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1

Pockwock-Bowater Watershed Project. Technical Note # 2 Overview of daily stream data for stream discharge, temperature, electrical conductivity, pH, dissolved oxygen content, and turbidity  

Microsoft Academic Search

Methods. The data that were acquired for stream discharge, temperature, electrical conductivity, and pH, but not in terms of stream turbidity for Peggy Brook, Long Ponds Stream, Sand Brook West and Walsh Brook were all compiled into the Excel spreadsheet format, with hourly resolution. The data were inspected in terms of erratic readings, sudden shifts, sensor instabilities (marked by onset

Todd Smith; Joe Pomeroy; Nancy McInnis Leek; Fan-Rui Meng; P. A. Arp

2

Electrical conductivity and total dissolved solids in urine.  

PubMed

The objective of this paper is to study the relevance of electrical conductivity (EC) and total dissolved solids (TDS) in early morning and random samples of urine of urinary stone patients; 2,000 urine samples were studied. The two parameters were correlated with the extent of various urinary concrements. The early morning urine (EMU) and random samples of the patients who attended the urinary stone clinic were analysed routinely. The pH, specific gravity, EC, TDS, redox potential, albumin, sugar and microscopic study of the urinary sediments including red blood cells (RBC), pus cells (PC), crystals, namely calcium oxalate monohydrate (COM), calcium oxalate dihydrate (COD), uric acid (UA), and phosphates and epithelial cells were assessed. The extent of RBC, PC, COM, COD, UA and phosphates was correlated with EC and TDS. The values of EC ranged from 1.1 to 33.9 mS, the mean value being 21.5 mS. TDS ranged from 3,028 to 18,480 ppm, the mean value being 7,012 ppm. The TDS levels corresponded with EC of urine. Both values were significantly higher (P < 0.05) in the EMU samples than the random samples. There was a statistically significant correlation between the level of abnormality in the urinary deposits (r = +0.27, P < 0.05). In samples, where the TDS were more than 12,000 ppm, there were more crystals than those samples containing TDS less than 12,000 ppm. However, there were certain urine samples, where the TDS were over 12,000, which did not contain any urinary crystals. It is concluded that the value of TDS has relevance in the process of stone formation. PMID:19921168

Fazil Marickar, Y M

2009-11-17

3

Electrical conductivity and total dissolved solids in urine  

Microsoft Academic Search

The objective of this paper is to study the relevance of electrical conductivity (EC) and total dissolved solids (TDS) in\\u000a early morning and random samples of urine of urinary stone patients; 2,000 urine samples were studied. The two parameters\\u000a were correlated with the extent of various urinary concrements. The early morning urine (EMU) and random samples of the patients\\u000a who

Y. M. Fazil Marickar

2010-01-01

4

pH change induces shifts in the size and light absorption of dissolved organic matter  

Microsoft Academic Search

Dissolved organic matter (DOM) influences inland water ecosystems through its light absorbing qualities. We investigated how\\u000a pH affects light absorption by DOM with pH manipulation experiments and with data from two lake surveys. We hypothesized that:\\u000a (1) light absorption and photobleaching of DOM would increase with increasing pH, and (2) as a result of photobleaching, molar\\u000a absorption (i.e. light absorbance

Michael L. Pace; Isabel Reche; Jonathan J. Cole; Antonio Fernández-Barbero; Ignacio P. Mazuecos; Yves T. Prairie

5

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

Microsoft Academic Search

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

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

1981-01-01

6

Relative Effect of Temperature and pH on Diel Cycling of Dissolved Trace Elements in Prickly Pear Creek, Montana  

Microsoft Academic Search

Diel (24 hr) cycles in dissolved metal and As concentrations have been documented in many northern Rocky Mountain streams in the U.S.A. The cause(s) of the cycles are unknown, although temperature- and pH-dependent sorption reactions have been cited as likely causes. A light\\/dark experiment was conducted to isolate temperature and pH as variables affecting diel metal cycles in Prickly Pear

Clain A. Jones; David A. Nimick; R. Blaine McCleskey

2004-01-01

7

Effects of pH on Dissolved Organic Matter From Freshwater Algal Species  

NASA Astrophysics Data System (ADS)

Dissolved organic matter (DOM) is ubiquitous in all natural waters. The nature and composition of aquatic DOM depends on its origin (autochthonous vs. allochthonous) and the physical chemical conditions (pH) of the system. It is clear that autochthonous DOM of algal origin is an important contributor to the DOM pool in most aquatic systems. Little is known on its nature and composition. In this study, algal monocultures of S. acutus and F. crotonensis were grown at two different pHs (pH 7 and 5). The production of exudates was monitored over time and characterized by dissolved organic carbon content, absorbance and synchronous fluorescence. Results indicate a significant difference in the concentration of dissolved organic carbon (DOC) formed per species. The ratio of DOC to chlorophyll a is ten times greater in S. acutus than F. crotonensis. In terms of composition, the production of humic-like compounds varies between species with F. crotonensis producing up to four fold more at natural pH. At lower pH, the production of algal DOM is less but there were more proteins and humic materials generated by both species under decreasing pH, with a significant increase in the S. acutus species. Therefore, the concentration and composition of DOM depends not only on algal species but also on the physical chemical condition (pH level) indicating that water acidification would have a major impact on DOM composition.

Kehret, Y.; Gueguen, C.

2009-05-01

8

THE EFFECT OF PH AND DISSOLVED INORGANIC CARBON ON THE PROPERTIES OF IRON COLLOIDAL SUSPENSIONS  

EPA Science Inventory

Discolored water resulting from suspended iron particles is a relatively common drinking water consumer complaint. These particles result from the oxygenation of Fe(II), and this study shows that pH and dissolved inorganic carbon (DIC) have important effects on their properties....

9

Effects of pH on Dissolved Organic Matter From Freshwater Algal Species  

Microsoft Academic Search

Dissolved organic matter (DOM) is ubiquitous in all natural waters. The nature and composition of aquatic DOM depends on its origin (autochthonous vs. allochthonous) and the physical chemical conditions (pH) of the system. It is clear that autochthonous DOM of algal origin is an important contributor to the DOM pool in most aquatic systems. Little is known on its nature

Y. Kehret; C. Gueguen

2009-01-01

10

pH measurement of low-conductivity waters  

USGS Publications Warehouse

pH is an important and commonly measured parameter of precipitation and other natural waters. The various sources of errors in pH measurement were analyzed and procedures for improving the accuracy and precision of pH measurements in natural waters with conductivities of < 100 uS/cm at 25 C are suggested. Detailed procedures are given for the preparation of dilute sulfuric acid standards to evaluate the performance of pH electrodes in low conductivity waters. A daily check of the pH of dilute sulfuric acid standards and deionized water saturated with a gas mixture of low carbon dioxide at partial pressure (air) prior to the measurement of the pH of low conductivity waters is suggested. (Author 's abstract)

Busenberg, Eurybiades; Plummer, L. N.

1987-01-01

11

Limestone drains to increase pH and remove dissolved metals from acidic mine drainage  

Microsoft Academic Search

Despite encrustation by Fe and Al hydroxides, limestone can be effective for remediation of acidic mine drainage (AMD). Samples of water and limestone (CaCO3) were collected periodically for 1 a at 3 identical limestone-filled drains in Pennsylvania to evaluate the attenuation of dissolved metals and the effects of pH and Fe- and Al-hydrolysis products on the rate of CaCO3 dissolution.

Charles A. Cravotta III; Mary Kay Trahan

1999-01-01

12

in situ interlaboratory comparisons for dissolved oxygen concentration and pH  

Microsoft Academic Search

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

Lauri Jalukse; Viktor Vabson; Ivo Leito

2006-01-01

13

Specific Conductance Method for In Situ Estimation of Total Dissolved Solids  

Microsoft Academic Search

There are two methods that are commonly used for determining total dissolved solids in water. This article proposes another method— determination by means of electrical conductance measurement. An excellent relationship was discovered between specific conductance and total dissolved solids of mountain streams.

Teja Singh; Y. P. Kalra

1975-01-01

14

pH modeling for maximum dissolved organic matter removal by enhanced coagulation.  

PubMed

Correlations between raw water characteristics and pH after enhanced coagulation to maximize dissolved organic matter (DOM) removal using four typical coagulants (FeCl3, Al2(SO4)3, polyaluminum chloride (PACl) and high performance polyaluminum chloride (HPAC)) without pH control were investigated. These correlations were analyzed on the basis of the raw water quality and the chemical and physical fractionations of DOM of thirteen Chinese source waters over three seasons. It was found that the final pH after enhanced coagulation for each of the four coagulants was influenced by the content of removable DOM (i.e. hydrophobic and higher apparent molecular weight (AMW) DOM), the alkalinity and the initial pH of raw water. A set of feed-forward semi-empirical models relating the final pH after enhanced coagulation for each of the four coagulants with the raw water characteristics were developed and optimized based on correlation analysis. The established models were preliminarily validated for prediction purposes, and it was found that the deviation between the predicted data and actual data was low. This result demonstrated the potential for the application of these models in practical operation of drinking water treatment plants. PMID:22655388

Xie, Jiankun; Wang, Dongsheng; van Leeuwen, John; Zhao, Yanmei; Xing, Linan; Chow, Christopher W K

2012-01-01

15

Scales and sources of pH and dissolved oxygen variability in a shallow, upwelling-driven ecosystem  

NASA Astrophysics Data System (ADS)

In the coastal zone extreme variability in carbonate chemistry and oxygen is driven by fluctuations in temperature, salinity, air-sea gas exchange, mixing processes, and biology. This variability appears to be magnified in upwelling-driven ecosystems where low oxygen and low pH waters intrude into shallow depths. The oxygen and carbon chemistry signal can be further confounded by highly productive ecosystems such as kelp beds where photosynthesis and respiration consume and release significant amounts of dissolved inorganic carbon and oxygen. This variability poses a challenge for scientists assessing the impacts of climate change on nearshore ecosystems. We deployed physical & biogeochemical sensors in order to observe these processes in situ. The "SeapHOx" instruments used in this study consist of a modified Honeywell Durafet° ISFET pH sensor, an Aanderra Optode Oxygen sensor, and a SBE-37 conductivity, temperature, pressure sensor. The instruments were deployed on and around the La Jolla Kelp Forest at a variety of depths. Our goals were to (a) characterize the link between pH and oxygen and identify the magnitude of pH and oxygen variability over a range of intra-annual time scales and (b) investigate spatial patterns of pH and oxygen variability associated with depth, proximity to shore, and presence of kelp. Results thus far reveal a strong relationship between oxygen and pH. Temporal variability is greatest at the semidiurnal frequency where pH (at 7 m) can range up to 0.3 units and oxygen can change 50% over 6 h. Diurnal variability is a combination of the diurnal tidal component and diel cycles of production and respiration. Event-scale dynamics associated with upwelling can maintain pH and oxygen below 7.8 units and 200 ?mol kg-1, respectively, for multiple days. Frequent current reversals drive changes in the observed oxygen and pH variability. When alongshore currents are flowing southward, driven by upwelling-favorable winds, the magnitude of semidiurnal pH variability increases 5-fold relative to the magnitude of change during northward alongshore. Applying an empirically-determined alkalinity relationship, we conclude that changes in the carbonate chemistry parameters are largely driven by changes in total carbon. On small spatial scales, cross-shore differences exist in mean oxygen and pH but differences in alongshore mean oxygen and pH at a given depth appears to be negligible. Cross-shore differences can equate to a 0.05 pH unit decrease and 25 ?mol kg-1 oxygen decrease over 1 km at a given depth. Strong spatial variability in pH and oxygen conditions exist over vertical gradients in the kelp forest, with mean pH at the surface (7m) being 0.2 pH units greater than at the bottom (17m) and mean oxygen being 104 ?mol kg-1 greater. The observed range of pH (7.55-8.22) observed in this shallow environment during the course of a year is greater than open ocean predictions for a global mean pH reduction of 0.2-0.3 units predicted by the year 2100. These results suggest that organisms on exposed upwelling coasts may be adapted to a range of pH conditions and highlight the need for scientists to consider biological response to varying scales of pH change in order to develop more realistic predictions of the impacts of climate change for the coastal zone.

Tanner, C. A.; Martz, T.; Levin, L. A.

2011-12-01

16

Overcoming challenges in WAVE Bioreactors without feedback controls for pH and dissolved oxygen.  

PubMed

The biopharmaceutical industry is increasing its use of the WAVE Bioreactor for culturing cells. Although this disposable bioreactor can be equipped to provide real-time pH and dissolved oxygen (DO) monitoring and control, our goal was to develop a process for culturing CHO cells in this system without relying on pH and DO feedback controls. After identifying challenges in culturing cells without controlling for pH and DO in the WAVE Bioreactor, we characterized O(2) and CO(2) transfer in the system. From these cell-free studies, we identified rock rate and rock angle as key parameters affecting O(2) transfer. We also identified the concentration of CO(2) in the incoming gas and the rate of gas flow into the headspace as key parameters affecting CO(2) transfer--and therefore pH--in the disposable culture chamber. Using a full-factorial design to evaluate the rock rate, rock angle, and gas flow rate defined for this WAVE Bioreactor process, we found comparable cell growth and pH profiles in the ranges tested for these three parameters in two CHO cell lines. This process supported cell growth, and maintained pH and DO within our desired range--pH 6.8-7.2 and DO exceeding 20% of air saturation--for six CHO cell lines, and it also demonstrated comparable cell growth and viability with the stirred-tank bioreactor process with online pH and DO control. By eliminating the use of pH and DO probes, this process provides a simple and more cost-effective method for culturing cells in the WAVE Bioreactor. PMID:21987370

Yuk, Inn H; Baskar, Dinesh; Duffy, Philip H; Hsiung, Jenny; Leung, Susan; Lin, Andy A

2011-07-11

17

Sulfamethazine Sorption to Soil: Vegetative Management, pH, and Dissolved Organic Matter Effects.  

PubMed

Elucidating veterinary antibiotic interactions with soil is important for assessing and mitigating possible environmental hazards. The objectives of this study were to investigate the effects of vegetative management, soil properties, and >1000 Da dissolved organic matter (DOM) on sulfamethazine (SMZ) behavior in soil. Sorption experiments were performed over a range of SMZ concentrations (2.5-50 ?mol L) using samples from three soils (Armstrong, Huntington, and Menfro), each planted to one of three vegetation treatments: agroforestry buffers strips (ABS), grass buffer strips (GBS), and row crops (RC). Our results show that SMZ sorption isotherms are well fitted by the Freundlich isotherm model (log = 0.44-0.93; Freundlich nonlinearity parameter = 0.59-0.79). Further investigation of solid-to-solution distribution coefficients () demonstrated that vegetative management significantly ( < 0.05) influences SMZ sorption (ABS > GBS > RC). Multiple linear regression analyses indicated that organic carbon (OC) content, pH, and initial SMZ concentration were important properties controlling SMZ sorption. Study of the two most contrasting soils in our sample set revealed that increasing solution pH (pH 6.0-7.5) reduced SMZ sorption to the Armstrong GBS soil, but little pH effect was observed for the Huntington GBS soil containing 50% kaolinite in the clay fraction. The presence of DOM (150 mg L OC) had little significant effect on the Freundlich nonlinearity parameter; however, DOM slightly reduced SMZ values overall. Our results support the use of vegetative buffers to mitigate veterinary antibiotic loss from agroecosystems, provide guidance for properly managing vegetative buffer strips to increase SMZ sorption, and enhance understanding of SMZ sorption to soil. PMID:23673946

Chu, Bei; Goyne, Keith W; Anderson, Stephen H; Lin, Chung-Ho; Lerch, Robert N

18

Correlation between Electrical Conductivity and Total Dissolved Solids in Natural Waters  

Microsoft Academic Search

The study aims at establishing the correlation ratio between Total Dissolved Solids (TDS )and Electrical Conductivity ( EC ) for natural waters such as fresh water , sea water and tender coconut .The EC value can be obtained from in situ conductivity measurements since it is quick reliable and relatively of low cost . Twenty four fresh water , fifteen

S. Thirumalini; Kurian Joseph

2009-01-01

19

Specific conductance as an indicator of total dissolved solids in cold, dilute waters  

Microsoft Academic Search

Specific conductance is shown to bear a well-defined, linear relationship to total dissolved solids for cold, low ionic strength streams. Unless the water temperature is constant it is necessary first to correct the conductivity data to 25°C. This temperature correction may be taken as linear, even below 4°C, but not necessarily to be 2% per °C as is commonly used

A. G. THOMAS

1986-01-01

20

In situ measurements of dissolved oxygen, pH and redox potential of biocathode microenvironments using microelectrodes.  

PubMed

Biofilms are the core component of bioelectrochemical systems (BESs). To understand the polarization effects on biocathode performance of BES, dissolved oxygen concentrations, pHs and oxidation-reduction potentials of biofilm microenvironments were determined in situ. The results showed that lower polarization potentials resulted in the generation of larger currents and higher pH values, as well as the consumption of more oxygen. Oxidation-reduction potentials of biofilms were mainly affected by polarization potentials of the electrode rather than the concentration of dissolved oxygen or pH value, and its changes in the potentials corresponded to the electric field distribution of the electrode surface. The results demonstrated that a sufficient supply of dissolved oxygen and pH control of the biocathode are necessary to obtain optimal performance of BESs; a lower polarization potential endowed microorganisms with a higher electrochemical activity. PMID:23228452

Wang, Zejie; Deng, Huan; Chen, Lihui; Xiao, Yong; Zhao, Feng

2012-11-16

21

Electrochemistry of Dissolved Gases.  

National Technical Information Service (NTIS)

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

D. T. Sawyer

1965-01-01

22

Effects of initial cell density, pH and dissolved oxygen on bioreactor production of carrot somatic embryos  

Microsoft Academic Search

Effects of initial cell density, pH and dissolved oxygen on bioreactor production of somatic embryos of carrot (Daucus carota L.) were investigated using the cell suspension culture induced from hypocotyl segments in MS medium containing 0.5 mg\\/l 2,4-D. The best embryo production (140 torpedo-shaped embryos\\/ml-medium) was achieved with a medium pH of 5.2 at an initial cell density of 1

Jun-ichi Shigeta; Kenji Sato; Masahiro Mii

1996-01-01

23

Effect of pH and Dissolved Oxygen on the Cr(VI) Removal by Zero-Valent Iron  

Microsoft Academic Search

Chromate (Cr(VI)) is an industrial contaminant in groundwater and soil, and known as a carcinogen material. In this study, the effect of pH and dissolved oxygen (DO) for Cr(VI) removal by Zero-Valent Iron (ZVI) was investigated using batch and column experiments. Under oxic condition, 5 mg\\/L Cr(VI) in batch experiments was completely removed by 1 g ZVI at pH 4,

In-Ho Yoon; Kyoung-Woong Kim

24

pH, dissolved oxygen, and adsorption effects on metal removal in anaerobic bioreactors.  

PubMed

Anaerobic bioreactors were used to test the effect of the pH of influent on the removal efficiency of heavy metals from acid-rock drainage. Two studies used a near-neutral-pH, metal-laden influent to examine the heavy metal removal efficiency and hydraulic residence time requirements of the reactors. Another study used the more typical low-pH mine drainage influent. Experiments also were done to (i) test the effects of oxygen content of feed water on metal removal and (ii) the adsorptive capacity of the reactor organic substrate. Analysis of the results indicates that bacterial sulfate reduction may be a zero-order kinetic reaction relative to sulfate concentrations used in the experiments, and may be the factor that controls the metal mass removal efficiency in the anaerobic treatment systems. The sorptive capacities of the organic substrate used in the experiments had not been exhausted during the experiments as indicated by the loading rates of removal of metals exceeding the mass production rates of sulfide. Microbial sulfate reduction was less in the reactors receiving low-pH influent during experiments with short residence times. Sulfate-reducing bacteria may have been inhibited by high flows of low-pH water. Dissolved oxygen content of the feed waters had little effect on sulfate reduction and metal removal capacity. PMID:12931874

Willow, Mark A; Cohen, Ronald R H

25

Relationship between molecular orientation and conductivity of dielectric liquids dissolving restrained water  

Microsoft Academic Search

The state of water clusters dissolved in dielectric liquids has been studied using an IR spectrum method. Especially, the effect of water clusters on electrical conductivity is measured together with temperature dependence. In this experiment, dielectric liquids, such as nitrobenzene, benzonitrile and methylbenzoate, which are connected to an electron acceptor base, are used. From the results, it is found that

K. Ota; S. Itahashi; Y. Hayashi; M. Sone; H. Mitsui; Y. Murooka

1999-01-01

26

Dually Fluorescent Sensing of pH and Dissolved Oxygen Using a Membrane Made from Polymerizable Sensing Monomers  

PubMed Central

Using a thermal polymerization approach and polymerizable pH and oxygen sensing monomers with green and red emission spectra, respectively, new pH, oxygen, and their dual sensing membranes were prepared using poly(2-hydroxyethyl methacrylate)-co-poly(acrylamide) as a matrix. The sensors were grafted on acrylate-modified quartz glass and characterized under different pH values, oxygen concentrations, ion strengths, temperatures and cell culture media. The pH and oxygen sensors were excited using the same excitation wavelength and exhibited well-separated emission spectra. The pH-sensing films showed good response over the pH range 5.5 to 8.5, corresponding to pKa values in the biologically-relevant range between 6.9 and 7.1. The oxygen-sensing films exhibited linear Stern-Volmer quenching responses to dissolved oxygen. As the sensing membranes were prepared using thermally initiated polymerization of sensing moiety-containing monomers, no leaching of the sensors from the membranes to buffers or medium was observed. This advantageous characteristic accounts in part for the sensors' biocompatibility without apparent toxicity to HeLa cells after 40 hours incubation. The dual-sensing membrane was used to measure pH and dissolved oxygen simultaneously. The measured results correlated with the set-point values.

Tian, Yanqing; Shumway, Bradley R.; Youngbull, A. Cody; Li, Yongzhong; Jen, Alex K.-Y.; Johnson, Roger H.; Meldrum, Deirdre R.

2010-01-01

27

Influence of temperature, pH and dissolved oxygen on growth of Brevibacterium linens in a fermentor  

Microsoft Academic Search

The effects of temperature (20°, 25°, 30° C), pH (7.5, 8.0, 8.5) and dissolved oxygen (40%, 45%, 50%, 55%, 60% of concentration in air-saturated medium) on the growth of Brevibacterium linens were studied with cultures on sodium l-lactate and casamino acids in a regulated fermentor, using a factorial design methodology and an analysis of variance programme. The effect on growth

Marie-Hélène Famelart; André Kobilinsky; Christian Bouillanne; Michel J. Desmazeaud

1987-01-01

28

Comparison of Relationships Between pH, Dissolved Oxygen and Chlorophyll a for Aquaculture and Non-aquaculture Waters  

Microsoft Academic Search

The relationships between pH, dissolved oxygen (DO) and chlorophyll a in aquaculture and non-aquaculture waters are assessed in this paper. The research includes the evaluation of field and experimental\\u000a studies at the Panjiakou Reservoir (between Aug and Oct 2009) and the review of international data covering two decades. The\\u000a results indicated that typical eutrophic non-aquaculture water had mean concentrations of

Changjuan Zang; Suiliang Huang; Min Wu; Shenglan Du; Miklas Scholz; Feng Gao; Chao Lin; Yong Guo; Yu Dong

2011-01-01

29

The effects of dissolved organic matter and pH on sampling rates for polar organic chemical integrative samplers (POCIS)  

Microsoft Academic Search

The effect of solution pH and levels of dissolved organic matter (DOM) on the sampling rates for model pharmaceuticals and personal care products (PPCPs) and endocrine disrupting substance (EDS) by polar organic chemical integrative samplers (POCIS) was investigated in laboratory experiments. A commercially available POCIS configuration containing neutral Oasis HLB (hydrophilic–lipophilic balance) resin (i.e. pharmaceutical POCIS) and two POCIS configurations

Hongxia Li; Paul A. Helm; Gordon Paterson; Chris D. Metcalfe

2011-01-01

30

Sulfamethazine sorption to soil: vegetative management, pH, and dissolved organic matter effects  

Technology Transfer Automated Retrieval System (TEKTRAN)

Elucidating veterinary antibiotic (VA) interactions with soil is important for assessing and mitigating possible environmental hazards. Objectives of this study were to investigate the effects of vegetative management, soil physical and chemical properties, and manure-derived dissolved organic matte...

31

PhET Conductivity - Conducitivity, Energy Levels, Quantum Mechanics, Insulators  

NSDL National Science Digital Library

Experiment with conductivity in metals, plastics and photoconductors. See why metals conduct and plastics don't, and why some materials conduct only when you shine a flashlight on them. This simulation of a Conductivity is from the Physics Education Technology website of University of Colorado. Included are links to related topics and additional ideas and activities for teachers to use.

2008-10-22

32

High temporal and spatial variability of dissolved oxygen and pH in a nearshore California kelp forest  

NASA Astrophysics Data System (ADS)

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 ?mol 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 ?mol 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 ?mol 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 consequence, the exposure history of an organism is largely a function of its depth of occurrence within the kelp forest. These findings raise the possibility that the benthic communities along eastern boundary current systems are currently acclimatized and adapted to natural, variable, and low DO and pH. Future exposure of coastal California populations to low DO and pH may increase as upwelling intensifies and hypoxic boundaries shoal, compressing habitats and challenging the physiological capacity of intolerant species.

Frieder, C. A.; Nam, S. H.; Martz, T. R.; Levin, L. A.

2012-03-01

33

Influence of pH and dissolved Si on Fe isotope fractionation during dissimilatory microbial reduction of hematite  

NASA Astrophysics Data System (ADS)

Microbial dissimilatory iron reduction (DIR) has been identified as a mechanism for production of aqueous Fe(II) that has low 56Fe/ 54Fe ratios in modern and ancient suboxic environments that contain ferric oxides or hydroxides. These studies suggest that DIR could have played an important role in producing distinct Fe isotope compositions in Precambrian banded iron formations or other marine sedimentary rocks. However, the applicability of experimental studies of Fe isotope fractionation produced by DIR in geochemically simple systems to ancient marine environments remains unclear. Here we report Fe isotope fractionations produced during dissimilatory microbial reduction of hematite by Geobacter sulfurreducens in the presence and absence of dissolved Si at neutral and alkaline pH. Hematite reduction was significantly decreased by Si at alkaline (but not neutral) pH, presumably due to Si polymerization at the hematite surface. The presence of Si altered Fe isotope fractionation factors between aqueous Fe(II) or sorbed Fe(II) and reactive Fe(III), reflecting changes in bonding environment of the reactive Fe(III) component at the oxide surface. Despite these changes in isotopic fractionations, our results demonstrate that microbial Fe(III) oxide reduction produces Fe(II) with negative ? 56Fe values under conditions of variable pH and dissolved Si, similar to the large inventory of negative ? 56Fe in Neoarchean and Paleoproterozoic age marine sedimentary rocks.

Wu, Lingling; Beard, Brian L.; Roden, Eric E.; Johnson, Clark M.

2009-10-01

34

Microenvironments of pH in biofilms grown on dissolving silicate surfaces  

Microsoft Academic Search

Differences in pH between silicate–biofilm interfaces and bulk medium (?pH=pHinterface?pHbulk) were detectable with commercial microelectrodes in cultures grown in unbuffered medium (|?pH|=0.27–1.08) for an arthrobacter species, but were generally beneath detection (?pH<0.04) for a streptomyces species. Biofilm half-thicknesses developed by Arthrobacter ranged from 1.2 to 11.5 mm, and were highly variable even for replicates. In buffered medium, neither bacterium produced

Laura J. Liermann; Amy S. Barnes; Birgitta E. Kalinowski; Xiangyang Zhou; Susan L. Brantley

2000-01-01

35

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

National Technical Information Service (NTIS)

The purpose of this report is to describe specific conductance and dissolved-solids characteristics for two streams in the WLCI study area in Wyoming. Specifically, this report presents characteristics for the Green River near Green River, Wyoming, and fo...

M. L. Clark S. L. Davidson

2009-01-01

36

PALMERSTON NORTH, NEW ZEALAND The effects of IVF aspiration on the temperature, dissolved oxygen levels, and pH of follicular fluid  

Microsoft Academic Search

  \\u000a Purpose\\u000a : To investigate the effects of IVF aspiration on the temperature, pH, and dissolved oxygen of bovine follicular fluid.\\u000a \\u000a \\u000a Methods\\u000a : The temperature was monitored at various positions in an aspiration kit. Dissolved oxygen and pH were measured before and\\u000a after aspiration.\\u000a \\u000a \\u000a \\u000a \\u000a Results\\u000a : The temperature of follicular fluid dropped by 7.7?±?1.3°C upon aspiration. Dissolved oxygen levels rose

Gabe P. Redding; John E. Bronlund; Alan L. Hart

2006-01-01

37

The relationship of total dissolved solids measurements to bulk electrical conductivity in an aquifer contaminated with hydrocarbon  

Microsoft Academic Search

A recent conceptual model links higher bulk conductivities at hydrocarbon impacted sites to higher total dissolved solids (TDS) resulting from enhanced mineral weathering due to acids produced during biodegradation. In this study, we evaluated the above model by investigating the vertical distribution of bulk conductivity, TDS, and specific conductance in groundwater. The results showed higher TDS at contaminated locations consistent

Eliot A. Atekwana; Estella A. Atekwana; Rebecca S. Rowe; D. Dale Werkema; Franklyn D. Legall

2004-01-01

38

The relationship of total dissolved solids measurements to bulk electrical conductivity in an aquifer contaminated with hydrocarbon  

Microsoft Academic Search

A recent conceptual model links higher bulk conductivities at hydrocarbon impacted sites to higher total dissolved solids (TDS) resulting from enhanced mineral weathering due to acids produced during biodegradation. In this study, we evaluated the above model by investigating the vertical distribution of bulk conductivity, TDS, and specific conductance in groundwater. The results showed higher TDS at contaminated locations consistent

Eliot A. Atekwanaa; Estella A. Atekwanaa; Rebecca S. Roweb; D. Dale; Franklyn D. Legalld

39

The relationship of total dissolved solids measurements to bulk electrical conductivity in an aquifer contaminated with hydrocarbon  

Microsoft Academic Search

Abstract A recent conceptual model links higher bulk conductivities at hydrocarbon,impacted sites to higher total dissolved solids (TDS) resulting from enhanced mineral weathering due to acids produced during biodegradation. In this study, we evaluated the above model by investigating the vertical distribution of bulk conductivity, TDS, and specific conductance in groundwater. The results showed higher TDS at contaminated locations consistent

Eliot A. Atekwana; Estella A. Atekwana; Rebecca S. Rowe; D. Dale Werkema; Franklyn D. Legall

2004-01-01

40

Impact of shear stress and pH changes on floc size and removal of dissolved organic matter (DOM).  

PubMed

The impact of shear stress and increases in pH on the release of natural dissolved organic matter (DOM) from Fe-DOM and Al-DOM flocs was investigated for a high organic matter, low turbidity raw water by application of a dynamic extinction probe (DEP) and liquid chromatography organic carbon detection (LC-OCD). It was shown that high shear forces resulted in a breakage of Fe-DOM flocs. Re-growth took place during subsequent low shear phases. However, re-growth was limited. The flocs regained a size of about 50% of the size after initial coagulation. Cyclic shearing resulted in slower re-growth rates. A new insight was that when enough time was given, similar sizes of the re-grown flocs were regained. As shown by bulk DOC, only an insignificant release of DOM took place when flocs were exposed to shear. Increase in shear stress resulted in smaller flocs with higher specific outer surface area. However, DOM removal did not change. Thus, there was no increase in adsorption capacity due to floc breakage. Consequently, DOM must be adsorbed inside the amorphous flocs rather than on the outer surface. Also, as shear results in more compact flocs, compaction does not have an effect on DOM removal. A pH increase of 0.5, as it can happen during water treatment after coagulation, resulted in a release of DOM. Humic substances accounted for the largest proportion of total DOM released. The increase in pH did not affect floc size. Consequently, DOM removal is mainly governed by the dependence of DOM properties on pH with the final pH determining the degree of DOM removal and not the path on which this pH is reached. The physical properties of the flocs have no impact on DOM removal. PMID:23047054

Slavik, Irene; Müller, Susanne; Mokosch, Regina; Azongbilla, Joseph Abanga; Uhl, Wolfgang

2012-09-25

41

pH, ionic strength and dissolved organic matter alter aggregation of fullerene C60 nanoparticles suspensions in wastewater.  

PubMed

The rapid increase in the production and use of fullerene C(60) nanoparticles raise concerns about environmental risks and human health. Wastewater treatment plants are key barriers to their discharge into the environment. The aggregation behavior of aqueous suspensions of C(60) nanoparticles (nC(60)) could affect their transport, bioavailability, and removal during wastewater treatment. We tested the aggregation of nC(60) in wastewater at different values of pH, ionic strength, and dissolved organic matter (DOM). The nC(60) remained relatively stable in filtered wastewater under environmentally relevant conditions up to 24 h. But at pH 3 or at high ionic strength (>100 mM NaCl), the aggregate size increased greatly, reaching micrometer scale after only 1 h. However, the aggregation behavior varied among wastewater samples even at values of similar zeta potential, compared with that in filtered secondary effluent and aeration tank liquor, that in filtered primary effluent was obviously inhibited. This inhibition could be attributed to the steric stabilization due to the adsorption of DOM on nC(60) aggregate in addition to electrostatic stabilization. The aggregation results also suggest that membrane filtration could be improved by adjustments to pH. PMID:23177247

Yang, Yongkui; Nakada, Norihide; Nakajima, Ryoji; Yasojima, Makoto; Wang, Chao; Tanaka, Hiroaki

2012-11-02

42

Direct and indirect effects of increasing dissolved organic carbon levels on pH in lakes recovering from acidification  

NASA Astrophysics Data System (ADS)

In this study, we examine the impact of increasing concentrations of dissolved organic carbon (DOC) on the recovery from acidification for 66 lakes in Southern Sweden. The lakes are small, weakly buffered, and have all been affected by acidifying deposition. A majority of the lakes (˜75%) showed an increase in DOC concentrations between 1990 and 2008. The method used in this study was to model pH in 2008 from DOC, acid neutralizing capacity, pCO2 (partial carbon dioxide pressure), and Al speciation, using both the DOC observed in 2008 and the "unelevated" DOC of 1990. Furthermore, we consider the indirect effects of increasing DOC on acidity, i.e., the ancillary effects from DOC on pCO2, Al transport and speciation, and release of base cations (BCs). Our results indicate that the DOC increase in the latest decades has retarded the recovery from acidification by 0.13 pH units (median for all lakes) and by more than 1 unit for individual lakes. The effects of elevated pCO2 and BC concentrations accompanying the DOC increase compensated for each other for the average lake, whereas the effects of higher Al transport on pH were minor. The estimate of the amount of BCs released with the organic anions is however uncertain, and further studies on this topic are needed.

Erlandsson, Martin; Cory, Neil; KöHler, Stephan; Bishop, Kevin

2010-09-01

43

pH : a key control of the nature and distribution of dissolved organic matter and associated trace metals in soil  

NASA Astrophysics Data System (ADS)

Dissolved organic matter is ubiquitous at the Earth's surface and plays a prominent role in controlling metal speciation and mobility from soils to hydrosystems. Humic substances (HS) are usually considered to be the most reactive fraction of organic matter. Humic substances are relatively small and formed by chemically diverse organic molecules, bearing different functional groups that act as binding sites for cations and mineral surfaces. Among the different environmental physicochemical parameters controlling the metal speciation, pH is likely to be the most important one. Indeed, pH affect the dissociation of functional groups, and thus can influence the HS structure, their ability to complex metals, their solubility degree allowing the formation of aggregates at the mineral surface. In this context, soil/water interactions conducted through batch system experiments, were carried out with a wetland organic-rich soil to investigate the effect of pH on the release of dissolved organic carbon (DOC) and associated trace elements. The pH was regulated between 4 and 7.5 using an automatic pH stat titrator. Ultrafiltration experiments were performed to separate the dissolved organic pool following decreasing pore sizes (30 kDa, 5 kDa and 2 kDa with 1 Da = 1 g.mol-1). The pH increase induced a significant DOC release, especially in heavy organic molecules (size >5 kDa) with a high aromaticity (>30 %). These were probably humic acids (HA). This HA release influenced (i) directly the trace element concentrations in soil solution since HA were enriched in several trace elements such as Th, REE, Y, U, Cr and Cu; and (ii) indirectly by the breaking of clay-humic complexes releasing Fe- and Al-rich nanoparticles associated with V, Pb and Ti. By contrast, at acid pH, most HS were complexed onto mineral surfaces. They also sequestered iron nanoparticles. Therefore, at low pH, most part of DOC molecules had a size < 5 kDa and lower aromaticity. Thus, the DOC was mostly composed of simple organic compounds little complexing. Consequently, the soil solution was depleted in trace elements such as Th, REE, Y, U, Cr, Cu, Al, Fe, V, Pb and Ti, but also enriched in Ca, Sr, Ba, Mn, Mg, Co, Zn and in a lesser proportion in Rb, Li and Ni. The aromaticity in the fractions <5 kDa was higher than in the fractions <30 kDa or <0.2 µm. Complementary experiments were performed to understand the HS size distribution and aromaticity according to pH and ionic strength .The molecular size and shape of HS is usually explained by two concepts: (i) the macropolymeric structure with heavy organic molecules considered to be flexible linear polyelectrolytes and (ii) the supramolecular structure with an association of a complex mixture of different molecules held together by dispersive weak forces. Ours results supported the HA supramolecular structure at neutral or basic pH conditions. But, at acid pH, a disruption of the humic supramolecular associations involved the release of small organic molecules with a high aromaticity. Moreover, this aromaticity variation can be due also to the presence of fulvic acids in the fractions <5 kDa and a mixture of heavy organic molecules little complexing in the fractions >5 kDa. These latter molecules displayed a low aromaticity decreasing the global aromaticity of the fractions <30 kDa and <0.2 µm. To summarize, these new data demonstrated that the DOC and trace element concentrations of the soil solutions were strongly controlled by pH. This parameter influenced the nature and the size of the DOC as well as, the trace element concentrations in the soil solutions, with a decreasing contribution of HA when pH decreased. This pH dependence is a key issue of concern since local (human pressure) and/or global (climatic) warning result in pH water changes.

Pédrot, M.; Dia, A.; Davranche, M.

2009-04-01

44

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

PubMed

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

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

2011-06-28

45

The features of the correlation between the pH values and the dissolved oxygen at the Chistaya Balka test area in the Northern Caspian Sea  

NASA Astrophysics Data System (ADS)

Abnormally high pH values (up to 9 NBS units and over) were registered by different expeditions at the seaward edge of the Volga River delta. Within the report, the relationship of the pH values, the dissolved oxygen content, and the water temperature are considered using the equations of the thermodynamic theory of carbonate equilibrium. It is shown that the changes of the pH values are nonlinear relative to the content of oxygen. The nonlinearity is most pronounced at high values of the water saturation with oxygen (over 110-120%). A pH value over 9 may be reached in well heated waters at a dissolved oxygen content of 8-9 ml/l. The oxygen content as such is of course high but not excessive and might be caused by the high intensity of the production processes in the waters.

Makkaveev, P. N.

2009-08-01

46

Seasonal and diurnal variations of temperature, pH and dissolved oxygen in advanced integrated wastewater pond system ® treating tannery effluent  

Microsoft Academic Search

Seasonal and diurnal fluctuations of pH, dissolved oxygen (DO) and temperature were investigated in a pilot-scale advanced integrated wastewater pond system (AIWPS®) treating tannery effluent. The AIWPS® was comprised of advanced facultative pond (AFP), secondary facultative pond (SFP) and maturation pond (MP) all arranged in series. The variations of pH, DO and temperature in the SFP and MP followed the

I. Tadesse; F. B. Green; J. A. Puhakka

2004-01-01

47

Freeze\\/thaw and pH effects on freshwater dissolved organic matter fluorescence and absorbance properties from a number of UK locations  

Microsoft Academic Search

The UV-visible and fluorescence excitation-emission matrix spectrophotometric proper- ties of dissolved organic matter (DOM) were compared for the effects of both pH and freeze\\/ thaw on a wide range of freshwater DOM samples from the United Kingdom. It was observed that the spectrophotometric properties of our freshwater samples were sensitive to pH and that the recorded change varies with fluorescence

Robert G. M. Spencera; Lucy Boltond; Andy Bakere

48

Freeze\\/thaw and pH effects on freshwater dissolved organic matter fluorescence and absorbance properties from a number of UK locations  

Microsoft Academic Search

The UV–visible and fluorescence excitation–emission matrix spectrophotometric properties of dissolved organic matter (DOM) were compared for the effects of both pH and freeze\\/thaw on a wide range of freshwater DOM samples from the United Kingdom. It was observed that the spectrophotometric properties of our freshwater samples were sensitive to pH and that the recorded change varies with fluorescence and absorbance

Robert G. M. Spencer; Lucy Bolton; Andy Baker

2007-01-01

49

Relationship between pH and Medium Dissolved Solids in Terms of Growth and Metabolism of Lactobacilli and Saccharomyces cerevisiae during Ethanol Production  

Microsoft Academic Search

The specific growth rates of four species of lactobacilli decreased linearly with increases in the concentration of dissolved solids (sugars) in liquid growth medium. This was most likely due to the osmotic stress exerted by the sugars on the bacteria. The reduction in growth rates corresponded to decreased lactic acid production. Medium pH was another factor studied. As the medium

Neelakantam V. Narendranath; Ronan Power

2005-01-01

50

Effects of temperature, medium composition, pH, salt and dissolved oxygen on haemolysin and cytotoxin production by Aeromonas hydrophila isolated from oyster  

Microsoft Academic Search

The effects of temperature, medium composition, pH, salt content and dissolved oxygen (DO) on the production of haemolysin and cytotoxin by one strain of Aeromonas hydrophila isolated from oyster were investigated. Four media were tested: brain heart infusion broth (BHIB), casamino acid-yeast extract broth (CAYEB), nutrient broth (NB), and trypticase soy broth (TSB). BHIB was the best for toxin production

Guo-Jane Tsai; Fong-Cheng Tsai; Zwe-Ling Kong

1997-01-01

51

[Characteristics of precipitation pH and conductivity at Mt. Huang].  

PubMed

To understand the general characteristics of pH distribution and pollution in precipitation at Mt. Huang, statistical analyses were conducted for the routine measurements of pH and conductivity (K) at Mt. Huang during 2006-2011. The results showed that: (1) Over the period of study, the annual volume weighted mean (VWM) precipitation pH varied from 4.81 to 5.57, with precipitation acidity strengthening before 2009 and weakening thereafter. The precipitation acidity showed evident seasonal variations, with the VWM pH lowest in winter (4.78), and highest in summer (5.33). The occurrence frequency of acid rain was 46% , accounting for 45% of total rainfalls and with the most frequent pH falling into weak acid to neutral rain. (2) The annual VWM K varied from 16.91 to 27.84 microS x cm(-1), with no evident trend. As for ions pollution, the precipitation was relatively clean at Mt. Huang, with the most frequent K range being below 15 microS x cm(-1), followed by 15-25 microS x cm(-1). From February 2010 to December 2011, precipitation samples were collected on daily basis for ions analysis, as well as pH and K measurement in lab. Detailed comparisons were conducted between the two sets of pH and K, one set from field measurement and the other from lab measurement. The results indicated: (1) The lab measured pH (K) was highly correlated with the field pH (K); however, the lab pH tended to move towards neutral comparing with the corresponding field pH, and the shift range was closely correlated with the field pH and rainfall. The shift range of K from field to lab was highly correlated with the total ion concentration of precipitation. The field K showed evident negative correlation with the field pH with a correlation coefficient of -0.51. (2) When sampling with nylon-polyethylene bags, the statistics showed smaller bias between two sets of pH, with higher correlation coefficient between two sets of K. Furthermore, the lab K also showed evident negative correlation with the lab pH. Comparing with the observations at other alpine sites in central to eastern China, the natural precipitation at Mt. Huang was weaker in acidity and contains lower ion concentration. PMID:23914555

Shi, Chun-e; Deng, Xue-liang; Wu, Bi-wen; Hong, Jie; Zhang, Su; Yang, Yuan-jian

2013-05-01

52

Microbioreactor arrays with integrated mixers and fluid injectors for high-throughput experimentation with pH and dissolved oxygen control.  

