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1

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

National Technical Information Service (NTIS)

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

J. C. Ebbert

2003-01-01

2

Comparison of temperature, specific conductance, pH, and dissolved oxygen at selected basic fixed sites in south-central Texas, 1996-98  

USGS Publications Warehouse

One component of the surface-water part of the U.S. Geological Survey National Water-Quality Assessment Program is the use of continuous water-quality monitors to help characterize the spatial and temporal distribution of general water quality in relation to hydrologic conditions. During 1996?98, six continuous water-quality monitors in the South-Central Texas study unit collected water temperature, specific conductance, pH, and dissolved oxygen data. The data were compared among the six sites using boxplots of monthly mean values, summary statistics of monthly values, and hydrographs of daily mean values.

Ging, Patricia B.; Otero, Cassi L.

2003-01-01

3

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

USGS Publications Warehouse

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

Ebbert, James C.

2003-01-01

4

DISSOLVED ORGANIC MATTER AND METALS: EFFECTS OF PH ON PARTITIONING  

EPA Science Inventory

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 fractionated into three operationally defined fractions: hydrophilic acids (Hyd), fulvic acids (FA), an...

5

Dissolved Oxygen and pH Microelectrode Measurements at Water-Immersed Metal Surfaces,  

National Technical Information Service (NTIS)

Investigation of microbial corrosion requires incorporation of both electrochemical and microbiological methods. Dissolved oxygen (DO) and pH were measured at metal/artificial seawater interfaces using microelectrodes in biotic and abiotic systems. Measur...

B. Little W. C. Lee W. G. Characklis Z. Lewandowski

1989-01-01

6

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

7

Relative effect of temperature and pH on diel cycling of dissolved trace elements in prickly pear creek, Montana  

USGS Publications Warehouse

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 Creek, Montana. Light and dark chambers containing sediment and a strand of macrophyte were placed in the stream to simulate instream temperature oscillations. Photosynthesis-induced pH changes were allowed to proceed in the light chambers while photosynthesis was prevented in the dark chambers. Water samples were collected periodically for 22 hr in late July 2001 from all chambers and the stream. In the stream, dissolved Zn concentrations increased by 300% from late afternoon to early morning, while dissolved As concentrations exhibited the opposite pattern, increasing 33% between early morning and late afternoon. Zn and As concentrations in the light chambers showed similar, though less pronounced, diel variations. Conversely, Zn and As concentrations in the dark chambers had no obvious diel variation, indicating that light, or light-induced reactions, caused the variation. Temperature oscillations were nearly identical between light and dark chambers, strongly suggesting that temperature was not controlling the diel variations. As expected, pH was negatively correlated (P < 0.01) with dissolved Zn concentrations and positively correlated with dissolved As concentrations in both the light and dark chambers. From these experiments, photosynthesis-induced pH changes were determined to be the major cause of the diel dissolved Zn and As cycles in Prickly Pear Creek. Further research is necessary in other streams to verify that this finding is consistent among streams having large differences in trace-element concentrations and mineralogy of channel substrate. ?? 2004 Kluwer Academic Publishers.

Jones, C. A.; Nimick, D. A.; McCleskey, R. B.

2004-01-01

8

Dual excitation fluorescence-based sensors for pH and dissolved carbon dioxide monitoring  

Microsoft Academic Search

We report on high performance ratiometric fluorescence-based pH and dissolved carbon dioxide (dCO2) sensors for use in bioprocess and environmental monitoring applications, respectively. Novel hybrid sol-gel-based sensor materials have been developed and successfully used as host matrices in pH and dCO2 sensing. These sensors are easy to prepare and miniaturise, low-cost in terms of fabrication, are mass-producible and when the

Dorota Wencel; John P. Moore; Niall Stevenson; Colette McDonagh

2011-01-01

9

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....

10

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

EPA Science Inventory

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

11

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

12

[Effect of pH perturbation on rainwater dissolved organic matter fluorescence characteristics].  

PubMed

The influence of pH variation on the fluorescence characteristics of rainwater dissolved organic matter (DOM) was studied via excitation emission-matrix spectroscopy. A rainwater sample (pH 5.7) collected in Xiamen (China) in the summer of 2009 was adjusted to different pH values ranging from 3.2 to 10.7. Parallel factor analysis (PARAFAC) decomposed the fluorescence matrices into four humic-like components (C1, C3, C4, and C5), one protein-like component (C2) and an unknown component (C6). As pH values of the sample increased from the initial value of 5.7 to 10.7, the fluorescence intensities of C1, C3, and C5 also increased, while those of C4 and C6 decreased gradually, resulting in an increasing contribution of humic-like components to total fluorescence. The opposite trend was observed when pH decreased to more acidic conditions and the unknown component (< 250, 330/386 nm) became dominant. The relative contribution of the protein-like component to the total fluorescence remained more or less constant as pH varied. In addition, the fluorescence index (FI), humification index (HIX) and the index of recent autochthonous contribution (BIX) were also affected by pH perturbation. It is therefore recommended that the pH of rainwater samples should be measured and reported in future studies to effectively evaluate such "pH effects" on rainwater DOM fluorescence characteristics. PMID:22497145

Deng, Xun; Guo, Wei-dong; Zhuo, Jian-fu

2012-01-01

13

Effect of pH on dynamic and equilibrium surface tension of dissolve organic matter  

NASA Astrophysics Data System (ADS)

Dissolved organic matter (DOM) in the terrestrial environment may originate from the decomposition of soil organic matter accumulated from the degradation of vegetative residues, the release of root exudates, the lysis of microorganisms and addition of organic wastes, such as livestock manure, biosolids, and different composted organic residues, or from irrigation with wastewater. The structure of DOM macromolecules is known to vary with the following aqueous solution properties: ionic strength, the nature of the inorganic ions, pH and dissolved organic carbon (DOC) concentration. In aqueous solution, the DOM molecules are amphiphilic, that is, it possesses both hydrophilic and hydrophobic functional groups in the same molecule. This simultaneous presence, gave rise to the conceptual surfactant like model for DOM which has been studies in conjunction with the equilibrium surface tension at the liquid-air interface (STeq, mN/m). Measurements of STeq of DOM solution were reported in a relatively small number of studies for the conditions of the aqueous solution (e.g., temperature, pH, ionic strength, the valence of the metal ions, and DOC concentration). All studies demonstrate the decrease in STeq with increase aqueous concentration of the DOC. The effect of pH, however, exhibit contradictory results. Specifically, for a given DOC concentration, the patterns reported for STeq versus pH were different. With increasing pH values, STeq has been reported to decrease, increase or exhibit a minimum. These contradictory results have been attributed to the different DOC concentration examined in each of the studies. In current study we hypothesized that the inconsistent results of STeq vs. pH may also stem from the adsorption kinetics of the DOM amphiphilic molecules at the liquid air interface, which can be evaluated form dynamic surface tension measurements (STt). The STt is approaching STeq values and commonly exhibiting an exponential decay pattern. If for different pH values STt is not reaching STeq, different apparent STeq vs. pH patterns can be obtain. In this study measurement of STt and STeq as a function of pH will be presented for DOM solutions from different origins. The analysis of the STt curves will be demonstrated based on a short and long term diffusion model.

Arye, Gilboa; Trifonov, Pavel; Ilani, Talli

2014-05-01

14

Effects of pH and dissolved oxygen on Cr(VI) removal in Fe(0)/H2O systems.  

PubMed

The effects of pH and dissolved oxygen (DO) on aqueous Cr(VI) removal by micro-scale zero-valent iron (Fe(0)/H(2)O system) were investigated. Batch experiments were conducted at pH 4.0, 5.0 and 6.0 under oxic and anoxic conditions. Column experiments were performed at pH 5.0 and 7.5 under oxic condition. Spectroscopic analyses were applied to explain the mechanism of Cr(VI) removal using X-ray absorption near-edge structure (XANES), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Results showed that the kinetics of Cr(VI) removal were fastest at pH 5 under both oxic and anoxic conditions. As a rule, Cr(VI) removal were faster under oxic conditions than under anoxic conditions. Column experiments showed that Cr(VI) removal was about 1.7-fold higher at pH 5 than at pH 7.5. XANES (X-ray absorption near edge structures) results showed that Fe(0) reduced Cr(VI) to Cr(III) under both oxic and anoxic conditions. X-ray diffraction patterns of the Cr(VI)-Fe(0) reaction products suggested partial formation of chromite (FeCr(2)O(4)) at pH 5 and 6 under oxic conditions. However, nano-sized clusters of Cr(III)/Fe(III) hydroxide/oxyhydroxide were formed on the surface of Fe(0) under anoxic conditions. These results indicate that the presence of oxygen in solution plays an important role in control of the kinetic of Cr(VI) removal and in development of various Cr(VI) reduction products. PMID:21163574

Yoon, In-Ho; Bang, Sunbaek; Chang, Jin-Soo; Gyu Kim, Min; Kim, Kyoung-Woong

2011-02-15

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

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

17

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

18

Optimisation of the discrete conductivity and dissolved oxygen monitoring using continuous data series obtained with automated measurement stations.  

PubMed

During the last five years, research on the relation between pollution loads and ecological river water quality has been done on the Dender river. In addition to biological sampling of macroinvertebrates and fish, automated measurement stations were used too to investigate the spatio-temporal variability of physical-chemical water pollution. This study on on-line water quality data collection is based on a measurement campaign during March-April 2000 with two automated measurement stations at two different sites: the flow control weirs at Geraardsbergen and Denderleeuw. These measurement stations contain sensors for temperature, turbidity, conductivity, pH, redoxpotential and dissolved oxygen. Short wave radiation as well as rainfall were monitored by means of pyranometers and rain gauges. A refrigerated sampler with 24 bottles allowed to take samples for additional laboratory analyses. In this study, continuous measurements of two physical-chemical parameters, conductivity and dissolved oxygen, were analysed to evaluate the adequacy of the current monitoring frequency in Flanders. Analysis showed that discrete conductivity measurements can be sufficient for trend detection, but the measuring frequency must be highly increased from one measurement per month to at least 8 measurements. Continuous measurements for conductivity are preferred because extreme values are obtained as well. For dissolved oxygen, a single measurement per month in not enough. The percentage of dissolved oxygen showed a strong diurnal variation with maxima in the late afternoon (photosynthesis) and minima at night (respiration). This parameter also differed significantly from day to day. Continuous measurements are therefore necessary for a reliable assessment of the dissolved oxygen budget of surface waters. When using discrete measurements for dissolved oxygen, a set time should be introduced to eliminate diurnal variation. PMID:15954576

D'heygere, T; Goethals, P; van Griensven, A; Vandenberghe, V; Bauwens, W; Vanrolleghem, P; De Pauw, N

2001-01-01

19

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

2013-01-01

20

DISSOLVED ORGANIC MATTER AND METALS: EFFECTS OF PH ON PARTITIONING NATURAL ORGANIC MATTER IN SOILS AND WATER  

EPA Science Inventory

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 fractionated into three operationally defined fractions: hydrophilic acids (Hyd), fulvic acids (FA), an...

21

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

22

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

23

Optical device for parallel online measurement of dissolved oxygen and pH in shake flask cultures.  

PubMed

We describe a new device with parallel optical measurement of dissolved oxygen (DO) and pH in up to nine shake flasks applicable in any conventional shaking incubator. Measurement ranges are 0-500% of air saturation for oxygen and 5.5-8.5 for pH. It was used to characterize growth profiles of different L-lysine producing strains of Corynebacterium glutamicum, of Saccharomyces cerevisiae and of Escherichia coli. Cultures in unbaffled flasks were highly reproducible. Oxygen limitation was indicated online which is particularly important when cultivating fast growing cells as E. coli. C. glutamicum strains showed distinct characteristic patterns of DO and pH indicating biological events. During the cultivation of S. cerevisiae on glucose, fructose and galactose, oxygen uptake rate was determined using the predetermined value of k(L)a. pH measurement was used to determine the minimum buffer requirement for a culture of C. glutamicum. PMID:19701780

Schneider, Konstantin; Schütz, Verena; John, Gernot Thomas; Heinzle, Elmar

2010-06-01

24

The effect of iron content and dissolved O2 on dissolution rates of clinopyroxene at pH 5.8 and 25??C: Preliminary results  

USGS Publications Warehouse

Dissolution experiments using augite (Mg087Ca0.85Fe0.19Na0.09Al 0.03Si2O6) and diopside (Mg0.91Ca0.93Fe0.07Na0.03Al 0.03Si2O6) were conducted in flow-through reactors (5-ml/h flow rate). A pH of 5.8 was maintained by bubbling pure CO2 through a solution of 0.01 M KHCO3 at 25??C. Two experiments were run for each pyroxene type. In one experiment dissolved O2 concentration in reactors was 0.6 (??0.1) ppm and in the second dissolved O2 was 1.5 (??0.1) ppm. After 60 days, augite dissolution rates (based on Si release) were approximately three times greater in the 1.5 ppm dissolved O2 experiments than in the sealed experiments. In contrast, diopside dissolution rates were independent of dissolved O2 concentrations. Preliminary results from the augite experiments suggest that dissolution rate is directly related to oxidation of iron. This effect was not observed in experiments performed on iron-poor diopside. Additionally, dissolution rates of diopside were much slower than those of augite, again suggesting a relationship between Fe content, Fe oxidation and dissolution rates.

Hoch, A. R.; Reddy, M. M.; Drever, J. I.

1996-01-01

25

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

26

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

27

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

28

Comparisons of optical pH and dissolved oxygen sensors with traditional electrochemical probes during mammalian cell culture.  

PubMed

Small-scale upstream bioprocess development often occurs in flasks and multi-well plates. These culturing platforms are often not equipped to accurately monitor and control critical process parameters; thus they may not yield conditions representative of manufacturing. In response, we and others have developed optical sensors that enable small-scale process monitoring. Here we have compared two parameters critical to control in industrial cell culture, pH and dissolved oxygen (DO), measured with our optical sensors versus industrially accepted electrochemical probes. For both optical sensors, agreement with the corresponding electrochemical probe was excellent. The Pearson Correlations between the optical sensors and electrochemical probes were 98.7% and 99.7%, for DO and pH, respectively. Also, we have compared optical pH sensor performance in regular (320 mOsm/kg) and high-osmolality (450 mOsm/kg) cell culture media to simulate the increase in osmolality in pH-controlled cultures. Over a pH range of 6.38-7.98 the average difference in pH readings in the two media was 0.04 pH units. In summary, we have demonstrated that these optical sensors agree well with standard electrochemical probes. The accuracy of the optical probes demonstrates their ability to detect potential parameter drift that could have significant impact on growth, production kinetics, and protein product quality. We have also shown that an increase in osmolality that could result from controlling pH or operating the reactor in fed-batch mode has an insignificant impact on the functionality of the pH patches. PMID:17216654

Hanson, Michael A; Ge, Xudong; Kostov, Yordan; Brorson, Kurt A; Moreira, Antonio R; Rao, Govind

2007-07-01

29

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

30

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

NASA Astrophysics Data System (ADS)

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

Mammitzsch, K.; Jost, G.; Jürgens, K.

2012-12-01

31

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

2012-12-01

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 to low DO. The dominant scale of temporal DO and pH variability occurred on semidiurnal, diurnal and event (days-weeks) time scales. Daily ranges in DO and pH at 7 m water depth (13 mab) could be as large as 220 ?mol kg-1 and 0.36 units, respectively. Sources of pH and DO variation include photosynthesis within the kelp forest ecosystem, which can elevate DO and pH by up to 60 ?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 near-surface waters. High-frequency variation was also reduced at depth. The mean daily range in DO and pH was 39% and 37% less, respectively, at 17 m water depth relative to 7 m. As a consequence, the exposure history of an organism is largely a function of its depth of occurrence within the kelp forest. With knowledge of local alkalinity conditions and high-frequency temperature, salinity, and pH data, we estimated pCO2 and calcium carbonate saturation states with respect to calcite and aragonite (?calc and ?arag) for the La Jolla kelp forest at 7 m and 17 m water depth. pCO2 ranged from 246 to 1016 ?atm, ?calc was always supersaturated, and ?arag was undersaturated at the beginning of March for five days when pH was less than 7.75 and DO was less than 115 ?mol kg-1. 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. Still, future exposure of coastal California populations to even lower 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.

2012-10-01

33

THE RELATIONSHIP OF TOTAL DISSOLVED SOLIDS MEASUREMENTS TO BULK ELECTRICAL CONDUCTIVITY IN AN AQUIFER CONTAMINATED WITH HYDROCARBON  

EPA Science Inventory

A recent conceptual model links high bulk electrical 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 investigated the vertical distributio...

34

Dissolved oxygen and pH profile evolution after cryovial thaw and repeated cell passaging in a T-75 flask.  

PubMed

Routine cell culture is done in small-scale disposable vessels (typically 0.1-100 mL volumes) in academia and industry. Despite their wide use in bioprocess development (i.e., process optimization and process validation), miniature process scouting devices (PSDs) are considered "black boxes" because they are generally not equipped with sensors. In this study, we show that on-line monitoring of dissolved oxygen (DO) and pH in a T-75 flask-based PSD can be achieved during cell passaging and that this information can be linked to different cellular metabolic states. In this case, on-line monitoring of DO and pH show three distinctive metabolic regions in passages 1-18, 19-28, 29-54 and in particular, the shift in the pH curve, the specific oxygen uptake rate (q(O2)), and the lactate production rate to the oxygen consumption rate yield (Y(Lac/ox)) confirm the existence of these distinctive metabolic regions. These findings are particularly useful because they show that sensor equipped PSDs can help to monitor cell culture behavior after thaw, in pre- and seed culture prior to scale-up and in development/optimization studies. Such routine monitoring will help to develop more consistent cell culture techniques. PMID:20047191

Vallejos, Jose R; Brorson, Kurt A; Moreira, Antonio R; Rao, Govind

2010-04-15

35

Effects of pH, Temperature, Dissolved Oxygen, and Flow Rate on Phosphorus Release Processes at the Sediment and Water Interface in Storm Sewer  

PubMed Central

The effects of pH, temperature, dissolved oxygen (DO), and flow rate on the phosphorus (P) release processes at the sediment and water interface in rainwater pipes were investigated. The sampling was conducted in a residential storm sewer of North Li Shi Road in Xi Cheng District of Beijing on August 3, 2011. The release rate of P increased with the increase of pH from 8 to 10. High temperature is favorable for the release of P. The concentration of total phosphorus (TP) in the overlying water increased as the concentration of DO decreased. With the increase of flow rate from 0.7?m?s?1 to 1.1?m?s?1, the concentration of TP in the overlying water increased and then tends to be stable. Among all the factors examined in the present study, the flow rate is the primary influence factor on P release. The cumulative amount of P release increased with the process of pipeline runoff in the rainfall events with high intensities and shorter durations. Feasible measures such as best management practices and low-impact development can be conducted to control the P release on urban sediments by slowing down the flow rate.

Li, Haiyan; Li, Mingyi; Zhang, Xiaoran

2013-01-01

36

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

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

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

39

[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

40

Monitoring pH and electric conductivity in an EBPR sequencing batch reactor.  

PubMed

This paper presents laboratory-scale experimentation carried out to study enhanced biological phosphorus removal. Two anaerobic aerobic (A/O) sequencing batch reactors (SBR) have been operated during more than one year to investigate the information provided by monitoring pH and electric conductivity under stationary and transient conditions. Continuous measurements of these parameters allow detecting the end of anaerobic phosphorus release, of aerobic phosphorus uptake and of initial denitrification, as well as incomplete acetic acid uptake. These results suggest the possibility of using pH and electric conductivity as control parameters to determine the length of both anaerobic and aerobic phases in an A/O SBR. More valuable information provided by monitoring pH and electric conductivity is the relation between the amount of phosphorus released and the conductivity increase observed during the anaerobic stages and which group of bacteria (heterotrophic or polyphosphate accumulating) is carrying out the denitrification process. PMID:15656307

Serralta, J; Borrás, L; Blanco, C; Barat, R; Seco, A

2004-01-01

41

Automated management of nutrient solutions based on target electrical conductivity, ph, and nutrient concentration ratios  

Microsoft Academic Search

An algorithm to automatically formulate the composition and prepare nutrient solutions for soilless cultures based on desired characteristics given as target values is proposed. To formulate the complete ionic composition of a nutrient solution, standard recommendations referring to the following solution characteristics should be available: (i) electrical conductivity (EC), (ii) pH, (iii) concentration ratios of macronutrients (meq basis), and (iv)

Dimitrios Savvas; Konstantinos Adamidis

1999-01-01

42

Effect of water pH and total dissolved solids on the species diversity of pelagic zooplankton in lakes: A statistical analysis  

Microsoft Academic Search

Statistical analysis of the combined influence of lake surface area (S), water pH, and total dissolved solids (TDS) on the formation of zooplankton communities in lakes has been made on the basis\\u000a of available data on the number of species (N\\u000a \\u000a sp\\u000a ) of pelagic zooplankton in 256 lakes of the temperate zone of Europe, Asia, and North America. Graphic

M. B. Ivanova; T. I. Kazantseva

2006-01-01

43

Effect of pH on photo-oxidation of dissolved organic carbon by hydroxyl radicals in a coloured, softwater stream  

Microsoft Academic Search

Previous work has shown that the photo-oxidation rate of dissolved organic carbon (DOC) exposed to solar radiation was significantly enhanced in acidic stream waters and that the average photo-oxidative loss of DOC in the UVA region was more than 60%. This study examined the effect of pH on photobleaching and the photo-oxidative loss of DOC and the degree of photo-oxidative

Lewis A. Molot; Jeff J. Hudson; Peter J. Dillon; Sean A. Miller

2005-01-01

44

Effects of dissolved hydrogen and elastic and plastic deformation on active dissolution of pipeline steel in anaerobic groundwater of near-neutral pH  

Microsoft Academic Search

The mechano-electrochemical effects of deformation and hydrogen on active dissolution of pipeline steel in near-neutral pH groundwater are described. Thermodynamic analysis shows that the free energy increment due to elastic deformation is insufficient to alter active dissolution rate remarkably. The synergistic effect of stress field and dissolved hydrogen on active dissolution (corrosion) is negligible. The effect of plastic deformation on

B. T. Lu; J. L. Luo; P. R. Norton; H. Y. Ma

2009-01-01

45

Electrochemistry of conductive polymers 36. pH dependence of polyaniline conductivities studied by current-sensing atomic force microscopy.  

