and HSFCW4 (five-stage, with step-feeding) were designed to investigate the effects of dissolved oxygen (DO) and step-feeding on nitrogen removal. High removal of 90.9% COD, 99.1% ammonium nitrogen and 88.1% total nitrogen (TN) were obtained simultaneously in HSFCW4 compared with HSFCW1-3. The excellent TN removal of HSFCW4 was due to artificial aeration provided sufficient DO for nitrification and the favorable anoxic environment created for denitrification. Step-feeding was a crucial factor because it provided sufficient carbon source (high COD: nitrate ratio of 14.3) for the denitrification process. Microbial activities and microbial abundance in HSFCW4 was found to be influenced by DO distribution and step-feeding, and thus improve TN removal. These results suggest that artificial aeration combined with step-feeding could achieve high nitrogen removal in HSFCWs.

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

    Science.gov (United States)

    Chen, C K; Lo, S L

    2005-07-01

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

  7. Simulation modeling of hydropower impacts on dissolved oxygen in the upper Ohio river basin

    Energy Technology Data Exchange (ETDEWEB)

    Railsback, S.F.; Jager, H.I.

    1988-09-01

    A model has been developed to assess the impacts of hydropower development at navigation dams on dissolved oxygen (DO) concentrations in the upper Ohio River basin. Field data were used to fit statistical models of aeration at each dam. The Streeter-Phelps equations were used to model DO concentrations between dams. Input data sources were compiled, and the design conditions used for assessment of hydropower impacts were developed. The model was implemented both as Lotus 1-2-3 spreadsheets and as a FORTRAN program. This report contains users' guides for both of these implementations. The sensitivities and uncertainty of the model were analyzed. Modeled DO concentrations are sensitive to water temperature and flow rates, and sensitivities to dam aeration are relatively high in reaches where dam aeration rates are high. Uncertainty in the model was low in reaches dominated by dam aeration and higher in reaches with low dam aeration rates. The 95% confidence intervals for the model range from about /+-/ 0.5 mg/L to about /+-/ 1.5 mg/L.

  8. Evaluation of dissolved oxygen in water by artificial neural network and sample optimization

    Institute of Scientific and Technical Information of China (English)

    陈丽华; 李丽

    2008-01-01

    Three important factors influencing directly the dissolved oxygen (DO) of river including the outflow, the water temperature and the pH, were used as input parameters to set up a BP neural network based on Levenberg-Marquant algorithm. The neural network model was proposed to evaluate DO in water. The model contains two parts: firstly, the learning sample is unified; secondly, the neural network is used to train the unified samples to ensure the best node number of hidden layer. The proposed model is applied to assessing the DO concentration of the Yellow River in Lanzhou city. The evaluation result is compared with that by the neural network method and the reported result in Lanzhou city. The comparison result indicates that the performance of the neural network model is practically feasible in the assessment of DO. At the same time, the linear interpolation method can add the number of network’s learning sample to improve the prediction precision of the network.

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

    Science.gov (United States)

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

    2014-12-01

    High-loaded membrane bioreactors (HL-MBRs), i.e. MBRs which are operated at extremely short sludge and hydraulic retention times, can be applied to flocculate and concentrate sewage organic matter. The concentrated organics can be used for energy recovery, or for the production of more valuable organic chemicals. Little is known about the effect of the dissolved oxygen concentration (DO) on this bioflocculation process. To examine this effect, two HL-MBRs were operated, respectively at a low (1 mg L(-1)) and a higher (4 mg L(-1)) DO. The higher DO resulted in a better flocculation efficiency, i.e. 92% of the colloidal COD in the sewage flocculated compared to 69% at the lower DO. The difference was attributed to a higher microbial production of extracellular polymeric substances at a DO of 4 mg L(-1) and to more multivalent cations (calcium, iron and aluminium) being distributed to the floc matrix. In addition, the HL-MBR that was operated at a DO of 4 mg L(-1) gave a bigger mean floc size, a lower supernatant turbidity, better settleability and better membrane filterability than the HL-MBR that was operated at a DO of 1 mg L(-1). Copyright © 2014 Elsevier Ltd. All rights reserved.

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

    Directory of Open Access Journals (Sweden)

    D. G. Pereira

    2008-06-01

    Full Text Available 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 < 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 controlled by means of the incoming gas composition control (air/N2 or air/O2. From the response surface plots it can be verified that the effect of C was greater than that of N on the production of both metabolites. The absorbance for red pigments varied from 1.6 U (C< 10%; N=200 rpm up to 3.3 U (C=60%; N=600 rpm, an increase of 106%, while citrinin concentration increased 257%, from 14.2 to 50.7 mg.L-1. The most appropriate conditions were C=60% and N=600rpm, under which the highest red pigment absorbance (3.3U and half of the highest citrinin concentration were obtained.

  11. The effect of Sequoyah Nuclear Plant on dissolved oxygen in Chickamauga Reservoir

    Energy Technology Data Exchange (ETDEWEB)

    Butkus, S.R.; Shiao, M.C.; Yeager, B.L.

    1990-09-01

    During the summer of 1985, the Tennessee Division of Water Pollution Control and the Tennessee Wildlife Resources Agency measured dissolved oxygen (DO) concentrations downstream from the Sequoyah Nuclear Plant (SQN) discharge mixing zone that were below the state criterion for DO. The Tennessee General Water Quality Criteria'' specifies that DO should be a minimum of 5.0 mg/l measured at a depth of 5 feet for the protection of fish and aquatic life. The Tennessee Valley Authority developed the present study to answer general concerns about reservoir conditions and potential for adverse effects on aquatic biota. Four objectives were defined for this study: (1) to better define the extent and duration of the redistribution of DO in the reservoir, (2) to better understand DO dynamics within the mixing zone, (3) to determine whether DO is being lost (or added) as the condenser cooling water passes through the plant, and (4) to evaluate the potential for impact on aquatic life in the reservoir.

  12. Precise calibration of equilibrium oxygen isotope fractionations between dissolved phosphate and water from 3 to 37 °C

    Science.gov (United States)

    Chang, Sae Jung; Blake, Ruth E.

    2015-02-01

    The stable oxygen isotope composition of orthophosphate (δ18OPO4) is a widely used (paleo)temperature indicator and more recently, a useful tracer of phosphorus-cycling. In natural aqueous systems (e.g., oceans, rivers, soil/ground water) the largest reactive phosphorus pool is dissolved inorganic phosphate. Here, we present a new experimentally-determined equation for thermodynamic equilibrium O-isotope fractionations between dissolved phosphate and water, catalyzed by the enzyme inorganic pyrophosphatase (PPase) between 3 and 37 °C;

  13. Anticorrelated observed and modeled trends in dissolved oceanic oxygen over the last 50 years

    Directory of Open Access Journals (Sweden)

    L. Stramma

    2012-04-01

    Full Text Available Observations and model runs indicate trends in dissolved oxygen (DO associated with current and ongoing global warming. However, a large-scale observation-to-model comparison has been missing and is presented here. This study presents a first global compilation of DO measurements covering the last 50 years. It shows declining upper-ocean DO levels in many regions, especially the tropical oceans, whereas areas with increasing trends are found in the subtropics and in some subpolar regions. For the Atlantic Ocean south of 20° N, the DO history could even be extended back to about 70 years, showing decreasing DO in the subtropical South Atlantic. The global mean DO trend between 50° S and 50° N at 300 dbar for the period 1960 to 2010 is −0.063 μmol kg−1 yr−1. Results of a numerical biogeochemical Earth system model reveal that the magnitude of the observed change is consistent with CO2-induced climate change. However, the correlation between simulated and observed patterns of past DO change is negative, indicating that the model does not correctly reproduce the processes responsible for observed regional oxygen changes in the past 50 years. A negative pattern correlation is also obtained for model configurations with particularly low and particularly high diapycnal mixing, for a configuration that assumes a CO2-induced enhancement of the C:N ratios of exported organic matter and irrespective of whether climatological or realistic winds from reanalysis products are used to force the model. Depending on the model configuration the 300 dbar DO trend between 50° S and 50° N is −0.026 to −0.046 μmol kg−1 yr−1. Although numerical models reproduce the overall sign and, to some extent, magnitude of observed ocean deoxygenation, this degree of realism does not necessarily apply to simulated regional patterns and the representation of processes involved in their generation

  14. Heterogeneity in a Suburban River Network: Understanding the Impact of Fluvial Wetlands on Dissolved Oxygen and Metabolism in Headwater Streams

    Science.gov (United States)

    Cain, J. S.; Wollheim, W. M.; Sheehan, K.; Lightbody, A.

    2014-12-01

    Low dissolved oxygen content in rivers threatens fish populations, aquatic organisms, and the health of entire ecosystems. River systems with high fluvial wetland abundance and organic matter, may result in high metabolism that in conjunction with low re-aeration rates, lead to low oxygen conditions. Increasing abundance of beaver ponds in many areas may exacerbate this phenomenon. This research aims to understand the impact of fluvial wetlands, including beaver ponds, on dissolved oxygen (D.O.) and metabolism throughout the headwaters of the Ipswich R. watershed, MA, USA. In several fluvial wetland dominated systems, we measured diel D.O. and metabolism in the upstream inflow, the surface water transient storage zones of fluvial wetland sidepools, and at the outflow to understand how the wetlands modify dissolved oxygen. D.O. was also measured longitudinally along entire surface water flow paths (x-y km long) to determine how low levels of D.O. propagate downstream. Nutrient samples were also collected to understand how their behavior was related to D.O. behavior. Results show that D.O. in fluvial wetlands has large swings with periods of very low D.O. at night. D.O. swings were also seen in downstream outflow, though lagged and somewhat attenuated. Flow conditions affect the level of inundation and the subsequent effects of fluvial wetlands on main channel D.O.. Understanding the D.O. behavior throughout river systems has important implications for the ability of river systems to remove anthropogenic nitrogen.

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

    Science.gov (United States)

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

    2015-08-01

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

  16. Validation of updated RANNS with effect of oxygen-dissolved metallic Zircaloy-4 under LOCA quench condition

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Hsingtzu; Udagawa, Yutaka; Narukawa, Takafumi; Amaya, Masaki, E-mail: amaya.masaki@jaea.go.jp

    2016-04-15

    Highlights: • Equations about the impact of the oxygen-dissolved Zircaloy-4 metallic layer which are newly added to RANNS code are described. • Validation of RANNS code using LOCA quench experimental data is presented. • The impact of the oxygen-dissolved metallic layer and the oxide layer formed on the surface of cladding on its axial load is discussed. - Abstract: Loss-of-Coolant-Accident (LOCA) is a design basis accident considered in LWR safety analyses, and LOCA simulation technique can be used to gain a better understanding of local cladding behaviors. This paper first summarizes equations regarding the oxygen-dissolved metallic Zircaloy-4 which have been implemented into the updated RANNS code. It is then validated using experimental data. The oxidation temperature is about 1473 K, the oxidation time is about 182.5 s and the quench temperature is about 973 K. The difference between the measured axial load and the RANNS computation as the cladding surface temperature reaches about 373 K is about 18.7%. In addition, the updated RANNS code is used to examine the influence of the oxygen absorbed into cladding on its axial load under LOCA quench conditions with oxidation time up to 674 s. The results suggest that the contributions of both the oxygen-dissolved metallic layer and the oxide layer to the axial load increase with oxidation time. The former corresponds to about a tenth of the computed axial load. These findings are considered useful for improving the accuracy of the analyses of the fuel rod behaviors during LOCA conditions.

  17. Biodiversity patterns of macrophyte and macroinvertebrate communities in two lagoons of Western Greece.

    Science.gov (United States)

    Fyttis, G.; Reizopoulou, S.; Papastergiadou, E.

    2012-04-01

    Aquatic macrophytes and benthic macroinvertebrates were studied seasonally (Spring, Autumn, Summer) between the years 2009 - 2011 in two coastal lagoons (Kotychi and Prokopos) located in Peloponnese, Greece, in order to investigate spatial and temporal biodiversity trends related to hydrological processes (degree of confinement, nitrates, phosphates, chl-a, total suspended materials, light irradiance, pH, salinity, temperature and dissolved oxygen). Kotychi lagoon presents a better communication with the sea, while Prokopos has a high degree of confinement. Both ecosystems seasonally receive freshwater input from streams. The submerged aquatic macrophytes constituted a major component of the ecosystems studied. In total, 22 taxa of aquatic macrophytes (angiosperms and macroalgae), 16 taxa for Kotychi (2 Rhodophyta, 8 Chlorophyta, 5 Magnoliophyta, 1 Streptophyta) and 14 taxa for Prokopos (1 Rhodophyta, 5 Chlorophyta, 5 Magnoliophyta, 3 Streptophyta) were found. Ruppia cirrhosa, and Potamogeton pectinatus were dominant in both lagoons. Kotychi lagoon was also dominated by Zostera noltii and Prokopos by Zannichellia pallustris ssp. pedicellata, while the biomass of aquatic species peaked during the summer periods, in both lagoons. The total number of macroinvertebrates found in the lagoons was 28 taxa for Kotychi and 19 for Prokopos. Chironomidae were dominant in both lagoons, while Kotychi was also dominated by Lekanesphaera monodi and Monocorophium insidiosum, and Prokopos by Ostracoda and Lekanesphaera monodi. Benthic diversity ranged from 1.33 to 2.57 in Kotychi and from 0.67 to 2.48 in Prokopos. Species richness, diversity, and abundance of benthic macroinvertebrates were strongly related to aquatic vegetation and to the degree of communication with the marine environment. Moreover, species richness and abundance of both macrophytes and macroinvertebrates were mainly dependent on depth, temperature, pH and concentration of total suspended materials (TSM). Results

  18. A comparative study of the triple oxygen analyses of dissolved oxygen in a fresh water system (Feitsui reservoir) and South China Sea at SEATS station

    Science.gov (United States)

    Jurikova, H.; Guha, T.; Liang, M. C.

    2014-12-01

    We report the first insight into the stable isotopic composition of dissolved O2 from the Feitsui Reservoir, which supplies drinking water for millions of people living in Taipei, Taiwan. In addition, first observations on 17Δ from a cruise to South China Sea (the long-term station SEATS) in 2013 were also included for comparison. A regular sampling effort for collection of water samples from the Feitsui Reservoir was initiated in May 2014. The 17Δ of dissolved O2 from water samples was assessed to examine its spatial variations, variability over time and to estimate the gross oxygen production rates (GOP). Primary productivity estimated from the dissolved O2 will be compared to that from 14C. Results and implications will be presented and discussed.

  19. Inkjet-printed dissolved oxygen and pH sensors on flexible plastic substrates

    Science.gov (United States)

    Moya, A.; Zea, M.; Sowade, E.; Villa, R.; Ramon, E.; Baumann, R. R.; Gabriel, G.

    2017-06-01

    There are a broad range of applications such as analytical sensors, biosensing and medical applications that require the monitoring of dissolved oxygen (DO) and pH using sensitive, stable, compact and low cost sensors. Here we develop full inkjet printing sensors to measure DO and pH. They have been fabricated using commercially available gold and platinum inks in plastic substrates. The inks are specially designed formulation which allows their sintering at temperatures as low as 150 and 190 °C for Au and Pt respectively. This is a key point in the development of low-cost sensors made on plastic and paper substrates. These sensors integrate in a single platform all the basic elements for pH and DO recording, allowing the measures without any external electrode. The DO is directly measured with a gold working electrode, and the pH sensors is achieved after electrodepositing iridium oxide film over platinum working electrode. The printed electrodes for DO sensing exhibits excellent linearity between 0 and 8 mg L _ 1 range, with correlation factors greater than 0.99, obtaining low limits of detection, 0.17 mgL _ 1 and a sensitivity of 0.06 A(mgL) _ 1. IrOx pH sensors exhibit a super-Nernstian response in sensitivity repeatedly and reversibly between 65 mV/pH in the pH range of 3 to 10. This work demonstrates that these sensors are suitable for the determination of DO and pH and provide a cost-effective solution for future electrochemical monitoring systems.

  20. Puget Sound Dissolved Oxygen Modeling Study: Development of an Intermediate Scale Water Quality Model

    Energy Technology Data Exchange (ETDEWEB)

    Khangaonkar, Tarang; Sackmann, Brandon S.; Long, Wen; Mohamedali, Teizeen; Roberts, Mindy

    2012-10-01

    The Salish Sea, including Puget Sound, is a large estuarine system bounded by over seven thousand miles of complex shorelines, consists of several subbasins and many large inlets with distinct properties of their own. Pacific Ocean water enters Puget Sound through the Strait of Juan de Fuca at depth over the Admiralty Inlet sill. Ocean water mixed with freshwater discharges from runoff, rivers, and wastewater outfalls exits Puget Sound through the brackish surface outflow layer. Nutrient pollution is considered one of the largest threats to Puget Sound. There is considerable interest in understanding the effect of nutrient loads on the water quality and ecological health of Puget Sound in particular and the Salish Sea as a whole. The Washington State Department of Ecology (Ecology) contracted with Pacific Northwest National Laboratory (PNNL) to develop a coupled hydrodynamic and water quality model. The water quality model simulates algae growth, dissolved oxygen, (DO) and nutrient dynamics in Puget Sound to inform potential Puget Sound-wide nutrient management strategies. Specifically, the project is expected to help determine 1) if current and potential future nitrogen loadings from point and non-point sources are significantly impairing water quality at a large scale and 2) what level of nutrient reductions are necessary to reduce or control human impacts to DO levels in the sensitive areas. The project did not include any additional data collection but instead relied on currently available information. This report describes model development effort conducted during the period 2009 to 2012 under a U.S. Environmental Protection Agency (EPA) cooperative agreement with PNNL, Ecology, and the University of Washington awarded under the National Estuary Program

  1. Allocation of supplementary aeration stations in the Chicago waterway system for dissolved oxygen improvement.

    Science.gov (United States)

    Alp, Emre; Melching, Charles S

    2011-06-01

    The Chicago Waterway System (CWS), used mainly for commercial and recreational navigation and for urban drainage, is a 122.8 km branching network of navigable waterways controlled by hydraulic structures. The CWS receives pollutant loads from 3 of the largest wastewater treatment plants in the world, nearly 240 gravity Combined Sewer Overflows (CSO), 3 CSO pumping stations, direct diversions from Lake Michigan, and eleven tributary streams or drainage areas. Even though treatment plant effluent concentrations meet the applicable standards and most reaches of the CWS meet the applicable water quality standards, Dissolved Oxygen (DO) standards are not met in the CWS during some periods. A Use Attainability Analysis was initiated to evaluate what water quality standards can be achieved in the CWS. The UAA team identified several DO improvement alternatives including new supplementary aeration stations. Because of the dynamic nature of the CWS, the DUFLOW model that is capable of simulating hydraulics and water quality processes under unsteady-flow conditions was used to evaluate the effectiveness of new supplementary aeration stations. This paper details the use of the DUFLOW model to size and locate supplementary aeration stations. In order to determine the size and location of supplemental aeration stations, 90% compliance with a 5 mg/l DO standard was used as a planning target. The simulations showed that a total of four new supplementary aeration stations with oxygen supply capacities ranging from 30 to 80 g/s would be sufficient to meet the proposed target DO concentration for the North Branch and South Branch of the Chicago River. There are several aeration technologies, two of which are already being used in the CWS, available and the UAA team determined that the total capital costs of the alternatives range from $35.5 to $89.9 million with annual operations and maintenance costs ranging from $554,000 to $2.14 million. Supplemental aeration stations have been

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

    Directory of Open Access Journals (Sweden)

    K. Castro-Morales

    2012-01-01

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

  3. The use of dissolved oxygen-controlled, fed-batch aerobic cultivation for recombinant protein subunit vaccine manufacturing.

    Science.gov (United States)

    Farrell, Patrick; Sun, Jacob; Champagne, Paul-Philippe; Lau, Heron; Gao, Meg; Sun, Hong; Zeiser, Arno; D'Amore, Tony

    2015-11-27

    A simple "off-the-shelf" fed-batch approach to aerobic bacterial cultivation for recombinant protein subunit vaccine manufacturing is presented. In this approach, changes in the dissolved oxygen levels are used to adjust the nutrient feed rate (DO-stat), so that the desired dissolved oxygen level is maintained throughout cultivation. This enables high Escherichia coli cell densities and recombinant protein titers. When coupled to a kLa-matched scale-down model, process performance is shown to be consistent at the 2L, 20L, and 200L scales for two recombinant E. coli strains expressing different protein subunit vaccine candidates. Additionally, by mining historical DO-stat nutrient feeding data, a method to transition from DO-stat to a pre-determined feeding profile suitable for larger manufacturing scales without using feedback control is demonstrated at the 2L, 20L, and 200L scales.

  4. Measuring water quality from individual fractures in open wellbores using hydraulic isolation and the dissolved oxygen alteration method

    Science.gov (United States)

    Vitale, Sarah A.; Robbins, Gary A.

    2017-08-01

    This study describes a low-cost method for sampling individual fractures in open wellbores in crystalline bedrock utilizing naturally occurring flow conditions in the well. The method entails using the dissolved oxygen alteration method (DOAM) to identify transmissive fractures and vertical flow direction. After obtaining information about relative hydraulic gradients, flow direction in the well is modified using a single control pump to isolate fractures of interest for sampling. Additional dissolved oxygen, injected during the DOAM procedure, serves as a tracer to ensure the water quality in the sampling zone is characteristic of the fracture of interest by requiring a tracer-free zone prior to sampling. Sampling procedures are described conceptually for nine bedrock wells with varying flow conditions containing one, two, or three transmissive inflowing fractures. The method was demonstrated in two crystalline bedrock wells containing one and two transmissive inflowing fractures.

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

    Science.gov (United States)

    Quan, Ying; Han, Hui; Zheng, Shaokui

    2012-09-01

    The successful application of bioaugmentation is largely dependent on the selective enrichment of culture with regards to pH, temperature, salt, or specific toxic organic pollutants. In this study, we investigated the effect of dissolved oxygen (DO) concentrations (aerobic, >2 mg L(-1); microaerobic, concentrations (aerobic/microaerobic) should be considered a secondary selective pressure to achieve successful bioaugmentation. Copyright © 2012 Elsevier Ltd. All rights reserved.

  6. A Deterministic Model for Predicting Hourly Dissolved Oxygen Change: Development and Application to a Shallow Eutrophic Lake

    OpenAIRE

    Zhen Xu; Y. Jun Xu

    2016-01-01

    Predicting dissolved oxygen (DO) change at a high frequency in water bodies is useful for water quality management. In this study, we developed a deterministic model that can predict hourly DO change in a water body with high frequency weather parameters. The study was conducted during August 2008–July 2009 in a eutrophic shallow lake in Louisiana, USA. An environment monitoring buoy was deployed to record DO, water temperature and chlorophyll-a concentration at 15-min intervals, and hourly w...

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

    Science.gov (United States)

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

    2007-10-01

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

  8. Diel patterns of temperature, conductivity and dissolved oxygen in an Amazon floodplain lake: description of a friagem phenomenon

    Directory of Open Access Journals (Sweden)

    Pedro Caraballo

    2014-09-01

    Full Text Available AIM: The aim of this work was to study the diel stratification parameters temperature, dissolved oxygen and conductivity, providing a more detailed description of a friagem event. METHODS: the mixing behavior of the limnetic water column in Lago Catalão, an Amazon floodplain lake flooded by two of the world’s largest rivers (Solimões and Negro, was studied through diel profiling of temperature, conductivity and dissolved oxygen, between 2006 and 2007. Measurements were made every four hours at 1m depth intervals to the lake bottom. RESULTS: The water column remained stratified during most of the year with the exception of one month with low water level, when nocturnal mixing occurred and one friagem event during high water (May 2007 when an isothermal temperature profile and an atypical orthograde oxygen profile were observed. CONCLUSIONS: The friagem event, a large drop in air temperatures due to the intrusion of a polar air mass in the Amazon, constitutes an important force in the dynamics of the water column, which produces a profound redistribution of dissolved gases and solutes in the system. This is the first time that the effects of the friagem on the mixing patterns in a lowland Amazon lake have been documented in detail. The decline in air temperature, observed during the friagem event destabilized the normally stratified water column, which can be associated with an environmental disturb.

  9. Processes controlling dissolved oxygen and pH in the upper Willamette River basin, Oregon, 1994

    Science.gov (United States)

    Pogue, Ted R.; Anderson, Chauncey W.

    1995-01-01

    In July and August of 1994, the U. S. Geological Survey in cooperation with the Oregon Department of Environmental Quality (ODEQ) collected data to document the spatial extent and diel variability of dissolved oxygen (DO) concentrations and pH levels in selected reaches of streams in the upper Willamette River Basin. These data were also collected to identify primary factors that control DO concentrations downstream from major point sources as well as to provide ODEQ with data to refine calibration of their steady-state DO and nutrient models for the upper Willamette River Basin. All of the reaches studied had diel variations in DO and pH. The magnitude of the diel variations in DO ranged from 0.2 to 3.9 milligrams per liter (7 to 50 percent-saturation units based on ambient water temperature and barometric pressure) and in pH from 0.3 to 1.4 units. However, of the reaches studied, only the Coast Fork Willamette River from river mile (RM) 21.7 to 12.5 and the Willamette River from RM 151 to 141.6 had field measured violations of State standards for DO and pH. DO concentration and pH in water depend on many factors. Data were collected to examine several major factors, including BOD (biochemical oxygen demand), carbonaceous BOD, nitrogenous BOD, and measures of photosynthetic activity. Of the four study reaches, only a short stretch of the Coast Fork Willamette River has potential for important levels of oxygen consumption from BOD or nitrification. Additionally, water-column primary-productivity measurements indicated that respiration and photosynthesis by free-floating algae did not explain the observed diel variations in DO in the study reaches. Results from a simple mathematical model incorporating measures of community respiration and net primary productivities indicated that periphyton are capable of producing a diel variation of the order of magnitude observed during the August study period. In the Willamette River near Peoria, the combined periphyton DO

  10. Modeling evaluation of integrated strategies to meet proposed dissolved oxygen standards for the Chicago waterway system.

    Science.gov (United States)

    Melching, Charles S; Ao, Yaping; Alp, Emre

    2013-02-15

    The Chicago Waterway System (CWS) is a 113.8 km branching network of navigable waterways controlled by hydraulic structures in which the majority of flow is treated sewage effluent and there are periods of substantial combined sewer overflow. The Illinois Pollution Control Board (IPCB) designated the majority of the CWS as Secondary Contact and Indigenous Aquatic Life Use waters in the 1970s and made small alterations to these designations in 1988. Between 1988 and 2002 substantial improvements in the pollution control and water-quality management facilities were made in the Chicago area. The results of a Use Attainability Analysis led the Illinois Environmental Protection Agency (IEPA) to propose the division of the CWS into two new aquatic life use classes with appropriate dissolved oxygen (DO) standards. To aid the IPCB in their deliberations regarding the appropriate water use classifications and DO standards for the CWS, the DUFLOW model that is capable of simulating hydraulics and water-quality processes under unsteady-flow conditions was used to evaluate integrated strategies of water-quality improvement facilities that could meet the proposed DO standards during representative wet (2001) and dry (2003) years. A total of 28 new supplementary aeration stations with a maximum DO load of 80 or 100 g/s and aerated flow transfers at three locations in the CWS would be needed to achieve the IEPA proposed DO standards 100% of the time for both years. A much simpler and less costly (≈one tenth of the cost) system of facilities would be needed to meet the IEPA proposed DO standards 90% of the time. In theory, the combinations of flow augmentation and new supplemental aeration stations can achieve 100% compliance with the IEPA proposed DO standards, however, 100% compliance will be hard to achieve in practice because of-(1) difficulties in determining when to turn on the aeration stations and (2) localized heavy loads of pollutants during storms that may yield

  11. Revisiting inland hypoxia: diverse exceedances of dissolved oxygen thresholds for freshwater aquatic life.

    Science.gov (United States)

    Saari, Gavin N; Wang, Zhen; Brooks, Bryan W

    2017-04-11

    Water resources in many regions are stressed by impairments resulting from climate change, population growth and urbanization. In the United States (US), water quality criteria (WQC) and standards (WQS) were established to protect surface waters and associated designated uses, including aquatic life. In inland waters of the south central US, for example, depressed dissolved oxygen (DO) consistently results in impaired aquatic systems due to noncompliance with DO WQC and WQS. In the present study, we systematically examined currently available DO threshold data for freshwater fish and invertebrates and performed probabilistic aquatic hazard assessments with low DO toxicity data that were used to derive the US Environmental Protection Agency's (EPA) Ambient Water Quality Criteria (AWQC) for DO and newly published information. Aquatic hazard assessments predicted acute invertebrate DO thresholds for Ephemeroptera, Plecoptera, or Trichoptera (EPT) taxa and species inhabiting lotic systems to be more sensitive than fish. For example, these organisms were predicted to have acute low DO toxicity thresholds exceeding the US EPA guidelines 17, 26, 31 and 38% and 13, 24, 30 and 39% of the time at 8.0, 5.0, 4.0 and 3.0 mg DO/L, respectively. Based on our analysis, it appears possible that low DO effects to freshwater organisms have been underestimated. We also identified influences of temperature on low DO thresholds and pronounced differences in implementation and assessment of the US EPA AWQC among habitats, seasons, and geographic regions. These results suggest some implemented DO guidelines may adversely affect the survival, growth, and reproduction of freshwater aquatic organisms in a region susceptible to climate change and rapid population growth. Given the global decline of species, particularly invertebrates, low DO threshold information, including sublethal (e.g., reproduction, behavior) responses, for additional species (e.g., mollusks, other invertebrates, warm

  12. Patterns, drivers and implications of dissolved oxygen dynamics in tropical mangrove forests

    Science.gov (United States)

    Mattone, Carlo; Sheaves, Marcus

    2017-10-01

    Estuarine mangrove forests regulate and facilitate many ecological processes, and provide nursery ground for many commercially important species. However, mangroves grow in sediments with high carbon loading and high respiration rates which can potentially influencing the dissolved oxygen (DO) dynamics of tidal water flowing into mangrove forests, as bacteria strip DO from the incoming water to carry out metabolic functions. In turn this is likely to influence the way nekton and other aquatic organisms utilize mangrove forests. Despite these possibilities, previous work has focused on looking at DO dynamics within mangrove creeks, with little research focusing on understanding DO dynamics within the mangrove forests themselves during tidal inundation or of DO levels of pools within the forest remaining once the tide has ebbed. The present study investigates the pattern in DO at various distances within an estuarine Rhizophora stylosa forest in tropical north Queensland. DO levels were recorded at 5 min interval over 2 days and multiple tidal cycles, data were collected between 2013 and 2014 for a total of 32 tidal cycles encompassing multiples seasons and tidal amplitudes. There were substantial fluctuations in DO, often varying from normoxic to hypoxic within the same tidal cycle. A range of factors influenced DO dynamics, in particular: tidal height, amount of sunlight, tidal phase, and distance from the outer edge of the mangrove forest. In fact, spring tides tend to have high DO saturation, particularly during the flooding phase, however as the tide starts ebbing, DO depletes rapidly especially in areas further inside the forest. Moreover during tidal disconnection the remnant pools within the forest quickly became anoxic. These variations in DO suggest that the use of mangrove forests by animals is likely to be constrained by their ability to withstand low DO levels, and provides a plausible explanation for the apparent paucity of benthic organism observed

  13. Geographic variation in phenotypic plasticity in response to dissolved oxygen in an African cichlid fish

    National Research Council Canada - National Science Library

    CRISPO, E; CHAPMAN, L. J

    2010-01-01

    .... We examined genetic and plastic variation in gill and brain size among swamp (low oxygen; hypoxic) and river (normal oxygen; normoxic) populations of an African cichlid fish, Pseudocrenilabrus multicolor victoriae...

  14. Dissolved oxygen content in apple must: technological implications in cider processing

    National Research Council Canada - National Science Library

    Alberti, Aline; Braga, Cíntia Maia; Jaster, Henrique; Nogueira, Alessandro

    2014-01-01

    Oxygen can influence the composition and quality of apple must and cider. In this study, the effect of unit operations on oxygen dissolution during apple must processing was investigated and the technological implications discussed...

  15. Dissolved oxygen, salinity, temperature, and depth data from bottle casts in the North Atlantic Ocean from 05 February 1973 to 19 August 1980 (NODC Accession 0000289)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Dissolved oxygen, salinity, temperature, and depth data were collected using bottle casts in the North Atlantic Ocean from February 5, 1973 to August 19, 1980. These...

  16. Temperature, salinity, dissolved oxygen, nutrients, and currents data from the Chesapeake Bay region from multiple platforms, July 1949 - July 1965 (NODC Accession 7000995)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These data are currently only available in analog form. A digital scan of the pages containing measured values for temperature, salinity, dissolved oxygen,...

  17. Dissolved oxygen, salinity, and temperature data from bottle casts in the North Atlantic Ocean from 01 December 1974 to 04 November 1984 (NODC Accession 0000284)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Dissolved oxygen, salinity, and temperature data were collected using bottle casts in the North Atlantic Ocean from December 1, 1974 to November 4, 1984. Data were...

  18. Dissolved oxygen, salinity, temperature, and depth data from bottle casts in the North Atlantic Ocean from 07 February 1987 to 18 February 1991 (NODC Accession 0000290)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Dissolved oxygen, salinity, temperature, and depth data were collected using bottle casts in the North Atlantic Ocean from February 7, 1987 to February 18, 1991....

  19. Dissolved oxygen, salinity, and temperature data from multiple ships using CTD casts in the South Pacific Ocean from 26 March 1985 to 19 December 1997 (NODC Accession 0000286)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Dissolved oxygen, salinity, and temperature data were collected from the ALMIRANTE MONTT, CARLOS PORTE, SANTA MARGARITA II, MELI PULLI, IZISHI MARU, STELLA MARIS,...

  20. Effect of dissolved oxygen content on stress corrosion cracking of a cold worked 316L stainless steel in simulated pressurized water reactor primary water environment

    Science.gov (United States)

    Zhang, Litao; Wang, Jianqiu

    2014-03-01

    Stress corrosion crack growth tests of a cold worked nuclear grade 316L stainless steel were conducted in simulated pressurized water reactor (PWR) primary water environment containing various dissolved oxygen (DO) contents but no dissolved hydrogen. The crack growth rate (CGR) increased with increasing DO content in the simulated PWR primary water. The fracture surface exhibited typical intergranular stress corrosion cracking (IGSCC) characteristics.

  1. Effects of dissolved oxygen concentration and iron addition on immediate-early gene expression of Magnetospirillum gryphiswaldense MSR-1.

    Science.gov (United States)

    Zhuang, Shiwen; Anyaogu, Diana Chinyere; Kasama, Takeshi; Workman, Mhairi; Mortensen, Uffe Hasbro; Hobley, Timothy John

    2017-06-15

    We report the effects of dissolved oxygen (DO) concentration and iron addition on gene expression of Magnetospirillum gryphiswaldense MSR-1 cells during fermentations, focusing on 0.25-24 h after iron addition. The DO was strictly controlled at 0.5% or 5% O2, and compared with aerobic condition. Uptake of iron (and formation of magnetosomes) was only observed in the 0.5% O2 condition where there was little difference in cell growth and carbon consumption compared to the 5% O2 condition. Quantitative reverse transcription PCR analysis showed a rapid (within 0.25 h) genetic response of MSR-1 cells after iron addition for all the genes studied, except for MgFnr (oxygen sensor gene) and fur (ferric uptake regulator family gene), and which in some cases was oxygen dependent. In particular, expression of sodB1 (superoxide dismutase gene) and feoB1 (ferrous transport protein B1 gene) was markedly reduced in cultures at 0.5% O2 compared to those at higher oxygen tensions. Moreover, expression of katG (catalase-peroxidase gene) and feoB2 (ferrous transport protein B2 gene) was reduced markedly by iron addition, regardless of oxygen conditions. These data provide a greater understanding of molecular response of MSR-1 cells to environmental conditions associated with oxygen and iron metabolisms, especially relevant to immediate-early stage of fermentation. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  2. Abundance of dissolved polysaccharides in the oxygen minimum layer of the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Bhosle, N.B.; Bhaskar, P.V.; Ramachandran, S.

    ) were the most abundant form of total dissolved carbohydrates (TCHO) throughout the water column sampled and accounted for 75 plus or minus and 11% of the TCHO. Hydrolysis-resistant PCHO (HR-PCHO) contributed 48 plus or minusand 16% to the PCHO...

  3. Catalytic behavior of metallic particles in anisotropic etching of Ge(100) surfaces in water mediated by dissolved oxygen

    Science.gov (United States)

    Kawase, Tatsuya; Mura, Atsushi; Nishitani, Keisuke; Kawai, Yoshie; Kawai, Kentaro; Uchikoshi, Junichi; Morita, Mizuho; Arima, Kenta

    2012-06-01

    The authors demonstrate that Ge(100) surfaces containing metallic particles are etched anisotropically in water. This originates from the catalytic reduction of dissolved oxygen (O2) in water to water molecules (H2O) on the metallic particles, which is followed by the enhanced oxidation of Ge around the particles. The soluble nature of Ge oxide (GeO2) in water promotes the formation of inverted pyramidal etch pits composed of (111) microfacets. On the basis of the results, the authors propose strategies for avoiding unwanted surface roughening during the wet cleaning of Ge.

  4. Modelling of L-valine Repeated Fed-batch Fermentation Process Taking into Account the Dissolved Oxygen Tension

    Directory of Open Access Journals (Sweden)

    Tzanko Georgiev

    2009-03-01

    Full Text Available This article deals with synthesis of dynamic unstructured model of variable volume fed-batch fermentation process with intensive droppings for L-valine production. The presented approach of the investigation includes the following main procedures: description of the process by generalized stoichiometric equations; preliminary data processing and calculation of specific rates for main kinetic variables; identification of the specific rates takes into account the dissolved oxygen tension; establishment and optimisation of dynamic model of the process; simulation researches. MATLAB is used as a research environment.

  5. Dual perfluorocarbon method to noninvasively monitor dissolved oxygen concentration in tissue engineered constructs in vitro and in vivo.

    Science.gov (United States)

    Goh, Fernie; Long, Robert; Simpson, Nicholas; Sambanis, Athanassios

    2011-07-01

    Noninvasive in vivo monitoring of tissue implants provides important correlations between construct function and the observed physiologic effects. As oxygen is a key parameter affecting cell and tissue function, we established a monitoring method that utilizes (19) F nuclear magnetic resonance (NMR) spectroscopy, with perfluorocarbons (PFCs) as oxygen concentration markers, to noninvasively monitor dissolved oxygen concentration (DO) in tissue engineered implants. Specifically, we developed a dual PFC method capable of simultaneously measuring DO within a tissue construct and its surrounding environment, as the latter varies among animals and with physiologic conditions. In vitro studies using an NMR-compatible bioreactor demonstrated the feasibility of this method to monitor the DO within alginate beads containing metabolically active murine insulinoma βTC-tet cells, relative to the DO in the culture medium, under perfusion and static conditions. The DO profiles obtained under static conditions were supported by mathematical simulations of the system. In vivo, the dual PFC method was successful in tracking the oxygenation state of entrapped βTC-tet cells and the surrounding peritoneal DO over 16 days in normal mice. DO measurements correlated well with the extent of cell growth and host cell attachment examined postexplantation. The peritoneal oxygen environment was found to be variable and hypoxic, and significantly lower in the presence of metabolically active cells. The significance of the dual PFC system in providing critical DO measurements for entrapped cells and other tissue constructs, in vitro and in vivo, is discussed. Copyright © 2011 American Institute of Chemical Engineers (AIChE).

  6. Simple model of dissolved oxygen consumption in a bay within high organic loading: an applied remediation tool.

    Science.gov (United States)

    Ahumada, Ramón; Vargas, José; Pagliero, Liliana

    2006-07-01

    San Vicente Bay is a coastal shallow embayment in Central Chile with multiple uses, one of which is receiving wastewater from industrial fisheries, steel mill effluents, and domestic sewage. A simulation model was developed and applied to dissolved oxygen consumption by organic residues released into this embayment. Three compartments were established as function of: depth, circulation and outfall location. The model compartments had different volumes, and their oxygen saturation value was used as baseline. The parameters: (a) BOD5 of the industrial and urban effluents, (b) oxygen demand by organic sediments, (c) respiration, (d) photosynthesis and (e) re-aeration were included in the model. Iteration results of the model showed severe alterations in Compartment 1, with a decrease of 65% in the oxygen below saturation. Compartment 2 showed a small decline (10%) and compartment 3 did not show apparent changes in oxygen values. Measures recommended for remediation were to decrease the BOD5 loading by 30% in the affected sector. Iteration of the model for 200 h following recommendations derived from the preceding results produced an increase in saturation of 60% (5 ml O2 L(-1)), which suggested an improvement of the environmental conditions.