PubMed

We have developed an integrated array of microbioreactors, with 100 microL working volume, comprising a peristaltic oxygenating mixer and microfluidic injectors. These integrated devices were fabricated in a single chip and can provide a high oxygen transfer rate (k(L)a approximately 0.1 s(-1)) without introducing bubbles, and closed loop control over dissolved oxygen and pH (+/-0.1). The system was capable of supporting eight simultaneous Escherichia coli fermentations to cell densities greater than 13 g-dcw L(-1) (1 cm OD(650 nm) > 40). This cell density was comparable to that achieved in a 4 litre reference fermentation, conducted with the same strain, in a bench scale stirred tank bioreactor and is more than four times higher than cell densities previously achieved in microbioreactors. Bubble free oxygenation permitted near real time optical density measurements which could be used to observe subtle changes in the growth rate and infer changes in the state of microbial genetic networks. Our system provides a platform for the study of the interaction of microbial populations with different environmental conditions, which has applications in basic science and industrial bioprocess development. We leverage the advantages of microfluidic integration to deliver a disposable, parallel bioreactor in a single chip, rather than robotically multiplexing independent bioreactors, which opens a new avenue for scaling small scale bioreactor arrays with the capabilities of bench scale stirred tank reactors. PMID:16929403

Lee, Harry L T; Boccazzi, Paolo; Ram, Rajeev J; Sinskey, Anthony J

2006-07-27

53

Lack of Correlation between Turnover of Low-Molecular-Weight Dissolved Organic Carbon and Differences in Microbial Community Composition or Growth across a Soil pH Gradient?†  

PubMed Central

We studied how soil pH (pHs 4 to 8) influenced the mineralization of low-molecular-weight (LMW)-dissolved organic carbon (DOC) compounds, and how this compared with differences in microbial community structure. The mineralization of LMW-DOC compounds was not systematically connected to differences in soil pH, consistent with soil respiration. In contrast, the microbial community compositions differed dramatically. This suggests that microbial community composition data will be of limited use in improving the predictive power of soil C models.

Rousk, Johannes; Brookes, Philip C.; Glanville, Helen C.; Jones, David L.

2011-01-01

54

The Combined Effects of Hardness, pH, and Dissolved Organic Carbon on the Chronic Toxicity of Zn to D. magna : Development of a Surface Response Model  

Microsoft Academic Search

The effect of changes in pH, hardness, and dissolved organic carbon (DOC) and the possible interactions among these parameters\\u000a on the chronic toxicity of zinc to D. magna were investigated. Based on a Central Composite Design, models were developed that can explain the observed variation in\\u000a EC10 and EC50 as a function of these toxicity modifying factors. All three parameters

D. G. Heijerick; C. R. Janssen; W. M. De Coen

2003-01-01

55

The Effects of Salinity, pH, and Dissolved Organic Matter on Acute Copper Toxicity to the Rotifer, Brachionus plicatilis (“L” Strain)  

Microsoft Academic Search

This paper presents data from original research for use in the development of a marine biotic ligand model and, ultimately,\\u000a copper criteria for the protection of estuarine and marine organisms and their uses. Ten 48-h static acute (unfed) copper\\u000a toxicity tests using the euryhaline rotifer Brachionus plicatilis (“L” strain) were performed to assess the effects of salinity, pH, and dissolved

W. R. Arnold; R. L. Diamond; D. S. Smith

2010-01-01

56

Ensuring PhD Development of Responsible Conduct of Research Behaviors: Who's Responsible?  

PubMed

The importance of public confidence in scientific findings and trust in scientists cannot be overstated. Thus, it becomes critical for the scientific community to focus on enhancing the strategies used to educate future scientists on ethical research behaviors. What we are lacking is knowledge on how faculty members shape and develop ethical research standards with their students. We are presenting the results of a survey with 3,500 research faculty members. We believe this is the first report on how faculty work with and educate their PhD students on basic research standards. Specifically, we wanted to determine whether individual faculty members, who are advisors or mentors, differ in how they implemented components of responsible conduct of research (RCR) with their PhD students. Mentors were more likely than advisors or supervisors to report working with all of their PhDs, who graduated in the last 5 years, on the 17 recognized critical components of RCR training and research skill development. We also found about half of the faculty members believe RCR is an institutional responsibility versus a faculty responsibility. Less than a quarter have had opportunities to participate in faculty training to be a better mentor, advisor, or research teacher, and about one third of faculty did not or could not remember whether they had guidelines related to their responsibilities to PhD students. We discuss the implications of our findings and focus on ways that PhD research mentoring can be enhanced. PMID:23686393

Titus, Sandra L; Ballou, Janice M

2013-05-18

57

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

USGS Publications Warehouse

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

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

2009-01-01

58

[Phenomena of pH instant increasing and its effect on dissolved inorganic carbon flux to sea in Yellow River estuary].  

PubMed

Dissolved inorganic carbon (DIC), pH, the partial pressure of CO (pCO2), total alkalinity (TA), dissolved oxygen saturation (DO), chlorophyll a (Chl-a), and NH4+, PO4(3-) were studied in mixing zone of Yellow River estuary from September 2004 to April 2006. The results indicate that pH value is higher than that of freshwater in low salinity area where DIC is non-conservative. NH4+, PO4(3-) sharply decreasing indicates that biogenic respiration is possibly inhibited in early mixing of freshwater and seawater, then pCO2, which is derived from biogenic respiration, swiftly decrease and lead to CaCO3 precipitation in low salinity area, and the pH value will simultaneously increase in this area. Instant increasing pH value can be used as index of CaCO3 precipitation in Yellow River estuary. According to dissolved matter mixing model in estuary, the observation of 1:1 removal of TA and DIC provides just evidence that DIC removal we observed in the field is a result of CaCO3 precipitation. The process can clean 10% (1.21 x 10(5) tons) DIC which is transported by freshwater both in dry and wet weathers, and the annually effective DIC flux to sea of Yellow River is 10.86 x 10(5) tons. Ten percent of CO2 (2.24 x 10(5) t) which is absorbed by chemical weathering process in drainage basin will release to atmosphere in Yellow River estuary. PMID:17674725

Zhang, Xiang-Shang; Zhang, Long-Jun

2007-06-01

59

Effect of pH on the bioaccumulation of low level, dissolved methylmercury by rainbow trout (Oncorhynchus mykiss)  

Microsoft Academic Search

An inverse relationship has been observed between pH and McHg concentration in freshwater fish. Many hypotheses exist regarding\\u000a the mechanisms which lead to elevated levels of organic Hg in fish from low pH lakes. To determine if pH has a direct effect\\u000a on the rate of McHg bioaccumulation in fish, rainbow trout fingerlings (Oncorhynchus mykiss) were exposed to a low

R. A. Ponce; N. S. Bloom

1991-01-01

60

Intracellular pH controls cell membrane Na+ and K+ conductances and transport in frog skin epithelium  

Microsoft Academic Search

We determined the effects of intracellular respiratory and metabolic acid or alkali loads, at constant or variable external pH, on the apical membrane Na+-specific conductance (g~) and basolateral membrane conductance (gO, princi- pally due to K +, in the short-circuited isolated frog skin epithelium. Conductances were determined from the current-voltage relations of the amiloride-inhibitable cellular current pathway, and intracellular pH

BRIAN J. HARVEY; S. RANDALL THOMAS; JORDI EHRENFELD

1988-01-01

61

Effects of pH and dissolved CO2 level on simultaneous production of 2,3-butanediol and succinic acid using Klebsiella pneumoniae.  

PubMed

The influences of pH and dissolved CO2 level on the regulation of growth and formation of catabolic end products have been investigated in Klebsiella pneumoniae. With increasing CO2 levels, there were no apparent changes in 2,3-butanediol production but succinic acid productions were enhanced significantly. A novel strategy for co-production of 2,3-butanediol and succinic acid using K. pneumoniae was developed by controlling pH and dissolved CO2 concentration in fermentation medium. Under the optimum condition, maximal 77.1 g l(-1) 2,3-butanediol and 28.7 g l(-1) succinic acid were obtained after 60 h of fed-batch fermentation, giving a 2,3-butanediol+succinic acid yield of 1.03 mol mol(-1) glucose. This type of fermentation producing two commercial interests at the same fermentation process might be considered for a promising biological production process which will decrease the production cost by sharing the operation and recovery cost. PMID:23010216

Cheng, Ke-Ke; Wu, Jing; Wang, Gen-Yu; Li, Wen-Ying; Feng, Jie; Zhang, Jian-An

2012-09-05

62

Steady-state diagenetic model for dissolved carbonate species and pH in the pore waters of oxic and suboxic sediments  

SciTech Connect

An open-system diagenetic (transport) model is presented which accounts for the concurrent behavior of all the dissolved carbonate species as well as hydrogen and hydroxyl ions in the pore waters of marine sediments during the oxic and suboxic decay of organic-matter. The model includes interconversion between the dissolved carbonate species due to associationdissociation reactions as well as production by organic decay and CaCO/sub 3/ dissolution. The existence of rapid associationdissociation reactions has important consequences. First, the transport of a dissolved carbonate species is facilitated, because it can react and diffuse as another carbonate species. This action modifies the concentration profiles which would be expected without interconversion. As a consequence, the rate of CaCO/sub 3/ dissolution is increased because it is more difficult for CO/sub 3//sup =/ to reach and maintain the saturation concentration. Finally, CO/sub 2/(aq) and HCO/sub 3//sup -/ produced by decay affect the concentration of CO/sub 3//sup =/ and, therefore, the saturation state of pore waters with respect to carbonate minerals. The model is applied to the carbonate alkalinity and pH data from the Guatemala Basin and MANOP Site C. The model reproduces the sharp near-surface minimum in pH, observed at the Guatemala Basin sites; however, the carbonate alkalinity increase is underpredicted. This model result implies that there is an additional source of HCO/sub 3//sup -/ that is not presently recognized, probably in the form of sulfate reduction at depth.

Boudreau, B.P.

1987-07-01

63

The effect of dissolved organic matter (DOM) on sodium transport and nitrogenous waste excretion of the freshwater cladoceran (Daphnia magna) at circumneutral and low pH.  

PubMed

Dissolved organic matter (DOM), a heterogeneous substance found in all natural waters, has many documented abiotic roles, but recently, several possible direct influences of DOM on organism physiology have been reported. However, most studies have been carried out with a limited number of natural DOM isolates or were restricted to the use of commercial or artificial humic substances. We therefore employed three previously characterized, chemically-distinct natural DOMs, as well as a commercially available humic acid (Aldrich, AHA), at circumneutral (7-8) and acidic pH (~5), to examine DOM effects on whole-body Na(+) concentration, unidirectional influx and efflux rates of Na(+), and ammonia and urea excretion rates in Daphnia magna. Whole-body Na(+) concentration, Na(+) influx, and Na(+) efflux rates were all unaffected regardless of pH, suggesting no influence of the various natural DOMs on active uptake and passive diffusion of Na(+) in this organism. Ammonia and urea excretion rates were both increased by low pH. Ammonia excretion rates were reduced at circumneutral pH by the most highly colored, allochthonous DOM, and at low pH by all three natural DOMs, as well as by the commercial AHA. Urea excretion rates were not influenced by the presence of the various DOMs in circumneutral solutions, but were attenuated by the presence of two allochthonous DOM sources (isolated from Bannister Lake and Luther Marsh) at acidic pH. The observed reductions may be attributed partially to the higher buffering capacities of natural DOM sources, as well as their ability to interact with biological membranes as estimated by a new measure calculated from their acid-base titration characteristics, the Proton Binding Index (PBI). PMID:24028854

Al-Reasi, Hassan A; Yusuf, Usman; Smith, D Scott; Wood, Chris M

2013-09-10

64

Effects of Dissolved Sulfide, pH, and Temperature on Growth and Survival of Marine Hyperthermophilic Archaea  

PubMed Central

The ability of metabolically diverse hyperthermophilic archaea to withstand high temperatures, low pHs, high sulfide concentrations, and the absence of carbon and energy sources was investigated. Close relatives of our study organisms, Methanocaldococcus jannaschii, Archaeoglobus profundus, Thermococcus fumicolans, and Pyrococcus sp. strain GB-D, are commonly found in hydrothermal vent chimney walls and hot sediments and possibly deeper in the subsurface, where highly dynamic hydrothermal flow patterns and steep chemical and temperature gradients provide an ever-changing mosaic of microhabitats. These organisms (with the possible exception of Pyrococcus strain GB-D) tolerated greater extremes of low pH, high sulfide concentration, and high temperature when actively growing and metabolizing than when starved of carbon sources and electron donors/acceptors. Therefore these organisms must be actively metabolizing in the hydrothermal vent chimneys, sediments, and subsurface in order to withstand at least 24 h of exposure to extremes of pH, sulfide, and temperature that occur in these environments.

Lloyd, Karen G.; Edgcomb, Virginia P.; Molyneaux, Stephen J.; Boer, Simone; Wirsen, Carl O.; Atkins, Michael S.; Teske, Andreas

2005-01-01

65

Carbon dioxide addition to microbial fuel cell cathodes maintains sustainable catholyte pH and improves anolyte pH, alkalinity, and conductivity.  

PubMed

Bioelectrochemical system (BES) pH imbalances develop due to anodic proton-generating oxidation reactions and cathodic hydroxide-ion-generating reduction reactions. Until now, workers added unsustainable buffers to reduce the pH difference between the anode and cathode because the pH imbalance contributes to BES potential losses and, therefore, power losses. Here, we report that adding carbon dioxide (CO(2)) gas to the cathode, which creates a CO(2)/bicarbonate buffered catholyte system, can diminish microbial fuel cell (MFC) pH imbalances in contrast to the CO(2)/carbonate buffered catholyte system by Torres, Lee, and Rittmann [Environ. Sci. Technol. 2008, 42, 8773]. We operated an air-cathode and liquid-cathode MFC side-by-side. For the air-cathode MFC, CO(2) addition resulted in a stable catholyte film pH of 6.61 +/- 0.12 and a 152% increase in steady-state power density. By adding CO(2) to the liquid-cathode system, we sustained a steady catholyte pH (pH = 5.94 +/- 0.02) and a low pH imbalance (DeltapH = 0.65 +/- 0.18) over a 2-week period without external salt buffer addition. By migrating bicarbonate ions from the cathode to the anode (with an anion-exchange membrane), we increased the anolyte pH (DeltapH = 0.39 +/- 0.31), total alkalinity (494 +/- 6 to 582 +/- 6 as mg CaCO(3)/L), and conductivity (1.53 +/- 0.49 to 2.16 +/- 0.03 mS/cm) relative to the feed properties. We also verified with a phosphate-buffered MFC that our reaction rates were limited mainly by the reactor configuration rather than limitations due to the bicarbonate buffer. PMID:20178380

Fornero, Jeffrey J; Rosenbaum, Miriam; Cotta, Michael A; Angenent, Largus T

2010-04-01

66

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

Microsoft Academic Search

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

Alan M. Shiller

1997-01-01

67

Spatial and temporal patterns of temperature, alkalinity, dissolved oxygen and conductivity in an oligo-mesotrophic, deep-storage reservoir in central Texas  

Microsoft Academic Search

Impoundment behavior was determined for alkalinity, temperature, dissolved oxygen, and conductivity from stations located along the length of a bottom-draining, oligo-mesotrophic, hardwater, deep-storage reservoir located in central Texas. The epilimnion deepened the length of the reservoir throughout the summer as a result of drawdown. Bicarbonate alkalinity and conductivity exhibited both longitudinal and vertical stratification. Alkalinity and conductivity in the epilimnion

H. H. Hannan; I. R. Fuchs; D. C. Whitenberg

1979-01-01

68

Effect of temperature, pH, dissolved oxygen, and hydrolysate on the formation of triple light chain antibodies in cell culture.  

PubMed

THIOMABs are recombinant antibodies with reactive cysteine residues used for forming THIOMAB-drug conjugates (TDCs). We recently reported a new impurity associated with THIOMABs: one of the engineered cysteines forms a disulfide bond with an extra light chain (LC) to generate a triple light chain antibody (3LC). In our previous investigations, increased LC expression increased 3LC levels, whereas increased glutathione (GSH) production decreased 3LC levels. In this work, on three stably transfected CHO cell lines, we investigated the effects of temperature, pH, dissolved oxygen (DO), and hydrolysate on 3LC formation during THIOMAB fed-batch cell culture production. Although pH between 6.8 and 7.0 had no significant impact on 3LC formation, temperature at 35°C instead of 33 or 31°C generated the lowest 3LC values for two cell lines. The decreased 3LC level correlated with increased GSH production. We implemented a 35°C temperature process for large-scale (2,000 L) production of a THIOMAB. This process reduced 3LC levels by ?50% compared with a 33°C temperature process. By contrast, DO and hydrolysate had modest effect on 3LC levels for the model cell line studied. Overall, we did not find significant changes in LC expression under the conditions tested, whereas changes in GSH production were more evident. By investigating the impact of bioreactor process and medium conditions on 3LC levels, we identified strategies that reduced 3LC levels. PMID:20568280

Gomez, Natalia; Ouyang, Jun; Nguyen, Mary D H; Vinson, Abigail R; Lin, Andy A; Yuk, Inn H

69

Root-induced changes in pH and dissolved organic matter binding capacity affect copper dynamic speciation in the rhizosphere  

NASA Astrophysics Data System (ADS)

Due to only few experimental evidences, the importance of root-induced alteration of metal dynamic speciation in the rhizosphere in the determination of metal bioavailability to plants is still a matter for debate. The present study thus investigated how root-induced changes in pH and dissolved organic matters (DOM) altered copper (Cu) dynamic speciation in the rhizosphere of durum wheat (Triticum turgidum durum L.). Plants were exposed to a Cu-contaminated soil previously alkalised by liming to cover soil pH values ranging from 4.8 to 7.5. A range of analytical techniques was deployed on soil exposed (i.e. in the rhizosphere) or not (i.e. in the bulk soil) to plant roots, including the measurement and the modelling (using the Humic Ion-Binding Model VI) of Cu2+ activity, the measurement of labile Cu concentration and Cu lability by Differential Pulse Anodic Stripping Voltammetry (DPASV) and Diffusive Gradients in Thin films (DGT). Due to root-induced alkalisation, pH reached about 7.3 in the rhizosphere whatever the initial bulk soil pH. Compared to the most acidic bulk soil (pH ? 4.8), Cu2+ activity decreased by three orders of magnitude in the rhizosphere while DPASV-Cu concentration decreased by 6-fold. DOM became the key driver of Cu dynamic speciation in the rhizosphere, where roots induced up to an order of magnitude increase in DOM concentration compared to bulk soils. This resulted in an increase in labile-Cu (both DPASV and DGT) concentrations, in spite of a decrease in Cu2+ activity. Model VI calculations supported a decrease in DOM binding capacity towards Cu in the rhizosphere. DPASV measurements unequivocally demonstrated that the increase in Cu lability in the rhizosphere solution can be attributed to a greater lability of organically-bound Cu. Collectively, our data introduce a consistent picture of root-induced changes of Cu dynamic speciation in the rhizosphere that were notably related to substantial alterations of DOM binding capacity.

Bravin, Matthieu N.; Garnier, Cédric; Lenoble, Véronique; Gérard, Frédéric; Dudal, Yves; Hinsinger, Philippe

2012-05-01

70

Nanoceria facilitates the synthesis of poly(o-phenylene diamine) with pH tunable morphology conductivity and photoluminiscent properties  

PubMed Central

Poly(ortho-phenylene diamine) synthesis enabled by the catalytic oxidase-like activity of nanoceria was accomplished for applications in electronics, medicine and biotechnology. The polymer shows unique morphology, conductivity and photoluminescence based on pH of the solution during synthesis. The various poly(ortho-phenylene diamine) preparations were characterized by UV-visible spectroscopy, scanning electron microscopy, fluorescence spectroscopy, fluorescence microscopy, high pressure liquid chromatography and cyclic voltammetry. Poly(ortho-phenylene diamine) synthesized at pH 1.0 by nanoceria was selected to be extensively studied based on the fast synthetic kinetics and the resulting conductive and photoluminiscent properties for various applications.

Asati, Atul; Lehmkuhl, David; Diaz, Diego; Perez, J. Manuel

2012-01-01

71

PhRMA Survey on the Conduct of First-in-Human Clinical Trials Under Exploratory Investigational New Drug Applications  

Microsoft Academic Search

The FDA guidance on exploratory IND studies is intended to enable sponsors to move ahead more efficiently with the development of promising candidates. A survey of PhRMA member companies was conducted in 2007 to obtain a cross-sectional industry perspective on the current and future utility of exploratory IND studies. About 56% of survey responders (9 companies of 16 survey responders)

Adel H. Karara; Timi Edeki; James McLeod; Alfred P. Tonelli; John A. Wagner

2010-01-01

72

Methods for Conducting Snail (Aplexa hypnorum) Embryo through Adult Exposures: Effects of Cadmium and Reduced pH Levels.  

National Technical Information Service (NTIS)

Two separate embryo through adult exposures were conducted with cadmium and with reduced pH levels to validate various test methodologies and to determine the feasibility of testing and ease of handling the freshwater snail (Aplexa hypnorum) in a test sys...

G. W. Holcombe G. L. Phipps J. W. Marier

1984-01-01

73

Methods for conducting snail ( Aplexa hypnorum ) embryo through adult exposures: Effects of cadmium and reduced pH levels  

Microsoft Academic Search

Two separate embryo through adult exposures were conducted with cadmium and with reduced pH levels to validate various test methodologies and to determine the feasibility of testing and ease of handling the freshwater snail (Aplexa hypnorum) in a test system designed for fish bioassays. Exposure of snails from embryos through adult reproductive maturity to cadmium chloride produced delayed hatch, reductions

Gary W. Holcombe; Gary L. Phipps; John W. Marier

1984-01-01

74

Effect of pH, ionic strength, dissolved organic carbon, time, and particle size on metals release from mine drainage impacted streambed sediments.  

PubMed

Acid-mine drainage (AMD) input to a stream typically results in the stream having a reduced pH, increased concentrations of metals and salts, and decreased biological productivity. Removal and/or treatment of these AMD sources is desired to return the impacted stream(s) to initial conditions, or at least to conditions suitable for restoration of the aquatic ecosystem. Some expected changes in the water chemistry of the stream following removal of AMD input include an increase in pH, a decrease in ionic strength, and an increase in dissolved organic carbon (DOC) concentrations from increased biological activity in the absence of toxic metals concentrations. These changes in water chemistry may cause the existing contaminated bed sediments to become a source of metals to the stream water. Streambed sediments, collected from North Fork Clear Creek (NFCC), Colorado, currently impacted by AMD, were assessed for the effects of pH, ionic strength, DOC concentration, time, and particle size on metals release using a factorial design. The design included two levels for each chemical parameter (ionic strength = 40 and 80% lower than ambient; pH = 6 and 8; and DOC = 1 and 3 mg/l higher than ambient), ten sampling times (from zero to 48 h), and two size fractions of sediments (63 microm < or = x < 2 mm and < 63 microm). Greater concentrations of metals were released from the smaller sized sediments compared with the larger, with the exception of Cu. A mild acid digestion (0.6M HCl) evaluated the amount of each metal that could be removed easily from each of the sediment size fractions. Release of all metals over all time points, treatments, and from both sediment sizes was less than 1% of the extractable concentrations, with the exception of Mn, which ranged from 4 to 7% from the smaller sized sediment. Greater percentages of the 0.6M HCl-extractable concentrations of Cu, Fe, and Zn were released from the larger sized sediment, while this was true for release of Cd and Mn from the smaller sized sediment. Thus, at least for Cd and Mn, the observed higher concentrations released from the smaller sized sediment with each treatment solution is not simply a function of these particles having higher concentrations available for release, but that these metals also are more readily released from the smaller sediment particles versus the larger. DOC concentration strongly influenced the release of Cu; ionic strength strongly influenced the release of Cd, Mn, and Zn; and interaction effects were observed with the release of Cu, Mn, and Zn from the larger size fraction and with the release of Zn from the smaller size fraction. Overall, results suggest that the expected changes in water chemistry following removal/treatment of the AMD sources would result in a release of metals from the existing sediments, with a greater effect on the release of Cu and Fe, than on the release of Cd, Mn, and Zn. PMID:19110291

Butler, Barbara A

2008-12-24

75

Chloride-thiocyanate interactions in frog muscle anion-conducting channels at pH 5  

Microsoft Academic Search

Bi-ionic membrane potential measurements and three-microelectrode voltage clamp experiments have been performed on surface fibres of Xenopus laevis sartorius muscle at various mole fractions of SCN- in Cl- in the perfusate, at pH 5. Potassium was replaced in the test solutions by rubidium and\\/or tetraethylammonium and when the mole fraction of anions was changed the measured membrane potential changed to

P. C. Vaughan

1987-01-01

76

Defining Dissolving  

NSDL National Science Digital Library

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

Kessler, James H.; Galvan, Patricia M.

2007-01-01

77

The pH value and electrical conductivity of atmospheric environment from ice cores in the Tianshan Mountains  

Microsoft Academic Search

Electrical Conductivity Measurement (ECM) from ice core is a representative index for atmospheric environmental change. The\\u000a pH value and ECM from three shallow ice cores (each 3.85 m, 231 ice samples total) on Glacier No.1 at the headwater of Urumqi\\u000a River, Glacier No.48 in Kuitun area, and Miaoergou Glacier in Hami area in the eastern Tianshan Mountains, western China,\\u000a were

Zhiwen Dong; Mingjun Zhang; Zhongqin Li; Feiteng Wang; Wenbin Wang

2009-01-01

78

Changes in conductivity, alkalinity, calcium, and pH during a 50-year period in selected northern Wisconsin lakes  

SciTech Connect

Between 1925 and 1941 extensive water quality measurements were made on over 600 northern Wisconsin lakes, providing a benchmark against which comparisons can be made if the modern equivalent measurements can be determined. Of these 149 lakes were sampled from 1979 to 1983. Data on conductivity, alkalinity, calcium, and hydrogen ion (pH) are available for these lakes from 1925 to 1931. The historical methyl orange alkalinity data were adjusted to be comparable to the recent Gran alkalinity data by subtracting 57 micromol/L from the historical measurements. The colorimetric historical pH measurements were adjusted to be comparable to recent potentiometric measurements by a regression model. No adjustments were made to the historical calcium or conductivity measurements. Comparisons of adjusted historical data with recent data show a significant increase in the means of all four variables. The largest increases in all four variables show an association with increases in land use development on the lake perimeters. Statistically significant changes in alkalinity are observed, with 28 lakes increasing and 11 decreasing, compared with 110 lakes showing no change. Possible explanations for chemical changes in those lakes that have experienced little change in land use are discussed. For the lakes in northern Wisconsin which may have been affected by airborne pollutants, it is likely that these effects had their beginning before initiation of the historical lake survey.

Eilers, J.M.; Glass, G.E.; Pollack, A.K.; Sorensen, J.A.

1989-01-01

79

pH : a key control of the nature and distribution of dissolved organic matter and associated trace metals in soil  

Microsoft Academic Search

Dissolved organic matter is ubiquitous at the Earth's surface and plays a prominent role in controlling metal speciation and mobility from soils to hydrosystems. Humic substances (HS) are usually considered to be the most reactive fraction of organic matter. Humic substances are relatively small and formed by chemically diverse organic molecules, bearing different functional groups that act as binding sites

M. Pédrot; A. Dia; M. Davranche

2009-01-01

80

In situ deployment of voltammetric, potentiometric, and amperometric microelectrodes from a ROV to determine dissolved Oâ, Mn, Fe, S(-2), and pH in porewaters  

Microsoft Academic Search

Solid-state microelectrodes have been used in situ in Raritan Bay, NJ to measure pore water profiles of dissolved Oâ, Mn, Fe, and sulfide at (sub)millimeter resolution by voltammetric techniques. The voltammetric sensor was positioned with microprofiling instrumentation mounted on a small remote operated vehicle (ROV). This instrumentation and the sensor were controlled and monitored in real time from a research

George W. Luther; Clare E. Reimers; Donald B. Nuzzio; David Lovalvo

1999-01-01

81

Stability of chemical parameters of tissue culture medium (pH, osmolarity, electrical conductivity) as a function of time of growth  

Microsoft Academic Search

Changes in medium pH, osmolarity (OS), and electrical conductivity (EC) were studied as a function of time in Murashige and Skoog (MS) liquid proliferation and rooting medium. Microshoots of wild pear (Pyrus syriaca), bitter almond, and ‘Spunta’ potato were targeted. Results indicated an acidic drift in pH in the different species on both proliferation and rooting medium. The EC was

R. A. Shibli; M. J. Mohammad; M. M. Ajlouni; M. A. Shatnawi; A. F. Obeidat

1999-01-01

82

An Evaluation of In-Situ Measurements of Water Temperature, Specific Conductance, and pH in Low Ionic Strength Streams  

Microsoft Academic Search

The performance of minimonitors used by the U.S. Geological Survey for continuous measurement of water temperature, specific conductance, and pH in four low ionic strength streams in the Catskill Mountains of New York was evaluated through a calculation of their bias, precision, and accuracy and by comparison with laboratory measurements of specific conductance and pH on samples collected concurrently. Results

Anthony J. Ranalli

1998-01-01

83

EFFECT OF pH, IONIC STRENGTH, DISSOLVED ORGANIC CARBON, TIME, AND PARTICLE SIZE ON METALS RELEASE FROM MINE DRAINAGE IMPACTED STREAMBED SEDIMENTS  

EPA Science Inventory

Acid-mine drainage (AMD) input to a stream typically results in the stream having a reduced pH, increased concentrations of metals and salts, and decreased biological productivity. Removal and/or treatment of these AMD sources is desired to return the impacted stream(s) to initi...

84

Determination of the total dissolved sulphide in the pH range 3-11.4 with sulphide selective ISE and Ag/A92S electrodes.  

PubMed

An electrochemical method for the determination of the total sulphide concentration of sewage water samples has been studied using a potentiometric cell containing either a sulphide ion selective ISE-glass electrode pair or a Ag/Ag(2)S electrode-glass electrode system. The performance of the two sulphide ion sensors was investigated and compared in both acidic and basic pH ranges. It was proved that the cell potential can be made directly proportional to the logarithm of the total sulphide concentration when both the pH < lg K(2) - 1.5 condition (acidic range) and also when the lg K(2) + 1.5 < pH < lg K(1) - 1.5 condition prevails in the system (alkaline range); where K(1) and K(2) are the first and second protonation constants of the sulphide ion, respectively. A suitable calibration method for a wide range of sulphide concentration is also presented for both ranges of the pH scale. The overall performance of the measuring system was tested using model solutions and real waste water samples. PMID:18966059

Schmidt, E; Marton, A; Hlavay, J

1994-07-01

85

Modulation of cystic fibrosis transmembrane conductance regulator (CFTR) activity and genistein binding by cytosolic pH.  

PubMed

Potentiators are molecules that increase the activity of the cystic fibrosis transmembrane conductance regulator (CFTR). Some potentiators can also inhibit CFTR at higher concentrations. The activating binding site is thought to be located at the interface of the dimer formed by the two nucleotide-binding domains. We have hypothesized that if binding of potentiators involves titratable residues forming salt bridges, then modifications of cytosolic pH (pH(i)) would alter the binding affinity. Here, we analyzed the effect of pH(i) on CFTR activation and on the binding of genistein, a well known CFTR potentiator. We found that pH(i) does modify CFTR maximum current (I(m)) and half-activation concentration (K(d)): I(m) = 127.7, 185.5, and 231.8 ?A/cm(2) and K(d) = 32.7, 56.6 and 71.9 ?m at pH 6, 7.35, and 8, respectively. We also found that the genistein apparent dissociation constant for activation (K(a)) increased at alkaline pH(i), near cysteine pK (K(a) = 1.83, 1.81 and 4.99 ?m at pH(i) 6, 7.35, and 8, respectively), suggesting the involvement of cysteines in the binding site. Mutations of cysteine residues predicted to be within (Cys-491) or outside (Cys-1344) the potentiator-binding site showed that Cys-491 is responsible for the sensitivity of potentiator binding to alkaline pH(i). Effects of pH(i) on inhibition by high genistein doses were also analyzed. Our results extend previous data about multiple effects of pH(i) on CFTR activity and demonstrate that binding of potentiators involves salt bridge formation with amino acids of nucleotide-binding domain 1. PMID:20974851

Melani, Raffaella; Tomati, Valeria; Galietta, Luis J V; Zegarra-Moran, Olga

2010-10-25

86

Modulation of Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Activity and Genistein Binding by Cytosolic pH*  

PubMed Central

Potentiators are molecules that increase the activity of the cystic fibrosis transmembrane conductance regulator (CFTR). Some potentiators can also inhibit CFTR at higher concentrations. The activating binding site is thought to be located at the interface of the dimer formed by the two nucleotide-binding domains. We have hypothesized that if binding of potentiators involves titratable residues forming salt bridges, then modifications of cytosolic pH (pHi) would alter the binding affinity. Here, we analyzed the effect of pHi on CFTR activation and on the binding of genistein, a well known CFTR potentiator. We found that pHi does modify CFTR maximum current (Im) and half-activation concentration (Kd): Im = 127.7, 185.5, and 231.8 ?A/cm2 and Kd = 32.7, 56.6 and 71.9 ?m at pH 6, 7.35, and 8, respectively. We also found that the genistein apparent dissociation constant for activation (Ka) increased at alkaline pHi, near cysteine pK (Ka = 1.83, 1.81 and 4.99 ?m at pHi 6, 7.35, and 8, respectively), suggesting the involvement of cysteines in the binding site. Mutations of cysteine residues predicted to be within (Cys-491) or outside (Cys-1344) the potentiator-binding site showed that Cys-491 is responsible for the sensitivity of potentiator binding to alkaline pHi. Effects of pHi on inhibition by high genistein doses were also analyzed. Our results extend previous data about multiple effects of pHi on CFTR activity and demonstrate that binding of potentiators involves salt bridge formation with amino acids of nucleotide-binding domain 1.

Melani, Raffaella; Tomati, Valeria; Galietta, Luis J. V.; Zegarra-Moran, Olga

2010-01-01

87

How to Measure Dissolved Oxygen  

NSDL National Science Digital Library

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

Ecology, Washington S.

88

Effect of overlying water pH, dissolved oxygen, salinity and sediment disturbances on metal release and sequestration from metal contaminated marine sediments  

Microsoft Academic Search

Experiments were undertaken to examine the key variables affecting metal release and sequestration processes in marine sediments with metal concentrations in sediments reaching up to 86, 240, 700, and 3000mgkg?1 (dry weight) for Cd, Cu, Pb and Zn, respectively. The metal release and sequestration rates were affected to a much greater extent by changes in overlying water pH (5.5–8.0) and

Clare A. Atkinson; Dianne F. Jolley; Stuart L. Simpson

2007-01-01

89

Role of Na+\\/H+ exchange in the control of intracellular pH and cell membrane conductances in frog skin epithelium  

Microsoft Academic Search

Ion-sensitive microelectrodes and current-voltage analysis were used to study intracellular pH (pH3 regulation and its effects on ionic conductances in the isolated epithelium of frog skin. We show that pHi recovery after an acid load is dependent on the operation of an amiloride-sensitive Na+\\/H + exchanger local- ized at the basolateral cell membranes. The antiporter is not quiescent at physio-

BRIAN J. HARVEY; JORDI EHRENFELD

1988-01-01

90

Fabrication and characterization of dual function nanoscale pH-scanning ion conductance microscopy (SICM) probes for high resolution pH mapping.  

PubMed

The easy fabrication and use of nanoscale dual function pH-scanning ion conductance microscopy (SICM) probes is reported. These probes incorporate an iridium oxide coated carbon electrode for pH measurement and an SICM barrel for distance control, enabling simultaneous pH and topography mapping. These pH-SICM probes were fabricated rapidly from laser pulled theta quartz pipets, with the pH electrode prepared by in situ carbon filling of one of the barrels by the pyrolytic decomposition of butane, followed by electrodeposition of a thin layer of hydrous iridium oxide. The other barrel was filled with an electrolyte solution and Ag/AgCl electrode as part of a conductance cell for SICM. The fabricated probes, with pH and SICM sensing elements typically on the 100 nm scale, were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and various electrochemical measurements. They showed a linear super-Nernstian pH response over a range of pH (pH 2-10). The capability of the pH-SICM probe was demonstrated by detecting both pH and topographical changes during the dissolution of a calcite microcrystal in aqueous solution. This system illustrates the quantitative nature of pH-SICM imaging, because the dissolution process changes the crystal height and interfacial pH (compared to bulk), and each is sensitive to the rate. Both measurements reveal similar dissolution rates, which are in agreement with previously reported literature values measured by classical bulk methods. PMID:23919610

Nadappuram, Binoy Paulose; McKelvey, Kim; Al Botros, Rehab; Colburn, Alex W; Unwin, Patrick R

2013-08-22

91

Conductivity  

NSDL National Science Digital Library

Students make a simple conductivity tester using a battery and light bulb. They learn the difference between conductors and insulators of electrical energy as they test a variety of materials for their ability to conduct electricity.

Integrated Teaching And Learning Program

92

Structure-function relationships in diphtheria toxin channels: III. Residues which affect the cis pH dependence of channel conductance  

Microsoft Academic Search

The conductance of channels formed by diphtheria toxin (DT) in lipid bilayer membranes depends strongly on pH. We have previously shown that a 61 amino acid region of the protein, denoted TH8-9, is sufficient to form channels having the same pH-dependent conductance properties as those of whole toxin channels. One residue in this region, Aspartate 352, is responsible for all

J. A. Mindell; J. A. Silverman; R. J. Collier; A. Finkelstein

1994-01-01

93

K[subscript a] and K[subscript b] from pH and Conductivity Measurements: A General Chemistry Laboratory Exercise  

ERIC Educational Resources Information Center

|The acid ionization constant, K[subscript a], of acetic acid and the base ionization constant, K[subscript b], of ammonia are determined easily and rapidly using a datalogger, a pH sensor, and a conductivity sensor. To decrease sample preparation time and to minimize waste, sequential aliquots of a concentrated standard are added to a known…

Nyasulu, Frazier; Moehring, Michael; Arthasery, Phyllis; Barlag, Rebecca

2011-01-01

94

DEVELOPMENT AND EVALUATION OF AN ACID PRECIPITATION MONITOR FOR FRACTIONAL EVENT SAMPLING WITH CAPABILITY FOR REAL-TIME PH AND CONDUCTIVITY MEASUREMENT  

EPA Science Inventory

An acid precipitation monitor has been developed that collects fractions of rain events, measures the pH and conductivity in real-time, and stores the remaining samples under refrigerated conditions. -80 microprocessor controls all operations of the monitor including sample colle...

95

K[subscript a] and K[subscript b] from pH and Conductivity Measurements: A General Chemistry Laboratory Exercise  

ERIC Educational Resources Information Center

The acid ionization constant, K[subscript a], of acetic acid and the base ionization constant, K[subscript b], of ammonia are determined easily and rapidly using a datalogger, a pH sensor, and a conductivity sensor. To decrease sample preparation time and to minimize waste, sequential aliquots of a concentrated standard are added to a known volume…

Nyasulu, Frazier; Moehring, Michael; Arthasery, Phyllis; Barlag, Rebecca

2011-01-01

96

Ultrasonic Effect on pH, Electric Conductivity, and Tissue Surface of Button Mushrooms, Brussels Sprouts and Cauliflower  

Microsoft Academic Search

Jambrak A.R, Mason T.J., Paniwnyk L., Lelas V. ( 2007): Ultrasonic effect on pH, electric conductiv- ity, and tissue surface of button mushrooms, Brussels sprouts and cauliflower. Czech J. Food Sci., 25: 90-99. and 40 kHz bath for 3 and 10 min were compared with blanched (80°C\\/3 min) and untreated samples. The effect was followed of ultrasound and blanching treatments

97

In situ deployment of voltammetric, potentiometric, and amperometric microelectrodes from a ROV to determine dissolved O{sub 2}, Mn, Fe, S({minus}2), and pH in porewaters  

SciTech Connect

Solid-state microelectrodes have been used in situ in Raritan Bay, NJ to measure pore water profiles of dissolved O{sub 2}, Mn, Fe, and sulfide at (sub)millimeter resolution by voltammetric techniques. The voltammetric sensor was positioned with microprofiling instrumentation mounted on a small remote operated vehicle (ROV). This instrumentation and the sensor were controlled and monitored in real time from a research vessel anchored at the study site. The voltammetric analyzer was connected to the electrodes of the voltammetric cell with a 30 m cable which also bridged receiver-transmitter transducers to ensure signal quality along the cable. Single analyte O{sub 2}, pH, and resistivity microsensors were operated alongside the voltammetric sensor. The authors report on the technology of the system and the concentration changes of redox species observed from 2 to 3 cm above to approximately 4 cm below the sediment-water interface during three deployments. O{sub 2} measurements from both Clark and voltammetric electrodes were in excellent agreement. The profiles obtained show that there is no detectable overlap of O{sub 2} and Mn{sup 2+} in the sediments which is similar to previous reports from other continental margin sediments which were cored and analyzed in the laboratory. These data indicate that O{sub 2} is not a direct oxidant for Mn{sup 2+} when diffusive (rather than advective) processes control the transport of solutes within the sediment. Subsurface Mn{sup 2+} peaks were observed at about 2 cm and coincide with a subsurface pH maximum. The data can be explained by organic matter decomposition with alternate electron acceptors and by the formation of authigenic phases containing reduced Mn at depth.

Luther, G.W. III; Reimers, C.E.; Nuzzio, D.B.; Lovalvo, D.

1999-12-01

98

Influence of temperature, electrical conductivity, power and pH on ascorbic acid degradation kinetics during ohmic heating using stainless steel electrodes  

Microsoft Academic Search

Degradation kinetics of ascorbic acid was determined in pH 5.7 buffer solution using an isothermal batch ohmic heater with stainless steel electrodes. Variables included in this study were temperature (40, 60 and 80 °C); power (0, 100,150 and 300 W); and electrical conductivity (varied using 0.25%, 0.5% and 1.0% NaCl). Ascorbic acid concentration was detected by using a HPLC technique.

AlHussein M. Assiry; Sudhir K. Sastry; Chaminda P. Samaranayake

2006-01-01

99

Fusion of cultured dog kidney (MDCK) cells: II. Relationship between cell pH and K + conductance in response to aldosterone  

Microsoft Academic Search

Summary We have chosen the MDCK cell line to investigate aldosterone action on H+ transport and its role in regulating cell membrane K+ conductance (GmK). Cells grown in a monolayer respond to aldosterone indicated by the dose-dependent formation of domes and by the alkalinization of the dome fluid. The pH sensitivity of the plasma membrane K+ channels was tested in

Hans Oberleithner; Ulrich Kersting; Stefan Silberrlagl; Wieland Steigner; Ulrich Vogel

1989-01-01

100

Development and evaluation of a real-time pH and conductivity rain monitor. Final report for 1984-1986  

SciTech Connect

Acidic wet deposition (acid rain) is thought to be responsible for a variety of deleterious effects on ecosystems and on natural and man-made materials. Determining and quantitating these effects is complicated by the fact that rain is a low-ionic-strength solution of many different salts and organic compounds. The report describes the features and performance of a monitor that was designed to fractionate a rain event into samples corresponding to 0.3 mm of rain, determine the pH and conductivity of the sample within approximately one minute of collection, and store the remainder of the sample for more-detailed analysis.

Paur, R.J.

1987-04-01

101

Particulate and dissolved phases as indicators of limnological and ecophysiological spatial variation in Cima Lake system, Brazil: a case study  

Microsoft Academic Search

The spatial distribution and behavior of limnological variables were studied in a fluvial-lacustrine system, in northern Rio de Janeiro State, Brazil. Physical (e.g. temperature, transparency), physico-chemical (e.g. pH, conductivity), chemical (e.g. inorganic nutrients, dissolved oxygen, particulate and dissolved organic carbon), biochemical (water-soluble carbohydrates – SCHO, total proteins – TPROT, chlorophyll a – Chl a and carotenoids – CAR) and biological

Paulo Pedrosa; Cláudia V. C. Calasans; Carlos E. Rezende

1999-01-01

102

Dissolved Oxygen and Temperature  

Microsoft Academic Search

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

Kelly Addy; Linda Green

103

cAMP/Protein Kinase A Activates Cystic Fibrosis Transmembrane Conductance Regulator for ATP Release from Rat Skeletal Muscle during Low pH or Contractions  

PubMed Central

We have shown that cystic fibrosis transmembrane conductance regulator (CFTR) is involved in ATP release from skeletal muscle at low pH. These experiments investigate the signal transduction mechanism linking pH depression to CFTR activation and ATP release, and evaluate whether CFTR is involved in ATP release from contracting muscle. Lactic acid treatment elevated interstitial ATP of buffer-perfused muscle and extracellular ATP of L6 myocytes: this ATP release was abolished by the non-specific CFTR inhibitor, glibenclamide, or the specific CFTR inhibitor, CFTRinh-172, suggesting that CFTR was involved, and by inhibition of lactic acid entry to cells, indicating that intracellular pH depression was required. Muscle contractions significantly elevated interstitial ATP, but CFTRinh-172 abolished the increase. The cAMP/PKA pathway was involved in the signal transduction pathway for CFTR-regulated ATP release from muscle: forskolin increased CFTR phosphorylation and stimulated ATP release from muscle or myocytes; lactic acid increased intracellular cAMP, pCREB and PKA activity, whereas IBMX enhanced ATP release from myocytes. Inhibition of PKA with KT5720 abolished lactic-acid- or contraction-induced ATP release from muscle. Inhibition of either the Na+/H+-exchanger (NHE) with amiloride or the Na+/Ca2+-exchanger (NCX) with SN6 or KB-R7943 abolished lactic-acid- or contraction-induced release of ATP from muscle, suggesting that these exchange proteins may be involved in the activation of CFTR. Our data suggest that CFTR-regulated release contributes to ATP release from contracting muscle in vivo, and that cAMP and PKA are involved in the activation of CFTR during muscle contractions or acidosis; NHE and NCX may be involved in the signal transduction pathway.