PubMed

We demonstrate from our current-sensing atomic force microscopic studies that both electrical and topographical properties of electrochemically prepared polyaniline (PAn) films are affected by their preparation conditions. The electrical properties of the fully doped PAn films prepared in 0.30 M nitric acid with its pH and ionic strength adjusted to 0.50 can be described as a conductor with an average conductivity of 49 (+/-13) S/cm with primarily a compact structure resulting from a relatively small growth rate. The doped PAn films prepared at pH 5.0, for example, have compact structures with large grains and lightly doped semiconducting properties with an average conductivity of about 1.54 (+/-0.09) x 10(-4) S/cm. From these data, we conclude that the degree of protonation of the monomers and the main reactions taking place during an early stage of the polymerization reaction are important factors determining the chemical structures as well as their conductivities and morphologies of the PAn films. PMID:16852113

Hong, Sun-Young; Park, Su-Moon

2005-05-19

46

Mathematical simulation of ionic equilibriums of water coolant using electrical conductivity and pH measurements  

NASA Astrophysics Data System (ADS)

A generalized mathematical model for ionic equilibriums of water coolant is proposed. Particular cases of its solution for turbine condensate, demineralized water, feedwater, and boiler water are considered. It is shown that, by using the proposed method, it is possible to indirectly determine the concentrations of standardized ionic impurities from readings of conductivity meters and pH meters, instruments available in a regular chemical monitoring system.

Bushuev, E. N.

2009-07-01

47

CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Influence of pH on Nanofluids' Viscosity and Thermal Conductivity  

Microsoft Academic Search

Aiming at the dispersion stability of nanoparticles regarded as the guide of heat transfer enhancement, we investigate the viscosity and the thermal conductivity of Cu and Al2 O3 nanoparticles in water under different pH values. The results show that there exists an optimal pH value for the lowest viscosity and the highest thermal conductivity, and that at the optimal pH

Xian-Ju Wang; Xin-Fang Li

2009-01-01

48

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

PubMed

Epsilonproteobacteria have been found globally distributed in marine anoxic/sulfidic areas mediating relevant transformations within the sulfur and nitrogen cycles. In the Baltic Sea redox zones, chemoautotrophic epsilonproteobacteria mainly belong to the Sulfurimonas gotlandica GD17 cluster for which recently a representative strain, S. gotlandica GD1(T), could be established as a model organism. In this study, the potential effects of changes in dissolved inorganic carbon (DIC) and pH on S. gotlandica GD1(T) were examined. Bacterial cell abundance within a broad range of DIC concentrations and pH values were monitored and substrate utilization was determined. The results showed that the DIC saturation concentration for achieving maximal cell numbers was already reached at 800 ?mol L(-1), which is well below in situ DIC levels. The pH optimum was between 6.6 and 8.0. Within a pH range of 6.6-7.1 there was no significant difference in substrate utilization; however, at lower pH values maximum cell abundance decreased sharply and cell-specific substrate consumption increased. PMID:24376054

Mammitzsch, Kerstin; Jost, Günter; Jürgens, Klaus

2014-02-01

49

Changes in pH, dissolved organic matter and Cd species in the rhizosphere soils of Cd phytostabilizer Athyrium wardii (Hook.) Makino involved in Cd tolerance and accumulation.  

PubMed

Phytostabilization has great practical significance and flexibility in the ecological restoration of mining tailings and remediation of heavy metals polluted soils. However, potential use of metallophytes in phytostabilization is limited by a lack of knowledge of many basic plant processes. A mining ecotype (ME) Athyrium wardii, Pb/Cd phytostabilizer, and a non-mining ecotype (NME) A. wardii were grown in a pot experiment to investigate the chemical characteristics of the rhizosphere when exposed to the Cd polluted soils. Rhizobags were used to collect rhizosphere and bulk soils, separately. The results indicated that the ME A. wardii was more efficient in Cd accumulation in the root than NME after growing in Cd polluted soils for 50 days in a green house. Soil solution pH and dissolved organic carbon (DOC) concentration in the rhizosphere of ME A. wardii were higher than in the bulk soil and initial values (before planting), whereas the increment in the ME A. wardii were greater than NME. Owing to the increasing of rhizosphere soil pH, exchangeable Cd significantly decreased, whereas the other Cd species were increased with increasing soil DOC values. It is assumed that the ME A. wardii was effective in stabilizing Cd from the mobile fraction to non-mobile fractions. Results from this study suggest that rhizosphere alkalinization and the exudation of high amounts of dissolved organic matter (DOM) to reduce heavy metal mobility might be the two important mechanisms involved in the metal tolerance/accumulation of ME A. wardii. PMID:24338108

Zhang, Shujin; Li, Tingxuan; Zhang, Xizhou; Yu, Haiying; Zheng, Zicheng; Wang, Yongdong; Hao, Xiaoqing; Pu, Yong

2014-03-01

50

Measurement of pH and dissolved oxygen within cell culture media using a hydrogel microarray sensor  

Microsoft Academic Search

The sensing of analytes in cell culture media without the introduction of exogenous reagents proves difficult in today's cell culturing systems. In this paper, a completely embeddable microarray sensor that has been developed along with a compact fluorescent imaging system to sense oxygen and pH non-invasively is described. The compact detection system consists of an ultra-bright blue diode source, coupling

Seungjoon Lee; Bennett L. Ibey; Gerard L. Coté; Michael V. Pishko

2008-01-01

51

Low pH, dissolved oxygen and high temperature induces Thelohanellus rohita (myxozoan) infestation in tropical fish, Labeo rohita (Hamilton).  

PubMed

In Labeo rohita, myxozoan infection is very common and here occurrence and distribution of myxozoan gill parasites were studied with an objective to evaluate the relationship between myxozoan infections with different abiotic factors. All ponds were infected with myxozoan infection. Sampling of water and fish was done fortnightly and soil sample on monthly basis for about 6 months. L. rohita is infected with the one myxozoan species Thelohanellus rohita. The first, second and third gill arches showed higher distribution of myxozoans than the fourth one. Posterior hemibranch of second gill arch was the most preferred site for parasite attachment. The mean intensity of parasite was significantly higher (p < 0.05) in the size class of 8-9 cm in comparison to the other size classes. There were profound variability in the prevalence, abundance and mean intensity of gill myxosoporeans from three ponds. During the start of the sampling, myxozoans were present in all the ponds but their intensity varied in different ponds. These may be due to the variability in the abiotic factors of individual ponds. Most importantly acidic pH, lower DO and higher temperature promote myxozoan infestation and their propagation. Low soil pH is also seen to enhance their propagation. Our data clearly highlighted that prevalence, intensity and abundance of T. rohita strongly influenced by the above environmental parameters and suggested that its life cycle is probably effected by their change; our hypothesis must be regarded as speculative as long as further detail study is not carried out. PMID:24431581

Saha, Himadri; Saha, Ratan K; Kamilya, Dibyendu; Kumar, Pankaj

2013-10-01

52

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

53

A comprehensive protocol for conducting the Syrian hamster embryo cell transformation assay at pH 6.70  

Microsoft Academic Search

Studies from our laboratory have demonstrated several advantages of conducting the Syrian hamster embryo (SHE) cell transformation assay at pH 6.70 compared to that done historically at higher pH values (7.10–7.35). These include reduction of the influence of SHE cell isolates and fetal bovine serum lot variability on the assay, an increase in the frequency of chemically induced morphological transformation

G. A. Kerckaert; R. J. Isfort; G. J. Carr; M. J. Aardema; R. A. LeBoeuf

1996-01-01

54

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

PubMed

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

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

2014-08-01

55

Effects of dissolved organic matter and pH on heavy metal uptake by sludge particulates exemplified by copper(II) and nickel(II): Three-variable model  

SciTech Connect

Dissolved organic matter (DOM) and pH are important factors affecting heavy metal uptake by sludge particulates. Copper(II) and Nickel(II) uptake behavior by primary and secondary sludge particulates was studied under various pH and DOM conditions. A three-variable model, incorporating effects of pH and DOM, was developed to describe heavy metal uptake. Results show that heavy metal uptake by sludge particulates can be better described by the three-variable model than by the modified Langmuir model in a wide pH range.

Wang, J.; Huang, C.P.; Allen, H.E.; Poesponegoro, I.; Poesponegoro, H.; Takiyama, L.R.

1999-03-01

56

The voltage-activated hydrogen ion conductance in rat alveolar epithelial cells is determined by the pH gradient  

PubMed Central

Voltage-activated H+ currents were studied in rat alveolar epithelial cells using tight-seal whole-cell voltage clamp recording and highly buffered, EGTA-containing solutions. Under these conditions, the tail current reversal potential, Vrev, was close to the Nernst potential, EH, varying 52 mV/U pH over four delta pH units (delta pH = pHo - pHi). This result indicates that H+ channels are extremely selective, PH/PTMA > 10(7), and that both internal and external pH, pHi, and pHo, were well controlled. The H+ current amplitude was practically constant at any fixed delta pH, in spite of up to 100-fold symmetrical changes in H+ concentration. Thus, the rate-limiting step in H+ permeation is pH independent, must be localized to the channel (entry, permeation, or exit), and is not bulk diffusion limitation. The instantaneous current- voltage relationship exhibited distinct outward rectification at symmetrical pH, suggesting asymmetry in the permeation pathway. Sigmoid activation kinetics and biexponential decay of tail currents near threshold potentials indicate that H+ channels pass through at least two closed states before opening. The steady state H+ conductance, gH, as well as activation and deactivation kinetic parameters were all shifted along the voltage axis by approximately 40 mV/U pH by changes in pHi or pHo, with the exception of the fast component of tail currents which was shifted less if at all. The threshold potential at which H+ currents were detectably activated can be described empirically as approximately 20-40(pHo-pHi) mV. If internal and external protons regulate the voltage dependence of gH gating at separate sites, then they must be equally effective. A simpler interpretation is that gating is controlled by the pH gradient, delta pH. We propose a simple general model to account for the observed delta pH dependence. Protonation at an externally accessible site stabilizes the closed channel conformation. Deprotonation of this site permits a conformational change resulting in the appearance of a protonation site, possibly the same one, which is accessible via the internal solution. Protonation of the internal site stabilizes the open conformation of the channel. In summary, within the physiological range of pH, the voltage dependence of H+ channel gating depends on delta pH and not on the absolute pH.

1995-01-01

57

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

58

Assessing constructed wetland functional success using diel changes in dissolved oxygen, pH, and temperature in submerged, emergent, and open-water habitats in the Beaver Creek Wetlands Complex, Kentucky (USA)  

Microsoft Academic Search

We assessed the functional success of restored wetlands by determining if the patterns in dissolved oxygen (DO), temperature, and pH were similar to those conditions observed in natural wetlands. The Beaver Creek Wetlands Complex consists of dozens of marshes and ponds built in a former Licking River floodplain, in the hills of east Kentucky, USA. In natural wetland ecosystems, aquatic

Brian C. Reeder

2011-01-01

59

Systems Characterization of Temperature, Ph and Electrical Conductivity in Aerobic Biodegradation of Wheat Biomass at Differing Mixing Rates  

NASA Technical Reports Server (NTRS)

The purpose of this preliminary study is to observe and relate the rate of mixing to pH and electrical conductivity in an aerobic, continuously stirred bioreactor. The objective is to use data collected from successive experiments as a means of a system characterization. Tests were conducted to obtain these data using a continuously stirred 20 L Cytostir glass reaction vessel as a bioreactor operated without built-in temperature or pH control. The tests were conducted on the lab bench at ambient temperatures. The substrate in the bioreactor was ground wheat biomass obtained from the Biomass Production Chamber at NASA Kennedy Space Center. In this study, the data reflect characteristics of the native (uninoculated) systems as well as inoculated systems. In the native systems, it was found that pi levels became stable after approximately 2 to 3 days. The electrical conductivity levels for the native systems tended to decrease over time. In contrast, ion activity was increased after the introduction of bacteria into the system. This could be correlated with the release of nutrients, due to the activity of the bacteria. Also, there were slight increases in pH in the inoculated system, a result which is expected for a system with no active pr controls. The data will be used to test a mathematical model in an automated system.

Calhoun, M.; Trotman, A.; Aglan, H.

1998-01-01

60

Sorption-desorption and transport of trimethoprim and sulfonamide antibiotics in agricultural soil: effect of soil type, dissolved organic matter, and pH.  

PubMed

Use of animal manure is a main source of veterinary pharmaceuticals (VPs) in soil and groundwater through a series of migration processes. The sorption-desorption and transport of four commonly used VPs including trimethoprim (TMP), sulfapyridine, sulfameter, and sulfadimethoxine were investigated in three soil layers taken from an agricultural field in Chongming Island China and two types of aqueous solution (0.01 M CaCl2 solution and wastewater treatment plant effluent). Results from sorption-desorption experiments showed that the sorption behavior of selected VPs conformed to the Freundlich isotherm equation. TMP exhibited higher distribution coefficients (K d?=?6.73-9.21) than other sulfonamides (K d?=?0.03-0.47), indicating a much stronger adsorption capacity of TMP. The percentage of desorption for TMP in a range of 8-12 % is not so high to be considered significant. Low pH (dissolved organic matter might affect their sorption behavior. Column studies indicated that the transport of VPs in the soil column was mainly influenced by sorption capacity. The weakly adsorbed sulfonamides had a high recovery rate (63.6-98.0 %) in the leachate, while the recovery rate of TMP was only 4.2-10.4 %. The sulfonamides and TMP exhibited stronger retaining capacity in 20-80 cm and 0-20 cm soil samples, respectively. The transport of VPs was slightly higher in the columns leached by WWTP effluent than by CaCl2 solution (0.01 M) due to their sorption interactions. PMID:24443047

Zhang, Ya-Lei; Lin, Shuang-Shuang; Dai, Chao-Meng; Shi, Lu; Zhou, Xue-Fei

2014-05-01

61

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

62

Variation in hydraulic conductivity with decreasing pH in a biologically-clogged porous medium (Invited)  

NASA Astrophysics Data System (ADS)

Microbial biomass can clog porous media and ultimately affect both structural and mineral trapping of CO2 in geological carbon storage reservoirs. Whether biomass can remain intact following a sudden decrease in groundwater pH, a geochemical change associated with CO2 injection, is unclear. We examined this question using twelve biologically-active and three control column-reactor experiments. Cell abundance and distribution was monitored using confocal microscopy, plating, and direct counting. Hydraulic conductivity (K) was monitored using pressure sensors. Growth occurred for four days at neutral pH. During that time, K within the clogged portion of the reactors decreased from 0.013 to 0.0006 cm s-1 on average, a 1.47 log reduction. Next, the pH of the inflowing aqueous medium was lowered to pH 4 in six experiments and pH 5.7 in six experiments. As a result, K increased in five of the pH 4 experiments and two of the pH 5.7 experiments. Despite this increase, however, the columns remained largely clogged. Compared to pre-inoculation K values, log reductions averaged 1.13 and 1.44 in pH 4 and pH 5.7 experiments, respectively. Our findings show that biomass can largely remain intact following acidification and continue to reduce K, even when considerable cell stress and death occurs. This material is based upon work supported as part of the Center for Frontiers of Subsurface Energy Security, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001114. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Altman, S. J.; Kirk, M. F.; Santillan, E. U.; McGrath, L. K.

2013-12-01

63

Summary statistics and graphical comparisons of specific conductance, temperature, and dissolved oxygen data, Buffalo Bayou, Houston, Texas, April 1986-March 1991  

USGS Publications Warehouse

Buffalo Bayou is the major stream that drains the Houston, Texas, metropolitan area. The U.S. Geological Survey has provided specific conductance, temperature, and dissolved oxygen data to the City of Houston for three sites along a 7.7-mile reach of Buffalo Bayou since 1986. Summary statistics and graphical comparisons of the data show substantial variability in the properties during 1986-91. Specific conductance ranged from about 100 microsiemens per centimeter at 25 degrees Celsius at each of the three sites to 17,100 microsiemens per centimeter at 25 degrees Celsius at the most downstream site, at the headwaters of the Houston Ship Channel. Water temperatures ranged from 5 to 33 degrees Celsius. Temperatures were very similar at the two upstream sites and slightly warmer at the most downstream site. Dissolved oxygen ranged from zero at the most downstream site to 11.7 milligrams per liter at the most upstream site.

Brown, D. W.; Paul, E. M.

1995-01-01

64

Quantifying the impact of daily and seasonal variation in sap pH on xylem dissolved inorganic carbon estimates in plum trees.  

PubMed

In studies on internal CO2 transport, average xylem sap pH (pHx ) is one of the factors used for calculation of the concentration of dissolved inorganic carbon in the xylem sap ([CO2 *]). Lack of detailed pHx measurements at high temporal resolution could be a potential source of error when evaluating [CO2 *] dynamics. In this experiment, we performed continuous measurements of CO2 concentration ([CO2 ]) and stem temperature (Tstem ), complemented with pHx measurements at 30-min intervals during the day at various stages of the growing season (Day of the Year (DOY): 86 (late winter), 128 (mid-spring) and 155 (early summer)) on a plum tree (Prunus domestica L. cv. Reine Claude d'Oullins). We used the recorded pHx to calculate [CO2 *] based on Tstem and the corresponding measured [CO2 ]. No statistically significant difference was found between mean [CO2 *] calculated with instantaneous pHx and daily average pHx . However, using an average pHx value from a different part of the growing season than the measurements of [CO2 ] and Tstem to estimate [CO2 *] led to a statistically significant error. The error varied between 3.25 ± 0.01% under-estimation and 3.97 ± 0.01% over-estimation, relative to the true [CO2 *] data. Measured pHx did not show a significant daily variation, unlike [CO2 ], which increased during the day and declined at night. As the growing season progressed, daily average [CO2 ] (3.4%, 5.3%, 7.4%) increased and average pHx (5.43, 5.29, 5.20) decreased. Increase in [CO2 ] will increase its solubility in xylem sap according to Henry's law, and the dissociation of [CO2 *] will negatively affect pHx . Our results are the first quantifying the error in [CO2 *] due to the interaction between [CO2 ] and pHx on a seasonal time scale. We found significant changes in pHx across the growing season, but overall the effect on the calculation of [CO2 *] remained within an error range of 4%. However, it is possible that the error could be more substantial for other tree species, particularly if pHx is in the more sensitive range (pHx > 6.5). PMID:23627372

Erda, F G; Bloemen, J; Steppe, K

2013-04-29

65

Electrochemical sensor for neurotransmitters at physiological pH using a heterocyclic conducting polymer modified electrode.  

PubMed

We report the simultaneous determination of two neurotransmitters, norepinephrine (NEP) and serotonin (5-HT), at physiological pH using the electropolymerized film of 3-amino-5-mercapto-1,2,4-triazole modified glassy carbon (p-AMTa) electrode. A bare glassy carbon (GC) electrode fails to resolve the voltammetric signals of NEP and 5-HT due to the surface fouling caused by the oxidized products of them. However, the p-AMTa electrode not only separates the voltammetric signals of NEP and 5-HT with a potential difference of 150 mV between NEP and 5-HT but also shows higher oxidation currents for them. The simultaneous determination of NEP and 5-HT was successfully achieved at p-AMTa electrode using differential pulse voltammetry method. The amperometric current response increased linearly with increasing NEP and 5-HT concentration in the range of 1.0 × 10(-8) to 1.0 × 10(-4) M and 1.0 × 10(-8) to 5.0 × 10(-5) M, respectively, and the detection limit was found to be 1.65 × 10(-11) for NEP and 1.32 × 10(-11) M for 5-HT (S/N = 3). The p-AMTa electrode shows better recovery results for spiked NEP and 5-HT in human blood plasma samples. PMID:22048066

Revin, S Brillians; John, S Abraham

2012-01-01

66

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

67

Rapid solidification of high-conductivity copper alloys. Ph.D. Thesis  

NASA Technical Reports Server (NTRS)

The main objective was to develop improved copper alloys of high strength and high thermal and electric conductivity. Chill block melt spinning was used to produce binary alloys of Cu-Cr and Cu-Zr, and ternary alloys of Cu-Cr-Ag. By quenching from the liquid state, up to 5 atomic percent of Cr and Zr were retained in metastable extended solid solution during the rapid solidification process. Eutectic solidification was avoided and the full strengthening benefits of the large volume fraction of precipitates were realized by subsequent aging treatment. The very low solid solubility of Cr and Zr in Cu result in a high conductivity Cu matrix strengthened by second phase precipitates. Tensile properties on as-cast and aged ribbons were measured at room and elevated temperatures. Precipitate coarsening of Cr in Cu was studied by changes in electrical resistance during aging. X-ray diffraction was used to measure the lattice parameter and the degree of supersaturation of the matrix. The microstructures were characterized by optical and electron microscopy.