  7. Effects of anthropogenic silt on aquatic macroinvertebrates and abiotic variables in streams in the Brazilian Amazon

    Energy Technology Data Exchange (ETDEWEB)

    Couceiro, Sheyla Regina Marques; Hamada, Neusa [Inst. Nacional de Pesquisas da Amazonia, Coordenacao de Pesquisas em Entomologia, Manaus, AM (Brazil); Forsberg, Bruce Rider [Inst. Nacional de Pesquisas da Amazonia, Coordenacao de Pesquisas em Entomologia, Manaus, AM (Brazil); Inst. Nacional de Pesquisas da Amazonia, Coordenacao de Pesquisas em Ecologia, Manaus, AM (Brazil); Padovesi-Fonseca, Claudia [Univ. de Brasilia, Dept. de Ecologia, Brasilia, DF (Brazil)

    2010-01-15

    Purpose: While environmental risks associated with petroleum extraction such as oil spills or leaks are relatively well known, little attention has been given to the impacts of silt. The increase in petroleum exploitation in Amazonia has resulted in sediment input to aquatic systems, with impacts on their biodiversity. Here we use a combination of field measurements and statistical analyses to evaluate the impacts of anthropogenic silt derived from the construction of roads, borrow pits, and wells during the terrestrial development of gas and oil, on macroinvertebrate communities in streams of the Urucu Petroleum Province in the Central Brazilian Amazon. Material and methods: Ten impacted and nine non-impacted streams were sampled in January, April, and November of 2007. Macroinvertebrates were sampled along a 100-m continuous reach in each stream at 10-m intervals using a dip net. Abiotic variables including, a siltation index (SI), suspended inorganic sediment (SIS), sediment color index (SCI), suspend organic sediment (SOS), pH, electrical conductivity, dissolved oxygen, temperature, water velocity, channel width, and depth, were measured at three equidistant points in each stream ({proportional_to}30-m intervals). Results and discussion: SI did not differ between impacted and undisturbed streams. SIS was higher and SCI lower (more reddish) in impacted than in non-impacted streams. SCI had a positive and SIS a negative effect on both macroinvertebrate richness and density. SIS and SCI also influenced macrophyte taxonomic composition. In impacted streams, taxonomic richness and density were 1.5 times lower than in non-impacted streams. No taxon was significantly associated with impacted streams. SIS was positively correlated with SOS and electrical conductivity while SCI was negatively correlated with SOS, electrical conductivity, and pH. The lack of difference in SI between impacted and nonimpacted streams suggests that anthropogenic sediment does not accumulate

  8. L-Lake macroinvertebrate community

    Energy Technology Data Exchange (ETDEWEB)

    Specht, W.L.

    1996-06-01

    To characterize the present benthic macroinvertebrate community of L-Lake, Regions 5 and 7 of the reservoir were sampled in September 1995 at the same locations sampled in 1988 and 1989 during the L-Lake monitoring program. The macroinvertebrate community of 1995 is compared to that of 1988 and 1989. The species composition of L-Lake`s macroinvertebrate community has changed considerably since 1988-1989, due primarily to maturation of the reservoir ecosystem. L-Lake contains a reasonably diverse macroinvertebrate community that is capable of supporting higher trophic levels, including a diverse assemblage of fish species. The L-Lake macroinvertebrate community is similar to those of many other southeastern reservoirs, and there is no indication that the macroinvertebrate community is perturbed by chemical or physical stressors.

  9. Photoluminiscence response of Ru(II) complex immobilized in SiO2-based matrix to dissolved oxygen in beer.

    Science.gov (United States)

    Anastasova, S; Milanova, M; Todorovsky, D

    2008-04-24

    The possibility to use the photoluminescence of Ru(II) tris(4,7-diphenyl-1,10-phenathroline) dichloride, immobilized in sol-gel produced SiO2-based matrix for the determination of dissolved oxygen concentration in beer is studied. Organically-modified silane (octyltriethoxysilane) and mixtures from tetraethoxysilane and octyltriethoxysilane are used as precursors for matrix production. Spin- and dip-coating techniques are applied for films deposition. The predeposition ultrasound treatment of the sol ensures a good sensitivity and a linear sensor quenching response to oxygen in 1/6 ppm O2-concentration interval. The CO2 present practically has no effect on the films performance. Their photoluminescence show rather good stability on prolonged storage in beer.

  10. Dissolved Oxygen Dynamics in Coastal Pacific Northwest Rivers: Biological Controls and Management Options

    Science.gov (United States)

    Sobota, D. J.; Foster, E.; Michie, R.; Waltz, D.

    2014-12-01

    In Oregon's Central Coast Range (OCR), dissolved O2 concentrations in at least 10% of stream length frequently dip below state standards set to ensure survival and reproduction of native salmonids. We examined O2 dynamics on 12 OCR rivers during times of the year when standards had been violated. Continuous dissolved O2 data were collected 15 minutes apart over a 24-hour period during spring (May - June) or fall (September - November) 2008 on each river. We modeled O2 dynamics for each river with parameters describing O2 exchange with the atmosphere, production of O2 from gross primary production (GPP), and consumption of O2 by ecosystem respiration (ER) fit to observed data. Average nighttime atmospheric O2 exchange and ER were estimated by regressing interval changes in dissolved O2 concentrations between measurements with corresponding O2 saturation deficits. GPP for each daytime sampling interval was calculated as the difference between O2 saturation deficit and the sum of temperature-corrected reaeration and ecosystem respiration. All regression models developed for estimating night-time reaeration and ER were highly significant (pbiological processes) ranged from -11.64 to 3.75 mg O2 L-1 d-1 across all rivers and seasons. Increased aquatic productivity resulting from adjacent and upstream human activities likely altered dissolved O2 dynamics in these rivers. Through scenario analysis, we found that at one river (Alsea), GPP and ER would need to be reduced by 85 and 73%, respectively, to meet the state standard (95% saturation). Our modeling approach can be connected with management actions across a variety of spatial and temporal scales, ranging from local, riparian-scale manipulations of shading and organic matter input to watershed and regional nutrient and temperature management.

  11. Effect of arsenic on the activity of oxygen dissolved in dilute liquid copper solutions

    Science.gov (United States)

    Walqui, H.; Seetharaman, S.; Staffansson, L. I.

    1985-06-01

    The influence of arsenic additions on the activity of oxygen in liquid copper was studied by the solid-electrolyte galvanic cell (-) Pt, W/Cu-O-As ∥ ZrO2-CaO ∥ NiO-Ni/Pt (+) in the temperature range 1373 to 1473 K. The activity coefficient of oxygen in liquid copper was found to be unaffected by the addition of arsenic. The interaction parameter values for group V B elements in the periodic table with respect to oxygen are discussed in the light of the solute interactions in copper.

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

    Science.gov (United States)

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

    2015-11-01

    Biomass production by baker's yeast in a fed-batch reactor depends on the metabolic regime determined by the concentration of glucose and dissolved oxygen in the reactor. Achieving high biomass concentration in turn is dependent on the dynamic interaction between the glucose and dissolved oxygen concentration. Taking this into account, we present in this paper the implementation of a decoupled input-output linearizing controller (DIOLC) for maximizing biomass in a fed-batch yeast process. The decoupling is based on the inversion of 2×2 input-output matrix resulting from global linearization. The DIOLC was implemented online using a platform created in LabVIEW employing a TCP/IP protocol via the reactor's built-in electronic system. An improvement in biomass yield by 23% was obtained compared to that using a PID controller. The results demonstrate superior capability of the DIOLC and that the cumulative effect of smoother control action contributes to biomass maximization. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

    Science.gov (United States)

    Di Bella, Gaetano; Torregrossa, Michele

    2013-08-01

    Simultaneous nitrification and denitrification (SND) together with organic removal in granules is usually carried out without Dissolved Oxygen (DO) concentration control, at "low DO" (with a DOoxygen control with big sized granules. More specifically, the paper presents a experimentation focused on the analysis of two Sequencing Batch Reactors (SBRs), in bench scale, working with different aerobic sludge granules, in terms of granule size, and high DO concentration, (with concentration varying from anoxic conditions, about DO ∼0 mg/L, to values close to those of saturation, >7-8 mg/L, during feast and famine conditions respectively). In particular, different strategies of cultivation and several organic and nitrogen loading rate have been applied, in order to evaluate the efficiencies in SND process without dissolved oxygen control. The results show that, even under conditions of high DO concentration, nitrogen and organic matter can be simultaneously removed, with efficiency >90%. Nevertheless, the biological conditions in the inner layer of the granule may change significantly between small and big granules, during the feast and famine periods. From point of view of granule stability, it is also interesting that with a particle size greater than 1.5mm, after the cultivation start-up, the granules are presented stable for a long period (about 100 days) and, despite the variations of operational conditions, the granules breaking was always negligible. Copyright © 2013 Elsevier Ltd. All rights reserved.

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

    Science.gov (United States)

    Okada, Hiroshi; Tanaka, Kazuo; Chujo, Yoshiki

    2014-06-15

    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. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Survival of Campylobacter jejuni in co-culture with Acanthamoeba castellanii: role of amoeba-mediated depletion of dissolved oxygen.

    Science.gov (United States)

    Bui, Xuan Thanh; Winding, Anne; Qvortrup, Klaus; Wolff, Anders; Bang, Dang Duong; Creuzenet, Carole

    2012-08-01

    Campylobacter jejuni is a major cause of infectious diarrhoea worldwide but relatively little is known about its ecology. In this study, we examined its interactions with Acanthamoeba castellanii, a protozoan suspected to serve as a reservoir for bacterial pathogens. We observed rapid degradation of intracellular C.jejuni in A.castellanii 5 h post gentamicin treatment at 25°C. Conversely, we found that A.castellanii promoted the extracellular growth of C.jejuni in co-cultures at 37°C in aerobic conditions. This growth-promoting effect did not require amoebae - bacteria contact. The growth rates observed with or without contact with amoeba were similar to those observed when C.jejuni was grown in microaerophilic conditions. Preconditioned media prepared with live or dead amoebae cultivated with or without C.jejuni did not promote the growth of C.jejuni in aerobic conditions. Interestingly, the dissolved oxygen levels of co-cultures with or without amoebae - bacteria contact were much lower than those observed with culture media or with C.jejuni alone incubated in aerobic conditions, and were comparable with levels obtained after 24 h of growth of C.jejuni under microaerophilic conditions. Our studies identified the depletion of dissolved oxygen by A.castellanii as the major contributor for the observed amoeba-mediated growth enhancement.

  16. Modelling algae growth and dissolved oxygen in the Seine River downstream the Paris urban area: contribution of high frequency measurements

    Science.gov (United States)

    Vilmin, Lauriane; Escoffier, Nicolas; Groleau, Alexis; Poulin, Michel; Flipo, Nicolas

    2014-05-01

    Dissolved oxygen is a key variable in the hydro-ecological functioning of river systems. The accurate representation of the different biogeochemical processes affecting algal blooms and dissolved oxygen in the water column in hydro-ecological models is crucial for the use of these models as reliable management tools. This study focuses on the water quality of the Seine River along a 225 km stretch, from Paris to the Seine estuary. The study area is highly urbanized and located downstream France's largest agricultural area, and therefore receives large amounts of nutrients. During the last decades, nutrient inputs have been significantly reduced, especially with the implementation of new sewage water treatment technologies. Even though the frequency and the intensity of observed algal blooms have decreased, blooms were observed in 2011 and 2012. These blooms are generally followed by a period of high organic matter accumulation, leading to high mineralization fluxes and potential oxygen depletion. The hydrodynamics and the water quality of the Seine River are simulated for the 2011-2012 period with the distributed process-based hydro-ecological model ProSe (Even et al., 1998). The simulated chlorophyll a and dissolved oxygen concentrations are compared to high frequency measurements at the Bougival monitoring station (50 km downstream from Paris), which is part of the CarboSeine monitoring network. The high frequency continuous dataset allows calibrating of primary producers' physiological parameters. New growth parameters are defined for the diatom community. The blooms occur at the end of the winter period (march 2011 and march 2012) and the optimal temperature for diatom growth is calibrated at 10°C, based on an analysis of the physiological response of the diatom community. One of the main outcomes of the modelling exercise is that the precise identification of the constituting communities of algal blooms must be achieved prior to the modelling itself. With the

  17. Distribution and mass transfer of dissolved oxygen in a multi-habitat membrane bioreactor.

    Science.gov (United States)

    Tang, Bing; Qiu, Bing; Huang, Shaosong; Yang, Kanghua; Bin, Liying; Fu, Fenglian; Yang, Huiwen

    2015-04-01

    This work investigated the DO distribution and the factors influencing the mass transfer of DO in a multi-habitat membrane bioreactor. Through the continuous measurements of an on-line automatic system, the timely DO values at different zones in the bioreactor were obtained, which gave a detailed description to the distribution of oxygen within the bioreactor. The results indicated that the growth of biomass had an important influence on the distribution of oxygen. As the extension of operational time, the volumetric oxygen mass transfer coefficient (kLa) was generally decreased. With the difference in DO values, a complex environment combining anoxic and oxic state was produced within a single bioreactor, which provided a fundamental guarantee for the total removal of TN. Aeration rate, the concentration and apparent viscosity of MLSS have different influences on kLa, but adjusting the viscosity is a feasible method to improve the mass transfer of oxygen in the bioreactor.

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

    Science.gov (United States)

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

    2015-01-01

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

  19. The effect of dissolved oxygen concentration (DO) on oxygen diffusion and bacterial community structure in moving bed sequencing batch reactor (MBSBR).

    Science.gov (United States)

    Cao, Yongfeng; Zhang, Chaosheng; Rong, Hongwei; Zheng, Guilin; Zhao, Limin

    2017-01-01

    The effect of dissolved oxygen concentration (DO) on simultaneous nitrification and denitrification was studied in a moving bed sequencing batch reactor (MBSBR) by microelectrode measurements and by real-time PCR. In this system, the biofilm grew on polyurethane foam carriers used to treat municipal sewage at five DO concentrations (1.5, 2.5, 3.5, 4.5 and 5.5 mg/L). The results indicated that the MBSBR exhibited good removal of chemical oxygen demand (92.43%) and nitrogen (83.73%) when DO concentration was 2.5 mg/L. Increasing the oxygen concentration in the reactor was inhibitory to denitrification. Microelectrode measurements showed that the thickness of oxygen penetration increased from 1.2 to 2.6 mm when the DO concentration (from 1.5 mg/L to 5.5 mg/L) in the system increased. Oxygen diffusion was not significantly limited by the boundary layer surrounding the carrier and had the largest slope when DO concentration was 2.5 mg/L. The real-time PCR analysis indicated that the amount of the ammonia-oxidizing bacteria and nitrite-oxidizing bacteria increased slowly as DO concentration increased. The proportions of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria, as a percentage of the total bacteria, were low with average values of 0.063% and 0.67%, respectively. When the DO concentration was 2.5 mg/L, oxygen diffusion was optimal and ensured the optimal bacterial community structure and activity; under these conditions, the MBSBR was efficient for total inorganic nitrogen removal. Changing the DO concentration could alter the aerobic zone and the bacterial community structure in the biofilm, directly influencing the simultaneous nitrification and denitrification activity in MBSBRs. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Electrochemically reduced water exerts superior reactive oxygen species scavenging activity in HT1080 cells than the equivalent level of hydrogen-dissolved water

    Science.gov (United States)

    Hamasaki, Takeki; Harada, Gakuro; Nakamichi, Noboru; Kabayama, Shigeru; Teruya, Kiichiro; Fugetsu, Bunshi; Gong, Wei; Sakata, Ichiro; Shirahata, Sanetaka

    2017-01-01

    Electrochemically reduced water (ERW) is produced near a cathode during electrolysis and exhibits an alkaline pH, contains richly dissolved hydrogen, and contains a small amount of platinum nanoparticles. ERW has reactive oxygen species (ROS)-scavenging activity and recent studies demonstrated that hydrogen-dissolved water exhibits ROS-scavenging activity. Thus, the antioxidative capacity of ERW is postulated to be dependent on the presence of hydrogen levels; however, there is no report verifying the role of dissolved hydrogen in ERW. In this report, we clarify whether the responsive factor for antioxidative activity in ERW is dissolved hydrogen. The intracellular ROS scavenging activity of ERW and hydrogen-dissolved water was tested by both fluorescent stain method and immuno spin trapping assay. We confirm that ERW possessed electrolysis intensity-dependent intracellular ROS-scavenging activity, and ERW exerts significantly superior ROS-scavenging activity in HT1080 cells than the equivalent level of hydrogen-dissolved water. ERW retained its ROS-scavenging activity after removal of dissolved hydrogen, but lost its activity when autoclaved. An oxygen radical absorbance capacity assay, the 2,2-diphenyl-1-picrylhydrazyl assay and chemiluminescence assay could not detect radical-scavenging activity in both ERW and hydrogen-dissolved water. These results indicate that ERW contains electrolysis-dependent hydrogen and an additional antioxidative factor predicted to be platinum nanoparticles. PMID:28182635

  1. Electrochemically reduced water exerts superior reactive oxygen species scavenging activity in HT1080 cells than the equivalent level of hydrogen-dissolved water.

    Science.gov (United States)

    Hamasaki, Takeki; Harada, Gakuro; Nakamichi, Noboru; Kabayama, Shigeru; Teruya, Kiichiro; Fugetsu, Bunshi; Gong, Wei; Sakata, Ichiro; Shirahata, Sanetaka

    2017-01-01

    Electrochemically reduced water (ERW) is produced near a cathode during electrolysis and exhibits an alkaline pH, contains richly dissolved hydrogen, and contains a small amount of platinum nanoparticles. ERW has reactive oxygen species (ROS)-scavenging activity and recent studies demonstrated that hydrogen-dissolved water exhibits ROS-scavenging activity. Thus, the antioxidative capacity of ERW is postulated to be dependent on the presence of hydrogen levels; however, there is no report verifying the role of dissolved hydrogen in ERW. In this report, we clarify whether the responsive factor for antioxidative activity in ERW is dissolved hydrogen. The intracellular ROS scavenging activity of ERW and hydrogen-dissolved water was tested by both fluorescent stain method and immuno spin trapping assay. We confirm that ERW possessed electrolysis intensity-dependent intracellular ROS-scavenging activity, and ERW exerts significantly superior ROS-scavenging activity in HT1080 cells than the equivalent level of hydrogen-dissolved water. ERW retained its ROS-scavenging activity after removal of dissolved hydrogen, but lost its activity when autoclaved. An oxygen radical absorbance capacity assay, the 2,2-diphenyl-1-picrylhydrazyl assay and chemiluminescence assay could not detect radical-scavenging activity in both ERW and hydrogen-dissolved water. These results indicate that ERW contains electrolysis-dependent hydrogen and an additional antioxidative factor predicted to be platinum nanoparticles.

  2. Three-Dimensional Short-Term Prediction Model of Dissolved Oxygen Content Based on PSO-BPANN Algorithm Coupled with Kriging Interpolation

    Directory of Open Access Journals (Sweden)

    Yingyi Chen

    2016-01-01

    Full Text Available Dissolved oxygen (DO content is a significant aspect of water quality in aquaculture. Prediction of dissolved oxygen may timely avoid the financial loss caused by inappropriate dissolved oxygen content and three-dimensional prediction can achieve more accurate and overall guidance. Therefore, this study presents a three-dimensional short-term prediction model of dissolved oxygen in crab aquaculture ponds based on back propagation artificial neural network (BPANN optimized by particle swarm optimization (PSO, which coupled with Kriging method. In this model, wavelet analysis is adopted for denoising, BPANN optimized by PSO is utilized for data analysis and one-dimensional prediction, and Kriging method is used for three-dimensional prediction. Compared with traditional one-dimensional prediction model, three-dimensional model has more real reaction of dissolved oxygen content in crab growth environment. In particular, the merits of PSO are evaluated against genetic algorithm (GA. The root mean square error (RMSE, mean absolute error (MAE, and mean absolute percentage error (MAPE for PSO model are 0.136445, 0.90534, and 0.15384, respectively, while for the GA model the values are 2.04184, 1.18316, and 0.21014, respectively. Furthermore, results of cross validation experiment show that the average error of this model is 0.0705 (mg/L. Consequently, this study suggests that the prediction model operates in a satisfactory manner.

  3. The role of dissolved molecular oxygen in abiotic pyrite oxidation under acid pH conditions - Experiments with {sup 18}O-enriched molecular oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Heidel, Claudia, E-mail: claudia.heidel@gmx.net [Institute of Mineralogy, TU Bergakademie Freiberg, Brennhausgasse 14, 09599 Freiberg (Germany); Tichomirowa, Marion [Institute of Mineralogy, TU Bergakademie Freiberg, Brennhausgasse 14, 09599 Freiberg (Germany)

    2010-11-15

    Research highlights: {yields} A small amount of molecular oxygen is permanently incorporated into sulfate during pyrite oxidation. {yields} Molecular oxygen may be incorporated into sulfate by sulfite oxidation and tetrathionate oxidation. {yields} Molecular oxygen is incorporated into water molecules during its cathodic reduction. {yields} Molecular oxygen mainly accepts electrons from pyrite and minor from dissolved and adsorbed ferrous iron. - Abstract: Several O isotope studies have shown that SO{sub 4}{sup 2-} produced from aqueous pyrite oxidation mainly contains water-derived O and minor atmospherically-derived O{sub 2}. However, the incorporation of O{sub 2} into SO{sub 4}{sup 2-} has been shown to decrease continuously during pyrite oxidation experiments. Hence, it remains uncertain if (and how) O{sub 2} is permanently incorporated into SO{sub 4}{sup 2-} during pyrite oxidation. Abiotic aerobic batch pyrite oxidation experiments in aqueous solutions were performed under acid pH conditions. After 151 days, {sup 18}O-enriched O{sub 2} was injected into the headspace of the reaction vessels. Increasing {delta}{sup 18}O{sub SO{sub 4}} values with increasing injection volume of {sup 18}O-enriched O{sub 2} indicated the permanent incorporation of about 9% O{sub 2} into the produced SO{sub 4}{sup 2-} during pyrite oxidation from 151 to 201 days. Molecular oxygen may be incorporated into SO{sub 4}{sup 2-} by oxidation of the S intermediate species sulfite (and maybe tetrathionate) into SO{sub 4}{sup 2-}. However, only 4% of the O{sub 2} consumed during the experiments was incorporated into SO{sub 4}{sup 2-}. Slightly increased {delta}{sup 18}O{sub H{sub 2}O} values from experiments with the largest injection of {sup 18}O-enriched O{sub 2} indicated the incorporation of O{sub 2} into water molecules which may proceed during the cathodic reduction of O{sub 2}. Thus, O{sub 2} was an important electron acceptor under aerobic acid conditions. The observed {epsilon

  4. LUMOS - A Sensitive and Reliable Optode System for Measuring Dissolved Oxygen in the Nanomolar Range

    DEFF Research Database (Denmark)

    Lehner, Philipp; Larndorfer, Christoph; Garcia-Robledo, Emilio;

    2015-01-01

    Most commercially available optical oxygen sensors target the measuring range of 300 to 2 mu mol L-1. However these are not suitable for investigating the nanomolar range which is relevant for many important environmental situations. We therefore developed a miniaturized phase fluorimeter based m...

  5. Quantitative Aspects of the Interfacial Catalytic Oxidation of Dithiothreitol by Dissolved Oxygen in the Presence of Carbon Nanoparticles.

    Science.gov (United States)

    Sauvain, Jean-Jacques; Rossi, Michel J

    2016-01-19

    The catalytic nature of particulate matter is often advocated to explain its ability to generate reactive oxygen species, but quantitative data are lacking. We have performed molecular characterization of three different carbonaceous nanoparticles (NP) by 1. identifying and quantifying their surface functional groups based on probe gas-particle titration; 2. studying the kinetics of dissolved oxygen consumption in the presence of suspended NP's and dithiothreitol (DTT). We show that these NP's can reversibly change their oxidation state between oxidized and reduced functional groups present on the NP surface. By comparing the amount of O2 consumed and the number of strongly reducing sites on the NP, its average turnover ranged from 35 to 600 depending on the type of NP. The observed quadratic rate law for O2 disappearance points to a Langmuir-Hinshelwood surface-based reaction mechanism possibly involving semiquinone radical. In the proposed model, the strongly reducing surface site is assumed to be a polycyclic aromatic hydroquinone whose oxidation to the corresponding conjugated quinone is rate-limiting in the catalytic chain reaction. The presence and strength of the reducing surface functional groups are important for explaining the catalytic activity of NP in the presence of oxygen and a reducing agent like DTT.

  6. Dynamics of Dissolved Oxygen in Relation to Saturation and Health of an Aquatic Body: A Case for Chilka Lagoon, India

    Directory of Open Access Journals (Sweden)

    B. S. R. V. Prasad

    2014-01-01

    Full Text Available Dissolved oxygen (DO is essential for an aquatic ecosystem since it controls the biological productivity. Here, we propose a unidimensional dynamic model for DO by incorporating biological (photosynthesis, respiration, and mineralization, physical (atmospheric reaeration and chemical (nitrification processes so characteristic of shallow coastal water bodies. The analytical study of the proposed model is focussed on supersaturation and undersaturation of oxygen in the water body. The controllability of the ecosystem health has also been investigated. Model results indicate that, while undersaturation of oxygen is largely governed by nitrification and Net Ecosystem Metabolism (NEM, the supersaturation is controlled by photosynthetic activity. The model results are corroborated with observed data collected from Chilka lagoon, India. Subsequently, a biogeochemical model to study the DO variations in Chilka lagoon has been constructed. The model is properly calibrated and validated with observed data. Two independent sets of data (2004-2005 and 2005-2006 were used for model calibration and validation and Chi-square tests supported its robustness (R2=0.982 and 0.987; P<0.05. The model was used to evaluate independently the influence of individual taxa (diatoms, microphytobenthos, and cyanophyceans on DO variations. Simulations indicate the vital role of microphytobenthos in lagoon DO dynamics and the overall wellbeing.

  7. A Deterministic Model for Predicting Hourly Dissolved Oxygen Change: Development and Application to a Shallow Eutrophic Lake

    Directory of Open Access Journals (Sweden)

    Zhen Xu

    2016-01-01

    Full Text Available Predicting dissolved oxygen (DO change at a high frequency in water bodies is useful for water quality management. In this study, we developed a deterministic model that can predict hourly DO change in a water body with high frequency weather parameters. The study was conducted during August 2008–July 2009 in a eutrophic shallow lake in Louisiana, USA. An environment monitoring buoy was deployed to record DO, water temperature and chlorophyll-a concentration at 15-min intervals, and hourly weather data including air temperature, precipitation, wind speed, relative humidity, and solar radiation were gathered from a nearby weather station. These data formed a foundation for developing a DO model that predicts rapid change of source and sink components including photosynthesis, re-aeration, respiration, and oxygen consumption by sediments. We then applied the model to a studied shallow lake that is widely representative of lake water conditions in the subtropical southern United States. Overall, the model successfully simulated high-time fluctuation of DO in the studied lake, showing good predictability for extreme algal bloom events. However, a knowledge gap still exists in accurately quantifying oxygen source produced by photosynthesis in high frequency DO modeling.

  8. Culture scale-up studies as seen from the viewpoint of oxygen supply and dissolved carbon dioxide stripping.

    Science.gov (United States)

    Matsunaga, Naoki; Kano, Kenjiro; Maki, Yasuyuki; Dobashi, Toshiaki

    2009-04-01

    Oxygen supply and dissolved carbon dioxide (dCO(2)) stripping are two of the most important control parameters in cell culture. In this study, we investigated the effect of scale-up on the volumetric gas transfer coefficient with bioreactors of different sizes (working volume: 80 L, 500 L, 2000 L, and 10,000 L; aspect ratio: 1.0-1.6). Sparging air into water increased the volumetric oxygen transfer coefficient (k(L)a), an index of oxygen supply efficiency, by scale-up roughly in proportion to the depth of the water. A corresponding increase in k(L)a was found in a real cell culture of Chinese hamster ovary cells. dCO(2) stripping efficiency was evaluated in water tests using changes in k(L)a(co2), an index defined in relation to k(L)a. k(L)a(co2) increased following surface aeration, but the rate of increase was reduced by scale-up, which was attributed to a decrease in the liquid surface-to-volume ratio. A similar decrease in efficiency was observed in a 2000 L bioreactor by increasing the liquid volume at constant liquid surface area. The observed scale-up effects are discussed based on a simple theoretical consideration.

  9. A one-dimensional, steady-state, dissolved-oxygen model and waste-load assimilation study for West Fork Blue River, Washington County, Indiana

    Science.gov (United States)

    Peters, James G.; Wilber, W.G.; Crawford, Charles G.; Girardi, F.P.

    1979-01-01

    A digital computer model calibrated to observe stream conditions was used to evaluate water quality in West Fork Blue River, Washington County, IN. Instream dissolved-oxygen concentration averaged 96.5% of saturation at selected sites on West Fork Blue River during two 24-hour summer surveys. This high dissolved-oxygen concentration reflects small carbonaceous and nitrogenous waste loads; adequate dilution of waste by the stream; and natural reaeration. Nonpoint source waste loads accounted for an average of 53.2% of the total carbonaceous biochemical-oxygen demand and 90.2% of the nitrogenous biochemical-oxygen demand. Waste-load assimilation was studiedfor critical summer and winter low flows. Natural streamflow for these conditions was zero, so no benefit from dilution was provided. The projected stream reaeration capacity was not sufficient to maintain the minimum daily dissolved-oxygen concentration (5 milligrams per liter) in the stream with current waste-discharge restrictions. During winter low flow, ammonia toxicity, rather than dissolved-oxygen concentration, was the limiting water-quality criterion downstream from the Salem wastewater-treatment facility. (USGS)

  10. Influence and Control of Dissolved Oxygen on Amino Acid Fermentation%溶氧对氨基酸发酵的影响及其控制

    Institute of Scientific and Technical Information of China (English)

    张夙夙

    2014-01-01

    溶解氧是指溶解于水分子状态的氧。在氨基酸发酵过程中必须提供氧气,菌体才能繁殖和积累所需的代谢产物。研究溶氧对氨基酸发酵的影响及其控制对提高生产效率、改善产品质量等方面有着重要的意义。%Dissolved oxygen refers to the state of the oxygen dissolved in water molecules. Bacteria can on-ly multiply and accumulate the metabolites provided by the appropriate amount of sterile air during the amino acid fermentation.It has important significance to study the influence and control of dissolved oxygen during the amino acid fermentation to improve the production efficiency and quality.

  11. The effect of the oxygen dissolved in the adsorption of gold in activated carbon; Efecto del oxigeno disuelto en la adsorcion de oro en carbon activado

    Energy Technology Data Exchange (ETDEWEB)

    Navarro, P. [Universidad de Santiago. Chile (Chile); Wilkomirsky, I. [Universidad de Concepcion. Chile (Chile)

    1999-07-01

    The effect of the oxygen dissolved on the adsorption of gold in a activated carbon such as these used for carbon in pulp (CIP) and carbon in leach (CIL) processes were studied. The research was oriented to dilucidate the effect of the oxygen dissolved in the gold solution on the kinetics and distribution of the gold adsorbed in the carbon under different conditions of ionic strength, pH and gold concentration. It was found that the level of the oxygen dissolved influences directly the amount of gold adsorbed on the activated carbon, being this effect more relevant for low ionic strength solutions. The pH and initial gold concentration has no effect on this behavior. (Author) 16 refs.

  12. Dissolved oxygen regimen (PO2 may affect osmorespiratory compromise in European sea bass (Dicentrarchus labrax, L.

    Directory of Open Access Journals (Sweden)

    Genciana Terova

    2010-02-01

    Full Text Available Fundamentally, in land based mediterranean aquaculture, two techniques are applied to supply water with oxygen: paddling water aeration and application of pure oxygen. The two oxygenation techniques result in quite different PO2 regimens and, consequently, different fish growth performance and gill morphology. Data exist showing a reduction in total respiratory surface (RSA and increasing gas diffusion distance (GDD in gills of sea bass (Dicentrarchus labrax, L. farmed under elevated PO2 regimens. That such a modification might have an effect on the ion regulation has been defined elsewhere as osmorespiratory compromise. In this study, European sea bass previously acclimatized to two PO2 regimens, mild hypoxia and mild hyperoxia (70-80% and 130-140% of the saturation value, respectively, were challenged for 1 hour with hypo-osmotic plus manipulation stress in two separate trials. During the first trial, when only Na+ loss was determined, the ion efflux during the first 5 min resulted in a rate of 163.72±31 and 112.23±87 nmol g-1min-1 from hypoxia and hyperoxia sea bass groups, respectively, and, if sustained, would approach 15.3 and 11.2% per hour of the total body Na+, respectively. During the second trial, in which both Na+ and Cl- loss were determined, after 60 min the Na+ loss was shown to be 76.86±12 and 179.28±32 nmol g-1 min-1 for the fish previously acclimatized to hyperoxia and hypoxia regimens, respectively, whereas for Cl- this loss was 62.02±11 and 157.28±28 nmol g-1min-1, respectively. Our data are compatible with the hypothesis of an osmotic advantage of sea bass exposed to an elevated PO2 regimen, achievable with application of pure oxygen, instead of simple water aeration.

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

    Science.gov (United States)

    Heddam, Salim

    2014-08-01

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

  14. Regeneration of elemental sulfur in a simultaneous sulfide and nitrate removal reactor under different dissolved oxygen conditions.

    Science.gov (United States)

    Wang, Xiaowei; Zhang, Yu; Zhou, Jiti; Zhang, Tingting; Chen, Mingxiang

    2015-04-01

    A continuous reactor in microaerobic conditions was adopted for sulfide-oxidizing, nitrate-reducing and elemental sulfur (S(0)) regenerating, simultaneously. The results showed that appropriate dissolved oxygen (DO) enhanced S(0) regeneration efficiency, sulfide oxidation efficiency, and nitrate reduction efficiency. When the DO concentration was 0.1-0.3 mg L(-1), the microaerobic bioreactor simultaneously converted 8.16 kg-Sm(-3)d(-1) of sulfide to S(0) and 2.48 kg-Nm(-3)d(-1) of nitrate to nitrogen with the sulfide and nitrate removal efficiency of 100% and 90% respectively. Compared with anaerobic sulfide and nitrate removal process previously reported, the loading sulfide was higher and more S(0) was generated during the operation in microaerobic reactor. Analysis using the 16S rDNA gene clone library revealed that Azoarcus, Thauera, Paracoccus, Sulfurospirillum, Arcobacter and Clostridium were the dominant microorganisms in the sulfide and nitrate removal system.

  15. Sliding mode control of dissolved oxygen in an integrated nitrogen removal process in a sequencing batch reactor (SBR).

    Science.gov (United States)

    Muñoz, C; Young, H; Antileo, C; Bornhardt, C

    2009-01-01

    This paper presents a sliding mode controller (SMC) for dissolved oxygen (DO) in an integrated nitrogen removal process carried out in a suspended biomass sequencing batch reactor (SBR). The SMC performance was compared against an auto-tuning PI controller with parameters adjusted at the beginning of the batch cycle. A method for cancelling the slow DO sensor dynamics was implemented by using a first order model of the sensor. Tests in a lab-scale reactor showed that the SMC offers a better disturbance rejection capability than the auto-tuning PI controller, furthermore providing reasonable performance in a wide range of operation. Thus, SMC becomes an effective robust nonlinear tool to the DO control in this process, being also simple from a computational point of view, allowing its implementation in devices such as industrial programmable logic controllers (PLCs).

  16. Regression model-based predictions of diel, diurnal and nocturnal dissolved oxygen dynamics after wavelet denoising of noisy time series

    Science.gov (United States)

    Evrendilek, F.; Karakaya, N.

    2014-06-01

    Continuous time-series measurements of diel dissolved oxygen (DO) through online sensors are vital to better understanding and management of metabolism of lake ecosystems, but are prone to noise. Discrete wavelet transforms (DWT) with the orthogonal Symmlet and the semiorthogonal Chui-Wang B-spline were compared in denoising diel, daytime and nighttime dynamics of DO, water temperature, pH, and chlorophyll-a. Predictive efficacies of multiple non-linear regression (MNLR) models of DO dynamics were evaluated with or without DWT denoising of either the response variable alone or all the response and explanatory variables. The combined use of the B-spline-based denoising of all the variables and the temporally partitioned data improved both the predictive power and the errors of the MNLR models better than the use of Symmlet DWT denoising of DO only or all the variables with or without the temporal partitioning.

  17. The distribution of nutrients, dissolved oxygen and chlorophyll a in the upper Gulf of Nicoya, Costa Rica, a tropical estuary.

    Science.gov (United States)

    Palter, Jaime; Coto, Sandra León; Ballestero, Daniel

    2007-06-01

    In the Gulf of Nicoya on the Pacific Coast of Costa Rica, nutrient rich equatorial subsurface water (ESW) is upwelled in much of the lower gulf. These offshore waters are often regarded as the major source of nutrients to the gulf. However, for most of the year, the ESW has little influence on the nutrient content of the upper gulf, which has a distinct character from the lower gulf. The upper gulf, extending 40 km north of the restriction between Puntarenas Peninsula and San Lucas Island, is bordered primarily by mangrove swamps, is less than 20 m deep, and is less saline than the lower gulf. We surveyed the upper gulf for dissolved inorganic nitrogen, phosphate, silicate, dissolved oxygen, and chlorophyll in November 2000, January and July 2001. All nutrients are more concentrated in the upper gulf during the rainy and transitional seasons than the dry season, significantly so for phosphate and silicate. Throughout the year, nutrients tend to be much more concentrated in the less saline water of the upper gulf. This trend indicates that discharge from the Tempisque River predominantly controls spatial and temporal nutrient variability in the upper gulf. However, nutrient rich ESW, upwelled offshore and mixed to form a mid-temperature intermediate water, may enter the inner gulf to provide an important secondary source of nutrients during the dry season.

  18. Dissolved oxygen fluctuations in karst spring flow and implications for endemic species: Barton Springs, Edwards aquifer, Texas, USA

    Science.gov (United States)

    Mahler, Barbara J.; Bourgeais, Renan

    2013-01-01

    Karst aquifers and springs provide the dissolved oxygen critical for survival of endemic stygophiles worldwide, but little is known about fluctuations of dissolved oxygen concentrations (DO) and factors that control those concentrations. We investigated temporal variation in DO at Barton Springs, Austin, Texas, USA. During 2006–2012, DO fluctuated by as much as a factor of 2, and at some periods decreased to concentrations that adversely affect the Barton Springs salamander (Eurycea sorosum) (≤4.4 mg/L), a federally listed endangered species endemic to Barton Springs. DO was lowest (≤4.4 mg/L) when discharge was low (≤1 m3/s) and spring water temperature was >21 °C, although not at a maximum; the minimum DO recorded was 4.0 mg/L. Relatively low DO (3/s) and maximum T (22.2 °C). A four-segment linear regression model with daily data for discharge and spring water temperature as explanatory variables provided an excellent fit for mean daily DO (Nash–Sutcliffe coefficient for the validation period of 0.90). DO also fluctuated at short-term timescales in response to storms, and DO measured at 15-min intervals could be simulated with a combination of discharge, spring temperature, and specific conductance as explanatory variables. On the basis of the daily-data regression model, we hypothesize that more frequent low DO corresponding to salamander mortality could result from (i) lower discharge from Barton Springs resulting from increased groundwater withdrawals or decreased recharge as a result of climate change, and (or) (ii) higher groundwater temperature as a result of climate change.

  19. Modelling coupled turbulence - dissolved oxygen dynamics near the sediment-water interface under wind waves and sea swell.