Cai, Weisong; Ballard, Heather J.

2012-01-01

104

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

Microsoft Academic Search

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

R. M. W. Amon; R. Benner

1996-01-01

105

Role of Na+/H+ exchange in the control of intracellular pH and cell membrane conductances in frog skin epithelium  

PubMed Central

Ion-sensitive microelectrodes and current-voltage analysis were used to study intracellular pH (pHi) regulation and its effects on ionic conductances in the isolated epithelium of frog skin. We show that pHi recovery after an acid load is dependent on the operation of an amiloride-sensitive Na+/H+ exchanger localized at the basolateral cell membranes. The antiporter is not quiescent at physiological pHi (7.1- 7.4) and, thus, contributes to the maintenance of steady state pHi. Moreover, intracellular sodium ion activity is also controlled in part by Na+ uptake via the exchanger. Intracellular acidification decreased transepithelial Na+ transport rate, apical Na+ permeability (PNa) and Na+ and K+ conductances. The recovery of these transport parameters after the removal of the acid load was found to be dependent on pHi regulation via Na+/H+ exchange. Conversely, variations in Na+ transport were accompanied by changes in pHi. Inhibition of Na+/K+ ATPase by ouabain produced covariant decreases in pHi and PNa, whereas increases in Na+ transport, occurring spontaneously or after aldosterone treatment, were highly correlated with intracellular alkalinization. We conclude that cytoplasmic H+ activity is regulated by a basolateral Na+/H+ exchanger and that transcellular coupling of ion flows at opposing cell membranes can be modulated by the pHi-regulating mechanism.

1988-01-01

106

Dissolved Oxygen Protocol  

NSDL National Science Digital Library

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

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

2003-08-01

107

Chemistry Review: Dissolving  

NSDL National Science Digital Library

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

Kessler, James; Galvan, Patti

2010-01-01

108

Cell pH of rat renal proximal tubule in vivo and the conductive nature of peritubular HCO 3 ? (OH ? ) exit  

Microsoft Academic Search

Intracellular pH (pHc) was measured on surface loops of rat kidney proximal tubules under free-flow conditions in vivo using fine tip double-barrelled pH microelectrodes based on a neutral H+ ligand. The microelectrodes had Nernstian slopes and a resistance of the order of 1012 O. By using a driven shield feed back circuit the response time to pH jumps was lowered

K. Yoshitomi; E. Frömter

1984-01-01

109

Role of Bicarbonate in the Actions of gamma-aminobutyric acid (Gaba) on Membrane Conductances, Currents, and pH Regulation in Excitable Cells.  

National Technical Information Service (NTIS)

Ion selective microelectrodes and a two or three microelectrode voltage or current clamp were used to examine the effects of inhibitory neurotransmitter Gamma Amino Butyric Acid (GABA) on intracellular pH (pH(i)) extracellular surface pH (pH(s)) intercell...

J. Voipio

1990-01-01

110

Effects of Method and Level of Nitrogen Fertilizer Application on Soil pH, Electrical Conductivity, and Availability of Ammonium and Nitrate in Blueberry  

Technology Transfer Automated Retrieval System (TEKTRAN)

Blueberries (Vaccinium spp.) require low soil pH and prefer N primarily as ammonium for optimum production. Nitrogen fertilizer methods and rates were evaluated in a new field of ‘Bluecrop’ blueberry (Vaccinium corymbosum L.) to determine their effects on soil pH and availability of ammonium and nit...

111

Partial nitrification under limited dissolved oxygen conditions  

Microsoft Academic Search

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

Wang Jianlong; Yang Ning

2004-01-01

112

Conducting Signals  

NSDL National Science Digital Library

In this activity, learners create an electrical circuit and investigate how some dissolved substances conduct electricity. Use this activity to explain how the nervous system sends messages as electrical signals along the length of living nerve cells and the role of nutrition in brain functioning. This lesson guide includes background information, extensions, and a handout.

Moreno, Nancy P.; Tharp, Barbara Z.

2003-01-01

113

Early Life Stage Brook Trout (Salvelinus Fontinalis) Experiment to Determine the Effects of pH, Calcium and Aluminum in Low Conductivity Water.  

National Technical Information Service (NTIS)

Recruitment failure has been suggested as a mechanism leading to loss of fish populations in acidified streams and lakes. Numerous laboratory studies have investigated the effects of pH, aluminum, and calcium, alone or in combination, on early life stages...

C. G. Ingersoll H. L. Bergman J. Breck T. W. La Point

1984-01-01

114

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

Microsoft Academic Search

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

Peter J. Hernes; Ronald Benner

2003-01-01

115

Effect of pH and conductivity on hindered diffusion of perchlorate ions during transport through negatively charged nanofiltration and ultrafiltration membranes  

Microsoft Academic Search

Hindered (effective) diffusion of perchlorate anion (ClO4?) through negatively-charged porous nanofiltration and ultrafiltration membranes was determined by means of diffusion cell experiments. Three electrolytes, KCl, K2SO4, and CaCl2, were employed to determine their effects on the effective diffusion of perchlorate through membrane pores under varying pH levels (4, 6, 8, and 10). In addition, the effect of electrolyte concentration on

Yeomin Yoon; Gary Amy; Jaekyung Yoon

2005-01-01

116

The dependence of the effects of i.cor. Administered adenosine and of coronary conductance on the arterial pH, p CO 2 and buffer capacity in dogs  

Microsoft Academic Search

Summary Coronary conductance and the coronary dilatory action of adenosine, injected into the left coronary artery, were investigated at different arterial pH andpCO2 in intact anaesthetized dogs. Four groups of experiments were carried out: Experiments with slow i.v. infusion 1. of 0.1 N HCl, 2. of 5% NaHCO3, 3. of 1 M THAM and 4. of 0.1 N HCl following

G. Raberger; M. Weissel; O. Kraupp

1971-01-01

117

Dissolved and Total Copper in a Coal Ash Effluent and Receiving Stream: Assessment of In Situ Biological Effects  

Microsoft Academic Search

An in situ chemical and biological study was conducted in the lower Muskingum River (southeast Ohio, U.S.A.) to evaluate potential effects of copper (Cu) discharged from a coal ash effluent. Effluent total Cu, dissolved Cu, TSS and pH measurements were performed monthlyduring January–December 1995. Benthic macroinvertebrates were sampled at five river locations using artificial substrate samplers, and in situ Cu

Robin J. Reash

2004-01-01

118

Dissolver vessel bottom assembly  

DOEpatents

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

Kilian, Douglas C. (Kennewick, WA)

1976-01-01

119

Do pH changes in the leaf apoplast contribute to rapid inhibition of leaf elongation rate by water stress? Comparison of stress responses induced by polyethylene glycol and down-regulation of root hydraulic conductivity.  

PubMed

We have dissected the influences of apoplastic pH and cell turgor on short-term responses of leaf growth to plant water status, by using a combination of a double-barrelled pH-selective microelectrodes and a cell pressure probe. These techniques were used, together with continuous measurements of leaf elongation rate (LER), in the (hidden) elongating zone of the leaves of intact maize plants while exposing roots to various treatments. Polyethylene glycol (PEG) reduced water availability to roots, while acid load and anoxia decreased root hydraulic conductivity. During the first 30 min, acid load and anoxia induced moderate reductions in leaf growth and turgor, with no effect on leaf apoplastic pH. PEG stopped leaf growth, while turgor was only partially reduced. Rapid alkalinization of the apoplast, from pH 4.9 ± 0.3 to pH 5.8 ± 0.2 within 30 min, may have participated to this rapid growth reduction. After 60 min, leaf growth inhibition correlated well with turgor reduction across all treatments, supporting a growth limitation by hydraulics. We conclude that apoplastic alkalinization may transiently impair the control of leaf growth by cell turgor upon abrupt water stress, whereas direct hydraulic control of growth predominates under moderate conditions and after a 30-60 min delay following imposition of water stress. PMID:21477119

Ehlert, Christina; Plassard, Claude; Cookson, Sarah Jane; Tardieu, François; Simonneau, Thierry

2011-05-16

120

Cell-to-cell channels with two independently regulated gates in series: Analysis of junctional conductance modulation by membrane potential, calcium, and pH  

Microsoft Academic Search

Summary We study cell-to-cell channels, in cell pairs isolated fromChironomus salivary gland, by investigating the dependence of junctional conductance (gj) on membrane potentials (E1,E2), on Ca2+, and on H+, and we explore the interrelations among these dependencies; we use two separate voltage clamps to set the membrane potentials and to measuregj. We findgj to depend on membrane potentials whether or

Ana Lia Obaid; Sidney J. Socolar; Birgit Rose

1983-01-01

121

Dissolved Oxygen in Water  

Microsoft Academic Search

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

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

122

Melting and dissolving  

NASA Astrophysics Data System (ADS)

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

Woods, Andrew W.

1992-06-01

123

Dissolved Oxygen Activity  

NSDL National Science Digital Library

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

Gordon, Steve

124

Dissolved Oxygen Model  

NSDL National Science Digital Library

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

Gordon, Steve

125

Temperature Affects Dissolving  

NSDL National Science Digital Library

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

Kessler, James; Galvan, Patti

2010-01-01

126

A new pH-ISFET based dissolved oxygen sensor by employing electrolysis of oxygen  

Microsoft Academic Search

A new dissolved oxygen sensor based on a pH-ISFET is discussed. A working electrode surrounding a pH-sensing gate of the pH-ISFET electrolyzes dissolved oxygen, resulting in a corresponding pH change near the pH-sensing gate. The pH-ISFET is expected to determine dissolved oxygen concentration by detecting this pH change. The results suggest that the proposed sensor operated by a combined mechanism

Byung-Ki Sohn; Chang-Soo Kim

1996-01-01

127

Human radiation studies: Remembering the early years: Oral history of cell biologist Don Francis Petersen, Ph.D., conducted November 29, 1994  

SciTech Connect

This report is a transcript of an interview of Dr. Don Francis Petersen by representatives of the US DOE Office of Human Radiation Experiments. Dr. Petersen was selected for this interview because of his long research career at Los Alamos and his knowledge of the Atomic Energy Commission`s biomedical program. Dr. Petersen did not personally conduct research on human subjects. After a brief biographical sketch Dr. Petersen discusses his remembrances of the early use of radionuclides as biological tracers, aspects of nuclear weapons testing in the 1940`s and 1950`s including fallout studies, the means by which research projects were approved, use of humans in the whole-body counter, and the Health Division Biomedical responsibilities.

NONE

1995-08-01

128

Lap-Dissolve Slides  

ERIC Educational Resources Information Center

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

Fine, Leonard W.; And Others

1977-01-01

129

Dissolving a Partnership Efficiently  

Microsoft Academic Search

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

Peter Cramton; Robert Gibbons; PAUL KLEMPERERI

1987-01-01

130

Developing Standards for Dissolved Iron in Seawater  

Microsoft Academic Search

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

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

2007-01-01

131

A Dissolving Challenge  

NSDL National Science Digital Library

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

Kessler, James H.; Galvan, Patricia M.

2007-01-01

132

A quality-control method for physical and chemical monitoring data. Application to dissolved oxygen levels in the river Loire (France)  

Microsoft Academic Search

A quality-control method is proposed for examining continuous physical and chemical measurements, including temperature, dissolved oxygen, pH and electrical conductivity. Firstly, measurement consistency is evaluated by various modelling approaches: internal series structure, inter-variable relations or relations with external variables, spatial coherence and deterministic models. Secondly, outliers or systematic errors are detected using classical statistical tests. The method was evaluated for

F. Moatar; J. Miquel; A. Poirel

2001-01-01

133

Dissolved-Oxygen Requirements of Three Species of Fish  

Microsoft Academic Search

Critical dissolved-oxygen levels and standard metabolic rates were determined for the bluegill, Lepomis macrochirus; largemouth bass, Micropterus salmoides; and the channel catfish, Ictalurus punctatus, at 25° C., 30° C., and 35° C. Two types of experiments were conducted: shock tests in which the dissolved oxygen was dropped rapidly from near saturation to a critically low point; and acclimation tests in

D. D. Moss; D. C. Scott

1961-01-01

134

CASAA Dissolvables - Attachment 6 1  

Center for Biologics Evaluation and Research (CBER)

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

135

Developing Standards for Dissolved Iron in Seawater  

NASA Astrophysics Data System (ADS)

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

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

2007-03-01

136

Method of dissolving organic filter cake  

SciTech Connect

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

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

1989-03-07

137

Using water chemistry time series to model dissolved inorganic carbon dynamics in the western Amazon basin  

NASA Astrophysics Data System (ADS)

Two small streams (New Colpita and Main Trail) and two rivers (Tambopata and La Torre), in the Tambopata National Reserve, Madre de Dios, Peru, were sampled for water chemistry (conductivity, pH and dissolved oxygen) and hydrology (stage height and flow velocity). In the small streams water chemistry and hydrology variables were logged at 15 minute intervals from Feb 2011 to November 2012. Water samples were collected from all four channels during field campaigns spanning different seasons and targeting the hydrological extremes. All the samples were analysed for dissolved inorganic carbon (DIC) concentration and ?13C (sample size ranging from 77 to 172 depending on the drainage system) and a smaller subset for dissolved organic carbon (DOC) and particulate organic carbon (POC) concentrations. Strong positive relationships were found between conductivity and both DIC concentration and ?13C in the New Colpita stream and the La Torre river. In Tambopata river the trends were less clear and in the Main Trail stream there was very little change in DIC and isotopic composition. The conductivity data was used to model continuous DIC time series for the New Colpita stream. The modelled DIC data agreed well with the measurements; the concordance correlation coefficients between predicted and measured data were 0.91 and 0.87 for mM-DIC and ?13C-DIC, respectively. The predictions of ?13C-DIC were improved when calendar month was included in the model, which indicates seasonal differences in the ?13C-DIC conductivity relationship. At present, continuous DIC sampling still requires expensive instrumentation. Therefore, modelling DIC from a proxy variable which can be monitored continuously with ease and at relatively low cost, such as conductivity, provides a powerful alternative method of DIC determination.

Vihermaa, Leena; Waldron, Susan; Newton, Jason

2013-04-01

138

Electrochemical determination of dissolved uranium in Krka river estuary  

Microsoft Academic Search

The applicability of the previously developed method for electrochemical determination of dissolved uranium concentration has been tested on natural water samples taken from the Krka river estuary during various seasons and along different depth profiles. The method is based on the following treatment of the sample: destroying the uranyl-carbonato complexes by adjusting the pH to 3, enabling the formation of

R Djogi?; M Branica

2001-01-01

139

Chemical characterization of dissolvable tobacco products promoted to reduce harm.  

PubMed

In 2009, the R. J. Reynolds Tobacco Co. released a line of dissolvable tobacco products that are marketed as an alternative to smoking in places where smoking is prohibited. These products are currently available in Indianapolis, IN, Columbus, OH, and Portland, OR. This paper describes the chemical characterization of four such products by gas chromatography-mass spectrometry (GC-MS). The dissolvable tobacco products were extracted and prepared by ultrasonic extraction using acetone, trimethylsilyl derivatization, and headspace solid phase microextraction (SPME). The following compounds were identified in the dissolvables using either ultrasonic extractions or trimethylsilyl derivatization: nicotine, ethyl citrate, palmitic acid, stearic acid, sorbitol, glycerol, and xylitol. The following compounds were identified in the dissolvables using headspace SPME: nicotine, ethyl citrate, cinnamaldehyde, coumarin, vanillin, and carvone. With the exception of nicotine, the compounds identified thus far in the dissolvables are either flavoring compounds or binders. The concentration of free nicotine in the dissolvables was determined from the Henderson-Hasselbalch equation and by measuring the pH and nicotine concentration by GC-MS. The results presented here are the first to reveal the complexity of dissolvable tobacco products and may be used to assess potential oral health effects. PMID:21332188

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

2011-02-18

140

Enhanced dissolution of cinnabar (mercuric sulfide) by dissolved organic matter isolated from the Florida Everglades  

SciTech Connect

Organic matter isolated from the Florida Everglades caused a dramatic increase in mercury release from cinnabar (HgS), a solid with limited solubility. Hydrophobic (a mixture of both humic and fulvic) acids dissolved more mercury than hydrophilic acids and other nonacid fractions of dissolved organic matter (DOM). Cinnabar dissolution by isolated organic matter and natural water samples was inhibited by cations such as Ca{sup 2+}. Dissolution was independent of oxygen content in experimental solutions. Dissolution experiments conducted in Dl water had no detectable dissolved mercury. The presence of various inorganic (chloride, sulfate, or sulfide) and organic ligands (salicylic acid, acetic acid, EDTA, or cysteine) did not enhance the dissolution of mercury from the mineral. Aromatic carbon content in the isolates correlated positively with enhanced cinnabar dissolution. {zeta}-potential measurements indicated sorption of negatively charged organic matter to the negatively charged cinnabar at pH 6.0. Possible mechanisms of dissolution include surface complexation of mercury and oxidation of surface sulfur species by the organic matter.

Ravichandran, M.; Ryan, J.N. [Univ. of Colorado, Boulder, CO (United States). Dept. of Civil, Environmental, and Architectural Engineering; Aiken, G.R.; Reddy, M.M. [Geological Survey, Boulder, CO (United States)

1998-11-01

141

Dissolved Oxygen Characteristics of Spring Algal Bloom in Xiangxi Bay of Three Gorges Reservoir  

Microsoft Academic Search

Dissolved oxygen characteristics of spring algal bloom in Xiangxi Bay of Three Gorges Reservoir were studied. In surveys, 12 stations have been investigated and 132 samples were collected weekly from February 24 to May 10 in 2008. Chlorophyll a, pH and water temperature could be the significant influence factors to dissolved oxygen in spring algal bloom by using stepwise multiple

Huajun Luo; Defu Liu; Daobin Ji; Yingping Huang

2010-01-01

142

Empirical model for dissolved oxygen depletion during corrosion of drinking water copper pipes  

Microsoft Academic Search

Predictive models characterizing the evolution and interaction of key parameters of water chemistry are needed to better understand corrosion events in drinking water pipes. We performed experiments with new copper pipes under combinations of pH, dissolved oxygen (DO), temperature, chlorine, and dissolved inorganic carbon. We found that DO consumption during 24h of stagnation was not limited by diffusion, thus the

Ignacio T. Vargas; Pablo A. Pastén; Gonzalo E. Pizarro

2010-01-01

143

Yucca Mountain Area Saturated Zone Dissolved Organic Carbon Isotopic Data  

SciTech Connect

Groundwater samples in the Yucca Mountain area were collected for chemical and isotopic analyses and measurements of water temperature, pH, specific conductivity, and alkalinity were obtained at the well or spring at the time of sampling. For this project, groundwater samples were analyzed for major-ion chemistry, deuterium, oxygen-18, and carbon isotopes of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC). The U.S. Geological Survey (USGS) performed all the fieldwork on this project including measurement of water chemistry field parameters and sample collection. The major ions dissolved in the groundwater, deuterium, oxygen-18, and carbon isotopes of dissolved inorganic carbon (DIC) were analyzed by the USGS. All preparation and processing of samples for DOC carbon isotopic analyses and geochemical modeling were performed by the Desert Research Institute (DRI). Analysis of the DOC carbon dioxide gas produced at DRI to obtain carbon-13 and carbon-14 values was conducted at the University of Arizona Accelerator Facility (a NSHE Yucca Mountain project QA qualified contract facility). The major-ion chemistry, deuterium, oxygen-18, and carbon isotopes of DIC were used in geochemical modeling (NETPATH) to determine groundwater sources, flow paths, mixing, and ages. The carbon isotopes of DOC were used to calculate groundwater ages that are independent of DIC model corrected carbon-14 ages. The DIC model corrected carbon-14 calculated ages were used to evaluate groundwater travel times for mixtures of water including water beneath Yucca Mountain. When possible, groundwater travel times were calculated for groundwater flow from beneath Yucca Mountain to down gradient sample sites. DOC carbon-14 groundwater ages were also calculated for groundwaters in the Yucca Mountain area. When possible, groundwater travel times were estimated for groundwater flow from beneath Yucca Mountain to down gradient groundwater sample sites using the DOC calculated groundwater ages. The DIC calculated groundwater ages were compared with DOC calculated groundwater ages and both of these ages were compared to travel times developed in ground-water flow and transport models. If nuclear waste is stored in Yucca Mountain, the saturated zone is the final barrier against the release of radionuclides to the environment. The most recent rendition of the TSPA takes little credit for the presence of the saturated zone and is a testament to the inadequate understanding of this important barrier. If radionuclides reach the saturated zone beneath Yucca Mountain, then there is a travel time before they would leave the Yucca Mountain area and flow down gradient to the Amargosa Valley area. Knowing how long it takes groundwater in the saturated zone to flow from beneath Yucca Mountain to down gradient areas is critical information for potential radionuclide transport. Radionuclide transport in groundwater may be the quickest pathway for radionuclides in the proposed Yucca Mountain repository to reach land surface by way of groundwater pumped in Amargosa Valley. An alternative approach to ground-water flow and transport models to determine the travel time of radionuclides from beneath Yucca Mountain to down gradient areas in the saturated zone is by carbon-14 dating of both inorganic and organic carbon dissolved in the groundwater. A standard method of determining ground-water ages is to measure the carbon-13 and carbon-14 of DIC in the groundwater and then correct the measured carbon-14 along a flow path for geochemical reactions that involve carbon containing phases. These geochemical reactions are constrained by carbon-13 and isotopic fractionations. Without correcting for geochemical reactions, the ground-water ages calculated from only the differences in carbon-14 measured along a flow path (assuming the decrease in carbon-14 is due strictly to radioactive decay) could be tens of thousands of years too old. The computer program NETPATH, developed by the USGS, is the best geochemical program for correcting carbon-14 activities for geochemical r

Thomas, James; Decker, David; Patterson, Gary; Peterman, Zell; Mihevc, Todd; Larsen, Jessica; Hershey, Ronald

2007-06-25

144

Method for dissolving plutonium dioxide  

DOEpatents

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

Tallent, Othar K. (Oak Ridge, TN)

1978-01-01

145

Effect of Leaf Litter Diversity on Dissolved Organic Matter Export in a Deciduous Forest Soil  

NASA Astrophysics Data System (ADS)

We investigated sources and fate of dissolved organic matter (DOM) in soils in order to understand the effect of tree diversity on below ground processes. We established a leaf litter exchange experiment in the National Park Hainich (Thuringia, Germany) in December 2008. Labeled (13C) and unlabeled leaf litter of beach (Fagus sylvatica) and ash (Fraxinus excelsior) were exposed to study the decomposition process. Soil water was collected biweekly with glass suction plates (1 ?m pore size, UMS, Munich, Germany) in 5 cm soil depth and pH, conductivity, DOC and anions (Cl-, NO3-, NO2-, PO43-, SO42-, F-) were determined. The 13DOC values were measured using high performance liquid chromatography - isotope ratio mass spectrometry (HPLC-IRMS). The values of conductivity and pH in the soil water indicate slower decomposition processes for leaf litter of beech in comparison to ash leaf litter. The conductivity was correlated with the Cl- ion during the first spring, which suggests the export of carbon due to leaching processes. However during the summer the conductivity correlated with the NO3- ions, which indicates mineralization as driving process. Surprisingly, the contribution of litter 13C into the dissolved carbon pool was very low. The highest contribution with up to 8.6% DOC labeled by ash litter derived carbon was found in the first 3 month of application. However, in the mean only 1.2% and 2.6% of DOC was labeled by carbon of the beech and ash litter, respectively. This represents in total only up to 0.41% of labeled litter carbon that was added. The higher percentages of ash litter derived 13C in DOM of soil water compared to beech indicates a positive effect of litter quality on decomposition. However, we did not find a faster decomposition or higher ash litter derived carbon export in mixed (ash and beech litter) treatments, which would indicate food selection or biodiversity effects.

Scheibe*, A.; Eißfeller, V.; Langenbruch, C.; Seven, J.; Gleixner, G.

2012-04-01

146

METHOD OF DISSOLVING MASSIVE PLUTONIUM  

DOEpatents

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

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

1960-06-28

147

Biogeochemical controls on seasonal variations of the stable isotopes of dissolved oxygen and dissolved inorganic carbon in Castle Lake, CA  

NASA Astrophysics Data System (ADS)

The purpose of this project is to perform a seasonal dissolved oxygen (DO) and dissolved inorganic carbon (DIC) stable isotope (?18O, ?13C) study to assess the fluctuations in biogeochemical processes with depth in a lake. DO and DIC concentrations and stable isotope compositions (?18O-DO, ?13C-DIC) have been used as a technique to study the systematics of diurnal freshwater biogeochemical processes, primarily photosynthesis, respiration, and gas-exchange (e.g. Quay et al. 1995, Trojanowska et al. 2008). For example, photosynthesis produces DO isotopically identical to the host water, typically light relative to atmospheric oxygen (+23.5‰), while respiration preferentially consumes isotopically light DO. Diel ?18O-DO and ?13C-DIC studies in rivers (e.g. Parker et al. 2005, Parker et al. 2010, Poulson & Sullivan 2010) have been used to determine the rates of biogeochemical processes over a 24h time scale. However, similar studies in lakes are rare, for either diel or seasonal time scales. The focus of this project is Castle Lake, 12km southwest of Mt. Shasta, CA, at an elevation of 1660m. Castle Lake is an alpine, meso-oligotrophic lake with a 19ha surface area and a maximum depth of up to 35m. This project consists of sampling profiles, 2-3 weeks apart, throughout the 2010 field season for monitoring seasonal depth trends, with measurements of DO concentration, temperature, pH, alkalinity, specific conductivity, PAR, chlorophyll concentration, ?18O-DO, ?13C-DIC, ?18O-H2O, and ?D-H2O. Diel measurements of DO concentration, temperature, pH, specific conductivity, PAR, and chlorophyll concentration have also been performed at various depths. To date, the profile data collected at Castle Lake show various seasonal changes, starting after ice-out (late June 2010) through mid-August 2010. DO profiles display a positive heterograde trend with a maximum of 11.33mg/L at 12m in mid-August and minima of ?0.12mg/L near the lake bottom. DIC concentrations increase with depth and with time up to 2mmol/L at 30m by mid-August. pH ranges from 5.9-7.5 and consistently increases in the metalimnion (5-15m) with the season. ?18O-DO profiles show inverse trends relative to DO concentration, and range from +15.8 to +27.8‰ after ice-out and from +10.2 to +30.9‰ in mid-August. ?13C-DIC profiles also show inverse trends relative to DIC concentration, reach a maximum of -12 to -10‰, generally in the metalimnion, and a minimum of down to -18‰ near the bottom of the hypolimnion (28-30m sampling depth). DO concentration, ?18O-DO, DIC concentration, and ?13C-DIC data all suggest that: photosynthesis is the principal process affecting DO in the metalimnion; that respiration is the dominant process affecting DIC in the hypolimnion; and that both processes increase in magnitude over the course of the season. To date, no significant diel variations of DO or pH have been observed. The ?18O-DO and ?13C-DIC results thus far are consistent with systematic variations of photosynthesis and respiration rates during the course of a season, suggesting the analyses in this study provide a reliable means for the quantitative study of biogeochemical processes in lakes on a seasonal time scale.

Brown, J. M.; Poulson, S. R.

2010-12-01

148

Productivity Estimation of Hypersaline Microbial Mat Communities - Diurnal Cycles of Dissolved Oxygen  

NASA Astrophysics Data System (ADS)

Hypersaline microbial mat communities (MMC) are the modern equivalents of the Archean stromatolities, the first photosynthetic organisms on Earth. An estimate of their oxygen production rate is important to the understanding of oxygen evolution on Earth ca. 2 b.y.b.p. Here we use the diurnal cycle of dissolved oxygen, O2/Ar ratio and the isotopic composition of dissolved oxygen to calculate net and gross primary productivity of MMC growing in a large scale (80 m2) experimental pan. The pan is inoculated with MMC taken from the Solar Lake, Sinai, Egypt and filled with 90\\permil evaporated Red Sea water brine up to a depth of ca. 0.25 m. It is equipped with computerized flow through system that is programmed to pump pan water at selected time intervals into a sampling cell fitted with dissolved oxygen, pH, conductivity and temperature sensors connected to a datalogger. Manual brine samples were taken for calibrating the sensors, mass spectrometric analyses and for measurements of additional relevant parameters. Dissolved oxygen concentrations fluctuate during the diurnal cycle being highly supersaturated except for the end of the night. The O2 curve varies seasonally and has a typical "shark fin" shape due to the MMC metabolic response to the shape of the diurnal light curve. The dissolved oxygen data were fitted to a smooth curve that its time derivative (dO2 /dt) is defined as: Z dO2 /dt=GP-R-k(O2(meas)- O2(sat)) where z is the depth (m); GP and R are the MMC gross production and respiration (mol m-2 d-1), respectively; k is the gas exchange coefficient (m d-1); O2(meas) and O2(sat) (mol L-1) are the measured and equilibrium dissolved oxygen concentrations, respectively. The high resolution sampling of the automated system produces O2 curves that enable the calculation of smooth and reliable time derivatives. The calculations yield net production values that vary between 1,000 10-6 to -100 10-6 mol O2 m-2 h-1 and day respiration rates between 60 10-6 to 30 10-6 mol O2 m-2 h-1 in summer and winter, respectively. Independent estimate of the gross productivity and respiration is provided by the oxygen isotopic measurements.

Less, G.; Cohen, Y.; Luz, B.; Lazar, B.

2002-05-01

149

Study on the numerical simulation of the dissolved air releaser in the energy microalgae recovery device  

Microsoft Academic Search

Dissolv ed air flotation recovery is one of the feasible microalgae recovery methods. Choose the standard k - (; turbulent calculation model to conduct numerical simulation to the flow field of the dissolved air releaser of the energy microalgae recovery device, and study the structural parameters and power dissipation. The result of the numerical simulation conducted to the value of

Wang Guang-hui; Kuang Ya-li; Lin Zhe; Chen Xue

2011-01-01

150

DISSOLVED CONCENTRATION LIMITS OF RADIOACTIVE ELEMENTS  

SciTech Connect

The purpose of this study is to evaluate dissolved concentration limits (also referred to as solubility limits) of elements with radioactive isotopes under probable repository conditions, based on geochemical modeling calculations using geochemical modeling tools, thermodynamic databases, field measurements, and laboratory experiments. The scope of this modeling activity is to predict dissolved concentrations or solubility limits for 14 elements with radioactive isotopes (actinium, americium, carbon, cesium, iodine, lead, neptunium, plutonium, protactinium, radium, strontium, technetium, thorium, and uranium) important to calculated dose. Model outputs for uranium, plutonium, neptunium, thorium, americium, and protactinium are in the form of tabulated functions with pH and log (line integral) CO{sub 2} as independent variables, plus one or more uncertainty terms. The solubility limits for the remaining elements are either in the form of distributions or single values. The output data from this report are fundamental inputs for Total System Performance Assessment for the License Application (TSPA-LA) to determine the estimated release of these elements from waste packages and the engineered barrier system. Consistent modeling approaches and environmental conditions were used to develop solubility models for all of the actinides. These models cover broad ranges of environmental conditions so that they are applicable to both waste packages and the invert. Uncertainties from thermodynamic data, water chemistry, temperature variation, and activity coefficients have been quantified or otherwise addressed.

NA

2004-11-22

151

Simultaneous fluorimetric determination of the biodegradation processes of dissolved multi-component PAHs  

Microsoft Academic Search

A fluorimetric method for simultaneous determination of dissolved acenaphthylene (Ace) phenanthrene (Ph) and pyrene (Py), mixed in an aqueous mineral salts medium (MSM), was developed. The linear ranges for determination of Ace, Ph and Py dissolved in the mixture were 4.00×10?6 to 3.00×10?3g\\/L, 2.00×10?6 to 1.00×10?3g\\/L and 7.00×10?7 to 1.00×10?4g\\/L. The limits of detection for Ace, Ph and Py were

Ling Zi Sang; Xing Yuan Wei; Jia Ning Chen; Ya Xian Zhu; Yong Zhang

2009-01-01

152

Electrochemical determination of dissolved uranium in Krka River estuary.  

PubMed

The applicability of the previously developed method for electrochemical determination of dissolved uranium concentration has been tested on natural water samples taken from the Krka river estuary during various seasons and along different depth profiles. The method is based on the following treatment of the sample: destroying the uranyl-carbonato complexes by adjusting the pH to 3, enabling the formation of adsorbable uranyl-hydroxo complexes by adjusting the pH to 6.5-7.0 and measurement by cathodic stripping voltammetry technique. As the signal of the dissolved uranium reduction is sometimes masked by the signal of the matrix of the sample, a resolution enhancement including digestion and/or deconvolution has to be applied. The measured concentration of dissolved uranium varies in the range from 0.4 to 3.3 x 10(-8) mol l-1, corresponding to the data found in the literature. The depth profile of dissolved uranium concentration distributions shows conservative behaviour. The X-ray fluorescence spectroscopy (XRF) confirmed the applicability of the method, yet pointing out to its limitations caused by the matrix of the solution. PMID:11337837

Djogi?, R; Pizeta, I; Branica, M

2001-06-01

153

Removal properties of dissolved boron by glucomannan gel.  

PubMed

Boron ions have long been known to form complexes with the cis-diol group of a polysaccharide. Konjac glucomannan (KGM) which is one of polysaccharides was used to remove dissolved boron in this study. KGM forms a complex with boron, but does not remove boron from contaminated waters as well as other polysaccharides because of its high water solubility. Therefore, the removal efficiencies of dissolved boron were examined using both an insoluble KGM gel and KGM semi-gel. The former did not remove dissolved boron, but the latter did. The difference in the ability of boron removal was due to the presence of diol group inside. KGM loses free diol group during the process of gelation. On the other hand, the semi-gel gelated only surface layer in water has diol group inside. The boron removal capacity of the semi-gel was highest at pHs?11, when the boron species is present as B(OH)4(-). The capacity was slightly increased by the addition of Al, Ca and Mg under high pH conditions. This was due to co-precipitation of boron with Ca dissolved from the semi-gel. The boron adsorbed to the semi-gel easily was desorbed under low pH conditions and the hysteresis was not found. PMID:23260255

Oishi, Kyoko; Maehata, Yugo

2012-12-20

154

Reducing emissions from uranium dissolving  

SciTech Connect

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

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

1992-10-01

155

Reducing emissions from uranium dissolving  

SciTech Connect

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

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

1992-10-01

156

Oxidative dissolution of metacinnabar (?-HgS) by dissolved oxygen  

Microsoft Academic Search

The oxidative dissolution rate of metacinnabar by dissolved O2 was measured at pH ?5 in batch and column reactors. In the batch reactors, the dissolution rate varied from 3.15 (±0.40) to 5.87 (±0.39) × 10?2 ?mol\\/m2\\/day (I=0.01 M, 23°C) and increased with stirring speed, a characteristic normally associated with a transport-controlled reaction. However, theoretical calculations, a measured activation energy of

Mark O Barnett; Ralph R Turner; Philip C Singer

2001-01-01

157

The diffusion of dissolved silica in dilute aqueous solution  

NASA Astrophysics Data System (ADS)

The diffusion coefficient of dissolved silica at 25.5 ± .5° C was determined as a function of concentration using a non-steady-state method whereby agar-gelled solutions containing dissolved silica from 0.09 to 1.50 mM ( pH = 5.5) were placed in contact with distilled water in glass cells. Diffusion coefficients were obtained by measuring the dissolved silica content of the distilled water after a given length of time. The measured diffusion coefficients decreased as a function of increasing dissolved silica concentration, which is thought to reflect an increase in dimeric silica according to the equilibrium: 2 Si ( OH ) 4 = Si 2 O ( OH ) 6 + H 2 O . The tracer diffusion coefficients for Si(OH) 4 and Si 2 O(OH) 6 and an association constant for the above reaction were determined by fitting the following equation to the experimental data: D obs = D monomer + (1 - ) D dimer where is the fraction of total dissolved silica which is Si(OH) 4 . The best fit yielded tracer D 's for Si(OH) 4 and Si 2 O(OH) 6 of 2.2 and 1.0 (in units of 10 -5 cm 2 sec -1 ), respectively, and an association constant of 330.

Applin, Kenneth R.

1987-08-01

158

Dissolving a Substance in Different Liquids  

NSDL National Science Digital Library

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

Kessler, James H.; Galvan, Patricia M.

2007-01-01

159

Dissolving Different Liquids in Water  

NSDL National Science Digital Library

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

Kessler, James; Galvan, Patti

2010-01-01

160

pH  

NSDL National Science Digital Library

This lab activity is designed to teach students how to test for pH and understand its relationship to them and their environment. They will learn what pH is, draw and label a pH scale, measure the pH of various items, and explain why it's important to understand pH, for example, the danger presented by substances having very high or low pH.

161

Dynamics of planktonic prokaryotes and dissolved carbon in a subtropical coastal lake.  

PubMed

To understand the dynamics of planktonic prokaryotes in a subtropical lake and its relationship with carbon, we conducted water sampling through four 48-h periods in Peri Lake for 1?year. Planktonic prokaryotes were characterized by the abundance and biomass of heterotrophic bacteria (HB) and of cyanobacteria (coccoid and filamentous cells). During all samplings, we measured wind speed, water temperature (WT), pH, dissolved oxygen (DO), precipitation, dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and carbon dioxide (CO2). DOC was higher in the summer (average?=?465??M - WT?=?27°C) and lower in the winter (average?=?235??M - WT?=?17°C), with no significant variability throughout the daily cycles. CO2 concentrations presented a different pattern, with a minimum in the warm waters of the summer period (8.31??M) and a maximum in the spring (37.13??M). Daily trends were observed for pH, DO, WT, and CO2. At an annual scale, both biological and physical-chemical controls were important regulators of CO2. HB abundance and biomass were higher in the winter sampling (5.60?×?10(9)?cells?L(-1) and 20.83??mol?C?L(-1)) and lower in the summer (1.87?×?10(9)?cells?L(-1) and 3.95??mol?C?L(-1)). Filamentous cyanobacteria (0.23?×?10(8)-0.68?×?10(8)?filaments?L(-1)) produced up to 167.16??mol?C?L(-1) as biomass (during the warmer period), whereas coccoid cyanobacteria contributed only 0.38??mol?C?L(-1). Precipitation, temperature, and the biomass of HB were the main regulators of CO2 concentrations. Temperature had a negative effect on the concentration of CO2, which may be indirectly attributed to high heterotroph activity in the autumn and winter periods. DOC was positively correlated with the abundance of total cyanobacteria and negatively with HB. Thus, planktonic prokaryotes have played an important role in the dynamics of both dissolved inorganic and organic carbon in the lake. PMID:23579926

Fontes, Maria Luiza S; Tonetta, Denise; Dalpaz, Larissa; Antônio, Regina V; Petrucio, Maurício M

2013-04-08

162

Influence of pH and natural organic matter on zinc biosorption in a model lignocellulosic biofuel biorefinery effluent.  

PubMed

The effect of dissolved natural organic matter (NOM) and pH on microbial biosorption of Zn was evaluated in a model lignocellulosic biofuel refinery effluent rich in NOM. Batch culture experiments conducted with two model microorganisms (yeast, Candida tropicalis; bacteria Novosphingobium nitrogenifigens Y88(T)), showed an inhibitory effect of NOM, and an optimum pH for Zn removal at 7.5-8.0. Membrane bioreactors with mixed autochthonous organisms were operated at pH 6.5 and pH 8.0 to better simulate real-world remediation scenarios. More Zn was removed at the high (91%) than at the low (26%) pH, presumably because the higher pH freed negatively-charged functional groups on the cellular biomass for passive Zn binding. Manipulating the pH of bioreactors can significantly improve metal removal in NOM rich wastewater. Such reactors could maintain water quality for closed-cycle biorefineries, leading to reduced water consumption, and a more sustainable biofuel. PMID:23933024

Palumbo, Amanda J; Daughney, Christopher J; Slade, Alison H; Glover, Chris N

2013-07-20

163

Solubilization of hydroxyapatite at neutral pH by an anionic ionic exchange resin.  

PubMed

Sucrose, induced dental plaque has been shown to contain high amounts of lipoteichoic acids, a bacterial anionic polymer with chemical properties similar to ionic exchange resins. The present study describes an in vitro experiment where a commercial resin Amberlite IR 120 was shown to dissolve hydroxyapatite at neutral pH. The resin binds calcium and the dissociation of the hydroxyapatite Ca5(PO4)3OH leads to 5Ca++ +3 PO4(-3) + OH- is driven to the right as long as the resin takes up calcium. The dissociation of the hydroxyapatite was monitored by electrical conductivity and pH of the aqueous phase. It is suggested that this mechanism may be of some significance in vivo. PMID:6937087

Rölla, G; Bergseth, H; Svatun, B

1980-01-01

164

Dissolved oxygen and fish behavior  

Microsoft Academic Search

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

Donald L. Kramer

1987-01-01

165

Dissolving Pulp Industry. Market Trends.  

National Technical Information Service (NTIS)

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

I. Durbak

1993-01-01

166

Phase fluorometric dissolved oxygen sensor  

Microsoft Academic Search

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

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

2001-01-01

167

Adsorption of dissolved organic carbon extracted from sewage sludge on montmorillonite and kaolinite in the presence of metal ions  

SciTech Connect

The adsorption of dissolved organic carbon extracted from sewage sludge (SSDOC) and its complexes with Co, Pb, and Cd by montmorillonite and kaolinite was measured at 283, 298, and 308 K. Experiments were conducted at 2 g L{sup -3} clay suspension concentration in an ionic background of 50 mM NaClO{sup 4}. Sufficient metal ion concentrations were present to saturate the clays (92 and 5 cmol(c) kg{sup -1} for montmorillonite and kaolinite, respectively). The pH value of the suspensions was adjusted to 5.5 prior to initiation of the adsorption experiments. Kinetic studies conducted under aseptic conditions indicated that within 2 h the adsorption of the SSDOC by the days reached an equilibrium value.

Baham, J. [Oregon State Univ., Corvallis, OR (United States); Sposito, G. [Univ. of California, Berkeley, CA (United States)

1994-01-01

168

Spatial Variability of Dissolved Organic Carbon in Headwater Wetlands in Central Pennsylvania  

NASA Astrophysics Data System (ADS)

Dissolved organic carbon (DOC) is known to be of an important factor in many microbially mediated biochemical processes, such as denitrification, that occur in wetlands. The spatial variability of DOC within a wetland could impact the microbes that fuel these processes, which in turn can affect the ecosystem services provided by wetlands. However, the amount of spatial variability of DOC in wetlands is generally unknown. Furthermore, it is unknown how disturbance to wetlands can affect spatial variability of DOC. Previous research in central Pennsylvania headwater wetland soils has shown that wetlands with increased human disturbance had decreased heterogeneity in soil biochemistry. To address groundwater chemical variability 20 monitoring wells were installed in a random pattern in a 400 meter squared plot in a low-disturbance headwater wetland and a high-disturbance headwater wetland in central Pennsylvania. Water samples from these wells will be analyzed for DOC, dissolved inorganic carbon, nitrate, ammonia, and sulfate concentrations, as well as pH, conductivity, and temperature on a seasonal basis. It is hypothesized that there will be greater spatial variability of groundwater chemistry in the low disturbance wetland than the high disturbance wetland. This poster will present the initial data concerning DOC spatial variability in both the low and high impact headwater wetlands.

Reichert-Eberhardt, A. J.; Wardrop, D.; Boyer, E. W.

2011-12-01

169

Salmonid Bioassay of Supersaturated Dissolved Air in Water.  

National Technical Information Service (NTIS)

Tests were conducted in shallow (0.25 m) and deep (2.5 m) tanks of water at 10C with concentrations of dissolved atmospheric gas ranging from 100% to 127% of air saturation to determine the lethal and sublethal effects on juvenile fall chinook salmon (Onc...