Bloom, Theodore Atlas

1989-01-01

68

New Secondary Batteries Utilizing Electronically Conductive Polypyrrole Cathode. Ph.D. Thesis  

NASA Technical Reports Server (NTRS)

To gain a better understanding of the dynamic behavior in electronically conducting polypyrroles and to provide guidance toward designs of new secondary batteries based on these polymers, two mathematical models are developed; one for the potentiostatically controlled switching behavior of polypyrrole film, and one for the galvanostatically controlled charge/discharge behavior of lithium/polypyrrole secondary battery cell. The first model is used to predict the profiles of electrolyte concentrations, charge states, and electrochemical potentials within the thin polypyrrole film during switching process as functions of applied potential and position. Thus, the detailed mechanisms of charge transport and electrochemical reaction can be understood. Sensitivity analysis is performed for independent parameters, describing the physical and electrochemical characteristic of polypyrrole film, to verify their influences on the model performance. The values of independent parameters are estimated by comparing model predictions with experimental data obtained from identical conditions. The second model is used to predict the profiles of electrolyte concentrations, charge state, and electrochemical potentials within the battery system during charge and discharge processes as functions of time and position. Energy and power densities are estimated from model predictions and compared with existing battery systems. The independent design criteria on the charge and discharge performance of the cell are provided by studying the effects of design parameters.

Yeu, Taewhan

1991-01-01

69

Removal of dissolved aluminum (released by acid rain) using decaying leaves. I. Effects of pH and species of leaves  

SciTech Connect

Aluminum ion appears to be toxic to fish particularly at low pH levels. It is important, therefore, to try to remove aluminum ion from water. The short and long term effects of leaves on reducing aluminum concentration in water have been examined. The overall effect of pH on this process has also been studied. Five common species of leaves have been used and their capacities for removing aluminum from solution have been studied. Results showed that leaves absorbed aluminum in widely varying degrees, depending on the type of leaf and the pH of the solution.

Salim, R.; Robinson, J.W.

1985-01-01

70

Long-term trends in pH, aluminium and dissolved organic carbon in Scottish fresh waters; implications for brown trout ( Salmo trutta) survival  

Microsoft Academic Search

Over the past 30 years upland streams and lochs in Scotland have shown significant signs of recovery from acidification, particularly in terms of declining concentrations of non-marine sulphate (nm-SO4). Long-term index sites in central and southwest Scotland reveal a significant decline in the concentration of biologically important components, notably acidity (H+) and labile (toxic) forms of aluminium (Al-L), whilst dissolved

A. G. McCartney; R. Harriman; A. W. Watt; D. W. Moore; E. M. Taylor; P. Collen; E. J. Keay

2003-01-01

71

An evaluation of in-situ measurements of water temperature, specific conductance, and pH in low ionic strength streams  

USGS Publications Warehouse

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 indicate that the mini-monitor measurements of specific conductance and pH in an acidic stream (acid-neutralizing capacity always less than 0) agreed with laboratory measurements well enough that the minimonitors can be used to supplement laboratory measurements (mean difference in pH was 0.02 pH unit and mean difference in specific conductance was 0.72 ??S cm-1. This mean difference was 0.32 ??S cm-1 if the minimonitor data were adjusted by the bias). In less acidic streams (two streams in which the acid-neutralizing capacity was always greater than 0 and one in which the acid-neutralizing capacity was greater than 0 except during high flows), there was poor agreement between laboratory and minimonitor measurements of specific conductance at high flows and pH at all flows. The water-temperature probes measured with sufficiently small bias (-0.1 ??C) and adequate precision (??0.70 ??C) for use with most applications.

Ranalli, A. J.

1998-01-01

72

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...

73

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

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

74

Air Breathing and Gill Ventilation Frequencies in Juvenile Tarpon, Megalops atlanticus: Responses to Changes in Dissolved Oxygen, Temperature, Hydrogen Sulfide, and PH  

Microsoft Academic Search

This study quantified the air-breathing frequency (ABf in breaths h-1) and gill ventilation frequency (Vf in ventilations min-1) of tarpon Megalops atlanticusas a function of PO2, temperature, pH, and sulphide concentration. Ten tarpon held at normoxia at 22–33°C without access to atmospheric oxygen survived for eight days, and seven survived for 14 days (at which point the experiment was terminated)

Stephen P. Geiger; Joseph J. Torres; Roy E. Crabtree

2000-01-01

75

A monitor for continuous measurement of temperature, pH, and conductance of wet precipitation: Preliminary results from the Adirondack Mountains, New York  

USGS Publications Warehouse

This report describes a continuous wet-only precipitation monitor designed by the U.S. Geological Survey to record variations in rainfall temperature, pH, and specific conductance at 1-min intervals over the course of storms. Initial sampling in the Adirondack Mountains showed that rainfall acidity varied over the course of summer storms, with low initial pH values increasing as storm intensity increased.This report describes a continuous wet-only precipitation monitor designed by the U.S. Geological Survey to record variations in rainfall temperature, pH, and specific conductance at 1-min intervals over the course of storms. Initial sampling in the Adirondack Mountains showed that rainfall acidity varied over the course of summer storms, with low initial pH values increasing as storm intensity increased.

Johnsson, P. A.; Reddy, M. M.

1990-01-01

76

Sol-gel synthesis of ZnO transparent conductive films: The role of pH  

NASA Astrophysics Data System (ADS)

The sol-gel synthesis of undoped and B- or Al-doped ZnO thin films were critically examined with particular reference to the influence of the pH of the reaction medium on some of their specific characteristics, such as thickness, morphology, doping level and optical properties, in view of their application in the photovoltaic field. Using triethanolamine (TEA) as chelating agent, a range of basic pH from 7.66 to 8.76 was explored starting from a very concentrated zinc acetate dehydrate (ZAD) solution in ethanol, [Zn2+] = 1.0 M, and keeping the ZAD/TEA = 1. A more basic environment gives more porous films whose thickness and crystallinity are higher than those achieved at lower pH. It was found that the morphology, as well as the sheet resistance (Rs) of films, depends on both pH and doping. Increasing the pH the Rs decreases for both undoped and doped films. At a certain pH undoped films exhibit a granular microstructure and lower Rs than B- or Al-doped films which exhibit a finer texture, characterized by a lower porosity. Optical properties strongly depend on the pH as well. Increasing the pH, a noticeable blue shift effect was observed, that was attributed mainly to structural changes and to a lesser extent to the Burnstein-Moss effect.

Addonizio, Maria Luisa; Aronne, Antonio; Daliento, Santolo; Tari, Orlando; Fanelli, Esther; Pernice, Pasquale

2014-06-01

77

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

78

Influence of olive oil solid waste applications on soil pH, electrical conductivity, soil nitrogen transformations, carbon content and aggregate stability  

Microsoft Academic Search

Some of the agricultural wastes have important economic potentials to be used as a plant nutrition and\\/or soil conditioner. Olive oil solid waste (OSW) is one of them. The aim of this study was to determine effects of OSW on soil pH, electrical conductivity (EC), improving soil nitrogen (N) status, soil aggregate stability and soil carbon contents. Different rates of

Yasemin Kavdir; Dilek Killi

2008-01-01

79

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

80

Revisiting the Role of Cystic Fibrosis Transmembrane Conductance Regulator and Counterion Permeability in the pH Regulation of Endocytic Organelles  

PubMed Central

Organellar acidification by the electrogenic vacuolar proton-ATPase is coupled to anion uptake and cation efflux to preserve electroneutrality. The defective organellar pH regulation, caused by impaired counterion conductance of the mutant cystic fibrosis transmembrane conductance regulator (CFTR), remains highly controversial in epithelia and macrophages. Restricting the pH-sensitive probe to CFTR-containing vesicles, the counterion and proton permeability, and the luminal pH of endosomes were measured in various cells, including genetically matched CF and non-CF human respiratory epithelia, as well as cftr+/+ and cftr?/? mouse alveolar macrophages. Passive proton and relative counterion permeabilities, determinants of endosomal, lysosomal, and phagosomal pH-regulation, were probed with FITC-conjugated transferrin, dextran, and Pseudomonas aeruginosa, respectively. Although CFTR function could be documented in recycling endosomes and immature phagosomes, neither channel activation nor inhibition influenced the pH in any of these organelles. CFTR heterologous overexpression also failed to alter endocytic organellar pH. We propose that the relatively large CFTR-independent counterion and small passive proton permeability ensure efficient shunting of the proton-ATPase–generated membrane potential. These results have implications in the regulation of organelle acidification in general and demonstrate that perturbations of the endolysosomal organelles pH homeostasis cannot be linked to the etiology of the CF lung disease.

Barriere, Herve; Bagdany, Miklos; Bossard, Florian; Okiyoneda, Tsukasa; Wojewodka, Gabriella; Gruenert, Dieter; Radzioch, Danuta

2009-01-01

81

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

82

Seasonal variations of dissolved and particulate copper species in estuarine waters  

Microsoft Academic Search

This one-year survey conducted in the macrotidal estuary of Penzé (Brittany, Western part of the Channel, France) was aimed at examining the variations of the various dissolved and particulate copper species. Ten field stations along the whole freshwater–seawater mixing zone were sampled each month. Different biogeochemical parameters (SPM, chl-a, pH and DOC) were also measured. The levels in total dissolved

Matthieu Waeles; Ricardo D. Riso; Pierre Le Corre

2005-01-01

83

Test and Evaluation of the Interocean System, Inc. Model 500 CTD/O(2) pH In-situ Monitor System.  

National Technical Information Service (NTIS)

Test and evaluation results are reported for a system which is designed to measure temperature, conductivity, depth, dissolved oxygen, and pH to depths of 100 meters. The system is described and manufacturer's specifications are listed along with represen...

B. S. Pijanowski

1976-01-01

84

Significant different conductivities of the two grades of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), Clevios P and Clevios PH1000, arising from different molecular weights.  

PubMed

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is promising to be the next-generation transparent electrode of optoelectronic devices. This paper reports the differences between two commercially available grades of PEDOT:PSS: Clevios P and Clevios PH1000. The as-prepared PEDOT:PSS films from Clevios P and Clevios PH1000 solutions have close conductivities of 0.2-0.35 S cm(-1). Their conductivities can be enhanced to 171 and 1164 S cm(-1), respectively, through a treatment with hydrofluoroacetone trihydrate (HFA). The differences between Clevios P and Clevios PH1000 were studied by various characterizations on PEDOT:PSS aqueous solutions and PEDOT:PSS films. The gel particles are larger in Clevios PH1000 solution than in Clevios P solution as revealed by dynamic light scattering and fluorescence spectroscopy of pyrene in these solutions. These results suggest that PEDOT of Clevios PH1000 has a higher average molecular weight than that of Clevios P. The difference in the molecular weight of PEDOT for the two grades of PEDOT:PSS is confirmed by the characterizations on their polymer films, including atomic force microscopy and temperature dependences of the resistances of as-prepared and HFA-treated PEDOT:PSS films. The different molecular weights of PEDOT also gives rise to significant differences in the electrochemical behaviors of the two grades of PEDOT:PSS, as revealed by the cyclic voltammetry, in situ UV-vis-NIR absorption spectroscopy and potentiostatic transient measurements. PMID:22768998

Xia, Yijie; Ouyang, Jianyong

2012-08-01

85

High-speed ion-exclusion chromatography of dissolved carbon dioxide on a small weakly acidic cation-exchange resin column with ion-exchange enhancement columns of conductivity detection.  

PubMed

The high-speed ion-exclusion chromatographic determination of dissolved carbon dioxide, i.e., carbonic acid, hydrogencarbonate or carbonate, with conductivity detection was obtained using a small column packed with a weakly acidic cation-exchange resin in the H+-form (40 mm long x 4.6 mm i.d., 3 microm-particle and 0.1 meq./ml-capacity). Two different ion-exchange resin columns, which were a strongly acidic cation-exchange resin in the K+-form and a strongly basic anion-exchange resin in the OH- -form, were connected after the separation column. The sequence of columns could convert dissolved carbon dioxide to KOH having high conductivity response. The enhancement effect for dissolved carbon dioxide could retain even on the vast chromatographic runs, by using the enhancement columns with high ion-exchange capacity above 1.0 meq./ml. The retention time was in 60 s at flow-rate of 1.2 ml/min. The calibration graph of dissolved carbon dioxide estimated as H2CO3- was linear in the range of 0.005-10 mM. The detection limit at signal to noise of 3 was 0.15 microM as H2CO3-. This method was applicable to several rainwater and tap water samples. PMID:16199234

Mori, Masanobu; Ikedo, Mikaru; Hu, Wenzhi; Helaleh, Murad I H; Xu, Qun; Itabashi, Hideyuki; Tanaka, Kazuhiko

2005-10-28

86

The electrical conductivity of the Earth's upper mantle as estimated from satellite measured magnetic field variations. Ph.D. Thesis  

NASA Technical Reports Server (NTRS)

Low latitude magnetic field variations (magnetic storms) caused by large fluctuations in the equatorial ring current were derived from magnetic field magnitude data obtained by OGO 2, 4, and 6 satellites over an almost 5 year period. Analysis procedures consisted of (1) separating the disturbance field into internal and external parts relative to the surface of the Earth; (2) estimating the response function which related to the internally generated magnetic field variations to the external variations due to the ring current; and (3) interpreting the estimated response function using theoretical response functions for known conductivity profiles. Special consideration is given to possible ocean effects. A temperature profile is proposed using conductivity temperature data for single crystal olivine. The resulting temperature profile is reasonable for depths below 150-200 km, but is too high for shallower depths. Apparently, conductivity is not controlled solely by olivine at shallow depths.

Didwall, E. M.

1981-01-01

87

Influence of olive oil solid waste applications on soil pH, electrical conductivity, soil nitrogen transformations, carbon content and aggregate stability.  

PubMed

Some of the agricultural wastes have important economic potentials to be used as a plant nutrition and/or soil conditioner. Olive oil solid waste (OSW) is one of them. The aim of this study was to determine effects of OSW on soil pH, electrical conductivity (EC), improving soil nitrogen (N) status, soil aggregate stability and soil carbon contents. Different rates of OSW (control, 2%, 4% and 8%, w/w) were applied to coarse soils and incubated for 2 months. OSW applications decreased soil pH values. The mean EC value of soil measured 2 months after the incubation was greater than that of the first month. Application of OSW at the rate of 8% has significantly increased soil total organic nitrogen contents. OSW applications at the rate of 8% (w/w) significantly increased both mean SOC content (3.5%) and aggregate stability (88%) after 2 months of incubation (p<0.01). Therefore, OSW has great potential to improve soil structure of coarse textured soil in short term. PMID:17627818

Kavdir, Yasemin; Killi, Dilek

2008-05-01

88

DISSOLVED OXYGEN PROFILES AND WATER QUALITY ANALYSIS IN THE MILNER RESERVOIR NEAR BURLEY IDAHO, IDAHO, OCTOBER 1975  

EPA Science Inventory

On August 29, 1975, Parametrix, Inc. conducted a water sampling program in the Milner Reservoir. This program was designed to determine the effects of the Ore-Ida and Simplot Companies discharges upon the dissolved oxygen, pH, alkalinity, and BOD of the receiving waters. 7 samp...

89

Investigation of a fiber optic surface plasmon spectroscopy in conjunction with conductivity as an in situ method for simultaneously monitoring changes in dissolved organic carbon and salinity in coastal waters.  

PubMed

A combination surface plasmon resonance (SPR) and conductivity sensor array was developed and implemented to demonstrate the ability to differentiate among changes in dissolved organic carbon (DOC) and salinity in coastal water. The array is capable of achieving sufficient spatial and temporal data density to better understand the cycling and fate of terrestrial DOC in coastal areas. DOC is the second largest source of bioreactive carbon in the environment and plays a key role in mediating microbial activity and generation of atmospheric CO(2). In the coastal areas, the salinity is also an important property in many applications, such as leak detection for landfill liners, saltwater intrusion to drinking water, marine environment monitoring, and seasonal climate prediction. Conductivity sensors are the industry standard for determining salinity in ocean systems. However, both conductivity and refractive index sensors, such as SPR spectroscopy based sensors, respond to salinity and DOC levels. To demonstrate the capability of the SPR sensor and a conductivity sensor to collect complimentary data useful in discrimination of salinity and DOC in coastal zone water, conductivity, SPR, and temperature data were collected during passage from the Juan de Fuca ridge area returning to the University of Washington docks. PMID:21881638

Kim, Yoon-Chang; Cramer, Jeffrey A; Booksh, Karl S

2011-10-21

90

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

91

Electrical Conductivity Protocol  

NSDL National Science Digital Library

The purpose of this resource is to measure the conductivity of water at a freshwater hydrology site. Students calibrate and take electrical conductivity measurements using an electrical conductivity meter. Students estimate the total dissolved solids from the electrical conductivity measurements.

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

2003-08-01

92

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

93

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

94

Photobleaching of humic rich dissolved organic matter  

Microsoft Academic Search

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

Thomas Brinkmann; Daniel Sartorius; Fritz H. Frimmel

2003-01-01

95

DISSOLVED OXYGEN DIURNAL FLUX STUDY  

EPA Science Inventory

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

96

Seasonal variations of dissolved and particulate copper species in estuarine waters  

Microsoft Academic Search

This one-year survey conducted in the macrotidal estuary of Penzé (Brittany, Western part of the Channel, France) was aimed at examining the variations of the various dissolved and particulate copper species. Ten field stations along the whole freshwater seawater mixing zone were sampled each month. Different biogeochemical parameters (SPM, chl-a, pH and DOC) were also measured. The levels in total

M. Waeles; R. D. Riso; P. Le Corre

2005-01-01

97

Quality-assurance results for field pH and specific-conductance measurements, and for laboratory analysis, National Atmospheric Deposition Program and National Trends Network; January 1980-September 1984  

USGS Publications Warehouse

Five intersite comparison studies for the field determination of pH and specific conductance, using simulated-precipitation samples, were conducted by the U.S.G.S. for the National Atmospheric Deposition Program and National Trends Network. These comparisons were performed to estimate the precision of pH and specific conductance determinations made by sampling-site operators. Simulated-precipitation samples were prepared from nitric acid and deionized water. The estimated standard deviation for site-operator determination of pH was 0.25 for pH values ranging from 3.79 to 4.64; the estimated standard deviation for specific conductance was 4.6 microsiemens/cm at 25 C for specific-conductance values ranging from 10.4 to 59.0 microsiemens/cm at 25 C. Performance-audit samples with known analyte concentrations were prepared by the U.S.G.S.and distributed to the National Atmospheric Deposition Program 's Central Analytical Laboratory. The differences between the National Atmospheric Deposition Program and national Trends Network-reported analyte concentrations and known analyte concentrations were calculated, and the bias and precision were determined. For 1983, concentrations of calcium, magnesium, sodium, and chloride were biased at the 99% confidence limit; concentrations of potassium and sulfate were unbiased at the 99% confidence limit. Four analytical laboratories routinely analyzing precipitation were evaluated in their analysis of identical natural- and simulated precipitation samples. Analyte bias for each laboratory was examined using analysis of variance coupled with Duncan 's multiple-range test on data produced by these laboratories, from the analysis of identical simulated-precipitation samples. Analyte precision for each laboratory has been estimated by calculating a pooled variance for each analyte. Interlaboratory comparability results may be used to normalize natural-precipitation chemistry data obtained from two or more of these laboratories. (Author 's abstract)

Schroder, L. J.; Brooks, M. H.; Malo, B. A.; Willoughby, T. C.

1986-01-01

98

Kinetics of Kaolinite Precipitation and Dissolution under Circumneutral pH Conditions  

NASA Astrophysics Data System (ADS)

The precipitation of clay minerals exerts an important control on pore water chemistry in a variety of subsurface environments, and may even control the extent of undersaturation with respect to primary dissolving phases like feldspar (Maher et al., 2005). It is essential, therefore, to quantify clay precipitation kinetics, particularly under the circumneutral pH conditions typically found in subsurface environments. We have conducted kinetic studies of Georgia KGA-1b kaolinite dissolution and precipitation rates at 25C and input pH values of 4 in continuously stirred flowthrough reactors as a function of the extent of undersaturation or supersaturation, dissolved silica and aluminum concentration, and pH. Preliminary results suggest a promotion of dissolution rates by dissolved silica. For example, dissolution rates determined close to equilibrium (log Q/Keq ~ -0.5), but with high input silica concentrations (~ 300 micromolar), are more rapid than rates determined far from equilibrium with no dissolved silica in the input solution. Dissolution rates at pH 4 and 25C are broadly comparable to rates determined by Nagy et al. (1991). The dissolution experiments also provide a direct measure of the solubility of the KGA-1b kaolinite, an essential prerequisite to precipitation experiments intended to quantify rates as a function of supersaturation. Scanning transmission X-ray microscopy (STXM) and XPS analyses at the Advanced Light Source are being used to characterize reaction products.