    Science.gov (United States)

    Chatelain, Mathieu; Guizien, Katell

    2010-03-01

    A one-dimensional vertical unsteady numerical model for diffusion-consumption of dissolved oxygen (DO) above and below the sediment-water interface was developed to investigate DO profile dynamics under wind waves and sea swell (high-frequency oscillatory flows with periods ranging from 2 to 30s). We tested a new approach to modelling DO profiles that coupled an oscillatory turbulent bottom boundary layer model with a Michaelis-Menten based consumption model. The flow regime controls both the mean value and the fluctuations of the oxygen mass transfer efficiency during a wave cycle, as expressed by the non-dimensional Sherwood number defined with the maximum shear velocity (Sh). The Sherwood number was found to be non-dependent on the sediment biogeochemical activity (mu). In the laminar regime, both cycle-averaged and variance of the Sherwood number are very low (Sh wave cycle fluctuations that increase with the wave Reynolds number (VAR(Sh) up to 30%). Our computations show that DO mass transfer efficiency under high-frequency oscillatory flows in the turbulent regime are water-side controlled by: (a) the diffusion time across the diffusive boundary layer and (b) diffusive boundary layer dynamics during a wave cycle. As a result of these two processes, when the wave period decreases, the Sh minimum increases and the Sh maximum decreases. Sh values vary little, ranging from 0.17 to 0.23. For periods up to 30s, oxygen penetration depth into the sediment did not show any intra-wave fluctuations. Values for the laminar regime are small (oxygen penetration depth reaches values up to five times larger than those in the laminar regime, becoming asymptotic as the maximum shear velocity increases.

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

    Science.gov (United States)

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

    2013-01-01

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

  1. Dissolved oxygen, COD, nitrogen and phosphorus profiles in a continuous sand filter used for WWTP effluent reclamation.

    Science.gov (United States)

    Xu, Hongbin; Scherrenberg, Sigrid M; van Lier, Jules B

    2012-01-01

    Continuous sand filtration (CSF) offers interesting potential for the extensive treatment of wastewater treatment plant (WWTP) effluents for water reclamation and/or restrictive discharge. Research on concentration profiles over the height of the CSF shows that most bacteriological conversions are restricted to the lower part of the filter bed. Dissolved oxygen (DO) rapidly decreases to below 1 mg/L in the first 0.4 m of the filter bed, applying hydraulic velocities of 12.9 ∼ 14.9 m/h and 10 ∼ 20 mm/min sand velocities, independent of the methanol dosage. The DO decrease agrees with the observed decrease in chemical oxygen demand (COD). At the given operational conditions, NO(x)-N and N-total removal is dedicated to the first 0.9 m of the filter bed. Results show that by optimising the CSF operational conditions the very restrictive effluent N and P values of 2.2 and 0.15 mg/L, respectively, as described in the European Water Framework Directive, can be met.

  2. Preliminary study on the dissolved oxygen distributions and the influential factors in the Daliao River estuary and its adjacent areas

    Institute of Scientific and Technical Information of China (English)

    LEI Kun; MENG Wei; ZHENG Binghui; FU Guo

    2004-01-01

    Dissolved oxygen (DO) concentrations were surveyed in the Daliao River Estuary in autumn to investigate the temporaland spatial trends of DO distributions. The results indicate that DO is weakly stratified in the Yingkou section of theDaliao River Estuary, and remains constant vertically in the areas near and out of the entrance. Horizontally, both in-stantaneous and continuous observations show that the Yingkou section of the Daliao River Estuary is affected by hy-poxic conditions; while no conditions of low DO have been observed in the areas near and out of the entrance.DO-salinity correlations exhibit different controlling factors of DO distributions in different sections of the Daliao Riv-er Estuary. At the upstream part of the Yingkou section of the Daliao River (A1-A4), oxygen demanding materials and the associated biochemical processes are the main factor controlling the DO distribution, but in the lower part of theYingkou section and the area near and out of the entrance (A5-A15), tidal advections are more influential for DO distributions.

  3. Comparison of Artificial Neural Network (ANN Model Development Methods for Prediction of Macroinvertebrate Communities in the Zwalm River Basin in Flanders, Belgium

    Directory of Open Access Journals (Sweden)

    Andy P. Dedecker

    2002-01-01

    Full Text Available Modelling has become an interesting tool to support decision making in water management. River ecosystem modelling methods have improved substantially during recent years. New concepts, such as artificial neural networks, fuzzy logic, evolutionary algorithms, chaos and fractals, cellular automata, etc., are being more commonly used to analyse ecosystem databases and to make predictions for river management purposes. In this context, artificial neural networks were applied to predict macroinvertebrate communities in the Zwalm River basin (Flanders, Belgium. Structural characteristics (meandering, substrate type, flow velocity and physical and chemical variables (dissolved oxygen, pH were used as predictive variables to predict the presence or absence of macroinvertebrate taxa in the headwaters and brooks of the Zwalm River basin. Special interest was paid to the frequency of occurrence of the taxa as well as the selection of the predictors and variables to be predicted on the prediction reliability of the developed models. Sensitivity analyses allowed us to study the impact of the predictive variables on the prediction of presence or absence of macroinvertebrate taxa and to define which variables are the most influential in determining the neural network outputs.

  4. Macroinvertebrate communities associated with macrophyte habitats in a tropical man-made lake (Lake Taabo, Côte d’Ivoire

    Directory of Open Access Journals (Sweden)

    Kouamé M. K.

    2011-02-01

    Full Text Available An ecological study was done on Lake Taabo with the main objective of characterising macroinvertebrate communities associated with the microhabitats created mainly by Eichhornia crassipes and other littoral native macrophytes. We sampled organisms in patches of those aquatic macrophytes. Also, some abiotic variables (temperature, transparency, turbidity, pH, TDS, conductivity, dissolved oxygen, NH$_{4}^{+}$+4, NO$_{3}^{-}$−3, NO$_{2}^{-}$−2, PO$_{4}^{3-}$3−4 and SiO$_{2}^{-}$−2 were measured. Overall, forty-three taxa of macroinvertebrates were identified. Ten of them were exclusively associated with water hyacinth while five were only associated with littoral macrophytes. Macroinvertebrate taxa with some of the highest family richness were Gastropoda, Coleoptera, Heteroptera, Odonata and Diptera. The taxon with highest density in both microhabitats was Chironomidae. Although higher values of taxonomic richness (Rs, the Shannon index (H′ and evenness (J were obtained with the water hyacinth habitat, significant differences between the two microhabitats were not observed. Canonical Correspondence Analysis revealed that samples of E. crassipes collected in the dry season were characterised by Gastropoda and Odonata, as well as higher values of transparency and ammonia-nitrogen. Baetidae, Hydrophilidae, Chironomidae, Ceratopogonidae, Coenagrionidae, Naucoridae and Ostracoda were most abundant in both E. crassipes and littoral macrophyte habitats during the rainy season. This season was characterised by higher levels of nitrates and conductivity.

  5. Altitudinal distribution limits of aquatic macroinvertebrates

    DEFF Research Database (Denmark)

    Madsen, Philip B.; Morabowen, Andrés; Andino, Patricio

    2015-01-01

    altitudinal patterns in population densities, (ii) transplants of the five taxa upstream of their natural altitudinal limit to test the short-term (14days) effect on survival, and (iii) in situ experiments of locomotory activity as a proxy for animal response to relatively small differences in temperature (5...... relatively small differences in temperature and oxygen may produce effects explaining ecological patterns, and depending on the taxon, either water temperature or oxygen saturation, without clear interacting effects, are important drivers of altitudinal limits.......1. Temperature and oxygen are recognised as the main drivers of altitudinal limits of species distributions. However, the two factors are linked, and both decrease with altitude, why their effects are difficult to disentangle. 2. This was experimentally addressed using aquatic macroinvertebrates...

  6. Dissolved oxygen analysis, TMDL model comparison, and particulate matter shunting—Preliminary results from three model scenarios for the Klamath River upstream of Keno Dam, Oregon

    Science.gov (United States)

    Sullivan, Annett B.; Rounds, Stewart A.; Deas, Michael L.; Sogutlugil, I. Ertugrul

    2012-01-01

    Efforts are underway to identify actions that would improve water quality in the Link River to Keno Dam reach of the Upper Klamath River in south-central Oregon. To provide further insight into water-quality improvement options, three scenarios were developed, run, and analyzed using previously calibrated CE-QUAL-W2 hydrodynamic and water-quality models. Additional scenarios are under development as part of this ongoing study. Most of these scenarios evaluate changes relative to a "current conditions" model, but in some cases a "natural conditions" model was used that simulated the reach without the effect of point and nonpoint sources and set Upper Klamath Lake at its Total Maximum Daily Load (TMDL) targets. These scenarios were simulated using a model developed by the U.S. Geological Survey (USGS) and Watercourse Engineering, Inc. for the years 2006–09, referred to here as the "USGS model." Another model of the reach was developed by Tetra Tech, Inc. for years 2000 and 2002 to support the Klamath River TMDL process; that model is referred to here as the "TMDL model." The three scenarios described in this report included (1) an analysis of whether this reach of the Upper Klamath River would be in compliance with dissolved oxygen standards if sources met TMDL allocations, (2) an application of more recent datasets to the TMDL model with comparison to results from the USGS model, and (3) an examination of the effect on dissolved oxygen in the Klamath River if particulate material were stopped from entering Klamath Project diversion canals. Updates and modifications to the USGS model are in progress, so in the future these scenarios will be reanalyzed with the updated model and the interim results presented here will be superseded. Significant findings from this phase of the investigation include: * The TMDL analysis used depth-averaged dissolved oxygen concentrations from model output for comparison with dissolved oxygen standards. The Oregon dissolved oxygen

  7. Use of Benthic Macroinvertebrates to Evaluate Stream Water Quality in Trinidad and Tobago, West Indies

    Science.gov (United States)

    Maharaj, L. D.; Alkins-Koo, M.

    2005-05-01

    In order to determine the best method of using benthic macroinvertebrates to monitor water quality in Trinidad and Tobago, 63 sites along 38 streams were sampled in each of the wet and dry seasons from 1999-2001. At each site, 5 benthic samples were collected with a 300μm 'D' frame kicknet, along with data for 14 environmental parameters and habitat data. Principal Components Analyses separated the streams into 3 ecoregions based on substrate type and discharge. Using ANOVA, mean values for each environmental parameter were compared across each ecoregion. Values of dissolved Oxygen, BOD-5, nitrates, total suspended solids and pH varied significantly during the wet season, while dissolved Oxygen, pH and chlorophyll-a varied significantly during the dry. Using PRIMER version 5, non-metric multi-dimensional scaling and cluster analyses were performed on the faunal data for each ecoregion separately and for all sites combined. These analyses indicate that the fauna associated with minimally, moderately and severely impaired sites is similar across all 3 ecoregions. Of the different metrics compared during the study, a modified version of the Average Score Per Taxon (ASPT) best fit the clusters were produced.

  8. Effect of dissolved oxygen on redox potential and milk acidification by lactic acid bacteria isolated from a DL-starter culture

    DEFF Research Database (Denmark)

    Larsen, Nadja; Werner, Birgit Brøsted; Vogensen, Finn Kvist

    2015-01-01

    was to investigate the effect of dissolved oxygen on acidification kinetics and redox potential during milk fermentation by lactic acid bacteria (LAB). Fermentations were conducted by single strains isolated from mixed DL-starter culture, including Lactococcus lactis ssp. lactis, Lactococcus lactis ssp. cremoris...

  9. Cryptic flows: using multiple tracers to relate dissolved oxygen to hyporheic and groundwater flowpaths in intermittent salmonid streams

    Science.gov (United States)

    Woelfle-Erskine, C. A.; Larsen, L.; Gomez-Velez, J. D.

    2016-12-01

    Intermittent streams provide important habitat for aquatic species, including endangered salmonid fishes, but during prolonged dry periods may become depleted in dissolved oxygen (DO). The rate of depletion and the consequent length of time a pool remains habitable depend on DO and carbon concentrations in groundwater and hyporheic flow, and within-pool metabolic rates. We performed repeat surveys, habitat characterization, and ecohydrologic sampling on two intermittent tributaries of Salmon Creek (Sonoma Co., CA) to elucidate controls on salmonid over-summer survival at the pool scale. Pools exhibited heterogeneity within and across stream reaches in salmonid recruitment and survival during the summer dry period. In classification tree analysis, high conductivity (>310 mS/cm) and low DO (concentration. To distinguish between surface, hyporheic, and groundwater contributions, we measured dissolved organic carbon (DOC) concentration and fluorescence excitation-emission matrices (EEMs), radon (222Rn), and stable isotopes (18O and D) in pools, hyporheic flow, and wells and springs in local aquifers. Radon concentrations in pools ranged from 1.5-2.3 Bq/l, 3-4 orders of magnitude higher than expected for water in equilibrium with air, suggesting substantial groundwater inflow. We developed a five-component PARAFAC model from the EEMs and used with the isotope data to perform an end-member mixing analysis to track water sources and flowpaths. These analyses suggested high separability among groundwaters from aquifers separated by faults and between groundwater and surface water, with groundwater of different age and flowpath length discharging to different pools. Pools with shallow groundwater or hyporheic flow sustained DO concentrations above the threshold for salmonid survival, with shallow groundwater unexpectedly acting as a source of DO to the stream. These inflows were further essential for inhibiting stagnation and promoting reaeration across the air

  10. Metal concentrations in water column, benthic macroinvertebrates ...

    African Journals Online (AJOL)

    With the exception of pH, dissolved oxygen, turbidity and biochemical ... With the exception of manganese, water sample had the lowest values of metal detected. ... and cadmium in the fish is of serious health concern to human consumers.

  11. The assemblage characteristics of benthic macroinvertebrates in the Yalutsangpo River, the highest major river in the world

    Science.gov (United States)

    Xu, Mengzhen; Wang, Zhaoyin; Pan, Baozhu; Yu, Guoan

    2014-09-01

    Aquatic ecosystems of highland rivers are different from those of low altitude rivers because of the specific topography and environmental parameters associated with high altitudes. Yalutsangpo, the upper course of the Brahmaputra River, is the highest major river in the world, flowing from west to east across Tibet, China and pouring into India. Macroinvertebrates were sampled from Yalutsangpo and its tributaries, the Lhasa, Niyang, and Parlong Tsangpo Rivers, from October 2009 to June 2010, to study characters of the highland aquatic ecosystem. Altogether, 110 macroinvertebrate taxa belonging to 57 families and 102 genera were identified from the basin. The biodiversity and composition of macroinvertebrate assemblages were strongly affected by altitude gradients. Local diversity represented by taxa richness and the improved Shannon-Wiener index were high at altitudes of 3,300-3,700 m, among which suitability of habitat was higher due to the better integrated environmental conditions of water temperature, dissolved oxygen, and aquatic vegetation, etc. Macroinvertebrates were grouped into shredders, scrapers, predators, collector-filterers, and collector-gatherers according to their feeding behaviors. It was found that the distributions of the functional feeding groups varied with habitat altitudes. Shredders were present at altitudes of 2,900-4,400 m, while scrapers mainly inhabited altitudes of 3,500-4,500 m, and collector-filterers preferred 3,500-4,000 m. Even though the local taxa richness was not high at each site, the taxonomic composition and density of the assemblages varied greatly among the different sites, resulting in much higher regional diversity compared to the lowland river with similar flow and substrate conditions. The regional cumulative taxa richness of Yalutsangpo decreased and more families were lost as the altitude increased. However, some families that were newly present as the altitude increased were essential for sustaining the high

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

    Science.gov (United States)

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

    2016-04-01

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

  13. Effect of Dissolved Oxygen, Temperature, Initial Cell Count, and Sugar Concentration on the Viability of Saccharomyces cerevisiae in Rapid Fermentations1

    Science.gov (United States)

    Nagodawithana, Tilak W.; Castellano, Carmine; Steinkraus, Keith H.

    1974-01-01

    By using 7 × 108 cells of Saccharomyces cerevisiae per ml with which 25° Brix honey solutions were fermented to 9.5% (wt/vol; 12% vol/vol) ethanol in 2.5 to 3 h at 30 C, i.e., rapid fermentation, the death rate was found to be high, with only 2.1% of the yeast cells surviving at the end of 3 h under anaerobic conditions. As the dissolved oxygen in the medium was increased from 0 to 13 to 20 to 100% in rapid fermentations at 30 C, there was a progressive increase in the percentage of cells surviving. The ethanol production rate and total were not seriously affected by a dissolved oxygen concentration of 13%, but fermentation was retarded by 20% dissolved oxygen and still further decreased as the dissolved oxygen content reached 100%. When the fermentation temperature was decreased to 15 C (at 13% dissolved oxygen), the rate of fermentation decreased, and the fermentation time to 9.5% ethanol (wt/vol) increased to 6 h. It was found that the higher the temperature between 15 and 30 C, the greater the rate of death as initial cell counts were increased from 1.1 × 107 to 7.8 × 108 cells per ml. At the lowest level of inoculum, 1.1 × 107 cells per ml, there was actual multiplication, even at 30 C; however, the fermentation was no longer rapid. The addition of 15% sugar, initially followed after an hour by the remaining 10%, or addition of the sugar in increments of 2.5 or 5% yielded a better survival rate of yeast cells than when the fermentation was initiated with 25% sugar. PMID:4607742

  14. The design and fabrication of three-chamber microscale cell culture analog devices with integrated dissolved oxygen sensors.

    Science.gov (United States)

    Sin, Aaron; Chin, Katherine C; Jamil, Muhammad F; Kostov, Yordan; Rao, Govind; Shuler, Michael L

    2004-01-01

    Whole animal testing is an essential part in evaluating the toxicological and pharmacological profiles of chemicals and pharmaceuticals, but these experiments are expensive and cumbersome. A cell culture analog (CCA) system, when used in conjunction with a physiologically based pharmacokinetic (PBPK) model, provides an in vitro supplement to animal studies and the possibility of a human surrogate for predicting human response in clinical trials. A PBPK model mathematically simulates animal metabolism by modeling the absorption, distribution, metabolism, and elimination kinetics of a chemical in interconnected tissue compartments. A CCA uses mammalian cells cultured in interconnected chambers to physically represent the corresponding PBPK. These compartments are connected by recirculating tissue culture medium that acts as a blood surrogate. The purpose of this article is to describe the design and basic operation of the microscale manifestation of such a system. Microscale CCAs offer the potential for inexpensive, relatively high throughput evaluation of chemicals while minimizing demand for reagents and cells. Using microfabrication technology, a three-chamber ("lung"-"liver"-"other") microscale cell culture analog (microCCA) device was fabricated on a 1 in. (2.54 cm) square silicon chip. With a design flow rate of 1.76 microL/min, this microCCA device achieves approximate physiological liquid-to-cell ratio and hydrodynamic shear stress while replicating the liquid residence time parameters in the PBPK model. A dissolved oxygen sensor based on collision quenching of a fluorescent ruthenium complex by oxygen molecules was integrated into the system, demonstrating the potential to integrate real-time sensors into such devices.

  15. Effect of dissolved oxygen on elemental sulfur generation in sulfide and nitrate removal process: characterization, pathway, and microbial community analysis.

    Science.gov (United States)

    Wang, Xiaowei; Zhang, Yu; Zhang, Tingting; Zhou, Jiti

    2016-03-01

    Microaerobic bioreactor treatment for enriched sulfide and nitrate has been demonstrated as an effective strategy to improve the efficiencies of elemental sulfur (S(0)) generation, sulfide oxidation, and nitrate reduction. However, there is little detailed information for the effect and mechanism of dissolved oxygen (DO) on the variations of microbial community in sulfur generation, sulfide oxidation, and nitrate reduction systems. Polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) was employed to evaluate the variations of microbial community structures in a sulfide oxidation and nitrate reduction reactor under different DO conditions (DO 0-0.7 mg · L(-1)). Experimental results revealed that the activity of sulfide-oxidizing bacteria (SOB) and nitrate-reducing bacteria (NRB) could be greatly stimulated in 0.1-0.3 mg-DO · L(-1). However, when the DO concentration was further elevated to more than 0.5 mg · L(-1), the abundance of NRB was markedly decreased, while the heterotrophic microorganisms, especially carbon degradation species, were enriched. The reaction pathways for sulfide and nitrate removal under microaerobic conditions were also deduced by combining batch experiments with functional species analysis. It was likely that the oxidation of sulfide to sulfur could be performed by both aerobic heterotrophic SOB and sulfur-based autotrophic denitrification bacteria with oxygen and nitrate as terminal electron acceptor, respectively. The nitrate could be reduced to nitrite by both autotrophic and heterotrophic denitrification, and then the generated nitrite could be completely converted to nitrogen gas via heterotrophic denitrification. This study provides new insights into the impacts of microaerobic conditions on the microbial community functional structures of sulfide-oxidizing, nitrate-reducing, and sulfur-producing bioreactors, which revealing the potential linkage between functional microbial communities and

  16. Heterogeneous conditions in dissolved oxygen affect N-glycosylation but not productivity of a monoclonal antibody in hybridoma cultures.

    Science.gov (United States)

    Serrato, J Antonio; Palomares, Laura A; Meneses-Acosta, Angélica; Ramírez, Octavio T

    2004-10-20

    It is known that heterogeneous conditions exist in large-scale animal cell cultures. However, little is known about how heterogeneities affect cells, productivities, and product quality. To study the effect of non-constant dissolved oxygen tension (DOT), hybridomas were subjected to sinusoidal DOT oscillations in a one-compartment scale-down simulator. Oscillations were forced by manipulating the inlet oxygen partial pressure through a feedback control algorithm in a 220-mL bioreactor maintained at a constant agitation. Such temporal DOT oscillations simulate spatial DOT gradients that can occur in large scales. Different oscillation periods, in the range of 800 to 12,800 s (axis of 7% (air saturation) and amplitude of 7%), were tested and compared to constant DOT (10%) control cultures. Oscillating DOT decreased maximum cell concentrations, cell growth rates, and viability indexes. Cultures at oscillating DOT had an increased glycolytic metabolism that was evidenced by a decrease in yield of cells on glucose and an increase in lactate yield. DOT gradients, even several orders of magnitude higher than those expected under practical large-scale conditions, did not significantly affect the maximum concentration of an IgG(1) monoclonal antibody (MAb). The glycosylation profile of the MAb produced at a constant DOT of 10% was similar to that reported in the literature. However, MAb produced under oscillating culture conditions had a higher amount of triantennary and sialylated glycans, which can interfere with effector functions of the antibody. It was shown that transient excursions of hybridomas to limiting DOT, as occurs in deficiently mixed large-scale bioreactors, is important to culture performance as the oscillation period, and thus the time cells spent at low DOT, affected cell growth, metabolism, and the glycosylation pattern of MAb. Such results underline the importance of monitoring protein characteristics for the development of large-scale processes.

  17. Impact of oxygen dissolved at bottling and transmitted through closures on the composition and sensory properties of a Sauvignon Blanc wine during bottle storage.

    Science.gov (United States)

    Lopes, Paulo; Silva, Maria A; Pons, Alexandre; Tominaga, Takatoshi; Lavigne, Valérie; Saucier, Cédric; Darriet, Philippe; Teissedre, Pierre-Louis; Dubourdieu, Denis

    2009-11-11

    This work outlines the results from an investigation to determine the effect of the oxygen dissolved at bottling and the specific oxygen barrier properties of commercially available closures on the composition, color and sensory properties of a Bordeaux Sauvignon Blanc wine during two years of storage. The importance of oxygen for wine development after bottling was also assessed using an airtight bottle ampule. Wines were assessed for the antioxidants (SO(2) and ascorbic acid), varietal thiols (4-mercapto-4-methylpentan-2-one, 3-mercaptohexan-1-ol), hydrogen sulfide and sotolon content, and color throughout 24 months of storage. In addition, the aroma and palate properties of wines were also assessed. The combination of oxygen dissolved at bottling and the oxygen transferred through closures has a significant effect on Sauvignon Blanc development after bottling. Wines highly exposed to oxygen at bottling and those sealed with a synthetic, Nomacorc classic closure, highly permeable to oxygen, were relatively oxidized in aroma, brown in color, and low in antioxidants and volatile compounds compared to wines sealed with other closures. Conversely, wines sealed under more airtight conditions, bottle ampule and screw cap Saran-tin, have the slowest rate of browning, and displayed the greatest contents of antioxidants and varietal thiols, but also high levels of H(2)S, which were responsible for the reduced dominating character found in these wines, while wines sealed with cork stoppers and screw cap Saranex presented negligible reduced and oxidized characters.

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

    Science.gov (United States)

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

    2013-09-01

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

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

    Science.gov (United States)

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

    2010-10-01

    To evaluate the effects of dissolved oxygen (DO) control strategy on cell growth and the production of antibiotic (cyclo(2-Me-BABA-Gly)) by Xenorhabdus nematophila. The effects of different agitation speeds and DO concentrations on cell growth and antibiotic activity of X. nematophila YL001 were examined. Experiments showed that higher agitation speeds and DO concentrations at earlier fermentation stage were favorable for cell growth and antibiotic production. At mid- and later-stage, properly decreasing DO concentration can strengthen cell growth and antibiotic production. Based on the kinetic information about the effects of agitation speeds and DO concentrations on the fermentation, the two-stage DO control strategy in which DO concentration was controlled to 70% in the first 18 h, and then switched to 50% after 18 h, was established to improve the biomass and antibiotic activity. By applying this DO-shift strategy in X. nematophila YL001 fermentation, maximal antibiotic activity and biomass reached 252.0+/-6.10 U/mL and 30.04+/-2.50 g/L, respectively, thus was 18.99% and 15.36% more than in the cultures at constantly 50% DO. Copyright 2010 Elsevier Ltd. All rights reserved.

  20. Effects of dissolved oxygen concentration on photosynthetic bacteria wastewater treatment: Pollutants removal, cell growth and pigments production.

    Science.gov (United States)

    Meng, Fan; Yang, Anqi; Zhang, Guangming; Wang, Hangyao

    2017-10-01

    Dissolved oxygen (DO) is an important parameter in photosynthetic bacteria (PSB) wastewater treatment. This study set different DO levels and detected the pollutants removal, PSB growth and pigments production. Results showed that DO significantly influenced the performances of PSB wastewater treatment process. The highest COD (93%) and NH3-N removal (83%) was achieved under DO of 4-8mg/L, but DO of 2-4mg/L was recommended considering the aeration cost. PSB biomass reached 1645mg/L under DO of 4-8mg/L with satisfying co-enzyme Q10 content. The biomass yield was relatively stable at all DO levels. For bacteriochlorophyll and carotenoids, DO>1mg/L could satisfy their production. On the other hand, DO<0.5mg/L led to the highest dehydrogenase activity. According to the different purposes, the optimal treatment time was different. The most pigments production occurred at 24h; biomass reached peak at 48h; and the optimal time for pollutants removal was 72h. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

    Science.gov (United States)

    Heddam, Salim

    2014-01-01

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

  2. Impact of microbial physiology and microbial community structure on pharmaceutical fate driven by dissolved oxygen concentration in nitrifying bioreactors.

    Science.gov (United States)

    Stadler, Lauren B; Love, Nancy G

    2016-11-01

    Operation at low dissolved oxygen (DO) concentrations (concentration can impact pharmaceutical biotransformation rates during wastewater treatment both directly and indirectly: directly by acting as a limiting substrate that slows the activity of the microorganisms involved in biotransformation; and indirectly by shaping the microbial community and selecting for a community that performs pharmaceutical biotransformation faster (or slower). In this study, nitrifying bioreactors were operated at low (∼0.3 mg/L) and high (>4 mg/L) DO concentrations to understand how DO growth conditions impacted microbial community structure. Short-term batch experiments using the biomass from the parent reactors were performed under low and high DO conditions to understand how DO concentration impacts microbial physiology. Although the low DO parent biomass had a lower specific activity with respect to ammonia oxidation than the high DO parent reactor biomass, it had faster biotransformation rates of ibuprofen, sulfamethoxazole, 17α-ethinylestradiol, acetaminophen, and atenolol in high DO batch conditions. This was likely because the low DO reactor had a 2x higher biomass concentration, was enriched for ammonia oxidizers (4x higher concentration), and harbored a more diverse microbial community (3x more unique taxa) as compared to the high DO parent reactor. Overall, the results show that there can be indirect benefits from low DO operation over high DO operation that support pharmaceutical biotransformation during wastewater treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

    Science.gov (United States)

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

    2014-04-01

    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.

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

    Science.gov (United States)

    Rongsayamanont, Chaiwat; Limpiyakorn, Tawan; Khan, Eakalak

    2014-07-01

    An entrapment of nitrifiers into gel matrix is employed as a tool to fulfill partial nitrification under non-limiting dissolved oxygen (DO) concentrations in bulk solutions. This study aims to clarify which of these two attributes, inoculum type and DO concentration in bulk solutions, is the decisive factor for partial nitrification in an entrapped-cell based system. Four polyvinyl alcohol entrapped inocula were prepared to have different proportions of nitrite-oxidizing bacteria (NOB) and nitrite-oxidizing activity. At a DO concentration of 3 mg l(-1), the number of active NOB cells in an inoculum was the decisive factor for partial nitrification enhancement. However, when the DO concentration was reduced to 2 mg l(-1), all entrapped cell inocula showed similar degrees of partial nitrification. The results suggested that with the lower bulk DO concentration, the preparation of entrapped cell inocula is not useful as the DO level becomes the decisive factor for achieving partial nitrification. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Removal of chemical oxygen demand and dissolved nutrients by a sunken lawn infiltration system during intermittent storm events.

    Science.gov (United States)

    Hou, Lizhu; Yang, Huan; Li, Ming

    2014-01-01

    Urban surface water runoff typically contains high but varying amounts of organic matter and nutrients that require removal before reuse. Infiltration systems such as sunken lawns can improve water quality. However, there is currently insufficient information describing the treatment efficiency of lawn-based infiltration systems. In this study, novel sunken lawn infiltration systems (SLISs) were designed and their pollutant removal effectiveness was assessed. The results revealed that SLISs with Poa pratensis and Lolium perenne effectively removed most chemical oxygen demand (CODCr) and dissolved nutrients. Average CODCr, total nitrogen (TN), ammonium-nitrogen (NH4(+)-N) and total phosphorus (TP) concentrations were reduced by 78.93, 66.64, 71.86 and 75.83%, respectively, and the corresponding effluent concentrations met the standard for urban miscellaneous water consumption in China. The NH4(+)-N in the synthetic runoff was shown to be removed by adsorption during the stormwater dosing and nitrification during subsequent dry days, as well as through uptake by plants. Phosphorus was mainly removed by adsorption and chemical precipitation. The NH4(+)-N and phosphorus Langmuir isotherm model fitted the clay loam soil adsorption process better than the Freundlich model. Overall, these results indicate that an SLIS provides an alternative means of removing runoff pollutants owing to its efficiency, easy operation and maintenance.

  6. Flow field and dissolved oxygen distributions in the outer channel of the Orbal oxidation ditch by monitor and CFD simulation

    Institute of Scientific and Technical Information of China (English)

    Xuesong Guo; Xin Zhou; Qiuwen Chen; Junxin Liu

    2013-01-01

    In the Orbal oxidation ditch,denitrification is primarily accomplished in the outer channel.However,the detailed characteristics of the flow field and dissolved oxygen (DO) distribution in the outer channel are not well understood.Therefore,in this study,the flow velocity and DO concentration in the outer channel of an Orbal oxidation ditch system in a wastewater treatment plant in Beijing (China)were monitored under actual operation conditions.The flow field and DO concentration distributions were analyzed by computed fluid dynamic modeling.In situ monitoring and modeling both showed that the flow velocity was heterogeneous in the outer channel.As a result,the DO was also heterogeneously distributed in the outer channel,with concentration gradients occurring along the flow direction as well as in the cross-section.This heterogeneous DO distribution created many anoxic and aerobic zones,which may have facilitated simultaneous nitrification-denitrification in the channel.These findings may provide supporting information for rational optimization of the oerformance of the Orbal oxidation ditch.

  7. Effects of Dissolved Oxygen Tension and Ammonium Concentration on Polyhydroxybutyrate Synthesis from Cassava Starch by Bacillus cereus IFO 13690

    Directory of Open Access Journals (Sweden)

    Margono .

    2015-11-01

    Full Text Available generated by an Adobe application 11.5606 Attempting to get low price of raw material for producing polyhydroxybutyrate is always studied. Tapioca starch is one of the raw material with low price. The objective of this research was to study the effects of initial ammonium concentration and dissolved oxygen tension (doT on producing PHB by Bacillus cereus IFO 13690 with tapioca starch as the carbon source. This fermentation was carried out in 5 L fementors with a 2 L working volume, temperature of 30 oC, and agitation of 500 rpm. The pH medium was controlled at 5.6 after it came down from the initial pH of 6.8. Meanwhile, the initial doT was 100 % air saturation and also came down to and maintained at doT of experiment, i.e. 1 , 5 , or 10 % air saturation. The best result was obtained when the initial ammonium concentration was 5 g/L and the doT value maintained at 5 % air saturation. By this conditions, the cell growth reached 5,457 g cell dry weight/L containing PHB of 2.42 % cell dry weigh after 29 hours fermentation. Normal 0 36 false false false

  8. Novel probes for pH and dissolved oxygen measurements in cultivations from millilitre to benchtop scale.

    Science.gov (United States)

    Demuth, Caspar; Varonier, Joel; Jossen, Valentin; Eibl, Regine; Eibl, Dieter

    2016-05-01

    pH value and the concentration of dissolved oxygen (DO) are key parameters to monitor and control cell growth in cultivation studies. Reliable, robust and accurate methods to measure these parameters in cultivation systems in real time guarantee high product yield and quality. This mini-review summarises the current state of the art of pH and DO sensors that are applied to bioprocesses from millilitre to benchtop scale by means of a short introduction on measuring principles and selected applications. Special emphasis is placed on single-use bioreactors, which have been increasingly employed in bioprocess development and production in recent years. Working principles, applications and the particular requirements of sensors in these cultivation systems are given. In such processes, optical sensors for pH and DO are often preferred to electrochemical probes, as they allow semi-invasive measurements and can be miniaturised to micrometre scale or lower. In addition, selected measuring principles of novel sensing technologies for pH and DO are discussed. These include solid-state sensors and miniaturised devices that are not yet commercially available, but show promising characteristics for possible use in bioprocesses in the near future.

  9. Analytical approaches used in stream benthic macroinvertebrate biomonitoring programs of State agencies in the United States

    Science.gov (United States)

    Carter, James L.; Resh, Vincent H.

    2013-01-01

    Biomonitoring programs based on benthic macroinvertebrates are well-established worldwide. Their value, however, depends on the appropriateness of the analytical techniques used. All United States State, benthic macroinvertebrate biomonitoring programs were surveyed regarding the purposes of their programs, quality-assurance and quality-control procedures used, habitat and water-chemistry data collected, treatment of macroinvertebrate data prior to analysis, statistical methods used, and data-storage considerations. State regulatory mandates (59 percent of programs), biotic index development (17 percent), and Federal requirements (15 percent) were the most frequently reported purposes of State programs, with the specific tasks of satisfying the requirements for 305b/303d reports (89 percent), establishment and monitoring of total maximum daily loads, and developing biocriteria being the purposes most often mentioned. Most states establish reference sites (81 percent), but classify them using State-specific methods. The most often used technique for determining the appropriateness of a reference site was Best Professional Judgment (86 percent of these states). Macroinvertebrate samples are almost always collected by using a D-frame net, and duplicate samples are collected from approximately 10 percent of sites for quality assurance and quality control purposes. Most programs have macroinvertebrate samples processed by contractors (53 percent) and have identifications confirmed by a second taxonomist (85 percent). All States collect habitat data, with most using the Rapid Bioassessment Protocol visual-assessment approach, which requires ~1 h/site. Dissolved oxygen, pH, and conductivity are measured in more than 90 percent of programs. Wide variation exists in which taxa are excluded from analyses and the level of taxonomic resolution used. Species traits, such as functional feeding groups, are commonly used (96 percent), as are tolerance values for organic pollution

  10. Mismatch between observed and modeled trends in dissolved upper-ocean oxygen over the last 50 yr

    Directory of Open Access Journals (Sweden)

    L. Stramma

    2012-10-01

    Full Text Available Observations and model runs indicate trends in dissolved oxygen (DO associated with current and ongoing global warming. However, a large-scale observation-to-model comparison has been missing and is presented here. This study presents a first global compilation of DO measurements covering the last 50 yr. It shows declining upper-ocean DO levels in many regions, especially the tropical oceans, whereas areas with increasing trends are found in the subtropics and in some subpolar regions. For the Atlantic Ocean south of 20° N, the DO history could even be extended back to about 70 yr, showing decreasing DO in the subtropical South Atlantic. The global mean DO trend between 50° S and 50° N at 300 dbar for the period 1960 to 2010 is –0.066 μmol kg−1 yr−1. Results of a numerical biogeochemical Earth system model reveal that the magnitude of the observed change is consistent with CO2-induced climate change. However, the pattern correlation between simulated and observed patterns of past DO change is negative, indicating that the model does not correctly reproduce the processes responsible for observed regional oxygen changes in the past 50 yr. A negative pattern correlation is also obtained for model configurations with particularly low and particularly high diapycnal mixing, for a configuration that assumes a CO2-induced enhancement of the C : N ratios of exported organic matter and irrespective of whether climatological or realistic winds from reanalysis products are used to force the model. Depending on the model configuration the 300 dbar DO trend between 50° S and 50° N is −0.027 to –0.047 μmol kg−1 yr−1 for climatological wind forcing, with a much larger range of –0.083 to +0.027 μmol kg−1 yr−1 for different initializations of sensitivity runs with reanalysis wind forcing. Although numerical models reproduce the overall sign and, to

  11. Dissolved Oxygen Sensor in Animal-Borne Instruments: An Innovation for Monitoring the Health of Oceans and Investigating the Functioning of Marine Ecosystems.

    Directory of Open Access Journals (Sweden)

    Frederic Bailleul

    Full Text Available The current decline in dissolved oxygen concentration within the oceans is a sensitive indicator of the effect of climate change on marine environment. However the impact of its declining on marine life and ecosystems' health is still quite unclear because of the difficulty in obtaining in situ data, especially in remote areas, like the Southern Ocean (SO. Southern elephant seals (Mirounga leonina proved to be a relevant alternative to the traditional oceanographic platforms to measure physical and biogeochemical structure of oceanic regions rarely observed. In this study, we use a new stage of development in biologging technology to draw a picture of dissolved oxygen concentration in the SO. We present the first results obtained from a dissolved oxygen sensor added to Argos CTD-SRDL tags and deployed on 5 female elephant seals at Kerguelen. From October 2010 and October 2011, 742 oxygen profiles associated with temperature and salinity measurements were recorded. Whether a part of the data must be considered cautiously, especially because of offsets and temporal drifts of the sensors, the range of values recorded was consistent with a concomitant survey conducted from a research vessel (Keops-2 project. Once again, elephant seals reinforced the relationship between marine ecology and oceanography, delivering essential information about the water masses properties and the biological status of the Southern Ocean. But more than the presentation of a new stage of development in animal-borne instrumentation, this pilot study opens a new field of investigation in marine ecology and could be enlarged in a near future to other key marine predators, especially large fish species like swordfish, tuna or sharks, for which dissolved oxygen is expected to play a crucial role in distribution and behaviour.

  12. Dissolved Oxygen Sensor in Animal-Borne Instruments: An Innovation for Monitoring the Health of Oceans and Investigating the Functioning of Marine Ecosystems.

    Science.gov (United States)

    Bailleul, Frederic; Vacquie-Garcia, Jade; Guinet, Christophe

    2015-01-01

    The current decline in dissolved oxygen concentration within the oceans is a sensitive indicator of the effect of climate change on marine environment. However the impact of its declining on marine life and ecosystems' health is still quite unclear because of the difficulty in obtaining in situ data, especially in remote areas, like the Southern Ocean (SO). Southern elephant seals (Mirounga leonina) proved to be a relevant alternative to the traditional oceanographic platforms to measure physical and biogeochemical structure of oceanic regions rarely observed. In this study, we use a new stage of development in biologging technology to draw a picture of dissolved oxygen concentration in the SO. We present the first results obtained from a dissolved oxygen sensor added to Argos CTD-SRDL tags and deployed on 5 female elephant seals at Kerguelen. From October 2010 and October 2011, 742 oxygen profiles associated with temperature and salinity measurements were recorded. Whether a part of the data must be considered cautiously, especially because of offsets and temporal drifts of the sensors, the range of values recorded was consistent with a concomitant survey conducted from a research vessel (Keops-2 project). Once again, elephant seals reinforced the relationship between marine ecology and oceanography, delivering essential information about the water masses properties and the biological status of the Southern Ocean. But more than the presentation of a new stage of development in animal-borne instrumentation, this pilot study opens a new field of investigation in marine ecology and could be enlarged in a near future to other key marine predators, especially large fish species like swordfish, tuna or sharks, for which dissolved oxygen is expected to play a crucial role in distribution and behaviour.