E. Dawley B. Monk M. Schiewe F. Ossiander W. Ebel

1976-01-01

170

DISSOLVED CONCENTRATION LIMITS OF RADIOACTIVE ELEMENTS  

SciTech Connect

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

P. Bernot

2005-07-13

171

Vertical Variation in Dissolved Alkaline Phosphatase Activity in a Shallow Eutrophic Lake Determined in Reverse Micelles  

Microsoft Academic Search

We evaluated the feasibility of microencapsulating dissolved alkaline phosphatase of a water body into reverse micelle systems prepared by hexadecyltrimethylammonium bromide as a surfactant in cyclohexane and 1-butanol as co-surfactant. The dissolved alkaline phosphatase activity within the micelle was described, including its kinetic parameters and the effects of pH and temperature on catalytic activity in surface, overlying and interstitial water

Chunlei Song; Xiuyun Cao; Jianqiu Li; Qingman Li; Yiyong Zhou

2005-01-01

172

Fiber-optic dissolved oxygen and dissolved carbon dioxide sensors using fluorophores encapsulated in sol gel matrices  

NASA Astrophysics Data System (ADS)

Fiber optic chemical sensors (FOCS) for oxygen, dissolved oxygen (DO), and dissolved CO2 sensing using thin films of fluorophores encapsulated in sol-gel matrices were made and tested. The DO/O2 sensor used ruthenium(II) tris(4,7-diphenyl-1,10-phenanthroline) perchlorate (Ru(Ph 2Phen)Cl2) as the oxygen sensitive fluorophore and methyltrimethoxysilane (MTMS) sol-gel as the encapsulating matrix material. For the DCO2 sensor, 8-hydroxy-1,3,6-pyrenetrisulfonic acid trisodium salt (HPTS) co-doped with sodium bicarbonate was used as the DCO2 sensitive fluorophore-chemical system and diisobutoxy-alumino triethoxysilane (ASE) sol-gel was used as the encapsulating matrix material. It was found that oxygen quenches the excited state Ru(Ph2Phen)Cl 2 by diffusing through the MTMS matrix. Continuous excitation of Ru(Ph 2Phen)Cl2 during MTMS drying resulted in long, single exponential lifetimes of the metal complex and increased sensor sensitivity. When the sensor was field tested, it was found to have an excellent match compared to conventional titration method for determining dissolved oxygen concentrations and had fast response times. It was determined that this sensor measured the vapor pressure of oxygen rather than the absolute concentration of dissolved oxygen. For DCO2 sensing, it was found that the dynamic response of the senor could be tuned by varying the HPTS to NaHCO3 ratios. The sensor had fast response times compared to other fiber optic DCO 2 sensors reported which typically have response times of minutes.

Kwon, Hyeog-Chan

173

Dissolved organic carbon production by microbial populations in the Atlantic Ocean  

Microsoft Academic Search

Dissolved organic carbon (DOC) production by microbial populations was measured at 19 stations in the Atlantic Ocean to quantify the fraction of photoassimilated carbon that flows through the dissolved organic pool at basin scale and to assess the relationship between the percentage of DOC production, phytoplankton size structure, and rates of net community production. Experiments were conducted during four cruises

Eva Teira; María José Pazó; Pablo Serret; Emilio Fernández

2001-01-01

174

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

EPA Science Inventory

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

175

Dissolved solids do not induce diapause in the calanoid copepod Aglaodiaptomus leptopus  

Microsoft Academic Search

The effect of different total dissolved solid levels (TDS) was investigated as a predictor of diapause induction in the calanoid copepod Aglaodiaptomus leptopus. We collected adult copepods in the field and monitored seasonal changes in diapause egg production. We determined total dissolved solid levels, conductivity and temperature values from five ponds. In experimental work, females bearing clutches, collected from the

Steve S. Di Lonardo; Edward J. Maly

2004-01-01

176

Small Changes in pH Have Direct Effects on Marine Bacterial Community Composition: A Microcosm Approach  

PubMed Central

As the atmospheric CO2 concentration rises, more CO2 will dissolve in the oceans, leading to a reduction in pH. Effects of ocean acidification on bacterial communities have mainly been studied in biologically complex systems, in which indirect effects, mediated through food web interactions, come into play. These approaches come close to nature but suffer from low replication and neglect seasonality. To comprehensively investigate direct pH effects, we conducted highly-replicated laboratory acidification experiments with the natural bacterial community from Helgoland Roads (North Sea). Seasonal variability was accounted for by repeating the experiment four times (spring, summer, autumn, winter). Three dilution approaches were used to select for different ecological strategies, i.e. fast-growing or low-nutrient adapted bacteria. The pH levels investigated were in situ seawater pH (8.15–8.22), pH 7.82 and pH 7.67, representing the present-day situation and two acidification scenarios projected for the North Sea for the year 2100. In all seasons, both automated ribosomal intergenic spacer analysis and 16S ribosomal amplicon pyrosequencing revealed pH-dependent community shifts for two of the dilution approaches. Bacteria susceptible to changes in pH were different members of Gammaproteobacteria, Flavobacteriaceae, Rhodobacteraceae, Campylobacteraceae and further less abundant groups. Their specific response to reduced pH was often context-dependent. Bacterial abundance was not influenced by pH. Our findings suggest that already moderate changes in pH have the potential to cause compositional shifts, depending on the community assembly and environmental factors. By identifying pH-susceptible groups, this study provides insights for more directed, in-depth community analyses in large-scale and long-term experiments.

Krause, Evamaria; Wichels, Antje; Gimenez, Luis; Lunau, Mirko; Schilhabel, Markus B.; Gerdts, Gunnar

2012-01-01

177

Photochemical flocculation of terrestrial dissolved organic matter and iron  

NASA Astrophysics Data System (ADS)

Dissolved organic matter (DOM) rich water samples (Great Dismal Swamp, Virginia) were 0.1-?m filtered and UV-irradiated in a solar simulator for 30 days. During the irradiation, pH increased, particulate organic matter (POM) and particulate iron formed. After 30 days, 7% of the dissolved organic carbon (DOC) was converted to POC while 75% was remineralized. Approximately 87% of the iron was removed from the dissolved phase after 30 days, but iron did not flocculate until a major fraction of DOM was removed by photochemical degradation and flocculation (>10 days); thus, during the initial 10 days, there were sufficient organic ligands present or the pH was low enough to keep iron in solution. Nuclear magnetic resonance and Fourier transform infrared spectroscopies indicated that photochemically flocculated POM was more aliphatic than the residual non-flocculated DOM. Photochemically flocculated POM was also enriched in amide functionality, while carbohydrate-like material was resistant to both photochemical degradation and flocculation. Abiotic photochemical flocculation likely removes a significant fraction of terrestrial DOM from the upper water column between headwaters and the ocean, but has previously been ignored. Preliminary evidence suggests that this process may significantly impact the transport of DOM and POM in ocean margin environments including estuaries.

Helms, John R.; Mao, Jingdong; Schmidt-Rohr, Klaus; Abdulla, Hussain; Mopper, Kenneth

2013-11-01

178

Toxic and carcinogenic constituents in dissolvable tobacco ...  

Center for Biologics Evaluation and Research (CBER)

Text Version... Page 8. Tobacco-specific N-nitrosamines in Camel dissolvable products ... Page 9. Tobacco-specific N-nitrosamines in Camel dissolvable products ... More results from www.fda.gov/downloads/advisorycommittees/committeesmeetingmaterials

179

Dissolved Oxygen and Biochemical Oxygen Demand  

NSDL National Science Digital Library

This Environmental Protection Agency (EPA) website provides general information about dissolved oxygen, including what it is, sampling and equipment considerations, and sampling and analysis protocols. The site also features a chart of dissolved oxygen solubility as a function of temperature.

2010-03-02

180

Dissolved Oxygen and Biochemical Oxygen Demand  

NSDL National Science Digital Library

This EPA website provides general information about dissolved oxygen, including what it is, sampling and equipment considerations, and sampling and analysis protocols. The site also features a chart of dissolved oxygen solubility as a function of temperature.

Agency, U. S.

181

Delta-plutonium dissolving: A HAN process.  

National Technical Information Service (NTIS)

This report describes preliminary studies in the development of a nitrate-based method for dissolving delta-phase plutonium. The dissolving solution, a mixture of nitric acid, hydroxylammonium nitrate (HAN) and fluoride offers substantial advantages over ...

D. G. Karraker

1990-01-01

182

Carbon uptake in low dissolved inorganic carbon environments: the effect of limited carbon availability on photosynthetic organisms in thermal waters  

NASA Astrophysics Data System (ADS)

Photosynthesis is the primary carbon fixation process in thermal waters below 70°C, but some hydrothermal waters have extremely low dissolved inorganic carbon (DIC), potentially limiting the growth of inorganic carbon fixing organisms such as algae and cyanobacteria. To address the issue of how carbon is assimilated by phototrophs in these environments, we conducted experiments to compare inorganic carbon uptake mechanisms by two phylogenetically distinct organisms collected from geographically distinct carbon limited systems: the neutral pH geothermal waters of El Tatio, Chile, and the acidic geothermal waters of Tantalus Creek in Norris Geyser Basin, Yellowstone National Park. Discharge waters at El Tatio have low total DIC concentrations (2 to 6 ppm) found mainly as HCO3-; this is in contrast to even lower measured DIC values in Tantalus Creek (as low as 0.13 ppm) that, due to a measured pH of 2.5, exists primarily as CO2. Cyanobacteria and algae are innately physiologically plastic, and we are looking to explore the possibility that carbon limitation in these environments is extreme enough to challenge that plasticity and lead to a suite of carbon uptake adaptations. We hypothesize that these microorganisms utilize adaptive modes of Ci uptake that allow them to survive under these limiting conditions. Cyanobacteria (primarily Synechococcus spp.) isolated from El Tatio can utilize either passive CO2 uptake or active HCO3- uptake mechanisms, in contrast to the eukaryotic alga Cyanidium spp. from Tantalus Creek, which is restricted to an energy-dependent CO2 uptake mechanism. To test this hypothesis, we conducted pH drift experiments (Omelon et al., 2008) to examine changes in pH and [DIC] under a range of pH and [DIC] culture conditions. This work provides baseline information upon which we will begin to investigate the effects of low [DIC] on the growth of phototrophs collected from these and other less carbon limited systems.

Myers, K. D.; Omelon, C. R.; Bennett, P.

2010-12-01

183

Applications of a total dissolved gas pressure probe in ground water studies.  

PubMed

Measurements of dissolved gases have numerous applications in ground water hydrology, and it is now possible to measure the total dissolved gas pressure in situ using a probe. Dissolved gas pressure is measured by submerging a headspace volume with a gas-permeable membrane, allowing dissolved gases in the water to equilibrate with gases in the headspace, then measuring the pressure in the headspace with a pressure transducer. Total dissolved gas pressure (TGP) probes have many potential uses in ground water studies employing dissolved gases, including: (1) determining approximate excess air levels, which may provide information about the time and location of recharge; (2) screening wells for air contamination, which can compromise the accuracy of dissolved gas tracer techniques: (3) detecting a trapped gas phase, which can significantly reduce hydraulic conductivity and impede the transport of dissolved solutes and gases; (4) enabling the use of gas-filled passive diffusion samplers for determining accurate dissolved gas concentrations; and (5) determining relative concentrations of CH4 and CO2 when they are known to be highly abundant. Although TGP probes designed for surface water have been available for several years, TGP probes suitable for ground water applications have only recently become available. Herein we present what are, to our knowledge, the first reported ground water dissolved gas data collected using a TGP probe. We also explain the basic operating principles of these probes and discuss the potential applications listed. PMID:12873007

Manning, Andrew H; Solomon, D Kip; Sheldon, Amy L

184

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

NASA Astrophysics Data System (ADS)

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

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

2008-09-01

185

pH. Agricultural Lesson Plans.  

ERIC Educational Resources Information Center

This lesson plan is intended for use in conducting classes on the effect of pH on plant growth. Presented first are an attention step/problem statement and a series of questions and answers designed to convey general information about soil pH and its effect on plants. The following topics are among those discussed: acidity and alkalinity; the…

Southern Illinois Univ., Carbondale. Dept. of Agricultural Education and Mechanization.

186

pH. Agricultural Lesson Plans.  

ERIC Educational Resources Information Center

|This lesson plan is intended for use in conducting classes on the effect of pH on plant growth. Presented first are an attention step/problem statement and a series of questions and answers designed to convey general information about soil pH and its effect on plants. The following topics are among those discussed: acidity and alkalinity; the…

Southern Illinois Univ., Carbondale. Dept. of Agricultural Education and Mechanization.

187

Azomethine H colorimetric method for determining dissolved boron in water  

USGS Publications Warehouse

An automated colorimetric method for determining dissolved boron in water is described. The boron is complexed with azomethine H, which is readily available as the condensation product of H acid (8-amino-1-naphthol-3,6-disulfonic acid) and salicylaldehyde. The absorbance of the yellow complex formed is then measured colorimetrically at 410 nm. Interference effects from other dissolved species are minimized by the addition of diethylenetriaminepentaacetic acid (DTPA); however, iron, zinc, and bicarbonate interfere at concentrations above 400 ??g/L, 2000 ??g/L, and 200 mg/L, respectively. The bicarbonate interference can be eliminated by careful acidification of the sample with concentrated HCl to a pH between 5 and 6. Thirty samples per hour can be routinely analyzed over the range of from 10 to 400 ??g/L, boron.

Spencer, R. R.; Erdmann, D. E.

1979-01-01

188

Determination of dissolved aluminum in water samples  

USGS Publications Warehouse

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

Afifi, A. A.

1983-01-01

189

Tried and True: Inquiry-based dissolving  

NSDL National Science Digital Library

This project highlights a dissolving unit that was part of an eighth-grade, semester-long investigation into matter. During the dissolving unit, students explored the concepts of mixture, solution, dissolving, saturation, and conservation of mass. Dissolving is an advanced concept that involves the atomic structure of matter and the nature of chemical bonds. However, dissolving is also a common experience in studentsâ lives (e.g., when they mix sugar in lemonade). The unit allowed students to explore everyday materials in new ways, address common misconceptions, and pursue scientific discovery.

Benedis-Grab, Gregory; Petzoldt, Molly; Uribe, Lisbeth

2009-10-01

190

Recalcitrant dissolved organic carbon fractions.  

PubMed

Marine dissolved organic carbon (DOC) exhibits a spectrum of reactivity, from very fast turnover of the most bioavailable forms in the surface ocean to long-lived materials circulating within the ocean abyss. These disparate reactivities group DOC by fractions with distinctive functions in the cycling of carbon, ranging from support of the microbial loop to involvement in the biological pump to a hypothesized major source/sink of atmospheric CO(2) driving paleoclimate variability. Here, the major fractions constituting the global ocean's recalcitrant DOC pool are quantitatively and qualitatively characterized with reference to their roles in carbon biogeochemistry. A nomenclature for the fractions is proposed based on those roles. PMID:22881353

Hansell, Dennis A

2012-07-16

191

PROCESS OF DISSOLVING ZIRCONIUM ALLOYS  

DOEpatents

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

Shor, R.S.; Vogler, S.

1958-01-21

192

Bromide, Chloride, and Sulfate Concentrations, and Specific Conductance, Lake Texoma, Texas and Oklahoma, 2007-08  

USGS Publications Warehouse

The U.S. Geological Survey, in cooperation with the City of Dallas Water Utilities Division, collected water-quality data from 11 sites on Lake Texoma, a reservoir on the Texas-Oklahoma border, during April 2007-September 2008. At 10 of the sites, physical properties (depth, specific conductance, pH, temperature, dissolved oxygen, and alkalinity) were measured and samples were collected for analysis of selected dissolved constituents (bromide, calcium, magnesium, potassium, sodium, carbonate, bicarbonate, chloride, and sulfate); at one site, only physical properties were measured. The primary constituent of interest was bromide. Bromate can form when ozone is used to disinfect raw water containing bromide, and bromate is a suspected human carcinogen. Chloride and sulfate were of secondary interest. Only the analytical results for bromide, chloride, sulfate, and measured specific conductance are discussed in this report. Median dissolved bromide concentrations ranged from 0.28 to 0.60 milligrams per liter. The largest median dissolved bromide concentration (0.60 milligram per liter at site 11) was from the Red River arm of Lake Texoma. Dissolved bromide concentrations generally were larger in the Red River arm of Lake Texoma than in the Washita arm of the lake. Median dissolved chloride concentrations were largest in the Red River arm of Lake Texoma at site 11 (431 milligrams per liter) and smallest at site 8 (122 milligrams per liter) in the Washita arm. At site 11 in the Red River arm, the mean and median chloride concentrations exceeded the secondary maximum contaminant level of 300 milligrams per liter for chloride established by the 'Texas Surface Water Quality Standards' for surface-water bodies designated for the public water supply use. Median dissolved sulfate concentrations ranged from 182 milligrams per liter at site 4 in the Big Mineral arm to 246 milligrams per liter at site 11 in the Red River arm. None of the mean or median sulfate concentrations exceeded the secondary maximum contaminant level of 300 milligrams per liter. Median specific conductance measurements at sites ranged from 1,120 microsiemens per centimeter at site 8 in the Washita arm to 2,100 microsiemens per centimeter in the Red River arm. The spatial distribution of specific conductance in Lake Texoma was similar to that of bromide and chloride, with larger specific conductance values in the Red River arm compared to those in the Washita arm.

Baldys, Stanley, III

2009-01-01

193

Adsorption of Dissolved Metals in the Berkeley Pit using Thiol-Functionalized Self-Assembled Monolayers on Mesoporous Supports (Thiol-SAMMS)  

SciTech Connect

The Berkeley Pit in Butte, Montana, is heavily contaminated with dissolved metals. Adsorption and extraction of these metals can be accomplished through the use of a selective adsorbent. For this research, the adsorbent used was thiol-functionalized Self-Assembled Monolayers on Mesoporous Supports (thiol-SAMMS), which was developed at Pacific Northwest National Laboratory (PNNL). Thiol-SAMMS selectively binds to numerous types of dissolved metals. The objective of this research was to evaluate the loading and kinetics of aluminum, beryllium, copper, and zinc on thiol-SAMMS. For the loading tests, a series of Berkeley Pit water to thiol-SAMMS ratios (mL:g) were tested. These ratios were 1000:1, 500:1, 100:1, and 50:1. Berkeley Pit water is acidic (pH {approx} 2.5). This can affect the performance of SAMMS materials. Therefore, the effect of pH was evaluated by conducting parallel series of loading tests wherein the Berkeley Pit water was neutralized before or after addition of thiol-SAMMS, and a series of kinetics tests wherein the Berkeley Pit water was neutralized before addition of thiol-SAMMS for the first test and was not neutralized for the second test. For the kinetics tests, one Berkeley Pit water to thiol-SAMMS ratio was tested, which was 2000:1. The results of the loading and kinetics tests suggest that a significant decrease in dissolved metal concentration at Berkeley Pit could be realized through neutralization of Berkeley Pit water. Thiol-SAMMS technology has a limited application under the highly acidic conditions posed by the Berkeley Pit. However, thiol-SAMMS could provide a secondary remedial technique which would complete the remedial system and remove dissolved metals from the Berkeley Pit to below drinking water standards.

Betancourt, Amaury P.; Mattigod, Shas V.; Wellman, Dawn M.

2010-03-07

194

Effects of Low Dissolved Oxygen on Survival, Growth and Reproduction of 'Daphnia, Hyalella and Gammarus'.  

National Technical Information Service (NTIS)

Daphnia magna, Daphnia pulex, Hyalella azteca, and Gammarus lacustris were exposed to low dissolved oxygen concentrations in the laboratory. Acute and chronic exposures were conducted to develop data for use in the U.S. Environmental Protection Agency's (...

A. V. Nebeker S. T. Onjukka D. G. Stevens G. A. Chapman S. E. Dominguez

1993-01-01

195

Total Dissolved Gas Monitoring in Chum Salmon Spawning Gravel Below Bonneville Dam.  

National Technical Information Service (NTIS)

At the request of the U.S. Army Corps of Engineers (Portland District), Pacific Northwest National Laboratory (PNNL) conducted research to determine whether total dissolved gas concentrations are elevated in chum salmon redds during spring spill operation...

D. R. Geist E. M. Dawley E. V. Arntzen J. L. Panther

2007-01-01

196

Effect of Temperature and Dissolved Oxygen on Sediment-Water Nutrient Flux.  

National Technical Information Service (NTIS)

A series of experiments was conducted to determine the influence of water-column temperature and dissolved oxygen on sediment-water nutrient flux. Three nutrients were considered: ammonium nitrogen, nitrate nitrogen, and ortho phosphorus. Results of the e...

C. F. Cerco

1985-01-01

197

Effects of Low Dissolved Oxygen on Survival, Growth and Reproduction of 'Daphnia', 'Hyalella' and 'Gammarus'.  

National Technical Information Service (NTIS)

Daphnia magna, Daphnia pulex, Hyalella azteca, and Gammarus lacustris were exposed to low dissolved oxygen concentrations in the laboratory. Acute and chronic exposures were conducted to develop data for use in the U.S. Environmental Protection Agency's (...

A. V. Nebeker S. T. Onjukka D. G. Stevens G. A. Chapman S. E. Dominguez

1992-01-01

198

Fluvial dissolved inorganic C dynamics in the Western Amazonian basin: where does this carbon come from?  

NASA Astrophysics Data System (ADS)

The Amazon river and tributaries constitute globally a significant freshwater body and thus a source of atmospheric carbon dioxide. Aquatic carbon dioxide may originate from biological or physicochemical reprocessing of allochthonous dissolved, particulate or inorganic C (ecosystem-derived C, EDC) or it may derive from groundwater inputs of dissolved inorganic C through lithological weathering by soil-derived organic acids or by the dissolution of atmospheric carbon dioxide (minerogenic-derived C, MDC). In addition to quantifying and scaling catchment source import and export terms, accurate budgeting requires additional source differentiation. The significance of MDC is not usually considered by those assessing carbon dioxide efflux, yet differentiating MDC from EDC is crucial. For example, MDC should be less directly affected than EDC by future climatic change, becoming proportionally more important to fluvial carbon dioxide efflux in drought episodes. We are measuring the stable carbon isotopic ratio of dissolved inorganic C to determine the relative importance of MDC and EDC to total C loads in the Tambopata basin in Western Peru. This is an area little studied for C cycling, but important as the soils here are more nutrient rich than the remainder of the Amazon basin which is more studied. Our field station is in the Tambopata national park and since 2010 we have sampled four different river systems which vary in size and drainage characteristics: the Tambopata, (CA ~14,000 km sq.; ~30% of its in the Andes Mountains); La Torre (~2000 km sq.), New Colpita and Main Trail (both < 2 km sq. forest drainage but Main Trail only active in the wet season). Additionally the pH, conductivity, dissolved oxygen, water temperature and stage height have been monitored in these drainage systems where possible by logging at 15 minute intervals. Our data shows that there are statistically significant differences in carbon isotopic composition (ranging from -14 to -29 ‰) and [DIC] concentration (ranging from 0.1 to 0.7 mM) between rivers, which we interpret to represent differences in the MDC / EDC input. We will present this data and discuss in more detail local, seasonal and regional controls on composition, and its application in source contribution apportionment. Whilst we are utilising this DIC isotope tracer to differentiate the source of DIC (and ultimately effluxed carbon dioxide) this study shows the potential of utilising the DIC-C isotopic composition as a tracer of groundwater-surface water interaction.

Waldron, S.; Vihermaa, L. E.; Newton, J.; Krusche, A.; Salimon, C.

2012-04-01

199

Continuous measurement of dissolved sulfide in sewer systems.  

PubMed

Sulfides are particularly problematic in the sewage industry. Hydrogen sulfide causes corrosion of concrete infrastructure, is dangerous at high concentrations and is foul smelling at low concentrations. Despite the importance of sulfide monitoring there is no commercially available system to quantify sulfide in waste water. In this article we report on our use of an in situ spectrometer to quantify bisulfide in waste water and additional analysis with a pH probe to calculate total dissolved sulfide. Our results show it is possible to use existing commercially available and field proven sensors to measure sulfide to mg/l levels continuously with little operator intervention and no sample preparation. PMID:18309215

Sutherland-Stacey, L; Corrie, S; Neethling, A; Johnson, I; Gutierrez, O; Dexter, R; Yuan, Z; Keller, J; Hamilton, G

2008-01-01

200

A Study of Dissolved Gas Dynamics in Mixed Stream Electrolyzed Water  

Microsoft Academic Search

Supersaturated hydrogen and oxygen solutions of pH-neutral tap water were created through electrolysis and subsequently blended back together. The blended solution was monitored as a function of time with dissolved gas meters and time-lapse photography. While the pH of the blended anodic and cathodic electrolysis streams returned to neutral pH within seconds, the blended solution was observed to retain significantly

Kevin Klunder; Frederick A Hekman; Kenneth L Brown; Graham F Peaslee

2012-01-01

201

Biodegradable Materials and Their Effect on Dissolved Oxygen Levels  

NSDL National Science Digital Library

In this laboratory exercise, students will design and conduct an experiment to evaluate the effect of the presence of biodegradable materials on dissolved oxygen levels. They will come to understand the effect of biodegradable pollutants on water quality, design and conduct an experiment, interpret data, suggest additional studies, and preform serial dilutions. The students will discover that in aquatic systems, aerobic microorganisms will consume biodegradable material for energy, and in doing so will also take up oxygen from the environment as part of the cellular respiration process. They will also learn that scientists use dissolved oxygen levels as an indication of contamination by such pollutants as sewage, agricultural runoff, and organic industrial effluents. This activity has an accompanying teacher site with hints and more information. There are also links to several related sites.

202

METHOD OF DISSOLVING REFRACTORY ALLOYS  

DOEpatents

This patent relates to the dissolution of alloys of uranium with zirconium, thorium, molybdenum, or niobium. The alloy is contacted with an anhydrous solution of mercuric chloride in a low-molecular-weight monohydric alcohol to produce a mercury-containing alcohol slurry. The slurry is then converted to an aqueous system by adding water and driving off the alcohol. The resulting aqueous slurry is electrolyzed in the presence of a mercury cathode to remove the mercury and produce a uranium-bearing aqueous solution. This process is useful for dissolving irradiated nuclear reactor fuels for radiochemical reprocessing by solvent extraction. In addition, zirconium-alloy cladding is selectively removed from uranium dioxide fuel compacts by this means. (AEC)

Helton, D.M.; Savolainen, J.K.

1963-04-23

203

Bench-scale evaluation of ferrous iron oxidation kinetics in drinking water: Effect of corrosion control and dissolved organic matter.  

PubMed

Corrosion control strategies are important for many utilities in maintaining water quality from the water treatment plant to the customers' tap. In drinking water with low alkalinity, water quality can become significantly degraded in iron-based pipes if water utilities are not diligent in maintaining proper corrosion control. This article reports on experiments conducted in bicarbonate buffered (5 mg-C/L) synthetic water to determine the effects of corrosion control (pH and phosphate) and dissolved organic matter (DOM) on the rate constants of the Fe(II) oxidation process. A factorial design approach elucidated that pH (P = 0.007, contribution: 42.5%) and phosphate (P = 0.025, contribution: 22.7%) were the statistically significant factors in the Fe(II) oxidation process at a 95% confidence level. The comprehensive study revealed a significant dependency relationship between the Fe(II) oxidation rate constants (k) and phosphate-to- Fe(II) mole ratio. At pH 6.5, the optimum mole ratio was found to be 0.3 to reduce the k values. Conversely, the k values were observed to increase for the phosphate-to- Fe(II) mole ratio >1. The factorial design approach revealed that chlorine and DOM for the designated dosages did not cause a statistically significant (?=0.05, P>0.05)change in rate constants. However, an increment of the chlorine to ferrous iron mole ratio by a factor of ?2.5 resulted in an increase k values by a factor of ?10. This study conclusively demonstrated that the lowest Fe(II) oxidation rate constant was obtained under low pH conditions (pH ? 6.5), with chlorine doses less than 2.2 mg/L and with a phosphate-to-Fe(II) mole ratio?0.3 in the iron water systems. PMID:24117078

Rahman, Safiur; Gagnon, Graham A

2014-01-01

204

Progress in dissolving modified LEU Cintichem targets  

SciTech Connect

A process is under development to use low-enriched uranium (LEU) metal targets for production of {sup 99}Mo. The first step is to dissolve the irradiated foil. In past work, this has been done by heating a closed (sealed) vessel containing the foil and a solution of nitric and sulfuric acids. In this work, the authors have demonstrated that (1) the dissolver solution can contain nitric acid alone, (2) uranium dioxide is also dissolved by nitric acid alone, and (3) barrier metals of Cu, Fe, or Ni on the U foil are also dissolved by nitric acid. Changes to the dissolver design and operation needed to accommodate the uranium foil are discussed, including (1) simple operations that are easy to do in a remote-maintenance facility, (2) heat removal from the irradiated LEU foil, and (3) cold trap operation with high dissolver pressures.

Leonard, R.A.; Chen, L.; Mertz, C.J.; Vandegrift, G.F. [Argonne National Lab., IL (United States). Chemical Technology Div.

1996-12-31

205

Comparison of zinc complexation properties of dissolved natural organic matter from different surface waters  

Microsoft Academic Search

The zinc binding characteristics of natural organic matter (NOM) from several representative surface waters were studied and compared. NOM samples were concentrated by reverse osmosis. The samples were treated in the laboratory to remove trace metals. Square wave anodic stripping voltammetry (SWASV) was used to study zinc complexing properties of those NOM samples at fixed pH, ionic strength, and dissolved

Tao Cheng; Herbert E. Allen

2006-01-01

206

Adsorption of dissolved organics in lake water by aluminum oxide. Effect of molecular weight  

Microsoft Academic Search

Dissolved organic compounds in a Swiss lake were fractionated into three molecular size classes by gel exclusion chromatography, and adsorption of each fraction on colloidal alumina was studied as a function of pH. Organic compounds with molecular weight (mr) greater than 1000 formed strong complexes with the alumina surface, but low molecular weight compounds were weakly adsorbed. Electrophoretic mobility measurements

James A. Davis; Rolf Gloor

1981-01-01

207

Dissolved phosphorus concentrations in a natural salt-marsh of Delaware  

Microsoft Academic Search

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

Robert J. Reimold; Franklin C. Daiber

1970-01-01

208

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

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

209

Electrical conductivity: a useful technique in teaching geomorphology  

Microsoft Academic Search

The electrical conductivity of a water sample is proportional to its total dissolved solids content. Since conductivity can be measured easily and quickly by commercially available meters it is admirably suited to geomorphological field work on the dissolved solids content of natural waters. The technique lends itself to exercises involving work in the field, the classroom and the laboratory and

Brian Finlayson

1979-01-01

210

The Role of Dissolved Organic Carbon, Dissolved Organic Nitrogen, and Dissolved Inorganic Nitrogen in a Tropical Wet Forest Ecosystem  

Microsoft Academic Search

Although tropical wet forests play an important role in the global carbon (C) and nitrogen (N) cycles, little is known about the origin, composition, and fate of dissolved organic C (DOC) and N (DON) in these ecosystems. We quantified and characterized fluxes of DOC, DON, and dissolved inorganic N (DIN) in throughfall, litter leachate, and soil solution of an old-growth

Luitgard Schwendenmann; Edzo Veldkamp

2005-01-01

211

pH Game  

NSDL National Science Digital Library

The purpose of this resource is to teach students about the acidity levels of liquids and other substances around their school so they understand what pH levels tell us about the environment. Students will create mixtures of water samples, soil samples, plants and other natural materials to better understand the importance of pH levels.

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

2003-08-01

212

Quantification and characterization of dissolved organic nitrogen in wastewater effluents by electrodialysis treatment followed by size-exclusion chromatography with nitrogen detection.  

PubMed

Dissolved organic nitrogen (DON) can act as a precursor of nitrogenous disinfection byproducts during oxidative water treatment. Quantification and characterization of DON are still challenging for waters with high concentrations of dissolved inorganic nitrogen (DIN, including ammonia, nitrate and nitrite) relative to total dissolved nitrogen (TDN) due to the cumulative analytical errors of independently measured nitrogen species (i.e., DON = TDN - NO2(-) - NO3(-) - NH4(+)/NH3) and interference of DIN species to TDN quantification. In this study, a novel electrodialysis (ED)-based treatment for selective DIN removal was developed and optimized with respect to type of ion-exchange membrane, sample pH, and ED duration. The optimized ED method was then coupled with size-exclusion chromatography with organic carbon, UV, and nitrogen detection (SEC-OCD-ND) for advanced DON analysis in wastewater effluents. Among the tested ion-exchange membranes, the PC-AR anion- and CMT cation-exchange membranes showed the lowest DOC loss (1-7%) during ED treatment of a wastewater effluent at ambient pH (8.0). A good correlation was found between the decrease of the DIN/TDN ratio and conductivity. Therefore, conductivity has been adopted as a convenient way to determine the optimal duration of the ED treatment. In the pH range of 7.0-8.3, ED treatment of various wastewater effluents with the PC-AR/CMT membranes showed that the relative residual conductivity could be reduced to less than 0.50 (DIN removal >90%; DIN/TDN ratio ?0.60) with lower DOC losses (6%) than the previous dialysis and nanofiltration methods (DOC loss >10%). In addition, the ED method is shorter (0.5 h) than the previous methods (>1-24 h). The relative residual conductivity was further reduced to ?0.20 (DIN removal >95%; DIN/TDN ratio ?0.35) by increasing the ED duration to 0.7 h (DOC loss = 8%) for analysis by SEC-OCD-ND, which provided new information on distribution and ratio of organic carbon and nitrogen in different molecular weight fractions of effluent organic matter. PMID:23916154

Chon, Kangmin; Lee, Yunho; Traber, Jacqueline; von Gunten, Urs

2013-06-20

213

A review of dissolved gas supersaturation literature  

Microsoft Academic Search

Gas bubble disease in a condition that affects aquatic animals residing in fresh or marine waters that are supersaturated with atmospheric gases. The majority of research concerning dissolved gas supersaturation has been stimulated by a serious supersaturation problem that was first observed in the Columbia and Snake river systems in 1970. Available literature dealing with dissolved gas supersaturation and recorded

DON E. WEITKAMP; MAX KATZ

1980-01-01

214

Investigating Students' Understanding of the Dissolving Process  

ERIC Educational Resources Information Center

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

Naah, Basil M.; Sanger, Michael J.

2013-01-01

215

Investigating Students' Understanding of the Dissolving Process  

ERIC Educational Resources Information Center

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

Naah, Basil M.; Sanger, Michael J.

2013-01-01

216

Application of dissolvable layered double hydroxides as sorbent in dispersive solid-phase extraction and extraction by co-precipitation for the determination of aromatic acid anions.  

PubMed

Three types of magnesium-aluminum layered double hydroxides were synthesized and employed as solid-phase extraction (SPE) sorbents to extract several aromatic acids (protocatechuic acid, mandelic acid, phthalic acid, benzoic acid, and salicylic acid) from aqueous samples. An interesting feature of these sorbents is that they dissolve when the pH of the solution is lower than 4. Thus, the analyte elution step, as needed in conventional sorbent-based extraction, was obviated by dissolving the sorbent in acid after extraction and separation from the sample solution. The extract was then directly injected into a high-performance liquid chromatography-ultraviolet detection system for analysis. In the key adsorption process, both dispersive SPE and co-precipitation extraction with the sorbents were conducted and experimental parameters such as pH, temperature, and extraction time were optimized. The results showed that both extraction methods provided low limits of detection (0.03-1.47 ?g/L) and good linearity (r(2) > 0.9903). The optimized extraction conditions were applied to human urine and sports drink samples. This new and interesting extraction approach was demonstrated to be a fast and efficient procedure for the extraction of organic anions from aqueous samples. PMID:23855757

Tang, Sheng; Lee, Hian Kee

2013-07-29

217

Boiling of Water Droplets Containing Dissolved Salts  

NASA Astrophysics Data System (ADS)

We conducted experiments on the effect of dissolving three different salts (sodium chloride, sodium sulphate and magnesium sulphate) in water droplets boiling on a hot stainless steel surface. Substrate temperatures were varied from 100^oC to 300^oC. We photographed droplets as they evaporated, and recorded their evaporation time. At surface temperatures that were too low to initiate nucleate boiling, all three salts were found to reduce the evaporation rate since they lower the vapor pressure of water. In the nucleate boiling regime, sodium sulphate and magnesium sulphate enhanced heat transfer because they prevented coalescence of vapor bubbles and produced foaming in the droplet, significantly reducing droplet lifetime. The ability of salts to prevent coalescence is linked to their ionic strength: electric charge accumulated on the surfaces of bubbles produces a repulsive force, preventing them from approaching each other. Sodium chloride, which has a low ionic strength, had little effect on droplet evaporation. Low concentrations (<0.3 mol/liter) of magnesium sulphate enhanced droplet boiling by promoting foaming. However high concentrations (>0.3 mol/liter) reduce droplet evaporation rates by increasing the vapour pressure of water.

Cui, Qiang; Chandra, Sanjeev; McCahan, Susan

2000-11-01

218

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

SciTech Connect

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

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

1991-10-01

219

Urine pH  

MedlinePLUS

... Drugs that can decrease urine pH include ammonium chloride, thiazide diuretics, and methenamine mandelate. Eat a normal, ... is associated with xanthine, cystine, uric acid , and calcium oxalate stones. Alkaline urine is associated with calcium ...

220

A controlled field experiment on groundwater contamination by a multicomponent DNAPL: dissolved-plume retardation  

Microsoft Academic Search

A natural gradient emplaced-source (ES) controlled field experiment was conducted at the Borden aquifer research site, Ontario, to study the transport of dissolved plumes emanating from residual dense nonaqueous-phase liquid (DNAPL) source zones. The specific objective of the work presented here is to determine the effects of solute and co-solute concentrations on sorption and retardation of dissolved chlorinated solvent-contaminant plumes.

Michael O Rivett; Richelle M Allen-King

2003-01-01

221

Experimental evaluation of NO\\/sub x\\/ and Iâ retention during the scrubbing of dissolver off-gas  

Microsoft Academic Search

As part of the Consolidated Fuel Reprocessing Program, this study was conducted at the Oak Ridge National Laboratory to investigate the removal of nitrogen oxides from simulated dissolver off-gas, a gas blended to simulate that arising from the dissolution of nuclear fuel in reprocessing operations. Dissolver off-gas contains large quantities of water vapor and nitrogen oxides and much smaller quantities

R. M. Counce; W. S. Groenier; R. T. Jubin

1986-01-01

222

Effects of microbial activity on the d18O of dissolved inorganic phosphate and textural features of synthetic apatites  

Microsoft Academic Search

Laboratory growth experiments were conducted to investigate the oxygen isotope effects associated with bacterial metabolism of phosphatic compounds commonly available in nature. The observed oxygen isotope fractionations suggest complex patterns of exchange between dissolved inorganic phosphate (Pi) and water, and significant circulation of P i between intracellular and extracellular locations with extensive recycling of the dissolved Pi pool, even at

R. E. BLAKE; J. R. O'NEIL; G. A. GARCIA

1998-01-01

223

Use of a Ferrous Sulfate - Sodium Dithionite Blend to Treat a Dissolved Phase Cr(VI) Plume  

EPA Science Inventory

A field study was conducted to evaluate the use of a combination of sodium dithionite and ferrous sulfate in creating an in situ redox zone for treatment of a dissolved phase Cr(VI) plume at a former industrial site. The reductant blend was injected into the path of a dissolved ...

224

Effects of staged vessels on dissolver performance. Internal R and D final report. [Staged reactors at different temperatures  

Microsoft Academic Search

This report summarizes the work conducted under ICRC's Program Area 12.1.7, on the effects of staged vessels on dissolver performance. Results showed that operating the dissolvers in series decreased the preasphaltenes yield. From a process viewpoint, this should increase the amount of recoverable product, because recovery from the plant's critical solvent deashing unit will increase when preasphaltene content decreases. Neither

R. Sivasubramanian; E. N. Givens

1983-01-01

225

Acidogenesis of dairy wastewater at various pH levels  

Microsoft Academic Search

Continuous experiments were conducted to study the influence of pH in the range 4.0-6.5 on the acidification of dairy wastewater at 37°C with 12 hours of hydraulic retention in an upflow reactor. Results showed that degradation of dairy pollutants increased with pH from pH 4.0 to 5.5. At pH 5.5, 95% of carbohydrate, 82% of protein and 41% of lipid

H.-Q. Yu; H. H. P. Fang

2002-01-01

226

Dynamics and Biodegradability of Chromophoric Dissolved Organic Matter in a Severely Polluted River  

NASA Astrophysics Data System (ADS)

The 70-kilometer long Kishon River is one of Israel's largest rivers. Its annual discharge may vary substantially, e.g. between 47 and 10 million m3. The lower section of the river has been severely polluted for dozens of years, by industrial effluents containing heavy metals, radionuclides, nutrients, and diverse organic contaminants. The total volume of effluents discharged from the plants into the river stream may contribute as much as 30% of the total water volume. Dissolved organic matter (DOM) and specifically its chromophoric components (CDOM) including humic-like and proteinous substances may form water-soluble complexes with multiple organic and inorganic pollutants and, thus, enhance their release from the sediments and their mobility. The volatility of pollutants, their bioavailability, toxicity and potential to undergo bio-, abiotic and photodegradation may be affected by interactions with CDOM. Therefore, the dynamics of CDOM is important for understanding the fate of pollutants in aquatic environments. In this study, we intended (i) to characterize the seasonal and spatial variability of CDOM at the most contaminated lower section of the Kishon River and (ii) to assess the impact of biodegradation, dilution by seawater and contribution of discharged effluents on the overall dynamics of DOM and CDOM. For this purpose, water was sampled during 11 months at 8 locations distributed along Lower Kishon River. Samples were characterized for concentrations of dissolved organic carbon (DOC), UV- absorbance at 254 nm, electrical-conductivity, pH, concentration of dissolved oxygen and excitation emission matrices (EEM) of fluorescence. Parallel factor analysis of EEM enabled quantifying two major groups of riverine fluorescent CDOM: humic-like substances and components spectrally similar to those associated with phytoplankton productivity. CDOM (including fluorescent matter and components absorbing light at 254 nm) was found resistant to biodegradation by riverine microorganisms. The fraction of easily degradable riverine DOM that was not included in the CDOM was estimated to be between 8 and 26% of the overall DOC. The variability in DOM and CDOM composition was strongly affected by dilution with seawater. Approaching the estuary, the DOM in the Kishon River becomes depleted in CDOM. At the same time, the UV-active components become relatively enriched in fluorescent matter. It was hypothesized that the concentration of humic-like substances may increase in the river due to DOM transformation. Effluent discharge from multiple industrial sites along the river did not result in a distinct increase in concentrations of CDOM components absorbing light at 254 nm or fluorescent humic-like substances. However, an increase in the fluorescent CDOM associated with phytoplankton productivity was observed in the central section of Lower Kishon River, probably linked to an increase of nutrients supply originating from discharged effluents, which enhanced biological activity. Thus, different processes appear to influence the concentrations of two major groups of fluorescent riverine CDOM. The collected data showed significant correlations between concentration of dissolved oxygen, pH and UV- absorbance at 254 nm which may suggest that as the content of aromatic components increases, the oxygen demand for DOM biodegradation decreases, since DOM is enriched in biodegradation-resistant substances. The different dynamics of DOC and CDOM as observed in this study needs to be considered when modeling the impact of DOM on the fate of pollutants in riverine ecosystems.

Borisover, Mikhail; Laor, Yael; Saadi, Ibrahim; Lado, Marcos; Bukhanovsky, Nadezhda

2010-05-01

227

INDUSTRIAL SCALE-UP OF PH CONTROLLED LIQUID HOT WATER PRETREATMENT OF CORN FIBER FOR FUEL ETHANOL PRODUCTION  

Technology Transfer Automated Retrieval System (TEKTRAN)

The pretreatment of cellulose in corn fiber by liquid hot water at 160 deg C and a pH above 4.0 dissolves 50% of the fiber in 20 min. The preatment also enables the subsequent complete enzymatic hydrolysis of the remaining polysaccharides to monosaccharides. The carbohydrates dissolved by the pret...

228

Diffusive gradients in thin films technique equipped with a mixed binding gel for simultaneous measurements of dissolved reactive phosphorus and dissolved iron.  

PubMed

Developing a technique to track the release of phosphorus (P) and iron (Fe) simultaneously in sediments would be very useful in deepening our understanding of the internal loading process of P coupled with Fe cycling in aquatic systems. In this study, a new technique was established to measure simultaneously the dissolved reactive P (DRP) and dissolved Fe primarily released from sediment solids based on the diffusive gradients in thin films (DGT) theory. A mixed binding gel (ZrO-Chelex gel) used for assembling DGT was developed for simultaneous uptake of DRP and dissolved Fe(II) using amorphous zirconium hydroxide (Zr-oxide) and Chelex-100 resin as binding agents. Simultaneous measurements of DRP and dissolved Fe(II) with the ZrO-Chelex DGT were validated in solution and were independent of solution pH and ionic strength in normal environments. The capacities of the ZrO-Chelex DGT for measurements of DRP and dissolved Fe(II) were 90 ?g P cm(-2) and 75 ?g Fe cm(-2), with the latter being greater than that (45 ?g Fe cm(-2)) observed with the Chelex-100 resin DGT commonly used in DGT measurements of metals. Microcosm experiments further confirmed the feasibility of the ZrO-Chelex DGT for simultaneous measurement of P and Fe in sediments, with a higher concentration of Fe being measured due to this method's higher capacity compared with the Chelex-100 resin DGT. PMID:23941608

Xu, Di; Chen, Yifei; Ding, Shiming; Sun, Qin; Wang, Yan; Zhang, Chaosheng

2013-08-27

229

A novel paper pH sensor based on polypyrrole  

Microsoft Academic Search

A novel versatile paper pH sensor has been fabricated from conducting polypyrrole (PPy) supported on a paper substrate. The response of this paper pH sensor is based on the conductivity change of PPy under different pH environments, which is monitored by measuring the resistance of the sensor under dry conditions via a specially designed four-point probe connected to a multimeter.