Yang, L.; Steefel, C. I.; Larsen, J. T.

2005-12-01

99

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

100

A methodology for quantifying time variations of the turbidity/electrical conductivity relationship during complex floods: application to the delineation of particle and dissolved materials transfer at a karst spring  

NASA Astrophysics Data System (ADS)

In Upper Normandy, where drinking water supply comes from karst aquifers, rainfall events may involve turbid runoffs. These events induce sanitary crises and shutdowns of the water supply. The springs of Fontaine-Sous-Préaux provide 60% of Rouen's population (400,000) (France). These springs are highly vulnerable and their exploitation is confronted with the recurrence of turbid events, which can reach up to 150 NTU during highly rain events. The turbidity observed at karst springs is a complex signal composed by two parts of different origins: a first part coming from the direct transfer of particles from the surface following runoff events, and a second part involving the resuspension of materials previously deposited within karst conduits. The disctinction between those two part has always been very challenging. In this study, taking the example of a karst spring in Upper Normandy (Fontaine Sous Préaux spring), we attempted to refine a turbidigraph decomposition method based on the comparison between electrical conductivity (EC) and turbidity (T) using separated modelled hysteresis curves. In a first step, the EC and T breakthrough curves are modelled using an appropriate number of sub-peaks. Second, local EC-T hysteresis curves are builded up in order to characterize the time-varying changes of the dissolved/particulate transports relationships and to assess the respective contribution of the direct transfer and resuspended parts of turbidity throughout complex floods. Associated to cross-correlation analyses of the EC and T sub-peaks separated, the method allowed identification of the (potentially changing) lag time between EC and T. The results obtained highlighted the pre-eminence of resuspension phenomena at the spring for all floods studied. Nevertheless, four different types of hysteresis curves could be distinguished: i) wide clockwise hysteresis expressing the pre-eminence of resuspension accompanied by pressure pulse transfer phenomena; ii) wide clockwise hysteresis expressing the pre-eminence of resuspension of sediments arriving simultaneously with surface waters; iii) a thin hystérésis equivalent to an almost linear relationship between EC and T, corresponding to a simultaneous transfer of surface water and particles, iv) a thin and curved counter-clockwise hysteresis representing a direct transfer of particles and water from the surface characterizing a deficit of available sedimentary stock. Keywords : transport processes, hysteresis, resuspension, direct transfer, deposition.

Mouhri, A.; Motelay, A.; Hanin, G.; Massei, N.; Fournier, M.; Dupont, J. P.; Laignel, B.

2009-04-01

101

Monitoring pH and ORP in a SHARON reactor.  

PubMed

This paper analyses the valuable information provided by the on-line measurements of pH and oxidation reduction potential (ORP) in a continuous single high ammonia removal over nitrite (SHARON) reactor. A laboratory-scale SHARON reactor equipped with pH, ORP, electric conductivity and dissolved oxygen (DO) probes has been operated for more than one year. Nitrogen removal over nitrite has been achieved by adding methanol at the beginning of anoxic stages. Time evolution of pH and ORP along each cycle allows identifying the decrease in nitritation rate when ammonia is consumed during the aerobic phase and the end of the denitrification process during the anoxic phase. Therefore, monitoring pH and ORP can be used to develop a real-time control system aimed at optimizing the length of both aerobic and anoxic stages. Real-time control of methanol addition can be carried out by using the information provided by these probes: excessive methanol addition in the anoxic stage is clearly detected in the ORP profile of the following aerobic phase, while a deficit of methanol is detected in both pH and ORP profiles of that anoxic phase. Moreover, other valuable information such as the amount of ammonia nitrified, failures in DO measurements, excessive stirring during the anoxic stage and methanol dosage in the aerobic phase was also provided by the pH and ORP profiles. PMID:22049741

Claros, J; Serralta, J; Seco, A; Ferrer, J; Aguado, D

2011-01-01

102

Measuring Total Dissolved Gas Pressure at a Petroleum Plume Site  

NASA Astrophysics Data System (ADS)

Groundwater contamination from petroleum hydrocarbons is ubiquitous across the country, in both urban and rural settings. Natural attenuation of petroleum contaminants may result in the production of gases (e.g. methane, carbon dioxide), in dissolved and potentially gas-phase form, which may affect the extent, persistence and remediation of petroleum hydrocarbon groundwater plumes. Current monitoring practices for gases in groundwater generally involve collecting water samples from wells or gas from gas-water separators during pumping tests, and subsequent analysis in the laboratory. Another potential option is the use of total dissolved gas pressure (TDGP) sensors, which can provide valuable real-time information on dissolved gas conditions while minimizing analytical costs. However, these have not been adequately tested or optimized for use in monitoring petroleum-contaminated groundwater. Preliminary testing of TDGP sensor measurement was performed on a selection of existing wells at a site in Ontario with previously-monitored groundwater contamination by petroleum hydrocarbons. TDGP was measured using a PT4 Tracker (Point Four Systems Inc., B.C.). Other properties such as dissolved oxygen and pH were also measured, and samples were collected and analyzed for major ions, metals, and various petroleum hydrocarbons. Results showed that 3 of the wells had contaminants, as well as elevated methane and dissolved iron. They also had lower nitrate and sulphate concentrations, but so did one uncontaminated well. The TDGP for these wells was elevated compared to background groundwater and compared to that expected for equilibration with the atmosphere. These higher values likely result from the microbial generation of dissolved methane. This data set suggests that natural biodegradation processes are occurring in the petroleum plume. However, some other wells also had elevated TDGP. They could indicate a septic plume, but the relatively low electrical conductivity (EC) is not supportive of this. It was also noted that for some wells, but not all, TDGP increased substantially following pumping, which may indicate that degassed stagnant water in the well needs to be replaced by fresher groundwater prior to TDGP measurement. These preliminary findings suggest that TDGP has the potential to provide real-time insight into where gas-producing reactions (in this case, likely methanogenesis) may be occurring in groundwater, which may be useful in assessing or monitoring natural attenuation of petroleum hydrocarbons. However, there are complicating factors that require further investigation.

Roy, J. W.; Spoelstra, J.; van Stempvoort, D.

2009-05-01

103

Pill Dissolving Demo  

NSDL National Science Digital Library

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

Vu Bioengineering Ret Program

104

A finite element model of conduction, convection, and phase change near a solid/melt interface. Ph.D. Thesis - Michigan Univ.  

NASA Technical Reports Server (NTRS)

Detailed understanding of heat transfer and fluid flow is required for many aerospace thermal systems. These systems often include phase change and operate over a range of accelerations or effective gravitational fields. An approach to analyzing such systems is presented which requires the simultaneous solution of the conservation laws of energy, momentum, and mass, as well as an equation of state. The variable property form of the governing equations are developed in two-dimensional Cartesian coordinates for a Newtonian fluid. A numerical procedure for solving the governing equations is presented and implemented in a computer program. The Galerkin form of the finite element method is used to solve the spatial variation of the field variables, along with the implicit Crank-Nicolson time marching algorithm. Quadratic Langrangian elements are used for the internal energy and the two components of velocity. Linear Lagrangian elements are used for the pressure. The location of the solid/liquid interface as well as the temperatures are determined form the calculated internal energy and pressure. This approach is quite general in that it can describe heat transfer without phase change, phase change with a sharp interface, and phase change without an interface. Analytical results from this model are compared to those of other researchers studying transient conduction, convection, and phase change and are found to be in good agreement. The numerical procedure presented requires significant computer resources, but this is not unusual when compared to similar studies by other researchers. Several methods are suggested to reduce the computational times.

Viterna, Larry A.

1991-01-01

105

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

106

Precipitation strengthened high strength, high conductivity Cu-Cr-Nb alloys produced by chill block melt spinning. Final Report Ph.D. Thesis  

NASA Technical Reports Server (NTRS)

A series of Cu-based alloys containing 2 to 10 a/o Cr and 1 to 5 a/o Nb were produced by chill block melt spinning (CBMS). The melt spun ribbons were consolidated and hot rolled to sheet to produce a supersaturated Cu-Cr-Nb solid solution from which the high melting point intermetallic compound Cr2Nb could be precipitated to strengthen the Cu matrix. The results show that the materials possess electrical conductivities in excess of 90 percent that of pure Cu at 200 C and above. The strengths of the Cu-Cr-Nb alloys were much greater than Cu, Cu-0.6 Cr, NARloy-A, and NARloy-Z in the as-melt spun condition. The strengths of the consolidated materials were less than Cu-Cr and Cu-Cr-Zr below 500 C and 600 C respectively, but were significantly better above these temperatures. The strengths of the consolidated materials were greater than NARloy-Z, at all temperatures. The GLIDCOP possessed similar strength levels up to 750 C when the strength of the Cu-Cr-Nb alloys begins to degrade. The long term stability of the Cu-Cr-Nb alloys was measured by the microhardness of aged samples and the growth of precipitates. The microhardness measurements indicate that the alloys overage rapidly, but do not suffer much loss in strength between 10 and 100 hours which confirms the results of the electrical resistivity measurements taken during the aging of the alloys at 500 C. The loss in strength from peak strength levels is significant, but the strength remains exceptionally good. Transmission electron microscopy (TEM) of the as-melt spun samples revealed that Cr2Nb precipitates formed in the liquid Cu during the chill block melt spinning, indicating a very strong driving force for the formation of the precipitates. The TEM of the aged and consolidated materials indicates that the precipitates coarsen considerably, but remain in the submicron range.

Ellis, David L.; Michal, Gary M.

1989-01-01

107

Precipitation strengthened high strength, high conductivity Cu-Cr-Nb alloys produced by chill block melt spinning. Final report Ph. D. Thesis  

SciTech Connect

A series of Cu-based alloys containing 2 to 10 a/o Cr and 1 to 5 a/o Nb were produced by chill block melt spinning (CBMS). The melt spun ribbons were consolidated and hot rolled to sheet to produce a supersaturated Cu-Cr-Nb solid solution from which the high melting point intermetallic compound Cr2Nb could be precipitated to strengthen the Cu matrix. The results show that the materials possess electrical conductivities in excess of 90 percent that of pure Cu at 200 C and above. The strengths of the Cu-Cr-Nb alloys were much greater than Cu, Cu-0.6 Cr, NARloy-A, and NARloy-Z in the as-melt spun condition. The strengths of the consolidated materials were less than Cu-Cr and Cu-Cr-Zr below 500 C and 600 C respectively, but were significantly better above these temperatures. The strengths of the consolidated materials were greater than NARloy-Z, at all temperatures. The GLIDCOP possessed similar strength levels up to 750 C when the strength of the Cu-Cr-Nb alloys begins to degrade. The long term stability of the Cu-Cr-Nb alloys was measured by the microhardness of aged samples and the growth of precipitates. The microhardness measurements indicate that the alloys overage rapidly, but do not suffer much loss in strength between 10 and 100 hours which confirms the results of the electrical resistivity measurements taken during the aging of the alloys at 500 C. The loss in strength from peak strength levels is significant, but the strength remains exceptionally good. Transmission electron microscopy (TEM) of the as-melt spun samples revealed that Cr2Nb precipitates formed in the liquid Cu during the chill block melt spinning, indicating a very strong driving force for the formation of the precipitates. The TEM of the aged and consolidated materials indicates that the precipitates coarsen considerably, but remain in the submicron range.

Ellis, D.L.; Michal, G.M.

1989-09-01

108

Electrically Conductive Polymer Compositions.  

National Technical Information Service (NTIS)

A conductive polymer composite system is made by dissolving an electron donating polymer and a simple or complex N-methylphenazinium TCNQ salt in a mutual solvent and casting a film of the resulting solution on a suitable substrate.

O. K. Kim

1983-01-01

109

Voltammetric determination of dissolved iron and its speciation in freshwater  

Microsoft Academic Search

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

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

2004-01-01

110

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

111

Effect of Dissolved Organic Matter on Basalt Weathering Rates under Flow Conditions  

NASA Astrophysics Data System (ADS)

Rock weathering is an important aspect of soil formation that is tightly coupled to the progressive colonization of grain surfaces by microorganisms and plant tissue, both of which are associated with the exudation of complexing ligands and reducing equivalents that are incorporated into dissolved organic matter. As part of a larger hillslope experimental study being designed for Biosphere 2 (Oracle, AZ), we seek to determine how the presence and concentration of dissolved organic matter affects the incongruent dissolution rates of basaltic tuff. Saturated flow column experiments are being conducted using plant-derived soluble organic matter solutions of variable concentrations, and comparisons are being made to experiments conducted with malic acid, a low-molecular weight organic acid commonly exuded into the rhizosphere. Dissolved organic matter was extracted from Ponderosa Pine forest floor and was characterized for aqueous geochemical parameters (pH, EC, ion balance, DOC/TN) and also for DOC composition (UV-Vis, FTIR spectroscopy). Column effluents are being analyzed for major and trace cations, anions, silica and organic solutes. Dissolution rates of primary minerals and precipitation rates of secondary phases will be estimated by fitting the data to a numerical reactive transport model, CrunchFlow2007. At the end of the fluid flow experiment, column materials will be analyzed for biogeochemical composition to detect preferential dissolution of specific phases, the precipitation of new ones, and to monitor the associated formation of biofilms. The influence of organic solutions on weathering patterns of basalt will be discussed.

Dontsova, K.; Steefel, C. I.; Chorover, J. D.

2009-12-01

112

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

113

A Dissolving Challenge  

NSDL National Science Digital Library

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

Kessler, James; Galvan, Patti

2010-01-01

114

Seasonal variations of dissolved and particulate copper species in estuarine waters  

NASA Astrophysics Data System (ADS)

This one-year survey conducted in the macrotidal estuary of Penzé (Brittany, Western part of the Channel, France) was aimed at examining the variations of the various dissolved and particulate copper species. Ten field stations along the whole freshwater-seawater mixing zone were sampled each month. Different biogeochemical parameters (SPM, chl- a, pH and DOC) were also measured. The levels in total dissolved and total particulate copper ranged from 1.8 to 9.5 nM and from 5 to 98 ?g g -1, respectively; such amounts are indicative of a pollution-free system. Extractable C 18 copper (non-polar hydrophobic organic copper species), in winter and spring, accounted for 30-40% of the total dissolved copper. In summer, this contribution rapidly rose to 60% in the salinity range 20-30; over the same period of time, total particulate copper decreased. The change in dissolved copper speciation and the lowering of particulate copper concentrations were attributed to the release of strong organic ligands by phytoplankton. Our field data evidenced a highly variable behaviour for the various copper species over the seasonal cycle, and then led us to identify the following mechanisms: (i) metal desorption from organic river-flown particles (winter and spring), (ii) metal desorption from resuspended sediment in the upstream section (summer), (iii) competition between particles, non-extractable C 18 organic ligands and phytoplankton-released extractable C 18 organic ligands to complex copper in the downstream section (summer), and (iv) removal of non-extractable C 18 organic copper by adsorption (autumn). Dissolved copper species fluxes were assessed: most of metal inputs to the estuary (60-74%) corresponded to non-extractable C 18 organic copper. Winter and spring metal output fluxes were mainly constituted of non-extractable C 18 organic complexes; on the other hand, extractable C 18 organic complexes were predominant in summer and autumn output fluxes.

Waeles, Matthieu; Riso, Ricardo D.; Le Corre, Pierre

2005-01-01

115

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

116

pH Protocol  

NSDL National Science Digital Library

The purpose of this resource is to measure the pH of water. Students use either a pH meter or pH paper to measure the pH. If using the pH meter, the meter needs to be calibrated with buffer solutions that have pH values of 4, 7, and 10.

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

2005-06-02

117

Kinetics of the removal of dissolved aluminum by diatoms in seawater: A comparison with thorium  

SciTech Connect

Kinetic experiments were conducted using batch systems to investigate the removal of dissolved Al and [sup 234]Th tracer by dead Phaeodactylum tricornutum diatoms in seawater. Experiments were conducted at constant temperature (2 C), pH (7.8), and salinity (30 psu), using realistic oceanic concentrations of dissolved Al (50 nM), and 1, 2.5, 5, and 10 mg/l suspensions of dead diatoms in ultrafiltered (< 10,000 NMW) seawater. Results are characterized by a rapid initial removal followed by slower sorption of dissolved Al and [sup 234]Th by the diatoms on time scales ranging from hours to days. Both the removal rate and percentage of Al and [sup 234]Th removed are strong functions of the particle concentration (C[sub p]). Modelling the kinetic data as a reversible exchange of metal between solution and particles indicates a first-order dependence of the forward rate constants for Al and [sup 234]Th on C[sub p]. Extending these results to oceanic scavenging, it is shown that a first-order dependence exists between oceanic scavenging rate constants for Al and Th and suspended particle concentration for C[sub p] [approximately] 0.01-1 mg/l. This relationship is suggested to reflect the importance of physicochemical removal mechanisms (surface-adsorption, coagulation/sedimentation) rather than active biological uptake of dissolved Al and Th in oceanic waters. Oceanic scavenging rate constants for Al and Th qualitatively agree with removal rate constants predicted by the Brownian-pumping model for reactive metal scavenging.

Moran, S.B. (Woods Hole Oceanographic Inst., MA (United States)); Moore, R.M. (Dalhousie Univ., Halifax, NS (Canada))

1992-09-01

118

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

1998-11-01

119

Effects of Alkaline Treatment on Dissolved Carbohydrates in Suspensions of Norway Spruce Thermomechanical Pulp  

Microsoft Academic Search

The effects of alkaline treatment on dissolved carbohydrates in suspensions of Norway spruce thermomechanical pulp (TMP) were studied by agitating 1% consistency TMP suspensions at different pH values (5.4 to 12) for 3 h at 60°, followed by acidification and centrifugation to obtain water samples for analysis. It was found that at pH values above 8, dissolved galactoglucomannans were deacetylated,

Jeff Thornton; Rainer Ekman; Bjarne Holmbom; Charlotte Pettersson

1994-01-01

120

Modeling the interaction of dissolved organic matter with cations  

SciTech Connect

The last couple of decades have seen a variety of models for the binding of metals and protons by dissolved organic matter (DOM). This dissertation examined the continuing evolution of one of these models (Continuous Gaussian Distribution) (CGD), some of the underlying assumptions inherent in modeling DOM, and the incorporation of continuous distribution models into comprehensive, speciation computer programs. This thesis consisted of two distinct parts, one which deals with metal binding by DOM as it relates to the overall chemistry of rivers and ash ponds, and the other which concerns Suwannee river DOM binding of Pb. Initially, DOM was collected from the Clinch river in Tennessee and an adjacent power plant ash pond using a portable reverse osmosis unit. The concentrated DOM samples were subjected to alkalimetric and Cu(II) titrations using ionic selective electrodes to measure metal and proton complexation properties of the dissolved organic acids. The data were fit to the CGD models of Perdue and coworkers to determine the pK[sub a] distributions of major classes of acidic functional groups and to estimate the abundance and Log K distribution of metal binding sites in the DOM. Concentration based Gaussian and activity based competitive Gaussian modeling were compared. Fitting parameters from these modeling efforts were integrated into MINEQL and MINTEQA2 to examine the overall metal speciation in the river and ash pond. The other aspect of this study concerned Pb binding by Suwannee river DOM which had previously been isolated and characterized in relation to proton and Cu binding. Pb titrations were conducted at two ionic strengths, three pH's and two DOM concentrations. Fitting these data to the Competitive Gaussian model while varying parameters such as organic charge, stoichiometry and the number of binding sites helped to elucidate the effect of various solution conditions on the binding of Pb by DOM and to procure optimum fitting parameters.

Matlack, K.S.

1992-01-01

121

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

122

The Effects of Acid Rock Drainage (ARD) on Fluorescent Dissolved Organic Matter (DOM)  

NASA Astrophysics Data System (ADS)

Located in the Rocky Mountains of central Colorado, the catchments drained by the headwaters of the Snake River are dominated by metal- and sulfide-rich bedrock. The breakdown of these minerals results in acidic metal-rich waters in the Snake (pH ~3) that persist until the confluence with Deer Creek (pH ~7). Previous research has been conducted examining the interactions of acid-rock drainage (ARD) and dissolved organic matter (DOM), but the effects of ARD on DOM production is not as well understood. In a synoptic study, samples of creek water were collected at evenly spaced intervals along the length of a tributary to the Snake River which drains an area with ARD. At each sampling location, water samples were collected and pH, conductivity, and temperature were measured. Water samples were analyzed for metal chemistry, and the DOM was analyzed with UV-Vis and fluorescence spectroscopy. The character of the DOM was described using PARAFAC and index calculations. This work demonstrates that the introduction of acid and dissolved metal species has notable effects on DOM composition. Preliminary data suggests that the introduction of acid drainage is responsible for the formation of a fluorophore not accounted for in the Cory and McKnight PARAFAC model. Both high concentrations of heavy metals (e.g. zinc) and the novel fluorophore are present downstream from a mining site, which indicates it as a possible source of both species. The data suggest a link between the introduction of fluorophores in acidic waters and acidophile populations at the source of the acid rock drainage.