  13. Determining Dissolved Oxygen Levels

    Science.gov (United States)

    Boucher, Randy

    2010-01-01

    This project was used in a mathematical modeling and introduction to differential equations course for first-year college students. The students worked in two-person groups and were given three weeks to complete the project. Students were given this project three weeks into the course, after basic first order linear differential equation and…

  14. Extreme learning machines: a new approach for modeling dissolved oxygen (DO) concentration with and without water quality variables as predictors.

    Science.gov (United States)

    Heddam, Salim; Kisi, Ozgur

    2017-07-01

    In this paper, several extreme learning machine (ELM) models, including standard extreme learning machine with sigmoid activation function (S-ELM), extreme learning machine with radial basis activation function (R-ELM), online sequential extreme learning machine (OS-ELM), and optimally pruned extreme learning machine (OP-ELM), are newly applied for predicting dissolved oxygen concentration with and without water quality variables as predictors. Firstly, using data from eight United States Geological Survey (USGS) stations located in different rivers basins, USA, the S-ELM, R-ELM, OS-ELM, and OP-ELM were compared against the measured dissolved oxygen (DO) using four water quality variables, water temperature, specific conductance, turbidity, and pH, as predictors. For each station, we used data measured at an hourly time step for a period of 4 years. The dataset was divided into a training set (70%) and a validation set (30%). We selected several combinations of the water quality variables as inputs for each ELM model and six different scenarios were compared. Secondly, an attempt was made to predict DO concentration without water quality variables. To achieve this goal, we used the year numbers, 2008, 2009, etc., month numbers from (1) to (12), day numbers from (1) to (31) and hour numbers from (00:00) to (24:00) as predictors. Thirdly, the best ELM models were trained using validation dataset and tested with the training dataset. The performances of the four ELM models were evaluated using four statistical indices: the coefficient of correlation (R), the Nash-Sutcliffe efficiency (NSE), the root mean squared error (RMSE), and the mean absolute error (MAE). Results obtained from the eight stations indicated that: (i) the best results were obtained by the S-ELM, R-ELM, OS-ELM, and OP-ELM models having four water quality variables as predictors; (ii) out of eight stations, the OP-ELM performed better than the other three ELM models at seven stations while the R

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

    Science.gov (United States)

    Landmeyer, James E.; Effinger, Thomas N.

    2016-01-01

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

  16. Fuzzy control of dissolved oxygen, pH and temperature of bubble column bioreactor for Candida utilis biomass production

    Directory of Open Access Journals (Sweden)

    Hubert Arteaga Miñano

    2012-06-01

    Full Text Available An automatic control system by dissolved oxygen (DO fuzzy logic, pH and temperature in a bubble column bioreactor (BCB for Candida utilis CECT 10704 biomass production was implemented. Their performance was compared with the classical proportional control. A data acquisition card for the control was designed, built and programmed, using the 4.14 Eagle software for the design and the 3.0 Microcode Studio Plus for programming. A program in 6.0 Visual Basic, which linked up with 7.0 MatLab for fuzzy control was developed; using Mandani inference, membership functions of input and output trapezoidal and triangular; 4 rules for the DO, 3 for pH and 3 for temperature, with connector and type and for defuzzifying the centroid method. Evaluation of biomass production was performed by determining dry weight and growth kinetics with the Gompertz model.The fuzzy control performance of DO, pH and temperature showed superiority in proportional control, characterized by a very close control to set point and a low standard deviation. DO Fuzzy control at 6 ppm, pH of 6 and 30°C, allowed to have the greatest dry weight of 7.65±0.02 g/L and the highest maximum growth of 1.51±0.2, the lowest adaptation phase of 0.27±0.01 h and the greatest specific speed of Candida utilis growth rate of 0.7±0.01 h-1.

  17. Modelling of dissolved oxygen in the Danube River using artificial neural networks and Monte Carlo Simulation uncertainty analysis

    Science.gov (United States)

    Antanasijević, Davor; Pocajt, Viktor; Perić-Grujić, Aleksandra; Ristić, Mirjana

    2014-11-01

    This paper describes the training, validation, testing and uncertainty analysis of general regression neural network (GRNN) models for the forecasting of dissolved oxygen (DO) in the Danube River. The main objectives of this work were to determine the optimum data normalization and input selection techniques, the determination of the relative importance of uncertainty in different input variables, as well as the uncertainty analysis of model results using the Monte Carlo Simulation (MCS) technique. Min-max, median, z-score, sigmoid and tanh were validated as normalization techniques, whilst the variance inflation factor, correlation analysis and genetic algorithm were tested as input selection techniques. As inputs, the GRNN models used 19 water quality variables, measured in the river water each month at 17 different sites over a period of 9 years. The best results were obtained using min-max normalized data and the input selection based on the correlation between DO and dependent variables, which provided the most accurate GRNN model, and in combination the smallest number of inputs: Temperature, pH, HCO3-, SO42-, NO3-N, Hardness, Na, Cl-, Conductivity and Alkalinity. The results show that the correlation coefficient between measured and predicted DO values is 0.85. The inputs with the greatest effect on the GRNN model (arranged in descending order) were T, pH, HCO3-, SO42- and NO3-N. Of all inputs, variability of temperature had the greatest influence on the variability of DO content in river body, with the DO decreasing at a rate similar to the theoretical DO decreasing rate relating to temperature. The uncertainty analysis of the model results demonstrate that the GRNN can effectively forecast the DO content, since the distribution of model results are very similar to the corresponding distribution of real data.

  18. Enhancement of 5-keto-d-gluconate production by a recombinant Gluconobacter oxydans using a dissolved oxygen control strategy.

    Science.gov (United States)

    Yuan, Jianfeng; Wu, Mianbin; Lin, Jianping; Yang, Lirong

    2016-07-01

    The rapid and incomplete oxidation of sugars, alcohols, and polyols by the gram-negative bacterium Gluconobacter oxydans facilitates a wide variety of biological applications. For the conversion of glucose to 5-keto-d-gluconate (5-KGA), a promising precursor of the industrial substance L-(+)-tartaric acid, G. oxydans DSM2343 was genetically engineered to strain ZJU2, in which the GOX1231 and GOX1081 genes were knocked out in a markerless fashion. Then, a secondary alcohol dehydrogenase (GCD) from Xanthomonas campestris DSM3586 was heterologously expressed in G. oxydans ZJU2. The 5-KGA production and cell yield were increased by 10% and 24.5%, respectively. The specific activity of GCD towards gluconate was 1.75±0.02 U/mg protein, which was 7-fold higher than that of the sldAB in G. oxydans. Based on the analysis of kinetic parameters including specific cell growth rate (μ), specific glucose consumption rate (qs) and specific 5-KGA production rate (qp), a dissolved oxygen (DO) control strategy was proposed. Finally, batch fermentation was carried out in a 15-L bioreactor using an initial agitation speed of 600 rpm to obtain a high μ for cell growth. Subsequently, DO was continuously maintained above 20% to achieve a high qp to ensure a high accumulation of 5-KGA. Under these conditions, the maximum concentration of 5-KGA reached 117.75 g/L with a productivity of 2.10 g/(L·h).

  19. Hydrodynamic features of the South Aegean Sea as derived from Argo T/ S and dissolved oxygen profiles in the area

    Science.gov (United States)

    Kassis, Dimitris; Krasakopoulou, Evangelia; Korres, Gerasimos; Petihakis, George; Triantafyllou, George S.

    2016-11-01

    In this work, the hydrodynamic picture of the South Aegean Sea is examined through an analysis of recent measurements in its sub-basins, the Myrtoan and Cretan Sea. Both sub-basins play an important role in the water circulation, exchange, and formation processes that affect the dynamics of the whole Eastern Mediterranean. For the first time, Bio-Argo floats were deployed in the area under the Greek Argo Research Infrastructure coordination. The acquired profiles cover an almost 2-year period (November 2013-July 2015) and are compared with previous Argo profiles and the re-processed time-series data recorded from the E1-M3A POSEIDON observatory operating in the area since 2007. The spatio-temporal distribution of the physical and chemical properties in each sub-basin is examined. Dense water formation events are revealed in the northern part (Myrtoan), while the wider area can be characterized as pre-conditioned. In the Cretan basin, a strong inter-annual variability of the salinity field at intermediate and deep layers is observed that is associated with water exchange from its open boundaries. Furthermore, comparison of the dissolved oxygen (DO) distribution with physical water properties within both the mixed layer, and at greater depths, indicated that relatively high but still under-saturated DO values are more likely to be associated with convection events. Finally, an updated picture of the physical properties and the DO distribution is presented based on the last 5 years of measurements and the recent introduction of Bio-Argo floats with DO sensors in the area.

  20. Dissolved Oxygen in Guadalupe Slough and Pond A3W, South San Francisco Bay, California, August and September 2007

    Science.gov (United States)

    Shellenbarger, Gregory; Schoellhamer, David H.; Morgan, Tara L.; Takekawa, John Y.; Athearn, Nicole D.; Henderson, Kathleen D.

    2008-01-01

    Initial restoration of former salt evaporation ponds under the South Bay Salt Pond Restoration Project in San Francisco Bay included the changing of water-flow patterns and the monitoring of water quality of discharge waters from the ponds. Low dissolved oxygen (DO) concentrations became evident in discharge waters when the ponds first were opened in 2004. This was a concern, because of the potential for low-DO pond discharge to decrease the DO concentrations in the sloughs that receive water from the ponds. However, as of summer 2007, only limited point-measurements of DO concentrations had been made in the receiving sloughs adjacent to the discharge ponds. In this report, we describe two short studies aimed at understanding the natural variability of slough DO and the effect of pond discharge on the DO concentrations in the sloughs. Pond A3W (a discharge pond) and the adjacent Guadalupe Slough were instrumented in August and September 2007 to measure DO, temperature, conductivity, and pH. In addition, Mowry and Newark Sloughs were instrumented during the August study to document DO variability in nearby sloughs that were unaffected by pond discharge. The results showed that natural tidal variability in the slough appeared to dominate and control the slough DO concentrations. Water-quality parameters between Guadalupe Slough and Mowry and Newark Sloughs could not be directly compared because deployment locations were different distances from the bay. Pond-discharge water was identified in Guadalupe Slough using the deployed instruments, but, counter to the previous assumption, the pond discharge, at times, increased DO concentrations in the slough. The effects of altering the volume of pond discharge were overwhelmed by natural spring-neap tidal variability in the slough. This work represents a preliminary investigation by the U.S. Geological Survey of the effects of pond discharge on adjacent sloughs, and the results will be used in designing a comprehensive DO

  1. Dissolved Oxygen (DO) and Nutrients Analysis in the Río Piedras River, San Juan, Puerto Rico

    Science.gov (United States)

    Santiago, I.; Infante, G.

    2016-02-01

    The Río Piedras is the only River in the metropolitan area of Puerto Rico. This River was the first water supplier and is part of the ancient aqueduct, the first treatment plant of the San Juan urban area. Because of its cultural and historic importance the ancient aqueduct was cataloged as a National Treasure by the National Trust of History Preservation in 2014. Actually, is protected by Para La Naturaleza (before named in Spanish as the "Fideicomiso de Conservación de Puerto Rico"). The research objectives were to evaluate and measure the dissolved oxygen (DO), total phosphorus (TP) and the heavy metals (HM) concentrations of the River. Also, to examine if the DO, TP and HM (Cu, Fe, Pb, Mn, Al, and Zn) concentrations were in compliance with the Environmental Protection Agency (EPA) standards. Using DO bottles, water samples were collected on three points during six dates. DO concentrations were measured with the YSI Pro GBOD. TP concentrations were analyzed using the UV-Vis spectrophotometer "HACH" (DR 5000). Utilizing the ICP (Inductively Coupled Plasma) spectrophotometer emission technique and the EPA protocols HM concentrations were measured. Preliminary results show that the DO measurements were from 5.00 mg/L to 7.00 mg/L (p-value=0.282). HM concentrations findings were 0.456 (correlation coefficient=0.9997), 1.205 (correlation coefficient=0.9972) and 3.287 (correlation coefficient=0.9950) for Zn, Cu and Cr, respectively. We expected highest HM concentrations in our finals results due to the drought weather during each samples collection. Data analysis for DO, TP and HM concentrations will be presented. Finally, the results obtained and the project details will be explained during the poster presentation.

  2. Stream macroinvertebrate occurrence along gradients in organic pollution and eutrophication

    DEFF Research Database (Denmark)

    Friberg, Nikolai; Skriver, Jens; Larsen, Søren Erik

    2010-01-01

    We analysed a large number of concurrent samples of macroinvertebrate communities and chemical indicators of eutrophication and organic pollution [total-P, total-N, NH4-N, biological oxygen demand (BOD5)] from 594 Danish stream sites. Samples were taken over an 11-year time span as part of the Da......We analysed a large number of concurrent samples of macroinvertebrate communities and chemical indicators of eutrophication and organic pollution [total-P, total-N, NH4-N, biological oxygen demand (BOD5)] from 594 Danish stream sites. Samples were taken over an 11-year time span as part...... to be slightly less sensitive than Leuctra. Other plecopterans such as Isoperla showed a similar type of response curve to Leuctra (negative exponential) but occurred at sites with relatively high concentrations of BOD5 up to 3-4 mg L-1. In contrast, the response curve of the isopod Asellus aquaticus followed...

  3. The investigation of effect of organic carbon sources addition in anaerobic-aerobic (low dissolved oxygen) sequencing batch reactor for nutrients removal from wastewaters.

    Science.gov (United States)

    Zheng, Xiong; Tong, Juan; Li, Hongjing; Chen, Yinguang

    2009-05-01

    The effect of addition of organic carbon sources (acetic acid and waste activated sludge alkaline fermentation liquid) on anaerobic-aerobic (low dissolved oxygen, 0.15-0.45 mg/L) biological municipal wastewater treatment was investigated. The results showed that carbon source addition affected not only the transformations of polyhydroxyalkanoates (PHA), glycogen, nitrogen and phosphorus, but the net removal of nitrogen and phosphorus. The removal efficiencies of TN and TP were, respectively, 61% and 61% without organic carbon source addition, 81% and 95% with acetic acid addition, and 83% and 97% with waste activated sludge alkaline fermentation liquid addition. It seems that the alkaline fermentation liquid of waste biosolids generated in biological wastewater treatment plant can be used to replace acetic acid as an additional carbon source to improve the anaerobic-aerobic (low dissolved oxygen) municipal wastewater nutrients removal although its use was observed to cause a slight increase of effluent BOD and COD concentrations.

  4. Determining Dissolved Oxygen with Carbon Tetrachloride Visual Colorimetry%四氯化碳显色法测定溶解氧

    Institute of Scientific and Technical Information of China (English)

    韩丽媛

    2011-01-01

    This paper introduces a new method for determining the content of dissolved oxygen. The method is suitable for emergent monitoring thanks to its speed, accuracy, manifest result of analysis.%本文介绍了一种测定溶解氧的新方法。此方法快速、准确、分析结果直观、适合应急监测。

  5. Optical sensor based on fluorescent quenching and pulsed blue LED excitation for long-term monitoring of dissolved oxygen in NASA space bioreactors.

    Science.gov (United States)

    Gao, Frank G; Fay, James M; Mathew, Grace; Jeevarajan, Antony S; Anderson, Melody M

    2005-01-01

    There is a need to monitor the concentration of dissolved oxygen (DO) present in the culture medium for NASA's space cell biology experiments, as well as in earth-based cell cultures. Continuous measurement of DO concentration in the cell culture medium in perfused bioreactors requires that the oxygen sensor provide adequate sensitivity and low toxicity to the cells, as well as maintain calibration over several weeks. Although there are a number of sensors for dissolved oxygen on the market and under development elsewhere, very few meet these stringent conditions. An in-house optical oxygen sensor (HOXY) based on dynamic fluorescent quenching of Tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) chloride and a pulsed blue LED light source was developed in our laboratory to address these requirements. The sensing element consisted of the fluorescent dye embedded in a silicone matrix and coated onto a glass capillary. Photobleaching was minimized by a pulsed LED light source. The total noise in the sensor output is 2% and the sensor dynamic range is 0 to 200 mm Hg. The resolution of the sensor is 0.1 mm Hg at 50 mm Hg, and 0.25 mm Hg at 130 mm Hg, while the accuracy is 5%. The LED-based oxygen sensor exhibited stable performance and low drift, making it compatible for space-flight bioreactor systems.

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

    Science.gov (United States)

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

    2013-09-01

    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.

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

    Institute of Scientific and Technical Information of China (English)

    Yiming Su; Yalei Zhang; Xuefei Zhou; Ming Jiang

    2013-01-01

    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.

  8. Study of double bond equivalents and the numbers of carbon and oxygen atom distribution of dissolved organic matter with negative-mode FT-ICR MS.

    Science.gov (United States)

    Bae, EunJung; Yeo, In Joon; Jeong, Byungkwan; Shin, Yongsik; Shin, Kyung-Hoon; Kim, Sunghwan

    2011-06-01

    A strong linear relationship was observed between the average double bond equivalence (DBE) and the ratio of carbon to oxygen atoms in oxygenated compounds of dissolved organic matter (DOM). Data were acquired by a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS), equipped with a negative-mode electrospray ionization source. The slope and y-intercepts extracted from the linear relationship can be used to compare DOM samples originating from different locations. Significant differences in these parameters were observed between inland riverine and offshore coastal DOM samples. Offshore coastal DOM molecules underwent a change of one DBE for each removal or addition of two oxygen atoms. This suggested the existence of multiple carboxyl groups, each of which contains a double bond and two oxygen atoms. Inland riverine samples exhibited a change of ~1.5 DBE following the addition or removal of two oxygen atoms. This extra change in DBE was attributed to cyclic structures or unsaturated chemical bonds. The DBE value with maximum relative abundance and the minimum DBE value for each class of oxygenated compounds showed that approximately two oxygen atoms contributed to a unity change in DBE. The qualitative analyses given here are in a good agreement with results obtained from analyses using orthogonal analytical techniques. This study demonstrates that DBE and the carbon number distribution, observed by high resolution mass spectrometry, can be valuable in elucidating and comparing structural features of oxygenated molecules of DOM.

  9. Aspects of the uptake of dissolved oxygen in Cabiúnas and Imboassica Lagoons (Macaé, RJ

    Directory of Open Access Journals (Sweden)

    Paulo R. Brum

    1999-01-01

    Full Text Available In this work, we describe qualitative and quantitative aspects of the cycling of detritus of aquatic macrophytes and carbohydrates in two coastal lagoons of the northeastern part of the State of Rio de Janeiro. Samples of water of the Imboassica and Cabiúnas lagoons were enriched with sucrose. Samples of water of the Cabiúnas lagoon were also utilized to arrange mineralization chambers with fragments of three species of aquatic macrophytes found in these lagoons (Typha domingensis, Potamogeton stenostachys and Nymphaea ampla. Following that, the bottles were aerated and incubated (in the laboratory for a period of 8 days. The concentrations of dissolved oxygen, the pH, the electrical conductivity and the temperature were daily measured. The anaerobic processes were inhibited by periodical aeration of the bottles. The results suggested that the mineralization process in Imboassica lagoon was more efficient; in Cabiúnas lagoon the process of immobilization of the organic matter was dominant. In the short term, maximum oxygen uptake occurred in the mineralization of N. ampla, followed by the mineralization of P. stenostachys and of T. domingensis. However, it was estimated that in long term the mineralization of P. stenostachys showed a greater oxygen uptake.Nesta pesquisa, descrevemos aspectos qualitativos e quantitativos da ciclagem de detritos de macrófitas aquáticas e carboidratos em duas lagoas costeiras do nordeste do Estado do Rio de Janeiro. Amostras de água das lagoas Imboassica e Cabiúnas foram enriquecidas com sacarose. Amostras de água da lagoa Cabiúnas foram também utilizadas para a montagem de câmaras de mineralização com fragmentos de três espécies de macrófitas aquáticas encontradas nestas lagoas (Typha domingensis, Potamogeton stenostachys e Nymphaea ampla. Em seguida, as garrafas foram aeradas e incubadas (no laboratório por um período de 8 dias. As concentrações de oxigênio dissolvido, o pH, a condutividade

  10. The distribution of nutrients, dissolved oxygen and chlorophyll a in the upper Gulf of Nicoya, Costa Rica, a tropical estuary

    Directory of Open Access Journals (Sweden)

    Jaime Palter

    2007-06-01

    Full Text Available in the Gulf of Nicoya on the Pacific Coast of Costa Rica, nutrient rich equatorial subsurface water (ESW is upwelled in much of the lower gulf. These offshore waters are often regarded as the major source of nutrients to the gulf. However, for most of the year, the ESW has little influence on the nutrient content of the upper gulf, which has a distinct character from the lower gulf. The upper gulf, extending 40 km north of the restriction between Puntarenas Peninsula and San Lucas island, is bordered primarily by mangrove swamps, is less than 20 m deep, and is less saline than the lower gulf. We surveyed the upper gulf for dissolved inorganic nitrogen, phosphate, silicate, dissolved oxygen, and chlorophyll in November 2000, January and July 2001. All nutrients are more concentrated in the upper gulf during the rainy and transitional seasons than the dry season, significantly so for phosphate and silicate. Throughout the year, nutrients tend to be much more concentrated in the less saline water of the upper gulf. This trend indicates that discharge from the Tempisque River predominantly controls spatial and temporal nutrient variability in the upper gulf. However, nutrient rich ESW, upwelled offshore and mixed to form a mid-temperature intermediate water, may enter the inner gulf to provide an important secondary source of nutrients during the dry season. Rev. Biol. Trop. 55 (2: 427-436. Epub 2007 June, 29.Las aguas subsuperficiales ecuatoriales (ESW que entran por la parte externa del Golfo de Nicoya de Costa Rica, se consideran una fuente importante de nutrientes para el estuario. Sin embargo, durante la mayoría del año las ESW tiene una influencia pequeña en la parte interna del golfo, que es oceanográfica y biológicamente diferente de la parte externa. La parte interna está ubicada desde la península de Puntarenas hasta la boca del Río Tempisque, 40 km al norte; es un área que se caracteriza por un importante aporte de agua dulce

  11. Dissolved oxygen as a factor influencing nitrogen removal rates in a one-stage system with partial nitritation and Anammox process.

    Science.gov (United States)

    Cema, G; Płaza, E; Trela, J; Surmacz-Górska, J

    2011-01-01

    A biofilm system with Kaldnes biofilm carrier was used in these studies to cultivate bacteria responsible for both partial nitritation and Anammox processes. Due to co-existence of oxygen and oxygen-free zones within the biofilm depth, both processes can occur in a single reactor. Oxygen that inhibits the Anammox process is consumed in the outer layer of the biofilm and in this way Anammox bacteria are protected from oxygen. The impact of oxygen concentration on nitrogen removal rates was investigated in the pilot plant (2.1 m3), supplied with reject water from the Himmerfjärden Waste Water Treatment Plant. The results of batch tests showed that the highest nitrogen removal rates were obtained for a dissolved oxygen (DO) concentration around 3 g O2 m(-3) At a DO concentration of 4 g O2 m(-3), an increase of nitrite and nitrate nitrogen concentrations in the batch reactor were observed. The average nitrogen removal rate in the pilot plant during a whole operating period oscillated around 1.3 g N m(-2)d(-1) (0.3 +/- 0.1 kg N m(-3)d(-1)) at the average dissolved oxygen concentration of 2.3 g O2 m(-3). The maximum value of a nitrogen removal rate amounted to 1.9 g N m(-2)d(-1) (0.47 kg N m(-3)d(-1)) and was observed for a DO concentration equal to 2.5 g O2 m(-3). It was observed that increase of biofilm thickness during the operational period, had no influence on nitrogen removal rates in the pilot plant.

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

    Science.gov (United States)

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

    2013-12-01

    The hyporheic zone (HZ) is a potentially important source of the potent greenhouse gas, nitrous oxide (N2O); stream processes may account for up to 10% of global anthropogenic N2O emissions. However, mechanistic understanding and predictive quantification of this gas flux is hampered by complex temporally and spatially variable interactions between flow dynamics and biogeochemical processes. Reactive inorganic nitrogen (Nr) is typically present at low concentrations in natural stream waters, but many rural and urban streams suffer from an excess of Nr, typically in the form of ammonium (NH4+) and nitrate (NO3-). These reactive species are either assimilated by living biomass or transformed by microbial processes. The two primary microbial transformations of Nr are nitrification (NH4+ to NO3-) and denitrification (NO3- to N2). Denitrification, which occurs almost exclusively in the anoxic zone of the HZ, permanently removes between 30-70% of all Nr entering streams, other mechanisms may retain nitrogen. The mass transport of reactive species (i.e. O2, NO3- and N2O) by hyporheic flow strongly influences reaction rates, residence times, and subsequent N2O flux. By extension, stream flow and channel morphology presumably control, and may be effective predictors of, N2O generation rates. By recreating the stream processes in the University of Idaho flume, we are able to control the bed morphology, fluxes and residence times through the HZ and concentrations of Nr from exogenous (stream water) and endogenous (organic material in the streambed) sources. For the present experiment, the flume was divided into three streams, each with different morphologies (3, 6 and 9cm dunes) and all using the same source water. Stream water for this first experimental phase had no significant loading of Nr. As such, all reaction products were the result of endogenous sources of Nr. To measure dissolved oxygen (DO) concentrations we deployed 120 channels of a novel, fiber-optic optode

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

    Science.gov (United States)

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

    2011-12-15

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

  14. Effect of Dissolved Oxygen on Swimming Ability and Physiological Response to Swimming Fatigue of Whiteleg Shrimp (Litopenaeus vannamei)

    Institute of Scientific and Technical Information of China (English)

    DUAN Yan; ZHANG Xiumei; LIU Xuxu; Dhanrajsingh N. Thakur

    2014-01-01

    The swimming endurance of whiteleg shrimp (Litopenaeus vannamei, 87.66 mm ± 0.25 mm, 7.73 g ± 0.06 g) was exam-ined at various concentrations of dissolved oxygen (DO, 1.9, 3.8, 6.8 and 13.6 mg L-1) in a swimming channel against one of the five flow velocities (v1, v2, v3, v4 and v5). Metabolite contents in the plasma, hepatopancreas and pleopods muscle of the shrimp were quantified before and after swimming fatigue. The results revealed that the swimming speed and DO concentration were significant factors that affected the swimming endurance of L. vannamei. The relationship between swimming endurance and swimming speed at various DO concentrations can be described by the power model (ν·tb=a). The relationship between DO concentration (mg L-1) and the swimming ability index (SAI), defined as SAI= 90000∫ vdt (cm) , can be described as SAI=27.947 DO0.137 (R2=0.9312). The level of DO concentration directly affected the physiology of shrimp, and exposure to low concentrations of DO led to the increases in lactate and energetic substrate content in the shrimp. In responding to the low DO concentration at 1.9 mg L-1 and the swimming stress, L. vannamei exhibited a mix of aerobic and anaerobic metabolism to satisfy the energetic demand, mainly characterized by the utilization of total protein and glycogen and the production of lactate and glucose. Fatigue from swimming led to severe loss of plasma triglyceride at v1, v2, and v3 with 1.9 mg L-1 DO, and at v1 with 3.8, 6.8 and 13.6 mg L-1 DO, whereas the plasma glucose con-tent increased significantly at v3, v4 and v5 with 3.8 and 6.8 mg L-1 DO, and at v5 with 13.6 mg L-1 DO. The plasma total protein and hepatopancreas glycogen were highly depleted in shrimp by swimming fatigue at various DO concentrations, whereas the plasma lactate accumulated at high levels after swimming fatigue at different velocities. These results were of particular value to under-standing the locomotory ability of whiteleg shrimp and its

  15. Assessment of Dissolved Oxygen Mitigation at Hydropower Dams Using an Integrated Hydrodynamic/Water Quality/Fish Growth Model

    Energy Technology Data Exchange (ETDEWEB)

    Bevelhimer, Mark S [ORNL; Coutant, Charles C [ORNL

    2006-07-01

    Dissolved oxygen (DO) in rivers is a common environmental problem associated with hydropower projects. Approximately 40% of all FERC-licensed projects have requirements to monitor and/or mitigate downstream DO conditions. Most forms of mitigation for increasing DO in dam tailwaters are fairly expensive. One area of research of the Department of Energy's Hydropower Program is the development of advanced turbines that improve downstream water quality and have other environmental benefits. There is great interest in being able to predict the benefits of these modifications prior to committing to the cost of new equipment. In the case of turbine replacement or modification, there is a need for methods that allow us to accurately extrapolate the benefits derived from one or two turbines with better design to the replacement or modification of all turbines at a site. The main objective of our study was to demonstrate a modeling approach that integrates the effects of flow and water quality dynamics with fish bioenergetics to predict DO mitigation effectiveness over long river segments downstream of hydropower dams. We were particularly interested in demonstrating the incremental value of including a fish growth model as a measure of biological response. The models applied are a suite of tools (RMS4 modeling system) originally developed by the Tennessee Valley Authority for simulating hydrodynamics (ADYN model), water quality (RQUAL model), and fish growth (FISH model) as influenced by DO, temperature, and available food base. We parameterized a model for a 26-mile reach of the Caney Fork River (Tennessee) below Center Hill Dam to assess how improvements in DO at the dam discharge would affect water quality and fish growth throughout the river. We simulated different types of mitigation (i.e., at the turbine and in the reservoir forebay) and different levels of improvement. The model application successfully demonstrates how a modeling approach like this one can be

  16. Role of Dissolved and Molecular Oxygen on Cu and PtCu Alloy Particle Structure during Laser Ablation Synthesis in Liquids.

    Science.gov (United States)

    Marzun, Galina; Bönnemann, Helmut; Lehmann, Christian; Spliethoff, Bernd; Weidenthaler, Claudia; Barcikowski, Stephan

    2017-05-05

    The role of molecular oxygen dissolved in the solvent is often discussed as being an influential factor on particle oxidation during pulsed laser ablation in liquids. However, the formation of the particles during laser synthesis takes place under extreme conditions that enable the decomposition of the liquid medium. Reactive species of the solvent may then affect particle formation due to a chemical reaction in the reactive plasma. Experimental results show a difference between the role of dissolved molecular oxygen and the contribution from the oxygen in water molecules. Using a metallic Cu target in air-saturated water, laser ablation led to 20.5 wt % Cu, 11.5 wt % Cu2 O, and 68 wt % CuO nanoparticles, according to X-ray diffraction results. In contrast to particles obtained in air-saturated water, no CuO was observed in the colloid synthesized in a Schlenk ablation chamber in completely oxygen-free water. Under these conditions, less-oxidized nanoparticles (25 wt % Cu and 75 wt % Cu2 O) were synthesized. The results show that nanoparticle oxidation during laser synthesis is mainly caused by reactive oxygen species from the decomposition of water molecules. However, the addition of molecular oxygen promotes particle oxidation. Storage of the Cu colloid in the presence of dissolved oxygen leads, due to aging, to nanostructures with a higher oxidation state than the freshly prepared colloid. The XRD pattern of the sample prepared in air-saturated acetone showed no crystalline phases, which is possibly due to small crystallites or low particle concentration. Concentration of the particles by centrifugation showed that in the large fraction (>20 nm), even less oxidized nanoparticles (46 wt % Cu and 54 wt % Cu2 O) were present, although the solubility of molecular oxygen is higher in acetone than in water. The nanoparticles in acetone were stable due to a Cu-catalyzed graphite layer formed on their surfaces. The influence of the solvent

  17. Spatial-temporal variability in water quality and macro-invertebrate assemblages in the Upper Mara River basin, Kenya

    Science.gov (United States)

    Kilonzo, Fidelis; Masese, Frank O.; Van Griensven, Ann; Bauwens, Willy; Obando, Joy; Lens, Piet N. L.

    Tropical rivers display profound temporal and spatial heterogeneity in terms of environmental conditions. This aspect needs to be considered when designing a monitoring program for water quality in rivers. Therefore, the physico-chemical composition and the nutrient loading of the Upper Mara River and its two main tributaries, the Amala and Nyangores were monitored. Initial daily, and later a weekly monitoring schedule for 4 months spanning through the wet and dry seasons was adopted. Benthic macro-invertebrates were also collected during the initial sampling to be used as indicators of water quality. The aim of the current study was to investigate the physico-chemical status and biological integrity of the Upper Mara River basin. This was achieved by examining trends in nutrient concentrations and analyzing the structure, diversity and abundance of benthic macro-invertebrates in relation to varying land use patterns. Sampling sites were selected based on catchment land use and the level of human disturbance, and using historical records of previous water quality studies. River water pH, dissolved oxygen, electrical conductivity (EC), temperature, and turbidity were determined in situ. All investigated parameters except iron and manganese had concentration values within allowable limits according to Kenyan and international standards for drinking water. The Amala tributary is more mineralized and also shows higher levels of pH and EC than water from the Nyangores tributary. The latter, however, has a higher variability in both the total phosphorus (TP) and total nitrogen (TN) concentrations. The variability in TP and TN concentrations increases downstream for both tributaries and is more pronounced for TN than for TP. Macro-invertebrate assemblages responded to the changes in land use and water quality in terms of community composition and diversity. The study recommends detailed continuous monitoring of the water quality at shorter time intervals and to identify

  18. Multimillennium changes in dissolved oxygen under global warming: results from an AOGCM and offline ocean biogeochemical model

    Science.gov (United States)

    Yamamoto, A.; Abe-Ouchi, A.; Shigemitsu, M.; Oka, A.; Takahashi, K.; Ohgaito, R.; Yamanaka, Y.

    2016-12-01

    Long-term oceanic oxygen change due to global warming is still unclear; most future projections (such as CMIP5) are only performed until 2100. Indeed, few previous studies using conceptual models project oxygen change in the next thousands of years, showing persistent global oxygen reduction by about 30% in the next 2000 years, even after atmospheric carbon dioxide stops rising. Yet, these models cannot sufficiently represent the ocean circulation change: the key driver of oxygen change. Moreover, considering serious effect oxygen reduction has on marine life and biogeochemical cycling, long-term oxygen change should be projected for higher validity. Therefore, we used a coupled atmosphere-ocean general circulation model (AOGCM) and an offline ocean biogeochemical model, investigating realistic long-term changes in oceanic oxygen concentration and ocean circulation. We integrated these models for 2000 years under atmospheric CO2 doubling and quadrupling. After global oxygen reduction in the first 500 years, oxygen concentration in deep ocean globally recovers and overshoots, despite surface oxygen decrease and weaker Atlantic Meridional Overturning Circulation. Deep ocean convection in the Weddell Sea recovers and overshoots, after initial cessation. Thus, enhanced deep convection and associated Antarctic Bottom Water supply oxygen-rich surface waters to deep ocean, resulting global deep ocean oxygenation. We conclude that the change in ocean circulation in the Southern Ocean potentially drives millennial-scale oxygenation in the deep ocean; contrary to past reported long-term oxygen reduction and general expectation. In presentation, we will discuss the mechanism of response of deep ocean convection in the Weddell Sea and show the volume changes of hypoxic waters.

  19. Response of export production and dissolved oxygen concentrations in oxygen minimum zones to pCO2 and temperature stabilization scenarios in the biogeochemical model HAMOCC 2.0

    Science.gov (United States)

    Beaty, Teresa; Heinze, Christoph; Hughlett, Taylor; Winguth, Arne M. E.

    2017-02-01

    Dissolved oxygen (DO) concentration in the ocean is an important component of marine biogeochemical cycles and will be greatly altered as climate change persists. In this study a global oceanic carbon cycle model (HAMOCC 2.0) is used to address how mechanisms of oxygen minimum zone (OMZ) expansion respond to changes in CO2 radiative forcing. Atmospheric pCO2 is increased at a rate of 1 % annually and the model is stabilized at 2 ×, 4 ×, 6 ×, and 8 × preindustrial pCO2 levels. With an increase in CO2 radiative forcing, the OMZ in the Pacific Ocean is controlled largely by changes in particulate organic carbon (POC) export, resulting in increased remineralization and thus expanding the OMZs within the tropical Pacific Ocean. A potential decline in primary producers in the future as a result of environmental stress due to ocean warming and acidification could lead to a substantial reduction in POC export production, vertical POC flux, and thus increased DO concentration particularly in the Pacific Ocean at a depth of 600-800 m. In contrast, the vertical expansion of the OMZs within the Atlantic is linked to increases POC flux as well as changes in oxygen solubility with increasing seawater temperature. Changes in total organic carbon and increase sea surface temperature (SST) also lead to the formation of a new OMZ in the western subtropical Pacific Ocean. The development of the new OMZ results in dissolved oxygen concentration of ≤ 50 µmol kg-1 throughout the equatorial Pacific Ocean at 4 times preindustrial pCO2. Total ocean volume with dissolved oxygen concentrations of ≤ 50 µmol kg-1 increases by 2.4, 5.0, and 10.5 % for the 2 ×, 4 ×, and 8 × CO2 simulations, respectively.

  20. A one-dimensional, steady-state, dissolved-oxygen model and waste-load assimilation study for Clear Creek, Monroe County, Indiana

    Science.gov (United States)

    Wilber, William G.; Crawford, Charles G.; Peters, J.G.; Girardi, F.P.

    1979-01-01

    A digital model calibrated to conditions in Clear Creek, Monroe County, IN, was used to develop alternatives for future waste loadings that would be compatible with Indiana stream water-quality standards defined for two critical hydrologic conditions, summer and winter low flows. The Winston Thomas wastewater-treatment facility is the only point-source waste load affecting the modeled reach of Clear Creek. A new waste-water-treatment facility under construction at Dillman Road (river mile 13.78) will replace the Winston Thomas wastewater-treatment facility (river mile 16.96) in 1980. Natural streamflow during the summer and annual 7-day, 10-year low flow is zero, so no benefit from dilution is provided. The model indicates that ammonia-nitrogen toxicity is the most significant factor affecting the stream water quality during summer and winter low flows. The ammonia-nitrogen concentration of the wastewater effluent exceeds the maximum total ammonia-nitrogen concentration of 2.5 milligrams per liter for summer months (June through August) and 4.0 milligrams per liter for winter months (November through March) required for Indiana streams. Nitrification, benthic-oxygen demand, and algal respiration were the most significant factors affecting the dissolved-oxygen concentration in Clear Creek during the model calibration. Nitrification should not significantly affect the dissolved-oxygen concentration in Clear Creek during summer low flows when the ammonia-nitrogen toxicity standards are met. (USGS)

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

    Science.gov (United States)

    Ebbert, James C.

    2003-01-01

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

  2. Water temperature, specific conductance, pH, and dissolved-oxygen concentrations in the lower White River and the Puyallup River estuary, Washington, August-October 2002

    Science.gov (United States)

    Ebbert, James C.