Fang Yue; Tan Swee Ngin; Ge Hailin

1996-01-01

230

pH sensors based on hydrogenated diamond surfaces  

Microsoft Academic Search

We report on the operation of ungated surface conductive diamond devices in electrolytic solutions. The effect of electrolyte pH on the channel conductivity is studied in detail. It is shown that fully hydrogen terminated diamond surfaces are not pH sensitive. However, a pronounced pH sensitivity arises after a mild surface oxidation by ozone. We propose that charged ions from the

Jose A. Garrido; Stefan Kuch; Martin Stutzmann; Oliver A. Williams; R. B. Jackmann

2005-01-01

231

PhD Students' Work Conditions and Study Environment in University- and Industry-Based PhD Programmes  

ERIC Educational Resources Information Center

|During the last 10 years, new models of funding and training PhD students have been established in Denmark in order to integrate industry into the entire PhD education. Several programmes have been conducted where it is possible to co-finance PhD scholarships or to become an employee as an industrial PhD in a company. An important question is…

Kolmos, A.; Kofoed, L. B.; Du, X. Y.

2008-01-01

232

Analysis of karst hydrodynamics through comparison of dissolved and suspended solids' transport  

Microsoft Academic Search

In karst systems, rain events often result in a decrease of the conductivity (a tracer of dissolved phase transport) and an increase in turbidity (a tracer of suspended solids transport) at wells and springs. This study shows that the comparison of suspended solids and solute transport by the coupled approach of T–C curves (Turbidity–Conductivity) and autocorrelations gives evidence of the

Danièle Valdes; Jean-Paul Dupont; Nicolas Massei; Benoît Laignel; Joël Rodet

2005-01-01

233

Laboratory and marine study of photoluminescent sensors of oxygen dissolved in seawater  

NASA Astrophysics Data System (ADS)

The laboratory and marine study of photoluminescent sensors developed at the TsAGI has been conducted to create a highly sensitivity gauge of the oxygen dissolved in seawater. The advantages of the photoluminescent gauge over the electrochemical ones are the following: zero sensitivity to electromagnetic fields, the pH of the water, and the hydrogen sulphide and ions of heavy metals in the water; zero oxygen consumption; and no need for the water to be pumped through the device. A breadboard model of the photoluminescent gauge with LED excitation of the luminescence has been built. The laboratory tests of the model demonstrated the accuracy of the gauge to be as high as 0.05 ml/1 in air at a response time of 0.3 s for 63% relaxation. Comparative field tests of the breadboard model and the SBE 43 electrochemical oxygen gauge (Sea-Bird Electronics Corp.) have shown good agreement of the estimates of the oxygen content in the water and clarified the prospects of model’s performance improvement.

Vlasov, V. L.; Konovalov, B. V.; Mosharov, V. E.; Radchenko, V. N.; Khanaev, S. A.; Khlebnikov, D. V.

2010-02-01

234

The Effect of Gastric pH on the Absorption of Controlled-Release Theophylline Dosage Forms in Humans  

Microsoft Academic Search

The bioavailability of three marketed controlled-release dosage forms and a reference solution of theophylline was studied in eight subjects with normal gastric fluid acidity and seven subjects who were achlorhydric. Gastric pH was monitored with a Heidelberg capsule. One of the controlled-release dosage forms dissolved more rapidly in vitro when exposed to acid conditions, one dissolved more rapidly in pH

Marvin C. Meyer; Arthur B. Straughn; Eric J. Jarvi; George C. Wood; Vijaykumar I. Vashi; Paul Hepp; John Hunt

1993-01-01

235

Artificial neural network modeling of dissolved oxygen in the Heihe River, Northwestern China.  

PubMed

Identification and quantification of dissolved oxygen (DO) profiles of river is one of the primary concerns for water resources managers. In this research, an artificial neural network (ANN) was developed to simulate the DO concentrations in the Heihe River, Northwestern China. A three-layer back-propagation ANN was used with the Bayesian regularization training algorithm. The input variables of the neural network were pH, electrical conductivity, chloride (Cl(-)), calcium (Ca(2+)), total alkalinity, total hardness, nitrate nitrogen (NO3-N), and ammonical nitrogen (NH4-N). The ANN structure with 14 hidden neurons obtained the best selection. By making comparison between the results of the ANN model and the measured data on the basis of correlation coefficient (r) and root mean square error (RMSE), a good model-fitting DO values indicated the effectiveness of neural network model. It is found that the coefficient of correlation (r) values for the training, validation, and test sets were 0.9654, 0.9841, and 0.9680, respectively, and the respective values of RMSE for the training, validation, and test sets were 0.4272, 0.3667, and 0.4570, respectively. Sensitivity analysis was used to determine the influence of input variables on the dependent variable. The most effective inputs were determined as pH, NO3-N, NH4-N, and Ca(2+). Cl(-) was found to be least effective variables on the proposed model. The identified ANN model can be used to simulate the water quality parameters. PMID:23001527

Wen, Xiaohu; Fang, Jing; Diao, Meina; Zhang, Chuanqi

2012-09-22

236

Removing Dissolved Inorganic Contaminants from Water.  

National Technical Information Service (NTIS)

Dissolved inorganic contaminants in water can be cationic, anionic, or neutral forms of ions, atoms, or molecules of any element in the periodic table. The article describes the physicochemical treatment processes typically used to remove the more common ...

D. Clifford T. J. Sorg S. Subramonian

1986-01-01

237

College Students' Awareness and Perceptions of Dissolvable ...  

Center for Biologics Evaluation and Research (CBER)

Text VersionCollege Students' Awareness and Perceptions of Dissolvable Tobacco Products ... o Risk Perception ... To measure trajectories of SLT use among ... More results from www.fda.gov/downloads/advisorycommittees/committeesmeetingmaterials

238

EXPERIMENTAL DETERMINATION OF UO2(cr) DISSOLUTION KINETICS: EFFECTS OF SOLUTION SATURATION STATE and pH  

SciTech Connect

To evaluate the release of uranium from natural ore deposits, spent nuclear fuel repositories, and REDOX permeable reactive barriers, knowledge of the fundamental reaction kinetics associated with the dissolution of uranium dioxide is necessary. Dissolution of crystalline uranium (IV) dioxide under environmental conditions has been studied for four decades but a cardinal gap in the published literature is the effect of pH and solution saturation state on UO2(cr) dissolution. To resolve these inconsistencies, UO2 dissolution experiments have been conducted under oxic conditions using the single-pass flow-through system. Experiments were conducted as a function of total dissolved carbonate ([CO3-2]T) from 0.001 to 0.1 M; pH from 7.5 to 11.1; ratio of flow-through rate (q) to specific surface area (S), constant ionic strength (I) = 0.1 M, and temperatures (T) from 23 to 60 C utilizing both powder and monolithic specimens. The results show that UO2 dissolution varies as a function of the ratio q/S and temperature. At values of log10 q/S > -7.0, UO2 dissolution becomes invariant with respect to q/S, which can be interpreted as evidence for dissolution at the forward rate of reaction. The data collected in these experiments show the rate of UO2 dissolution increased by an order of magnitude with a 30? increase in temperature. The results also show the overall dissolution rate will increase with an increase in pH and decrease as the dissolved uranium concentration approaches saturation with respect to secondary reaction products. Thus, as the value of the reaction quotient, Q, approaches equilibrium, K, (with respect to a potential secondary phase) the dissolution rate decreases. This decrease in dissolution rate was also observed when comparing measured UO2 dissolution rates from static tests where r = 1.7 ?0.14 ? 10-8 mol m 2 s-1 to the rate for flow-through reactors where r = 3.1 ?1.2 ? 10-7 mol m-2 s-1. Thus, using traditional static test methods can result in an underestimation of the true forward rate of UO2(cr) dissolution. These results illustrate the release of uranium from UO2 in the natural environment will be controlled by pH, solution saturation state, and the concentration of dissolved carbonate.

Pierce, Eric M.; Icenhower, Jonathan P.; Serne, R JEFFREY.; Catalano, Jeffrey G.

2005-09-01

239

Experimental determination of UO2(cr) dissolution kinetics: Effects of solution saturation state and pH  

NASA Astrophysics Data System (ADS)

To evaluate the release of uranium from natural ore deposits, spent nuclear fuel repositories, and REDOX permeable reactive barriers (PRB), knowledge of the fundamental reaction kinetics associated with the dissolution of uranium dioxide is necessary. Dissolution of crystalline uranium (IV) dioxide under environmental conditions has been studied for four decades but a cardinal gap in the published literature is the effect of pH and solution saturation state on UO2(cr) dissolution. To resolve inconsistencies, UO2 dissolution experiments have been conducted under oxic conditions using the single-pass flow-through system. Experiments were conducted as a function of total dissolved carbonate ([CO3-3]) from 0.001 to 0.1 M; pH from 7.5 to 11.1; ratio of flow-through rate (q) to specific surface area (S), constant ionic strength (I) = 0.1 M, and temperatures (T) from 23 to 60 °C utilizing both powder and monolithic specimens. The results show that UO2 dissolution varies as a function of the ratio q/S and temperature. At values of log10 q/S > -7.0, UO2 dissolution becomes invariant with respect to q/S, which can be interpreted as evidence for dissolution at the forward rate of reaction. The data collected in these experiments show the rate of UO2 dissolution increased by an order of magnitude with a 30 °C increase in temperature. The results also show the overall dissolution rate increases with an increase in pH and decreases as the dissolved uranium concentration approaches saturation with respect to secondary reaction products. Thus, as the value of the reaction quotient, Q, approaches equilibrium, K, (with respect to a potential secondary phase) the dissolution rate decreases. This decrease in dissolution rate (r) was also observed when comparing measured UO2 dissolution rates from static tests where r = 1.7 ± 0.14 × 10-8 mol m-2 s-1 to the rate for flow-through reactors where r = 3.1 ± 1.2 × 10-7 mol m-2 s-1. Thus, using traditional static test methods can result in an underestimation of the true forward rate of UO2(cr) dissolution. These results illustrate the importance of pH, solution saturation state, and the concentration of dissolved carbonate on the release of uranium from UO2 in the natural environment.

Pierce, E. M.; Icenhower, J. P.; Serne, R. J.; Catalano, J. G.

2005-10-01

240

Sequestration of Dissolved CO2 in the Oriskany Formation  

SciTech Connect

Experiments were conducted to determine the solubility of CO2 in a natural brine solution of the Oriskany formation under elevated temperature and pressure conditions. These data were collected at temperatures of 22 and 75 °C and pressures between 100 and 450 bar. Experimentally determined data were compared with CO2 solubility predictions using a model developed by Duan and Sun (Chem. Geol. 2003, 193, 257-271). Model results compare well with Oriskany brine CO2 solubility data collected experimentally, suggesting that the Duan and Sun model is a reliable tool for estimating solution CO2 capacity in high salinity aquifers in the temperature and pressure range evaluated. The capacity for the Oriskany formation to sequester dissolved CO2 was calculated using results of the solubility models, estimation of the density of CO2 saturated brine, and available geographic information system (GIS) information on the formation depth and thickness. Results indicate that the Oriskany formation can hold approximately 0.36 gigatonnes of dissolved CO2 if the full basin is considered. When only the region where supercritical CO2 can exist (temperatures greater than 31° C and pressures greater than 74 bar) is considered, the capacity of the Oriskany formation to sequester dissolved CO2 is 0.31 gigatonnes. The capacity estimate considering the potential to sequester free-phase supercritical CO2 if brine were displaced from formation pore space is 8.8 gigatonnes in the Oriskany formation.

Dilmore, R.M.; Allen, D.E. (Salem State College, Salem, MA); McCarthy-Jones, J.R.; Hedges, S.W.; Soong, Yee

2008-04-15

241

Dissolved gas tracers in groundwater: Simplified injection, sampling, and analysis  

NASA Astrophysics Data System (ADS)

Simplified injection, sampling, and analytical procedures using dissolved gases as groundwater tracers are presented for use in saturated conditions at both the laboratory and field scales. The injection of gases into the groundwater is accomplished by allowing the gas to diffuse through semipermeable tubing, minimizing the formation of bubbles that could modify the hydraulic properties around the well. We have simplified the collection of dissolved gases by developing a passive in situ headspace sampler the employs a semipermeable membrane and copper tubing equipped with a schrader valve. The headspace within the sampler equilibrates with the dissolved gases in the groundwater in around 24 hours, and no groundwater is collected, which is of great advantage for use in contaminated sites. The design parameters and the time to equilibrium of the headspace sampler can be adjusted for investigation requirements using the analytical equation presented. The analysis of the gases for tracer content is performed by using a common gas chromatograph fitted with a thermal conductivity detector. Examples of the use of these methods at both the laboratory and field scales are presented.

Sanford, William E.; Shropshire, Robin G.; Solomon, D. Kip

242

What's the Conductivity of Gatorade?  

NSDL National Science Digital Library

Students use conductivity meters to measure various salt and water solutions, as indicated by the number of LEDs (light emitting diodes) that illuminate on the meter. Students create calibration curves using known amounts of table salt dissolved in water and their corresponding conductivity readings. Using their calibration curves, students estimate the total equivalent amount of salt contained in Gatorade (or other sports drinks and/or unknown salt solutions). This activity reinforces electrical engineering concepts, such as the relationship between electrical potential, current and resistance, as well as the typical circuitry components that represent these phenomena. The concept of conductors is extended to ions that are dissolved in solution to illustrate why electrolytic solutions support the passage of currents.

AMPS GK-12 Program,

243

Dissolved Trace Metals in Soft-Water Streams of the Northeast, USA  

NASA Astrophysics Data System (ADS)

The free dissolved fraction of trace metals is biologically available and correlated with acute toxicity in aquatic organisms that respire through gills. Consensus regarding prevalence of dissolved trace-metal occurrence in streams in the United States has varied, ranging from widespread occurrence in the 1 to 10's of micrograms per liter for cadmium, copper, chromium, lead, molybdenum, nickel, silver, and zinc, during 1975 to 1995, but less than 1 microgram per liter during the late 1990's to present. Whereas much of the earlier data is thought to have been affected by contamination during sampling and sample processing, later data after implementation of clean-sampling techniques indicates dissolved trace-metal concentrations in hard-water streams are very low because of sorption on suspended solids. In low-conductance, low-suspended-load streams of the northeast, USA, however, substantial dissolved metals concentrations have been measured with periods of record now approaching 6 years since implementation of clean sampling methods. The high concentrations are associated with industrial and domestic-development source, low surface area on suspended loads, and stabilizing dissolved organic ligands, including natural fulvic acids and chelating compounds of anthropogenic origin, such as EDTA. Although present at substantial concentrations, only a small part of the total dissolved metals is in a free state, unassociated with organic ligands, so that acute toxicity of the dissolved trace metals may be low.

Colman, J. A.

2004-05-01

244

Formulation and evaluation of aceclofenac mouth-dissolving tablet  

PubMed Central

Aceclofenac has been shown to have potent analgesic and anti-inflammatory activities similar to indomethacin and diclofenac, and due to its preferential Cox-2 blockade, it has a better safety than conventional Non steroidal anti-inflammatory drug (NSAIDs) with respect to adverse effect on gastrointestinal and cardiovascular systems. Aceclofenac is superior from other NSAIDs as it has selectivity for Cox-2, a beneficial Cox inhibitor is well tolerated, has better Gastrointestinal (GI) tolerability and improved cardiovascular safety when compared with other selective Cox-2 inhibitor. To provide the patient with the most convenient mode of administration, there is need to develop a fast-disintegrating dosage form, particularly one that disintegrates and dissolves/disperses in saliva and can be administered without water, anywhere, any time. Such tablets are also called as “melt in mouth tablet.” Direct compression, freeze drying, sublimation, spray drying, tablet molding, disintegrant addition, and use of sugar-based excipients are technologies available for mouth-dissolving tablet. Mouth-dissolving tablets of aceclofenac were prepared with two different techniques, wet granulation and direct compression, in which different formulations were prepared with varying concentration of excipients. These tablets were evaluated for their friability, hardness, wetting time, and disintegration time; the drug release profile was studied in buffer Phosphate buffered Saline (PBS) pH 7.4. Direct compression batch C3 gave far better dissolution than the wet granulation Batch F2, which released only 75.37% drug, and C3, which released 89.69% drug in 90 minutes.

Solanki, Shailendra Singh; Dahima, Rashmi

2011-01-01

245

Variation of dissolved oxygen and redox potential and their correlation with microbial population along a novel horizontal subsurface flow wetland  

Microsoft Academic Search

Aims: This study was conducted to evaluate the performance of a novel horizontal subsurface flow wetland (HSFW) in naturally improving the dissolved oxygen (DO) and the impact on redox condition, microbial activity and the nitrogen removal in the HSFW bed.\\\

Jun Zhai; Jinsong Zou; Qiang He; Kejia Ning; Haiwen Xiao

2012-01-01

246

Feasibility Study for Evaluating Cumulative Exposure of Downstream Migrant Juvenile Salmonids to Total Dissolved Gas. Final Report 1996.  

SciTech Connect

A feasibility study was initiated to determine if downstream migrant salmonids could be monitored to determine potential relationships between total dissolved gas (TDG) exposure and signs of gas bubble trauma (GBT). The primary objectives were to: (1) establish logistical requirements for in-river monitoring of TDG exposure, including net pen design, deployment, and navigation constraints; (2) resolve uncertainties associated with effects of the net pen on fish behavior; (3) test the accuracy and precision of in-river monitoring equipment used to measure fish distribution and water quality; and (4) determine the application of hydrologic/flow models to predictions of TDG exposure. In-river measurements included water velocity, boat position, and selected water quality parameters (temperature, dissolved oxygen, pH, depth, conductivity). Fish distribution within the net pen was monitored using scanning sonar, and a split-beam echo sounder was used to evaluate vertical distribution of fish m in the river adjacent to the net pen. Three test drifts were conducted from late July through late August. The studies demonstrated that it was feasible to assemble and deploy a large net pen for mobile monitoring of TDG exposure. Accurate monitoring of vertical and lateral distribution of smolts was performed, and diel differences in behavior were documented. Further, the fish sounded in response to researcher activity on the perimeter platform. Thus, in-transit monitoring for GBT or mortality would affect fish depth distribution and exposure to TDG. Principal recommendations for future studies are directed at improving maneuverability of the net pen in adverse weather conditions and applying new acoustics technology to simultaneously collect fish distribution data from within and outside of the pen. 6 refs., 17 figs., 2 tabs.

Abernethy, C.Scott; Dauble, Dennis D.; Johnson, Robert L. [Pacific Northwest National Laboratory, Richland, WA (United States)

1997-11-01

247

Effect of magnesium ions on the stable oxygen isotope equilibrium between dissolved inorganic carbon species and water.  

NASA Astrophysics Data System (ADS)

Stable oxygen isotope (?18O) values of foraminiferal calcites, which represent one of the most fundamental paleoceanographic tools to reconstruct ancient seawater temperatures, are influenced by seawater pH variations. Understanding the driving mechanism for such phenomenon requires precise knowledge of the equilibrium 18O fractionation factors between dissolved inorganic carbon (DIC) species and water. An experimental study by Beck et al. (2005) successfully refined the 18O fractionation factors between DIC components and water. Based on these results, the overall 18O fractionation between total DIC and water as a function of pH can be readily calculated (e.g., Zeebe, 2007). However, these calculations may not be applicable to seawater because the fractionation factors were measured in freshwater. Natural seawater contains numerous ionic species and other dissolved constituents, which may affect the fractionation factors. For example, it has been experimentally demonstrated that the presence of magnesium ions (Mg2+) in solutions affect equilibrium carbon isotope (13C) fractionation between aqueous CO2 and carbonate ions presumably due to the enrichment of 13C isotopes in Mg-CO30 complexes (Thode et al., 1965). This suggests that the presence of Mg2+ in solutions similarly affects the 18O fractionation factors between DIC species and water. On the other hand, Beck et al. (2005) concluded that the effect of ion pairs on the ?18O equilibrium appears to be negligible. However, this conclusion may not apply to ion paring in general, because experiments were not conducted for metal ions other than Na+. Given that Mg2+ has a marked effect on the equilibrium ?13C fractionation factors and Mg-CO30 is the most abundant form of metal-CO3-complexes in natural seawater, the potential effect of Mg2+ on the 18O fractionation factors between DIC components and water needs to be examined. Here, we will present preliminary results from quantitative carbonate precipitation experiments to evaluate the influence of Mg2+ on the ?18O equilibrium in the DIC-water system. REFERENCES Beck, W.C., Grossman, E.L., and Morse, J.W. (2005). Experimental studies of oxygen isotope fractionation in the carbonic acid system at 15° , 25° and 40° C. Geochim. Cosmochim. Acta, 69, 3493-3503. Thode, H.G., Shima, M., Rees, C.E., and Krishnamurty, K.V. (1965). Carbon-13 isotope effects in systems containing carbon dioxide, bicarbonate, carbonate, and metal ions. Canad. J. Chem., 43, 582-595. Zeebe, R.E. (2007). An expression for the overall oxygen isotope fractionation between the sum of dissolved inorganic carbon and water. Geochem. Geophys. Geosyst., 8, Q09002, doi: 10.1029/2007GC001663.

Uchikawa, Joji; Zeebe, Richard

2010-05-01

248

Biological Assessment of the Revised Oregon Water Quality Standards for Dissolved Oxygen, Temperature, and PH.  

National Technical Information Service (NTIS)

Section 303 of the Clean Water Act (CWA) requires States to adopt Water Quality Standards (WQS) to restore and maintain the chemical, physical, and biological integrity of the Nation's waters. WQS consists of beneficial uses (i.e. salmonid fish spawning, ...

1998-01-01

249

Interdisciplinary Ph.D. Programming in Evaluation.  

ERIC Educational Resources Information Center

|Advocates and presents an illustrative structure for interdisciplinary Ph.D. programs in evaluation. Posits that the introduction of such programs will give prospective students options through which they can gain the knowledge, skills, and experience needed to conduct evaluations. Describes the interdisciplinary evaluation program at Western…

Stufflebeam, Daniel L.

2001-01-01

250

Lithium ion conducting electrolytes  

DOEpatents

A liquid, predominantly lithium-conducting, ionic electrolyte is described having exceptionally high conductivity at temperatures of 100 C or lower, including room temperature, and comprising the lithium salts selected from the group consisting of the thiocyanate, iodide, bromide, chloride, perchlorate, acetate, tetrafluoroborate, perfluoromethane sulfonate, perfluoromethane sulfonamide, tetrahaloaluminate, and heptahaloaluminate salts of lithium, with or without a magnesium-salt selected from the group consisting of the perchlorate and acetate salts of magnesium. Certain of the latter embodiments may also contain molecular additives from the group of acetonitrile (CH{sub 3}CN), succinnonitrile (CH{sub 2}CN){sub 2}, and tetraglyme (CH{sub 3}--O--CH{sub 2}--CH{sub 2}--O--){sub 2} (or like solvents) solvated to a Mg{sup +2} cation to lower the freezing point of the electrolyte below room temperature. Other particularly useful embodiments contain up to about 40, but preferably not more than about 25, mol percent of a long chain polyether polymer dissolved in the lithium salts to provide an elastic or rubbery solid electrolyte of high ambient temperature conductivity and exceptional 100 C conductivity. Another embodiment contains up to about but not more than 10 mol percent of a molecular solvent such as acetone. 2 figs.

Angell, C.A.; Liu, C.

1996-04-09

251

ADDING REALISM TO NUCLEAR MATERIAL DISSOLVING ANALYSIS  

SciTech Connect

Two new criticality modeling approaches have greatly increased the efficiency of dissolver operations in H-Canyon. The first new approach takes credit for the linear, physical distribution of the mass throughout the entire length of the fuel assembly. This distribution of mass is referred to as the linear density. Crediting the linear density of the fuel bundles results in using lower fissile concentrations, which allows higher masses to be charged to the dissolver. Also, this approach takes credit for the fact that only part of the fissile mass is wetted at a time. There are multiple assemblies stacked on top of each other in a bundle. On average, only 50-75% of the mass (the bottom two or three assemblies) is wetted at a time. This means that only 50-75% (depending on operating level) of the mass is moderated and is contributing to the reactivity of the system. The second new approach takes credit for the progression of the dissolving process. Previously, dissolving analysis looked at a snapshot in time where the same fissile material existed both in the wells and in the bulk solution at the same time. The second new approach models multiple consecutive phases that simulate the fissile material moving from a high concentration in the wells to a low concentration in the bulk solution. This approach is more realistic and allows higher fissile masses to be charged to the dissolver.

Williamson, B.

2011-08-15

252

Electrochemical generation of hydrogen peroxide from dissolved oxygen in acidic solutions  

Microsoft Academic Search

Hydrogen peroxide (H2O2) was electro-generated in a parallel-plate electrolyzer by reduction of dissolved oxygen (DO) in acidic solutions containing dilute supporting electrolyte. Operational parameters such as cathodic potential, oxygen purity and mass flow rate, cathode surface area, pH, temperature, and inert supporting electrolyte concentration were systematically investigated as to improve the Faradic current efficiency of H2O2 generation. Results indicate that

Zhimin Qiang; Jih-Hsing Chang; Chin-Pao Huang

2002-01-01

253

Effect of progressive acidification on stable carbon isotopes of dissolved inorganic carbon in surface waters  

Microsoft Academic Search

Acidification of surface waters by acid mine drainage (AMD) contamination or atmospheric deposition perturbs the carbonate equilibrium, with unknown effects to the isotope ratio of dissolved inorganic carbon (DIC). We progressively acidified samples of NaHCO3, stream water, groundwater, and spring water contaminated by AMD (AMD spring) to a pH < 3 using H2SO4 under open conditions (exposed to the atmosphere)

Hendratta N. Ali; Eliot A. Atekwana

2009-01-01

254

Treatment of oil-in-water emulsions by coagulation and dissolved-air flotation  

Microsoft Academic Search

The treatment of oil-in-water emulsions containing n-octane (used as simulated wastewater) was investigated by means of dissolved-air flotation jar-tests. The effect of several parameters on flotation efficiency for separation of the emulsified oil was examined, namely, (a) the presence the nonionic surfactant Tween 80, used for the stabilization of the emulsions, (b) the initial pH value of the emulsions, (c)

A. I Zouboulis; A Avranas

2000-01-01

255

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

Microsoft Academic Search

(1) Total suspended solids (TSS), dissolved organic carbon (DOC), and total dissolved nitrogen (TDN) loads were calculated for all stages of the dam removal process (dewatering, breaching, and removal) at various points upstream, within, and downstream of Lowell Mill Impoundment on the Little River, North Carolina. The impoundment dewatering exported loads of TSS, DOC, and TDN which were all 1-2

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

2007-01-01

256

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

Microsoft Academic Search

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

Aaron M. Hook; J. Alan Yeakley

2005-01-01

257

PhET: Research  

NSDL National Science Digital Library

This web page contains links to published research articles relating to the Physics Education Technology Project (PhET). This project provides technology-based resources and information for physics education, most notably, simulations on a wide range of topics including Newton's Laws, electricity, waves, light, and quantum physics. The simulations are developed in conjunction with careful research to enhance their effectiveness as learning tools.

Project, The P.

2009-02-10

258

Influence of Dissolved Oxygen Levels on Production of l-Asparaginase and Prodigiosin by Serratia marcescens  

PubMed Central

The effect of dissolved oxygen concentrations on the behavior of Serratia marcescens and on yields of asparaginase and prodigiosin produced in shaken cultures and in a 55-liter stainless-steel fermentor was studied. A range of oxygen transfer rates was obtained in 500-ml Erlenmeyer flasks by using internal, stainless-steel baffles and by varying the volume of medium per flask, and in the fermentor by high speed agitation (375 rev/min) or low rates of aeration (1.5 volumes of air per volume of broth per min), or both. Dissolved oxygen levels in the fermentation medium were measured with a membrane-type electrode. Peak yields of asparaginase were obtained in unbaffled flasks (3.0 to 3.8 IU/ml) and in the fermentor (2.7 IU/ml) when the level of dissolved oxygen in the culture medium reached zero. A low rate of oxygen transfer was accomplished by limited aeration. Production of prodigiosin required a supply of dissolved oxygen that was obtainable in baffled flasks with a high rate of oxygen transfer and in the fermentor with a combination of high-speed agitation and low-rate aeration. The fermentation proceeded at a more rapid rate and changes in pH and cell populations were accelerated by maintaining high levels of dissolved oxygen in the growth medium.

Heinemann, Bernard; Howard, Alma J.; Palocz, Henry J.

1970-01-01

259

Removal of dissolved organic matter by anion exchange: effect of dissolved organic matter properties.  

PubMed

Ten isolates of aquatic dissolved organic matter (DOM) were evaluated to determine the effect that chemical properties of the DOM, such as charge density, aromaticity, and molecular weight, have on DOM removal by anion exchange. The DOM isolateswere characterized as terrestrial, microbial, or intermediate humic substances or transphilic acids. All anion exchange experiments were conducted using a magnetic ion exchange (MIEX) resin. The charge density of the DOM isolates, determined by direct potentiometric titration, was fundamental to quantifying the stoichiometry of the anion exchange mechanism. The results clearly show that all DOM isolates were removed by anion exchange; however, differences among the DOM isolates did influence their removal by MIEX resin. In particular, MIEX resin had the greatest affinity for DOM with high charge density and the least affinity for DOM with low charge density and low aromaticity. This work illustrates that the chemical characteristics of DOM and solution conditions must be considered when evaluating anion exchange treatment for the removal of DOM. PMID:18939582

Boyer, Treavor H; Singer, Philip C; Aiken, George R

2008-10-01

260

Lithium ion conducting ionic electrolytes  

DOEpatents

A liquid, predominantly lithium-conducting, ionic electrolyte is described which has exceptionally high conductivity at temperatures of 100.degree. C. or lower, including room temperature. It comprises molten lithium salts or salt mixtures in which a small amount of an anionic polymer lithium salt is dissolved to stabilize the liquid against recrystallization. Further, a liquid ionic electrolyte which has been rubberized by addition of an extra proportion of anionic polymer, and which has good chemical and electrochemical stability, is described. This presents an attractive alternative to conventional salt-in-polymer electrolytes which are not cationic conductors.

Angell, C. Austen (Mesa, AZ); Xu, Kang (Tempe, AZ); Liu, Changle (Tulsa, OK)

1996-01-01

261

Dissolved Organic Metals in the Hydrothermal Plume  

NASA Astrophysics Data System (ADS)

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

Shitashima, K.

2003-12-01

262

In situ spectrophotometric measurement of dissolved inorganic carbon in seawater.  

PubMed

Autonomous in situ sensors are needed to document the effects of today's rapid ocean uptake of atmospheric carbon dioxide (e.g., ocean acidification). General environmental conditions (e.g., biofouling, turbidity) and carbon-specific conditions (e.g., wide diel variations) present significant challenges to acquiring long-term measurements of dissolved inorganic carbon (DIC) with satisfactory accuracy and resolution. SEAS-DIC is a new in situ instrument designed to provide calibrated, high-frequency, long-term measurements of DIC in marine and fresh waters. Sample water is first acidified to convert all DIC to carbon dioxide (CO2). The sample and a known reagent solution are then equilibrated across a gas-permeable membrane. Spectrophotometric measurement of reagent pH can thereby determine the sample DIC over a wide dynamic range, with inherent calibration provided by the pH indicator's molecular characteristics. Field trials indicate that SEAS-DIC performs well in biofouling and turbid waters, with a DIC accuracy and precision of ?2 ?mol kg(-1) and a measurement rate of approximately once per minute. The acidic reagent protects the sensor cell from biofouling, and the gas-permeable membrane excludes particulates from the optical path. This instrument, the first spectrophotometric system capable of automated in situ DIC measurements, positions DIC to become a key parameter for in situ CO2-system characterizations. PMID:23991621

Liu, Xuewu; Byrne, Robert H; Adornato, Lori; Yates, Kimberly K; Kaltenbacher, Eric; Ding, Xiaoling; Yang, Bo

2013-09-17

263

MONITORING NATURAL ORGANIC MATTER IN SURFACE WATER BY UV SPECTROSCOPY: EFFECTS OF CALCIUM, MAGNESIUM AND PH VALUE  

Microsoft Academic Search

The aim of this study was to evaluate the effects of dissolved magnesium and calcium ions on the determination of humic substances in water by spectrophotometry at 254 nm. Quantifications were carried out for different pH values, both with and without filtration of the samples. The smallest effects were observed for unfiltered samples and neutral pH values.

264

Effects of photodegradation of dissolved organic matter on the binding of benzo(a)pyrene.  

PubMed

Dissolved organic matter (DOM) in natural waters can bind various organic pollutants, and the affinity of this binding is strongly influenced by the chemical characteristics of the DOM and water pH. This study examined the effects of photochemically induced alteration of the DOM's chemical properties and water pH on the binding of benzo(a)pyrene (BaP). Time- and pH-series of solar-simulated irradiations were performed on a natural water sample and aqueous DOM solutions prepared from aquatic and soil humic substances. The binding affinity of BaP, expressed as a partition coefficient of a compound to DOM, decreased substantially after the DOM samples were irradiated over environmentally relevant radiation doses and pH ranges. The lowering of the pH due to the photoproduction of acidic products often partly offsets the reduction of the binding affinity caused by direct photoalteration of the DOM's chemical structure. The decrease of the binding affinity, after correction for the photoinduced pH change, was positively correlated with the decrease in the molecular weight and the aromaticity of the DOM in the course of irradiation. Increasing O(2) abundance accelerated the decrease of the binding affinity as a result of enhanced DOM photodegradation. Visible light played a more important role in reducing the molecular weight and aromaticity of the DOM than in reducing the content of dissolved organic carbon (DOC) via photoremineralization while the reverse was true for UV radiation, indicating that photochemical reduction of the binding affinity may occur in natural waters at depths greater than UV radiation can reach. A decrease of the affinity of DOM for binding BaP will increase the free dissolved fraction of BaP and thus its availability and toxicity to aquatic organisms. The results from this study may have similar implications for organic pollutants other than BaP. PMID:16406054

Lou, Tao; Xie, Huixiang; Chen, Guohua; Gagné, Jean-Pierre

2006-01-10

265

Dissolved carbon and nitrogen quantity and quality at natural, drained and re-wetted bog sites in Lower Saxony (Germany)  

NASA Astrophysics Data System (ADS)

5 % of Germany's land area is covered with peatlands. Due to the large carbon and nitrogen stocks, changes in peatland hydrology for agricultural use have a huge impact on C and N cycling in the peatland and on the export to the atmosphere and adjacent ecosystems. Nonetheless, only a few studies focussed on the impact of drainage and re-wetting on C and N cycling in German raised bogs. Four study sites in the "Ahlenmoor" near Cuxhaven (Northwestern Germany) were chosen. This bog has a deep, medium to weakly decomposed peat layer. The sites represent a gradient of the groundwater level combined with land use differences (intensive and extensive grassland, natural site, re-wetted peat-cutting area). The mean annual groundwater level decreases from the natural and re-wetted sites (near surface) to the extensive grassland (30 cm below surface) and, finally, the intensive grassland (56 cm). The "Peeper" technique (dialysis sampler) was used to measure soil water chemistry in a high spatial resolution. At each site, three peepers (0-60 cm, 12 chambers each) collected soil water samples via diffusion. Monthly sampling was conducted from February 2012 till November 2012. The soil water solution was analysed for pH, EC, dissolved organic carbon (DOC), dissolved organic nitrogen (DON), NH4+, NO3- and SUVA(280). Samples taken in November 2012 were additionally analysed for dissolved CO2, CH4 and N2O. Average DOC concentrations ranged from 211 to 41 mg/L and decreased in order intensive > extensive grassland > re-wetted = natural site. After 10 years of restoration, the re-wetted and the natural site show similar DOC concentrations. Average SUVA(280) values of 3.7 to 3.3 L/(mg m) were higher at the grassland sites than at the re-wetted and the natural site. This indicates a distinct increase in aromaticity of DOC in grassland sites as a result of more intense humification of the upper peat layer. In contrast to mineral soils, SUVA(280) remained constant with depth at our sites. Total nitrogen decreased in same order as DOC and was mainly composed of DON. NH4+ dominates the inorganic nitrogen fraction. The comparison of peat C/N to DOC/DON ratios indicates that the more degraded upper layer is the main source of carbon and nitrogen in the soil solution. Dissolved inorganic carbon (DIC) was mainly measured as dissolved CO2-C (13.6 mg/L), followed by CH4-C (1.7 mg/L). While CH4-C was present over the whole profile at the re-wetted and the natural site, it was missing in the upper 40 cm of the grassland sites. Instead, dissolved N2O-N was found (19.8 µg/L). Especially in natural bogs with low DOC concentrations, DIC may be a relevant part of the carbon budget. Our results show that the groundwater level in combination with land use has a huge impact on C- and N-quality and quantity between sites and within the peat profile, and that re-wetting may result in a return to "natural" DOC concentration levels and properties.

Frank, Stefan; Tiemeyer, Bärbel; Freibauer, Annette

2013-04-01

266

Steady-state dissolved oxygen model of the Willamette River, Oregon  

USGS Publications Warehouse

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

McKenzie, Stuart W.; Hines, W. G.; Rickert, D. A.; Rinella, F. A.

1979-01-01

267

Dissolved-oxygen regimen of the Willamette River, Oregon, under conditions of basinwide secondary treatment  

USGS Publications Warehouse

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

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

1977-01-01

268

Control of Dissolved Oxygen in Stirred Bioreactors  

Microsoft Academic Search

This report discusses control of dissolved oxygen in a biore­ actor where the oxygen supply is manipulated using the stirrer speed. In batch and fed­batch cultivations the operating conditions change signifi­ cantly which may cause tuning problems. Analysis using a linearized pro­ cess model shows that the process dynamics is mainly affected by changes in the volumetric oxygen transfer coefficient

Mats Åkesson Per Hagander

269

REMOVING DISSOLVED INORGANIC CONTAMINANTS FROM WATER  

EPA Science Inventory

Dissolved inorganic contaminants in water can be cationic, anionic, or neutral forms of ions, atoms, or molecules of any element in the periodic table. The article describes the physicochemical treatment processes typically used to remove the more common inorganic contaminants fr...

270

Dissolved zirconium in the north Pacific Ocean  

SciTech Connect

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

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

1993-08-01

271

Dissolved silver in the Baltic Sea  

Microsoft Academic Search

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

Kuria Ndungu

2011-01-01

272

DISSOLVED OXYGEN IMPACT FROM URBAN STORM RUNOFF  

EPA Science Inventory

The primary objective of the research reported here is to determine if on a national basis a correlation exists between strength of dissolved oxygen (DO) deficits and the presence of rainfall and/or storm runoff downstream of urban areas. A secondary objective is to estimate the ...

273

Progress in dissolving modified LEU Cintichem targets.  

National Technical Information Service (NTIS)

A process is under development to use low-enriched uranium (LEU) metal targets for production of (sup 99)Mo. The first step is to dissolve the irradiated foil. In past work, this has been done by heating a closed (sealed) vessel containing the foil and a ...

R. A. Leonard L. Chen C. J. Mertz G. F. Vandegrift

1996-01-01

274

Bubble Dissolving in Turbulent Pipe Flow.  

National Technical Information Service (NTIS)

Measurements are presented of bubble dissolving in turbulent pipe flow at pipe Reynolds numbers of 2xlO4, lxlO5 and 2xlO5, based on pipe diameter. The mass transfer coefficient is determined and it increases with Reynolds number. The coefficient appears t...

S. Gowing

1992-01-01

275

Dissolved vanadium in rivers and estuaries  

NASA Astrophysics Data System (ADS)

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

Shiller, Alan M.; Boyle, Edward A.

1987-12-01

276

Dissolved zirconium in the North Pacific Ocean  

NASA Astrophysics Data System (ADS)

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

McKelvey, Brad A.; Orians, Kristin J.

1993-08-01

277

Water quality and dissolved inorganic fluxes of N, P, SO?, and K of a small catchment river in the Southwestern Coast of India.  

PubMed

The southwestern coast of India is drained by many small rivers with lengths less than 250 km and catchment areas less than 6,500 km(2). These rivers are perennial and are also the major drinking water sources in the region. But, the fast pace of urbanization, industrialization, fertilizer intensive agricultural activities and rise in pilgrim tourism in the past four to five decades have imposed marked changes in water quality and solute fluxes of many of these rivers. The problems have aggravated further due to leaching of ionic constituents from the organic-rich (peaty) impervious sub-surface layers that are exposed due to channel incision resulting from indiscriminate instream mining for construction-grade sand and gravel. In this context, an attempt has been made here to evaluate the water quality and the net nutrient flux of one of the important rivers in the southwestern coast of India, the Manimala river which has a length of about 90 km and catchment area of 847 km(2). The river exhibits seasonal variation in most of the water quality parameters (pH, electrical conductivity, dissolved oxygen, total dissolved solids, Ca, Mg, Na, K, Fe, HCO(3), NO(2)-N, NO(3)-N, P[Formula: see text], P[Formula: see text], chloride, SO(4), and SiO(2)). Except for NO(3)-N and SiO(2), all the other parameters are generally enriched in non-monsoon (December-May) samples than that of monsoon (June-November). The flux estimation reveals that the Manimala river transports an amount of 2,308 t y(-1) of dissolved inorganic nitrogen, 87 t y(-1) dissolved inorganic phosphorus, and 9246 t y(-1) of SO(4), and 1984 t y(-1) K into the receiving coastal waters. These together constitute about 23% of the total dissolved fluxes transported by the Manimala river. Based on the study, a set of mitigation measures are also suggested to improve the overall water quality of small catchment rivers of the densely populated tropics in general and the south western coast in particular. PMID:21544504

Padmalal, D; Remya, S I; Jyothi, S Jissy; Baijulal, B; Babu, K N; Baiju, R S

2011-05-05

278

Interlaboratory Test of pH Measurements in Rainwater.  

National Technical Information Service (NTIS)

An interlaboratory test of pH measurements in rainwater has been conducted. Various types of electrodes and junction materials were used in the test. The results of the exercise verify that there are significant differences in the pH values of low ionic s...

W. F. Koch G. Marinenko R. C. Paule

1985-01-01

279

Interlaboratory test of pH measurements in rainwater  

SciTech Connect

An interlaboratory test of pH measurements in rainwater was conducted. Various types of electrodes and junction materials were used in the test. The results of the exercise verify that there are significant differences in the pH values of low-ionic-strength solutions reported by various laboratories.

Koch, W.F.; Marinenko, G.; Paule, R.C.

1985-10-23

280

Predicting Computer Science Ph.D. Completion: A Case Study  

ERIC Educational Resources Information Center

|This paper presents the results of an analysis of indicators that can be used to predict whether a student will succeed in a Computer Science Ph.D. program. The analysis was conducted by studying the records of 75 students who have been in the Computer Science Ph.D. program of the University of Alabama in Huntsville. Seventy-seven variables were…

Cox, G. W.; Hughes, W. E., Jr.; Etzkorn, L. H.; Weisskopf, M. E.

2009-01-01

281

Identification of Dissolved-Constituent Sources in Mine-Site Ground Water Using Batch Mixing  

NASA Astrophysics Data System (ADS)

Batch-mixing experiments were used to help identify lithologic and mineralogic sources of increased concentrations of dissolved solids in water affected by surface coal mining in northwestern Colorado. Ten overburden core samples were analyzed for mineral composition and mixed with distilled water for 90 days until mineral-water equilibrium was reached. Between one day and 90 days after initial contact, specific conductance in the sample mixtures had a median increase of 306 percent. Dissolved-solids concentrations ranged from 200 to 8,700 mg/L in water samples extracted from the mixtures after 90 days. Mass-balance simulations were conducted using the geochemical models BALANCE and WATEQF to quantify mineral-water interactions occurring in five selected sample mixtures and in water collected from a spring at a reclaimed mine site. The spring water is affected by mineral-water interactions occurring in all of the lithologic units comprising the overburden. Results of the simulations indicate that oxidation of pyrite, dissolution of dolomite, gypsum, and epsomite, and cation-exchange reactions are the primary mineral-water interactions occurring in the overburden. Three lithologic units in the overburden (a coal, a sandstone, and a shale) probably contribute most of the dissolved solids to the spring water. Water sample extracts from mixtures using core from these three units accounted for 85 percent of the total dissolved solids in the 10 sample extracts. Other lithologic units in the overburden probably contribute smaller quantities of dissolved solids to the spring water.