Lee, R. H.; Gabor, R. S.; SanClements, M.; McKnight, D. M.

2011-12-01

123

Experimental study of the effects of Bacillus subtilis on gibbsite dissolution rates under near-neutral pH and nutrient-poor conditions  

Microsoft Academic Search

In order to examine the effects of Bacillus subtilis on rates and extents of gibbsite dissolution, we conducted batch-type dissolution experiments with viable, non-viable, and no bacteria. Dissolved Al and organic carbon were monitored at regular time intervals for approximately 10 days under near-neutral pH and nutrient-poor conditions that simulated the conditions under which natural fluid–mineral interactions occur. Viable bacteria

Jong-Un Lee; Jeremy B. Fein

2000-01-01

124

ICPP custom dissolver explosion recovery  

Microsoft Academic Search

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

R. Demmer; R. Hawk

1992-01-01

125

METHOD OF DISSOLVING URANIUM METAL  

Microsoft Academic Search

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

Slotin

1958-01-01

126

Abiotic Synthesis of Methane Under Alkaline Hydrothermal Conditions: the Effect of pH in Heterogeneous Catalysis  

NASA Astrophysics Data System (ADS)

Abiotic formation of methane in hydrothermal reaction zones at mid-ocean ridges likely occurs by Fischer-Tropsch catalytic processes involving reaction of CO2-bearing fluids with mineral surfaces. The elevated concentrations of dissolved methane and low molecular weight hydrocarbons observed in high temperature vent fluids issuing from ultramafic-hosted hydrothermal systems, in particular, suggest that Fe and Cr-bearing mineral phases attribute as catalysts, enhancing abiotic production of alkanes. The chemi-adsorption of dissolved CO2 on the catalytic mineral surface, however, might be influenced by a pH dependent surface electron charge developed within the mineral-fluid interface. Thus, a series of experiments was conducted to evaluate the role of pH on rates of carbon reduction in fluids coexisting with Fe-oxides at 390 degree C and 400 bars. At two distinct pH conditions, acidic (pH = 5) and alkaline (pH = 8.8), the abiotic production of isotopically labelled CH4(aq) was monitored during FeO reaction with aqueous NaCl-NaHCO3-H2-bearing fluid (0.56 mol/kg NaCl, 0.03 mol/kg NaH13CO3). Despite the lower H2(aq) concentrations (120 mmol/kg) in the high pH system, concentrations of abiogenic methane attained values of 195 umol/kg and 120 umol/kg respectively, suggesting enhanced catalytic properties of mineral under moderately high pH. X-ray photoelectron spectroscopy (XPS), performed on unreacted and final solid products, reveal the significantly greater abundances of alkyl (C-C-) groups on the surface of FeO oxidized at elevated pH, in comparison with mineral reacted at low pH conditions. Thus, enhanced adsorption of dissolved CO2 and the resulting Fischer-Tropsch formation of alkyl groups likely contributes to methane production observed at alkaline conditions. Introducing the effect of pH in the Fischer-Tropsch mechanism of alkane formation has important implications for the recently discovered Lost City ultramafic-hosted hydrothermal system, where elevated pH and high CH4 concentrations in the moderate temperature vent fluids are observed.

Foustoukos, D. I.; Qi, F.; Seyfried, W. E.

2004-12-01

127

Middle School Chemistry: The Water Molecule and Dissolving  

NSDL National Science Digital Library

This set of multimedia lessons, developed by the American Chemical Society, examines the process of dissolving materials in water. Videos, interactive simulations, hands-on labs, and demonstrations are all integrated into a 9-part unit of instruction that includes assessments and background information. Students will explore why water dissolves salt and sugar, conduct solubility tests, investigate how temperature affects dissolving, and more. Editor's Note: The authors designed this curriculum to help students understand basic chemistry within a framework of molecular interactions. The molecular models and related animations provide a foundation for understanding states of matter, atomic models and bonding, charge interactions, and chemical change.

Galvan, Patti; Kessler, Jim

2011-06-27

128

Seasonal changes in photochemical properties of dissolved organic matter  

NASA Astrophysics Data System (ADS)

The fate of dissolved organic matter (DOM) in lakes and streams is significantly affected by photochemical transformation of DOM. A series of laboratory photochemical experiments was conducted to describe long-term changes in photochemical properties of DOM. The stream samples used in this study originated from three different catchments on the southern-most part of the Boreal ecozone near Dorset, Ontario, Canada. A first-order kinetics equation was used to model photochemical degradation of DOM and the kinetic rate constant, K, was used as an indicator of photochemical properties of DOM. Highest Kwas observed in samples from the catchment dominated by coniferous forest while the lowest K was measured in the deciduous catchment. Kinetic rate constants from all three catchments showed a sinusoidal pattern during the hydrological year. K increased steadily during autumn and winter and decreased during spring and summer. The highest values were observed during spring melt events when DOM was flushed from terrestrial sources by high flows. The minimum rate constants were found in summer when discharge was lowest. DOM molecular weight and specific absorbance at 254 nm also exhibited annual cycles corresponding to the seasonal cycles of terrestrial organic matter but the relationships between these properties and K was probably affected by previous exposure to solar radiation during transit from the catchment as well as pH and iron.

Porcal, P.; Dillon, P. J.; Molot, L. A.

2013-03-01

129

Artificial neural network modeling of dissolved oxygen in reservoir.  

PubMed

The water quality of reservoirs is one of the key factors in the operation and water quality management of reservoirs. Dissolved oxygen (DO) in water column is essential for microorganisms and a significant indicator of the state of aquatic ecosystems. In this study, two artificial neural network (ANN) models including back propagation neural network (BPNN) and adaptive neural-based fuzzy inference system (ANFIS) approaches and multilinear regression (MLR) model were developed to estimate the DO concentration in the Feitsui Reservoir of northern Taiwan. The input variables of the neural network are determined as water temperature, pH, conductivity, turbidity, suspended solids, total hardness, total alkalinity, and ammonium nitrogen. The performance of the ANN models and MLR model was assessed through the mean absolute error, root mean square error, and correlation coefficient computed from the measured and model-simulated DO values. The results reveal that ANN estimation performances were superior to those of MLR. Comparing to the BPNN and ANFIS models through the performance criteria, the ANFIS model is better than the BPNN model for predicting the DO values. Study results show that the neural network particularly using ANFIS model is able to predict the DO concentrations with reasonable accuracy, suggesting that the neural network is a valuable tool for reservoir management in Taiwan. PMID:24078053

Chen, Wei-Bo; Liu, Wen-Cheng

2014-02-01

130

In situ removal of dissolved and suspended contaminants from a eutrophic pond using hybrid sand-filter.  

PubMed

In this study, in situ hybrid sand filters were designed to remove dissolved and suspended contaminants from eutrophic pond. Currently, there are no attempts made to eradicate dissolved as well as suspended contaminants from eutrophic water system in a single step. Monitoring studies revealed that examined pond contain high chlorophyll-a content (101.8 ?g L(-1)), turbidity (39.5 NTU) and total dissolved solids concentration (0.04 g L(-1)). Samples were further exposed to extensive water quality analysis, which include examining physicochemical parameters (pH, conductivity, total dissolved solids, salinity, turbidity and chlorophyll-a), metals (Na, K, Ca, Mg, Al, Fe, Cu, Cd, Pb, Zn, Cr, and Ni) and anions (NO3, NO2, PO4, SO4, Cl, F and Br). To tackle pollutants, filtration system was designed to comprise of several components including fine sand, coarse sand/sorbent mix and gravel from top to bottom loaded in fiberglass tanks. All the filters (activated carbon, Sargassum and zeolite) completely removed algal biomass and showed potential to decrease pH during entire operational period of 20 h at 120 L h(-1). To examine the efficiency of filters in adverse conditions, the pond water was spiked with heavy metals (Cu, Cd, Pb, Zn, Cr, and Ni). Of the different filter systems, Sargassum-loaded filter performed exceedingly well with concentrations of heavy metals never exceeded the Environmental protection agency regulations for freshwater limits during total operational period. The total uptake capacities at the end of the fifth event were 24.9, 20.5, 0.58, 5.2, 0.091 and 2.8 mg/kg for Cr, Ni, Cu, Zn, Cd and Pb, respectively. PMID:24844899

Vijayaraghavan, K; Joshi, Umid Man; Ping, Han; Reuben, Sheela; Burger, David F

2014-08-24

131

The Measurement of Dissolved Oxygen  

ERIC Educational Resources Information Center

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

Thistlethwayte, D.; And Others

1974-01-01

132

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

2013-10-01

133

Removal of dissolved metals by plant tissue  

SciTech Connect

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

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

1992-04-25

134

Formulation Development and Evaluation of Fast Dissolving Film of Telmisartan  

PubMed Central

Hypertension is a major cause of concern not just in the elderly but also in the youngsters. An effort was made to formulate a fast dissolving film containing telmisartan which is used in the treatment of hypertension with a view to improve the onset of action, therapeutic efficacy, patient compliance and convenience. The major challenge in formulation of oral films of telmisatran is that it shows very less solubility in the pH range of 3–9. Various film forming agents and polyhydric alcohols were evaluated for optimizing composition of fast dissolving films. Fast dissolving films using hydroxypropyl methylcellulose, polyvinyl alcohol, glycerol, sorbitol, menthol and an alkalizer were formulated using solvent casting method. Optimized formulations were evaluated for their weight, thickness, folding endurance, appearance, tensile strength, disintegration time and dissolution profile.

Londhe, Vaishali Y.; Umalkar, Kashmira B.

2012-01-01

135

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

136

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

USGS Publications Warehouse

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 C??L-1 (as acetate) to stream sediments reduced nitrification rates (P < 0.003), but lower concentration additions or dilution of ambient DOC concentration had no effect on nitrification. C:N and organic N availability strongly interacted to affect nitrification (P < 0.0001), with N availability increasing nitrification most at lower C:N. Nitrification was also strongly influenced by pH (P < 0.002), with maximum rates occurring at pH 7.5. A multiple regression model developed from the stream survey consisted of five variables (stream temperature, pH, conductivity, DOC concentration, and total extractable NH4+) and explained 60% of the variation observed in nitrification. Our results suggest that nitrification is regulated by several variables, with NH4+ availability and pH being the most important. Organic C is likely important at regulating nitrification only under high environmental C:N conditions and if most available C is relatively labile.

Strauss, E. A.; Mitchell, N. L.; Lamberti, G. A.

2002-01-01

137

The Influence of pH on the Oxygen Isotope Composition of Calcium Carbonate  

NASA Astrophysics Data System (ADS)

Oxygen isotope fractionation between calcium carbonate and water is temperature-dependent and can therefore be used as a paleothermometer. Although oxygen isotope fractionation is expected from principles of equilibrium isotopic partitioning, the temperature-dependence remains uncertain because other factors, such as slow exchange between dissolved inorganic carbon (DIC) species and water, can obscure the temperature signal. Oxygen isotopic equilibrium between aqueous solution and calcium carbonate includes two distinct equilibria: equilibrium of the DIC species in solution (i.e., CO2(aq), H2CO3, HCO3-, and CO32-) with water, and equilibrium between the dissolved inorganic carbon with the precipitated carbonate. To isolate kinetic isotope effects that arise at the mineral-solution interface, isotopic equilibrium among DIC species must be maintained. This can be accomplished by dissolving the enzyme carbonic anhydrase (CA) into the solution, thereby reducing the time required for isotopic equilibration between DIC species by approximately two orders of magnitude between pH 7.7 and 9.3. We conduct calcite growth experiments aimed specifically at measuring the pH-dependence of kinetic oxygen isotope effects during precipitation of calcite. We precipitated calcite from aqueous solution at a constant pH and controlled supersaturation over the pH range 7.7-9.3. For each experiment, a gas mixture of N2 and CO2 is constantly bubbled through a beaker containing ~1300 mL of solution (30 mM CaCl2 + 5 mM NH4Cl + 0.1 mM SrCl2). As CO2 from the gas dissolves into solution, calcite crystals grow on the beaker walls. The pH of the solution is maintained by use of an autotitrator with NaOH as the titrant. We control the temperature, pH, the pCO2 of the gas inflow, and the gas inflow rate, and monitor the total alkalinity, the pCO2 of the gas outflow, and the amount of NaOH added. A constant crystal growth rate of ~1.6 mmol/m2/hr is maintained over all experiments. We will present results from this set of experiments and discuss kinetic oxygen isotope effects in the context of a recently-developed ion-by-ion growth model of calcite.

Hunt, J. D.; Watkins, J. M.; Ryerson, F. J.; DePaolo, D. J.

2013-12-01

138

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

2013-04-01

139

Mineralization of dissolved organic phosphorus from a shallow eutrophic lake  

Microsoft Academic Search

Release of soluble reactive phosphorus (SRP) from dissolved organic phosphorus (DOP), concentrated by reverse osmosis of water\\u000a samples from Lough Neagh Northern Ireland, was measured in the presence of enzymes and cultures of lake water bacteria in\\u000a a basal liquid medium adjusted to the pH of lake water (7.6). No hydrolysis of unfractionated DOP was observed in the presence\\u000a of

J. E. Cooper; J. Early; A. J. Holding

1991-01-01

140

Aerobic sludge digestion under low dissolved oxygen concentrations.  

PubMed

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

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

2004-01-01

141

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

NASA Astrophysics Data System (ADS)

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

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

142

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

143

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.

144

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

2013-01-01

145

Science Shorts: The Dynamics of Dissolving  

NSDL National Science Digital Library

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

Kessler, James; Galvan, Patti

2006-02-01

146

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

NSDL National Science Digital Library

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

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

2006-06-18

147

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

148

Understanding pH  

NSDL National Science Digital Library

The first site related to pH is from the Horiba corporate Web site entitled the Story of pH (1). Visitors can learn what pH is and how it's measured, explore various facts about pH, and read several anecdotes such as "Is the Rain in Our Cities Acidic." The site contains simple text, attractive graphics, and a well-designed layout making it fun and easy for anyone to explore. The second site from the Miami Museum of Science is called the pH Factor (2) kids activity page. This interactive and extensive site contains lessons on testing items for pH, tasting acids and bases, an interactive meter to find the pH of common household items, and much more. Next, is the pH and Water Quality (3) page, which is part of the State of Kentucky Division of Water Web site. The site provides a table of the effects of pH on fish and aquatic life and gives a short description of the most significant environmental impacts of pH. Trout for example, can tolerate a pH range between 4.1 and 9.5 while Mosquito larvae can survive within the 3.3 and 4.7 range. The fourth site from Gardengate Magazine.com is entitled More Soil Stuff: Soil pH (4). Described is the pH range of most soil types, requirements of certain plants, how to test soil for pH, and how to adjust it using sulfur and limestone. Seaworld.org maintains the Understanding the pH Cycle within the Aquarium (5) lesson plan site. The stated objective of the activity is to have students define pH, explain how it affects a tank's water quality, and test the pH level in a classroom aquarium. Although an aquarium is obviously needed, the activity offers a unique and fun way for kids to learn about this basic chemistry concept. About.com offers the next site, which is an interactive pH calculator called pH (6). Users simply enter a pH to get the concentration of Hydrogen ions or, conversely, the Hydrogen ion concentration to get the pH. Another tool to learn about pH and Hydrogen ions is called Acids and Alkalis--the pH Scale (7). Provided by Purchon.com, the interactive pH scale illustrates how the ion concentration changes with pH, common acids associated with each, and whether it is a weak or strong acid or alkali. The last site maintained by the National Park Service is called Acid Rain Lesson Plan: Activity 1 The pH Scale (8). Kids will be able to describe the pH scale and its components, explain why a pH measurement must be accurate, and explain why small changes in pH are important. Everything needed to complete the activity is provided, including a materials list, complete instructions, thinking questions, as well as links for further information.

Brieske, Joel A.

149

ICPP custom dissolver explosion recovery  

Microsoft Academic Search

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

R. Demmer; R. Hawk

1992-01-01

150

Wormhole formation in dissolving fractures  

Microsoft Academic Search

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

P. Szymczak; A. J. C. Ladd

2009-01-01

151

Manual for Dissolved Oxygen Analysis.  

National Technical Information Service (NTIS)

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

H. C. Edgington

1971-01-01

152

Optimization of Dissolved Oxygen Measurements.  

National Technical Information Service (NTIS)

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

H. C. Edgington

1971-01-01

153

A field control release test for assessing plausibility of dissolved CO2 measurements for CO2 leakage detection in a shallow aquifer  

NASA Astrophysics Data System (ADS)

Detecting Co2 leakage signals in the shallow aquifer is one of the most changing issues because of high variability in groundwater chemistry and also interactions among CO2, aquifer materials and groundwater. This study presents a novel technology for detecting CO2 leakage by measuring dissolved CO2 in groundwater using an optical CO2 sensor. The control release test was conducted in the field laboratory, Brackenridge Field Lab where shallow aquifer is unconfined with bedrock at the depth of 6 m below surface. Several groundwater wells were drilled and screened at depths from 3 m to 6 m. Fiber optic distributed sensors for dissolved CO2 monitoring were installed in a well bore and connected to a computer for automatically measuring dissolved CO2 gas in groundwater for every 30 seconds. CO2 gas was bubbled into a well bore for about two hours and then was stopped. In addition, Nabr solution was added to the wellbore and Br was used as a tracer. Groundwater samples were collected periodically from the well for measuring groundwater pH, titrating alkalinity and analyzing DIC and concentrations of major ions. A reactive transport model by considering water-rock-CO2 interactions was used to simulate the control release test. Both field and modeling results show that dissolved CO2 measurements with an optical Co2 sensor can be used for detecting CO2 leakage in groundwater.

Yang, C.; Delgado, J.; Philips, S. B.; Mickler, P. J.; Guzman, N.

2013-12-01

154

A revised scheme for the reactivity of iron (oxyhydr)oxide minerals towards dissolved sulfide  

Microsoft Academic Search

The reaction between dissolved sulfide and synthetic iron (oxyhydr)oxide minerals was studied in artificial seawater and 0.1 M NaCl at pH 7.5 and 25°C. Electron transfer between surface-complexed sulfide and solid-phase Fe(III) results in the oxidation of dissolved sulfide to elemental sulfur, and the subsequent dissolution of the surface-reduced Fe. Sulfide oxidation and Fe(II) dissolution kinetics were evaluated for freshly

Simon W. Poulton; Michael D. Krom; Robert Raiswell

2004-01-01

155

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

156

Dissolved oxygen as a key parameter to aerobic granule formation  

Microsoft Academic Search

Much research has asserted that high shear forces are necessary for the formation of aerobic granular sludge in Sequencing Batch Reactors (SBRs). In order to distinguish the role of shear and dissolved oxygen on granule formation, two separate experiments were conducted with three bench-scale SBRs. In the first experiment, an SBR was operated with five sequentially decreasing superficial upflow gas

B. S. McSwain Sturm; R. L. Irvine

2008-01-01

157

Dissolved organic matter in Arizona reservoirs: assessment of carbonaceous sources  

Microsoft Academic Search

Most studies of freshwater dissolved organic matter (DOM) have been conducted in temperate climates where allochthonous organic material is abundant. Because climatic conditions of the Southwestern USA are different than temperate environments, DOM from three freshwater reservoirs (Saguaro Lake, Bartlett Lake and Lake Pleasant) was investigated to determine the importance of allochthonous and autochthonous organic material. Results from the study

Heath Mash; Paul K Westerhoff; Lawrence A Baker; Ronald A Nieman; My-Lihn Nguyen

2004-01-01

158

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

159

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

160

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

161

Dissolved organic carbon and nitrogen relationships in forest litter as affected by nitrogen deposition  

Microsoft Academic Search

Dissolved forms of carbon and nitrogen have become recognized for their importance in forest nutrient cycling. The role of dissolved organic carbon (DOC) as an energy source for microbial metabolism is of particular interest. A laboratory decomposition experiment was conducted to examine the relationship between potential increased N inputs (via acid deposition) and DOC production in the forest litter layer

Alison H. Magill; John D. Aber

2000-01-01

162

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...

163

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

164

Exercise and Pulmonary Hypertension (PH)  

MedlinePLUS

... International PH News and Projects Let Me Breathe Music Video PATIENTS Patients Newly Diagnosed Request an Envelope ... International PH News and Projects Let Me Breathe Music Video Help spread PH awareness and share PH ...