    2003-01-01

    The U.S. Geological Survey, Washington State Department of Ecology, and Puyallup Tribe of Indians monitored water temperature, specific conductance, pH, and dissolved-oxygen concentrations in the White River at river miles 4.9 and 1.8 from August until mid-October 2002. Water diverted from the White River upstream from the monitoring sites into Lake Tapps is returned to the river at river mile 3.6 between the two sites. The same characteristics were measured in a cross section of the Puyallup River estuary at river mile 1.5 during high and low tides in September 2002. In late August, maximum daily water temperatures in the White River of 21.1°C (degrees Celsius) at river mile 4.9 and 19.6°C at river mile 1.8 exceeded the water-quality standard of 18°C 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

  3. High temporal and spatial variability of dissolved oxygen and pH in a nearshore California kelp forest

    Directory of Open Access Journals (Sweden)

    C. A. Frieder

    2012-03-01

    Full Text Available Predicting consequences of ocean deoxygenation and ocean acidification for nearshore marine ecosystems requires baseline dissolved oxygen (DO and carbonate chemistry data that are both high-frequency and high-quality. Such data allow accurate assessment of environmental variability and present-day organism exposure regimes. In this study, scales of DO and pH variability were characterized over one year in a nearshore, kelp forest ecosystem in the Southern California Bight. DO and pH were strongly, positively correlated revealing that organisms on this upwelling shelf are not only exposed to low pH but also low DO. The dominant temporal scale of DO and pH variability occurred on semidiurnal, diurnal and event (days–weeks time scales. Daily ranges in DO and pH at 7 m water depth (13 mab could be as large as 220 μmol kg−1 and 0.36 units, respectively. This range is much greater than the expected decreases in pH in the open ocean by the year 2100. Sources of pH and DO variation include photosynthesis within the kelp forest ecosystem, which can elevate DO and pH by up to 60 μmol kg−1 and 0.1 units over one week following the intrusion of high-density, nutrient-rich water. Accordingly, highly productive macrophyte-based ecosystems could serve as deoxygenation and acidification refugia by acting to elevate DO and pH relative to surrounding waters. DO and pH exhibited greater spatial variation over a 10 m increase in water depth (from 7 to 17 m than along a 5-km stretch of shelf in a cross-shore or alongshore direction. Over a three-month time period mean DO and pH at 17-m water depth were 168 μmol kg−1 and 7.87, respectively. These values represent a 35% decrease in mean DO and 37% increase in [H+] relative to surface waters. High-frequency variation was also reduced at depth. The mean daily range in DO and pH was 39% and 37% less, respectively, at 17-m water depth relative to the surface. As a

  4. High temporal and spatial variability of dissolved oxygen and pH in a nearshore California kelp forest

    Directory of Open Access Journals (Sweden)

    C. A. Frieder

    2012-10-01

    Full Text Available Predicting consequences of ocean deoxygenation and ocean acidification for nearshore marine ecosystems requires baseline dissolved oxygen (DO and carbonate chemistry data that are both high-frequency and high-quality. Such data allow accurate assessment of environmental variability and present-day organism exposure regimes. In this study, scales of DO and pH variability were characterized over one year in a nearshore kelp forest ecosystem in the Southern California Bight. DO and pH were strongly, positively correlated, revealing that organisms on this upwelling shelf are not only exposed to low pH but also to low DO. The dominant scale of temporal DO and pH variability occurred on semidiurnal, diurnal and event (days–weeks time scales. Daily ranges in DO and pH at 7 m water depth (13 mab could be as large as 220 μmol kg−1 and 0.36 units, respectively. Sources of pH and DO variation include photosynthesis within the kelp forest ecosystem, which can elevate DO and pH by up to 60 μmol kg−1 and 0.1 units over one week following the intrusion of high-density, nutrient-rich water. Accordingly, highly productive macrophyte-based ecosystems could serve as deoxygenation and acidification refugia by acting to elevate DO and pH relative to surrounding waters. DO and pH exhibited greater spatial variation over a 10 m increase in water depth (from 7 to 17 m than along a 5 km stretch of shelf in a cross-shore or alongshore direction. Over a three-month time period, mean DO and pH at 17 m water depth were 168 μmol kg−1 and 7.87, respectively. These values represent a 35% decrease in mean DO and 37% increase in [H+] relative to near-surface waters. High-frequency variation was also reduced at depth. The mean daily range in DO and pH was 39% and 37% less, respectively, at 17 m water depth relative to 7 m. As a consequence, the exposure history of an organism is largely a function of its depth of occurrence

  5. [Distribution of dissolved inorganic nutrients and dissolved oxygen in the high frequency area of harmful algal blooms in the East China Sea in spring].

    Science.gov (United States)

    Li, Hong-Mei; Shi, Xiao-Yong; Chen, Peng; Zhang, Chuan-Song

    2013-06-01

    According to two cruises in the high frequency area of Harmful Algal Blooms (HABs) in ECS from Apr. 8th to 26th and May 7th to 14th 2010, concentrations and distributions of biogenic elements before and after HABs were analyzed, and their influenced factors were also discussed. The results showed that April was the earlier stage of HAB breaking out, and diatom was the dominant species; while Dinoflagellate became the dominant species when large-scale HAB broke out in May. The concentrations of DIN and PO4(3-) -P decreased significantly from April to May. The Mean value of DIN decreased from 18.04 to 10.80 micromol x L(-1), its decline rate was 40%. As for PO4(3-) -P, its Mean value decreased from 0.47 to 0.27 micromol x L(-1), and its decline rate was 43%. This phenomenon indicated the significant depletion of nutrients by harmful algae in the process. However, the primary species of HABs in ECS was dinoflagellates in May. Since dinoflagellates did not consume SiO3(2-) -Si during the breed, as well as the supplement from Changjiang Diluted Water, the mean value of SiO3(2-) -Si increased slightly from 16. 15 to 16.96 micromol x L(11) in the researched area. The Mean value of DO decreased from 8.76 to 6.09 mg x L(-1) from April to May, because the effect of temperature to DO was more obvious than that of phytoplankton photosynthesis. The temperature was higher in May, and the solubility of oxygen decreased with increasing temperature, therefore, the concentration of DO was lower after the Harmful algal blooms.

  6. Effects of Dissolved Oxygen Concentration and Iron Addition on Immediate-early Gene Expression of Magnetospirillum gryphiswaldense MSR-1

    DEFF Research Database (Denmark)

    Zhuang, Shiwen; Anyaogu, Diana Chinyere; Kasama, Takeshi

    2017-01-01

    iron addition for all the genes studied, except for MgFnr (oxygen sensor gene) and fur (ferric uptake regulator family gene), and which in some cases was oxygen-dependent. In particular, expression of sodB1 (superoxide dismutase gene) and feoB1 (ferrous transport protein B1 gene) were markedly reduced...... in cultures at 0.5% O2 compared to those at higher oxygen tensions. Moreover, expression of katG (catalase-peroxidase gene) and feoB2 (ferrous transport protein B2 gene) was reduced markedly by iron addition, regardless of oxygen conditions. The data provides a greater understanding of molecular response...

  7. Plankton communities and summertime declines in algal abundance associated with low dissolved oxygen in the Tualatin River, Oregon

    Science.gov (United States)

    Carpenter, Kurt D.; Rounds, Stewart A.

    2013-01-01

    Phytoplankton populations in the Tualatin River in northwestern Oregon are an important component of the dissolved oxygen (DO) budget of the river and are critical for maintaining DO levels in summer. During the low-flow summer period, sufficient nutrients and a long residence time typically combine with ample sunshine and warm water to fuel blooms of cryptophyte algae, diatoms, green and blue-green algae in the low-gradient, slow-moving reservoir reach of the lower river. Algae in the Tualatin River generally drift with the water rather than attach to the river bottom as a result of moderate water depths, slightly elevated turbidity caused by suspended colloidal material, and dominance of silty substrates. Growth of algae occurs as if on a “conveyor belt” of streamflow, a dynamic system that is continually refreshed with inflowing water. Transit through the system can take as long as 2 weeks during the summer low-flow period. Photosynthetic production of DO during algal blooms is important in offsetting oxygen consumption at the sediment-water interface caused by the decomposition of organic matter from primarily terrestrial sources, and the absence of photosynthesis can lead to low DO concentrations that can harm aquatic life. The periods with the lowest DO concentrations in recent years (since 2003) typically occur in August following a decline in algal abundance and activity, when DO concentrations often decrease to less than State standards for extended periods (nearly 80 days). Since 2003, algal populations have tended to be smaller and algal blooms have terminated earlier compared to conditions in the 1990s, leading to more frequent declines in DO to levels that do not meet State standards. This study was developed to document the current abundance and species composition of phytoplankton in the Tualatin River, identify the possible causes of the general decline in algae, and evaluate hypotheses to explain why algal blooms diminish in midsummer. Plankton

  8. Distribution of Nile perch Lates niloticus in southern Lake Victoria is determined by depth and dissolved oxygen concentrations

    NARCIS (Netherlands)

    Goudswaard, P.C.; Katunzi, E.F.B.; Wanink, J.H.; Witte, F.

    2011-01-01

    Although Nile perch Lates niloticus is assumed to be sensitive to low oxygen concentrations, it was found in deep water in Lake Victoria, where oxygen depletion is common during the rainy season. Since factors determining Nile perch distribution are not well understood its spatial distribution in

  9. Measuring in-stream productivity: the potential of continuous chlorophyll and dissolved oxygen monitoring for assessing the ecological status of surface waters.

    Science.gov (United States)

    Jarvie, H P; Love, A J; Williams, R J; Neal, C

    2003-01-01

    Continuous (hourly) measurements of dissolved oxygen and chlorophyll (determined by fluorimetry) were made for an inter-linked lowland river and canal system. The dissolved oxygen data were used to estimate daily rates of re-aeration, photosynthesis and respiration, using a process-based analytical technique (the Delta method). In-situ fluorimeter measurements of chlorophyll were ground-truthed on a fortnightly basis using laboratory methanol extraction of chlorophyll and spectrophotometric analysis. Water samples were also analysed for algal species on a fortnightly basis. The river and canal exhibited very similar rates of photosynthesis and respiration during the summer of 2001, despite much higher chlorophyll concentrations and total algal counts, indicating that benthic algae and/or aquatic macrophytes may be making an important contribution to photosynthesis rates in the river. Suspended algal populations in the canal are dominated by planktonic species, whereas the river has a higher proportion of species which are predominantly benthic in habitat. The river exhibited higher rates of respiration, reflecting a higher organic loading from external (e.g. sewage effluent) sources.

  10. The influence of a toxic cyanobacterial bloom and water hydrology on algal populations and macroinvertebrate abundance in the upper littoral zone of Lake Krugersdrift, South Africa.

    Science.gov (United States)

    Oberholster, Paul J; Botha, Anna-Maria; Ashton, Peter J

    2009-01-01

    The biological interactions and the physical and chemical properties of the littoral zone of Lake Krugersdrift were studied for a 4-month period when a dense, toxic cyanobacterial bloom dominated by Microcystis aeruginosa was present in the main lake basin. The presence of a toxic strain of M. aeruginosa was confirmed through the use of ELISA and molecular markers that detect the presence of the mcyB and mcyD genes of the mcy gene cluster that synthesizes microcystin. An increase in Microcystis toxicity at sites dominated by the cyanobacterial scum was accompanied by an increase in total abundance of the macroinvertebrate families Hirudinae, Chironomidae, and Tubificidae. Sites located away from the cyanobacterial scum had a lower abundance but a higher diversity of macroinvertebrates. The water quality under the Microcystis scum was characterized by low pH values, low concentrations of dissolved oxygen, and lower total alkalinity values. The periphytic alga Ulothrix zonata was absent in areas dominated by the cyanobacterial scum, possibly as a result of overshadowing by the scum or direct toxic allelopathic effects on growth and photosynthesis. The diatom Diatoma vulgare dominated the benthic algal flora beneath the cyanobacterial scum.

  11. 水库溶解氧的立面二维数值模拟%Vertical 2D numerical simulation of dissolved oxygen in reservoir

    Institute of Scientific and Technical Information of China (English)

    曾玉红; 槐文信; 陈刚; 刘建

    2013-01-01

    采用宽度平均的立面二维数学模型对水库水质进行数值模拟,通过对水位、水温的计算值与实测值的对比,验证了模型模拟水库水质的有效性.在此基础上,对库区的溶解氧浓度分布进行计算,结果表明,溶解氧的计算值与实测值整体吻合较好,基本能够反映水库中的溶解氧分布特性.对该水库水体中的饱和溶解氧率的计算分析表明,水库水体2007年全年的饱和溶解氧率多在90%以上,水体总体质量较好.在3-5月气温适宜的条件下,由于浮游植物生长旺盛,过饱和情况较为明显.而在夏季(6-9月),由于气温高,水体复氧能力较弱,同时同时期上游来水丰沛,随地表径流带来的面源污染也增加了水体的耗氧量,致使这一时期的溶解氧浓度较低,因此水库溶解氧受上游来流及气温的影响较为显著.%A width-averaged vertical 2D numerical model was adopted to simulate the water quality in a reservoir. Firstly, the water level and water temperature were predicted, and the agreement between the calculated results and the measured data proved that this model is effective in predicting the water quality in reservoir. Then the dissolved oxygen in the reservoir has been predicted, and saturated dissolved oxygen rates were calculated. Further analysis shows that most of the saturated dissolved oxygen rates in 2007 are higher than 90% which means that the water quality of this reservoir is satisfied. Oversaturation phenomenon appeared from March to May since the temperature was comfortable and the growth of aquatic vegetation was exuberant. During flooding season (June to September) , the surface runoff into the reservoir carried a large number of non-point source pollution, which increased the dissolved oxygen consumption; at the same time, the high temperature during this season restained the reoxygenation process of the water body. The conclusion is that the inflow and air temperature are two main

  12. The dissolution rate of unirratiated uranium dioxide under repository conditions: The influence of fuel and water chemistry, dissolved oxygen, and temperature

    Science.gov (United States)

    Casella, Amanda J.

    The dissolution rate of both unirradiated UO2 and spent fuel has been studied by numerous countries as part of the performance assessments of proposed geologic repositories. The effects of variables such as temperature, dissolved oxygen, and water and fuel chemistry on the dissolution rates of the fuel are necessary to provide a quantitative estimate of the potential dose over geologic time frames. The primary objective of this research was to determine the influence these parameters have on the dissolution rate of unirradiated UO2 under Yucca Mountain repository conditions and compare them to the current Yucca Mountain Model. Fuels containing between 0 and 8 wt% Gd2O3-doped UO2 were tested in a single-pass flow-through setup. These tests have verified that in bicarbonate solutions as temperature increased the dissolution rate increased. However, the presence of silicate in the feedwater altered the system and lowered the dissolution rate at higher temperatures. Pure UO 2 samples exhibited a dependence on the dissolved oxygen concentration, which in the current experiments was varied from 3.0 to 8.7 ppm. The significance of this dissolved oxygen dependence increased with rising temperature. At 75ºC the powder samples had a maximum dependence of 0.7, although the fragment samples had a much larger dependence up to 2.2. For the case of the Gd2O3-doped samples, there was minimal oxygen dependence at any temperature. The Gd2O3-dopant stabilized the fuel matrix, which lowered the dissolution rates by over an order of magnitude at the higher dopant levels. This effect in lowering the dissolution rate was more pronounced at higher temperatures, and additional dopant continued to decrease the dissolution rate up to the 4 wt% Gd2O3-doped UO2 tested. The dissolution rates for pure UO2 compared reasonably well with the Yucca Mountain Model for tests performed at 50ºC and 75ºC, but were found to be approximately half the values predicted by the model at 25ºC. After long

  13. Effect of dissolved oxygen on nitrate removal using polycaprolactone as an organic carbon source and biofilm carrier in fixed-film denitrifying reactors.

    Science.gov (United States)

    Luo, Guozhi; Xu, Guimei; Gao, Jinfang; Tan, Hongxin

    2016-05-01

    Nitrate-nitrogen (NO3(-)-N) always accumulates in commercial recirculating aquaculture systems (RASs) with aerobic nitrification units. The ability to reduce NO3(-)-N consistently and confidently could help RASs to become more sustainable. The rich dissolved oxygen (DO) content and sensitive organisms stocked in RASs increase the difficulty of denitrifying technology. A denitrifying process using biologically degradable polymers as an organic carbon source and biofilm carrier was proposed because of its space-efficient nature and strong ability to remove NO3(-)-N from RASs. The effect of dissolved oxygen (DO) levels on heterotrophic denitrification in fixed-film reactors filled with polycaprolactone (PCL) was explored in the current experiment. DO conditions in the influent of the denitrifying reactors were set up as follows: the anoxic treatment group (Group A, average DO concentration of 0.28±0.05mg/L), the low-oxygen treatment DO group (Group B, average DO concentration of 2.50±0.24mg/L) and the aerated treatment group (Group C, average DO concentration of 5.63±0.57mg/L). Feeding with 200mg/L of NO3(-)-N, the NO3(-)-N removal rates were 1.53, 1.60 and 1.42kg/m(3) PCL/day in Groups A, B and C, respectively. No significant difference in NO3(-)-N removal rates was observed among the three treatments. It was concluded that the inhibitory effects of DO concentrations lower than 6mg/L on heterotrophic denitrification in the fixed-film reactors filled with PCL can be mitigated.

  14. A New Optic Technology for Measuring Oxygen Dissolved in Water: Luminescence Dissolved Oxygen (LDO); Nueva tecnologia optica para la medicion de oxigeno disuelto en agua: oxigeno disuelto por luminiscencia (LDO)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2003-07-01

    Continual measurement of oxygen in the active sludge tank is a very important parameter is the biological treatment of waste waters. Traditional electrochemical sensors are based on polarographic or galvanic cells, a technique which produces electrolyte consumption and progressive deterioration of the anode. Both effects inevitable lead to a drift in the measurement signal, which requires periodical calibration. Lange has developed a completely new technique for its new LDO sensor for measuring oxygen concentration in waste waters. This technique is based on the luminescent radiation of a luminescent substance (luminophore) and reduces the determination to the purely physical measurement of time, so that, in theory it is free of drift and there is no need for the use to calibrate the sensor. (Author)

  15. Influence of environmental forcings on the seasonality of dissolved oxygen and nutrients in the Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Sardessai, S.; Ramaiah, N.; PrasannaKumar, S.; DeSouza, S.N.

    in the subsurface layer. In the open ocean the Minimum Oxygen Layer (MOL 10mu Mol L-1) during the southwest monsoon and fall intermonsoon is mostly confined to the north of 11N due to the penetration of high salinity water in the deeper waters of the central Bay...

  16. Interaction between dissolved oxygen concentration and diet composition on growth, digestibility and intestinal health of Nile tilapia (Oreochromis niloticus)

    NARCIS (Netherlands)

    Tran, N.T.K.; Dinh, Ngu T.; Tin, Nguyen Hong; Roem, A.J.; Schrama, J.W.; Verreth, J.A.J.

    2016-01-01

    The present study was undertaken to evaluate the individual and combined effects of oxygen concentration and
    diet composition on the growth, nutrient utilization and intestinal morphology of Nile tilapia (Oreochromis
    niloticus). Two recirculating aquaculture systems were used to create the

  17. High sensitivity and accuracy dissolved oxygen (DO) detection by using PtOEP/poly(MMA-co-TFEMA) sensing film

    Science.gov (United States)

    Zhang, Ke; Zhang, Honglin; Wang, Ying; Tian, Yanqing; Zhao, Jiupeng; Li, Yao

    2017-01-01

    Fluorinated acrylate polymer has received great interest in recent years due to its extraordinary characteristics such as high oxygen permeability, good stability, low surface energy and refractive index. In this work, platinum octaethylporphyrin/poly(methylmethacrylate-co-trifluoroethyl methacrylate) (PtOEP/poly(MMA-co-TFEMA)) oxygen sensing film was prepared by the immobilizing of PtOEP in a poly(MMA-co-TFEMA) matrix and the technological readiness of optical properties was established based on the principle of luminescence quenching. It was found that the oxygen-sensing performance could be improved by optimizing the monomer ratio (MMA/TFEMA = 1:1), tributylphosphate(TBP, 0.05 mL) and PtOEP (5 μg) content. Under this condition, the maximum quenching ratio I0/I100 of the oxygen sensing film is obtained to be about 8.16, Stern-Volmer equation is I0/I = 1.003 + 2.663[O2] (R2 = 0.999), exhibiting a linear relationship, good photo-stability, high sensitivity and accuracy. Finally, the synthesized PtOEP/poly(MMA-co-TFEMA) sensing film was used for DO detection in different water samples.

  18. Horizontal transport and seasonal distribution of nutrients, dissolved oxygen and chlorophyll -a in the Gulf of Nicoya, Costa Rica: a tropical estuary

    Science.gov (United States)

    Kress, Nurit; Coto, Sandra Leon; Brenes, Carlos L.; Brenner, Stephen; Arroyo, Guillermo

    2002-01-01

    The distributions of salinity, temperature, nutrients, dissolved oxygen and chlorophyll -a (chl -a) concentrations in the Gulf of Nicoya, Costa Rica, during the rainy and dry seasons are presented. In the rainy season, the entire Gulf is strongly stratified due to high riverine discharge; surface temperature decreases and salinity increases towards the sea and most of the Gulf is undersaturated with dissolved oxygen. In the dry season, the Gulf is still stratified although without the strong fresh water signal identified in the rainy season. The lowest surface temperatures appear in the middle of the Gulf whilst the salinity generally decreases towards the upper Gulf. Only the deep waters (below 30 m depth) are undersaturated with dissolved oxygen. In the lower Gulf, oversaturation reaches up to 134% at the surface. The concentration of Si(OH) 4 in the Gulf is much higher during the rainy season than in the dry season, whilst PO 4 is not seasonally dependent. Surficial concentrations of NO 3+NO 2 in the upper Gulf are higher in the dry season than in the rainy season; whilst in most of the lower Gulf, the concentrations are lower in the dry season. Surficial chl -a concentrations in the Gulf are higher in the rainy season, in particular, close to the Tarcoles outflow. A three-component mixing diagram describes the spatial distribution of the nutrients, during both seasons. Riverine waters from the Tempisque (high nutrients and low salinity) are mixed with surface waters from the lower Gulf (higher salinity and lower nutrients). The resulting water then mixes with oceanic water. Salinity in relation to PO 4 is seasonally dependent in the upper Gulf; the riverine end member during the dry season is higher, by a factor of 4, than during the rainy season. There is a significant correlation between NO 3+NO 2 and salinity only during the dry season in the upper Gulf; this is probably a result of phytoplankton consumption of N, in the rainy season. The calculated NO 3+NO

  19. Wildfire Impacts on Water Quality, Macroinvertebrates and Trout: An Initial Survey After the West Fork Complex Fire in the Upper Rio Grande

    Science.gov (United States)

    Rust, A.; Knipper, K. R.; Randall, J.; Hogue, T. S.

    2014-12-01

    Forest fires affect water quality in the disrupted watershed, which can devastate the aquatic ecosystem including sensitive trout (Salmonidae) and macroinvertebrate species. The West Fork Fire Complex consumed 88,724 acres of forest in the state of Colorado during the summer of 2013. The majority (88%) of the burn area was comprised of Engelmann spruce (Picea engelmanii) trees killed previously by Spruce Beetle (Ips spp.). Damage to the soils was of moderate to high severity in the majority of the area (60%). The recent fire surrounded the Rio Grande, affecting water quality and habitat critical to insects and fish. The water quality of the Rio Grande (above and below the burn) and some of the effected tributaries is currently being monitored for both quality and quantity. Parameters important to the survival of aquatic life, such as flow, temperature, dissolved oxygen, pH, conductivity, total dissolved solids, total suspended solids, turbidity, nutrients, and suspended and dissolved metals are being monitored along the Rio Grande and in tributaries. Macroinvertebrate and fish populations are sampled in the same locations. First year observations showed the ecosystem to be relatively resilient, with stable water quality and survival of insects and fish. However, an intense monsoon season this summer is driving extensive sediments into tributaries from steep, severely burned hillslopes. These monsoon events have caused acute and dramatic fish kills, where hundreds of trout were reported killed in one tributary in a single day event. Turbidity was observed as high as 488 NTU in the impacted stream with fish kill, whereas the turbidity was 25 NTU in a neighboring tributary outside of the burn area. Salmonids can be negatively impacted by relatively low turbidity, with prior studies noting that the turbidity threshold for rainbow trout is 70 NTU. Continued monitoring of water quality, macroinvertebrate populations, and fish populations is being undertaken to determine

  20. Plankton communities and summertime declines in algal abundance associated with low dissolved oxygen in the Tualatin River, Oregon

    Science.gov (United States)

    Carpenter, Kurt D.; Rounds, Stewart A.

    2013-01-01

    Phytoplankton populations in the Tualatin River in northwestern Oregon are an important component of the dissolved oxygen (DO) budget of the river and are critical for maintaining DO levels in summer. During the low-flow summer period, sufficient nutrients and a long residence time typically combine with ample sunshine and warm water to fuel blooms of cryptophyte algae, diatoms, green and blue-green algae in the low-gradient, slow-moving reservoir reach of the lower river. Algae in the Tualatin River generally drift with the water rather than attach to the river bottom as a result of moderate water depths, slightly elevated turbidity caused by suspended colloidal material, and dominance of silty substrates. Growth of algae occurs as if on a “conveyor belt” of streamflow, a dynamic system that is continually refreshed with inflowing water. Transit through the system can take as long as 2 weeks during the summer low-flow period. Photosynthetic production of DO during algal blooms is important in offsetting oxygen consumption at the sediment-water interface caused by the decomposition of organic matter from primarily terrestrial sources, and the absence of photosynthesis can lead to low DO concentrations that can harm aquatic life. The periods with the lowest DO concentrations in recent years (since 2003) typically occur in August following a decline in algal abundance and activity, when DO concentrations often decrease to less than State standards for extended periods (nearly 80 days). Since 2003, algal populations have tended to be smaller and algal blooms have terminated earlier compared to conditions in the 1990s, leading to more frequent declines in DO to levels that do not meet State standards. This study was developed to document the current abundance and species composition of phytoplankton in the Tualatin River, identify the possible causes of the general decline in algae, and evaluate hypotheses to explain why algal blooms diminish in midsummer. Plankton

  1. Radical mechanisms of methyl vinyl ketone oligomerization through aqueous phase OH-oxidation: on the paradoxical role of dissolved molecular oxygen

    Directory of Open Access Journals (Sweden)

    P. Renard

    2013-01-01

    Full Text Available It is now accepted that one of the important pathways of Secondary Organic Aerosol (SOA formation occurs through aqueous phase chemistry in the atmosphere. However, the liquid phase chemical mechanisms leading to macromolecules are still not well understood. For α-dicarbonyl precursors, such as methylglyoxal and glyoxal, radical reactions through OH-oxidation produce oligomers, irreversibly and faster than accretion reactions. Methyl vinyl ketone (MVK was chosen in the present study as it is an α, β-unsaturated carbonyl that can undergo such reaction pathways in the aqueous phase and forms even high molecular weight oligomers. We present here experiments on the aqueous phase OH-oxidation of MVK, performed under atmospheric relevant conditions. Using NMR and UV absorption spectroscopy, high and ultra-high resolution mass spectrometry, we show that the fast formation of oligomers up to 1800 Da is due to radical oligomerization of MVK, and 13 series of oligomers (out of a total of 26 series are identified. The influence of atmospherically relevant parameters such as temperature, initial concentrations of MVK and dissolved oxygen are presented and discussed. In agreement with the experimental observations, we propose a chemical mechanism of OH-oxidation of MVK in the aqueous phase that proceeds via radical oligomerization of MVK on the olefin part of the molecule. This mechanism highlights the paradoxical role of dissolved O2: while it inhibits oligomerization reactions, it contributes to produce oligomerization initiator radicals, which rapidly consume O2, thus leading to the supremacy of oligomerization reactions after several minutes of reaction. These processes, together with the large ranges of initial concentrations investigated (60–656 μM of dissolved O2 and 0.2–20 mM of MVK show the fundamental role that O2 likely plays in atmospheric organic aerosol.

  2. Continuous-flow mass production of silicon nanowires via substrate-enhanced metal-catalyzed electroless etching of silicon with dissolved oxygen as an oxidant.

    Science.gov (United States)

    Hu, Ya; Peng, Kui-Qing; Liu, Lin; Qiao, Zhen; Huang, Xing; Wu, Xiao-Ling; Meng, Xiang-Min; Lee, Shuit-Tong

    2014-01-13

    Silicon nanowires (SiNWs) are attracting growing interest due to their unique properties and promising applications in photovoltaic devices, thermoelectric devices, lithium-ion batteries, and biotechnology. Low-cost mass production of SiNWs is essential for SiNWs-based nanotechnology commercialization. However, economic, controlled large-scale production of SiNWs remains challenging and rarely attainable. Here, we demonstrate a facile strategy capable of low-cost, continuous-flow mass production of SiNWs on an industrial scale. The strategy relies on substrate-enhanced metal-catalyzed electroless etching (MCEE) of silicon using dissolved oxygen in aqueous hydrofluoric acid (HF) solution as an oxidant. The distinct advantages of this novel MCEE approach, such as simplicity, scalability and flexibility, make it an attractive alternative to conventional MCEE methods.

  3. Scale up production of polyhydroxyalkanoate (PHA at different aeration, agitation and controlled dissolved oxygen levels in fermenter using Halomonas campisalis MCM B-1027

    Directory of Open Access Journals (Sweden)

    Pranav R Kshirsagar

    2012-08-01

    Full Text Available Production of biodegradable plastic, polyhydroxyalkanoate (PHA was demonstrated using culture of moderately haloakalitolerant Halomonas campisalis MCMB-1027. Production of PHA was carried out at different aeration (0.5-1, 1, and 1.5 vvm and agitation (100,150 and 200 rpm in 14 L fermenter. Maximum production of PHA was 40.69% on the basis of dry cell mass at 1 vvm and 100 rpm. Material balance over maltose revealed that aeration 1 vvm and agitation 100 rpm was optimum for conversion of utilized maltose into PHA. Controlled dissolved oxygen in the range 1-5% level during PHA accumulation phase facilitated to increase PHA content to 56.23%. A correlation equation was developed by fixing mass transfer coefficient (KLa and applied successfully for scale up production of PHA in 120 L fermenter. 1H NMR analysis showed percentage of HB and HV unit 95.83 and 4.17 respectively.

  4. Bathymetric, Velocity, Streamflow, and Dissolved Oxygen Data on the Pee Dee River near Bostick Boat Landing, Florence County, South Carolina, May-August 2007

    Science.gov (United States)

    Shelton, John M.

    2009-01-01

    Santee Cooper is planning to construct an electricity generating station in southeastern Florence County near the Kingsburg community. As part of this project, a water-intake structure will be constructed on the Pee Dee River near the Bostick Boat Landing, which is located east of the intersection of State secondary roads S-21-57 and S-21-66. Velocity, bathymetric, and dissolved oxygen data are needed to help determine the location for the water-intake structure. The U.S. Geological Survey (USGS), in cooperation with Santee Cooper, collected these data at three different flow regimes during the period of May through August 2007. Data were collected along 15 transects located at 50-foot intervals starting 400 feet upstream from the boat landing and continuing to 300 feet downstream from the boat landing. All data were geographically referenced using a differentially corrected global positioning system (GPS).

  5. Impact of Dissolved Oxygen during UV-Irradiation on the Chemical Composition and Function of CHO Cell Culture Media.

    Directory of Open Access Journals (Sweden)

    Sarah M Meunier

    Full Text Available Ultraviolet (UV irradiation is advantageous as a sterilization technique in the biopharmaceutical industry since it is capable of targeting non-enveloped viruses that are typically challenging to destroy, as well as smaller viruses that can be difficult to remove via conventional separation techniques. In this work, we investigated the influence of oxygen in the media during UV irradiation and characterized the effect on chemical composition using NMR and LC-MS, as well as the ability of the irradiated media to support cell culture. Chemically defined Chinese hamster ovary cell growth media was irradiated at high fluences in a continuous-flow UV reactor. UV-irradiation caused the depletion of pyridoxamine, pyridoxine, pyruvate, riboflavin, tryptophan, and tyrosine; and accumulation of acetate, formate, kynurenine, lumichrome, and sarcosine. Pyridoxamine was the only compound to undergo complete degradation within the fluences considered; complete depletion of pyridoxamine was observed at 200 mJ/cm2. Although in both oxygen- and nitrogen-saturated media, the cell culture performance was affected at fluences above 200 mJ/cm2, there was less of an impact on cell culture performance in the nitrogen-saturated media. Based on these results, minimization of oxygen in cell culture media prior to UV treatment is recommended to minimize the negative impact on sensitive media.

  6. 木薯酒精发酵过程关键参数的测控研究%Dissolved Oxygen Measure and Control in Cassava Alcohol Fermentation Process

    Institute of Scientific and Technical Information of China (English)

    王章利; 谭永红

    2009-01-01

    木薯酒精发酵过程是一个时变、非线形和多参数影响的动态过程.时发酵过程的关键参数如pH值、溶解氧的测控是非常重要的.设计了由工控机和西门子公司的PLC构成的发酵过程两级计算机集散系统,实现对酒精发酵过程中关键参数pH值、溶解氧等的数据采集与监视,同时利用该系统实现对采集到的数据进行分析与处理,从而达到最终的控制目的.%Cassava Alcohol Fermentation Process is a non-linear,time-varying dynamic process with infection by many parameter.Si-multaneity,it's very important to measure and control pivotal parameter such as pH and DO (Dissolved Oxygen).This paper de-signs the DCS(Distributing Control System) which is made by industry PC and SIEMENS PLC.This system can achieve to col-lection and stakeout the pivotal parameter like pH and DO in alcohol fermentation.At the same time,using the system imple-mentation of the dissolved oxygen data collected for analysis and treatment,So as to achieve the ultimate control purposes.

  7. Modeling the effect of land use/land cover on nitrogen, phosphorous and dissolved oxygen loads in the Velhas River using the concept of exclusive contribution area.

    Science.gov (United States)

    de Oliveira, Lília Maria; Maillard, Philippe; de Andrade Pinto, Éber José

    2016-06-01

    Non-point source water pollution is a major problem in most parts of the world, but is also very difficult to quantify and control since it is not easily separated from point sources and can theoretically originate from the whole watershed. In this article, we evaluate the relationship between land use and land cover and four water pollution parameters in a watershed in Southeast Brazil. The four parameters are nitrate, total ammonia nitrogen, total phosphorous, and dissolved oxygen. To help concentrate on non-point source pollution, only data from the wet seasons of the time period (2001-2013) were analysed, based on the fact that precipitation causes runoff which is the main cause of diffuse pollution. The parameters measured were transformed into loads, which were in turn associated with an exclusive contribution area, so that every measuring station could be considered independent. Analyses were also performed on riparian zones of different widths to verify if the effect of the land cover on the water quality of the stream decreases with the increased distance. Pearson correlation coefficients indicate that urban areas and agriculture/pasture tend to worsen water quality (source). Conversely, forest and riparian areas have a reducing effect on pollution (sink). The best results were obtained for total ammonia nitrogen and dissolved oxygen using the whole exclusive contribution areas with determination coefficients better than R (2)≈0.8. Nitrate and total phosphorous did not produce valid models. We suspect that the transformation delay from total ammonia nitrogen to nitrate might be an important factor for the poor result for this parameter. For phosphorous, we think that the phosphorous sink in the bottom sediment might be the most limiting factor explaining the failure of our models.

  8. Influence of the adipate and dissolved oxygen concentrations on the beta-lactam production during continuous cultivations of a Penicillium chrysogenum strain expressing the expandase gene from Streptomyces clavuligerus

    DEFF Research Database (Denmark)

    Robin, Jarno Jacky Christian; Bonneau, S.; Schipper, D.

    2003-01-01

    The influence of adipate concentration and dissolved oxygen on production of adipoyl-7-aminodeacetoxycephalosporanic acid (ad-7-ADCA) by a recombinant strain of Penicillium chrysogenum expressing the expandase gene from Streptomyces clavuligerus was studied in glucose-limited continuous cultures....... Operating conditions were maintained constant but the adipate and dissolved oxygen concentrations (DOC) were varied separately in a range from I to 37.5 g l(-1) and from 2% to 125% air saturation (%AS), respectively. The total beta-lactams specific productivity, r(p) (total) was not significantly changed...

  9. Role of Chloride Ion and Dissolved Oxygen in Electrochemical Corrosion of AA5083-H321 Aluminum-Magnesium Alloy in NaCl Solutions under Flow Conditions

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Flow-induced corrosion consists electrochemical and mechanical components. The present paper has to assessed the role of chloride ion and dissolved oxygen in the electrochemical component of flow induced corrosion for AA5083-H321 aluminum-magnesium alloy which is extensively used in the construction of high-speed boats, submarines, hovercrafts, and desalination systems, in NaCl solutions. Electrochemical tests were carried out at flow velocities of 0, 2, 5, 7 and 10 m/s, in aerated and deaerated NaCl solutions with different sodium chloride concentrations. The results showed that the high rate of oxygen reduction under hydrodynamic conditions causes an increase in the density of pits on the surface. The increase of chloride ions concentration under flow conditions accelerates the rate of anodic reactions, but have no influence on the cathodic reactions. Thus, in the current work, it was found that under flow conditions, due to the elimination of corrosion products inside the pits, corrosion resistance of the alloy is increased.

  10. Roles of singlet oxygen and triplet excited state of dissolved organic matter formed by different organic matters in bacteriophage MS2 inactivation

    KAUST Repository

    Rosado-Lausell, Sahid L.

    2013-09-01

    Inactivation of bacteriophage MS2 by reactive oxygen species (ROS) and triplet excited state of dissolved organic matter (3DOM*) produced by irradiation of natural and synthetic sensitizers with simulated sunlight of wavelengths greater than 320nm was investigated. Natural sensitizers included purified DOM isolates obtained from wastewater and river waters, and water samples collected from Singapore River, Stamford Canal, and Marina Bay Reservoir in Singapore. Linear correlations were found between MS2 inactivation rate constants (kobs) and the photo-induced reaction rate constants of 2,4,6-trimethylphenol (TMP), a probe compound shown to react mainly with 3DOM*. Linear correlations between MS2 kobs and singlet oxygen (1O2) concentrations were also found for both purified DOM isolates and natural water samples. These correlations, along with data from quenching experiments and experiments with synthetic sensitizers, Rose Bengal (RB), 3\\'-methoxyacetophenone (3\\'-MAP), and nitrite (NO2-), suggest that 1O2, 3DOM*, and hydroxyl radicals (•OH) could inactivate bacteriophage MS2. Linear correlations between MS2 kobs and Specific Ultraviolet Absorption determined at 254nm (SUVA254) were also found for both purified DOM isolates and natural samples. These results suggest the potential use of TMP as a chemical probe and SUVA254 as an indicator for virus inactivation in natural and purified DOM water samples. © 2013 Elsevier Ltd.

  11. [Comparison and application of biological indices of macroinvertebrates in river health assessment].

    Science.gov (United States)

    Geng, Shi-Wei; Qu, Xiao-Dong; Zhang, Yuan; Lin, Kun-De

    2012-07-01

    The different biological indices usually result in different results in the river health assessment. It is imperative and valuable to identify the correlation among different indices and their applicability for assessing stream health. In this study, totally five biological indices were selected and compared in the investigation of macroinvertebrate communities in the Taizi river. The results showed significant correlations among the five indices. However, due to the difference in health rating criteria for each biological index, different results of health ratings were obtained when different indices were used. The responding sensitivities to disturbance caused by different types of human activities were studied for each index to determine their applicability in assessment of river health. The data indicated that the BI index had significant correlations with land use and dissolved oxygen and was a good indicator for these two types of disturbance. The FBI index could well reflect the acid and ammonia contamination of the investigated stream. Strong negative correlation was found between the ASPT index and several water quality parameters concerning oxygen consumption. The B-IBI index had a significant negative correlation with the total nitrogen concentration, being a good indicator for nitrogen contamination. Besides, the B-IBI index was also significantly correlated to disturbance caused by other types of human activities and can be used as an indicator for both land use and aquatic pollution. To be concluded, the BI index and ASPT index can be individually used to assess the land use of a riverine and the impact of hydrochemical index on the ecosystems, whereas the B-IBI index could be a suitable indicator for evaluating the stream health correlated with various human activities.

  12. Evaluation of Primary Production in the Lower Amazon River Based on a Dissolved Oxygen Stable Isotopic Mass Balance

    Energy Technology Data Exchange (ETDEWEB)

    Gagne-Maynard, William C.; Ward, Nicholas D.; Keil, Richard G.; Sawakuchi, Henrique O.; Da Cunha, Alan C.; Neu, Vania; Brito, Daimio C.; Da Silva Less, Diani F.; Diniz, Joel E. M.; De Matos Valerio, Aline; Kampel, Milton; Krusche, Alex V.; Richey, Jeffrey E.