Clark, Gregory M.; Williams, Robert S., Jr.

1991-02-01

282

Appropriate Conduct  

ERIC Educational Resources Information Center

Many years ago when the author assumed the role of assistant principal for school climate, discipline, and attendance, he inherited many school policies and guidelines that were outdated, unfair, and without merit in the current school climate. Because the school conduct code had not been revised since the school opened in 1960, many of the…

Di Lullo, Louis

2004-01-01

283

Conducting Meetings.  

ERIC Educational Resources Information Center

|Written for anyone interested in what makes a meeting run smoothly (and what doesn't), the guide for conducting meetings is divided into the following sections: the chairperson (his/her responsibilities, preparing an agenda, organizing discussions); the meeting (quorums, discussions, points of order, and clarification); the motion (making the…

United Tribes Educational Technical Center, Bismarck, ND.

284

Appropriate Conduct  

ERIC Educational Resources Information Center

|Many years ago when the author assumed the role of assistant principal for school climate, discipline, and attendance, he inherited many school policies and guidelines that were outdated, unfair, and without merit in the current school climate. Because the school conduct code had not been revised since the school opened in 1960, many of the…

Di Lullo, Louis

2004-01-01

285

Flux of Dissolved Forms of Mercury Across the Sediment-Water Interface in Lahontan Reservoir, Nevada.  

National Technical Information Service (NTIS)

Field and laboratory studies were conducted between April 30, 2001 and July 19, 2001 to provide the first direct measurements of the benthic flux of dissolved mercury species (total and methylated forms) between the bottom sediment and water column at thr...

J. S. Kuwabara M. Marvin-Dipasquale W. Praskins E. Bryon B. R. Topping

2002-01-01

286

Predicting and managing risk of unsuitable dissolved oxygen in a eutrophic lake  

Microsoft Academic Search

Eutrophication of lakes is often accompanied by wide diel fluctuations in dissolved oxygen (DO) concentrations that can influence fish assemblage composition and periodically result in highly visible fish kills. We conducted a probabilistic risk assessment to estimate the likelihood that a shallow eutrophic oxbow lake would be affected by critically low DO concentration at dawn during mid-summer. Monte-Carlo simulations with

L. E. Miranda; J. A. Hargreaves; S. W. Raborn

2001-01-01

287

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

Microsoft Academic Search

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

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

1987-01-01

288

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

EPA Science Inventory

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

289

Study on a novel non-dissolved redox mediator catalyzing biological denitrification (RMBDN) technology  

Microsoft Academic Search

There are little literatures about the accelerating effect of redox mediators on the denitrification processes. In this paper, a novel non-dissolved redox mediator catalyzing biological denitrification (RMBDN) technology was first explored, and the accelerating effect of redox mediator on the denitrification processes was conducted with immobilized anthraquinone. Anthraquinone as a redox mediator was able to increase the denitrification rate, and

Jianbo Guo; Li Kang; Jingliang Yang; Xiaolei Wang; Jing Lian; Haibo Li; Yankai Guo; Yuyu Wang

2010-01-01

290

Growth and biomass stimulation of the toxic dinoflagellate Gymnodinium catenatum (Graham) by dissolved organic substances  

Microsoft Academic Search

Blooms of the toxic dinoflagellate Gymnodinium catenatum are annually recurrent events in south-east Tasmanian waters. Extensive blooms are preceded by a rainfall `trigger' and the associated influx of dissolved organic matter (DOM; otherwise known as humic substances) from land runoff. Culture studies were conducted to investigate the potential nutritive influence of DOM on G. catenatum. Using a seawater-based growth medium

Martina A Doblin; Susan I Blackburn; Gustaaf M Hallegraeff

1999-01-01

291

EFFECT OF ACID TREATMENT ON DISSOLVED ORGANIC CARBON RETENTION BY A SPODIC HORIZON  

EPA Science Inventory

Processes involving the movement of organic substances in forest soils are not well understood. This study was conducted to examine the role of acidic inputs on dissolved organic carbon (DOC) mobility, processes affecting the retention of DOV by a B horizon, and SO2-4 adsorption....

292

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

EPA Science Inventory

Daphnia magna, Daphnia pulex, Hyalella azteca, and Gammarus lacustris were exposed to low dissolved oxygen concentrations in the laboratory. cute and chronic exposures were conducted to develop data for use in the U.S. Environmental Protection Agency's (EPA's) water quality crite...

293

Performance study of the inverted absorber solar still with water depth and total dissolved solid  

Microsoft Academic Search

In this communication, an experimental study of inverted absorber solar still (IASS) and single slope solar still (SS) at different water depth and total dissolved solid (TDS) is presented. Experiments are conducted for the climatic condition of Muscat, Oman. A thermal model is also developed for the IASS and validated with experimental results. A fair agreement is found for the

Rahul Dev; Sabah A. Abdul-Wahab; G. N. Tiwari

2011-01-01

294

Stabilization of dissolved organic matter by aluminium: A toxic effect or stabilization through precipitation?  

Microsoft Academic Search

Carbon mineralization in acidic forest soils can be retarded by large concentrations of aluminium (Al). However, it is still unclear whether Al reduces C mineralization by direct toxicity to microorganisms or by decreased bioavailability of organic matter (OM) because dissolved organic matter (DOM) is precipitated by Al. We conducted an incubation experiment (6 weeks) with two DOM solutions (40 mg

T. Scheel; B. Jansen; Wijk van A. J; J. M. Verstraten; K. Kalbitz

2008-01-01

295

Technical description of parameters influencing the pH value of suspension absorbent used in flue gas desulfurization systems.  

PubMed

As a result of the large limestone deposits available in Poland, the low cost of reagent acquisition for the largescale technological use and relatively well-documented processes of flue gas desulfurization (FGD) technologies based on limestone sorbent slurry, wet scrubbing desulfurization is a method of choice in Poland for flue gas treatment in energy production facilities, including power plants and industrial systems. The efficiency of FGD using the above method depends on several technological and kinetic parameters, particularly on the pH value of the sorbent (i.e., ground limestone suspended in water). Consequently, many studies in Poland and abroad address the impact of various parameters on the pH value of the sorbent suspension, such as the average diameter of sorbent particles (related to the limestone pulverization degree), sorbent quality (in terms of pure calcium carbonate [CaCO3] content of the sorbent material), stoichiometric surfeit of CaCO3 in relation to sulfur dioxide (SO2) absorbed from flue gas circulating in the absorption node, time of absorption slurry retention in the absorber tank, chlorine ion concentration in sorbent slurry, and concentration of dissolved metal salts (Na, K, Mg, Fe, Al, and others). This study discusses the results of laboratory-scale tests conducted to establish the effect of the above parameters on the pH value of limestone slurry circulating in the SO2 absorption node. On the basis of the test results, a correlation equation was postulated to help maintain the desirable pH value at the design phase of the wet FGD process. The postulated equation displays good coincidence between calculated pH values and those obtained using laboratory measurements. PMID:20842941

G?omba, Micha?

2010-08-01

296

Interplay Between Intestinal pH, Transit Time and Feed Status on the In Vivo Performance of pH Responsive IleoColonic Release Systems  

Microsoft Academic Search

Purpose  Oral pH triggered drug delivery systems, for targeting to the lower gastrointestinal tract, show erratic behaviour in vivo. This study aimed to establish correlations between in situ gastrointestinal pH, transit time or feed status and the disintegration of pH-responsive dosage forms designed to dissolve\\u000a above pH 7.\\u000a \\u000a \\u000a \\u000a Methods  Tablets (radiolabelled with Technetium 99m) coated with Eudragit S were administered to eight healthy

Valentine C. Ibekwe; Hala M. Fadda; Emma L. McConnell; Mandeep K. Khela; David F. Evans; Abdul W. Basit

2008-01-01

297

Factors affecting the presence of dissolved glutathione in estuarine waters.  

PubMed

We investigated factors influencing the presence of the thiol glutathione (GSH) in estuarine waters. Our study addressed thiol phase-association, the biological release from algal cultures, and the role of copper in both thiol release and preservation. Our measurements in three diverse estuaries in the continental United States (San Diego Bay, Cape Fear Estuary, and Norfolk Estuary) show that dissolved GSH, present at sub-nanomolar levels, is preferentially partitioned into the ultra-filtrate fraction (<1 kDa) in comparison with dissolved organic carbon (DOC). Concentrations of GSH generally increased with increases in total copper (Cu)levels, although large variability was observed among estuaries. In 30-h exposure experiments, release of dissolved GSH from the diatom Thalassiosira weissflogii into organic ligand-free experimental media was a strong function of added Cu concentration. The released GSH increased from about 0.02 to 0.27 fmol/cell as Cu was increased from the background level (0.5 nM) to 310 nM in the modified Aquil media. However, excretion of GSH was lower (up to 0.13 fmol/cell) when cells were grown in surface waters of San Diego Bay, despite much higher total Cu concentrations. Experiments conducted in-situ in San Diego Bay water indicated that high concentrations of added Cu destabilized GSH, while both Mn(II) and natural colloids promoted GSH stability. In contrast, laboratory experiments in synthetic media indicated that moderate levels of added Cu enhanced GSH stability. PMID:15382849

Tang, Degui; Shafer, Martin M; Karner, Dawn A; Overdier, Joel; Armstrong, David E

2004-08-15

298

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

USGS Publications Warehouse

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

Cravotta, III, C. A.

2008-01-01

299

Simultaneous spectrophotometric flow-through measurements of pH, carbon dioxide fugacity, and total inorganic carbon in seawater  

Microsoft Academic Search

An autonomous multi-parameter flow-through CO2 system has been developed to simultaneously measure surface seawater pH, carbon dioxide fugacity (fCO2), and total dissolved inorganic carbon (DIC). All three measurements are based on spectrophotometric determinations of solution pH at multiple wavelengths using sulfonephthalein indicators. The pH optical cell is machined from a PEEK polymer rod bearing a bore-hole with an optical pathlength

Zhaohui Aleck Wang; Xuewu Liu; Robert H. Byrne; Rik Wanninkhof; Renate E. Bernstein; Eric A. Kaltenbacher; James Patten

2007-01-01

300

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

Microsoft Academic Search

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

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

2008-01-01

301

Suspended solids abatement by pH increase—upgrading of an oxidation pond effluent  

Microsoft Academic Search

The effectiveness of solids abatement by pH increase was investigated using the jar test procedure with a bentonite tap water suspension and an urban wastewater and an oxidation pond effluent. The results indicated that, depending on the suspended particles and on the dissolved ions, pH values between 9.5 and 12 induced extensive solids elimination without adding any other chemical than

S. Elmaleh; H. Yahi; J. Coma

1996-01-01

302

The effect of microorganisms on Fe precipitation rates at neutral pH  

Microsoft Academic Search

The effect of microorganisms on Fe precipitation rates at neutral pH in the field was examined. The studied area was a cave having Fe-stalactites composed mainly of ferrihydrite and associated microorganisms. The microorganisms were covered with ferrihydrite. Water associated with stalactites was slightly supersaturated with respect to ferrihydrite, and had a dissolved oxygen concentration of 2 ppm, a pH of

Takeshi Kasama; Takashi Murakami

2001-01-01

303

Partitioning of organic matter in soils: effects of pH and water\\/soil ratio  

Microsoft Academic Search

The effects of pH and water\\/soil ratio on the soil–water partitioning of soil organic matter (SOM) in 15 New Jersey soils were investigated. The dissolved organic carbon (DOC) concentration stabilized within 24 h. An increase in pH increased dissolution of soil organic matter. The ratio of UV absorbance at 465 nm to that at 665 nm (E4\\/E6 ratio) of the

Sun-Jae You; Yujun Yin; Herbert E Allen

1999-01-01

304

Conductivity study of chitosan based nanocomposites  

NASA Astrophysics Data System (ADS)

Bio polymer like chitosan is dissolved in acids like formic and acetic acid and CdS nano particle prepared by chemical methods has been embedded in the salts of chitosan matrix. The viscous solution is cast into film on the glass substrate using spin coating method and their ionic conductivity has been studied for various frequencies and temperatures.

Mohan, C. Raja; Murugan, S.; Jayakumar, K.

2012-06-01

305

Scavenging of dissolved yttrium and rare earths by precipitating iron oxyhydroxide: experimental evidence for Ce oxidation, Y-Ho fractionation, and lanthanide tetrad effect  

Microsoft Academic Search

Scavenging experiments were performed at pH 3.6 to 6.2 with synthetic solutions containing dissolved Fe (?7 mg\\/L), Rare Earths and Yttrium (?REY: ?61 ?g\\/L) in a matrix of 0.01 M HCl, and with natural water from Nishiki-numa spring, Japan, with the aim to study the fractionation that results from the interaction of dissolved REY with precipitating Fe oxyhydroxide. All patterns

Michael Bau

1999-01-01

306

Conduction Countdown  

NSDL National Science Digital Library

In this quick SciGirls activity (page 1 of the PDF), learners will be introduced to the concept of thermal conductivity. A metal knife and a plastic knife are each poked into slices of cold butter then placed handle-first into a glass of warm water. Learners predict which butter slice will fall first and watch carefully for the result. Relates to the linked video, DragonflyTV GPS: Doghouse Design.

Twin Cities Public Television, Inc.

2006-01-01

307

Conductive Polymers  

SciTech Connect

Electroluminescent devices such as light-emitting diodes (LED) and high-energy density batteries. These new polymers offer cost savings, weight reduction, ease of processing, and inherent rugged design compared to conventional semiconductor materials. The photovoltaic industry has grown more than 30% during the past three years. Lightweight, flexible solar modules are being used by the U.S. Army and Marine Corps for field power units. LEDs historically used for indicator lights are now being investigated for general lighting to replace fluorescent and incandescent lights. These so-called solid-state lights are becoming more prevalent across the country since they produce efficient lighting with little heat generation. Conductive polymers are being sought for battery development as well. Considerable weight savings over conventional cathode materials used in secondary storage batteries make portable devices easier to carry and electric cars more efficient and nimble. Secondary battery sales represent an $8 billion industry annually. The purpose of the project was to synthesize and characterize conductive polymers. TRACE Photonics Inc. has researched critical issues which affect conductivity. Much of their work has focused on production of substituted poly(phenylenevinylene) compounds. These compounds exhibit greater solubility over the parent polyphenylenevinylene, making them easier to process. Alkoxy substituted groups evaluated during this study included: methoxy, propoxy, and heptyloxy. Synthesis routes for production of alkoxy-substituted poly phenylenevinylene were developed. Considerable emphasis was placed on final product yield and purity.

Bohnert, G.W.

2002-11-22

308

Pumping-induced ebullition: a unified and simplified method for measuring multiple dissolved gases.  

PubMed

The incorporation of multiple dissolved gas measurements in biogeochemical studies remains a difficult and expensive challenge. Incompatibilities in collection, handling, and storage procedures generally force the application of multiple sampling procedures for multiple gases. This paper introduces the concept and application of pumping-induced ebullition (PIE), a unified approach for routine measurement of multiple dissolved gases in natural waters and establishes a new platform for development of in situ real-time dissolved gas monitoring tools. Ebullition (spontaneous formation of bubbles) is induced by pumping a water sample through a narrow-diametertube (a "restrictor") to decrease hydrostatic pressure (PH) below total dissolved gas pressure (PT). Buoyancy is used to trap bubbles within a collection tower where gas accumulates rapidly (1 mL/min) to support multiple chemical analyses. Providing for field collection of an essentially unlimited and unified volume of gas sample, PIE afforded accurate and precise measurements of major (N2, 02, Ar), trace (CO2, N20, CH4) and ultratrace (CFC11, CFC12, CFC113, SF6) dissolved gases in Wisconsin groundwater, revealing interrelationships between denitrification, apparent recharge age-dates, and historical land use. Compared to conventional approaches, PIE eliminates multiple gas-specific sampling methods, reduces data computations, simplifies laboratory instrumentation, and avoids aqueous production and consumption of biogenic gases during sample storage. A lake depth profile for CO2 demonstrates PIE's flexibility as an in situ real-time platform for dissolved gas measurements. The apparent departures of some gases (SF6, H2, N2O, CO2) from solubility equilibrium behavior warrant further confirmation and theoretical investigation. PMID:15575293

Browne, Bryant A

2004-11-01

309

Upper ocean model of dissolved atmospheric gases  

SciTech Connect

The goal of this project is to estimate the rate of biological oxygen production at Hawaiian Ocean Time-series station ALOHA in the central North Pacific ocean. Our approach is to use an upper ocean model together with measurements to interpret an annual cycle of temperature, salinity, dissolved oxygen, argon, nitrogen, and the stable isotope ratio of oxygen at station ALOHA. This project represents the first upper ocean geochemical study in which model predictions are verifiable by independent measurements. Using the model, we will be able to assess the relative roles played by physical processes (air-sea gas exchange, air injection by bubbles, temperature-induced changes in gas solubility, trapping below the mixed layer, and diffusion) and biological processes (photosynthesis, respiration, and nutrient recycling) in producing the observed distribution of dissolved atmospheric gases. The long term goal of this project is to understand the utility of chemical tracers for quantifying biological processes in the ocean.

Schudlich, R.; Emerson, S.

1992-01-01

310

Dissolved silver in the Baltic Sea.  

PubMed

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

Ndungu, Kuria

2010-11-13

311

Distribution of dissolved silver in marine waters  

NASA Astrophysics Data System (ADS)

Silver is one of the most toxic heavy metals, surpassed only by mercury [1-3]. Monitoring of dissolved silver concentrations in natural waters is therefore of great importance. The determination of dissolved silver in waters is not without challenges, because of its low (picomolar) concentrations. Consequently, there are only a few reported studies in marine waters, which have been performed in USA [4-6] and Japan [7]. The analytical techniques used in the reported studies for the determination of silver in seawater were Graphite Furnace Atomic Absorption Spectroscopy (GFAAS) after solvent extraction [2,4,5], and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) after solvent extraction or solid phase extraction [7,8]. In this contribution, we will present an optimised Magnetic Sector (MS) ICP-MS technique for the determination of dissolved silver in marine waters. The MS-ICP-MS method used anion exchange column to preconcentrate silver from saline waters, and to remove the saline matrix. The ICP-MS method has been used successfully to determine total dissolved silver in estuarine and oceanic samples. Bibliography 1. H. T. Ratte, Environ. Toxicol. Chem. 1999, 18: p. 89-108. 2. R. T. Herrin, A. W. Andren and D. E. Armstrong, Environ. Sci. Technol. 2001, 35: 1953-1958. 3. D. E. Schildkraut, P. T. Dao, J. P. Twist, A. T. Davis and K. A. Robillard, Environ. Toxicol. Chem. 1998, 17: 642-649. 4. E. Breuer, S. A. Sanudo-Wilhelmy and R. C. Aller, Estuaries. 1999, 22:603-615. 5. A. R. Flegal, S. A. Sanudowilhelmy and G. M. Scelfo, Mar. Chem. 1995, 49: 315-320. 6. S. N. Luoma, Y. B. Ho and G. W. Bryan, Mar. Pollut. Bull. 1995, 31: 44-54. 7. Y. Zhang, H. Amakawa and Y. Nozaki, Mar. Chem. 2001, 75: 151-163. 8. L. Yang and R. E. Sturgeon, J. Anal. At. Spectrom. 2002, 17: 88-93.

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

2003-04-01

312

Fast dissolving films made of maltodextrins  

Microsoft Academic Search

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

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

2008-01-01

313

Dissolved gases in seawater and sediments  

Microsoft Academic Search

Certainly the most controversial results derived from the study of any dissolved gas concerned oxygen utilization rates in the North Atlantic. Jenkins (1982) estimated a net oxy- gen utilization rate (OUR) for the Beta triangle region of the North Atlantic (apices 26.5°N x 38.5°W, 32.5°N x 30.0°W, and 22.5°N x 28.5°W) of 5.7 moles of oxygen consumed m?2 yr?1 for

R. M. Key

1987-01-01

314

Dissolved oxygen and the scleroglucan fermentation process  

Microsoft Academic Search

The effect of culture dissolved oxygen (D.O.) upon biomass, scleroglucan and oxalate formation bySclerotium glucanicum was examined in a stirred tank fermenter by oxygen enrichment. Controlling culture D.O. at 5 or 10% saturation led to increased biomass formation and decreased scleroglucan formation. The mechanism by which this occurred probably involved a non-specific diversion of C source (sucrose) away from product

Y. Wang; B McNeil

1995-01-01

315

Microbial degradation of dissolved proteins in seawater  

Microsoft Academic Search

An experimental protocol using radiolabeled proteins was developed to investigate the rates and mechanisms whereby dissolved proteins are degraded in natural marine plankton communities. The results of field observations and laboratory experiments indicate that proteins are degraded by a particle-bound, thermolabile system, presumably bacteria-associated enzymes, with an apparent half-saturation constant of ca. 25 ..mu..g bovine serum albumin (BSA) per liter.

J. T. Hollibaugh; F. Azam

1983-01-01

316

Performances of Small-Sized Generator of Ozone-Dissolved Water Using Boron-Doped Diamond Electrodes  

Microsoft Academic Search

A new electrochemical generator of ozone-dissolved water, which is comprised of an electro-conductive diamond electrode and an ion exchange membrane, was evaluated using tap water as source solution, in order to confirm general versatility. Although the current efficiency of tap water became lower than that obtained in the case of pure water, ozone-dissolved water of over 1 mg\\/L could be

Yoshinori Nishiki; Noriyuki Kitaori; Katsuhiko Nakamuro

2011-01-01

317

Dissolved Zinc Measurements Using Shipboard FIA During the 2008 GEOTRACES Cruise  

NASA Astrophysics Data System (ADS)

Zinc concentrations in the open ocean have been measured accurately by only a few investigators due to the extreme difficulties of collecting and processing seawater samples without introducing Zn contamination. Accurate measurements of dissolved Zn are important for understanding the biogeochemical behavior of this important biochemically required element in the open ocean. Historically, reliable samples for dissolved Zn were collected using Teflon-coated GO-FLO bottles individually hung on Kevlar line. To speed up sample collection, two "Trace Metal" rosette systems were tested during Leg 1 of the GEOTRACES 2008 intercalibration cruise: a large GEOTRACES 24-bottle rosette and the smaller Measures and Landing "CLIVAR" 12-bottle rosette. Both rosettes use 12-liter, Teflon-coated GO- FLO bottles equipped with Teflon spigots and modified air-relief fittings, allowing for pressure filtration. Contamination for dissolved Zn was eliminated in the 12-liter Teflon-lined GO-FLO bottles by repeated deployments ("flushing") on both rosette systems. A Flow Injection (FIA) technique for shipboard determination of total dissolved Zn was utilized to test rosette sampling methods for Zn contamination. Samples were acidified to 0.024M HCl (pH 2) for 16 hours. Samples were buffered to pH 5.5 using ammonium acetate buffer. Dissolved Zn was pre-concentrated using a small- volume column of 8-HQ cation exchange resin. After column rinsing, Zn was eluted into the flowing stream of organic reagent p-Tosyl-8-aminoquinoline (pTAQ), which forms fluorescent complexes with Zn. A flow- through fluorometer was used to record peak heights. Calibration was performed via standard additions. Accuracy of this method was established by measuring standard SAFe D2 and S1 samples, as well as multiple samples collected and analyzed throughout Leg 1 of the GEOTRACES 2008 cruise. Dissolved Cadmium (Cd) can additionally form fluorescent complexes with pTAQ. Thus, when necessary, a small, positive, Cd interference can be corrected for using established Cd-PO4 relationships. Dissolved Zn profiles from both rosette systems agree extremely well with previously published Zn data from this region.

Gosnell, K. J.; Landing, W. M.; Milne, A.

2008-12-01

318

Dissolved organic carbon on Georges Bank  

NASA Astrophysics Data System (ADS)

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

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

1996-04-01

319

Dissolution of mercury from dental amalgam at different pH values.  

PubMed

Dissolution of mercury from dental amalgam has been shown to be diminished by the formation of a tin oxide film on the surface of the mercury-rich gamma 1 phase (Marek, 1990b). Since tin oxides dissolve at low pH values (Deltombe et al., 1974), acidic conditions in the oral cavity may cause an increase in the mercury release. The purpose of this study was to determine the effect of acidity in the range of pH 1 to pH 8 on the rate of mercury dissolution in synthetic saliva from tin-free and tin-containing gamma 1 phase and two commercial dental amalgams. The tested hypothesis was that pH affects mercury dissolution only when a protective oxide film dissolves in an acidic environment. After exposures of the specimens for 2 hr or 24 hr in sealed glass bottles, the solutions were analyzed by flameless atomic absorption spectrophotometry for mercury and silver. The results have shown pH-independent mercury dissolution in the range of pH 3 to 8, and a much faster dissolution at pH 1. At all pH values, more mercury dissolved from the tin-free phase than from the tin-containing phase, and the rate of dissolution was lowest for the dental amalgams. The results were affected by the length of the test exposure. The pH independence in a wide range of pH values has been attributed to the atomic mechanism of mercury dissolution. The low rate of mercury dissolution from specimens containing tin has been explained by the formation of a barrier tin oxide film, which dissolved only at the lowest pH. Dissolution of silver at low pH values is believed to have accelerated dissolution of mercury from the tin-free gamma 1 phase. Variation of the dissolution rate with concentration of the dissolved species and kinetics of oxide film dissolution caused the effect of the exposure period. PMID:9168865

Marek, M

1997-06-01

320

Stream diurnal dissolved oxygen profiles as indicators of in-stream metabolism and disturbance effects: Fort Benning as a case study  

Microsoft Academic Search

We investigated whether two characteristics of stream diurnal dissolved oxygen profiles, the daily amplitude and maximum value of the dissolved oxygen saturation deficit, are useful indicators of stream metabolism and the effects of catchment-scale disturbances. The study was conducted at the U.S. Army's Fort Benning installation where vegetation loss and high rates of erosion from intensely used training areas and

Patrick J. Mulholland; Jeffrey N. Houser; Kelly O. Maloney

2005-01-01

321

Factors regulating nitrification in aquatic sediments: effects of organic carbon, nitrogen availability, and pH  

Microsoft Academic Search

We investigated the response in nitrification to organic carbon (C) availability, the interactive effects of the C: nitrogen (N) ratio and organic N availability, and differing pH in sediments from several streams in the upper midwestern United States. In addition, we surveyed 36 streams to assess variability in sediment nitrification rates. Labile dissolved organic carbon (DOC) additions of 30 mg

Eric A. Strauss; Nicole L. Mitchell; Gary A. Lamberti

2002-01-01

322

Uptake of allochthonous dissolved organic matter from soil and ...  

Treesearch

Title: Uptake of allochthonous dissolved organic matter from soil and salmon ... Description: Dissolved organic matter (DOM) is an important component of aquatic food ... DOC, DON, fluorescence, PARAFAC salmon, wetlands, nutrient uptake.

323

Danger from Dissolvable Tobacco and Other Tobacco Products  

MedlinePLUS

... market. In January 2009, R.J. Reynolds introduced Camel Orbs, Strips, and Sticks, its newest dissolvable, smokeless ... them), the novel configuration, packaging, and flavoring of Camel’s new dissolvables prompted Congress to include a requirement ...

324

Changes in dissolved organic matter with depth suggest the ...  

Treesearch

Research into postharvest management of forests often focuses on ... a strong influence over the translocation of carbon (C) into and through the soil ... Keywords: dissolved organic carbon, dissolved organic nitrogen, DOC:DON ratio, forest ...

325

[Change of humic-like fluorescence characteristics of dissolved organic matter from Dagu River to Jiaozhou Bay].  

PubMed

Fluorescence excitation-emission matrix spectroscopy was employed to characterize the change of humic-like fluorescence from Dagu River to Jiaozhou Bay. The relationships of humic-like fluorescence characteristics with salinity, pH, chlorophyll a, dissolved organic carbon, chemical oxygen demand and carbohydrate were discussed. The results show that humic-like fluorescence intensities are high in Dagu River but low in Jiaozhou Bay. The input of Dagu River is important origin of humic-like fluorescent dissolved organic matter of Jiaozhou Bay. High humic-like fluorescence intensity and high chlorophyll a are not coexist always, which suggests that humic-like fluorescent dissolved organic matter doesn't mainly come from phytoplankton. Good relationships of humic-like fluorescence intensity with dissolved organic carbon, chemical organic demand and carbohydrate suggest that humic-like fluorescent matter is the main component of dissolved organic matter. The distribution of humic-like fluorescence reflects the distribution of dissolved organic matter to some extents. PMID:16921937

Ji, Nai-yun; Zhao, Wei-hong; Wang, Jiang-tao; Miao, Hui

2006-06-01

326

Water What-ifs: Water Quality and Dissolved Oxygen  

NSDL National Science Digital Library

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

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

327

Macroscopic observations of the effects of varying fresh water pH on bone.  

PubMed

Little is known about the decomposition of remains in aquatic environments of varying pH, and even less is known about the specific effects of these environments on bone. Bovine bones were placed in solutions of pH 1, 4, 7, 10, and 14 and observed over a period of 1 year. All solutions eventually removed or dissolved the soft tissues from the external surface of the bone. The pH 7 and pH 10 solutions had little effect on the bone, but the other solutions affected the bone to varying degrees. Extreme pH levels were the most destructive, while more moderate pH levels had lesser but significant and interesting effects. Empirical data on postmortem aquatic changes may be extremely useful in forensic contexts for both improving time since death estimates and also for providing better information to underwater recovery experts thereby potentially increasing the quantity and quality of remains recovery. PMID:21342189

Christensen, Angi M; Myers, Sarah W

2010-12-28

328

A simple and rapid method for monitoring dissolved oxygen in water with a submersible microbial fuel cell (SBMFC).  

PubMed

A submersible microbial fuel cell (SBMFC) was developed as a biosensor for in situ and real time monitoring of dissolved oxygen (DO) in environmental waters. Domestic wastewater was utilized as a sole fuel for powering the sensor. The sensor performance was firstly examined with tap water at varying DO levels. With an external resistance of 1000?, the current density produced by the sensor (5.6 ± 0.5-462.2 ± 0.5 mA/m(2)) increased linearly with DO level up to 8.8 ± 0.3mg/L (regression coefficient, R(2)=0.9912), while the maximum response time for each measurement was less than 4 min. The current density showed different response to DO levels when different external resistances were applied, but a linear relationship was always observed. Investigation of the sensor performance at different substrate concentrations indicates that the organic matter contained in the domestic wastewater was sufficient to power the sensing activities. The sensor ability was further explored under different environmental conditions (e.g. pH, temperature, conductivity, and alternative electron acceptor), and the results indicated that a calibration would be required before field application. Lastly, the sensor was tested with different environmental waters and the results showed no significant difference (p>0.05) with that measured by DO meter. The simple, compact SBMFC sensor showed promising potential for direct, inexpensive and rapid DO monitoring in various environmental waters. PMID:22726635

Zhang, Yifeng; Angelidaki, Irini

2012-06-01

329

Integrated versus isolated scenario for prediction dissolved oxygen at progression of water quality monitoring stations  

NASA Astrophysics Data System (ADS)

This study examined the potential of Multi-layer Perceptron Neural Network (MLP-NN) in predicting dissolved oxygen (DO) at Johor River Basin. The river water quality parameters were monitored regularly each month at four different stations by the Department of Environment (DOE) over a period of ten years, i.e. from 1998 to 2007. The following five water quality parameters were selected for the proposed MLP-NN modelling, namely; temperature (Temp), water pH, electrical conductivity (COND), nitrate (NO3) and ammonical nitrogen (NH3-NL). In this study, two scenarios were introduced; the first scenario (Scenario 1) was to establish the prediction model for DO at each station based on five input parameters, while the second scenario (Scenario 2) was to establish the prediction model for DO based on the five input parameters and DO predicted at previous station (upstream). The model needs to verify when output results and the observed values are close enough to satisfy the verification criteria. Therefore, in order to investigate the efficiency of the proposed model, the verification of MLP-NN based on collection of field data within duration 2009-2010 is presented. To evaluate the effect of input parameters on the model, the sensitivity analysis was adopted. It was found that the most effective inputs were oxygen-containing (NO3) and oxygen demand (NH3-NL). On the other hand, Temp and pH were found to be the least effective parameters, whereas COND contributed the lowest to the proposed model. In addition, 17 neurons were selected as the best number of neurons in the hidden layer for the MLP-NN architecture. To evaluate the performance of the proposed model, three statistical indexes were used, namely; Coefficient of Efficiency (CE), Mean Square Error (MSE) and Coefficient of Correlation (CC). A relatively low correlation between the observed and predicted values in the testing data set was obtained in Scenario 1. In contrast, high coefficients of correlation were obtained between the observed and predicted values for the test sets of 0.98, 0.96 and 0.97 for all stations after adopting Scenario 2. It appeared that the results for Scenario 2 were more adequate than Scenario 1, with a significant improvement for all stations ranging from 4 % to 8 %.

Najah, A.; El-Shafie, A.; Karim, O. A.; Jaafar, O.

2011-08-01

330

Integrated versus isolated scenario for prediction dissolved oxygen at progression of water quality monitoring stations  

NASA Astrophysics Data System (ADS)

This study examined the potential of Multi-layer Perceptron Neural Network (MLP-NN) in predicting dissolved oxygen (DO) at Johor River Basin. The river water quality parameters were monitored regularly each month at four different stations by the Department of Environment (DOE) over a period of ten years, i.e. from 1998 to 2007. The following five water quality parameters were selected for the proposed MLP-NN modelling, namely; temperature (Temp), water pH, electrical conductivity (COND), nitrate (NO3) and ammonical nitrogen (NH3-NL). In this study, two scenarios were introduced; the first scenario (Scenario 1) was to establish the prediction model for DO at each station based on five input parameters, while the second scenario (Scenario 2) was to establish the prediction model for DO based on the five input parameters and DO predicted at previous station (upstream). The model needs to verify when output results and the observed values are close enough to satisfy the verification criteria. Therefore, in order to investigate the efficiency of the proposed model, the verification of MLP-NN based on collection of field data within duration 2009-2010 is presented. To evaluate the effect of input parameters on the model, the sensitivity analysis was adopted. It was found that the most effective inputs were oxygen-containing (NO3) and oxygen demand (NH3-NL). On the other hand, Temp and pH were found to be the least effective parameters, whereas COND contributed the lowest to the proposed model. In addition, 17 neurons were selected as the best number of neurons in the hidden layer for the MLP-NN architecture. To evaluate the performance of the proposed model, three statistical indexes were used, namely; Coefficient of Efficiency (CE), Mean Square Error (MSE) and Coefficient of Correlation (CC). A relatively low correlation between the observed and predicted values in the testing data set was obtained in Scenario 1. In contrast, high coefficients of correlation were obtained between the observed and predicted values for the test sets of 0.98, 0.96 and 0.97 for all stations after adopting Scenario 2. It appeared that the results for Scenario 2 were more adequate than Scenario 1, with a significant improvement for all stations ranging from 4 % to 8 %.

Najah, A. A.; El-Shafie, A.; Karim, O. A.; Jaafar, O.

2011-06-01

331

27 CFR 19.455 - Dissolving of denaturants.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Dissolving of denaturants. 19.455 Section...Articles Denaturation § 19.455 Dissolving of denaturants. Denaturants...27 CFR part 21. Any spirits used in dissolving denaturants and contained in the...

2009-04-01

332

27 CFR 19.455 - Dissolving of denaturants.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Dissolving of denaturants. 19.455 Section...Articles Denaturation § 19.455 Dissolving of denaturants. Denaturants...27 CFR part 21. Any spirits used in dissolving denaturants and contained in the...

2010-04-01

333

Dissolved Organic Matter in the Hudson River Plume  

Microsoft Academic Search

As part of the LATTE (Lagrangian Transport and Transformation Experiment) program, dissolved organic carbon (DOC), total nitrogen (TN), and chromophoric dissolved organic matter (CDOM) were measured in the Hudson River Estuary and Plume. As revealed by high resolution measurements from the Integrated Coastal Observation System (ICOS), dissolved organic matter has several sources within the estuary including the Hudson and Raritan

R. F. Chen; G. B. Gardner

2004-01-01

334

Role of structural Fe in nontronite NAu-1 and dissolved Fe(II) in redox transformations of arsenic and antimony  

SciTech Connect

Oxidation state is a major factor affecting the mobility of arsenic (As) and antimony (Sb) in soil and aquatic systems. Metal (hydr)oxides and clay minerals are effective sorbents, and may also promote redox reactions on their surfaces via direct or indirect facilitation of electron transfer. Iron substituted for Al in the octahedral sites of aluminosilicate clay minerals has the potential to be in variable oxidation states and is a key constituent of electron transfer reactions in clay minerals. This experimental work was conducted to determine whether structural Fe in clays can affect the oxidation state of As and Sb adsorbed at the clay surface. Another goal of our study was to compare the reactivity of clay structural Fe(II) with systems containing Fe(II) present in dissolved/adsorbed forms. The experimental systems included batch reactors with various concentrations of As(III), Sb(III), As(V), or Sb(V) equilibrated with oxidized (NAu-1) or partially reduced (NAu-1-Red) nontronite, hydrous aluminum oxide (HAO) and kaolinite (KGa-1b) suspensions under oxic and anoxic conditions. The reaction times ranged from 0.5 to 720 h, and pH was constrained at 5.5 (for As) and at 5.5 or 8.0 (for Sb). The oxidation state of As and Sb in the liquid phase was determined by liquid chromatography in line with an inductively coupled plasma mass spectrometer, and in the solid phase by X-ray absorption spectroscopy. Our findings show that structural Fe(II) in NAu-1-Red was not able to reduce As(V)/Sb(V) under the conditions examined, but reduction was seen when aqueous Fe(II) was present in the systems with kaolinite (KGa-1b) and nontronite (NAu-1). The ability of the structural Fe in nontronite clay NAu-1 to promote oxidation of As(III)/Sb(III) was greatly affected by its oxidation state: if all structural Fe was in the oxidized Fe(III) form, no oxidation was observed; however, when the clay was partially reduced ({approx}20% of structural Fe was reduced to Fe(II)), NAu-1-Red promoted the most extensive oxidation under both oxic and anoxic conditions. Electron balance considerations suggest that structural Fe(III) in the NAu-1-Red was the sole oxidant in the anoxic setup, while dissolved O{sub 2} also contributes in oxic conditions. Long-term batch experiments revealed the complex dynamics of As aqueous speciation in anoxic and oxic systems when reduced arsenic was initially added: rapid disappearance of As(III) was observed due to oxidation to As(V) followed by a slow increase of aqueous As(III). This behavior is explained by two reactions: fast initial oxidation of As(III) by structural Fe(III) (anoxic) or Fe(III) and dissolved O2 (oxic) followed by the slow reduction of As(V) by dissolved Fe(II). The resulting re-mobilization of As due to As(V) reduction by aqueous Fe(II) occurs on time scales on the order of days. These reactions are likely significant in a natural soil or aquifer environment with seasonal cycling or slightly reducing conditions with an abundance of clay minerals and dissolved Fe(II).

Ilgen, Anastasia G.; Foster, Andrea L.; Trainor, Thomas P. (Alaska Fairbanks); (USGS)

2012-11-01

335

Discovery of a natural CO2 seep in the German North Sea: Implications for shallow dissolved gas and seep detection  

NASA Astrophysics Data System (ADS)

A natural carbon dioxide (CO2) seep was discovered during an expedition to the southern German North Sea (October 2008). Elevated CO2 levels of ˜10-20 times above background were detected in seawater above a natural salt dome ˜30 km north of the East-Frisian Island Juist. A single elevated value 53 times higher than background was measured, indicating a possible CO2 point source from the seafloor. Measured pH values of around 6.8 support modeled pH values for the observed high CO2 concentration. These results are presented in the context of CO2 seepage detection, in light of proposed subsurface CO2 sequestering and growing concern of ocean acidification. We explore the boundary conditions of CO2 bubble and plume seepage and potential flux paths to the atmosphere. Shallow bubble release experiments conducted in a lake combined with discrete-bubble modeling suggest that shallow CO2 outgassing will be difficult to detect as bubbles dissolve very rapidly (within meters). Bubble-plume modeling further shows that a CO2 plume will lose buoyancy quickly because of rapid bubble dissolution while the newly CO2-enriched water tends to sink toward the seabed. Results suggest that released CO2 will tend to stay near the bottom in shallow systems (<200 m) and will vent to the atmosphere only during deep water convection (water column turnover). While isotope signatures point to a biogenic source, the exact origin is inconclusive because of dilution. This site could serve as a natural laboratory to further study the effects of carbon sequestration below the seafloor.

McGinnis, Daniel F.; Schmidt, Mark; Delsontro, Tonya; Themann, SöRen; Rovelli, Lorenzo; Reitz, Anja; Linke, Peter

2011-03-01

336

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

NASA Astrophysics Data System (ADS)

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

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

2004-05-01

337

Kaolinite dissolution and precipitation kinetics at 22oC and pH 4  

SciTech Connect

Dissolution and precipitation rates of low defect Georgia kaolinite (KGa-1b) as a function of Gibbs free energy of reaction (or reaction affinity) were measured at 22 C and pH 4 in continuously stirred flowthrough reactors. Steady state dissolution experiments showed slightly incongruent dissolution, with a Si/Al ratio of about 1.12 that is attributed to the re-adsorption of Al on to the kaolinite surface. No inhibition of the kaolinite dissolution rate was apparent when dissolved aluminum was varied from 0 and 60 {micro}M. The relationship between dissolution rates and the reaction affinity can be described well by a Transition State Theory (TST) rate formulation with a Temkin coefficient of 2 R{sub diss} (mol/m{sup 2}s) = 1.15 x 10{sup -13} [1-exp(-{Delta}G/2RT)]. Stopping of flow in a close to equilibrium dissolution experiment yielded a solubility constant for kaolinite at 22 C of 10{sup 7.57}. Experiments on the precipitation kinetics of kaolinite showed a more complex behavior. One conducted using kaolinite seed that had previously undergone extensive dissolution under far from equilibrium conditions for 5 months showed a quasi-steady state precipitation rate for 105 hours that was compatible with the TST expression above. After this initial period, however, precipitation rates decreased by an order of magnitude, and like other precipitation experiments conducted at higher supersaturation and without kaolinite seed subjected to extensive prior dissolution, could not be described with the TST law. The initial quasi-steady state rate is interpreted as growth on activated sites created by the dissolution process, but this reversible growth mechanism could not be maintained once these sites were filled. Long-term precipitation rates showed a linear dependence on solution saturation state that is generally consistent with a two dimensional nucleation growth mechanism following the equation R{sub ppt}(mol/m{sup 2}s) = 3.38 x 10{sup -14} exp[- 181776/T{sup 2} 1n{Omega}]. Further analysis using Synchrotron Scanning Transmission X-ray Microscopy (STXM) in Total Electron Yield (TEY) mode of the material from the precipitation experiments showed spectra for newly precipitated material compatible with kaolinite. An idealized set of reactive transport simulations of the chemical weathering of albite to kaolinite using rate laws from HELLMANN and TISSERAND (2006) and this study respectively indicate that while pore waters are likely to be close to equilibrium with respect to kaolinite at pH 4, significant kaolinite supersaturation may occur at higher pH if its precipitation rate is pH dependent.

Steefel, Carl; Yang, L.; Steefel, C.I.

2008-04-01

338

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

NASA Astrophysics Data System (ADS)

The distribution of dissolved Cd, Cu, and Zn in the Scheldt estuary has been studied during eight axial surveys, carried out between February 1987 and February 1988. The observed metal-salinity profiles depend on the season. During spring and summer, when the river water is anoxic (containing traces of dissolved sulfide), the dissolved metal concentrations in the riverine endmember are extremely low. This observation is ascribed to formation of sparingly soluble metal sulfides in the water column. During winter, when the river water is not totally devoid of oxygen (10-40% saturation), the dissolved Cu and Zn concentrations in the riverine endmember are an order of magnitude higher, but rapid removal is apparent in the very low salinity zone. Flocculation (of organometal complexes) or coagulation (of colloid-associated metals), sediment resuspension and formation of particulate Fe and Mn oxyhydroxides are likely to be involved in the removal process. At higher salinities, maxima of dissolved Zn (at 6-9 × 10 -3), Cu (at 9-18 × 10 -3), and Cd (at 12-21 × 10 -3) are consistently found over the year. These maxima are ascribed to dissolution and desorption of particulate metal forms with increasing salinity. Reoxidation of trace metal sulfides during transport from the anoxic (or suboxic) upper estuary to the fully oxygenated lower estuary is suggested as the first step in the mobilization process. During phytoplankton blooms, desorption of Cd and Zn (but not Cu) is suppressed, which is attributed to the pH increase related to primary production, and to biological uptake. The impact of mobilization processes in the Scheldt estuary is reflected by effective dissolved Cd and Cu concentrations which are much higher than the observed metal concentrations in the river water. Based on these findings, it is expected that restoration of the dissolved oxygen concentration, which is a major goal of the present-day management of the Scheldt estuary, will lead to an increase in the dissolved metal transport to the North Sea.