165

Solubility and Diffusivity of Water in Basic Silicate Melts at Low pH2O  

NASA Astrophysics Data System (ADS)

Solubility experiments were conducted at 1 atm by equilibrating melts corresponding to a synthetic Apollo 15 yellow glass (AY) [1] and the 1 atm eutectic composition on the anorthite-diopside join (AD) with H2O-CO2 gas mixtures at 1350°C. Each melt composition was equilibrated at a range of pH2O, pH2, and pO2 (by varying the H2/CO2 ratio of the gas); concentrations of hydroxyl (OH) in the quenched glasses were measured by FTIR and ranged from 10s to 100s of ppm. Our results confirm that the concentrations of OH dissolved in both the AY and AD melts are proportional to pH2O0.5 under these conditions. Moreover, the amount of dissolved OH depends only on pH2O and is independent of pH2 and pO2 across the significant experimental range (6 orders of magnitude in pO2 and 3 orders of magnitude in pH2/pH2O). Apparent diffusivities of total water (D*water [2, 3]) were determined in AD melt at 1350°C and 1 atm over significant ranges of pH2/pH2O (~0.013-1.4) and pO2 (IW-0.5 to IW+3.5). AD melts were fused in a Pt crucible at 1350°C and IW+1 for ~70 hr under a CO-CO2 gas mixture. Samples equilibrated in this way contain < 50 ppm water as OH (as measured by FTIR). With the dehydrated sample still hanging in the furnace, the gas mixture was changed to a H2-CO2 mixture, fixing pH2O and pH2 and maintaining the same pO2 as in the CO-CO2 gas mixture. After exposure to the H2-CO2 gas mixture for 5-10 min (which generated a ~103 ?m diffusion profile in OH inward from the sample edge), the sample was quenched in deionized H2O. The diffusively generated concentration profiles in four experimental AD charges were measured by FTIR and SIMS. The four diffusion experiments on AD melt yield best-fit values for D*water of 1-3 × 10-10 m2s-1. Our results demonstrate that D*water is approximately constant over two orders of magnitude in pH2/pH2O, implying that diffusion of H2 does not make a significant contribution to the transport of total water in AD melt under these conditions. D*water determined in this study is ~10-100 times greater than D*water predicted by extrapolations of the speciation model [2, 3] that assumes mobile H2O molecules (with constant DH2Omol) and immobile OH groups (DOH=0). However, our preliminary results are well described by a modified speciation model in which hydroxyl groups are allowed to diffuse. This is consistent with the findings of [4] for haploandesite melt. Extension of these measurements of the diffusivity of OH to closer analogues of lunar basaltic melts will improve understanding of the mobility of H-bearing species in nature and will be directly applicable to modeling degassing of lunar magmas [e.g., 5, 6]. [1] Delano (1986) JGR, 91(B4), D201-D213. [2] Zhang et al. (1991) GCA, 55, 441-456. [3] Zhang & Stolper (1991) Nature, 351, 306-309. [4] Ni et al. (2012) submitted. [5] Saal et al. (2008) Nature, 454, 192-195. [6] Hauri et al. (2011) Science, 333, 213-215.

Newcombe, M.; Brett, A.; Beckett, J.; Baker, M. B.; Newman, S.; Stolper, E. M.

2012-12-01

166

Effect of dissolved gas on bubble nucleation  

Microsoft Academic Search

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

Y. Mori; K. Hijikata; T. Nagatani

1976-01-01

167

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

168

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

169

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

170

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

171

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

NASA Astrophysics Data System (ADS)

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

Hernes, Peter J.; Benner, Ronald

2003-09-01

172

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

PubMed

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

Heddam, Salim

2014-08-01

173

Wormhole formation in dissolving fractures  

NASA Astrophysics Data System (ADS)

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

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

2009-06-01

174

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

175

Effect of dissolved oxygen on etching process of Si(111)in 2.5% NH 3 solution  

NASA Astrophysics Data System (ADS)

Etching processes of Si(111) in 2.5% NH 3 solution (pH 12) were examined with attention to the effect of oxygen dissolved in the solution. Atomic force microscopy observation showed that many etch pits were formed on the surface in the solution containing dissolved oxygen at high concentrations. In contrast, the surface was atomically flattened by removing dissolved oxygen from the solution. Infrared absorption spectroscopy revealed that the surface was hydrogen-terminated after treatment with the solutions with and without dissolved oxygen, and that dissolved oxygen degraded the homogeneity of the surface. It was also found that dissolved oxygen lowered the etching rate of Si(111) in the solution.

Fukidome, Hirokazu; Matsumura, Michio

2000-09-01

176

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

177

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

178

Method of dissolving metal oxides with di- or polyphosphonic acid and a redundant  

DOEpatents

A method of dissolving metal oxides using a mixture of a di- or polyphosphonic acid and a reductant wherein each is present in a sufficient amount to provide a synergistic effect with respect to the dissolution of metal oxides and optionally containing corrosion inhibitors and pH adjusting agents.

Horwitz, Earl P. (Argonne, IL) [Argonne, IL; Chiarizia, Renato (Argonne, IL) [Argonne, IL

1996-01-01

179

Control of cavitation using dissolved carbon dioxide for damage-free megasonic cleaning of wafers  

NASA Astrophysics Data System (ADS)

This dissertation describes the finding that dissolved carbon dioxide is a potent inhibitor of sonoluminescence and describes the implications of the finding in the development of improved megasonic cleaning formulations. Megasonic cleaning, or the removal of contaminants particles from wafer surfaces using sound-irradiated cleaning fluids, has been traditionally used in the semiconductor industry for cleaning of wafers. A critical challenge in the field is to achieve removal of small particles (22 nm to 200 nm) without causing damage to fine wafer features. The work described here addresses this challenge by identifying sonoluminescence and solution pH as two key factors affecting damage and cleaning efficiency, respectively and establishing novel means to control them using CO2(aq) release compounds in the presence of acids and bases. Sonoluminescence (SL) behavior of the major dissolved gases such as Ar, Air, N2, O2 and CO2 was determined using a newly designed Cavitation Threshold Cell (CT Cell). SL, which is the phenomenon of release of light in sound-irradiated liquids, is a sensitive indicator of cavitation, primarily transient cavitation. It was found that all the tested dissolved gases such as Ar, Air, N2 and O2, generated SL signal efficiently. However, dissolved CO2 was found to be completely incapable of generating SL signal. Based on this interesting result, gradual suppression of SL signal was demonstrated using CO2(aq). It was further demonstrated that CO2(aq) is not only incapable but is also a potent inhibitor of SL. The inhibitory role of CO2(aq) was established using a novel method of controlled in-situ release of CO 2 from NH4HCO3. ~130 ppm CO2(aq) was shown to be necessary and sufficient for complete suppression of SL generation in air saturated DI water. The method however required acidification of solution for significant release of CO2, making it unsuitable for the design of cleaning solutions at high pH. Analysis of the underlying ionic equilibria revealed that the loss of released CO2(aq) upon increase in pH can be compensated by moderate increase in added NH4HCO3. Using this method, simultaneous control of SL and solution pH was demonstrated in two systems, NH4HCO3/HCl and NH4OH/CO2, at two nominal pH values; 5.7 and 7.0. Damage studies were performed on wafer samples with line/space patterns donated by IMEC and FSI International bearing Si/metal/a-Si gate stacks of thickness ~36 nm and Si/Poly-Si gate stacks of thickness ~67 nm, respectively. A single wafer spin cleaning tool MegPieRTM was used for the generation of megasonic energy for inducing damage to the structures. It was demonstrated that CO2 dissolution in DI water suppresses damage to the gate stacks in a dose-dependent manner. Together, these studies establish a systematic and strong correlation between CO2(aq) concentration, SL suppression and damage suppression. Significant damage reduction (~50 % to ~90 %) was observed at [CO2(aq)] > ~300 ppm. It was also demonstrated that CO2(aq) suppresses damage under alkaline pH condition too. This demonstration was made possible by the successful design of two new cleaning systems NH4HCO3/NH4OH and CO2/NH 4OH that could generate CO2(aq) under alkaline conditions. Damage suppressing ability of the newly designed cleaning systems were compared to the standard cleaning system NH4OH at pH 8.2 and it was found that NH4HCO3/NH4OH and CO2/NH 4OH systems were 80 % more efficient in suppressing damage compared to the standard NH4OH cleaning system. Finally, megasonic cleaning studies were conducted in the same single wafer spin cleaning tool MegPieRTM, using SiO2 particles (size 185 nm) deposited on 200 mm oxide Si wafers, as the contaminant. It was found that the standard cleaning chemical, NH4OH, pH 8.2, was effective in achieving > 95 % particle removal for 2 min irradiation of megasonic energy at power densities > 0.7 W/cm2. Based on these results, a new system, NH4HCO3/NH4OH, was designed with an aim to release ~300 ppm CO2 at pH 8.2. It was demonstrated that newly designed system NH4

Kumari, Sangita

180

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 what…

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

2008-01-01

181

The effects of dissolved salt on the Leidenfrost transition  

Microsoft Academic Search

In this study, Leidenfrost experiments were conducted for water, NaCl, and KCl aqueous solutions at atmospheric pressure. In our tests, a 1.1g test liquid was gently deposited on a horizontal heated aluminum surface. The evaporation time at various surface temperatures was recorded and plotted as evaporation curves. To examine the relationship between bubble coalescence, dissolved salt and the Leidenfrost transition,

Chen-Kang Huang; Van P. Carey

2007-01-01

182

pH at Polarized Metal Surfaces: Theory, Measurement and Implications for MIC. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

Microorganisms growing on metal surfaces change to local dissolved oxygen concentration due to microbial respiration. Areas of oxygen depletion are anodic relative to surrounding areas. The pH at these areas decreases due to hydrolysis of metal ions. This...

Z. Lewandowski W. C. Lee W. Characklis B. Little

1990-01-01

183

Fractionation of residual Al in natural water treatment from reservoir with poly-aluminum-silicate-chloride (PASiC): effect of OH/Al, Si/Al molar ratios and initial pH.  

PubMed

An aluminum fractionation study was conducted for a surface reservoir water treatment to understand the performance of poly-aluminum-silicate-chloride (PASiC) in terms of the residual Al fractions as a function of initial pH. The coagulation performance expressed as turbidity and organic matter removal was established as supporting data. Some extra data were evaluated in terms of the residual Al ratio of the composite PASiC coagulant. The main residual Al sources were the Al fractions derived from the use of PASiC. The turbidity and organic matter removal ability was optimal at initial pH 6.00-7.00, while the concentrations of various residual Al species and the residual Al ratio of PASiC were minimal at an initial pH range of 7.00-8.00. Under the conditions of OH/Al molar ratio = 2.00 and Si/Al molar ratio = 0.05, PASiC had superior coagulation performance and comparatively low residual Al concentrations. The Al fraction in the composite PASiC coagulant seldom remained under such conditions. Experimental data also indicated that the suspended (filterable) Al fraction was the dominant species, and organic-bound or organo-Al complex Al was considered to be the major species of dissolved Al in water treated by PASiC coagulation. Additionally, the dissolved inorganic monomeric Al species dominated the dissolved monomeric Al fraction. PMID:23534222

Yang, Zhonglian; Gao, Baoyu; Wang, Yan; Zhao, Yaqin; Yue, Qinyan

2012-01-01

184

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

2013-08-01

185

Ph.D. shortage  

NASA Astrophysics Data System (ADS)

The late 1990s will see a shortage of Ph.D. graduates, according to the Association of American Universities, Washington, D.C. AAU's new comprehensive study, “The Ph.D. Shortage: The Federal Role,” reports that competition for new Ph.D.s is already intense and can only intensify because demand is greater than supply in both academic and nonacademic markets.Doctoral education plays an increasingly important role in U.S. research and development programs. Students have a pivotal part in doing research and enriching it with new ideas. The AAU report says that graduate students are “major determinants of the creativity and productivity of U.S. academic research, the source of more than 50% of the nation's basic research.’ The market for doctoral education extends beyond the university. In 1985, about 43% of all Ph.D.s employed in this country were working outside higher education; the demand for doctorate recipients in nonacademic sectors continues to grow.

186

Dissolved aluminum in the Mediterranean  

SciTech Connect

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

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

1988-08-01

187

Fast Dissolving Tablets of Aloe Vera Gel  

Microsoft Academic Search

Purpose : The objective of this work was to prepare and evaluate fast dissolving tablets of the nutraceutical, freeze dried Aloe vera gel. Methods: Fast dissolving tablets of the nutraceutical, freeze-dried Aloe vera gel, were prepared by dry granulation method. The tablets were evaluated for crushing strength, disintegration time, wetting time, friability, drug content and drug release. A 3 2

Jyotsana Madan; AK Sharma; Ramnik Singh

188

Effect of dissolved oxygen and Eh and Bacteroides fragilis during continuous culture.  

PubMed Central

Bacteroides fragilis subsp. fragilis was maintained in a chemostat modified for anaerobic conditions to test the effects of dissolved oxygen and Eh on growth. Using a defined medium containing glucose and a dilution rate of 0.16 h -1, a stable population of 3 X 10(9) colony-forming units/ml was present. At this steady state, the pH was 5.6, the Eh was -50 mV, and the dissolved oxygen concentration was 0% atmospheric saturation. The Eh was then adjusted to +300 mV by adding potassium ferricyanide while oxygen was excluded; in this system there were no demonstrable changes from the steady state in viable cells, pH, glucose concentration, or volatile fatty acid production. In other experiments oxygen was introduced into the original steady state at a dissolved oxygen concentration of 10% atmospheric saturation for a period of 6 to 8 h. During O2 exposure, the viable cell count decreased at a rate comparable to the theoretical washout rate for a static bacterial culture. Similar results were obtained with a dissolved oxygen concentration of 25 and 100%. Other effects of O2 exposure included an increase in Eh from -50 to +250 mV, a decrease in glucose consumption, and a decrease in volatile fatty acid production. These results suggest that dissolved oxygen has a bacteriostatic effect on B. fragilis in continuous culture, which may be independent of changes in Eh alone.

Onderdonk, A B; Johnston, J; Mayhew, J W; Gorbach, S L

1976-01-01

189

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

USGS Publications Warehouse

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

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

1996-01-01

190

Changes in dissolved and particulate copper following mixing of POTW effluents with Delaware River water  

Microsoft Academic Search

Effluents from publicly owned treatment works (POTWs) were mixed with Delaware River water at ratios of 1:1 or 1:2 effluent to Delaware River water. These mixing experiments were performed at pH 6, ambient pH and pH 8. In all mixing experiments, copper was released from effluent particulate matter when mixing was conducted at pH 6. No copper release was observed

Bo Shi; Herbert E. Allen; Marco T. Grassi

1998-01-01

191

Black Shale: A Source of Dissolved Organic Matter in Natural Waters  

NASA Astrophysics Data System (ADS)

Black shales are fine-grained laminated sedimentary rocks that are rich in organic matter (OM). Exposure of shales to earth surface environments results in oxidative weathering of the shale. While prior studies have demonstrated a loss of organic carbon during weathering of shales, other efforts have shown that rivers draining watersheds underlain with black shale transport significantly aged (14C-depleted) dissolved and particulate OM when compared to rivers draining other lithologies. Consequently, it is uncertain if complete oxidation of ancient sedimentary OM occurs within an outcrop during weathering, or whether black shales can be a source to rivers of OM that is distinct in composition and isotopic character from other pools such as soils, decaying vegetation, and authochthonous production. To address this, column experiments were initiated in which sterile, air-saturated water was passed through shale substrates packed in glass flow-through cells. A Late Devonian black shale from the Appalachian Basin, USA, (7.60% TOC) was used. The Type-II kerogen contained in this shale is representative of kerogen compositions found in most marine sedimentary rocks. Three parallel column experiments including crushed shale, solvent-extracted crushed shale, and a baked-sand blank have been continually monitored for several months. Effluent from the columns has been collected and analyzed daily for dissolved organic carbon concentrations (DOC). Solution pH, conductivity, major cations/anions, and 13C NMR spectra of effluent collected on solid-phase-extraction disks have also been monitored. Within several days after initiation of experiments, DOC concentrations exiting both columns stabilized at 0.5 mg/L, which equates to 3.2 x 10-3 mgcarbon/gtoc/hr or 2.2 x 10-4 mg_{carbon}/m^{2}/hr. At this rate, organic carbon in the 82g shale column will fully dissolve in 36 years. However, release of kerogen into solution is not likely to be simple dissolution, but instead dominated by absorption/desorption exchange with the kerogen and mineral matrix. Streams draining black shales exhibit DOC concentrations that are similar to what is observed in these column experiments, which suggests that during weathering, sedimentary rock rich in organic carbon may be a source of OM to river ecosystems. If this OM is not remineralized during transport, these waters may be one source of ^{14}$C-depleted organic matter to seawater that is distinct in composition from other terrestrial sources.

Schillawski, S.; Petsch, S.

2004-12-01

192

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

193

An improved method for fluorescence analysis of dissolved organic matter in cave drip water  

NASA Astrophysics Data System (ADS)

An improved synchronous fluorimetric method for the determination of dissolved organic matter in cave drip water, by adding ascorbic acid, is described. The method is based on the redox reaction between ascorbic acid and the electron-withdrawing constituents in dissolved organic matter. The results show that adding ascorbic acid can quench the minor peaks, at 200-300 nm, but does not affect the intensity of the main peaks at 300-500 nm. In addition, adding ascorbic acid can maintain relatively high and constant fluorescence intensity over a wide pH range (9-4).

Drijfhout, S. S.; Katsman, C. A.; de Steur, L.; van der Vaart, P. C. F.; van Leeuwen, P. J.; Veth, C.

2014-06-01

194

PH—Postharvest Technology  

Microsoft Academic Search

Thermal conductivity, specific heat capacity and thermal diffusivity of borage (Borago officinalis) seeds were determined at temperatures ranging from 6 to 20°C and moisture contents from 1·2 to 30·3% w.b. The thermal conductivity was measured by the transient technique using a line heat source. The maximum slope method was used to analyse the line source heating data for thermal conductivity

W. Yang; S. Sokhansanj; J. Tang; P. Winter

2002-01-01

195

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

196

Seasonal changes in photochemical properties of dissolved organic matter in small boreal streams  

NASA Astrophysics Data System (ADS)

The fate of dissolved organic matter (DOM) in lakes and streams is significantly affected by photochemical transformation of DOM. A series of laboratory photochemical experiments was conducted to describe seasonal changes in photochemical properties of DOM. The stream samples used in this study originated from three different catchments in the southernmost part of the Boreal ecozone near Dorset, Ontario, Canada. A first-order kinetics equation was used to model photochemical degradation of DOM and the kinetic rate constant, K, was used as an indicator of photochemical properties of DOM. Kinetic rate constants from all three catchments showed a sinusoidal pattern during the hydrological year. K increased steadily during autumn and winter and decreased during spring and summer with a more than 3-fold range in each stream. The highest values were observed during spring melt events when DOM was flushed from terrestrial sources by high flows. The minimum rate constants were found in summer when discharge was lowest. K was strongly correlated with pH and iron. DOM molecular weight and specific absorbance at 254 nm also exhibited annual cycles corresponding to the seasonal cycles of terrestrial organic matter, but the relationships between these properties and K differed between seasons and may have been affected by previous exposure to solar radiation during transit from the catchment.

Porcal, P.; Dillon, P. J.; Molot, L. A.

2013-08-01

197

Influence of dissolved hydrogen on aluminum-lithium alloy fracture behavior  

NASA Technical Reports Server (NTRS)

The objective of this work is to study the effects of dissolved hydrogen on the mechanical properties of 2090 and 2219 alloys. Prior to mechanical testing, potentiostatic and potentiodynamic tests were performed using NaCl/HCl solutions varying in pH from 1.5 to 7.5 (3.5 pct NaCl in deionized water). After analysis of the potentiodynamic curve for each solution, several potentiostatic experiments were conducted for various times (from 10 minutes to several hours) with a cathodic overpotential of 300 mV. These experiments were performed to select charging conditions. It is shown that the fracture of L-S and T-S orientations proceeds via slipping of layers in the S-T direction. The T-S and L-S orientations fractured with substantially higher propagation energy that the L-T and T-L orientations, due in large part to the extensive delamination propagation of the fracture.

Rivet, F. C.; Swanson, R. E.

1989-01-01

198

17-4 PH and 15-5 PH  

NASA Technical Reports Server (NTRS)

17-4 PH and 15-5 PH are extremely useful and versatile precipitation-hardening stainless steels. Armco 17-4 PH is well suited for the magnetic particle inspection requirements of Aerospace Material Specification. Armco 15-5 PH and 17-4 PH are produced in billet, plate, bar, and wire. Also, 15-5 PH is able to meet the stringent mechanical properties required in the aerospace and nuclear industries. Both products are easy to heat treat and machine, making them very useful in many applications.

Johnson, Howard T.

1995-01-01

199

Carbon monoxide and chromophoric dissolved organic matter cycles in the shelf waters of the northern California upwelling system  

Microsoft Academic Search

An annual program of approximately bimonthly seawater sampling was conducted off the coast of the Bodega Marine Laboratory in the California Current upwelling system (CCUS) to investigate controls on dissolved carbon monoxide (CO) and its photochemical parent, chromophoric dissolved organic matter (CDOM). A diel steady state model was developed to quantify CO sources and sinks throughout the day. Observed midday

Douglas A. Day; Ian Faloona

2009-01-01

200

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 ...