    2017-02-07

    The Amazon River outgasses nearly an equivalent amount of CO2 as the rainforest sequesters on an annual basis due to microbial decomposition of terrigenous and aquatic organic matter. Most research performed in the Amazon has been focused on unraveling the mechanisms driving CO2 production since the recognition of a persistent state of CO2 supersaturation. However, although the river system is clearly net heterotrophic, the interplay between primary production and respiration is an essential aspect to understanding the overall metabolism of the ecosystem and potential transfer of energy up trophic levels. For example, an efficient ecosystem is capable of both decomposing high amounts of organic matter at lower trophic levels, driving CO2 emissions, and accumulating energy/biomass in higher trophic levels, stimulating fisheries production. Early studies found minimal evidence for primary production in the Amazon River mainstem and it has since been assumed that photosynthesis is strongly limited by low light penetration attributed to the high sediment load. Here, we test this assumption by measuring the stable isotopic composition of O218O-O2) and O2 saturation levels in the lower Amazon River from Óbidos to the river mouth and its major tributaries, the Xingu and Tapajós rivers, during high and low water periods. An oxygen mass balance model was developed to estimate the input of photosynthetic oxygen in the discrete reach from Óbidos to Almeirim, midway to the river mouth. Based on the oxygen mass balance we estimate that primary production occurred at a rate of 0.39 ± 0.24 g O m3 d-1 at high water and 1.02 ± 0.55 g O m3 d-1 at low water. This translates to 41 ± 24% of the rate of O2 drawdown via respiration during high water and 67 ± 33% during low water. These primary production rates are 2-7 times higher than

  13. Benthic Macroinvertebrate Communities in Agriculturally Impaired Streams

    Directory of Open Access Journals (Sweden)

    Virginija Pliuraite

    2009-10-01

    Full Text Available Normal 0 false false false EN-US X-NONE X-NONE This work presents research into the taxonomic composition of macroinvertebrate communities in streams that are under the influence of agricultural pollution A total of 67 macroinvertebrate taxa (including 61 identified species belonging to 40 families have been identified in the explored streams. The greatest species richness is recorded for the Trichoptera (18 species/1 taxa and Mollusca (12 species. The molluscs Gyraulus albus, amphipods Gammarus pulex, caddisflies Hydropsyche pellucidula and oligochaetes are detected in all examined streams. There, the number of total benthic macroinvertebrate taxa is highly variable, ranging from 16 to 40. Results show that the examined streams depending on the benthic macroinvertebrate taxonomic composition and predominance of seperate macroinvertebrate groups undergo different pollution. Intolerant to pollution taxa such as Plecoptera, which are the most sensitive to pollution insects, have been found only in 5 of 12 examined streams and in low abundances. The richness and diversity of macrozoobenthos in some streams appear to respond to the water quality deterioration. The present study has found out that in the stream where the total macroinvertebrate taxa, EPT taxa richness are the lowest and a relative abundance of gatherers is the highest, the values of NH4-N, NO3-N, total N, PO4-P and total P in the stream water are the highest, too.

  14. Photocatalytic generation of dissolved oxygen and oxyhemoglobin in whole blood based on the indirect interaction of ultraviolet light with a semiconducting titanium dioxide thin film

    Science.gov (United States)

    Gilbert, Richard J.; Carleton, Linda M.; Dasse, Kurt A.; Martin, Peter M.; Williford, Ralph E.; Monzyk, Bruce F.

    2007-10-01

    Most current artificial lung technologies require the delivery of oxygen to the blood via permeable hollow fibers, depending on membrane diffusivity and differential partial pressure to drive gas exchange. We have identified an alternative approach in which dissolved oxygen (DO) is generated directly from the water content of blood through the indirect interaction of ultraviolet (UV) light with a semiconducting titanium dioxide thin film. This reaction is promoted by photon absorption and displacement of electrons from the photoactive film and yields a cascading displacement of electron "holes" to the aqueous interface resulting in the oxidation of water molecules to form DO. Anatase TiO2 (photocatalyst) and indium tin oxide (ITO) (electrically conductive and light transparent) coatings were deposited onto quartz flow-cell plates by direct current reactive magnetron sputtering. The crystal structure of the films was evaluated by grazing incidence x-ray diffraction, which confirmed that the primary crystal phase of the TiO2 thin film was anatase with a probable rutile secondary phase. Surface topology and roughness were determined by atomic force microscopy, demonstrating a stochastically uniform array of nanocrystallites. UV illumination of the titanium dioxide thin film through the quartz/ITO surface resulted in the rapid increase of DO and oxyhemoglobin in adjacent flowing blood on the opposite TiO2 surface at a rate of 1.0×10-5 mmol O2/s. The rate of oxyhemoglobin generation was linearly proportional to residence time adjacent to the photoactive surface in a flow-through test cell under steady-state conditions. Preliminary biocompatibility for the proposed photocatalytic effect on whole blood demonstrated no increase in the rate of hemolysis or generation of toxic byproducts of photo-oxidation. These results demonstrate the feasibility and safety of employing optoelectronic mechanisms to promote oxygenation of hemoglobin in whole blood and provide

  15. Relationships between ecosystem metabolism, benthic macroinvertebrate densities, and environmental variables in a sub-arctic Alaskan river

    Science.gov (United States)

    Benson, Emily R.; Wipfli, Mark S.; Clapcott, Joanne E.; Hughes, Nicholas F.

    2013-01-01

    Relationships between environmental variables, ecosystem metabolism, and benthos are not well understood in sub-arctic ecosystems. The goal of this study was to investigate environmental drivers of river ecosystem metabolism and macroinvertebrate density in a sub-arctic river. We estimated primary production and respiration rates, sampled benthic macroinvertebrates, and monitored light intensity, discharge rate, and nutrient concentrations in the Chena River, interior Alaska, over two summers. We employed Random Forests models to identify predictor variables for metabolism rates and benthic macroinvertebrate density and biomass, and calculated Spearman correlations between in-stream nutrient levels and metabolism rates. Models indicated that discharge and length of time between high water events were the most important factors measured for predicting metabolism rates. Discharge was the most important variable for predicting benthic macroinvertebrate density and biomass. Primary production rate peaked at intermediate discharge, respiration rate was lowest at the greatest time since last high water event, and benthic macroinvertebrate density was lowest at high discharge rates. The ratio of dissolved inorganic nitrogen to soluble reactive phosphorus ranged from 27:1 to 172:1. We found that discharge plays a key role in regulating stream ecosystem metabolism, but that low phosphorous levels also likely limit primary production in this sub-arctic stream.

  16. The mitigation of flow-accelerated corrosion in the feedwater systems of nuclear reactors. The influence of dissolved oxygen under different operating conditions

    Energy Technology Data Exchange (ETDEWEB)

    Lister, Derek H.; Liu, Lihui [New Brunswick Univ., Fredericton, NB (Canada). Dept. of Chemical Engineering; Feicht, Andrew D. [New Brunswick Univ., Fredericton, NB (Canada). Center for Nuclear Energy Research; Fujiwara, Kazutoshi [Central Research Institute of the Electric Power Industry (CRIEPI), Tokyo (Japan); Khatibi, Mahsa [Toronto Univ., ON (Canada); Ohira, Taku [Japan Atomic Power Co. (JAPC), Tokyo (Japan). Plant Management Dept.; Uchida, Shunsuke [Japan Atomic Energy Agency, Tokai, Ibaraki (Japan)

    2011-04-15

    In order to improve our understanding of the flow-accelerated corrosion (FAC) of carbon steel piping in feedwater systems, a collaborative research program between Japan and Canada has investigated the combined effects of system operating parameters. A major objective was to optimize techniques for minimizing degradation; accordingly, we report here the influence of dissolved oxygen on FAC rate under a range of conditions as examined in the laboratory with a high-temperature water loop. Most of the experiments were done at 140 C in neutral water, in ammoniated water at pH{sub 25} {sub C} 9.2 and in ammoniated water at pH{sub 25} {sub C} 9.2 with 100 {mu}g . kg{sup -1} hydrazine. Several flow rates were imposed and two grades of carbon steel were employed for test probes: one containing 0.019 % chromium and the other containing 0.001 % chromium. Probes were designed to monitor continuously both FAC (by an electrical resistance technique) and electrochemical corrosion potential, ECP (relative to a Ag/AgCl reference electrode). During a typical experiment, probes of different diameters were installed in series. Downstream of the ''resistance probes'' to measure FAC, removable probes for detailed surface examination by techniques such as laser-Raman microscopy, scanning-electron microscopy and energy-dispersive x-ray analysis were also installed. In neutral water, FAC rates reached {proportional_to}6 mm per year and were apparently controlled by mass transfer, which led to a numerical correlation with fluid shear stress at the tube wall. The steel with the lower chromium content had a greater FAC rate by a factor of about 2.4. An oxygen concentration of almost 40 {mu}g . kg{sup -1} was required to stifle FAC. In ammoniated water, FAC rates were relatively low and correlations depending on mass transfer were dubious. Hydrazine reduced the FAC rate, possibly because it affected the pH locally at the metal surface. It also increased the stifling oxygen

  17. Decrease of dissolved oxygen after the mid-1980s in the western North Pacific subtropical gyre along the 137°E repeat section

    Science.gov (United States)

    Takatani, Yusuke; Sasano, Daisuke; Nakano, Toshiya; Midorikawa, Takashi; Ishii, Masao

    2012-06-01

    The Japan Meteorological Agency has acquired dissolved oxygen (DO) concentration data each year since 1967 along the 137°E repeat section in the western North Pacific. In this data set we found significant regional temporal trends of decreasing or increasing DO concentrations on various isopycnal surfaces. DO decreases were particularly significant after the mid-1980s in the subtropical gyre; mean rates of DO change at 20-25°N for 1985-2010 were -0.28 ± 0.08 μmol kg-1 yr-1 on 25.5 σθ in North Pacific Subtropical Mode Water (NPSTMW), -0.36 ± 0.08 μmol kg-1 yr-1 on 26.8 σθ in North Pacific Intermediate Water (NPIW), and -0.23 ± 0.04 μmol kg-1 yr-1 on 27.3 σθ in the O2 minimum Layer (OML). The cause of DO decrease differed among isopycnal surfaces. On density surfaces shallower than 26.0 σθ (less than about 400 m), the deepening of isopycnal surfaces and decline of oxygen solubility due to ocean warming have had the greatest influence. In particular, between 25.2 σθ and 25.8 σθ near the NPSTMW their combined contributions accounted for >50% of the DO decrease. In the NPIW core at roughly 26.8 σθ (˜700 m), the decline in DO was attributable to the DO decrease in the formation region. In the OML between 27.0 σθ and 27.3 σθ (˜1000 m), the DO decrease likely resulted from an increase in westward transport of low O2 water due to strengthening of the subtropical gyre. The result of this study shows the importance of the long-term and high-frequency along the 137°E repeat section.

  18. Study of a two-stage growth of DHA-producing marine algae Schizochytrium limacinum SR21 with shifting dissolved oxygen level.

    Science.gov (United States)

    Chi, Zhanyou; Liu, Yan; Frear, Craig; Chen, Shulin

    2009-01-01

    The culture protocol of Schizochytrium limacinum SR 21, a known docosahexaenoic acid (DHA) producing marine algae was modified in this study to better fit fermentation parameters, particularly control of dissolved oxygen (DO) to the known reproductive and growth biology of the microorganism. The cultures controlled at 50% DO saturation produced a cell density of 181 million cells/ml, whereas cultures with 10% DO produced only 98.4 million cells/ml. A fixed-agitation rate of 150 rpm resulted in an even lower density of 22.5 million cells/ml. Fifty percent DO saturation level led to a decreased pH, as well as a negative correlation with lipid accumulation, while low oxygen concentration was obligatory for lipid accumulation. This study indicated that high DO was preferred for the cells' reproduction via release of zoospores. Thus, the culture of S. limacinum SR21 should be best divided into two stages: (1) a cell-number-increasing stage in which cell reproduction and cell number increase with little increase in the size and weight of each cell; and (2) a cell-size-increasing stage in which cells stop reproduction but cell size enlarges due to lipids accumulation. With such a protocol, the production of algae biomass and DHA was improved to levels of 37.9 g/L and 6.56 g/L, respectively. The two-stage culture process could be potentially used not only for omega-3 PUFA production, but also in other single cell oil (SCO)-producing processes, including biodiesel production from algae.

  19. Impact of upwelling events on the sea water carbonate chemistry and dissolved oxygen concentration in the Gulf of Papagayo (Culebra Bay, Costa Rica: Implications for coral reefs

    Directory of Open Access Journals (Sweden)

    Tim Rixen

    2012-04-01

    Full Text Available The Gulf of Papagayo, Pacific coast of Costa Rica, is one of the three seasonal upwelling areas of Mesoamerica. In April 2009, a 29-hour experiment was carried out at the pier of the Marina Papagayo, Culebra Bay. We determined sea surface temperature (SST, dissolved oxygen concentration, salinity, pH, and the partial pressure of CO2 (pCO2. The aragonite saturation state (Ωa as well as the other parameters of the marine carbonate system such as the total dissolved inorganic carbon (DIC and the total alkalinity (TA were calculated based on the measured pH and the pCO2. The entrainment of subsurface waters raised the pCO2 up to 645 µatm. SSTs, dissolved oxygen concentrations decreased form 26.4 to 23.7°C and from 228 to 144 µmol l-1. Ωa dropped down to values of 2.1. Although these changes are assumed to reduce the coral growth, the main reef building coral species within the region (Pocillopora spp. and Pavona clavus reveal growth rates exceeding those measured at other sites in the eastern tropical Pacific. This implies that the negative impact of upwelling on coral growth might be overcompensated by an enhanced energy supply caused by the high density of food and nutrients and more favorable condition for coral growth during the non-upwelling season.El Golfo de Papagayo, costa Pacífica de Costa Rica, es una de las tres regiones de afloramiento estacional de Mesoamérica. Las características físicas y químicas del agua que aflora no habían sido estudiadas. Durante 29 horas en Abril 2009, se estudiaron la temperatura superficial del mar (TSM, la concentración de oxígeno disuelto, salinidad, pH y la presión parcial de CO2 (pCO2, en la Marina Papagayo, Bahía Culebra. Con base en las mediciones de pH y pCO2 se calculó el estado de saturación de la aragonita (Ω y otros parámetros del sistema de carbonatos como lo es el carbono orgánico disuelto (COD y la alcalinidad total (AT. Los resultados indican que el arrastre por convecci

  20. Improved 5-Aminolevulinic Acid Production with Recombinant Escherichia coli by a Short-term Dissolved Oxygen Shock in Fed-batch Fermentation

    Institute of Scientific and Technical Information of China (English)

    杨俊; 朱力; 傅维琦; 林逸君; 林建平; 岑沛霖

    2013-01-01

    5-Aminolevulinic acid (ALA) is a common precursor for tetrapyrrole compounds in all kinds of organ-isms and has wide applications in agriculture and medicines. In this study, a new strategy, i.e. short-term dissolved oxygen (DO) shock during aerobic fermentation, was introduced to produce 5-aminolevulinic acid with a recombi-nant E. coli. Effects of duration time of DO shock operation on plasmid concentration, intracellular ALA synthase (ALAS) activity and ALA production were investigated in Erlenmeyer shake flasks. The results indicated that both ALAS activity and ALA yield were enhanced in an anaerobic operation of 45 min in the early exponential phase during fermentation, while they decreased when the anaerobic operation time was further increased to 60 min. The DO shock protocol was confirmed with the fed-batch fermentation in a 15 L fermenter and the ALA production achieved 9.4 g·L-1 (72 mmol·L-1), which is the highest yield in the fermentation broth reported up to now.

  1. Effects of pH, Temperature, Dissolved Oxygen, and Flow Rate on Phosphorus Release Processes at the Sediment and Water Interface in Storm Sewer

    Directory of Open Access Journals (Sweden)

    Haiyan Li

    2013-01-01

    Full Text Available The effects of pH, temperature, dissolved oxygen (DO, and flow rate on the phosphorus (P release processes at the sediment and water interface in rainwater pipes were investigated. The sampling was conducted in a residential storm sewer of North Li Shi Road in Xi Cheng District of Beijing on August 3, 2011. The release rate of P increased with the increase of pH from 8 to 10. High temperature is favorable for the release of P. The concentration of total phosphorus (TP in the overlying water increased as the concentration of DO decreased. With the increase of flow rate from 0.7 m s−1 to 1.1 m s−1, the concentration of TP in the overlying water increased and then tends to be stable. Among all the factors examined in the present study, the flow rate is the primary influence factor on P release. The cumulative amount of P release increased with the process of pipeline runoff in the rainfall events with high intensities and shorter durations. Feasible measures such as best management practices and low-impact development can be conducted to control the P release on urban sediments by slowing down the flow rate.

  2. Influences of ammonia-nitrogen and dissolved oxygen on lysosomal integrity in green-lipped mussel Perna viridis: laboratory evaluation and field validation in Victoria Harbour, Hong Kong.

    Science.gov (United States)

    Fang, J K H; Wu, R S S; Chan, A K Y; Yip, C K M; Shin, P K S

    2008-12-01

    Lysosomal integrity in mussels has been applied as a biomarker to detect the pollution of trace organics and metals in the natural environments. However, few studies have examined the effects of water quality on the response of lysosomal integrity, in particular total ammonia-nitrogen (TAN) and dissolved oxygen (DO). This study demonstrated that high level of TAN (2.0mg/l) and low DO (2.5mg O(2)/l) could significantly reduce the lysosomal integrity in green-lipped mussel Perna viridis, respectively by 33% and 38%, whereas the mussel lysosomal integrity decreased by 70% in the combined treatment of TAN and low DO under laboratory conditions after one week. The mussel lysosomal integrity of all treatment groups could return to the control level after a three week recovery period. In the field validation in Victoria Harbour, Hong Kong during an one-year study period, lysosomal integrity in P. viridis identified the cleanest site east to the harbour, where the lowest TAN and highest DO concentrations were found. While lysosomal integrity in mussels seemed not affected by seasonal changes, approximately 40% of the variation of this biomarker could be attributable to the changes in TAN and DO in seawater. In conclusion, the response of the mussel lysosomal integrity can be confounded by both TAN and DO prevailing in the natural environments and thus caution must be exercised in relating the observed changes in lysosomal integrity to any specific pollutant in coastal water quality monitoring studies.

  3. The acetylation degree of alginates in Azotobacter vinelandii ATCC9046 is determined by dissolved oxygen and specific growth rate: studies in glucose-limited chemostat cultivations.

    Science.gov (United States)

    Castillo, Tania; Galindo, Enrique; Peña, Carlos F

    2013-07-01

    Alginates are polysaccharides that may be used as viscosifiers and gel or film-forming agents with a great diversity of applications. The alginates produced by bacteria such as Azotobacter vinelandii are acetylated. The presence of acetyl groups in this type of alginate increases its solubility, viscosity, and swelling capability. The aim of this study was to evaluate, in glucose-limited chemostat cultivations of A. vinelandii ATCC9046, the influence of dissolved oxygen tension (DO) and specific growth rate (μ) on the degree of acetylation of alginates produced by this bacterium. In glucose-limited chemostat cultivations, the degree of alginate acetylation was evaluated under two conditions of DO (1 and 9 %) and for a range of specific growth rates (0.02-0.15 h⁻¹). In addition, the alginate yields and PHB production were evaluated. High DO in the culture resulted in a high degree of alginate acetylation, reaching a maximum acetylation degree of 6.88 % at 9 % DO. In contrast, the increment of μ had a negative effect on the production and acetylation of the polymer. It was found that at high DO (9 %) and low μ, there was a reduction of the respiration rate, and the PHB accumulation was negligible, suggesting that the flux of acetyl-CoA (the acetyl donor) was diverted to alginate acetylation.

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

    Science.gov (United States)

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

    2013-01-01

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

  5. Effect of streambed substrate on macroinvertebrate biodiversity

    Institute of Scientific and Technical Information of China (English)

    Xuehua DUAN; Zhaoyin WANG; Shimin TIAN

    2008-01-01

    Macroinvertebrates are important components of stream ecosystems, and are often used as indicator spe-cies for the assessment of river ecology. Numerous studies have shown that substrate is the primary physical envir-onmental variable affecting the taxa richness and density of macroinvertebrates. The aim of this work is to study the effects of the characteristics of streambed substrate, such as grain size, shape, and roughness, on the composition and biodiversity of macroinvertebrates. A field experi-ment was done on the Juma River, a second-order moun-tain stream in northern China. Substrata of cobbles, hewn stones, pebbles, coarse sand, and fine sand were used to replace the original gravel and sand bed in a stretch of 30 m in length. The sampling results indicated that the macroinvertebrate assemblage is significantly affected by the grain size, porosity and interstitial dimension of the substrate, while it is rarely affected by the shape and the surface roughness of the experimental substrata. Macroinvertebrate compositions in cobbles and hewn stones were stable and changed least over time. The taxa richness and density of individuals in the substrata of cobbles, hewn stones, and pebbles are much higher than in those of the coarse sand and fine sand.

  6. Modeling Aquatic Macroinvertebrate Richness Using Landscape Attributes

    Directory of Open Access Journals (Sweden)

    Marcia S. Meixler

    2015-01-01

    Full Text Available We used a rapid, repeatable, and inexpensive geographic information system (GIS approach to predict aquatic macroinvertebrate family richness using the landscape attributes stream gradient, riparian forest cover, and water quality. Stream segments in the Allegheny River basin were classified into eight habitat classes using these three landscape attributes. Biological databases linking macroinvertebrate families with habitat classes were developed using life habits, feeding guilds, and water quality preferences and tolerances for each family. The biological databases provided a link between fauna and habitat enabling estimation of family composition in each habitat class and hence richness predictions for each stream segment. No difference was detected between field collected and modeled predictions of macroinvertebrate families in a paired t-test. Further, predicted stream gradient, riparian forest cover, and total phosphorus, total nitrogen, and suspended sediment classifications matched observed classifications much more often than by chance alone. High gradient streams with forested riparian zones and good water quality were predicted to have the greatest macroinvertebrate family richness and changes in water quality were predicted to have the greatest impact on richness. Our findings indicate that our model can provide meaningful landscape scale macroinvertebrate family richness predictions from widely available data for use in focusing conservation planning efforts.

  7. 溶氧控制对黄色短杆菌YILW合成L-异亮氨酸的影响%Effect of Dissolved Oxygen Control on L-isoleucine Synthesis by Brevibacterium flavum YIL W

    Institute of Scientific and Technical Information of China (English)

    白亚磊; 徐庆阳; 谢希贤; 陈宁

    2011-01-01

    The condition of dissolved oxygen of L-isoleucine synthesis in Brevibacterium flavum YILW was explored,and the metabolic networks and metabolic flux balance model were constructed. The fermentation processes were studied on the condition of different dissolved oxygen in 30 L fermenter. The results show that high dissolved oxygen leads to bacterium growth. Higher production ratio of L-isoleucine maintains a long time under the condition of 15% dissolved oxygen. Thus the grading-controlling mode of dissolved oxygen was proposed: 25% dissolved oxygen concentration in the cell growth phase and 15% dissolved oxygen concentration in the phase of acid stable. Under this strategy,the yield of L-isoleucine is 31.8 g/L in 30 L fermenter in 60 h,and the conversion of sugar to acid is up to 18.3%. The vice acid is reduced significantly such as lactic, alanine. The results was demonstrated by using the method of metabolic flux analysis ,providing a theoretical basis for the in-depth understanding from the perspective of the amount of dissolved oxygen on L-isoleucine fermentation , and providing a theoretical guidance for further optimization of L-isoleucine fermentation condition of dissolved oxygen.%对黄色短杆菌YILW合成L-异亮氨酸的发酵溶氧条件进行了探索,构建了该菌合成上L-异亮氨酸的代谢网络和代谢流平衡模型.在30 L发酵罐中考察了不同溶氧浓度下L-异亮氨酸发酵过程.研究结果表明:高溶氧浓度有利于菌体生长,15%溶氧浓度下产酸速率高且维持的时间长,有利于L-异亮氨酸的积累.为此提出了分段控氧模式:在菌体生长期,溶氧浓度控制为25%;在产酸稳定期,溶氧浓度控制为15%.在此溶氧控制模式下,在30 L发酵罐上补料分批发酵60 h.L-异亮氨酸产量可达31.8 g/L,糖酸转化率可达18.3%,且乳酸、丙氨酸等副酸明显减少.对此结果运用代谢流分析的方法进行论证,旨在从量的角度理解溶氧对L-异亮氨酸合

  8. Anthropogenic impact on water chemistry and benthic macroinvertebrate associated changes in a southern Nigeria stream.

    Science.gov (United States)

    Arimoro, Francis O; Odume, O Nelson; Uhunoma, Samson I; Edegbene, Augustine O

    2015-02-01

    The Ogba River in southern Nigeria is an important water resource for its riparian communities. This study evaluates impact of anthropogenic influences on the Ogba River using water chemistry and macroinvertebrate data sets obtained over a period of 6 months between January and June 2012. Four stations, stations 1-4, characterised by various human activities were chosen along the river. Organic wastes from domestic and industrial sources were the major point sources of pollutants. Station 2 where the municipal wastewater drains into the river had elevated values of flow velocity, BOD5, sulphate, phosphate, nitrate and sodium. Based on the canonical correspondence analysis (CCA), 5-day biochemical oxygen demand (BOD5), sulphate, nitrate and phosphate were the main factors that help to shape the macroinvertebrate assemblage structure of the Ogba River. Macroinvertebrates clustered strongly by stations than by seasons indicating that water quality differences between the stations were responsible for the observed differences in the biotic assemblage. The preponderance of naidid oligochaetes, baetid nymphs and certain tolerant dipteran taxa including chironomids and ceratopogonids at all four stations was an indication that the entire water body was stressed. The odonates were the single most abundant taxa; their dominance could be attributed to the vegetative nature of the stream, favouring odonate colonisation. Overall, the responses of macroinvertebrates to stress were reflected by the different assemblage structures recorded at the four study stations. Substrate and microhabitat obliteration and poor water quality appeared to be the factors responsible for the observed assemblage structure in the Ogba River.

  9. Prediction of dissolved oxygen concentration in hypoxic river systems using support vector machine: a case study of Wen-Rui Tang River, China.

    Science.gov (United States)

    Ji, Xiaoliang; Shang, Xu; Dahlgren, Randy A; Zhang, Minghua

    2017-07-01

    Accurate quantification of dissolved oxygen (DO) is critically important for managing water resources and controlling pollution. Artificial intelligence (AI) models have been successfully applied for modeling DO content in aquatic ecosystems with limited data. However, the efficacy of these AI models in predicting DO levels in the hypoxic river systems having multiple pollution sources and complicated pollutants behaviors is unclear. Given this dilemma, we developed a promising AI model, known as support vector machine (SVM), to predict the DO concentration in a hypoxic river in southeastern China. Four different calibration models, specifically, multiple linear regression, back propagation neural network, general regression neural network, and SVM, were established, and their prediction accuracy was systemically investigated and compared. A total of 11 hydro-chemical variables were used as model inputs. These variables were measured bimonthly at eight sampling sites along the rural-suburban-urban portion of Wen-Rui Tang River from 2004 to 2008. The performances of the established models were assessed through the mean square error (MSE), determination coefficient (R (2)), and Nash-Sutcliffe (NS) model efficiency. The results indicated that the SVM model was superior to other models in predicting DO concentration in Wen-Rui Tang River. For SVM, the MSE, R (2), and NS values for the testing subset were 0.9416 mg/L, 0.8646, and 0.8763, respectively. Sensitivity analysis showed that ammonium-nitrogen was the most significant input variable of the proposal SVM model. Overall, these results demonstrated that the proposed SVM model can efficiently predict water quality, especially for highly impaired and hypoxic river systems.

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

    Science.gov (United States)

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

    2014-01-01

    Maintaining stability of low concentration ( 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.

  11. Primary production and carbon export rates across the subpolar N. Atlantic Ocean basin based on triple oxygen isotope and dissolved O2 and Ar gas measurements

    Science.gov (United States)

    Quay, P.; Stutsman, J.; Steinhoff, T.

    2012-06-01

    Gross photosynthetic O2 production (GOP) rates in the subpolar North Atlantic Ocean were estimated using the measured isotopic composition of dissolved oxygen in the surface layer on samples collected on nine transits of a container ship between Great Britain and Canada during March 2007 to June 2008. The mean basin-wide GOP rate of 226 ± 48 mmol O2 m-2 d-1 during summer was double the winter rate of 107 ± 41 mmol O2 m-2 d-1. Converting these GOP rates to equivalent 14C-based PP (14C-PPeqv) yielded rates of 1005 ± 216 and 476 ± 183 mg C m-2 d-1 in summer and winter, respectively, that generally agreed well with previous 14C-based PP estimates in the region. The 14C-PPeqv estimates were 1-1.6× concurrent satellite-based PP estimates along the cruise track. A net community production rate (NCP) of 87 ± 12 mmol O2 m-2 d-1 (62 ± 9 mmol C m-2 d-1) and NCP/GOP of 0.35 ± 0.06 in the mixed layer was estimated from O2/Ar and 17Δ measurements (61°N 26°W) during spring bloom conditions in May 2008. Contrastingly, a much lower long-term annual mean NCP or organic carbon export rate of 2.8 ± 2.7 mol C m-2 yr-1 (8 ± 7 mmol C m-2 d-1) and NCP/GOP of 0.07 ± 0.06 at the winter mixed layer depth was estimated from 15 years of surface O2 data in the subpolar N. Atlantic collected during the CARINA program.

  12. Hydrodynamic features of the South Aegean Sea as derived from Argo T/S and dissolved oxygen profiles in the area

    Science.gov (United States)

    Kassis, Dimitris; Krasakopoulou, Evangelia; Korres, Gerasimos; Petihakis, George; Triantafyllou, George S.

    2016-09-01

    In this work, the hydrodynamic picture of the South Aegean Sea is examined through an analysis of recent measurements in its sub-basins, the Myrtoan and Cretan Sea. Both sub-basins play an important role in the water circulation, exchange, and formation processes that affect the dynamics of the whole Eastern Mediterranean. For the first time, Bio-Argo floats were deployed in the area under the Greek Argo Research Infrastructure coordination. The acquired profiles cover an almost 2-year period (November 2013-July 2015) and are compared with previous Argo profiles and the re-processed time-series data recorded from the E1-M3A POSEIDON observatory operating in the area since 2007. The spatio-temporal distribution of the physical and chemical properties in each sub-basin is examined. Dense water formation events are revealed in the northern part (Myrtoan), while the wider area can be characterized as pre-conditioned. In the Cretan basin, a strong inter-annual variability of the salinity field at intermediate and deep layers is observed that is associated with water exchange from its open boundaries. Furthermore, comparison of the dissolved oxygen (DO) distribution with physical water properties within both the mixed layer, and at greater depths, indicated that relatively high but still under-saturated DO values are more likely to be associated with convection events. Finally, an updated picture of the physical properties and the DO distribution is presented based on the last 5 years of measurements and the recent introduction of Bio-Argo floats with DO sensors in the area.

  13. Making sense of monitoring data using Jupyter Notebooks: a case study of dissolved oxygen dynamics across a fresh-estuarine gradient

    Science.gov (United States)

    Nelson, N.; Munoz-Carpena, R.

    2016-12-01

    In the presented exercise, students (advanced undergraduate-graduate) explore dissolved oxygen (DO) dynamics at three locations along a fresh-estuarine gradient of the Lower St. Johns River, FL (USA). Spatiotemporal DO trends along this gradient vary as a function of (1) tidal influence, and (2) biotic productivity (phytoplankton photosynthesis and community respiration). This combination of influences produces distinct DO behavior across each of the three hydrologically-connected sites. Through analysis of high frequency monitoring data, students are encouraged to think critically about the roles of physical and biological drivers of DO, and how the relative importance of these factors can vary among different locations within a single tidal waterbody. Data from each of the three locations along the river are downloaded with CUAHSI HydroClient, and analysis is performed with a Python-enabled Jupyter Notebook that has been specifically created for this assignment. Jupyter Notebooks include annotated code organized into blocks that are executed one-at-a-time; this format is amenable to classroom teaching, and provides an approachable introduction to Python for inexperienced coders. The outputs from each code block (i.e. graphs, tables) are produced within the Jupyter Notebook, thus allowing students to directly interact with the code. Expected student learning outcomes include increased spatial reasoning, as well as greater understanding of DO cycling, spatiotemporal variability in tidal systems, and challenges associated with collecting and evaluating large data sets. Specific technical learning outcomes include coding in Python for data management and analysis using Jupyter notebooks. This assignment and associated materials are open-access and available on the Science Education Resource Center website.

  14. [Effects of dissolved oxygen in the oxic parts of A/O reactor on degradation of organic pollutants and analysis of microbial community for treating petrochemical wastewater].

    Science.gov (United States)

    Ding, Peng-Yuan; Chu, Li-Bing; Zhang, Nan; Wang, Xing; Wang, Jian-Long

    2015-02-01

    Effects of dissolved oxygen (DO) on the biodegradation of organic pollutants were investigated using A/O reactors for the treatment of actual petrochemical wastewater. Two A/O reactors, DO were controlled at 2-3 mg x L(-1) in the oxic parts of reactor A and 5-6 mg x L(-1) of reactor B, were operated in parallel for comparison. The nearly a half of year operation results showed that the effluent COD in reactor A (72.5 ± 14.8 mg x L(-1)) was slightly higher than that in reactor B (68.7 ± 14.6 mg x L(-1)) at a HRT of 20 h. The average COD removal efficiencies were 67.0% and 68.8%, respectively. The effluent ammonium concentration was maintained at 0.8 mg x L(-1) and approximately 95% of ammonium removal was achieved. The effluent BOD, concentration was lower than 5 mg x L(-1). This indicated that the organic pollutants could be degraded thoroughly by the A/O processes, which were affected slightly by DO. Results of 454 pyrosequencing analysis of the sludge in oxic parts showed that at the phylum levels, sequences belonged to Proteobacteria, Planctomycetes and Bacteroidetes were abundant with 58.7% and 59.2%, 14.7% and 12.7%, 10.8% and 12.4% of total bacterial sequences in reactor A and B, respectively. Ammonium oxidation bacteria Nitrosomonas, nitrite oxidizing bacteria Nitrospira and obligate aerobic bacteria were highly enriched in reactor B with high DO levels, while the anaerobic denitrifiers Azospira and Acidovora were highly enriched in reactor A with low DO levels. The identified bacteria belonged to genera Novosphingobium, Comamonas, Sphingobium and Altererythrobacter were reported to degrade PAHs, chloronitrobenzene, pesticides and petroleum, which contributed to the degradation of petrochemical wastewater.

  15. Determination of dissolved oxygen in saline waters applying mathematical methods and as a membrane electrode sensor; Determinacion de oxigeno disuelto en aguas salinas aplicando modelos matematicos y como sensor electrodo de membrana

    Energy Technology Data Exchange (ETDEWEB)

    Mayari, R.; Espinosa, M. C.; Ruiz, M. [Centro Nacional de Investigaciones Ceintificas. La Habana (Cuba); Romero, E. [Universidad de Huelva (Spain)

    2000-07-01

    This work shows as specific methodology for the determination of dissolved oxygen in saline waters that allows to consider the variations of temperature and of concentration of salts. Both factors influence the solubility of the gases in water, making possible in place measurements, in bodies of water with content of salts unto of the concentration of sea water, with greater dependability. The mathematical models obtained are shown, the errors due to equipment, as well as the results obtained when applying this methodology in saline waters with diverse levels of contamination this allows to discern when the decrease of dissolved oxygen levels is due to an increase in the salinity or to an increase in the contamination of the water body. (Author) 7 refs.

  16. Influence of the adipate and dissolved oxygen concentrations on the beta-lactam production during continuous cultivations of a Penicillium chrysogenum strain expressing the expandase gene from Streptomyces clavuligerus

    DEFF Research Database (Denmark)

    Robin, Jarno Jacky Christian; Bonneau, S.; Schipper, D.

    2003-01-01

    The influence of adipate concentration and dissolved oxygen on production of adipoyl-7-aminodeacetoxycephalosporanic acid (ad-7-ADCA) by a recombinant strain of Penicillium chrysogenum expressing the expandase gene from Streptomyces clavuligerus was studied in glucose-limited continuous cultures....... from 15 to 7%AS, r(p) (total) increased to 25 mumol g DW-1 h(-1), mainly due to a two-fold increase in the adipoyl-6-aminopenicillanic acid (ad-6-APA) specific productivity....

  17. Design and Calculation of Parameters of Dissolved Oxygen in Water Quality Detecting Instruments%水质检测仪器中溶解氧参数计算与设计

    Institute of Scientific and Technical Information of China (English)

    辛向丽; 郭建

    2015-01-01

    水质检测项目繁多,不同的应用领域所关注的水质项目不同。在多参数水质智能检测仪系统设计中,以溶解氧、酸碱度、钠离子含量、电导率和浊度五种参数作为检测对象。在分析溶解氧参数的检测原理,检测过程和计算方法的基础上,采用极谱型传感器,选用MAX873基准电压源组成激励电压源,由于溶解氧传感器输出的是微弱电流,采用静电计放大器实现电流-电压的转换。%Water quality projects of concern to different ifelds of application. In the design of multi-parameter water intelligent detecting system, with dissolved oxygen, pH, sodium ion content, electrical conductivity and turbidity parameter as testing object. Dissolved oxygen parameters measuring principle and calculation method on the basis of the detection process using MAX873 polarographic sensor, reference voltage excitation voltage, due to the dissolved oxygen sensor is weak current, with an electrometer ampliifers achieve current-voltage conversion.

  18. Influence of Dissolved Oxygen in the Process of Fermentation and its Regulation%微生物发酵过程中溶氧的影响及其调控

    Institute of Scientific and Technical Information of China (English)

    赵宇; 陈忠敏

    2016-01-01

    许多因素会对微生物的整个发酵过程产生影响,其中发酵液的溶氧浓度(Dissolved Oxygen,DO)作为微生物发酵过程中的一个非常重要的发酵参数,它能显著影响微生物的生长以及代谢产物的形成。为了保证发酵过程中适宜的DO,对DO进行控制,笔者分析了影响DO的因素,并提出了溶氧调节的一般方法。%Many factors will affect the whole microbial fermentation process. Fermented liquid of Dissolved Oxygen concentration (DO) is a very important parameter in the microbial fermentation process, it makes a great impact on microbial growth and the formation of metabolic products. In order to ensure an appropriate DO in the fermentation process, to control the DO, the author analyzes the factors that affect the DO and put forward the general method of dissolved oxygen control.

  19. Classification and retrieval on macroinvertebrate image databases.

    Science.gov (United States)

    Kiranyaz, Serkan; Ince, Turker; Pulkkinen, Jenni; Gabbouj, Moncef; Ärje, Johanna; Kärkkäinen, Salme; Tirronen, Ville; Juhola, Martti; Turpeinen, Tuomas; Meissner, Kristian

    2011-07-01

    Aquatic ecosystems are continuously threatened by a growing number of human induced changes. Macroinvertebrate biomonitoring is particularly efficient in pinpointing the cause-effect structure between slow and subtle changes and their detrimental consequences in aquatic ecosystems. The greatest obstacle to implementing efficient biomonitoring is currently the cost-intensive human expert taxonomic identification of samples. While there is evidence that automated recognition techniques can match human taxa identification accuracy at greatly reduced costs, so far the development of automated identification techniques for aquatic organisms has been minimal. In this paper, we focus on advancing classification and data retrieval that are instrumental when processing large macroinvertebrate image datasets. To accomplish this for routine biomonitoring, in this paper we shall investigate the feasibility of automated river macroinvertebrate classification and retrieval with high precision. Besides the state-of-the-art classifiers such as Support Vector Machines (SVMs) and Bayesian Classifiers (BCs), the focus is particularly drawn on feed-forward artificial neural networks (ANNs), namely multilayer perceptrons (MLPs) and radial basis function networks (RBFNs). Since both ANN types have been proclaimed superior by different investigations even for the same benchmark problems, we shall first show that the main reason for this ambiguity lies in the static and rather poor comparison methodologies applied in most earlier works. Especially the most common drawback occurs due to the limited evaluation of the ANN performances over just one or few network architecture(s). Therefore, in this study, an extensive evaluation of each classifier performance over an ANN architecture space is performed. The best classifier among all, which is trained over a dataset of river macroinvertebrate specimens, is then used in the MUVIS framework for the efficient search and retrieval of particular

  20. Role of dissolved oxygen reduction in improvement inhibition performance of ascorbic acid during copper corrosion in 0.50 mol/L sulphuric acid

    Institute of Scientific and Technical Information of China (English)

    Mohammed; A.Amin

    2010-01-01

    The kinetics of dissolved O_2 reduction and hydrogen evolution reactions on copper surface was studied in naturally aerated and air and O_2-saturated 0.50 mol/L H_2SO_4 solutions using polarization measurements combined with the rotating disc electrode (RDE).The Koutecky-Levich plot indicated that the dissolved O_2 reduction at the copper electrode was an apparent four-electron process.A correlation between the presence of dissolved O_2 and the formation of Cu_2O,confirmed from XRD,was discussed. Ascorbi...

  1. Enumeration of non-labile oxygen atoms in dissolved organic matter by use of ¹⁶O/ ¹⁸O exchange and Fourier transform ion-cyclotron resonance mass spectrometry.