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

1997-04-01

339

Corrosion control in water supply systems: effect of pH, alkalinity, and orthophosphate on lead and copper leaching from brass plumbing.  

PubMed

This study explored the potential of lead and copper leaching from brass plumbing in the Auckland region of New Zealand. A five-month field investigation, at six representative locations, indicated that Auckland's water can be characterized as soft and potentially corrosive, having low alkalinity and hardness levels and a moderately alkaline pH. More than 90% of the unflushed samples contained lead above the maximum acceptable value (MAV) of 10 microg/L (New Zealand Standards). In contrast, the copper level of unflushed samples remained consistently below the corresponding MAV of 2 mg/L. Flushing however reduced sharply metal concentrations, with lead values well below the MAV limit. Generally, metal leaching patterns showed a limited degree of correlation with the variations in temperature, dissolved oxygen and free chlorine residual at all sampling locations. Furthermore, a series of bench-scale experiments was conducted to evaluate the effectiveness of pH and alkalinity adjustment, as well as orthophosphate addition as corrosion control tools regarding lead and copper dissolution. Results demonstrated that lead and copper leaching was predominant during the first 24 hr of stagnation, but reached an equilibrium state afterwards. Since the soluble fraction of both metals was small (12% for lead, 29% for copper), it is apparent that the non-soluble compounds play a predominant role in the dissolution process. The degree of leaching however was largely affected by the variations in pH and alkalinity. At pH around neutrality, an increase in alkalinity promoted metal dissolution, while at pH 9.0 the effect of alkalinity on leaching was marginal. Lastly, addition of orthophosphate as a corrosion inhibitor was more effective at pH 7.5 or higher, resulting in approximately 70% reduction in both lead and copper concentrations. PMID:19847713

Tam, Y S; Elefsiniotis, P

2009-10-01

340

The measurement of dissolved and gaseous carbon dioxide concentration  

NASA Astrophysics Data System (ADS)

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

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

2011-07-01

341

Lowering of cytoplasmic pH is essential for growth of Streptococcus faecalis at high pH.  

PubMed Central

The growth of Streptococcus faecalis at high pH was significantly stimulated by carbonate. In the absence of added carbonate the cells were unable to grow at a pH above 9.5, but in media containing 50 mM HCO3- they grew even at pH 10.5. Both rate and yield of growth at pH 9.5 were significantly stimulated by as little as 5 mM carbonate. The cytoplasmic pH in growing cells was maintained at about 7.8 to 8.2, whereas the medium pH ranged from 8.4 to 9.5. Nigericin and gramicidin D, ionophores which conduct protons, blocked growth at pH 9.5 but not at pH 7.5. These results indicate that lowering of the cytoplasmic pH is essential for the growth of this organism at high pH.

Kakinuma, Y

1987-01-01

342

[Fluorescence characteristics of dissolved organic matter during algal bloom in Jiaozhou Bay].  

PubMed

Fluorescence excitation-emission matrix spectroscopy (EEMS) was employed to characterize the dissolved organic matter (DOM) in algal bloom seawater of Jiaozhou Bay in February, 2004. The relationships of DOM fluorescence characteristics with phytoplankton multiplication, dissolved organic carbon (DOC), salinity, dissolved oxygen and pH were discussed. In addition, the protein-like and humic-like fluorescence changes fore and aft cross-flow ultrafiltration (CFF) were primarily evaluated. The results show that the intensities of high and low-excitation protein-like fluorescence, which have the same sources, are stronger than that of humic-like during algal bloom. Both correlations between protein-like fluorescence intensities and chlorophyll-a and between humic-like fluorescence intensities and chlorophyll-a are relevant to the phytoplankton multiplication. As a whole, the fluorescence intensities of protein-like and humic-like increases with chlorophyll-a increasing. Furthermore the ratios of new to old DOM increase with phytoplankton biomass increasing. Good positive correlations between protein-like fluorescence intensities and DOC and between the ratios of protein-like to humic-like fluorescence intensities and DOC suggest that the DOC is mainly composed of newly produced matter during algal bloom. Some inorganic factors, such as salinity, dissolved oxygen and pH, have little effects on protein-like and humic-like fluorescence. Fore and aft the CFF experiments, the positions of protein-like and humic-like fluorescence peaks have little alteration, the balance of fluorescence intensity is not so good as organic carbon mass balance as a whole. Fluorescence balance should be used only as a supplementary technique for evaluating contaminations or loss by organic carbon mass balance. PMID:16686185

Ji, Nai-yun; Zhao, Wei-hong; Wang, Jiang-tao; Cui, Xin; Miao, Hui

2006-02-01

343

Coefficients for estimating SAR from soil pH and EC data and calculating pH from SAR and EC values in salinity models  

Microsoft Academic Search

Data from highly weathered, low pH, sodic Australian soils have been used to develop a method for estimating soil exchangeable sodium percentage (ESP) or soil extract sodium adsorption ratio (SAR) from soil pH and electrical conductivity (EC) data. The method can also be used to calculate soil pH in soil salinity models using SAR and EC values. The pH was

Charles W. Robbins

1993-01-01

344

Experimental study of igneous and sedimentary apatite dissolution - Control of pH, distance from equilibrium, and temperature on dissolution rates  

NASA Astrophysics Data System (ADS)

Apatite dissolution experiments were conducted using both a fluidized bed and stirred tank reactor over a range of pH, temperature, solution saturation state, and on non-carbonated and carbonated apatite compositions: igneous fluorapatite (FAP) and sedimentary carbonate fluorapatite (CFA), respectively. From 2 <pH <6, the rate of release from dissolution of all apatite components [calcium (Ca), phosphorus (P), and fluoride (F)] increased with decreasing pH for FAP. From 6 < pH < 8.5, the FAP dissolution rate is pH independent. Measuring apatite dissolution rates at pH > 8.5 were not possible due to detection limits of the analytical techniques used in this study and the high insolubility of FAP. For the CFA compositions studied, the dissolution rate decreased with increasing pH from 4 < pH < 7. During early stages of the dissolution reaction for both FAP and CFA, mineral components were released in non-stoichiometric ratios with reacted solution ratios of dissolved Ca:P and Ca:F being greater than mineral stoichiometric ratios, suggesting that Ca was preferentially released compared to P and F from the mineral structure during the early stages of dissolution. An increase in reacted solution pH accompanies this early elevated release of Ca. As the dissolution reaction proceeded to steady state, dissolution became congruent. When normalized to BET measured surface area, FAP dissolved faster from 4 < pH < 7 compared to CFA. The apparent Arrhenius activation energy (E a) of FAP dissolution over the temperature range of 25-55°C at pH = 3.0, I = 0.1, and pCO 2 = 0 is 8.3 ± 0.2 kcal mol -1. Both the apparent exchange of solution H + for solid-bound Ca at low pH in the early stage of dissolution and the E a of dissolution suggest a surface and not a diffusion controlled dissolution reaction for FAP and CFA. The degree of undersaturation of the solution, ?G R, with respect to FAP was important in determining the dissolution rate. At pH = 3.0, I = 0.1, and pCO 2 = 0, the dissolution rate of FAP was ˜ 5× greater in the far-from-equilibrium region compared to the near-equilibrium slope region. A simple apatite weathering model incorporating the experimental results from this study was constructed, and numerical calculations suggest that during the Phanerozoic both the surface area of igneous rock available for weathering and the average global temperature were important factors in determining the P weathering flux from apatite dissolution. It is possible that elevated global temperatures coupled with relatively high surface area of igneous rock during the early- to mid-Paleozoic resulted in elevated P weathering fluxes, which along with climatic evolutionary pressures of the Neoproterozoic, facilitated the radiation of multicellular organisms, large-scale phosphorite deposition, and abundance of calcium phosphate shelled organisms during the early Cambrian.

Guidry, Michael W.; Mackenzie, Fred T.

2003-08-01

345

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

NASA Astrophysics Data System (ADS)

Dissolved silica concentrations in western Virginia streams showed a significant bias toward declines (p<0.0001) over the time period from 1988-2003. Streams with the greatest declines were those that had the highest mean dissolved silica concentrations, specific to watersheds underlain by basaltic and granitic bedrock. We examined potential geochemical, hydrological, and biological factors that could account for the observed widespread declines, focusing on six core watersheds where weekly stream chemistry data were available. No relationships were evident between stream water dissolved silica concentrations and pH, a finding supported by the results from a geochemical model applied to the dominant bedrock mineralogy. Along with changes in watershed acidity, changes in precipitation and discharge were also discounted since no significant trends were observed over the study period. Analyses of two longer-term datasets that extend back to 1979 revealed that the initiation of the dissolved silica declines coincided with the timing of a gypsy moth (Lymantria dispar) defoliation event. We develop a conceptual model centered on benthic diatoms, which are found within each of the six core watersheds but in greater abundance in the more silica-rich streams. Gypsy moth defoliation lead to greater sunlight penetration and enhanced nitrate concentrations in the streams, which could have spurred population growth and silica uptake. The model can explain why the observed declines are primarily driven by decreased concentrations during low-flow conditions. This study illustrates lasting effects of disturbance on watershed biogeochemistry, in this case causing decadal-scale variability in stream water dissolved silica concentrations.

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

2006-12-01

346

The conductivity of hydrocarbon transformer oil containing water and solid conducting particles  

Microsoft Academic Search

The d.c. resistivity test is used to determine the quality of transformer oil in service. It is found that water droplets in oil oscillate between the measuring electrodes in a d.c. field, transferring charge and giving rise to a high conductivity. As the test temperature is raised, oil dissolves more water and the quantity held in suspension decreases with consequent

A W Stannett

1951-01-01

347

Preservation of samples for dissolved mercury  

SciTech Connect

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

Hamlin, S.N. (Geological Survey, Sacramento, CA (United States))

1989-04-01

348

Dissolved-oxygen analysis with temperature dependence  

SciTech Connect

Water-quality models to predict oxygen dynamics in streams require estimates of rates of reaeration, respiration, and primary production, which are often evaluated through diel studies. Simple, approximate methods of parameter estimation are desirable at the scoping level, and are often used for waste-load allocation studies. Scoping methods often assume that reaeration and respiration are constant over the diel period. Use of such methods, however, can yield unrealistic parameter estimates for shallow streams with a significant range of diel water temperatures, because both reaeration and respiration rates as well as the saturation concentration of dissolved oxygen are temperature-dependent. Based on this work on the Santa Margarita River in Southern California, this paper presents a modified approach to dissolved-oxygen-rate parameter estimation that takes temperature variation into account. Using a simple finite-difference approximation, temperature-normalized parameter estimates are readily optimized in a spreadsheet application. The approach is applicable to many shallow streams in which diel temperature variability is significant.

Butcher, J.B. [Cadmus Group, Durham, NC (United States); Covington, S. [Cadmus Group, Laramie, WY (United States)

1995-10-01

349

PH as a stress signal  

Microsoft Academic Search

The pH of the xylem sap of plants experiencing a range of environmental conditions can increase by over a whole pH unit. This results in an increased ABA concentration in the apoplast adjacent to the stomatal guard cells in the leaf epidermis, by reducing the ability of the mesophyll and epidermal symplast to sequester ABA away from this compartment. As

Sally Wilkinson

1999-01-01

350

The pH Game.  

ERIC Educational Resources Information Center

Describes a game that can be used to teach students about the acidity of liquids and substances around their school and enable them to understand what pH levels tell us about the environment. Students collect samples and measure the pH of water, soil, plants, and other natural material. (DDR)

Chemecology, 1996

1996-01-01

351

The pH Game.  

ERIC Educational Resources Information Center

|Describes a game that can be used to teach students about the acidity of liquids and substances around their school and enable them to understand what pH levels tell us about the environment. Students collect samples and measure the pH of water, soil, plants, and other natural material. (DDR)|

Chemecology, 1996

1996-01-01

352

Carbon system measurements and potential climatic drivers at a site of rapidly declining ocean pH.  

PubMed

We explored changes in ocean pH in coastal Washington state, USA, by extending a decadal-scale pH data series, by reporting independent measures of dissolved inorganic carbon (DIC), spectrophotometric pH, and total alkalinity (TA), by exploring pH patterns over larger spatial scales, and by probing for long-term trends in environmental variables reflecting potentially important drivers of pH. We found that pH continued to decline in this area at a rapid rate, that pH exhibited high natural variability within years, that our measurements of pH corresponded well to spectrophotometric pH measures and expected pH calculated from DIC/TA, and that TA estimates based on salinity predicted well actual alkalinity. Multiple datasets reflecting upwelling, including water temperature, nutrient levels, phytoplankton abundance, the NOAA upwelling index, and data on local wind patterns showed no consistent trends over the period of our study. Multiple datasets reflecting precipitation change and freshwater runoff, including precipitation records, local and regional river discharge, salinity, nitrate and sulfate in rainwater, and dissolved organic carbon (DOC) in rivers also showed no consistent trends over time. Dissolved oxygen did not decline over time, indicating that long-term changes did not result from shifts in contributions of respiration to pH levels. These tests of multiple potential drivers of the observed rapid rate of pH decline indicate a primary role for inorganic carbon and suggest that geochemical models of coastal ocean carbon fluxes need increased investigation. PMID:23285290

Wootton, J Timothy; Pfister, Catherine A

2012-12-28

353

Carbon System Measurements and Potential Climatic Drivers at a Site of Rapidly Declining Ocean pH  

PubMed Central

We explored changes in ocean pH in coastal Washington state, USA, by extending a decadal-scale pH data series, by reporting independent measures of dissolved inorganic carbon (DIC), spectrophotometric pH, and total alkalinity (TA), by exploring pH patterns over larger spatial scales, and by probing for long-term trends in environmental variables reflecting potentially important drivers of pH. We found that pH continued to decline in this area at a rapid rate, that pH exhibited high natural variability within years, that our measurements of pH corresponded well to spectrophotometric pH measures and expected pH calculated from DIC/TA, and that TA estimates based on salinity predicted well actual alkalinity. Multiple datasets reflecting upwelling, including water temperature, nutrient levels, phytoplankton abundance, the NOAA upwelling index, and data on local wind patterns showed no consistent trends over the period of our study. Multiple datasets reflecting precipitation change and freshwater runoff, including precipitation records, local and regional river discharge, salinity, nitrate and sulfate in rainwater, and dissolved organic carbon (DOC) in rivers also showed no consistent trends over time. Dissolved oxygen did not decline over time, indicating that long-term changes did not result from shifts in contributions of respiration to pH levels. These tests of multiple potential drivers of the observed rapid rate of pH decline indicate a primary role for inorganic carbon and suggest that geochemical models of coastal ocean carbon fluxes need increased investigation.

Wootton, J. Timothy; Pfister, Catherine A.

2012-01-01

354

Copper binding by dissolved organic matter. I. Suwannee River fulvic acid equilibria  

Microsoft Academic Search

A cupric ion-selective electrode measured free Cu in solutions of Suwannee River fulvic acid (FA) in a series of 30 titrations carried out both at variable and at constant (5.14, 7.00, 8.44) pH. Total Cu varied 0.1-100 ..mu..m, dissolved organic carbon (DOC) 1-10 mg C\\/l, Ca and Mg 0-10 mM, and ionic strength 0.005-0.1. Copper complexation by FA is first

S. E. Cabaniss; M. S. Shuman

1988-01-01

355

Adsorption kinetics of natural dissolved organic matter and its impact on arsenic(V) leachability from arsenic-loaded ferrihydrite and Al-ferrihydrite  

Microsoft Academic Search

The present work was broadly divided into two parts: first, the efficiency of synthetically prepared ferrihydrite and Al-ferrihydrite to adsorb dissolved organic matter (DOM) was tested as a function of time, pH and ionic strength and its effects on specific surface area was found. In the second part, the effect of DOM concentration and solution pH was studied to elucidate

Debasish Mohapatra; Debaraj Mishra; Manmath Rout; Gautam R. Chaudhury

2007-01-01

356

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

Microsoft Academic Search

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

Kunio Kaiho

1994-01-01

357

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

SciTech Connect

At the request of the U.S. Army Corps of Engineers (Portland District), Pacific Northwest National Laboratory (PNNL) conducted research to determine whether total dissolved gas concentrations are elevated in chum salmon redds during spring spill operations at Bonneville Dam. The study involved monitoring the total dissolved gas levels at egg pocket depth and in the river at two chum salmon spawning locations downstream from Bonneville Dam. Dissolved atmospheric gas supersaturation generated by spill from Bonneville Dam may diminish survival of chum (Oncorhynchus keta) salmon when sac fry are still present in the gravel downstream from Bonneville Dam. However, no previous work has been conducted to determine whether total dissolved gas (TDG) levels are elevated during spring spill operations within incubation habitats. The guidance used by hydropower system managers to provide protection for pre-emergent chum salmon fry has been to limit TDG to 105% after allowing for depth compensation. A previous literature review completed in early 2006 shows that TDG levels as low as 103% have been documented to cause mortality in sac fry. Our study measured TDG in the incubation environment to evaluate whether these levels were exceeded during spring spill operations. Total dissolved gas levels were measured within chum salmon spawning areas near Ives Island and Multnomah Falls on the Columbia River. Water quality sensors screened at egg pocket depth and to the river were installed at both sites. At each location, we also measured dissolved oxygen, temperature, specific conductance, and water depth to assist with the interpretation of TDG results. Total dissolved gas was depth-compensated to determine when levels were high enough to potentially affect sac fry. This report provides detailed descriptions of the two study sites downstream of Bonneville Dam, as well as the equipment and procedures employed to monitor the TDG levels at the study sites. Results of the monitoring at both sites are then presented in both text and graphics. The findings and recommendations for further research are discussed, followed by a listing of the references cited in the report.

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

2007-01-30

358

Mössbauer evidence of rapid pyrite formation during the interaction of dissolved sulfide and lepidocrocite  

NASA Astrophysics Data System (ADS)

Mössbauer spectroscopy has been applied to study mineral transformation during the interaction between lepidocrocite and dissolved sulphide with two different initial concentration ratios. Synthetic lepidocrocite enriched with the Mössbauer sensitive isotope Fe-57 was reacted with dissolved sulphide at neutral pH in an anoxic glove box, the initial molar ratios of iron and sulphide being 3.125 and 0.5, respectively. Solid samples for Mössbauer analysis were collected by filtration at different time steps after 15 min, 2hrs, 48hrs, 72hrs and 1 week for the 3.125 iron-sulphide ratio; and after 72hrs and 1 week for the 0.5 iron-sulphide ratio. Dissolved and solid phase ferrous iron, dissolved sulphide and elemental sulphur were measured with wet chemistry analysis techniques in parallel runs. Mössbauer spectra provide evidence for rapid pyrite formation within 48hrs during the reaction at an initial molar ratio of 3.125. Pyrite formation was accompanied by a decrease of elemental sulphur and mackinawite, which is the main iron intermediate product with minor pyrrhotite and magnetite. At the ratio of 3.125, excess lepidocrocite existed and dissolved sulphide was completely consumed after 15min. Acid extractable Fe(II) concentration was in excess of that of Fe(II) bonded as FeS, which has been reported before[1,2] and the difference of the two iron species was defined as excess Fe(II)[2]. In the experiment with an initial ratio of 0.5, lepidocrocite was completely transferred to mackinawite. In this system dissolved sulphide was not completely consumed even after 1 week. No pyrite could be detected. Species including elemental sulphur and mackinawite were stable in 1 week without any further transformation. The long term preservation of unstable iron sulphide minerals at a low concentration of dissolved sulphide is consistent with the observation in marine sediment [3]. These experiments show an important linkage between rapid pyrite formation and surplus lepidocrocite and/or the excess Fe(II) formed during reaction. Together with wet chemistry analysis results we propose that some of the electrons donated by sulphide oxidation are preserved temporally in the lepidocrocite bulk and lead to formation of the excess Fe(II) fraction and ultimately rapid pyrite formation. [1] Poulton et al.(2004) Geochim. Cosmochim. Acta. [2] Hellige et al. (2011) Geochim. Cosmochim. Acta. [3] Gognon et al. (1995) Geochim. Cosmochim. Acta.

Wan, M.; Shröder, C.; Peiffer, S.

2012-04-01

359

Photolytic processing of secondary organic aerosols dissolved in cloud droplets.  

PubMed

The effect of UV irradiation on the molecular composition of aqueous extracts of secondary organic aerosol (SOA) was investigated. SOA was prepared by the dark reaction of ozone and d-limonene at 0.05-1 ppm precursor concentrations and collected with a particle-into-liquid sampler (PILS). The PILS extracts were photolyzed by 300-400 nm radiation for up to 24 h. Water-soluble SOA constituents were analyzed using high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) at different stages of photolysis for all SOA precursor concentrations. Exposure to UV radiation increased the average O/C ratio and decreased the average double bond equivalent (DBE) of the dissolved SOA compounds. Oligomeric compounds were significantly decreased by photolysis relative to the monomeric compounds. Direct pH measurements showed that acidic compounds increased in abundance upon photolysis. Methanol reactivity analysis revealed significant photodissociation of molecules containing carbonyl groups and the formation of carboxylic acids. Aldehydes, such as limononaldehyde, were almost completely removed. The removal of carbonyls was further confirmed by the UV/Vis absorption spectroscopy of the SOA extracts where the absorbance in the carbonyl n??* band decreased significantly upon photolysis. The effective quantum yield (the number of carbonyls destroyed per photon absorbed) was estimated as ?0.03. The total concentration of peroxides did not change significantly during photolysis as quantified with an iodometric test. Although organic peroxides were photolyzed, the likely end products of photolysis were smaller peroxides, including hydrogen peroxide, resulting in a no net change in the peroxide content. Photolysis of dry limonene SOA deposited on substrates was investigated in a separate set of experiments. The observed effects on the average O/C and DBE were similar to the aqueous photolysis, but the extent of chemical change was smaller in dry SOA. Our results suggest that biogenic SOA dissolved in cloud and fog droplets will undergo significant photolytic processing on a time scale of hours to days. This type of photolytic processing may account for the discrepancy between the higher values of O/C measured in the field experiments relative to the laboratory measurements on SOA in smog chambers. In addition, the direct photolysis of oligomeric compounds may be responsible for the scarcity of their observation in the field. PMID:21617794

Bateman, Adam P; Nizkorodov, Sergey A; Laskin, Julia; Laskin, Alexander

2011-05-26

360

Carbon isotope fractionation of dissolved inorganic carbon (DIC) due to outgassing of carbon dioxide from a headwater stream  

Microsoft Academic Search

The stable isotopic composition of dissolved inorganic carbon (?13C-DIC) was investigated as a potential tracer of streamflow generation processes at the Sleepers River Research Watershed, Vermont, USA. Downstream sampling showed ?13C-DIC increased between 3-5‰ from the stream source to the outlet weir approximately 0Ð5 km downstream, concomitant with increasing pH and decreasing PCO2. An increase in ?13C-DIC of 2Ð4 š

Daniel H; Carol Kendall; Stephen D. Sebestyen; James B. Shanley; Nobuhito Ohte; Elizabeth W. Boyer

2008-01-01

361

Polyacrylonitrile-grafted Plantago psyllium mucilage for the removal of suspended and dissolved solids from tannery effluent  

Microsoft Academic Search

Grafted copolymer of Plantago psyllium mucilage and acrylonitrile (Psy– g–PAN) has been synthesized in the presence of nitrogen using a ceric ion–nitric acid redox system. The solid removal efficiency of this copolymer was tested with tannery effluent. The suitable pH, optimum dose of polymer and contact time for the maximum removal of suspended (SS) and dissolved solids (TDS) are reported.

A. Mishra; A. Yadav; M. Agarwal; S. Rajani

2004-01-01

362

A novel biosensor for specific determination of hydrogen peroxide: catalase enzyme electrode based on dissolved oxygen probe  

Microsoft Academic Search

A biosensor for the specific determination of hydrogen peroxide was developed using catalase (EC 1.11.1.6) in combination with a dissolved oxygen probe. Catalase was immobilized with gelatin by means of glutaraldehyde and fixed on a pretreated teflon membrane served as enzyme electrode. The electrode response was maximum when 50 mM phosphate buffer was used at pH 7.0 and at 35°C.

Sinan Akgöl; Erhan Dinçkaya

1999-01-01

363

Extraction equilibrium of manganese(II) from sulfate solutions by di(2-ethylhexyl)phosphoric acid dissolved in kerosene  

Microsoft Academic Search

The distribution ratios of manganese(II) extracted from an aqueous sulfate medium by di(2-ethylhexyl)phosphoric acid (D2EHPA) dissolved in kerosene were studied at 25°C. The extraction equilibria are influenced by the total extractant concentration in the organic phase, equilibrium pH values and total sulfate concentration in the aqueous phase. The distribution data have been analyzed both graphically and numerically. The results show

Hung-Hsin Tsai; Teh-Hua Tsai

2011-01-01

364

Negative pH and extremely acidic mine waters from Iron Mountain, California  

SciTech Connect

Extremely acidic mine waters with pH values as low as {minus}3.6, total dissolved metal concentrations as high as 200 g/L, and sulfate concentrations as high as 760 g/L, have been encountered underground in the Richmond Mine at Iron Mountain, CA. These are the most acidic waters known. The pH measurements were obtained by using the Pitzer method to define pH for calibration of glass membrane electrodes. The calibration of pH below 0.5 with glass membrane electrodes becomes strongly nonlinear but is reproducible to a pH as low as {minus}4. Numerous efflorescent minerals were found forming from these acid waters. These extreme acid waters were formed primarily by pyrite oxidation and concentration by evaporation with minor effects from aqueous ferrous iron oxidation and efflorescent mineral formation.

Nordstrom, D.K.; Alpers, C.N.; Ptacek, C.J.; Blowes, D.W.

2000-01-15

365

Interactive Effects of Soil ph, Halosulfuron Rate, and Application Method on Carryover to Turnip Green and Cabbage.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Field studies were conducted in 2006 and 2007 to evaluate the tolerance of autumn-planted cabbage and turnip green to halosulfuron applied the previous spring to cantaloupe. Main plots were three levels of soil pH; maintained at a natural pH level, pH raised with Ca(OH)2, and pH lowered with Al2(SO...

366

PhET Simulation: Microwaves  

NSDL National Science Digital Library

This is an interactive simulation on the topic of microwave radiation. Users adjust the frequency and amplitude of microwaves in an oven-shaped cavity and watch water molecules rotate, bounce, and behave as dipoles. They can view the microwave field as a wave, a single line of vectors, or the entire field. This item is part of a larger and growing collection by the Physics Education Technology Project (PhET). Each PhET resource was developed using principles from physics education research. SEE RELATED MATERIALS BELOW for an activity designed by the PhET team specifically for use with the Microwaves simulation.

2008-10-30

367

Rapid dissolving polymer compositions and uses therefor  

SciTech Connect

This patent describes a method for imparting anti-misting properties to a fuel suitable for use on turbine and diesel engines comprising: adding to the fuel a rapid dissolving particulate polymer composition in an amount sufficient to substantially eliminate that population of fuel droplets having a diameter of less than about 50 micrometers normally produced when pure fuel is subjected to wind shear, the particles of the polymer composition having a central core consisting of a high molecular weight thermoplastic polymer which imparts viscoelastic properties to a solution of the polymer in the fuel, the central core having clean surfaces and being surrounded by a multilayer shell of an adherent, particulate, coating agent selected from the group consisting of tricalcium phosphate and graphite having a particle size much smaller than that of the central core and having the interstices between the coating agent particles and around the core filled with an inert gas.

O'Mara, D.P.; Hadermann, A.F.; Trippe, J.C.

1988-12-06

368

Method for dissolving delta-phase plutonium  

DOEpatents

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

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

1992-01-01

369

DGT measurement of dissolved aluminum species in waters: comparing Chelex-100 and titanium dioxide-based adsorbents.  

PubMed

Aluminum is acutely toxic, and elevated concentrations of dissolved Al can have detrimental effects on both terrestrial and aquatic ecosystems. Robust analytical methods that can determine environmentally relevant Al fractions accurately and efficiently are required by the environmental monitoring community. A simple, robust passive sampling method, the diffusive gradients in thin films (DGT) technique, was evaluated for the measurement of dissolved Al species in freshwater and marine water using either Chelex-100 or Metsorb (a titanium dioxide-based binding agent) as the adsorbent. Mass vs time DGT deployments at pH 5.05 (Al(3+) and Al(OH)(2+) dominate) and 8.35 (Al(OH)(4)(-) dominates) demonstrated linear uptake of Al (R(2) = 0.989 and 0.988, respectively) for Metsorb. Similar deployments of Chelex-DGT showed linear uptake at pH 5.05 (R(2) = 0.994); however, at pH 8.35 the mass of Al accumulated was 40-70% lower than predicted, suggesting that Chelex-100 is not suitable for Al measurements at high pH. The Metsorb-DGT measurement was independent of pH (5.0-8.5) and ionic strength (0.001-0.7 mol L(-1) NaNO(3)), whereas the Chelex-DGT measurement was only independent of ionic strength at pH 5.0. At pH 8.4, increasing ionic strength led to considerable underestimation (up to 67%) of Al concentration. Deployments of Metsorb-DGT (up to 4 days) in synthetic freshwater (pH range 5.4-8.1) and synthetic seawater (pH 8.15) resulted in linear mass uptakes, and the concentration measured by DGT agreed well with solution concentrations. Conversely, deployment of Chelex-DGT in synthetic seawater and freshwater (pH ?7.7 Al(OH)(4)(-) dominant species) resulted in a decrease in accumulated mass with increasing deployment time. In situ field evaluations in fresh, estuarine, and marine waters confirmed that Metsorb-DGT was more accurate than Chelex-DGT for the measurement of dissolved Al in typical environmental waters. PMID:22268706

Panther, Jared G; Bennett, William W; Teasdale, Peter R; Welsh, David T; Zhao, Huijun

2012-02-06

370

Measurement of CO2 Dissolved in Aqueous Solutions Using a Modified Infrared Gas Analyzer System 1  

PubMed Central

Total dissolved inorganic carbon (?CO2) and aqueous carbon dioxide (H2CO3*) in nutrient solutions may be measured by the injection of small gas or liquid samples (1 microliter to 8 milliliters) into a gas stripping column connected in-line with an infrared gas analyzer. The measurement of ?CO2 in solution requires sample acidification, while H2CO3* and gaseous CO2 are measured without the addition of lactic acid. The standard curve for ?CO2 was linear up to 300 nanomoles CO2. Maximum sensitivity was approximately 300 picomoles. Measurements of H2CO3* were independent of pH. Consequently, ?CO2 and H2CO3* could be used to calculate the pH, HCO3?, and CO32? values of nutrient solutions. Injection and complete analyses required from 0.8 to 2 minutes.

Schumacher, Thomas E.; Smucker, Alvin J. M.

1983-01-01

371

The Complexities of Conducting Ethnographic Race Research  

ERIC Educational Resources Information Center

|This paper explores the challenges and dilemmas of conducting ethnographic race research in the context of the South African situation, forming part of my ethnographic race research PhD project, conducted in two historically white, single-sex schools in South Africa. First, it critically examines the theoretical dilemmas on crucial issues of…

Klaas, Jongi

2006-01-01

372

Oxidative dissolution of 4C- and NC-pyrrhotite: Intrinsic reactivity differences, pH dependence, and the effect of anisotropy  

NASA Astrophysics Data System (ADS)

The crystallographic diversity of pyrrhotite (Fe1-xS), one of the most common iron sulfide minerals, offers insights into how mineral-fluid interactions are controlled by crystal structures. We have conducted oxidative dissolution experiments on monoclinic 4C-pyrrhotite and 'hexagonal' NC-pyrrhotite in aqueous H2O2/H2SO4 and FeCl3/HCl media at pH between 1.8 and 2.9 using polished surfaces of single crystals. Quantification and detailed characterization of the reaction interfaces has been accomplished by confocal 3D topometry and transmission electron microscopy (TEM) in conjunction with focused ion beam (FIB) preparation. Crystallographically coherent intergrowths of 4C- and NC-pyrrhotite in a single sample allowed unambiguous identification of strong intrinsic reactivity differences between the two closely related phases. On {1 1 0} faces in the H2O2 medium at 35 °C and pH below 2.70, NC-pyrrhotite (N ˜ 4.85) reacts about 50-80% faster than 4C-pyrrhotite. Above pH 2.70, the behavior inverts and 4C-pyrrhotite dissolves faster, while overall reaction rates drop drastically by up to two orders of magnitude. Because the two pyrrhotite phases show only marginally different Fe/S ratios but substantial differences in structural complexity with regards to vacancy ordering, we attribute the reactivity differences to structurally controlled processes at the mineral-water interface. The transition at pH 2.70 is close to the reported isoelectric point of pyrrhotite. We attribute the pH dependent changes in reaction rates and behaviors to protonation/deprotonation of surface sulfhydryl groups and related changes in speciation and bonding mode of reactive oxygen species at the mineral interface. At pH <2.70, we find elemental sulfur as a frequent reaction product in H2O2 and FeCl3 media, indicating incomplete sulfur oxidation. Above pH 2.70, elemental sulfur was not found in H2O2 experiments (no data for FeCl3). Our results show that the effects of crystal anisotropy are strong and directional preference of dissolution changes at the pH 2.70 transition point as well, leading to complex sub-?m-scale textural development at the reaction interfaces throughout the pH range studied. High resolution TEM imaging of cross sections through reacted mineral surfaces show crystalline pyrrhotite up to the reaction interface and the absence of significant non-equilibrium layers or S-enriched (poly)sulfides.

Harries, Dennis; Pollok, Kilian; Langenhorst, Falko

2013-02-01

373

Correlation of the partitioning of dissolved organic matter fractions with the desorption of Cd, Cu, Ni, Pb and Zn from 18 Dutch soils  

Microsoft Academic Search

Eighteen Dutch soils were extracted in aqueous solutions at varying pH. Extracts were analyzed for Cd, Cu, Ni, Pb and Zn by ICP-AES. Extract dissolved organic carbon (DOC) was also concentrated onto a macroreticular resin and fractionation into three operationally defined fractions: hydrophilic acids (Hyd), humic acids (HA) and fulvic acids (FA). In this manner, change in absolute solution concentration

Christopher A Impellitteri; Yuefeng Lu; Jennifer K Saxe; Herbert E Allen; Willie J. G. M Peijnenburg

2002-01-01

374

Crystallization and transformation of vaterite at controlled pH  

NASA Astrophysics Data System (ADS)

Precipitated calcium carbonate particles were prepared by passing CO2/N2 mixed gases into CaCl2 solution. The nucleation, crystallization and transformation of vaterite at controlled pH were investigated in this paper. The control of pH was conducted by the addition of ammonia. The results showed that addition of ammonia induced a local high supersaturation and continuous nuclei formation, which is in favor of the growth and agglomeration of vaterite nuclei while inhibiting the transformation of vaterite to calcite. The nearly pure vaterite is ready to form at the control of pH.

Sheng Han, Yong; Hadiko, Gunawan; Fuji, Masayoshi; Takahashi, Minoru

2006-03-01

375

Effect of pH on the concentrations of lead and trace contaminants in drinking water: a combined batch, pipe loop and sentinel home study.  

PubMed

High lead levels in drinking water are still a concern for households serviced by lead pipes in many parts of North America and Europe. This contribution focuses on the effect of pH on lead concentrations in drinking water delivered through lead pipes. Though this has been addressed in the past, we have conducted a combined batch, pipe loop and sentinel study aiming at filling some of the gaps present in the literature. Exhumed lead pipes and water quality data from the City of London's water distribution system were used in this study. As expected, the lead solubility of corrosion scale generally decreased as pH increased; whereas dissolution of other accumulated metals present in the corrosion scale followed a variety of trends. Moreover, dissolved arsenic and aluminum concentrations showed a strong correlation, indicating that the aluminosilicate phase present in the scale accumulates arsenic. A significant fraction of the total lead concentration in water was traced to particulate lead. Our results indicate that particulate lead is the primary contributor to total lead concentration in flowing systems, whereas particulate lead contribution to total lead concentrations for stagnated systems becomes significant only at high water pH values. PMID:21458838

Kim, Eun Jung; Herrera, Jose E; Huggins, Dan; Braam, John; Koshowski, Scott

2011-03-11

376

Factors affecting the biodegradation of phenanthrene initially dissolved in different nonaqueous-phase liquids  

Microsoft Academic Search

A study was conducted of the importance of measured partitioning rate, the nonaqueous-phase liquid (NAPL)-water interfacial area, and the toxicity of NAPLs to the biodegradation of constituents of NAPLs. Bacterial mineralization of phenanthrene was slower if the compound was initially dissolved in phthalate esters than in aliphatic hydrocarbons with several NAPL-water interfacial areas. The differences were not the result of

Maria Jose Carroquino; Martin Alexander

1998-01-01

377

METHOD FOR DISSOLVING LANTHANUM FLUORIDE CARRIER FOR PLUTONIUM  

DOEpatents

A method is described for dissolving lanthanum fluoride precipitates which is applicable to lanthanum fluoride carrier precipitation processes for recovery of plutonium values from aqueous solutions. The lanthanum fluoride precipitate is contacted with an aqueous acidic solution containing dissolved zirconium in the tetravalent oxidation state. The presence of the zirconium increases the lanthanum fluoride dissolved and makes any tetravalent plutonium present more readily oxidizable to the hexavalent state. (AEC)

Koshland, D.E. Jr.; Willard, J.E.

1961-08-01

378

Deformed cross-dissolves for image interpolation in scientific visualization  

Microsoft Academic Search

Deformed cross-dissolves are methods for inconspicuous interpolation between images. Wedescribe algorithms for deformation based on scattered data interpolation methods and animproved cross-dissolve algorithm offering better performance than a normal bidirectionalcross-dissolve. Results for interpolation in the field of medical visualization are presented.1 IntroductionImage interpolation has applications in scientific applications as well as in computer animation.In computer...

Detlef Ruprecht; Fb Informatik Ls

1994-01-01

379

Method for dissolving plutonium oxide with HI and separating plutonium  

DOEpatents

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

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

1979-01-01

380

Exercise and Pulmonary Hypertension (PH)  

MedlinePLUS

... Yoamna and Scott's Wedding Fight for the Cause Online Sometimes it’s PH: An Early Diagnosis Campaign Raise Awareness with Your Social Networks Facebook Fundraising Volunteer Volunteer Form Volunteer Profiles ...

381

Nanostructured conductive polymeric materials  

NASA Astrophysics Data System (ADS)

Conductive polymer composites (CPCs) are a suitable alternative to metals in many applications due to their light-weight, corrosion resistance, low cost, ease of processing and design flexibility. CPCs have been formulated using different types of conductive fillers. In this PhD thesis, the focus is on CPCs for electrostatic discharge (ESD) protection and electromagnetic interference (EMI) attenuation. Despite the versatility of conductive fillers, carbon black (CB) has been the dominant filler to make CPCs for ESD protection applications because CB/polymer composites have a cost advantage over all other CPCs. For EMI shielding, stainless steel fibres and metal coated fibers are the preferred fillers, however CPCs made of those fibers are not the dominant EMI shielding materials. Metal coated and polymer plated polymers are the most widely used EMI shielding options. The limited use of CPCs in the EMI shielding market is because the high filler loading required to formulate a composite with an adequate level of shielding remarkably increases the composite price. In order to increase the competitiveness of CPCs, percolation threshold should be minimized as much as possible and composites with high EMI shielding capabilities at low filler loading should be formulated because all conductive fillers are expensive compared to polymers. In this thesis, two different methodologies to reduce percolation threshold in CPCs have been successfully developed and a CPC with exceptional EMI shielding capability has been formulated using copper nanowires as conductive filler. The first percolation threshold reduction technique is based on the selective localization of CB at the interface of immiscible polymer blend. The technique requires adding a copolymer that prefers the blend's interface and for which CB nanoparticles has the highest affinity. The second method is based on producing a CPC powder and then using this powder as a conductive filler to produce composite by dry mixing with pure polymer powder followed by compression molding. The EMI shielding material was developed using copper nanowires. CuNW/Polystyrene composites exhibit EMI shielding effectiveness exceeding that of metal microfillers and carbon nanotube/polymer composites and approaching that of coating techniques have been formulated by solution processing and dry mixing.

Al-Saleh, Mohammed H.

382

PhEDEx Data Service  

NASA Astrophysics Data System (ADS)

The PhEDEx Data Service provides access to information from the central PhEDEx database, as well as certificate-authenticated managerial operations such as requesting the transfer or deletion of data. The Data Service is integrated with the "SiteDB" service for fine-grained access control, providing a safe and secure environment for operations. A plug-in architecture allows server-side modules to be developed rapidly and easily by anyone familiar with the schema, and can automatically return the data in a variety of formats for use by different client technologies. Using HTTP access via the Data Service instead of direct database connections makes it possible to build monitoring web-pages with complex drill-down operations, suitable for debugging or presentation from many aspects. This will form the basis of the new PhEDEx website in the near future, as well as providing access to PhEDEx information and certificate-authenticated services for other CMS dataflow and workflow management tools such as CRAB, WMCore, DBS and the dashboard. A PhEDEx command-line client tool provides one-stop access to all the functions of the PhEDEx Data Service interactively, for use in simple scripts that do not access the service directly. The client tool provides certificate-authenticated access to managerial functions, so all the functions of the PhEDEx Data Service are available to it. The tool can be expanded by plug-ins which can combine or extend the client-side manipulation of data from the Data Service, providing a powerful environment for manipulating data within PhEDEx.

Egeland, Ricky; Wildish, Tony; Huang, Chih-Hao

2010-04-01

383

Dissolution of phosphate rocks in soils. 2. Effect of pH on the dissolution and plant availability of phosphate rock in soil with pH dependent charge  

Microsoft Academic Search

The effect of soil pH on the dissolution of phosphate rocks (PRs) and the subsequent availability of the dissolved inorganic phosphorus (Pi) to plants was examined in a volcanic soil adjusted to different pH values. Potassium dihydrogen orthophosphate (KH2PO4) and three PRs, Nauru (NPR), Jordan (JPR) and North Carolina (NCPR) were incubated with the pH-amended soils at a rate of

N. S. Bolan; M. J. Hedley

1990-01-01

384

Adsorption and decomposition of water-dissolved ozone on high silica zeolites.  

PubMed

The adsorption properties of water-dissolved ozone on high silica zeolites were investigated. Adsorbed ozone was desorbed almost reversibly. The adsorption equilibrium relations were described by a linear expression written as q=betaC, where q is the amount adsorbed, C is the equilibrium concentration and beta is the equilibrium constant. Also, the beta values were strongly dependent on the SiO(2)/Al(2)O(3) ratio (mol/mol) and on the pore structure of the high silica zeolites. The larger the SiO(2)/Al(2)O(3) ratio, the larger the value of beta. ZSM-5 (SiO(2)/Al(2)O(3) ratio: 3000), which gave the highest adsorption capacity of water-dissolved ozone, was able to highly concentrate water-dissolved ozone on the adsorbent. The decomposition behavior of adsorbed ozone was also investigated. Ozone adsorbed on high silica zeolite was observed to be a little more stable than ozone existing in bulk water. The decomposition rate was independent of SiO(2)/Al(2)O(3) ratios in the range of 30-3000 or a solution pH in the range of 4-6. PMID:14630113

Fujita, Hirotaka; Izumi, Jun; Sagehashi, Masaki; Fujii, Takao; Sakoda, Akiyoshi

2004-01-01

385

Temperature and Hydrological Controls on Dissolved Organic Matter Mobilization and Transport within forest soils  

NASA Astrophysics Data System (ADS)

Natural dissolved organic matter (DOM) influences nutrients cycling and contaminants mobility, provides an energy source for heterotrophic production, and regulates soil and water pH. The objectives of this laboratory study were (i) to investigate the relative influence of temperature and rainfall characteristics on the mobilization and transport of DOM (quantity and composition) in forest soils; (ii) to evaluate the possible difference between dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) dynamics; and (iii) to elucidate the importance of biotic and physico-chemical mechanisms that govern DOM mobilization and transport during rainfall events. We applied intermittent rainfalls to unsaturated topsoil columns. The experimental treatments were distinguished on the basis of rainfall intensity, rainfall frequency, temperature, soil biotic activity (i.e., sterile vs unsterile soil), and soil storage time before rainfall initiation. A mathematical model incorporating reversible linear kinetics expressions for DOC release at soil-water interfaces closely describes the DOC breakthrough-curve data. Our results show that temperature significantly affects the release rate and composition of leached DOM, while changes in rainfall intensity and frequency only affect the quantity of mobilized DOM. Effluent concentrations of DON showed broadly similar temporal patterns with DOC during rainfall events. Differences between the quantity of DOC and DON were reflected in the C:N ratios of effluent DOM. Our results also indicate the relative importance of physico-chemical mechanisms for the DOM export process.