201

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

2013-05-01

202

Reactive solute transport in streams. 2. Simulation of a pH modification experiment  

USGS Publications Warehouse

We present an application of an equilibrium-based solute transport model to a pH-modification experiment conducted on the Snake River, an acidic, metal-rich stream located in the Rocky Mountains of Colorado. During the experiment, instream pH decreased from 4.2 to 3.2, causing a marked increase in dissolved iron concentrations. Model application requires specification of several parameters that are estimated using tracer techniques, mass balance calculations, and geochemical data. Two basic questions are addressed through model application: (1) What are the processes responsible for the observed increase in dissolved iron concentrations? (2) Can the identified processes be represented within the equilibrium-based transport model? Simulation results indicate that the increase in iron was due to the dissolution of hydrous iron oxides and the photoreduction of ferric iron. Dissolution from the streambed is represented by considering a trace compartment consisting of freshly precipitated hydrous iron oxide and an abundant compartment consisting of aged precipitates that are less soluble. Spatial variability in the solubility of hydrous iron oxide is attributed to heterogeneity in the streambed sediments, temperature effects, and/or variability in the effects of photoreduction. Solubility products estimated via simulation fall within a narrow range (pK(sp) from 40.2 to 40.8) relative to the 6 order of magnitude variation reported for laboratory experiments (pK(sp) from 37.3 to 43.3). Results also support the use of an equilibrium-based transport model as the predominate features of the iron and p H profiles are reproduced. The model provides a valuable tool for quantifying the nature and extent of pH- dependent processes within the context of hydrologic transport.

Runkel, R. L.; McKnight, D. M.; Bencala, K. E.; Chapra, S. C.

1996-01-01

203

Reduction of the efficiency of extraction of lipophilic chemicals from water by dissolved organic matter  

SciTech Connect

A study was made of the efficiency of liquid-liquid extraction of eight chlorinated hydrocarbons of varying lipophilicity from filtered organic-free water, soil humic acid solution, lacustrine dissolved organic matter solution, and a natural water. The efficiency of hexane extraction of the spiked chemicals without pH adjustment was reduced with increasing concentration of dissolved organic matter (DOM) and increasing chemical lipophilicity. At the same time, increasing amounts of the more lipophilic chemicals were found in subsequent extracts of the water at pH 12, and after chromic acid oxidation of the DOM. The results indicated that conventional liquid-liquid extraction underestimates the concentrations of dissolved highly lipophilic chemicals in fresh water, the extent of the underestimation depending upon the nature of the DOM. Sixteen-day exposure experiments with filtered natural waters containing roughly 5 mg/L DOM indicated that 6 to 8% of the most lipophilic chemical tested, mirex, was not recovered by standard hexane extraction without pH adjustment; with 5 mg/L of a soil-derived humic acid, 49% of mirex was not recovered by standard hexane extraction without pH adjustment. For highly lipophilic chemicals that are not destroyed by chromic acid oxidation, it is recommended that total concentrations in filtered or centrifuged fresh waters be determined by the chromic acid oxidation/extraction technique.

Maguire, R.J.; Batchelor, S.P.; Sullivan, C.A. [Canada Centre for Inland Waters, Burlington, Ontario (Canada)

1995-03-01

204

Carbonate mineral-dissolved silica interactions: Experimental study at 25--50 C  

SciTech Connect

Replacement of carbonate minerals by silica is a common feature of ancient sedimentary rocks and deep-sea sediments. Also, Mg-carbonates are used to scavenge silica in wastewaters which suggests that dissolved silica/carbonate mineral interactions can occur on short time scales as well. The authors present results of experiments conducted between 25 and 50 C of the rate, time dependence, and extent of aqueous SiO[sub 2] uptake from solutions ranging from 1.5 to 3.5 mM SiO[sub 2] onto well characterized Ca-Mg carbonates. Most experiments were conducted in Mg-free, artificial seawater solutions because of extreme supersaturation with respect to sepiolite at [Mg] > 0.01 and T > 35 C. Three different reaction conditions were investigated: (1) silica uptake during short term calcite overgrowth precipitation onto calcite seeds at fixed degrees of calcite supersaturation; (2) silica uptake near equilibrium with respect to calcite; and (3) silica uptake during the relatively long term (3 weeks) recrystallization of metastable carbonates (aragonite, 18 mol% Mg-calcite). Silica uptake onto carbonates is greatest during rapid carbonate precipitation. Calcite precipitation kinetics, however, were unaffected by the SiO[sub 2] interaction with carbonate surface is similar precipitation rates were observed at equivalent degrees of calcite supersaturation in silica-spiked and silica-free experiments. In near equilibrium experiments, SiO[sub 2] uptake was strongly time-dependent but smaller in magnitude and uptake was enhanced at higher SiO[sub 2] concentrations, lower pH, and higher temperature. In longer term aragonite and Mg-calcite recrystallization experiments. SiO[sub 2] uptake was similar to near-equilibrium experiments conducted with low Mg-calcite.

Klein, R.T.; Walter, L.M. (Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Geosciences)

1992-01-01

205

Fast Dissolving Sublingual Films of Ondansetron Hydrochloride: Effect of Additives on in vitro Drug Release and Mucosal Permeation.  

PubMed

Ondansetron hydrochloride, a 5 HT3 antagonist is a powerful antiemetic drug which has oral bioavailability of 60% due to hepatic first pass metabolism and has a short half-life of 5 h. To overcome the above draw back, the present study was carried out to formulate and evaluate fast dissolving films of ondansetron hydrochloride for sublingual administration. The films were prepared from polymers such as polyvinylalcohol, polyvinyl pyrrolidone, Carbopol 934P in different ratios by solvent casting method. Propylene glycol or PEG 400 as plasticizers and mannitol or sodium saccharin as sweeteners were also included. The IR spectral studies showed no interaction between drug and polymer or with other additives. Satisfactory results were obtained when subjected to physico-chemical tests such as uniformity of weight, thickness, surface pH, folding endurance, uniformity of drug content, swelling index, bioadhesive strength, and tensile strength. Films were also subjected to in vitro drug release studies by using USP dissolution apparatus. Ex vivo drug permeation studies were carried out using porcine membrane model. In vitro release studies indicated 81-96% release within 7 min and 66-80% within 7 min during ex vivo studies. Drug permeation of 66-77% was observed through porcine mucosa within 40 min. Higher percentage of drug release was observed from films containing the sweeteners. The stability studies conducted for a period of 8 weeks showed no appreciable change in drug content, surface pH, and in vitro drug release. PMID:21042474

Koland, M; Sandeep, Vp; Charyulu, Nr

2010-07-01

206

Desalination technology waste streams: Effect of pH and salinity on metabolism of marine microbial assemblages  

Microsoft Academic Search

Effluents from desalination technologies may influence natural bacterial assemblages due to changes in salinity, pH, dissolved organic carbon concentration (DOC), DOC quality and cellular hydrostatic pressure. Salinity, pH, and pressure change effects on heterotrophic bacterial production (as measured by leucine incorporation) were examined in experiments with surface water from the Delaware Bay, Atlantic Ocean and Pacific Ocean. Bacterial production decreased

M. T. Montgomery; T. J. Boyd; C. L. Osburn; R. E. Plummer; S. M. Masutani; R. B. Coffin

2009-01-01

207

Electrical Conductivity.  

ERIC Educational Resources Information Center

Examines Drude's classical (1900) theory of electrical conduction, details the objections to and successes of the 1900 theory, and investigates the Quantum (1928) theory of conduction, reviewing its successes and limitations. (BT)

Allen, Philip B.

1979-01-01

208

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

209

Progress in dissolving modified LEU Cintichem targets  

Microsoft Academic Search

A process is under development to use low-enriched uranium (LEU) metal targets for production of ⁹⁹Mo. 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

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

1996-01-01

210

Ratiometric sensor for dissolved oxygen in seawater  

NASA Astrophysics Data System (ADS)

A dissolved oxygen sensor for marine application is reported which is based on a ratiometric approach to the fluorescence intensity quenching of the ruthenium dye [Ru(II)-tris(4, 7-diphenyl-1, 10-phenanthroline)]2+. Both the ruthenium complex and the coumarin derivative dye have been entrapped in a porous sol-gel film. The membrane shows good optical response on exposure to low levels of dissolved oxygen in seawater. The design and limitations of such an optode membrane are discussed.

Poteau, Xavier; MacCraith, Brian D.

2003-03-01

211

Rheology of molten polystyrene with dissolved gases  

Microsoft Academic Search

Dissolved gases in polymers behave as excellent plasticizers, reducing viscosity significantly through the chain dilution effect and the addition of free volume. Rheological measurements and theoretical modeling are presented for molten polystyrene with dissolved gases, including carbon dioxide, 1,1-difluoroethane (R152a), and 1,1,1,2-tetrafluoroethane (R134a), which are considered to be environmentally acceptable for replacing previous ozone-depleting hydrochlorocarbon (HFC) refrigerants.^ A modified pressurized

Choongyong Kwag

1998-01-01

212

Geochemical Data for Upper Mineral Creek, Colorado, Under Existing Ambient Conditions and During an Experimental pH Modification, August 2005  

USGS Publications Warehouse

Mineral Creek, an acid mine drainage stream in south-western Colorado, was the subject of a water-quality study that employed a paired synoptic approach. Under the paired synoptic approach, two synoptic sampling campaigns were conducted on the same study reach. The initial synoptic campaign, conducted August 22, 2005, documented stream-water quality under existing ambient conditions. A second synoptic campaign, conducted August 24, 2005, documented stream-water quality during a pH-modification experiment that elevated the pH of Mineral Creek. The experimental pH modification was designed to determine the potential reductions in dissolved constituent concentrations that would result from the implementation of an active treatment system for acid mine drainage. During both synoptic sampling campaigns, a solution containing lithium bromide was injected continuously to allow for the calculation of streamflow using the tracer-dilution method. Synoptic water-quality samples were collected from 30 stream sites and 11 inflow locations along the 2-kilometer study reach. Data from the study provide spatial profiles of pH, concentration, and streamflow under both existing and experimentally-altered conditions. This report presents the data obtained August 21-24, 2005, as well as the methods used for sample collection and data analysis.

Runkel, Robert L.; Kimball, Briant A.; Steiger, Judy I.; Walton-Day, Katherine

2009-01-01

213

Measurement of dissolved carbon dioxide using colorimetric polymer films  

NASA Astrophysics Data System (ADS)

The hydrophobic bases tetradodecylammonium hydroxide (TDAOH) and tetrakisdecylammonium hydroxide (TKAOH) are to be used to solubilize the anionic form of m-cresol purple in ethyl cellulose to create a dry colorimetric thin polymer film sensor for CO2 in the gas phase or dissolved in solution. When used in aqueous solution, both TDAOH and TKAOH appear significantly more resistant to interference by protons or other ions at high concentration when compared with tetraoctylammonium hydroxide (TOAOH), the hydrophobic base which has been used for such work in previous studies. The TDAOH films are used as carbon dioxide sensors in aqueous solution at high ionic strength (e.g. 1 mol dm-3) and still appear blue at pH 1 after 1 h.

Mills, Andrew; Wild, Lorraine

1995-01-01

214

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

215

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

216

Transport and exchange of U-series nuclides between suspended material, dissolved load and colloids in rivers draining basaltic terrains  

NASA Astrophysics Data System (ADS)

This study presents uranium and thorium concentrations and activity ratios for all riverine phases (bedload, suspended load, dissolved load and colloids) from basaltic terrains in Iceland and the Azores. Small basaltic islands, such as these, are thought to account for ~ 25% of CO 2 consumed by global silicate weathering, and for ~ 45% of the flux of suspended material to the oceans. These data indicate that [U] and [Th] in the dissolved and colloidal fractions are strongly controlled by pH, and to a much lesser extent by levels of dissolved organic carbon (which are low in these environments). At high pH, basalt glass dissolution is enhanced, and secondary mineral formation (e.g. Fe-oxyhydroxides and allophane) is suppressed, resulting in high dissolved [U], and low colloidal [U] and [Th], indicating a direct chemical weathering control on elemental abundances. When the dissolved ( 234U/ 238U) activity ratio is >~1.3 (i.e. when physical weathering, groundwater contribution or soil formation are high), there is little isotope exchange between dissolved and colloidal fractions. At lower activity ratios, the dissolved load and colloids have indistinguishable activity ratios, suggesting that when chemical weathering rates are high, secondary clay formation is also high, and colloids rapidly adsorb dissolved U. Many of the suspended sediment samples have ( 234U/ 238U) activity ratios of > 1, which suggests that uptake of U onto the suspended load is important. Identical ( 230Th/ 232Th) in suspended, dissolved and colloidal samples suggests that Th, like U, is exchanged or sorbed rapidly between all riverine phases. This particle-reactivity, combined with poorly constrained contributions from groundwater and hydrothermal water, and short-term variations in input to soils (volcanic and glacial), suggests that U-series nuclides in riverine material from such basaltic terrains are unlikely to reflect steady state erosion processes.

Pogge von Strandmann, Philip A. E.; Burton, Kevin W.; Porcelli, Don; James, Rachael H.; van Calsteren, Peter; Gislason, Sigurður R.

2011-01-01

217

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

SciTech Connect

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

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

1984-01-01

218

Simultaneous E. coli inactivation and NOM degradation in river water via photo-Fenton process at natural pH in solar CPC reactor. A new way for enhancing solar disinfection of natural water.  

PubMed

Bacteria inactivation and natural organic matter oxidation in river water was simultaneously conducted via photo-Fenton reaction at "natural" pH ( approximately 6.5) containing 0.6 mg L(-1) of Fe(3+) and 10 mg L(-1) of H(2)O(2). The experiments were carried out by using a solar compound parabolic collector on river water previously filtered by a slow sand filtration system and voluntarily spiked with Escherichia coli. Fifty five percent of 5.3 mg L(-1) of dissolved organic carbon was mineralized whereas total disinfection was observed without re-growth after 24h in the dark. PMID:19716153

Moncayo-Lasso, Alejandro; Sanabria, Janeth; Pulgarin, César; Benítez, Norberto

2009-09-01

219

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,

220

Carbon Cycle - CDOM Activity: Chromophoric Dissolved Organic Matter (CDOM)  

NSDL National Science Digital Library

In this laboratory activity, students investigate chromophoric dissolved organic matter (CDOM) through gradual dilution of black, green and chamomile tea. Through this activity, students discover how CDOM can dominate the absorption of sunlight, how sunlight degrades CDOM through photochemical oxidation, and how CDOM levels are related to nutrient status, stratification and mixing of the ocean. Materials needed include coffee mugs, hot water, spoons, and tea. This resource is found in Rising Tides, a journal created for teachers and students reporting on current oceanography research conducted by NASA, NOAA, and university scientists, featuring articles, classroom activities, readings, teacher/student questions, and imagery for student investigation of marine science.

221

Natural attenuation of dissolved uranium within a small stream of central Japan  

Microsoft Academic Search

In this study, we investigated the natural attenuation of the uranium (U) load in the surface water within a humid forest\\u000a in Japan. Surface water and sediments that had accumulated behind dams in the area were investigated in terms of their mineralogy\\u000a and chemistry. The chemistry of the surface water was analyzed by field measurements of pH, dissolved oxygen (DO)

Mitsuo Manaka; Yoji Seki; Koichi Okuzawa; Hikari Kamioka; Yoshio Watanabe

2007-01-01

222

Cationic complexation with dissolved organic matter: Insights from molecular dynamics computer simulations and NMR spectroscopy  

Microsoft Academic Search

Dissolved organic matter (DOM) is ubiquitous in soil and surface water and plays many important geochemical and environmental roles acting as a proton donor\\/acceptor and pH buffer and interacting with metal ions, minerals and organic species to form water-soluble and water-insoluble complexes of widely differing chemical and biological stabilities. There are strong correlations among the concentration of DOM and the

A. G. Kalinichev; X. Xu; R. Kirkpatrick

2006-01-01

223

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

224

Formation of mixed Al–Fe colloidal sorbent and dissolved-colloidal partitioning of Cu and Zn in the Cement Creek – Animas River Confluence, Silverton, Colorado  

Microsoft Academic Search

Transport and chemical transformations of dissolved and colloidal Al, Fe, Cu and Zn were studied by detailed sampling in the mixing zone downstream from the confluence of Cement Creek (pH 4.1) with the Animas River (pH 7.6). Complete mixing resulted in circumneutral pH in the downstream reach of the 1300m study area. All four metals were transported through this mixing

Laurence E. Schemel; Briant A. Kimball; Robert L. Runkel; Marisa H. Cox

2007-01-01

225

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

226

Characterization of hydraulic conductivity of the alluvium and basin fill, Pinal Creek Basin near Globe, Arizona  

USGS Publications Warehouse

Acidic waters containing elevated concentrations of dissolved metals have contaminated the regional aquifer in the Pinal Creek Basin, which is in Gila County, Arizona, about 100 kilometers east of Phoenix. The aquifer is made up of two geologic units: unconsolidated stream alluvium and consolidated basin fill. To better understand how contaminants are transported through these units, a better understanding of the distribution of hydraulic conductivity and processes that affect it within the aquifer is needed. Slug tests were done in September 1997 and October 1998 on 9 wells finished in the basin fill and 14 wells finished in the stream alluvium. Data from the tests were analyzed by using either the Bouwer and Rice (1976) method, or by using an extension to the method developed by Springer and Gellhar (1991). Both methods are applicable for unconfined aquifers and partially penetrating wells. The results of the analyses show wide variability within and between the two geologic units. Hydraulic conductivity estimates ranged from 0.5 to 250 meters per day for the basin fill and from 3 to 200 meters per day for the stream alluvium. Results of the slug tests also show a correlation coefficient of 0.83 between the hydraulic conductivity and the pH of the ground water. The areas of highest hydraulic conductivity coincide with the areas of lowest pH, and the areas of lowest hydraulic conductivity coincide with the areas of highest pH, suggesting that the acidic water is increasing the hydraulic conductivity of the aquifer by dissolution of carbonate minerals.

Angeroth, Cory E.

2002-01-01

227

Characterization of Hydraulic Conductivity of the Alluvium and Basin Fill, Pinal Creek Basin near Globe, Arizona  

USGS Publications Warehouse

Acidic waters containing elevated concentrations of dissolved metals have contaminated the regional aquifer in the Pinal Creek Basin, which is in Gila County, Arizona, about 100 kilometers east of Phoenix. The aquifer is made up of two geologic units: unconsolidated stream alluvium and consolidated basin fill. To better understand how contaminants are transported through these units, a better understanding of the distribution of hydraulic conductivity and processes that affect it within the aquifer is needed. Slug tests were done in September 1997 and October 1998 on 9 wells finished in the basin fill and 14 wells finished in the stream alluvium. Data from the tests were analyzed by using either the Bouwer and Rice (1976) method, or by using an extension to the method developed by Springer and Gellhar (1991). Both methods are applicable for unconfined aquifers and partially penetrating wells. The results of the analyses show wide variability within and between the two geologic units. Hydraulic conductivity estimates ranged from 0.5 to 250 meters per day for the basin fill and from 3 to 200 meters per day for the stream alluvium. Results of the slug tests also show a correlation coefficient of 0.83 between the hydraulic conductivity and the pH of the ground water. The areas of highest hydraulic conductivity coincide with the areas of lowest pH, and the areas of lowest hydraulic conductivity coincide with the areas of highest pH, suggesting that the acidic water is increasing the hydraulic conductivity of the aquifer by dissolution of carbonate minerals.

Angeroth, Cory E.

2002-01-01

228

Toxicity identification evaluation of metal-contaminated sediments using an artificial pore water containing dissolved organic carbons  

SciTech Connect

Recent investigations of sediment-associated pollutants in Lake Champlain indicated significant contamination with As, Mn, and Ni in Outer Malletts Bay, Vermont, US. Ceriodaphnia dubia exposed to sediment pore water from several sites in Outer Malletts Bay showed repeatable, acute mortality at only one site. A toxicity identification evaluation (TIE) was conducted on pore water to determine the contaminants causing mortality at this site. Unlike most TIE applications, the dilution water used in these tests was formulated to match the hardness, alkalinity, pH, conductivity, and dissolved organic carbon content of the pore water. Results from phase 1 of the TIE indicated that divalent metals may be responsible for toxicity. Phase 2 results revealed levels of Mn above LC50 values. Spiking experiments employed in phase 3 confirmed Mn as the principal toxicant in sediment pore water. The formulated pore water worked well and helped ensure that toxicant behavior was influenced primarily by each TIE manipulation and not by physical and chemical differences between the dilution and site water. Although the Mn toxicity at this site may be the result of its unique geomorphology, this situation underscores the need to look broadly for potential toxicants when evaluating contaminated sites.