    Science.gov (United States)

    Kostyukevich, Yury; Kononikhin, Alexey; Zherebker, Alexander; Popov, Igor; Perminova, Irina; Nikolaev, Eugene

    2014-10-01

    We report a simple approach for enumeration of non-labile oxygen atoms in individual molecules of dissolved organic matter (DOM), using acid-catalyzed (16)O/(18)O exchange and ultrahigh-resolution Fourier-transform ion-cyclotron-resonance mass spectrometry (FTICR-MS). We found that by dissolving DOM in H2 (18)O at 95 °C for 20 days it is possible to replace all oxygen atoms of DOM molecules (excluding oxygen from ether groups) with (18)O. The number of exchanges in each molecule can be determined using high-resolution FTICR. Using the proposed method we identified the number of non-labile oxygen atoms in 231 molecules composing DOM. Also, using a previously developed hydrogen-deuterium (H/D)-exchange approach we identified the number of labile hydrogen atoms in 450 individual molecular formulas. In addition, we observed that several backbone hydrogen atoms can be exchanged for deuterium under acidic conditions. The method can be used for structural and chemical characterization of individual DOM molecules, comparing different DOM samples, and investigation of biological pathways of DOM in the environment.

  2. Temperature, salinity, dissolved oxygen, phosphate, nitrite, pH, alkalinity, bottom depth, and meteorology data collected from Arctic Seas and North Western Pacific by various Soviet Union institutions from 1925-11-16 to 1989-05-18 (NODC Accession 0075099)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature, salinity, dissolved oxygen, phosphate, nitrite, pH, alkalinity, bottom depth, and meteorology data collected from Arctic Seas and North Western Pacific...

  3. Temperature profile, dissolved oxygen, phosphate and other measurements collected using bottle, net, CTD casts from the NEW HORIZON, NOAA Ship DAVID STARR JORDAN, ROGER REVELLE in the North East Pacific Ocean as part of the California Cooperative Fisheries Investigation (CALCOFI) project, from 2000-06-29 to 2004-01-20 (NCEI Accession 0002116)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature, dissolved oxygen, phosphate and other data were collected using water pumps, SIMBAD radiometer, 150 kHz Acoustic Doppler Current Profiler (ADCP),...

  4. Temperature profile, salinity, dissolved oxygen, phosphate and other measurements collected using bottle and CTD casts from the New Horizon and NOAA Ship David Starr Jordan in the North East Pacific Ocean as part of the California Cooperative Fisheries Investigation (CALCOFI) project, from 23 March - 2004-07-28 (NCEI Accession 0002180)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature, salinity, dissolved oxygen, phosphate, conductivity, phytoplankton, and other data were collected using CalBOBL, manta net, pairovet, bottle, and CTD...

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

    Science.gov (United States)

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

    2015-12-01

    The objectives of this study were to determine the dissolved CO2 and O2 concentrations in the purge of vacuum-packaged pork chops over a 60 day storage period, and to elucidate the relationship of dissolved CO2 and O2 to the microbial populations and shelf life. As the populations of spoilage bacteria increased, the dissolved CO2 increased and the dissolved O2 decreased in the purge. Lactic acid bacteria dominated the spoilage microflora, followed by Enterobacteriaceae and Brochothrix thermosphacta. The surface pH decreased to 5.4 due to carbonic acid and lactic acid production before rising to 5.7 due to ammonia production. A mathematical model was developed which estimated microbial populations based on dissolved CO2 concentrations. Scanning electron microscope images were also taken of the packaging film to observe the biofilm development. The SEM images revealed a two-layer biofilm on the packaging film that was the result of the tri-phase growth environment. Copyright © 2015 Elsevier Ltd. All rights reserved.

  6. Application of Neural Network Predictive Control to Dissolved Oxygen Control in Sewage Treatment Process%神经网络预测控制在污水处理溶解氧控制中的应用

    Institute of Scientific and Technical Information of China (English)

    张学阳; 项雷军; 林文辉; 郭新华

    2015-01-01

    针对污水处理过程溶解氧浓度时变设定值难以控制的问题,提出一种溶解氧浓度的神经网络预测控制器设计方法。首先,在活性污泥法污水处理过程通用机理模型基础上,利用系统的输入、输出数据,采用递推学习更新模式,通过三层BP神经网络训练出系统神经网络逼近模型。然后,设计满足出水水质指标的溶解氧约束预测控制器。在考虑溶解氧测量白噪音干扰和进水流量发生阶跃变化情况下,将所设计的控制器用于污水处理溶解氧浓度的时变设定值跟踪控制。仿真结果表明:与传统 PID 控制器相比,神经网络预测控制器能够显著提高溶解氧跟踪控制性能,具有更好的自适应性和抗干扰能力。%In order to solve the difficult problem of controlling the dissolved oxygen (DO)concentration with time var-ying setpoint in sewage treatment process,a neural network predictive controller (NNPC)design method for the dissolved oxygen concentration is proposed in this paper.Firstly,based on the general mechanism model of the activated sludge sewage treatment process,by using the input and output data of the system and the recursive learning update mode,the neural network approximation model of the system is trained through three-layer BP neural network.Then the constrained predictive controller of dissolved oxygen is designed in the condition of satisfying effluent water quality indicators.Consid-ering the white noise interference on the dissolved oxygen measurement and the step changing influent flow,the designed controller is applied to the time varying setpoint tracking control of dissolved oxygen concentration in sewage treatment process.Simulation results show that compared to the conventional PID controller,the neural network predictive control-ler can significantly improve the tracking control performance of dissolved oxygen concentration and has better adaptability and stronger

  7. Computer Control Method of Dissolved Oxygen in Sewage Treatment%污水处理计算机控制系统的设计与实现

    Institute of Scientific and Technical Information of China (English)

    陈荣; 王海瑞

    2012-01-01

    This paper introduces in detail the process flow of wastewater disposal. . And designs the distributive control system in wastewater disposal plant based on 3-tiered architecture (Ethernet, Controller Link, Devicenet) of OMRON PLC. According to control objective of each part and the features of actuator, this paper designs PLC program of each part of wastewater disposal process and emphasizes on studying PID control algorithm of dissolved oxygen in SBR craft. Upon the completion of the PLC control task) we design the monitor pictures based on citect6. 0 which is software development platform. Through the monitor pictures we could monitor realtime parameter and get the realtime information. Monitor pictures includes general flow picture, control pictures of each part, trend pictures, alarm pictures and PID control picture. The whole DCS have been running for one year after production. It has a capacity to treat wastewater up to 12000 m3/ d, and ultimately realized the win-win situation of environmental protection and economic benefits.%对化工厂污水处理的工艺流程给予了详细的介绍,并据此提出了应用OMRON PLC典型的三层网络架构(管理层的以太网(Ethernet)、控制层的控制器网(Controller Link)和设备层的Devieenet网)来构建污水处理厂集散控制系统;根据污水处理过程各个部分的控制目标和执行机构的特点,给出了污水处理各个部分的下位机PLC控制程序流程,进而对下位机控制程序进行了详细的设计;在下位机的设计中,重点研究了污水处理过程中SBR工艺中溶解氧浓度的PID控制算法;设计并开发了基于Citect 6.0组态软件的上位机监控界面,实现了对现场设备运行参数的在线监控和故障报警信息的实时显示;上位机监控界面主要包括系统工艺流程界面,各个部分的控制界面,报警界面,趋势界面和PID控制界面等;整个污水处理计算机控制系统投入持续运行

  8. Influence of Dissolved Oxygen on Treatment Effect of Compound MBR%溶解氧对复合式MBR处理效果的影响

    Institute of Scientific and Technical Information of China (English)

    张小燕; 张铁坚; 刘俊良

    2011-01-01

    [Objective] The study aimed to explore the influence of the dissolved oxygen on the treatment effect of compound MBR. [Method] Under the environmental factors were certain, through the control of different DO concn. , the removal efficiency of chemical COD, TN and TP in the domestic sewage was observed to determine the best DO concn. [ Result] The COD removal efficiency could be rose from 68. 3% for DO at 0.5 mg/L to 97.05% for DO at 1. 5 mg/L and when DO was>1. 5 mg/L, the COD removal efficiency had little change with the rise of DO. The TN removal efficiency could rose from 34. 6% for DO at 0.5 mg/L to 66.58% for DO at 1. 5 mg/L, and when DO was>1. 5 mg/L, the TN removal efficiency was dropped on the contrary; the TP removal efficiency was 64.63% when DO was 0.5 mg/L and the TP removal efficiency was declined slightly with the rise of DO, but when DO was>1. 5 mg/L, the TP removal efficiency was decreased obviously. [ Conclusion] Synthesizing the removal effects of DO on each index, it was judged that, when DO was 1.5 mg/L, the comprehensive removing effects of MBR process on COD, TN, TP could reach the best.%[目的]探讨溶解氧(DO)对复合式MBR处理效果的影响.[方法]在各环境要素一定的情况下,通过控制不同的DO浓度来观察生活污水中的化学COD、TN、TP的去除效果,以此来确定最佳的DO浓度.[结果]COD的去除效率由DO为0.5 ng/L时的68.3%上升至DO为1.5 mg/L时的97.05%,而当DO>1.5 mg/L时,COD的去除效果则随着DO的升高变化不大;TN的去除效率由DO为0.5 mg/L时的34.6%上升至DO为1.5 mg/L时的66.58%,而当DO>1.5 mg/L时,TN的去除效率反而下降:TP的去除效果在DO为0.5 mg/L时是64.63%,随着DO的升高,TP的去除效果略有下降,但当DO>1.5 mg/L时,TP的去除效果明显下降.[结论]综合DO对于各项指标的去除影响可以断定,当DO为1.5 mg,/L时,MBR工艺对于COD、TN、TP的综合去除效果可达到最佳.

  9. Macroinvertebrate and diatom metrics as indicators of water-quality conditions in connected depression wetlands in the Mississippi Alluvial Plain

    Science.gov (United States)

    Justus, Billy; Burge, David; Cobb, Jennifer; Marsico, Travis; Bouldin, Jennifer

    2016-01-01

    Methods for assessing wetland conditions must be established so wetlands can be monitored and ecological services can be protected. We evaluated biological indices compiled from macroinvertebrate and diatom metrics developed primarily for streams to assess their ability to indicate water quality in connected depression wetlands. We collected water-quality and biological samples at 24 connected depressions dominated by water tupelo (Nyssa aquatica) or bald cypress (Taxodium distichum) (water depths = 0.5–1.0 m). Water quality of the least-disturbed connected depressions was characteristic of swamps in the southeastern USA, which tend to have low specific conductance, nutrient concentrations, and pH. We compared 162 macroinvertebrate metrics and 123 diatom metrics with a water-quality disturbance gradient. For most metrics, we evaluated richness, % richness, abundance, and % relative abundance values. Three of the 4 macroinvertebrate metrics that were most beneficial for identifying disturbance in connected depressions decreased along the disturbance gradient even though they normally increase relative to stream disturbance. The negative relationship to disturbance of some taxa (e.g., dipterans, mollusks, and crustaceans) that are considered tolerant in streams suggests that the tolerance scale for some macroinvertebrates can differ markedly between streams and wetlands. Three of the 4 metrics chosen for the diatom index reflected published tolerances or fit the usual perception of metric response to disturbance. Both biological indices may be useful in connected depressions elsewhere in the Mississippi Alluvial Plain Ecoregion and could have application in other wetland types. Given the paradoxical relationship of some macroinvertebrate metrics to dissolved O2 (DO), we suggest that the diatom metrics may be easier to interpret and defend for wetlands with low DO concentrations in least-disturbed conditions.

  10. Analysis of benthic macroinvertebrates and biotic indices to evaluate water quality in rivers impacted by mining activities in northern Chile

    Directory of Open Access Journals (Sweden)

    Alvial I.E.

    2013-02-01

    Full Text Available Catchments in the semiarid regions are especially susceptible to environmental perturbation associated with water scarcity, hydrological variations and overuse by anthropogenic activities. Using multivariate analysis to relate environmental and biological data, and diversity and biotic indices (ChBMWP, ChIBF, we analyzed the macroinvertebrate composition of 12 rivers of the semiarid region of northern Chile. A non-metric multidimensional scaling for macroinvertebrate taxa and a principal component analysis for environmental variables strongly separated upstream sites (e.g. Vacas Heladas and Malo Rivers, which presented low pH and high dissolved metal concentrations, from other sites. Effectively, CCA showed that metals and low pH, associated with the altitudinal gradient, determined the distributional patterns of macroinvertebrates in the Elqui catchment. The causes of these particular conditions could be related to geological processes and human impact. The biotic indices applied to the sampling sites corroborated and reflected these characteristics, with La Laguna and Turbio Rivers showing a diverse macroinvertebrate community and moderate to good water quality, and the Claro River showing favorable conditions for the development of aquatic biota, indicating its better quality relative to other stations. To the middle and low part of the basin, a change in the composition of the community was observed, with species that suggest an impact by an increase in organic matter, due to agricultural activities and urban settlements concentrated in this area. Our results suggest that macroinvertebrate taxa in northern Chile may be exceptional species, adapted to unfavorable geochemical conditions, and emphasize the need for protection of the semiarid basins of the region.

  11. Dissolved oxygen monitroing system of fishpond based on the internet of things%基于物联网的鱼塘溶解氧远程监控系统

    Institute of Scientific and Technical Information of China (English)

    杨世凤; 李洋

    2011-01-01

    Dissolved oxygen is one of the most important factors in the aquaculture environment A dissolved oxygen monitoring and control system is described in this paper which uses ZigBee to build the net, and Lab VIEW is used to control the dissolved oxygen of fisheries in the system, the historical data will be saved in MySQL database, GSM module or Internet is used to send message to remote users in the system, so that remote users are allowed to control the fisheries according to the messages. Experiments show that the electricity and artificial cost could be reduced effectively by using this system.%溶解氧是鱼塘水质环境中1项至关重要的指标.给出了1套基于ZigBee的溶解氧无线检测与控制系统,该系统上位机使用LabVIEW虚拟仪器系统控制,并将历史数据保存入MySQL数据库.该系统还使用GSM模块与用户远程通信,使用户可以远程获取鱼塘信息并有效地控制鱼塘环境,用户也可以通过网页浏览家中服务器上的鱼塘信息.实验表明该系统有效地减少了鱼塘用电与人工的开销.

  12. Effectiveness of timber harvesting BMPs: monitoring spatial and temporal dynamics of dissolved oxygen, nitrogen, and phosphorus in a low-gradient watershed, Louisiana

    Science.gov (United States)

    Abram DaSilva; Y. Jun Xu; George Ice; John Beebe; Richard Stich

    2012-01-01

    To test effectiveness of Louisiana’s voluntary best management practices (BMPs) at preventing water quality degradation from timber harvesting activities, a study with BACI design was conducted from 2006 through 2010 in the Flat Creek Watershed, north-central Louisiana. Water samples for nutrient analyses and measurements of stream flow and of in-stream dissolved...

  13. 基于K-means聚类和ELM神经网络的养殖水质溶解氧预测%Dissolved oxygen prediction in water based onK-means clustering and ELM neural network for aquaculture

    Institute of Scientific and Technical Information of China (English)

    宦娟; 刘星桥

    2016-01-01

    为解决养殖水质溶解氧预测传统方法引入不良样本、精度低等问题,该文以2014、2015年江苏常州养殖基地水质和气象数据为基础,提出了一种基于K-means聚类和ELM神经网络(extreme learning machine,ELM)的溶解氧预测模型。采用皮尔森相关系数法确定环境因素与溶解氧的相关系数,自定义相似日的统计量-相似度,通过K-means聚类方法将历史日样本划分为若干类,然后分类识别获得与预测日最相似的一类历史日样本集,将其与预测日的实测环境因素作为预测模型的输入样本建立ELM神经网络溶解氧预测模型。试验结果表明,该模型均具有较快的计算速度和较高的预测精度,在常规天气下,平均绝对百分误差和均方根误差分别达到1.4%、10.8%;在突变天气下,平均绝对百分误差和均方根误差分别达到2.6%和11.6%,有利于水产养殖水质精准调控。%Dissolved oxygen plays a vital role in water management as it is an important factor that determines the growth status of the fish. Either inadequate or excessive level of dissolved oxygen will be harmful to the survivability of the fish in their respective habitats. The accurate analysis of the data collected from the aquaculture ponds and the prediction for the anticipated level of dissolved oxygen are helpful for both water quality management and aquaculture production. Current studies reveal and understand the complex features of the water quality process mainly from the perspective of mathematical statistics. However, they cannot analyze the effects of changes in the environment on water quality, and cannot do well in dissolved oxygen prediction under the changing environment either. This paper proposed a new strategy to predict dissolved oxygen based on K-means clustering and ELM (extreme learning machine) neural networks. As the curves of similar days showed high correlation of dissolved oxygen, the

  14. Influence of seasonal variation on bioassessment of streams using macroinvertebrates

    NARCIS (Netherlands)

    Sporka, F.; Vlek, H.E.; Bulánková, E.; Krno, I.

    2006-01-01

    The EU Water Framework Directive requires assessment of the ecological quality of running waters using macroinvertebrates. One of the problems of obtaining representative samples of organisms from streams is the choice of sampling date, as the scores obtained from macroinvertebrate indices vary natu

  15. Suppression of aqueous corrosion of La(Fe{sub 0.88}Si{sub 0.12}){sub 13} by reducing dissolved oxygen concentration for high-performance magnetic refrigeration

    Energy Technology Data Exchange (ETDEWEB)

    Fujieda, S., E-mail: fujieda@tagen.tohoku.ac.jp; Fukamichi, K.; Suzuki, S.

    2014-07-05

    Highlights: • The aqueous corrosion of La(Fe{sub 0.88}Si{sub 0.12}){sub 13} and its suppression were investigated. • The lattice expansion after immersion was caused by the hydrogen absorption. • The itinerant-electron metamagnetic transition became indistinct after immersion. • The aqueous corrosion was suppressed by reducing the dissolved oxygen concentration. - Abstract: The itinerant-electron metamagnetic transition of La(Fe{sub 0.88}Si{sub 0.12}){sub 13} becomes indistinct after immersion in distilled-water containing about 8 ppm of the dissolved oxygen (DO) concentration because of aqueous corrosion. However, the aqueous corrosion of La(Fe{sub 0.88}Si{sub 0.12}){sub 13} is significantly suppressed by reducing the DO concentration. Thus, isothermal magnetic entropy change after immersion for 30 days in deaerated distilled-water with a DO concentration less than 0.1 ppm is larger than that after immersion for 5 days in distilled-water containing about 8 ppm of the DO concentration. Consequently, the reduction of the DO concentration is effective for preservation of the excellent magnetocaloric effects of La(Fe{sub 0.88}Si{sub 0.12}){sub 13} in an aqueous solution, which is a promising heat transfer fluid of room-temperature magnetic refrigeration.

  16. Benthic macroinvertebrates in Italian rice fields

    Directory of Open Access Journals (Sweden)

    Daniela Lupi

    2013-02-01

    Full Text Available Rice fields can be considered man-managed temporary wetlands. Five rice fields handled with different management strategies, their adjacent channels, and a spring were analysed by their benthic macroinvertebrate community to i evaluate the role of rice agroe- cosystem in biodiversity conservation; ii find indicator species which can be used to compare the ecological status of natural wetlands with rice agroecosystems; and iii find the influence of environmental variables on biodiversity. Different methods of data analysis with increasing degree of complexity – from diversity index up to sophisticated multivariate analysis – were used. The investigation provided a picture of benthic macroinvertebrates inhabiting rice agroecosystems where 173 taxa were identified, 89 of which detected in rice paddies. Among them, 4 phyla (Mollusca, Annelida, Nematomorpha, and Arthropoda, 8 classes (Bivalvia, Gastropoda, Oligochaeta, Hirudinea, Gordioida, Insecta, Branchiopoda, and Malacostraca, 24 orders, 68 families, 127 genera and 159 species have been found. Ten threatened and 3 invasive species were detected in the habitats examined. The information obtained by the different methods of data analysis allowed a more comprehensive view on the value of the components of rice agroecosystems. Data analyses highlighted significant differences between habitats (feeding channel and rice field, with higher diversity observed in channels, and emphasised the role of the water chemical-physical parameters. The period of water permanence in rice fields resulted to be only one of the factors influencing the community of benthic macroinvertebrates. The presence of rare/endangered species allowed characterising some stations, but it was less informative about management strategies in rice paddies because most of these species were absent in rice fields.

  17. Aquatic macroinvertebrates of the Jablanica river, Serbia

    Directory of Open Access Journals (Sweden)

    Stefanović Katarina S.

    2009-01-01

    Full Text Available Research on the community of aquatic macroinvertebrates was carried out during 2005 and 2006 at four sampling sites along the Jablanica River, a right-hand tributary of the Kolubara River. Fifty-seven taxa were recorded in the course of the investigation. The most diverse group was Ephemeroptera, followed by Trichoptera and Plecoptera. Members of the Rhitrogena semicolorata group were the most abundant. Our results could be the basis for evaluation of the influence of damming of the Jablanica River on the status of its water and can serve as a model for studying the influ­ence of hydromorphological degradation of aquatic ecosystems.

  18. 溶解氧突变指数对活性污泥重金属中毒的预警%Early Warning of Heavy Metal Poisoning of Activated Sludge Indicated with Dissolved Oxygen Mutation Index

    Institute of Scientific and Technical Information of China (English)

    陈亚松; 杜郁; 杨广文; 赵文玉; 陈振国

    2014-01-01

    以溶解氧(DO)突变为活性污泥中毒的预警指标,研究Cu2+、Cr6+、Pb2+、As5+4种重金属对活性污泥的毒性,并对预警活性污泥重金属中毒的测试参数进行优化。结果表明在相同的反应条件和重金属浓度(15 mg/L)下,4种重金属抑制活性污泥活性导致DO突变量分别为0.87、0.6、0.4和0.75 mg/L,其顺序为Cu2+> As5+> Cr6+> Pb2+,活性污泥对重金属铜中毒更加敏感。当As5+和Cr6+浓度由3 mg/L提高至15 mg/L时,活性污泥的DO突变量分别由0.32和0.27 mg/L上升至0.75和0.53 mg/L,表明随进水中As5+、Cr6+浓度增加,对活性污泥抑制性越强,存在剂量效应关系,因此溶解氧突变可作为活性污泥重金属离子中毒的判别指标,快速预警污水处理厂进水重金属引发活性污泥中毒与否,为污水处理厂稳定运行提供技术支持。%The early warning of activated sludge poisoned by heavy metals as Cu2+,Cr6+,Pb2+and As5+ was studied with dissolved oxygen mutation index. The parameters of early warning of activated sludge poisoning were optimized. With a certain condition and common dosage of heavy metals (15 mg/L),the dissolved oxygen mutation by these heavy metals are 0. 87,0. 6,0. 4 and 0. 75 mg/L,which indicates the biological inhibition order is Cu2+ >As5+ >Cr6+ >Pb2+. When concentrations of As5+and Cr6+ increase from 3 mg/L to 15 mg/L,the dissolved oxygen mutations increase from 0. 32,0. 27 mg/L up to 0. 75 and 0. 53 mg/L,respectively. With a rising dosage of heavy metals,the activated sludge ’s poison measured by dissolved oxygen mutation index is enhanced. Thus,the dissolved oxygen mutation index can be used as early warning of the activated sludge poisoned by heavy metals in wastewater treatment plant.

  19. Comparison of fish and macroinvertebrates as bioindicators of Neotropical streams.

    Science.gov (United States)

    Ruaro, Renata; Gubiani, Éder André; Cunico, Almir Manoel; Moretto, Yara; Piana, Pitágoras Augusto

    2016-01-01

    The biomonitoring of aquatic ecosystems in developing countries faces several limitations, especially related to gathering resources. The present study aimed at comparing the responses of fish and benthic macroinvertebrates to environmental change, to identify which group best indicates the differences between reference and impacted streams in southern Brazil. We determined reference and impacted sites based on physical and chemical variables of the water. For the analysis and comparison of biological responses, we calculated 22 metrics and submitted them to a discriminant analysis. We selected from this analysis only six metrics, which showed that the two studied assemblages respond differently to environmental change. A larger number of metrics were selected for macroinvertebrates than for fish in the separate analysis. The metrics selected for macroinvertebrates in the pooled analysis (i.e., fish and macroinvertebrates together) were different from those selected in the separate analysis for macroinvertebrates alone. However, the metrics selected for fish in the pooled analysis were the same selected in the separate analysis for fish alone. The macroinvertebrate assemblage was more effective for distinguishing reference from impacted sites. We suggest the use of macroinvertebrates as bioindicators of Neotropical streams, especially in situations in which time and money are short.

  20. Bioassessment of Choghakhor Wetland using Benthic Macroinvertebrates

    Directory of Open Access Journals (Sweden)

    P. Fathi

    2016-05-01

    Full Text Available In present study, besides investigating benthic communities and their demographics in Choghakhor wetland, the water quality has been evaluated and classified. Then, 10 stations were selected and sampling of benthos was done every 45 days since April 2010 to March 2011, with 3 replications at each station. Samples were obtained by Ekman grab Sampler (surface 400 cm2. The collected samples were separated and fixed by formalin (4%. The Macroinvertebrates samples were identified and counted in laboratory. Generally 25 families of benthic macroinvertebrates belonging to 5 classes and 12 orders were identified. The results were calculated as community measures, including total richness, Shannon - Wiener diversity index and Hilsenhoff Biological index at family level. The results obtained from temporal and spatial changes of data (Statgeraphics software and water qualitative classification using Shannon diversity index conformed to biological Hilsenhoff index. And finally, water quality of wetland was assessed to be polluted in average to high level. According to this study findings, it seems that, these indicators could be used as useful tools for evaluating water supplies quality.

  1. Macroinvertebrate diversity in the karst Jadro River (Croatia

    Directory of Open Access Journals (Sweden)

    Rađa Biljana

    2008-01-01

    Full Text Available This paper presents the results of 10 years of investigation of the aquatic macroinvertebrate fauna along the karst Jadro River. The Jadro is a typical karst river. Benthic macroinvertebrates were collected along the river at 15 sites by standard methods of sampling, in addition to which several physicochemical parameters were also determined. Based on qualitative and quantitative composition of the macroinvertebrate fauna, correspondence analysis divided the river course into three sections: upstream, midcourse, and downstream. Forty-three taxa were recorded. Results of saprobiological analysis based on macrozoobenthos indicate that water of the Jadro River belongs to quality classes I and II.

  2. 溶氧对Candida glycerinogenes产甘油发酵代谢流分布的影响%Effect of dissolved oxygen on metabolic flux distribution during glycerol fermentation by Candida glycerinogenes

    Institute of Scientific and Technical Information of China (English)

    焦策; 诸葛斌; 方慧英; 诸葛健

    2012-01-01

    The glycerol production by fermentation in flasks by Candida glycerinogenes was studied. Dissolved oxygen (DO) was one of the most important factors in the cultivation of the strain by influencing cell growth and metabolites generated. Based on this result, batch fermentation of glycerol under diverse DO levels in a 5 L stirred fermentor was investigated. The metabolic flux analysis explained the phenomenon that sugar consumption was fast and glycerol synthesis was relatively less under low dissolved oxygen levels, mainly due to generated ethanol. Metabolic flux analysis also showed that HMP pathway played an important role in glycerol synthesis. Analysis of carbon metabolization and energy metabolization (oxidative phosphorylation and substrate level phosphorylation) of C. Glycerinogenes in the process of glycerol fermentation showed that a high level of ATP synthesis at high dissolved oxygen levels to a certain degree inhibited substrate level phosphorylation so that more carbon flowed to glycerol synthesis. The intracellular redox balance (NADH/NAD+ ratio) reflected the competition between glycerolproduction and ethanol synthesis.%分析了耐高渗高产甘油工业菌株产甘油假丝酵母(Candida glycerinogenes)的摇瓶发酵过程,发现溶氧水平是影响C.glycerinogenes生长、代谢产物生成的重要因素.在此基础上,以5L发酵罐研究了不同恒溶氧水平甘油的合成过程,通过代谢流分析表明,低溶氧环境下乙醇碳流量增加,导致糖耗快而甘油合成相对较少;碳流分布表明HMP途径在甘油过量合成中起着重要的作用.分析C.glycerinogenes发酵过程中能量代谢和物质代谢(氧化磷酸化和底物水平磷酸化)的变化发现高溶氧环境下ATP合成水平高,一定程度抑制底物水平磷酸化从而使碳流更多地流向了甘油合成;C.glycerinogenes胞内氧化还原平衡(NADH/NAD+比率)的研究进一步解释了产甘油假丝酵母中甘油合成和乙醇生成的竞争关系.

  3. Advance in Measurement and Wireless Monitoring Mode of Dissolved Oxygen of Aquaculture Water%养殖水体溶氧量测定方法及其无线监测模式的研究进展

    Institute of Scientific and Technical Information of China (English)

    郭孟彩; 王宏坡; 李唯民; 张达娟

    2015-01-01

    The research progress of the principles, methods and the application scopes of iodimetry method, spectrophotometry method, oxygen electrode method and fiber optical oxygen sensor method were mainly discussed. On the basis of above, the wireless monitoring modes of dissolved oxygen of aquaculture water, such as ZigBee system mode, GSM system mode and WiFi system mode were introduced in order to provide references for grasping and applying the appropriate monitoring technologies.%综述了碘量法、分光光度法、氧电极法和光纤氧电极传感器法等养殖水体溶氧量测定法的原理、方法、应用及适用范围。在此基础上,比较了基于ZigBee无线通信系统模式、GSM系统模式以及WiFi系统模式3种养殖水体溶解氧无线监测模式的研究进展及应用实例,以期为掌握和应用相应的监测技术提供参考。

  4. Effects of organic pollution and physical stress on benthic macroinvertebrate communities from two intermittently closed and open coastal lagoons (ICOLLs)

    Science.gov (United States)

    Coelho, Susana; Pérez-Ruzafa, Angel; Gamito, Sofia

    2015-12-01

    Benthic macroinvertebrate communities and environmental conditions were studied in two intermittently closed and open coastal lakes and lagoons (ICOLLs), located in southern Algarve (Foz do Almargem e Salgados), with the purpose of evaluating the effects of organic pollution, originated mainly from wastewater discharges, and the physical stress caused by the irregular opening of the lagoons. Most of the year, lagoons were isolated from the sea, receiving the freshwater inputs from small rivers and in Salgados, also from the effluents of a wastewater plant. According to environmental and biotic conditions, Foz do Almargem presented a greater marine influence and a lower trophic state (mesotrophic) than Salgados (hypereutrophic). Benthic macroinvertebrate communities in the lagoons were distinct, just as their relations with environmental parameters. Mollusca were the most abundant macroinvertebrates in Foz do Almargem, while Insecta, Oligochaeta and Crustacea were more relevant in Salgados. Corophium multisetosum occurred exclusively in Salgados stations and, just as Chironomus sp., other Insecta and Oligochaeta, densities were positively related to total phosphorus, clay content and chlorophyll a concentration in the sediment, chlorophyll a concentration in water and with total dissolved inorganic nitrogen. Abra segmentum, Cerastoderma glaucum, Peringia ulvae and Ecrobia ventrosa occurred only in Foz do Almargem, with lower values of the above mentioned parameters. Both lagoons were dominated by deposit feeders and taxa tolerant to environmental stress, although in Salgados there was a greater occurrence of opportunistic taxa associated to pronounced unbalanced situations, due to excess organic matter enrichment.

  5. Explosives Dissolved from Unexploded Ordnance

    Science.gov (United States)

    2011-10-01

    moisture content) also result in higher corrosion rates especially if the moisture has high dissolved oxygen content ( Manahan 1994). Corrosion of metal is...R. 1993. Handbook of hydrology. New York: McGraw-Hill, Inc. Manahan , S. 1994. Environmental Chemistry. Boca Raton, FL: Lewis Publishers. McCormick

  6. Macro-invertebrate and Avian Species Survey : Biological Summary Report

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This was a survey effort to determine species diversity and density of macro-invertebrates and avian species inhabiting playa systems located in SW regions of Baca...

  7. Foote Brook Macroinvertebrate Biomonitoring-Phase I in Johnson, Vermont

    Data.gov (United States)

    Vermont Center for Geographic Information — The Foote Brook Biomonitoring Project, Phase I geospatial dataset consists of data from the biomonitoring of benthic macroinvertebrates at three sites located along...

  8. Long-term variations in benthic macroinvertebrate assemblages off Bombay, India

    Digital Repository Service at National Institute of Oceanography (India)

    Parulekar, A.H.; Ansari, Z.A.; Harkantra, S.N.; Rodrigues, C.L.

    composition, with total depletion at many sites, was observed. Of the environmental parameters, dissolved oxygen concentration in the near-bottom water and organic matter composition of bottom deposits exhibited major changes, with deleterious effects...

  9. Effect of carbon source, C/N ratio, nitrate and dissolved oxygen concentration on nitrite and ammonium production from denitrification process by Pseudomonas stutzeri D6.

    Science.gov (United States)

    Yang, Xinping; Wang, Shimei; Zhou, Lixiang

    2012-01-01

    Pseudomonas stutzeri D6, selectively isolated from activated sludge was used to study NO(2)(-) and NH(4)(+) production from denitrification processes. Changes in carbon type, C/N ratio and oxygen concentration significantly influenced the magnitude of NO(2)(-) and NH(4)(+) accumulation through denitrification. D6 showed a preference for citrate and acetate, which led to the largest quantity of nitrate reduced and which were exhausted most rapidly, with minimal intermediate products accumulation. It is found that at higher initial organic carbon concentration or for directly metabolic carbon type more complete denitrification could be obtained as a result of increase of the oxygen consumption rate by substrate stimulation. The higher the oxygen concentration in the culture was, the higher the intermediate products concentration became. The experiment showed that NO(2)(-) and NH(4)(+) production was only slightly influenced by nitrate concentration. Biological nitrogen removal systems should be optimized to promote complete denitrification to minimize NO(2)(-) and NH(4)(+) accumulation. Copyright © 2011 Elsevier Ltd. All rights reserved.

  10. Hydrologic controls on basin-scale distribution of benthic macroinvertebrates

    Science.gov (United States)

    Bertuzzo, E.; Ceola, S.; Singer, G. A.; Battin, T. J.; Montanari, A.; Rinaldo, A.

    2013-12-01

    The presentation deals with the role of streamflow variability on basin-scale distributions of benthic macroinvertebrates. Specifically, we present a probabilistic analysis of the impacts of the variability along the river network of relevant hydraulic variables on the density of benthic macroinvertebrate species. The relevance of this work is based on the implications of the predictability of macroinvertebrate patterns within a catchment on fluvial ecosystem health, being macroinvertebrates commonly used as sensitive indicators, and on the effects of anthropogenic activity. The analytical tools presented here outline a novel procedure of general nature aiming at a spatially-explicit quantitative assessment of how near-bed flow variability affects benthic macroinvertebrate abundance. Moving from the analytical characterization of the at-a-site probability distribution functions (pdfs) of streamflow and bottom shear stress, a spatial extension to a whole river network is performed aiming at the definition of spatial maps of streamflow and bottom shear stress. Then, bottom shear stress pdf, coupled with habitat suitability curves (e.g., empirical relations between species density and bottom shear stress) derived from field studies are used to produce maps of macroinvertebrate suitability to shear stress conditions. Thus, moving from measured hydrologic conditions, possible effects of river streamflow alterations on macroinvertebrate densities may be fairly assessed. We apply this framework to an Austrian river network, used as benchmark for the analysis, for which rainfall and streamflow time-series and river network hydraulic properties and macroinvertebrate density data are available. A comparison between observed vs "modeled" species' density in three locations along the examined river network is also presented. Although the proposed approach focuses on a single controlling factor, it shows important implications with water resources management and fluvial

  11. 改进递归最小二乘RBF神经网络溶解氧预测%Dissolved oxygen prediction based on improved recursive least square RBF neural network

    Institute of Scientific and Technical Information of China (English)

    袁红春; 潘金晶

    2016-01-01

    In order to improve accuracy of dissolved oxygen prediction,radial basis function( RBF)neural network based on improved recursive least square algorithm is applied to predict the dissolved oxygen. Using K means clustering algorithm to choose the center of hidden layer units and improved recursive least square algorithm is used to optimize the weights of hidden layer to output layer of RBF neural network. Simulation results show that the proposed method has good nonlinear fitting ability and its prediction precision is higher than RBF neural network and RBF neural network based on recusive least square algorithm.%为提高溶解氧预测的准确性,将基于改进型递归最小二乘算法优化的径向基函数( RBF)神经网络方法应用于溶解氧预测。利用K均值聚类算法进行隐层单元中心选择;利用改进型递归最小二乘算法优化RBF神经网络隐含层到输出层的权值。仿真结果表明:该方法对溶解氧的预测具有较好的非线性拟合能力,预测精度优于RBF神经网络和递归最小二乘算法优化的RBF神经网络。

  12. Does water level affect benthic macro-invertebrates of a marginal lake in a tropical river-reservoir transition zone?

    Science.gov (United States)

    Zerlin, R A; Henry, R

    2014-05-01

    Benthic macro-invertebrates are important components of freshwater ecosystems which are involved in ecological processes such as energy transfer between detritus and consumers and organic matter recycling. The aim of this work was to investigate the variation in organism richness, diversity and density of benthic fauna during the annual cycle in Camargo Lake, a lake marginal to Paranapanema River, southeast Brazil. The correlation of environmental factors with community attributes of the macro-benthic fauna was assessed. Since Camargo Lake is connected to the river, we tested the hypothesis that water level variation is the main regulating factor of environmental variables and of the composition and abundance of benthic macro-invertebrates. The results indicated that lake depth varied with rainfall, being the highest at the end of the rising water period and the lowest at the beginning of this period. The sediment granulometry was more heterogeneous at the bottom of the lake by the end of the high water period. The benthic macro-invertebrate fauna was composed by 15 taxa. The Diptera order was represented by seven taxa and had greater richness in relation to other taxa. This group was responsible for 60% of the total abundance of organisms, followed by Ephemeroptera (22%) and Anellida (16%). Significant differences were observed over time in total richness and, in density of Narapa bonettoi, Chaoborus, Ablabesmyia gr. annulata, Chironomus gigas, Larsia fittkau, and Procladius sp. 2. Total taxa richness correlated negatively with water pH, transparency, conductivity, and bottom water oxygen. Higher positive correlations were found between the densities of some taxa and bottom water oxygen, conductivity and very fine sand, silt + clay of sediment, while negative correlations were recorded with organic matter, and fine, medium and coarse sand, bottom water temperature, mean temperature and rainfall. The significant temporal difference in water level was associated

  13. Studied on The Relationship of Dissolved Oxygen and Aeration Tylosin Fermentation%泰乐菌素发酵中通气量与DO的分析控制

    Institute of Scientific and Technical Information of China (English)

    王成迎; 石永芝

    2005-01-01

    研究了泰乐菌素发酵生产过程中通气量(aeration)与溶解氧(dissoled oxygen)的关系,在实验中探明了泰乐菌素发酵中溶解氧的变化规律.得出了泰乐菌素发酵中通气量的控制参数并应用于生产实际,在发酵放罐单位相当的情况下,大大降低了空气消耗,有效地控制了发酵成本.

  14. Efficient simultaneous partial nitrification, anammox and denitrification (SNAD) system equipped with a real-time dissolved oxygen (DO) intelligent control system and microbial community shifts of different substrate concentrations.

    Science.gov (United States)

    Wen, Xin; Gong, Benzhou; Zhou, Jian; He, Qiang; Qing, Xiaoxia

    2017-08-01

    Simultaneous partial nitrification, anammox and denitrification (SNAD) process was studied in a sequencing batch biofilm reactor (SBBR) fed with synthetic wastewater in a range of 2200 mgN/L ∼ 50 mgN/L. Important was an external real-time precision dissolved oxygen (DO) intelligent control system that consisted of feed forward control system and feedback control system. This DO control system permitted close control of oxygen supply according to influent concentration, effluent quality and other environmental factors in the reactor. In this study the operation was divided into six phases according to influent nitrogen applied. SNAD system was successfully set up after adding COD into a CANON system. And the presence of COD enabled the survival of denitrifiers, and made Thauera and Pseudomonas predominant as functional denitrifiers in this system. Denaturing gradient gel electrophoresis (DGGE), fluorescence in situ hybridization (FISH) and 16S rRNA amplicon pyrosequencing were used to analyze the microbial variations of different substrate concentrations. Results indicated that the relative population of ammonia oxidizing bacteria (AOB) members decreased when influent ammonia concentration decreased from 2200 mg/L to 50 mg/L, while no dramatic drop of the percent of anammox bacteria was seen. And Nitrosomonas europaea was the predominant AOB in SNAD system treating sewage, while Candidatus Brocadia was the dominant anammox bacteria. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Benthos response following petroleum exploration in the southern Caspian Sea: Relating effects of nonaqueous drilling fluid, water depth, and dissolved oxygen.