Xu, N.; Saiers, J. E.

2009-12-01

386

Soil redox and pH effects on methane production in a flooded rice soil  

Microsoft Academic Search

Methane formation in soil is a microbiological process controlled by many factors. Of them soil redox potential (Eh) and soil pH are considered as critical controls. A laboratory incubation experiment was conducted to study the critical initiation soil Eh, the optimum soil pH, and the interaction of Eh and pH on methane production. A small decrease in pH resulting from

Z. P. Wang; R. D. DeLaune; P. H. Masscheleyn; W. H. Patrick

1993-01-01

387

Removal of actinides from dissolved ORNL MVST sludge using the TRUEX process  

SciTech Connect

Experiments were conducted to evaluate the transuranium extraction process for partitioning actinides from actual dissolved high-level radioactive waste sludge. All tests were performed at ambient temperature. Time and budget constraints permitted only two experimental campaigns. Samples of sludge from Melton Valley Storage Tank W-25 were rinsed with mild caustic (0.2 M NaOH) to reduce the concentrations of nitrates and fission products associated with the interstitial liquid. In one campaign, the rinsed sludge was dissolved in nitric acid to produce a solution containing total metal concentrations of ca. 1.8 M with a nitric acid concentration of ca. 2.9 M. About 50% of the dry mass of the sludge was dissolved. In the other campaign, the sludge was neutralized with nitric acid to destroy the carbonates, then leached with ca. 2.6 M NaOH for ca. 6 h before rinsing with the mild caustic. The sludge was then dissolved in nitric acid to produce a solution containing total metal concentrations of ca. 0.6 M with a nitric acid concentration of ca. 1.7 M. About 80% of the sludge dissolved. The dissolved sludge solution form the first campaign began gelling immediately, and a visible gel layer was observed after 8 days. In the second campaign, the solution became hazy after ca. 8 days, indicating gel formation, but did not display separated gel layers after aging for 20 days. Batch liquid-liquid equilibrium tests of both the extraction and stripping operations were conducted. Chemical analyses of both phases were used to evaluate the process. Evaluation was based on two metrics: the fraction of TRU elements removed from the dissolved sludge and comparison of the results with predictions made with the Generic TRUEX Model (GTM). The fractions of Eu, Pu, Cm, Th, and U species removed from aqueous solution in only one extraction stage were > 95% and were close to the values predicted by the GTM. Mercury was also found to be strongly extracted, with a one-stage removal of > 92%.

Spencer, B.B.; Egan, B.Z.; Chase, C.W.

1997-07-01

388

pH sensors based on hydrogenated diamond surfaces  

NASA Astrophysics Data System (ADS)

We report on the operation of ungated surface conductive diamond devices in electrolytic solutions. The effect of electrolyte pH on the channel conductivity is studied in detail. It is shown that fully hydrogen terminated diamond surfaces are not pH sensitive. However, a pronounced pH sensitivity arises after a mild surface oxidation by ozone. We propose that charged ions from the electrolyte adsorbed on the oxidized surface regions induce a lateral electrostatic modulation of the conductive hole accumulation layer on the surface. In contrast, charged ions are not expected to be adsorbed on the hydrogen terminated surface, either due to the screening induced by a dense layer of strongly adsorbed counter-ions or by the absence of the proper reactive surface groups. Therefore, the modulation of the surface conductivity is generated by the oxidized regions, which are described as microscopic chemical in-plane gates. The pH sensitivity mechanism proposed here differs qualitatively from the one used to explain the behavior of conventional ion sensitive field effect transistors, resulting in a pH sensitivity higher than the Nernstian limit.

Garrido, Jose A.; Härtl, Andreas; Kuch, Stefan; Stutzmann, Martin; Williams, Oliver A.; Jackmann, R. B.

2005-02-01

389

Design and deployment of a portable membrane equilibrator for sampling aqueous dissolved gases  

NASA Astrophysics Data System (ADS)

We present designs for a portable trace gas sampler, based on membrane technology, to obtain a gas sample from water in the field. A continuous flow of water is equilibrated with a finite volume of gas until the gas pressure matches the total dissolved gas pressure of the water stream. Samples collected in this manner can be analyzed to determine original water concentrations for potentially any dissolved gas. The sampler requires neither compressed carrier gas nor a vacuum pump to extract the dissolved gas sample; its power consumption is minimal and it fits within a 30 L plastic case. During the development stages, both major atmospheric gases (N2, O2, and Ar) and trace gases (CO2, SF6, and SF5CF3) were measured to confirm the equilibrium condition and to quantify the response time. Equilibration studies were conducted in the laboratory and at the site of a borehole CO2 injection experiment on the Lamont campus of Columbia University. The time required to achieve solubility equilibrium depends on the dissolved gas content and the water flow rate; we determined an e-folding response time of 9-12 min, under air-saturated conditions and with a flow rate of 2 L/min. Typically, equilibrium is achieved within 30-45 min. We compare the system function and analytical results to conventional sampling methods during the recovery phase of a push-pull experiment and find a generally good agreement within 10% of conventional analyses for each of the gases.

Loose, B.; Stute, M.; Alexander, P.; Smethie, W. M.

2009-04-01

390

Growth limitation of three Arctic sea ice algal species: effects of salinity, pH, and inorganic carbon availability  

Microsoft Academic Search

The effect of salinity, pH, and dissolved inorganic carbon (TCO2) on growth and survival of three Arctic sea ice algal species, two diatoms (Fragilariopsis nana and Fragilariopsis sp.), and one species of chlorophyte (Chlamydomonas sp.) was assessed in controlled laboratory experiments. Our results suggest that the chlorophyte and the two diatoms have\\u000a different tolerance to fluctuations in salinity and pH.

Dorte Haubjerg SøgaardPer; Per Juel Hansen; Søren Rysgaard; Ronnie Nøhr Glud

2011-01-01

391

Formulation Design and Optimization of Fast Dissolving Clonazepam Tablets  

PubMed Central

Fast dissolving tablets of clonazepam were prepared by direct compression method with a view to enhance patient compliance. A 32 full factorial design was applied to investigate the combined effect of two formulation variables: amount of crospovidone and microcrystalline cellulose. Crospovidone (2-8% w/w) was used as superdisintegrant and microcrystalline cellulose (20-40% w/w) was used as diluent, along with directly compressible mannitol to enhance mouth feel. The tablets were evaluated for hardness, friability, thickness, drug content uniformity, in vitro dispersion time, wetting time and water absorption ratio. Based on in vitro dispersion time (approximately 16 s); the formulation containing 2% w/w crospovidone and 40% w/w microcrystalline cellulose was found to be promising and tested for in vitro drug release pattern (in pH 6.8 phosphate buffer). Short-term stability (at 40°/75% relative humidity for 3 mo) and drug-excipient interaction. Surface response plots are presented to graphically represent the effect of independent variables on the invitro dispersion time. The validity of the generated mathematical model was tested by preparing two extra-design checkpoints. The optimized tablet formulation was compared with conventional commercial tablet formulation for drug release profiles. This formulation showed nearly five-fold faster drug release (t50% 3.5 min) compared to the conventional commercial tablet formulation (t50% 16.4 min). Short-term stability studies on the formulation indicated that there are no significant changes in drug content and in vitro dispersion time (P<0.05).

Shirsand, S. B.; Suresh, Sarasija; Swamy, P. V.

2009-01-01

392

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

USGS Publications Warehouse

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

Ebbert, J. C.

2002-01-01

393

Removal of dissolved heavy metals from acid rock drainage using iron metal  

SciTech Connect

The chemical and microbial activity of corroding iron metal is examined in the acid rock drainage (ARD) resulting from pyrite oxidation to determine the effectiveness in neutralizing the ARD and reducing the load of dissolved heavy metals. ARD from Berkeley Pit, MT, is treated with iron in batch reactors and columns containing iron granules. Iron, in acidic solution, hydrolyzes water producing hydride and hydroxide ion resulting in a concomitant increase in pH and decrease in redox potential. The dissolved metals in ARD are removed by several mechanisms. Copper and cadmium cement onto the surface of the iron as zerovalent metals. Hydroxide forming metals such as aluminum, zinc, and nickel form complexes with iron and other metals precipitating from solution as the pH rises. Metalloids such as arsenic and antimony coprecipitate with iron. As metals precipitate from solution, various other mechanisms including coprecipitation, sorption, and ion exchange also enhance removal of metals from solution. Corroding iron also creates a reducing environment supportive for sulfate reducing bacteria (SRB) growth. Increases in SRB populations of 5,000-fold are observed in iron metal treated ARD solutions. Although the biological process is slow, sulfidogenesis is an additional pathway to further stabilize heavy metal precipitates.

Shokes, T.E.; Moeller, G. [Univ. of Idaho, Moscow, ID (United States)

1999-01-15

394

Calcium and pH in north and central Swedish mire waters  

Microsoft Academic Search

Summary 1 We present data on calcium concentrations and pH in mire waters collected from different mire types in central and northern Sweden, compiled from published literature or calculated from field determinations of electrical conductivity and pH. 2 Measurements of electrical conductivity (after subtracting that of H + ions) were used to calculate the most probable Ca concentrations, but only

H. Sjors; U. Gunnarsson

2002-01-01

395

Supervisor selection or allocation and continuity of supervision: Ph.D. students’ progress and outcomes  

Microsoft Academic Search

This article reports part of an Australian longitudinal study which examined the patterns evident in the relationships Ph.D. students and supervisors developed and the ways they worked together. The participants were 21 Ph.D. students and their main supervisors. Data were collected via interviews conducted between 1995 and 1998. Three interviews were conducted separately for each student and supervisor. This report

Glenice Ives; Glenn Rowleyb

2005-01-01

396

Dissolved aluminium in the Southern Ocean  

NASA Astrophysics Data System (ADS)

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

Middag, R.; van Slooten, C.; de Baar, H. J. W.; Laan, P.

2011-12-01

397

Removal of dissolved Zn(II) using coal mine drainage sludge: implications for acidic wastewater treatment.  

PubMed

The mechanism for the removal of Zn(II) by using coal mine drainage sludge (CMDS) was investigated by spectroscopic analysis and observations of batch tests using model materials. Zeta potential analysis showed that CMDS(25) (dried at 25 °C) and CMDS(550) (dried at 550 °C) had a much lower isoelectric point of pH (pH(IEP)) than either goethite or calcite, which are the main constituents of CMDS. This indicates that the negatively charged anion (sulfate) was incorporated into the structural networks and adsorbed on the surface of CMDS via outer-sphere complexation. The removal of Zn(II) by CMDS was thought to be primarily caused by sulfate-complexed iron (oxy)hydroxide and calcite. In particular, the electrostatic attraction of the negatively charged functional group, FeOH-SO(4)(2-), to the dissolved Zn(II) could provide high removal efficiencies over a wide pH range. Thermodynamic modeling and Fourier transform infrared spectroscopy (FT-IR) demonstrated that ZnSO(4) is the dominant species in the pH range 3-7 as the sulfate complexes with the hydroxyl groups, whereas the precipitation of Zn(II) as ZnCO(3) or Zn(5)(CO(3))(2) (OH)(6) through the dissolution of calcite is the dominant mechanism in the pH range 7-9.6. PMID:23295677

Cui, Mingcan; Jang, Min; Cannon, Fred S; Na, Seunmin; Khim, Jeehyeong; Park, Jae Kwang

2013-01-05

398

Adsorption of dissolved organics in lake water by aluminum oxide. Effect of molecular weight  

USGS Publications Warehouse

Dissolved organic compounds in a Swiss lake were fractionated into three molecular size classes by gel exclusion chromatography, and adsorption of each fraction on colloidal alumina was studied as a function of pH. Organic compounds with molecular weight (Mr) greater than 1000 formed strong complexes with the alumina surface, but low molecular weight compounds were weakly adsorbed. Electrophoretic mobility measurements indicated that alumina particles suspended in the original lake water were highly negatively charged because of adsorbed organic matter. Most of the adsorbed organic compounds were in the Mr range 1000 < Mr < 3000. Adsorption of these compounds during the treatment of drinking water by alum coagulation may be responsible for the preferential removal of trihalomethane precursors. Adsorption may also influence the molecular-weight distribution of dissolved organic material in lakes. surface, the present work will focus on the influence of molecular size and pH on the adsorption behavior of dissolved organic material of a Swiss lake. From a geochemical point of view, it is important to know the molecular-weight distribution of adsorbed organic matter so that we may better assess its reactivity with trace elements. The study also serves as a first step in quantifying the role of adsorption in the geochemical cycle of organic carbon in lacustrine environments. For water-treatment practice, we need to determine whether molecular weight fractionation occurs during adsorption by aluminum oxide. Such a fractionation could be significant in the light of recent reports that chloroform and other organochlorine compounds are preferentially produced by particular molecular-weight fractions (25-27). ?? 1981 American Chemical Society.

Davis, J. A.; Gloor, R.

1981-01-01

399

Iron dynamics during injection of dissolved organic carbon into a sandy aquifer  

SciTech Connect

The dynamics of dissolved, colloidal, and solid-phase iron were examined during a forced-gradient field experiment in Georgetown, South Carolina, in the summer of 1990. The experiment involved injection of 80,000 L of oxygenated water containing high levels of dissolved organic carbon (66 mg/L DOC) into a sandy aquifer. Iron dynamics were followed for 2 weeks in three saturated horizons at sampling wells located 1.5 (A wells) and 3 m (B wells) from the injection well. The initial oxidation/reduction potential of the aquifer favored Fe(II) in the iron-rich groundwater. As oxygen-rich water was introduced into the groundwater, the redox potential was expected to increase. The impacts of the changing redox potential on iron dynamics were hypothesized to be as follows: (1) Fe(II) may decrease and Fe(III) may increase due to oxidation, but otherwise Fe(II) may be mobile and conservative. (2) Fe(III) is mostly in the ferric oxide/hydroxide colloidal fraction, that is, the ferric fraction may be found predominantly in sizes >{sup {approximately}}1 nm(or >3000 mol wt), and the transport of colloidal iron oxide may be limited. (3) Ferric oxide/hydroxide colloids may have positive or near-zero surface charge in the pH range of the groundwater (6.0-7.2). (4) The turbidity of groundwater may increase as a result of the formation of iron colloids. During the course of injection, dissolved oxygen (DO), pH, iron concentration, DOC concentration, and turbidity were measured. Samples were also collected for microelectrophoretic mobility measurement (Coulter model: Delsa 440), particle-size analysis (Coulter model: N4MD, based on photon correlation spectrometry (PCS)) and scanning electron microscopic examination (ISI-40). The results from the two sampling wells are summarized briefly. 4 refs., 3 figs., 1 tab.

Liang, Liyuan; McCarthy, J.F. (Oak Ridge National Lab., TN (USA)); Williams, T.M. (Clemson Univ., Georgetown, SC (USA). Belle W. Baruch Forest Science Inst.)

1991-01-01

400

Duodenal pH in cystic fibrosis and its relationship to fat malabsorption.  

PubMed

To investigate the relationship between duodenal pH levels and supplemental pancreatic enzyme function in cystic fibrosis, 18 children with this condition had pH recordings performed from the second and fourth part of the duodenum. Compared to age-matched controls, patients with cystic fibrosis had significantly longer periods below a pH of 4.0 in the postprandial period and significantly less time above pH 5.8. These values correspond to the pH levels at which lipase is irreversibly destroyed (pH 4.0) and enteric coating of enzyme supplements dissolves (pH 5.8). A significant relationship was found between the pH recordings from the fourth part of the duodenum and the degree of residual fat malabsorption while taking enteric-coated enzyme supplements. Four patients with an excessively acidic duodenum and residual fat malabsorption despite high-dose enzyme supplementation were treated with misoprostol (Searle), a known acid-reducing agent. There were significant improvements in both duodenal pH values and fat absorption. We conclude that there is a wide range of duodenal pH values found in patients with cystic fibrosis and that the efficiency with which enzyme supplements work is closely related to these pH levels. Administration of misoprostol to those patients with excessively acidic duodenal pH levels as well as residual malabsorption appears to be of benefit in improving both the excessively acidic pH levels and the fat malabsorption. PMID:2120019

Robinson, P J; Smith, A L; Sly, P D

1990-10-01

401

Dissolved organic carbon reduces the toxicity of aluminum to three tropical freshwater organisms.  

PubMed

The influence of dissolved organic carbon (DOC) on the toxicity of aluminum (Al) at pH 5 (relevant to acid mine drainage conditions), to the tropical green hydra (Hydra viridissima), green alga (Chlorella sp.), and cladoceran (Moinodaphnia macleayi) was assessed. Two DOC sources, a natural in situ DOC in soft billabong water (SBW) and Suwannee River fulvic acid (SRFA) standard, were compared. The order of sensitivity of the test organisms to dissolved Al (0.1 µm fraction) was Hydra viridissima > Moinodaphnia macleayi > Chlorella sp. with DOC reducing dissolved Al toxicity most for Hydra viridissima. However, colloidal or precipitated Al may contribute indirectly to the toxicity for M. macleayi and Chlorella sp. The toxicity of dissolved Al was up to six times lower in test waters containing 10 mg L(-1) DOC (in the form of SRFA), relative to toxicity observed at 1 mg L(-1) DOC. In contrast, the toxicity of Al was up to two times lower in SBW containing 10 mg L(-1) DOC, relative to water containing 1 mg L(-1) DOC. The increased ability of SRFA in reducing Al toxicity was linked to its greater affinity for complexing Al compared with the in situ DOC. This has important implications for studies that use commercial standards of humic substances to predict Al toxicity in local environments. Speciation modeling demonstrated that Al(3+) and AlOH(2+) provided a strong relationship with toxicity. An empirical relationship is provided for each organism that can be used to predict Al toxicity at a given Al and DOC concentration. PMID:22105345

Trenfield, Melanie A; Markich, Scott J; Ng, Jack C; Noller, Barry; van Dam, Rick A

2012-02-01

402

Formation of haloacetic acids from dissolved organic matter fractions during chloramination.  

PubMed

The objective of this study was to investigate the roles of dissolved organic matter (DOM) fractions, pH and bromide concentration in the formation of haloacetic acids (HAA) during chloramination. DOM from two surface waters with a low (2.9 L/mg-m) and high (5.1 L/mg-m) specific UV absorbance (SUVA(254)) values was isolated and fractionated into three fractions based on the hydrophobicity [i.e., hydrophobic (HPO), transphilic (TPH) and hydrophilic (HPI)]. DOM mass balances and DBP reactivity checks were performed to characterize the effects of isolation and fractionation steps. The fractions were chloraminated at three pHs and three bromide concentrations. The results showed that pH was the most important factor controlling HAA formation and speciation. The HAA yields significantly decreased with increase in pH from 6.3 to 9.0. The impact of bromide in the formation of brominated HAA species also became less important with increasing pH, and no brominated specie was detectable at pH 9. HPO fractions of the two source waters consistently showed higher HAA yields than TPH and HPI fractions. On the other hand, HPI fractions showed higher bromine incorporation than HPO and TPH fractions. To maintain higher and relatively stable combined chlorine residuals while reducing HAA formation, water utilities may consider keeping pH above 7.5 as one strategy. This will also lower the formation of brominated HAA species which have been shown to be more cyto- and geno-toxic than their chlorinated analogs. PMID:23245540

Hong, Ying; Song, Hocheol; Karanfil, Tanju

2012-11-30

403

Dissolved Humic Matter in Arctic Estuaries  

NASA Astrophysics Data System (ADS)

As part of the German-Russian bilateral SIRRO(Siberian River Runoff)-project we studied the distribution of dissolved humic matter isolated by XAD-8 in the estuarine waters of the Ob and Yenisei rivers. The relative contributions of humic matter carbon to total DOC decreased from 61-77 percent in the river freshwater endmember to 35-40 percent in the marine waters of the open Kara Sea at salinities 33 psu. Humic carbon mixed conservatively in the Yenisei and non-conservatively in the Ob, where partial removal was indicated in the low salinity range. Changes in the relative contribution of humic matter to different molecular weight classes of DOM (ultrafiltration cutoffs 150 KDa, 450 KDa, 800 KDa) were studied along the salinity gradient in the Yenisei. High molecular weight DOM is relatively enriched in humics in fresh-water compared to sea-water HMW-DOM. Low molecular weight DOM is realtively enriched in humics in sea-water compared to fresh-water LMW-DOM. Throughout the estuary humic matter is depleted in 13C and nitrogen compared to total DOM, reflecting a dominant soil source. We estimate an annual input of 5 Tg humic matter carbon by the two rivers into the Kara Sea.

Spitzy, A.; Koehler, H.; Ertl, S.

2002-12-01

404

Methanex, Hoechst Celanese dissolve methanol partnership  

SciTech Connect

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

Morris, G.D.L.

1993-03-31

405

Microbial degradation of dissolved proteins in seawater  

SciTech Connect

An experimental protocol using radiolabeled proteins was developed to investigate the rates and mechanisms whereby dissolved proteins are degraded in natural marine plankton communities. The results of field observations and laboratory experiments indicate that proteins are degraded by a particle-bound, thermolabile system, presumably bacteria-associated enzymes, with an apparent half-saturation constant of ca. 25 ..mu..g bovine serum albumin (BSA) per liter. Gel permeation chromatography indicated that peptides of chain length intermediate between BSA and the final products of degradation (MW<700) do not accumulate in the medium. Competition experiments indicate that the system is relatively nonspecific. Turnover rates for the protein pool in samples collected in the Southern California Bight were of the same order of magnitude as the turnover rate of the L-leucine pool and were correlated with primary productivity, chlorophyll a concentrations, bacterial abundance and biomass, and L-leucine turnover rate. These data suggest that amino acids derived from proteins are utilized preferentially and do not completely mix with the amino acids in the bulk phase.

Hollibaugh, J.T.; Azam, F.

1983-11-01

406

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

Microsoft Academic Search

The relationship of some dissolved trace metals (Al, Cr, Mn, Zn, and Pb) with one another and to dissolved phosphate and nitrate in a freshwater aquatic system at Flic en Flac and Grand River North West (GRNW) in Mauritius (1850 km2, 20°S and 57°E, Western Indian ocean) is reported following trace metal determination using inductively coupled plasma mass spectrometry (ICP-MS).

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

2001-01-01

407

Burrowing activity in Mercenaria mercenaria (L.) and Spisula solidissima (Dillwyn) as a function of temperature and dissolved oxygen  

Microsoft Academic Search

Burrowing activity was utilized as a measure of the ability of the hard shell clam (Mercenaria mercenaria) and the Atlantic surf clam (Spisula solidissima) to cope with extremes of temperature and dissolved oxygen. Clams were removed from clean sand substrate and the progress of reburial timed. Experiments were conducted in a once through circulating seawater system in which temperatures were

N. B. Savage

1976-01-01

408

Toxicity of total dissolved solids associated with two mine effluents to chironomid larvae and early life stages of rainbow trout  

Microsoft Academic Search

Assessment of total dissolved solids (TDS) represents an integrated measure of the concentrations of common ions (e.g., sodium, potassium, calcium, magnesium, chloride, sulfate, and bicarbonate) in freshwaters. Toxicity related to these ions is due to the specific combination and concentration of ions and is not predictable from TDS concentrations. Short-term chronic toxicity tests were conducted with larval chironomids and trout

P. M. Chapman; H. Bailey; E. Canaria

2000-01-01

409

Pressure, Temperature, Salinity and Dissolved-Oxygen Profile Data from R/V ATLANTIS II Cruise 107 - Leg X.  

National Technical Information Service (NTIS)

The report summarizes in graphical and tabular form the continuous conductivity-temperature-pressure-dissolved-oxygen (CTDO(sub 2)) data collected during the R/V ATLANTIS II cruise 107, Leg X. The data were collected in the austral winter of 1980 as part ...

D. T. Georgi A. R. Piola N. Galbraith

1981-01-01

410

FOREST SOIL RESPONSE TO ACID AND SALT ADDITIONS OF SULFATE III. SOLUBILIZATION AND COMPOSITION OF DISSOLVED ORGANIC CARBON  

EPA Science Inventory

A year-long experiment, using reconstructed spodosol and intact alfisol soil columns, was conducted to examine the effects of various simulated throughfall solutions on soil C dynamics. oil organic C solubilization, dissolved organic C fractions, and decomposition rates were stud...

411

Dissolved and Particulate Hydrocarbons in the Loire Estuary, from the Riverine Zone to the External Estuary: Budget at Different Seasons  

Microsoft Academic Search

In order to investigate the fate and transport processes of hydrocarbons in estuarine and coastal environments, we have undertaken a study of different hydrocarbon species in both dissolved and particulate forms. This two years study has been conducted in the Loire estuary at different reference stations (riverine, injection of sewage effluents, maximum turbidity zone, open sea) and at different seasons

J. Tronczynski; J. C. Marty; P. Scribe; A. Saliot

1986-01-01

412

Transport of dissolved oxygen through silicone rubber membrane  

Microsoft Academic Search

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

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

1971-01-01

413

Tissue oxygenation with graded dissolved oxygen delivery during cardiopulmonary bypass  

Microsoft Academic Search

Background: Intravascular perfluorochemical emulsions together with a high oxygen tension may increase the delivery of dissolved oxygen to useful levels. The hypothesis of this study is that increasing the dissolved oxygen content of blood with incremental doses of a perfluorochemical emulsion improves tissue oxygenation during cardiopulmonary bypass in a dose-related fashion. Methods and Results: Oxygen utilization was studied in a

William L. Holman; Russell D. Spruell; Edward R. Ferguson; Janice J. Clymer; Walter V. A. Vicente; C. Patrick Murrah; Albert D. Pacifico

1995-01-01

414

What controls dissolved iron concentrations in the world ocean?  

Microsoft Academic Search

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

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

1997-01-01

415

Dissolved humic substances of the Amazon River system1  

Microsoft Academic Search

Aquatic humic and fulvic acids from nine mainstem and seven major tributary sites in the Amazon River Basin are characterized by their elemental and lignin phenol compositions. Com- bined humic substances represent 60% of the riverine dissolved organic carbon (DOC), with fulvic to humic acid (FA : HA) ratios in the mainstem averaging 4.7 -t 1 .O. All dissolved humic

John R. Ertel; John I. Hedges; Allan H. Devol; Jefrey E. Richey

1986-01-01

416

Dissolved Organic Matter Transformations: Implications for Catchment-Scale Processes  

Microsoft Academic Search

Particulate and dissolved phase lignin parameters are used to understand sources and dynamics of terrigenous organic matter (OM) in freshwater and marine systems. Impacts of catchment properties, such as soil type and mineralogy, vegetation distribution and hydrologic conditions on terrestrial dissolved and particulate biomarker compositions have not been addressed. Our experimental approach deciphers relative contributions of these parameters on bulk

A. Robinson; P. Hernes; I. Montanez; B. Eustis

2006-01-01

417

Groundwater flow and dissolved carbon movement in a boreal peatland  

Microsoft Academic Search

Measurement of the groundwater flux and the consequent advection of dissolved carbon (DOC (dissolved organic carbon), CH4 and CO2) were made in a boreal peatland in northern Sweden in summer 1993. The early summer gradients in hydraulic head indicated a downward flux of water in the peatland, but after a persistent mid-summer dry period the gradients changed to produce an

J. M. Waddington; N. T. Roulet

1997-01-01

418

A bulk silicon dissolved wafer process for microelectromechanical devices  

Microsoft Academic Search

A single-sided bulk silicon dissolved wafer process that has been used to fabricate several different micromechanical structures is described. It involves the simultaneous processing of a glass wafer and a silicon wafer, which are eventually bonded together electrostatically. The silicon wafer is then dissolved to leave heavily boron doped devices attached to the glass substrate. Overhanging features can be fabricated

Yogesh B. Gianchandani; Khalil Najafi

1992-01-01

419

Dissolved P in streams in dry years and wet years  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

420

Kinetics of enhanced gold dissolution: activation by dissolved silver  

Microsoft Academic Search

Coupled oxygen reduction and metal oxidation occur during leaching of gold in cyanide solutions. Both processes are altered by specific surface-active constituents in solution. Dissolved cyanide in solution depresses the rate of oxygen reduction while the presence of silver in solution enhances the rate of reduction. Similarly, the oxidation (dissolution) rate of gold is dramatically increased by dissolved silver in

Milton E. Wadsworth; Ximeng Zhu

2003-01-01

421

Abuse Liability of Dissolvable Tobacco Products  

Center for Biologics Evaluation and Research (CBER)

Text Version... critically important to conduct abuse liability assessments of ... in the subjective experiments—the products may reduce ... (2011) tested product liking of ... More results from www.fda.gov/downloads/advisorycommittees/committeesmeetingmaterials

422

Heat conduction in conducting polyaniline nanofibers  

NASA Astrophysics Data System (ADS)

Thermal conductivity and specific heat of conducting polyaniline nanofibers are measured to identify the nature of heat carrying modes combined with their inhomogeneous structure. The low temperature thermal conductivity results reveal crystalline nature while the high temperature data confirm the amorphous nature of the material suggesting heterogeneous model for conducting polyaniline. Extended acoustic phonons dominate the low temperature (<100 K) heat conduction, while localized optical phonons hopping, assisted by the extended acoustic modes, account for the high temperature (>100 K) heat conduction.

Nath, Chandrani; Kumar, A.; Syu, K.-Z.; Kuo, Y.-K.

2013-09-01

423

Diel behavior of rare earth elements in a mountain stream with acidic to neutral pH  

NASA Astrophysics Data System (ADS)

Diel (24-h) changes in concentrations of rare earth elements (REE) were investigated in Fisher Creek, a mountain stream in Montana that receives acid mine drainage in its headwaters. Three simultaneous 24-h samplings were conducted at an upstream station (pH = 3.3), an intermediate station (pH = 5.5), and a downstream station (pH = 6.8). The REE were found to behave conservatively at the two upstream stations. At the downstream station, REE partitioned into suspended particles to a degree that varied with the time of day, and concentrations of dissolved REE were 2.9- to 9.4-fold (190% to 830%) higher in the early morning vs. the late afternoon. The decrease in dissolved REE concentrations during the day coincided with a corresponding increase in the concentration of REE in suspended particles, such that diel changes in the total REE concentrations were relatively minor (27% to 55% increase at night). Across the lanthanide series, the heavy REE partitioned into the suspended solid phase to a greater extent than the light REE. Filtered samples from the downstream station showed a decrease in shale-normalized REE concentration across the lanthanide series, with positive anomalies at La and Gd, and a negative Eu anomaly. As the temperature of the creek increased in the afternoon, the slope of the REE profile steepened and the magnitude of the anomalies increased. The above observations are explained by cyclic adsorption of REE onto suspended particles of hydrous ferric and aluminum oxides (HFO, HAO). Conditional partition coefficients for each REE between the suspended solids and the aqueous phase reached a maximum at 1700 hours and a minimum at 0700 hours. This pattern is attributed to diel variations in stream temperature, possibly reinforced by kinetic factors (i.e., slower rates of reaction at night than during the day). Estimates of the enthalpy of adsorption of each REE onto suspended particles based on the field results averaged +82 kJ/mol and are similar in magnitude to estimates in the literature for adsorption of divalent metal cations onto clays and hydrous metal oxides. The results of this study have important implications to the use of REE as hydrogeochemical tracers in streams.

Gammons, Christopher H.; Wood, Scott A.; Nimick, David A.

2005-08-01

424

Effect of pH alkaline salts of fatty acids on the inhibition of bacteria associated with poultry processing  

Technology Transfer Automated Retrieval System (TEKTRAN)

The agar diffusion assay was used to examine the effect of pH on the ability of alkaline salts of three fatty acids (FA) to inhibit growth of bacteria associated with poultry processing. FA solutions were prepared by dissolving 0.5 M concentrations of caprylic, capric, or lauric acid in separate ali...

425

The interactive effects of low pH, toxic metals, and DOC on a simulated temporary pond community  

Microsoft Academic Search

The effects of pH, potentially toxic metals, and dissolved organic carbon (DOC) on a freshwater, palustrine wetland assemblage (three amphibian species, one mosquito genus, and 18 genera of algae) were examined in 500 liter outdoor mesocosms. The design was fully factorial and exposure levels were set to represent concentrations that occur naturally in temporary ponds in central Pennsylvania, an acid-impacted

M. T. Horne; W. A. Dunson

1995-01-01

426

Safe thickness for D1 dissolver with 1500 GM plutonium  

SciTech Connect

There is some concern that the FB-Line D1 dissolver may have been pressurized above the liquid head pressure by a reaction that occurred in the dissolver. The D1 Pu limit of 8.8 kg is based on a tank with an inner slab thickness of 3.34 inches and a wall thickness of 0.40 inches for a total slab thickness of 4.14 inches. When the incident occurred there was less than 1,500 gm Pu (1,323 gm) in the dissolver. Some calculations were made to determine the safe slab thickness for 1,500 gm Pu in the D1 dissolver. Calculations show that 1,500 gm Pu can be safely contained in a 6 inch thick D1 dissolver provided the cabinet panels are in place.

Reilly, T.A.

1988-01-20

427

Electrically conductive and thermally conductive materials for electronic packaging  

NASA Astrophysics Data System (ADS)

The aim of this dissertation is to develop electrically or thermally conductive materials that are needed for electronic packaging and microelectronic cooling. These materials are in the form of coatings and are made from pastes. The research work encompasses paste formulation, studying the process of converting a paste to a conductive material, relating the processing conditions to the structure and performance, and evaluating performance attributes that are relevant to the application of these conductive materials. The research has resulted in new information that is valuable to the microelectronic industry. Work on electrically conductive materials emphasizes the development of electrical interconnection materials in the form of air-firable glass-free silver-based electrically conductive thick films, which use the Ti-Al alloy as the binder and are in contrast to conventional films that use glass as the binder. The air-firability, as enabled by minor additions of tin and zinc to the paste, is in contrast to previous glass-free films that are not firable. The recommended firing condition is 930°C in air. The organic vehicle in the paste comprises ethyl cellulose, which undergoes thermal decomposition during burnout of the paste. The ethyl cellulose is dissolved in ether, which facilitates the burnout. Excessive ethyl cellulose hinders the burnout. A higher heating rate results in more residue after burnout. The presence of silver particles facilitates drying and burnout. Firing in air gives lower resistivity than firing in oxygen. Firing in argon gives poor films. Compared to conventional films that use glass as the binder, these films, when appropriately fired, exhibit lower electrical resistivity (2.5 x 10-6 O.cm) and higher scratch resistance. Work on thermally conductive materials addresses thermal interface materials, which are materials placed at the interface between a heat sink and a heat source for the purpose of improving the thermal contact. Heat dissipation is the most critical problem in the microelectronic industry. This work emphasizes the development of thermal interface materials in the form of phase change materials, namely paraffin wax, which melts at 48°C. The addition of boron nitride particles to the wax improves the performance, as indicated by the thermal contact conductance between copper surfaces. The melting of the wax improves the conformability of the thermal interface material, thereby enhancing the conductance. Pressure applied in the direction perpendicular to the plane of the interface also enhances the conductance. With 15 wt. % BN and a pressure of 0.3 MPa, a thermal contact conductance comparable to that attained by using solder (applied in the molten state) as the thermal interface material has been attained.

Liu, Zongrong

428

PhET: Masses & Springs  

NSDL National Science Digital Library

This simulation provides a realistic virtual mass-and-spring laboratory. Users can explore spring motion by manipulating stiffness of the spring and mass of the hanging weight. Concepts of Hooke's Law and elastic potential energy are further clarified through charts showing kinetic, potential, and thermal energy for each spring. This item is part of a larger collection of simulations developed by the Physics Education Technology project (PhET). The simulations are animated, interactive, and game-like environments in which students learn through exploration. All of the sims are freely available from the PhET website for incorporation into classes.

2008-07-29

429

Selective Sorption of Dissolved Organic Carbon Compounds by Temperate Soils  

PubMed Central

Background Physico-chemical sorption onto soil minerals is one of the major processes of dissolved organic carbon (OC) stabilization in deeper soils. The interaction of DOC on soil solids is related to the reactivity of soil minerals, the chemistry of sorbate functional groups, and the stability of sorbate to microbial degradation. This study was conducted to examine the sorption of diverse OC compounds (D-glucose, L-alanine, oxalic acid, salicylic acid, and sinapyl alcohol) on temperate climate soil orders (Mollisols, Ultisols and Alfisols). Methodology Equilibrium batch experiments were conducted using 0–100 mg C L?1 at a solid-solution ratio of 1?60 for 48 hrs on natural soils and on soils sterilized by ?-irradiation. The maximum sorption capacity, Qmax and binding coefficient, k were calculated by fitting to the Langmuir model. Results Ultisols appeared to sorb more glucose, alanine, and salicylic acid than did Alfisols or Mollisols and the isotherms followed a non-linear pattern (higher k). Sterile experiments revealed that glucose and alanine were both readily degraded and/or incorporated into microbial biomass because the observed Qmax under sterile conditions decreased by 22–46% for glucose and 17–77% for alanine as compared to non-sterile conditions. Mollisols, in contrast, more readily reacted with oxalic acid (Qmax of 886 mg kg?1) and sinapyl alcohol (Qmax of 2031 mg kg?1), and no degradation was observed. The reactivity of Alfisols to DOC was intermediate to that of Ultisols and Mollisols, and degradation followed similar patterns as for Ultisols. Conclusion This study demonstrated that three common temperate soil orders experienced differential sorption and degradation of simple OC compounds, indicating that sorbate chemistry plays a significant role in the sorptive stabilization of DOC.

Jagadamma, Sindhu; Mayes, Melanie A.; Phillips, Jana R.

2012-01-01

430

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

SciTech Connect

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

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

1999-03-01

431

The pH of Hawaiian precipitation a preliminary report  

NASA Astrophysics Data System (ADS)

Daily or biweekly precipitation samples have been collected at various sites on the island of Hawaii since 1974. The elevations of the sites ranged from sea level to 3400 m. Samples were analyzed on the day of collection for pH and conductivity. Detection of major anions, such as sulfate and nitrate, were made on selected samples during the period. The pH data show a progressive increase of acidity with elevation. The sea level site averaged pH 5.2, in contrast to the sites above 2500 m, which averaged pH 4.3. It is postulated that the increase in acidity at higher levels might be explained by acidic materials, either natural or man-made, being transported over long distances in the mid-troposphere and being scavenged in the rain of the Hawaiian islands.

Miller, John M.; Yoshinaga, Alan M.

1981-07-01

432

Using pH Abnormalities in Diseased Skin to Trigger and Target Topical Therapy  

Microsoft Academic Search

Purpose  The pH discrepancy between healthy and atopic dermatitis skin was identified as a site-specific trigger for delivering hydrocortisone\\u000a from microcapsules.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Using Eudragit L100, a pH-responsive polymer which dissolves at pH 6, hydrocortisone-loaded microparticles were produced by\\u000a oil-in-oil microencapsulation or spray drying. Release and permeation of hydrocortisone from microparticles alone or in gels\\u000a was assessed, and preliminary stability data was determined.

Khalida Rizi; Rebecca J. Green; Michael X. Donaldson; Adrian C. Williams

433

Dissolved organic carbon fluxes under bare soil.  

PubMed

The flux of dissolved organic carbon (DOC) in soil facilitates transport of nutrients and contaminants in soil. There is little information on DOC fluxes and the relationship between DOC concentration and water flux in agricultural soils. The DOC fluxes and concentrations were measured during 2.5 yr using 30 automatic equilibrium tension plate lysimeters (AETPLs) at 0.4 m and 30 AETPLs at 1.20-m depth in a bare luvisol, previously used as an arable soil. Average annual DOC fluxes of the 30 AETPLS were 4.9 g C m(-2) y(-1) at 0.4 m and 2.4 g C m(-2) y(-1) at 1.2 m depth. The average leachate DOC concentrations were 17 mg C L(-1) (0.4 m) and 9 mg C L(-1) (1.2 m). The DOC concentrations were unrelated to soil moisture content or average temperature and rarely dropped below 9 mg C L(-1) (0.4 m) and 5 mg C L(-1) (1.2 m). The variability in cumulative DOC fluxes among the plates was positively related to leachate volume and not to average DOC concentrations at both depths. This suggests that water fluxes are the main determinants of spatial variability in DOC fluxes. However, the largest DOC concentrations were inversely proportional to the mean water velocity between succeeding sampling periods, suggesting that the maximal net DOC mobilization rate in the topsoil is limited. Elevated DOC concentrations, up to 90 mg C L(-1), were only observed at low water velocities, reducing the risks of DOC-facilitated transport of contaminants to groundwater. The study emphasizes that water flux and velocity are important parameters for DOC fluxes and concentrations. PMID:17332264

Mertens, Jan; Vanderborght, Jan; Kasteel, Roy; Pütz, Thomas; Merckx, Roel; Feyen, Jan; Smolders, Erik

2007-03-01

434

Calculating pH from EC and SAR values in salinity models and SAR from soil and bore water pH and EC data  

Microsoft Academic Search

Currently used soil salinity models do not contain a mechanism for including exchangeable sodium effects on soil pH. A method is needed that allows pH calculation from the sodium adsorption ratio (SAR) or exchangeable sodium percentage (ESP) and electrical conductivity (EC) data. This study developed a simple method for calculating saturated soil paste and aqueous solution pH from SAR (or

C. W. Robbins; W. S. Meyer

1990-01-01

435

Functional genomics of pH homeostasis in Corynebacterium glutamicum revealed novel links between pH response, oxidative stress, iron homeostasis and methionine synthesis  

Microsoft Academic Search

BACKGROUND: The maintenance of internal pH in bacterial cells is challenged by natural stress conditions, during host infection or in biotechnological production processes. Comprehensive transcriptomic and proteomic analyses has been conducted in several bacterial model systems, yet questions remain as to the mechanisms of pH homeostasis. RESULTS: Here we present the comprehensive analysis of pH homeostasis in C. glutamicum, a

Martin Follmann; Ines Ochrombel; Reinhard Krämer; Christian Trötschel; Ansgar Poetsch; Christian Rückert; Andrea Hüser; Marcus Persicke; Dominic Seiferling; Jörn Kalinowski; Kay Marin

2009-01-01

436

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

SciTech Connect

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

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

1990-03-01

437

Formation of Pyromorphite in Anglesite-Hydroxyapatite Suspensions Under Varying pH Conditions  

SciTech Connect

Addition of phosphate to lead [Pb(ll)l-cOntarninated soil to immobilize soil Pb by formation of pyromorphite has been proposed as an alternative remediation technique. Lead sulfate (PbS04, anglesite), a Pb-bearing form found in contaminated soils and wastes, was reacted with a synthetic phosphate mineral, hydroxyapa$te [Ca5(PO& OH], under constant pH (PH 2-7) and simulated gastric pH conditions (PH varied from 2 to 7 within 30 rein) to assess the effects of reaction kinetics on the formation rate of chloropyromorphite and the volubility of Pb. Under constant pH condition, complete transformation of anglesite to chloropyromorphite, [Pb5(PO&Cl], was obtained at pH 4 and pH 5. At pH 6 and pH 7, the newly formed chloropyromorphite precipitated on the surface of undissolved apatite, The coverage of the apatite surface may reduce apatite dissolution fate and the transformation rate of Pb from anglesite to"chloropyromorphite. Increasing the P/Pb ratio increased the transformation rate, but anglesite was still present after a' 120-min reaction time. in the dynamic pH system, the added apatite was rapidly dissolved at the initial low pH, and complete transformation of anglesite to chloropyromorphite was obtained within 25 min., The soluble Pb level was controlled by the volubility of chloropyromorphite during the entire reaction process. These results demonstrate the effect of reaction kinetics on the formation rate of chloropyromorphite and the mechanisms controlling the solubilization of Pb in the anglesite-apatite system. Furthermore, they illustrate that a complete transformation of ingested anglesite to chloropyromorphite can be achieved. under gastrointestinal tract pH conditions if sufficient phosphate is provided.

Ryan, J.A.; Zhang, P.

1998-10-14

438

Growth Regulation of Salvinia molesta by pH and Available Water Column Nutrients  

Microsoft Academic Search

Giant salvinia (Salvinia molesta D.S. Mitchell), a native of South America, is an invasive floating aquatic fern. Previous studies have reported that growth of S. molesta is dependent on dissolved nutrients in the water and that the plant achieves maximum biomass in circumneutral to slightly acidic water. We examined giant salvinia growth in a three-by-three factorial experiment, with pH levels

John D. Madsen; Ryan M. Wersal

2008-01-01

439

A Sodium Bicarbonate Dosing Methodology for pH Management in Freshwater-Recirculating Aquaculture Systems  

Microsoft Academic Search

High-density water-recirculating aquaculture systems with hydraulic retention times above about 5 d must be monitored for alkalinity, and in the vast majority of cases, the alkalinity must be adjusted upwards to assure maintenance of desirable pH levels. Sodium bicarbonate is the preferred additive for increasing alkalinity because it is inexpensive,