    Science.gov (United States)

    Tait, R D; Maxon, C L; Parr, T D; Newton, F C

    2016-09-15

    The effects of linear alpha olefin (LAO) nonaqueous drilling fluid on benthic macrofauna were assessed over a six year period at a southern Caspian Sea petroleum exploration site. A wide-ranging, pre-drilling survey identified a relatively diverse shelf-depth macrofauna numerically dominated by amphipods, cumaceans, and gastropods that transitioned to a less diverse assemblage dominated by hypoxia-tolerant annelid worms and motile ostracods with increasing depth. After drilling, a similar transition in macrofauna assemblage was observed with increasing concentration of LAO proximate to the shelf-depth well site. Post-drilling results were consistent with a hypothesis of hypoxia from microbial degradation of LAO, supported by the presence of bacterial mats and lack of oxygen penetration in surface sediment. Chemical and biological recoveries at ≥200m distance from the well site were evident 33months after drilling ceased. Our findings show the importance of monitoring recovery over time and understanding macrofauna community structure prior to drilling.

  16. Ammonia, silicate, phosphate, dissolved oxygen, and other variables collected from profile and discrete sample observations using CTD, nutrient autoanalyzer, and other instruments from NOAA Ship Delaware II, NOAA Ship Gordon Gunter, NOAA Ship Henry B. Bigelow, NOAA Ship Okeanos Explorer, and NOAA Ship Pisces in the Gulf of Maine, Georges Bank, and Mid-Atlantic Bight from 2009-11-03 to 2014-11-18 (NCEI Accession 0127524)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains nutrient concentrations, temperature, salinity, density and dissolved oxygen values measured by CTD profiles on the U.S. Northeast Continental...

  17. Guam Community Coral Reef Monitoring Program, Macroinvertebrate Training Surveys in Guam in 2012

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Guam community members gathered macroinvertebrate within a 25-meter x 2-meter belt transect. Members identified macroinvertebrates to species (when possible),...

  18. Guam Community Coral Reef Monitoring Program, Macroinvertebrate Surveys in Guam in 2013

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Guam community members gathered macroinvertebrate within a 25-meter x 2-meter belt transect. Members identified macroinvertebrates to species (when possible),...

  19. Roles of singlet oxygen and dissolved organic matter in self-sensitized photo-oxidation of antibiotic norfloxacin under sunlight irradiation.

    Science.gov (United States)

    Niu, Xi-Zhi; Busetti, Francesco; Langsa, Markus; Croué, Jean-Philippe

    2016-12-01

    Many fluoroquinolone (FLQ) antibiotics undergo rapid photodegradation in sunlit waters and form multifaceted photo-products. The high photodegradation rate is primarily ascribed to their photosensitizing properties. Though widely studied, the photo-reaction pathways are not completely revealed; photo-products mediated by different reactive oxygen species are not identified. In our study, photo-degradation of fluoroquinolone norfloxacin was investigated. A rapid degradation in buffered water was observed with a first-order rate constant of 2.45/hr and a quantum yield of 0.039. After light screening correction, selected DOMs (5 mg C/L) slightly enhanced the photodegradation rate with the exception of Suwannee river hydrophobic organic matter (SR-HPO). Three major photo-products were identified using high resolution mass spectrometry (HRMS). With (1)O2 dark formation and competitor experiments, norfloxacin self-sensitized (1)O2 was found to oxidize norfloxacin by inducing its piperazine chain cleavage. DOMs exhibited a dual role by inhibiting the (1)O2-mediated reaction while enhancing the heterolytic defluorination pathway. DOMs were proposed to enhance heterolytic defluorination by donating electron to triplet state FLQ, this proposal was supported with specific UV absorbance (SUVA) as an indicator for the abundance of π bonds. Fluoride formation indicated a 79% elimination ratio of fluorine, an important functional group for antimicrobial activity. This work provides important new insights into the photochemical fate of fluoroquinolone antibiotics in natural water. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. DEGRADATION OF DISSOLVED ORGANIC MATTER FROM DEAD PHYTOPLANKTON OFF THE CHANGJIANG RIVER ESTUARY AND THE RESULTING DISSOLVED OXYGEN CONSUMPTION%长江口外浮游植物死亡释放溶解有机质的降解及其溶氧消耗

    Institute of Scientific and Technical Information of China (English)

    高小丰; 吴莹; 朱卓毅

    2015-01-01

    浮游植物光合作用产生的溶解有机质(dissolved organic matter,DOM)是海洋中溶解有机质的重要来源,浮游植物死亡后释放的新鲜溶解有机质活性高、数量大、生物可利用性高,其降解过程中对溶解氧(dissolved oxygen,DO)的消耗显著.但到目前为止,对此类溶解有机质的降解过程以及其耗氧情况还鲜有研究.本文基于2013年8月东海航次,对浮游植物(硅藻为主)死亡后释放的新鲜有机质进行人工受控培养,研究其降解过程及对DO的消耗,并评估该降解过程对低氧现象形成的贡献.研究发现:培养体系中溶解有机碳(dissolved organic carbon,DOC)和DO浓度皆随时间呈指数下降,总溶解态碳水化合物(total carbohydrate,TCHO)也出现明显降解;体系的初始DOC浓度越高,降解速率常数k(DOC)、 k(DO)越大,k(DOC)受DOC浓度、活性以及DO浓度的影响;培养过程中细菌丰度明显增加,添加HgCl2的对比实验表明细菌在降解过程中起到重要作用.本文的研究结果表明,浮游植物死亡后释放的溶解有机质的快速降解及其对溶解氧的消耗,对长江口低氧环境的促成具有重要意义.

  1. Method to Estimate the Dissolved Air Content in Hydraulic Fluid

    Science.gov (United States)

    Hauser, Daniel M.

    2011-01-01

    In order to verify the air content in hydraulic fluid, an instrument was needed to measure the dissolved air content before the fluid was loaded into the system. The instrument also needed to measure the dissolved air content in situ and in real time during the de-aeration process. The current methods used to measure the dissolved air content require the fluid to be drawn from the hydraulic system, and additional offline laboratory processing time is involved. During laboratory processing, there is a potential for contamination to occur, especially when subsaturated fluid is to be analyzed. A new method measures the amount of dissolved air in hydraulic fluid through the use of a dissolved oxygen meter. The device measures the dissolved air content through an in situ, real-time process that requires no additional offline laboratory processing time. The method utilizes an instrument that measures the partial pressure of oxygen in the hydraulic fluid. By using a standardized calculation procedure that relates the oxygen partial pressure to the volume of dissolved air in solution, the dissolved air content is estimated. The technique employs luminescent quenching technology to determine the partial pressure of oxygen in the hydraulic fluid. An estimated Henry s law coefficient for oxygen and nitrogen in hydraulic fluid is calculated using a standard method to estimate the solubility of gases in lubricants. The amount of dissolved oxygen in the hydraulic fluid is estimated using the Henry s solubility coefficient and the measured partial pressure of oxygen in solution. The amount of dissolved nitrogen that is in solution is estimated by assuming that the ratio of dissolved nitrogen to dissolved oxygen is equal to the ratio of the gas solubility of nitrogen to oxygen at atmospheric pressure and temperature. The technique was performed at atmospheric pressure and room temperature. The technique could be theoretically carried out at higher pressures and elevated

  2. POP bioaccumulation in macroinvertebrates of alpine freshwater systems.

    Science.gov (United States)

    Bizzotto, E C; Villa, S; Vighi, M

    2009-12-01

    This study serves to investigate the uptake of POPs in the different trophic levels (scrapers, collectors, predators, shredders) of macroinvertebrate communities sampled from a glacial and a non-glacial stream in the Italian Alps. The presented results show that the contaminant concentrations in glacial communities are generally higher compared to those from non-glacial catchments, highlighting the importance of glaciers as temporary sinks of atmospherically transported pollutants. Moreover, the data also suggests that in mountain systems snow plays an important role in influencing macroinvertebrate contamination. The main chemical uptake process to the macroinvertebrates is considered to be bioconcentration from water, as similar contaminant profiles were observed between the different trophic levels. The role of biomagnification/bioaccumulation is thought to be absent or negligible. The enrichment of chemicals observed in the predators is likely to be related to their greater lipid content compared to that of other feeding groups.

  3. Fish stomach contents in benthic macroinvertebrate assemblage assessments

    Directory of Open Access Journals (Sweden)

    TH. Tupinambás

    Full Text Available The choice of sampling gears to assess benthic macroinvertebrate communities depends on environmental characteristics, study objectives, and cost effectiveness. Because of the high foraging capacity and diverse habitats and behaviors of benthophagous fishes, their stomach contents may offer a useful sampling tool in studies of benthic macroinvertebrates, especially in large, deep, fast rivers that are difficult to sample with traditional sediment sampling gear. Our objective was to compare the benthic macroinvertebrate communities sampled from sediments with those sampled from fish stomachs. We collected benthic macroinvertebrates and fish from three different habitat types (backwater, beach, riffle in the wet season, drying season, and dry season along a single reach of the Grande River (Paraná River Basin, southeast Brazil. We sampled sediments through use of a Petersen dredge (total of 216 grabs and used gill nets to sample fish (total of 36 samples. We analyzed the stomach contents of three commonly occurring benthophagous fish species (Eigenmannia virescens, Iheringichthys labrosus, Leporinus amblyrhynchus. Chironomids dominated in both sampling methods. Macroinvertebrate taxonomic composition and abundances from fish stomachs differed from those from sediment samples, but less so from riffles than from backwater and beach habitats. Macroinvertebrate taxa from E. virescens stomachs were more strongly correlated with sediment samples from all three habitats than were those from the other two species. The species accumulation curves and higher mean dispersion values, compared with with sediment samples suggest that E. virescens is more efficient than sediment samples and the other fish studied at collecting benthic taxa. We conclude that by analyzing the stomach contents of benthophagous fishes it is possible to assess important characteristics of benthic communities (dispersion, taxonomic composition and diversity. This is especially true

  4. Effects of dissolved oxygen concentration and flow velocity on corrosion of carbon steel in tap water; Suidosuichu ni okeru tansoko fushoku ni oyobosu yoson sanso nodo to ryusoku no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Murata, M.; Ouchi, M. [Miura Institute of Research and Development, Ehime (Japan); Fujii, T.; Shiraishi, H.; Kawahito, A. [Miura Co. Ltd., Ehime (Japan)

    1998-05-15

    Discussions were given on the effects of dissolved oxygen (DO) concentration and flow velocity on temporary corrosion of carbon steel in tap water by using a membrane-type deaerator which uses a hollow fiber membrane for air separation. In deaerated air with DO at 0.5 mg per liter, active corrosion took place, in which corrosion rate increases with flow velocity in a range from 0.5 to 2.0 m/s. The corrosion rate in a carbon steel in deaerated air with flow velocity of 0.5 m/s and DO of 0.5 mg per liter decreased to 1/4 to 1/5 of that in non-deaerated water, showing effectiveness in preventing corrosion and red water in pipings in buildings. The corrosion prevention effect is more excellent especially in low flow velocity regions, meaning it being suitable for corrosion prevention in building pipings for water supply which is low in flow velocity and often subjected to stagnation. It was found that, even at about the same flow velocity, the deaerated water is on the safer side than the non-deaerated water. With waters having DO of 2.0 and 4.0 mg per liter, the corrosion rate decreased when flow velocity is higher than 1 m/s, with appearance of passivation trend. There is a relation with high reproducibility between the corrosion rate in the carbon steel and oxygen supply amount, whereas the curve showed a maximum value. This maximum value is thought a transition point from active state corrosion to passive state corrosion. 9 refs., 6 figs., 2 tabs.

  5. Combining taxonomy and function in the study of stream macroinvertebrates

    Directory of Open Access Journals (Sweden)

    Kenneth W. Cummins

    2016-03-01

    Full Text Available Over the last fifty years, research on freshwater macroinvertebrates has been driven largely by the state of the taxonomy of these animals. In the great majority of studies conducted during the 2000s macroinvertebrates have been operationally defined by investigators as invertebrates retained by a 250 μ mesh in field sampling devices. Significant advances have been and continue to be made in developing ever more refined keys to macroinvertebrate groups. The analysis by function is a viable alternative when advances in macroinvertebrate ecological research is restricted by the level of detail in identifications. Focus on function, namely adaptations of macroinvertebrates to habitats and the utilization of food resources, has facilitated ecological evaluation of freshwater ecosystems (Functional feeding groups; FFG. As the great stream ecologist Noel Hynes observed, aquatic insects around the world exhibit similar morphologies and behaviors, even though they are in very different taxonomic groups. This is the basis for the FFG analysis that was initially developed in the early 1970s. FFG analysis applies taxonomy only to the level of detail that allows assignment to one of six FFG categories: scrapers adapted to feed on periphyton, detrital shredders adapted to feed on coarse (CPOM riparian-derived plant litter that has been colonized by microbes, herbivore shredders that feed on live, rooted aquatic vascular plants, filtering collectors adapted to remove fine particle detritus (FPOM from the water column, gathering collectors adapted to feed on FPOM where it is deposited on surfaces or in crevices in the sediments, and predators that capture live prey. The interacting roles of these FFGs in stream ecosystems were originally depicted in a conceptual model. Thus, there are a limited number of adaptations exhibited by stream macroinvertebrates that exploit these habitats and food resources. This accounts for the wide range of macroinvertebrate taxa

  6. 溶氧对斑点叉尾鮰免疫机能及抗病力的影响%Effect of Dissolved Oxygen on the Immune Response and Susceptibility of the Channel Catfish to Ichthyophthirius multifiliis

    Institute of Scientific and Technical Information of China (English)

    鲁伦文

    2011-01-01

    [目的]研究溶氧水平对斑点叉尾鮰免疫机能及抗病力的影响.[方法]设置4个溶氧水平:(2.01±0.26)、(4.17±0.53)、(6.32±0.59)、(8.86±1.01)mg/L,分别记作A、B、C、D组,饲养斑点叉尾鮰,于饲养试验开始后的0、7、14、28、56d取样观察外周血白细胞数(WBC)、白细胞吞噬百分比(PP)和吞噬指数(PI)、溶菌酶活力、补体C3和C4水平、皮质醇及血糖水平,并观察小瓜虫感染后上述指标的变化及累计死亡率.[结果]饲养试验最后,WBC、PP、PI均以A组最低;饲养试验期间,A组溶菌酶活力、皮质醇水平和血糖水平先升后降,补体C3、C4含量显著降低;除血糖外,各组所有指标均在感染前期升高,后期显著降低;A组免疫指标在感染后期最低,同时累计死亡率最高.[结论]慢性低氧胁迫降低了斑点叉尾鮰的免疫机能及对小瓜虫的抗病力.%[Objective] The dissolved oxygen affecting the immune response and susceptibility of the channel catfish(Ictalurus punctatus) to Ichthyophthirius multifiliis was analyzed. [ Method] The white blood cell( WBC) , percentage of phagocytic leucocyte(PP) , phagocytic index (PI) , plasma lysozyme activity, level of complement factor C3 and C4, plasma cortisol and glucose in blood of the channel catfish were tested at the at 0, 7th, 14th, 28th and 56th day after the channel catfish were treated with 4 different concentrations of dissolved oxygenf A, (2.01 ±0.26) mg/L; B, (4.17 ±0.53) mg/L; C, (6.32 ±0.59) mg/L; and D, (8.86±1.01 )mg/L] in water. The variation of the testing value mentioned-above of the infected channel catfish and its cumulative mortality were investigated. [ Results] The value of WBC, PP and PI in Treatment A were lowest at the end of experiment, which was significant different with others. During the experimental period, the plasma lysozyme activity, the level of plasma cortisol and glucose in blood of the channel catfish in Treatment A were firstly raised and then

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

    Science.gov (United States)

    Heddam, Salim

    2014-01-01

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

  8. 四氯化碳显色目视比色法测定溶解氧方法的研究%Research on Determining Dissolved Oxygen with Visual Colorimetry of Carbon Tetrachloride

    Institute of Scientific and Technical Information of China (English)

    韩丽媛

    2011-01-01

    This paper introduces the study of determination of dissolved oxygen by visual colorimetry with carbon tetrachloride. This method is proved quick and exact, clear in showing the experimental results and suit- able for emergency measurement by comparison of the choices of standard reagents, extraction solvents, the quantity of potassium iodide (KI) and tset of stability, denoisingt, environmental temperature and accuracy and precision.%本文介绍了四氯化碳显色目视比色法测定溶解氧方法的研究过程,通过时分析方法中,标准试剂的选择,萃取剂的选择,碘化钾(K1)用量的选择,及稳定性实验,消除干扰实验,环境温度实验,方法准确度及精密度实验,表明此方法快速、准确、分析结果直观、适合应急监测。

  9. Crescimento de alevinos de jundiá, Rhamdia quelen (Pisces, Pimelodidae, em diferentes concentrações de oxigênio dissolvido = Growth of silver catfish Rhamdia quelen (Pisces, Pimelodidae fingerlings in different dissolved oxygen concentrations

    Directory of Open Access Journals (Sweden)

    Giancarlo Maffezzolli

    2006-01-01

    Full Text Available O objetivo deste estudo foi avaliar o crescimento de alevinos de jundiá, Rhamdia quelen, em 5 concentrações de oxigênio dissolvido: 1,3 (T1, 2,4 (T2, 3,7 (T3, 5,4 (T4 e 7,5 mg O2/L (T5. O estudo utilizou o modelo experimental inteiramente ao acaso com 3 repetições e foi conduzido por 25 dias. Os alevinos foram distribuídos em tanques circulares de fibra de vidro de 150 L mantidos na escuridão e dotados de aeração mecânica, filtro biológico e renovação de água, nadensidade de 34 indivíduos/tanque. A sobrevivência foi menor nos extremos testados (T1 e T5. Maior crescimento em peso e em comprimento e melhor conversão alimentar foram obtidos com o aumento da concentração de oxigênio dissolvido. Os alevinos de jundiá apresentaram incremento em peso, mesmo na menor concentração de oxigênio dissolvido (T1, e T4 produziu os melhores efeitos sobre o desenvolvimento.This study's aim was evaluate the growth of silver catfish (Rhamdia quelen fingerlings on five dissolved oxygen concentrations: 1,3 (T1, 2,4 (T2, 3,7 (T3, 5,4 (T4 and 7,5 mg O2/L (T5. A completely random design experiment with three repetitions was used and the experiment was carried out during 25 days. Fingerlings were distributed in circular, 150-L fiberglass tanks kept in darkness, endowed with mechanic and biological filters and water renewal, at a stocking density of 34 individuals/tank. Survival was lower at the extreme tested levels (T1 and T5. Better growth in weight, length and food conversion were found at increasing oxygen concentrations. Even at the lowest oxygen concentration (T1 fingerlings showed growth increase. The best effects on silver catfish fingerlings development was observed at T4.

  10. Impact assessment of agricultural driven stressors on benthic macroinvertebrates using simulated data.

    Science.gov (United States)

    Stefanidis, K; Panagopoulos, Y; Mimikou, M

    2016-01-01

    Agricultural land use poses a significant threat to the ecological integrity of rivers in Europe. Particularly in the Mediterranean, water abstraction and nutrient application are anthropogenic pressures that have a significant impact on aquatic habitats and biodiversity. In this article, we assessed the effects of agricultural management practices on benthic macroinvertebrates in a large river basin of central Greece using simulated data based on the application of SWAT (Soil Water Assessment Tool) model. Physicochemical and hydrological output variables of the model were used as predictors of the ASPT (Average Score Per Taxon) metric based on a correlated component regression analysis (CCR) built on empirical data. The estimation of ASPT was performed for the wet and dry seasons within a 20-year period for a total of 47 subbasins under the baseline conditions and after implementing three management scenarios that reduced: a) irrigation water applied to crops by 30%, b) chemical fertilization applied to crops by 30% and c) both irrigation and fertilization by 30%. The results revealed that application of the reduced irrigation resulted to a slight increase of the simulated dissolved inorganic nitrogen concentration (DIN), which in turn decreased the mean ASPT in 21 of the 47 subbasins implying a negative effect on the macroinvertebrate communities. On the contrary, the reduction of fertilization as well as the combined scenario decreased both the simulated DIN and phosphate concentration causing an increase of the mean ASPT for a total of 40 of the 47 subbasins. Based on these results, we suggest that the best management option is a combined practice of deficit irrigation and fertilization reduction since it improved water quality, increased ASPT values and saved a considerable amount of water. Overall, this work demonstrates a simple methodology that can efficiently assess the effects of agricultural management practices on biotic indicators.

  11. 基于物联网技术的水质监测系统中不同溶解氧传感器应用效果初探%Preliminary Study on Application Effect of Different Dissolved Oxygen Sensors in Online Water Environment Monitoring System Based on the Internet of Things

    Institute of Scientific and Technical Information of China (English)

    房景辉; 邹健; 刘毅; 汪水吉; 徐松华

    2016-01-01

    将测量原理不同的电化学和光学溶解氧传感器分别集成在基于物联网的水质在线监测系统中,并应用于长时间监测海水养殖场的溶解氧,结果表明:两种传感器都能在一定时间内正常监测水体中的溶解氧,但基于传统原电池法的电化学溶解氧传感器在海水养殖水质监测中稳定性较差,维护复杂;而基于动态荧光淬灭的光学溶解氧传感器监测值相对比较稳定,且维护简单。本研究在实际应用层面上为两种类型溶解氧传感器的使用提供了技术参考。%Two kinds of dissolved oxygen sensors with different measuring principles (electrochemical method and optical fluorescence method)were integrated in the online water quality monitoring system based on the Internet of Things,and were used for long -term monitoring of dissolved oxygen in seawater farms.The results showed that both the two kinds of sensors could normally monitor the dissoved oxygen in a certain peri-od.The dissolved oxygen sensors based on optical fluorescence method exhibited excellent long -term stability and simple maintenance relative to galvanic cell sensors in marine culture.This study provided technic refer-ences for the practical application of the two kinds of dissolved oxygen sensors.

  12. Are sugarcane leaf-detritus well colonized by aquatic macroinvertebrates?

    Directory of Open Access Journals (Sweden)

    Luciene Aparecida Leite-Rossi

    Full Text Available AIM: The aim was to compare the kinetics of decomposition and the colonization of leaf litter of two plant species, the native Talauma ovata (pinha-do-brejo and the exotic Saccharum officinarum (sugarcane, by aquatic macroinvertebrates; METHODS: From each substrate, three recipients of colonization were taken from a stream, and the specimens identified to the lowest taxonomic level on days 7, 15, 34, 44, 61 and 75. The debris was weighed at the beginning and end of the experiment and determined their cell wall fractions; RESULTS: The coefficients of mineralization indicated higher velocity decay of organic matter refractory in T. ovata. There was no difference in taxonomic structure of macroinvertebrates, between the two substrates, but the community exhibited distinct functional feeding groups in the peak of colonization, with a greater number of shredders in T. ovata. The successive states of decomposition of the two plant detritus showed distinct macroinvertebrate densities; CONCLUSIONS: The amount and state of the plant biomass were important factors influencing the density and diversity of the macroinvertebrate fauna throughout the process of organic decomposition.

  13. Patterning and predicting aquatic macroinvertebrate diversities using artificial neural network

    NARCIS (Netherlands)

    Park, Y.S.; Verdonschot, P.F.M.; Chon, T.S.; Lek, S.

    2003-01-01

    A counterpropagation neural network (CPN) was applied to predict species richness (SR) and Shannon diversity index (SH) of benthic macroinvertebrate communities using 34 environmental variables. The data were collected at 664 sites at 23 different water types such as springs, streams, rivers, canals

  14. Influence of macroinvertebrate sample size on bioassessment of streams

    NARCIS (Netherlands)

    Vlek, H.E.; Sporka, F.; Krno, I.

    2006-01-01

    In order to standardise biological assessment of surface waters in Europe, a standardised method for sampling, sorting and identification of benthic macroinvertebrates in running waters was developed during the AQEM project. The AQEM method has proved to be relatively time-consuming. Hence, this stu

  15. Macrophyte presence and growth form influence macroinvertebrate community structure

    NARCIS (Netherlands)

    Walker, P.D.; Wijnhoven, S.; van der Velde, G.

    2013-01-01

    Multivariate analysis demonstrated that macroinvertebrate assemblages of macrophyte-dominated sub-habitats within a small eutrophic pond differed markedly from those of Bottom substrate and Open water habitats. Certain habitats (e.g. Nymphaea and Phragmites) appeared to be quite similar in their

  16. Qualitative Macroinvertebrate Assessment of Crouch Branch, June 1999

    Energy Technology Data Exchange (ETDEWEB)

    Specht, W.L.

    1999-11-05

    An assessment of the macroinvertebrate community of Crouch Branch was performed in June 1999 to determine if effluent from the H-02 outfall is impairing the quality of the stream. Concurrent samples were collected for metals analyses (copper and zinc). The results of the study indicate that the stream is most impaired just downstream from the H-02 outfall and that the quality of the stream biota improves with increasing distance from the outfall. Conversely, macroinvertebrate habitat quality is best just downstream from the H-02 outfall. The midreaches of the stream contain very poor habitat quality, and the lower reaches of the stream, contain habitat of intermediate quality. Although much of the stream has degraded habitat due to channel erosion and scouring, there is strong evidence to suggest that the impairment is due to elevated concentrations of copper and zinc that are present in the H-02 effluent. A comparison of macroinvertebrate data collected in 1997 to the data collected in this study indicates that the macroinvertebrate community of Crouch Branch has improved markedly in the last two years.

  17. Development of a local-scale urban stream assessment method using benthic macroinvertebrates: An example from the Santa Clara Basin, California

    Science.gov (United States)

    Carter, J.L.; Purcell, A.H.; Fend, S.V.; Resh, V.H.

    2009-01-01

    Research that explores the biological response to urbanization on a site-specific scale is necessary for management of urban basins. Recent studies have proposed a method to characterize the biological response of benthic macroinvertebrates along an urban gradient for several climatic regions in the USA. Our study demonstrates how this general framework can be refined and applied on a smaller scale to an urbanized basin, the Santa Clara Basin (surrounding San Jose, California, USA). Eighty-four sampling sites on 14 streams in the Santa Clara Basin were used for assessing local stream conditions. First, an urban index composed of human population density, road density, and urban land cover was used to determine the extent of urbanization upstream from each sampling site. Second, a multimetric biological index was developed to characterize the response of macroinvertebrate assemblages along the urban gradient. The resulting biological index included metrics from 3 ecological categories: taxonomic composition ( Ephemeroptera, Plecoptera, and Trichoptera), functional feeding group (shredder richness), and habit ( clingers). The 90th-quantile regression line was used to define the best available biological conditions along the urban gradient, which we define as the predicted biological potential. This descriptor was then used to determine the relative condition of sites throughout the basin. Hierarchical partitioning of variance revealed that several site-specific variables (dissolved O2 and temperature) were significantly related to a site's deviation from its predicted biological potential. Spatial analysis of each site's deviation from its biological potential indicated geographic heterogeneity in the distribution of impaired sites. The presence and operation of local dams optimize water use, but modify natural flow regimes, which in turn influence stream habitat, dissolved O2, and temperature. Current dissolved O2 and temperature regimes deviate from natural

  18. Dissolved Oxygen - Live Hauling of Fish

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — In certain markets, live fish can be sold for substantially higher prices than fresh dressed fish. A significant live-haul industry has developed in the U.S. and...

  19. Sediment Burial Intolerance of Marine Macroinvertebrates.

    Directory of Open Access Journals (Sweden)

    Vicki J Hendrick

    Full Text Available The marine environment contains suspended particulate matter which originates from natural and anthropogenic sources. Settlement of this material can leave benthic organisms susceptible to smothering, especially if burial is sudden i.e. following storms or activities such as dredging. Their survival will depend on their tolerance to, and their ability to escape from burial. Here we present data from a multi-factorial experiment measuring burial responses incorporating duration, sediment fraction and depth. Six macroinvertebrates commonly found in sediment rich environments were selected for their commercial and/or conservation importance. Assessments revealed that the brittle star (Ophiura ophiura, the queen scallop (Aequipecten opercularis and the sea squirt (Ciona intestinalis were all highly intolerant to burial whilst the green urchin (Psammichinus miliaris and the anemone (Sagartiogeton laceratus, showed intermediate and low intolerance respectively, to burial. The least intolerant, with very high survival was the Ross worm (Sabellaria spinulosa. With the exception of C. intestinalis, increasing duration and depth of burial with finer sediment fractions resulted in increased mortality for all species assessed. For C. intestinalis depth of burial and sediment fraction were found to be inconsequential since there was complete mortality of all specimens buried for more than one day. When burial emergence was assessed O. ophiura emerged most frequently, followed by P. miliaris. The former emerged most frequently from the medium and fine sediments whereas P. miliaris emerged more frequently from coarse sediment. Both A. opercularis and S. laceratus showed similar emergence responses over time, with A. opercularis emerging more frequently under coarse sediments. The frequency of emergence of S. laceratus increased with progressively finer sediment and C. intestinalis did not emerge from burial irrespective of sediment fraction or depth. Finally

  20. Linkage of iron elution and dissolved oxygen consumption with removal of organic pollutants by nanoscale zero-valent iron: Effects of pH on iron dissolution and formation of iron oxide/hydroxide layer.

    Science.gov (United States)

    Fujioka, Nanae; Suzuki, Moe; Kurosu, Shunji; Kawase, Yoshinori

    2016-02-01

    The iron elution and dissolved oxygen (DO) consumption in organic pollutant removal by nanoscale zero-valent iron (nZVI) was examined in the range of solution pH from 3.0 to 9.0. Their behaviors were linked with the removal of organic pollutant through the dissolution of iron and the formation of iron oxide/hydroxide layer affected strongly by solution pH and DO. As an example of organic pollutants, azo-dye Orange II was chosen in this study. The chemical composition analyses before and after reaction confirmed the corrosion of nZVI into ions, the formation of iron oxide/hydroxide layer on nZVI surface and the adsorption of the pollutant and its intermediates. The complete decolorization of Orange II with nZVI was accomplished very quickly. On the other hand, the total organic carbon (TOC) removal was considerably slow and the maximum TOC removal was around 40% obtained at pH 9.0. The reductive cleavage of azo-bond by emitted electrons more readily took place as compared with the cleavage of aromatic rings of Orange II leading to the degradation to smaller molecules and subsequently the mineralization. A reaction kinetic model based on the Langmuir-Hinshelwood/Eley-Rideal approach was developed to elucidate mechanisms for organic pollutant removal controlled by the formation of iron oxide/hydroxide layer, the progress of which could be characterized by considering the dynamic concentration changes in Fe(2+) and DO. The dynamic profiles of Orange II removal linked with Fe(2+) and DO could be reasonably simulated in the range of pH from 3.0 to 9.0.

  1. Effects of Dissolved Oxygen on Removal of Cr (Ⅵ) by Zero-valent Iron%溶解氧对零价铁去除水中六价铬的影响

    Institute of Scientific and Technical Information of China (English)

    曹茜; 陈家玮

    2013-01-01

    六价铬Cr(Ⅵ)有巨毒性,对人类及生态环境有极大危害,运用纳米零价铁(nZVI)去除水中六价铬是一种快速高效的环境修复手段.前人的研究更多报道了pH值、温度、初始浓度等因素的影响,溶解氧(DO)的存在对于nZVI去除水体中Cr(Ⅵ)的作用却少有研究.在对比普通铁粉和纳米铁对六价铬去除的基础上,着重探讨了溶解氧(DO)对水中六价铬去除效果的影响及作用机制.批实验短期结果表明:由于纳米铁有较大的比表面积和更高的反应活性,导致nZVI的除Cr(Ⅵ)效率明显高于普通铁粉;溶解氧的存在促进了nZVI对Cr(Ⅵ)的去除,这是因为氧化作用产生较多的Fe2+,有利于Cr(Ⅵ)的去除,随着nZVI进一步氧化,产生的针铁矿、磁铁矿等铁氧化物能够进一步吸附Cr(Ⅵ),使得在有氧环境下Cr(Ⅵ)的去除效果好于无氧环境.%Nanoscale zero-valent iron ( nZVI) is a kind of effective material for remediation of polluted soil and water. It can be used to remove hexavalent chromium, Cr ( VI) , which is toxic and easily mobile in the environment. In recent years, many researches have studied impacts of temperature, pH value, initial concentration, etc. in the systems, while dissolved oxygen (DO) is seldom to discuss. Herein, we compared zero-valent iron (ZVI) and nZVI for Cr ( VI) removal in the presence or absence of oxygen in water. We focused on the effect of DO on removal of Cr( VI) by nZVI. The short-term batch experiment showed that nZVI is significantly more effective in removing Cr ( VI) than ZVI due to large specific surface area and high activity of nano particles. Oxygen enhances Cr( VI) removal in water by nZVI in that more production of Fe 2+ , goethite, magnetite, etc. can be useful in this process and iron oxides can easily adsorb Cr( VI) on the surface of nZVI in the presence of oxygen.

  2. Macroinvertebrates as indicators of fish absence in naturally fishless lakes

    Science.gov (United States)

    Schilling, Emily Gaenzle; Loftin, C.S.; Huryn, Alexander D.

    2009-01-01

    1. Little is known about native communities in naturally fishless lakes in eastern North America, a region where fish stocking has led to a decline in these habitats. 2. Our study objectives were to: (i) characterise and compare macroinvertebrate communities in fishless lakes found in two biophysical regions of Maine (U.S.A.): kettle lakes in the eastern lowlands and foothills and headwater lakes in the central and western mountains; (ii) identify unique attributes of fishless lake macroinvertebrate communities compared to lakes with fish and (iii) develop a method to efficiently identify fishless lakes when thorough fish surveys are not possible. 3. We quantified macroinvertebrate community structure in the two physiographic fishless lake types (n = 8 kettle lakes; n = 8 headwater lakes) with submerged light traps and sweep nets. We also compared fishless lake macroinvertebrate communities to those in fish-containing lakes (n = 18) of similar size, location and maximum depth. We used non-metric multidimensional scaling to assess differences in community structure and t-tests for taxon-specific comparisons between lakes. 4. Few differences in macroinvertebrate communities between the two physiographic fishless lake types were apparent. Fishless and fish-containing lakes had numerous differences in macroinvertebrate community structure, abundance, taxonomic composition and species richness. Fish presence or absence was a stronger determinant of community structure in our study than differences in physical conditions relating to lake origin and physiography. 5. Communities in fishless lakes were more speciose and abundant than in fish-containing lakes, especially taxa that are large, active and free-swimming. Families differing in abundance and taxonomic composition included Notonectidae, Corixidae, Gyrinidae, Dytiscidae, Aeshnidae, Libellulidae and Chaoboridae. 6. We identified six taxa unique to fishless lakes that are robust indicators of fish absence: Graphoderus

  3. Impact of pesticides on hyphomycetes leaf processing and macroinvertebrate shredding activity

    DEFF Research Database (Denmark)

    Juul Monberg, Rikke; Rasmussen, Jes; Baatrup-Pedersen, Annette

    -cypermethrine (100, 1000 or 2000 ng/L) for three hours. Subsequently, we studied post exposure leaf degradation for four weeks in the laboratory in the presence/absence of two macroinvertebrate shredders (Gammarus pulex and Halesus radiatus) applying a classic crossed factorial design. Preliminary results indicate...... the first post exposure week when macroinvertebrate shredders were present. After four weeks no differences were apparent among treatments indicating a strong degree of functional redundancy applying this macroinvertebrate assemblage....

  4. A sampler for quantifying the vertical distribution of macroinvertebrates in shallow wetlands

    Science.gov (United States)

    MacKay, J.; Euliss, N.H.

    1993-01-01

    A sampler for quantifying the vertical distribution of aquatic macroinvertebrates in wetlands is described. This device will facilitate quantitative sampling of macroinvertebrates in waterfowl ecology and related studies. Because it simultaneously collects benthic and pelagic invertebrates the sampler reduces bias associated with sampling macroinvertebrates that occupy the benthic-pelagic interface of wetlands. The sampling device also separates benthic and pelagic macroinvertebrates into separate vertical profiles to facilitate studies of distribution patterns or the influence of chemical and physical gradients on invertebrate vertical distribution.

  5. A Stream Multimetric Macroinvertebrate Index (MMI) for the Sand Hills Ecoregion of the Southeastern Plains, USA

    Science.gov (United States)

    Kosnicki, Ely; Sefick, Stephen A.; Paller, Michael H.; Jerrell, Miller S.; Prusha, Blair A.; Sterrett, Sean C.; Tuberville, Tracey D.; Feminella, Jack W.

    2016-10-01

    A macroinvertebrate multimetric index is an effective tool for assessing the biological integrity of streams. However, data collected under a single protocol may not be available for an entire region. We sampled macroinvertebrates from the full extent of the Sand Hills ecoregion Level IV of the Southeastern Plains with a standard protocol during the summers of 2010-2012. We evaluated the performance of 94 metrics through a series of screening criteria and built 48 macroinvertebrate multimetric indexs with combinations of the best performing metrics, representing richness, habit, functional feeding guild, sensitivity, and community composition. A series of narrative-response tests for each macroinvertebrate multimetric index was used to find the best performing macroinvertebrate multimetric index which we called the Sand Hills macroinvertebrate multimetric index. The Sand Hills macroinvertebrate multimetric index consisted of the measures Biotic Index, % Shredder taxa, Clinger taxa2/total taxa, Plecoptera and Trichoptera richness, and Tanytarsini taxa2/Chironomidae taxa. Comparison of the Sand Hills macroinvertebrate multimetric index with existing assessment tools calculated with our data indicated that the Sand Hills macroinvertebrate multimetric index performs at a high level with regard to identifying degraded sites and in its response to stress gradients.

  6. Impacts of Shorebirds on Macroinvertebrates in the Lower Mississippi Alluvial Valley

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Study of the impacts of migratory birds by assessing macroinvertebrate community composition, abundance and biomass associated with habitats.

  7. Biological and physical conditions of macroinvertebrates in reference lowland streams

    Science.gov (United States)

    de Brouwer, Jan; Eekhout, Joris; Verdonschot, Piet

    2016-04-01

    Channelisation measures taken halfway the 20th century have had destructive consequences for the diversity of the ecology in the majority of the lowland streams in countries such as the Netherlands. Currently, stream restoration measures are being implemented in these degraded lowland streams, where design principles are often based on outdated relationships between biological and physical conditions. Little is known about the reference conditions in these streams. Therefore, the aim of this research is to quantify the relationships between biological and physical conditions of macroinvertebrates in reference lowland streams. The research was conducted in four near-natural lowland streams in Central Poland. Field data were obtained during a field campaign in 2011. The following data were obtained in a 50-m reach in each of the four streams: macroinvertebrate sampling, spatial habitat patterns, bathymetry, and flow-velocity. Furthermore, water level, light sensitivity and temperature sensors were installed to obtain the temporal dynamic of these streams. Macroinvertebrates were sampled in 9 different habitat types, i.e. sand, gravel, fine organic matter, stones, branches, leaves, silt, vegetation, and wood. Macroinvertebrates were determined to the highest taxonomic level possible. Data from the bathymetrical surveys were interpolated on a grid and bathymetrical metrics were determined. Flow velocity measurements were related to habitats and flow velocity metrics were determined. Analysis of the data shows that flow conditions vary among the different habitat, with a gradient from hard substrates towards soft substrates. Furthermore, the data show that stream as a unit best explains species composition, but also specific habitat conditions, such as substrate type and flow velocity, correlate with species composition. More specific, the data shows a strong effect of wood on species composition. These findings may have implications for stream restoration design, which

  8. Fire, flow and dynamic equilibrium in stream macroinvertebrate communities

    Science.gov (United States)

    Arkle, R.S.; Pilliod, D.S.; Strickler, K.

    2010-01-01

    The complex effects of disturbances on ecological communities can be further complicated by subsequent perturbations within an ecosystem. We investigated how wildfire interacts with annual variations in peak streamflow to affect the stability of stream macroinvertebrate communities in a centra