Boucher, A.M.; Watzin, M.C. [Univ. of Vermont, Burlington, VT (United States)

1999-03-01

229

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

230

Recent development and applications of optical and fiber-optic pH sensors  

Microsoft Academic Search

This article provides a brief review on the development and applications of optical and fiber-optic pH sensors in the 1990s. Various methods and materials for immobilization of pH indicators are surveyed. Different spectroscopic methods used for measurement with pH sensors are briefly discussed. Several special optical and fiber-optic pH sensors are reviewed, including pH sensors based on conductive polymers, imaging

Jie Lin

2000-01-01

231

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

USGS Publications Warehouse

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

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

2005-01-01

232

Chromophoric dissolved organic matter and dissolved organic carbon in Chesapeake Bay  

Microsoft Academic Search

Chromophoric dissolved organic matter (CDOM) is the light absorbing fraction of dissolved organic carbon (DOC). The optical properties of CDOM potentially permit remote sensing of DOC and CDOM, and correction for CDOM absorption is essential for remote sensing of chlorophyll a (chl a) in coastal and estuarine waters. To provide data for this purpose, we report the distributions of CDOM,

E. J. Rochelle-Newall; T. R. Fisher

2002-01-01

233

Method for dissolving hard-to-dissolve thorium and/or plutonium oxides  

SciTech Connect

Method for dissolving hard-to-dissolve thorium and/or plutonium oxides, especially dioxides such as ThO2, PuO2 or (U/Pu)O2 mixed oxides by heating the oxides in a hermetically sealed vessel in fluoride-free nitric acid. The use of a gas atmosphere containing oxygen in the sealed vessel is advantageous.

Ledebrink, F.-W.; Rosenkranz, W.; Stoll, W.

1985-07-09

234

Chemical and Isotopic Characterization of Rainwater Dissolved Organic Carbon and Chromophoric Dissolved Organic Matter  

Microsoft Academic Search

Chromophoric dissolved organic matter (CDOM) is a ubiquitous, integral component of atmospheric waters which comprises a significant fraction of the dissolved organic carbon (DOC) pool in the condensed phase. The presence of significant quantities of highly chromophoric DOM in atmospheric waters has profound ramifications with respect to a wide variety of fundamental processes in atmospheric chemistry because of its impact

G. B. Avery; R. J. Kieber; J. D. Willey; P. J. Seaton

2007-01-01

235

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

Microsoft Academic Search

Photochemical degradation of Congo River dissolved organic matter (DOM) was investigated to examine the fate of terrigenous DOM derived from tropical ecosystems. Tropical riverine DOM receives greater exposure to solar radiation, particularly in large river plumes discharging directly into the open ocean. Initial Congo River DOM exhibited dissolved organic carbon (DOC) concentration and compositional characteristics typical of organic rich blackwater

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

2009-01-01

236

PH—Postharvest Technology  

Microsoft Academic Search

This paper discusses the variation of relative permittivity, dielectric loss factor and loss tangent, and the a.c. conductivity of three varieties of parchment coffee (Coffea arabica L.) in the frequency range from 75 kHz to 5 MHz, at 21·0±0·9°C and 63±1% relative humidity. Included are curves showing the variation of these four dielectric properties on moisture (11·0 to 23·1% w.b.),

P. A. Berbert; D. M. Queiroz; E. F. Sousa; M. B. Molina; E. C. Melo; L. R. D. Faroni

2001-01-01

237

Summary of Dissolved Concentration Limits  

SciTech Connect

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

Yueting Chen

2001-06-11

238

Effect of pH on the coagulation performance of Al-based coagulants and residual aluminum speciation during the treatment of humic acid-kaolin synthetic water.  

PubMed

The fractionation and measurement of residual aluminum was conducted during the treatment of humic (HA)-kaolin synthetic water with Al(2)(SO(4))(3), AlCl(3) and polyaluminum chloride (PAC) in order to investigate the effect of pH on the coagulation performance as well as residual aluminum speciation. Experimental results suggested that turbidity removal performance varied according to the following order: AlCl(3)>PAC>Al(2)(SO(4))(3). HA removal performance of PAC was better than that of AlCl(3) under acidic condition. The optimum pH range for AlCl(3) and Al(2)(SO(4))(3) was between 6.0 and 7.0 while PAC showed stable HA and UV(254) removal capacity with broader pH variation (5.0-8.0). For the three coagulants, majority of residual aluminum existed in the form of total dissolved Al (60-80%), which existed mostly in oligomers or complexes formed between Al and natural organic matter or polymeric colloidal materials. PAC exhibited the least concentration for each kind of residual aluminum species as well as their percentage in total residual aluminum, followed by AlCl(3) and Al(2)(SO(4))(3) (in increasing order). Moreover, PAC could effectively reduce the concentration of dissolved monomeric Al and its residual aluminum ratio was the least among the three coagulants and varied little at an initial pH between 7.0 and 9.0. PMID:20188465

Yang, Zhong Lian; Gao, Bao Yu; Yue, Qin Yan; Wang, Yan

2010-06-15

239

Design and Evaluation of Fast Dissolving Tablets of Clonazepam  

PubMed Central

In the present work, fast dissolving tablets of clonazepam were prepared by direct compression method with a view to enhance patient compliance. Three super-disintegrants, viz., crospovidone, croscarmellose sodium and sodium starch glycolate in different ratios with microcrystalline cellulose (Avicel PH-102) along with directly compressible mannitol (Pearlitol SD 200) to enhance mouth feel. The prepared batches of tablets were evaluated for hardness, friability, drug content uniformity, wetting time, water absorption ratio and in vitro dispersion time. Based on in vitro dispersion time (approximately 13 s), three formulations were tested for the in vitro drug release pattern (in pH 6.8 phosphate buffer), short-term stability (at 40°/75% relative humidity for 6 mo) and drug-excipient interaction (IR spectroscopy). Among the three promising formulations, the formulation prepared by using 10% w/w of crospovidone and 35% w/w of microcrystalline cellulose emerged as the overall best formulation (t50% 1.8 min) based on the in vitro drug release characteristics compared to conventional commercial tablet formulation (t50% 16.4 min). Short-term stability studies on the formulations indicated that there were no significant changes in drug content and in vitro dispersion time (P<0.05).

Shirsand, S. B.; Suresh, Sarasija; Swamy, P. V.; Kumar, D. Nagendra; Rampure, M. V.

2008-01-01

240

Design and evaluation of fast dissolving tablets of clonazepam.  

PubMed

In the present work, fast dissolving tablets of clonazepam were prepared by direct compression method with a view to enhance patient compliance. Three super-disintegrants, viz., crospovidone, croscarmellose sodium and sodium starch glycolate in different ratios with microcrystalline cellulose (Avicel PH-102) along with directly compressible mannitol (Pearlitol SD 200) to enhance mouth feel. The prepared batches of tablets were evaluated for hardness, friability, drug content uniformity, wetting time, water absorption ratio and in vitro dispersion time. Based on in vitro dispersion time (approximately 13 s), three formulations were tested for the in vitro drug release pattern (in pH 6.8 phosphate buffer), short-term stability (at 40°/75% relative humidity for 6 mo) and drug-excipient interaction (IR spectroscopy). Among the three promising formulations, the formulation prepared by using 10% w/w of crospovidone and 35% w/w of microcrystalline cellulose emerged as the overall best formulation (t(50%) 1.8 min) based on the in vitro drug release characteristics compared to conventional commercial tablet formulation (t(50%) 16.4 min). Short-term stability studies on the formulations indicated that there were no significant changes in drug content and in vitro dispersion time (P<0.05). PMID:21369444

Shirsand, S B; Suresh, Sarasija; Swamy, P V; Kumar, D Nagendra; Rampure, M V

2008-11-01

241

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

2013-10-01

242

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

243

Long term patterns in dissolved organic carbon, major elements and trace metals in boreal headwater catchments: Trends, mechanisms and heterogeneity.  

NASA Astrophysics Data System (ADS)

The effects of climate change are currently apparent in the boreal landscape of northern Sweden. Warmer temperature and declining acid deposition are affecting runoff chemistry. These effects are mediated by landscape type. Markedly different responses are observed in streams draining forest and mire landscape elements. Here, we assess long-term water quality time-series from three nested headwater streams draining upland forest (C2), peat/mire (C4) and mixed (C7) (forest and mire) catchments. Temporal trends in weather and runoff (1981-2008); dissolved organic carbon concentration [DOC] (1993-2010) and other water quality parameters (1987-2011) were assessed. Historically, sulfate deposition is low in the region and is further declining. There was no significant annual trend in precipitation or runoff but a significant monotonic increasing trend existed in air temperature and length of growing season. Stream [DOC] was positively correlated with some trace metals (copper, iron and zinc) and negatively with several other chemical parameters (e.g. sulfate, conductivity, calcium). Both sulfate and conductivity showed declining trends, while a significant increase was observed in pH during winter and spring. Calcium and magnesium showed monotonic decreasing trends. The declining trajectories of stream base cation and sulfate concentrations during other times of the year were not accompanied by changes in pH and alkalinity. Water temperature increased significantly both annually and in most months while iron and DOC concentrations showed significant increases in autumn months. Though all streams showed significant positive trends in [DOC] in autumn, only C2 had a significant annual increasing trend. There was also a shift in the magnitude of variability in spring [DOC] and increasing trend of summer baseflow [DOC] in C2 and C7.

Oni, Stephen; Futter, Martyn; Bishop, Kevin; Kohler, Stephan; Ottosson-Lofvenius, Mikael; Laudon, Hjalmar

2013-04-01

244

Long term patterns in dissolved organic carbon, major elements and trace metals in boreal headwater catchments: trends, mechanisms and heterogeneity  

NASA Astrophysics Data System (ADS)

The boreal landscape is a complex, spatio-temporally varying mosaic of forest and mire landscape elements that control surface water hydrology and chemistry. Here, we assess long-term water quality time-series from three nested headwater streams draining upland forest (C2), peat/mire (C4) and mixed (C7) (forest and mire) catchments. Temporal trends in weather and runoff (1981-2008); dissolved organic carbon concentration [DOC] (1993-2010) and other water quality parameters (1987-2011) were assessed. There was no significant annual trend in precipitation or runoff but a significant monotonic increasing trend existed in air temperature and length of growing season. Stream [DOC] was positively correlated with some trace metals (copper, iron and zinc) and negatively with several other chemical parameters (e.g. sulfate, conductivity, calcium). Both sulfate and conductivity showed declining trends, while a significant increase was observed in pH during winter and spring. Calcium and magnesium showed monotonic decreasing trends. The declining trajectories of stream base cation and sulfate concentrations during other times of the year were not accompanied by changes in pH and alkalinity. Water temperature increased significantly both annually and in most months while iron and DOC concentrations showed significant increases in autumn months. Though all streams showed significant positive trends in [DOC] in autumn, only C2 had a significant annual increasing trend. There was also a shift in the magnitude of variability in spring [DOC] and increasing trend of summer baseflow [DOC] in C2 and C7.

Oni, S. K.; Futter, M. N.; Bishop, K.; Köhler, S. J.; Ottosson-Löfvenius, M.; Laudon, H.

2012-12-01

245

The surface chemistry of dissolving labradorite feldspar  

Microsoft Academic Search

Elastic recoil detection (ERD) analysis was used in conjunction with Rutherford backscattering (RBS) analysis to determine depth profiles of hydrogen, silicon, aluminum and calcium in labradorite crystals reacted under various pH conditions. The inventory of hydrogen in the mineral is strongly affected by solution pH. Hydrogen extensively infiltrates the mineral during reaction for 264 hours with solutions in the pH

W. H. Casey; H. R. Westrich; G. W. Arnold; J. F. Banfield

1989-01-01

246

Process for coal liquefaction in staged dissolvers  

DOEpatents

There is described an improved liquefaction process by which coal is converted to a low ash and low sulfur carbonaceous material that can be used as a fuel in an environmentally acceptable manner without costly gas scrubbing equipment. In the process, coal is slurried with a pasting oil, passed through a preheater and at least two dissolvers in series in the presence of hydrogen-rich gases at elevated temperatures and pressures. Solids, including mineral ash and unconverted coal macerals, are separated from the condensed reactor effluent. In accordance with the improved process, the first dissolver is operated at a higher temperature than the second dissolver. This temperature sequence produces improved product selectivity and permits the incorporation of sufficient hydrogen in the solvent for adequate recycle operations.

Roberts, George W. (Emmaus, PA); Givens, Edwin N. (Bethlehem, PA); Skinner, Ronald W. (Allentown, PA)

1983-01-01

247

Sediment–dissolved organic matter equilibrium partitioning of pentachlorophenol  

Microsoft Academic Search

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

Nina Paaso; Juhani Peuravuori; Tero Lehtonen; Kalevi Pihlaja

2002-01-01

248

Lithium ion conducting ionic electrolytes  

DOEpatents

A liquid, predominantly lithium-conducting, ionic electrolyte is described which has exceptionally high conductivity at temperatures of 100 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. 4 figs.

Angell, C.A.; Xu, K.; Liu, C.

1996-01-16

249

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

250

Production of Dissolved Organic Matter During Fungal Wood Rot Decay  

NASA Astrophysics Data System (ADS)

Dissolved organic matter mediates numerous biogeochemical processes in soil systems impacting subsurface microbial activity, redox chemistry, soil structure, and carbon and nitrogen sequestration. The structure and chemistry of DOM is a function of the inherited chemistry of the source material, the type of microbial action that has occurred, and selective interaction with mineral substrates. The type of fungal decomposition imparted to woody tissue is a major factor in determining the nature of DOM in forest soils. In order to investigate the relationship between fungal decomposition and the nature of DOM in coniferous forest soils we conducted 32-week inoculation studies on spruce sapwood with basidiomycete brown-rot wood decay fungi where leachable dissolved and colloidal organic matter was separated from decayed residue. A detailed examination of the organic fractions was conducted using 13C-labeled tetramethylammonium hydroxide thermochemolysis, solid-state 13C-NMR, and electrospray mass spectrometry. The progressive stages of microbial decay (cellulolytic and ligninolytic) were manifested in the chemical composition of the DOM which showed an evolution from a composition initially polysaccharide rich to one dominated by mildly oxidized and demethylated lignin. Upon removal of all polysaccharides at 16 weeks the DOM (up to 10% by weight of the original tissue) looked chemically distinct from the degraded residue

Filley, T. R.; Jellison, J.; Goodell, B.; Kelley, S.; Davis, M.

2002-12-01

251

Export of dissolved organic carbon and nitrogen from drained and re-wetted bog sites in Lower Saxony (Germany)  

NASA Astrophysics Data System (ADS)

Today, nearly all peatlands in Germany are drained for agriculture, forestry and peat cutting. The export of dissolved organic carbon (C) and nitrogen (N) may be important for the overall C and N balances and affects downstream ecosystems. While drainage generally increases solute losses, there is nearly no C and N export data of raised bogs in Germany which can be used to evaluate both the impact of drainage associated with intensive land use and the re-wetting of peat cutting sites. In the "Ahlenmoor" (North-Western Germany), four sampling points were chosen. Three sampling points represent a deeply drained intensively used grassland at various scales ranging from a drainage pipe (DP, 0.08 ha) and a drainage ditch (DD, 6.8 ha) to a collector ditch (CD, 20 ha). The fourth sampling point (RW) is a former peat cutting site (23 ha) re-wetted 10 years ago. At this site, polder technique was used to establish water tables at the soil surface. Sampling and discharge measurements were conducted bi-weekly from June 2011 to June 2013. Water table levels were recorded with automatic pressure sensors, and rating curves between discharge and water levels were used to calculate continuous discharge values. Samples were analyzed for dissolved organic carbon (DOC), particulate organic carbon (POC), dissolved organic nitrogen (DON), ammonium (NH4+), nitrate (NO3-), sulphate (SO42-), pH, electric conductivity (EC) and specific UV absorbance (SUVA). The discharge did not vary strongly between the sampling points and was slightly lower in the second year. Concentrations of all measured solutes were higher at the intensive grassland (DP, DD and CD) than at the re-wetted site. Surprisingly, SUVA showed no difference between all sites, while the DOC to DON ratio was narrower at DP, DD and CD than at RW. This indicates an export of more degraded dissolved organic matter (DOM) from the drained area. At the grassland sites, no statistical differences were found between the three scales except for SO42-, NO3- and pH. Thus, the grassland shows rather homogenous export patterns over various spatial scales, and there seem to be no fast mineralization or degradation of the exported DOM during the initial stage of export. In total, average losses of DOC (457 kg ha-1 a-1) and POC (40 kg ha-1 a-1) from the drained area were nearly thrice as high as from the re-wetted site (124 and 73 kg ha-1 a-1). The total nitrogen losses were even more reduced by re-wetting and dominated at all sites by DON (19.1 kg ha-1 a-1 at the grassland sites, 3.9 kg ha-1 a-1 at the re-wetted site). NH4+ (drained: 5.2 kg ha-1 a-1, re-wetted: 0.8 kg ha-1 a-1) and NO3- (drained: 1.6 kg ha-1 a-1, re-wetted: not detectable) played a minor role. Overall, differences in the export could rather be explained by differences in solute concentration than in discharge.

Frank, Stefan; Tiemeyer, Bärbel; Freibauer, Annette

2014-05-01

252

Dissolution Rates and Weathering Products of Iron-Titanium Oxides: pH and Temperature Dependence  

Microsoft Academic Search

Experiments show that Fe-Ti oxides dissolve readily at low pH and temperature on short timescales. After dissolution in H2SO4, Fe-bearing sulfate minerals precipitate from the fluid. Dissolution rates and evaporite mineralogy will be discussed.

S. A. Arlauckas; S. M. McLennan

2005-01-01

253

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

254

Seasonal and regional variability in dissolved and particulate iron fluxes via glacial runoff along the West Greenland coast  

NASA Astrophysics Data System (ADS)

Subglacial weathering, due to biogeochemical and physical weathering processes, can affect the chemical evolution of subglacial waters and release dissolved and particulate iron via glacial runoff. Iron is a growth limiting nutrient and plays a critical role in the biogeochemical cycles of coastal and marine waters. More recently, dissolved and colloidal iron derived from subglacial sources have been considered an important contributor of Fe fluxes to the ocean; however, their dependency on lithology, grain size, and microbial activity is not well understood. This study characterizes the solute chemistry, in particular iron mineralogy and dissolved iron concentrations, released from beneath the Greenland Ice Sheet (GrIS), from two locations along the West Greenland coast, Thule (76°N, 68°W) and Kangerlussuaq (67°N, 50°W). We hypothesize that the subglacial lithology has a control on Fe fluxes from the GrIS to coastal and marine systems. The underlying bedrock in Thule is the Precambrian Dundas and Narssarssuk sedimentary formations which include sandstone, siltstone, and shale. The bedrock in Kangerlussuaq is dominated by Archean granodioritic gneiss and amphibolite within the Nagssugtoqidian Orogen. Supra and subglacial meltwater samples were collected directly in front of the Ice Sheet over an entire melt season in 2011 (North River, Thule) and 2012 (Akuliarusiarsuup Kuua River, Kangerlussuaq). In situ parameters such as temperature, pH, dissolved oxygen, and electrical conductivity were recorded in order to interpret meltwater chemistry. Dissolved Fe(II) and Fe(III) species were fixed immediately and analyzed within 24 hours after sampling in the field laboratory using a spectrophotometer and 10 cm cell. Total dissolved iron (FeT) of different size fractions (<0.22 and <0.05 ?m) of iron were determined back in the home laboratory using reaction cell ICP MS. Preliminary results demonstrate that subglacial meltwater of North River has average FeT concentrations of 200 nM and 10 nM in the <0.22 and <0.05 ?m size fraction, respectively, indicating that FeT in the <0.22 ?m fraction is mostly (95%) in form of colloidal iron. In comparison, data from Kangerlussuaq show an average FeT of 580 nM in the <0.22 ?m size fraction and 150 nM in the <0.05 ?m fraction. Suspended load in North River increased throughout the ablation period in concurrence with variation in discharge, from an average of 0.08 g/L in the early melt stages (June), 0.21 g/L during the high melt (July-August), and 0.15 g/L during the late melt (end of August-September). Initial estimates for the suspended load for subglacial flow in Kangerlussuaq are 0.30 g/L on average. The suspended load will be analyzed for iron by sequential extraction in order to characterize how iron partitions between oxide and (oxyhydr)oxide minerals in the sediment. This comprehensive study will allow us to identify biogeochemical processes involved in the mobilization of iron and to evaluate how increased melting of GrIS will affect Fe fluxes to coastal and marine environments.

Choquette, K.; Hagedorn, B.; Sletten, R. S.; Harrold, Z.; Liu, L.; Dieser, M.; Cameron, K. A.; Christner, B. C.; Junge, K.

2012-12-01

255

Electrical Conductivity.  

ERIC Educational Resources Information Center

Explains how electrical conductivity (EC) can be used to measure ion concentration in solutions. Describes instrumentation for the measurement, temperature dependence and EC, and the EC of common substances. (PR)

Hershey, David R.; Sand, Susan

1993-01-01

256

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

257

Adsorption of dissolved aluminum on sapphire-c and kaolinite: implications for points of zero charge of clay minerals  

PubMed Central

We have studied the impact of dissolved aluminum on interfacial properties of two aluminum bearing minerals, corundum and kaolinite. The effect of intentionally adding dissolved aluminum on electrokinetic potential of basal plane surfaces of sapphire was studied by streaming potential measurements as a function of pH and was complemented by a second harmonic generation (SHG) study at pH 6. The electrokinetic data show a similar trend as the SHG data, suggesting that the SHG electric field correlates to zeta-potential. A comparable study was carried out on kaolinite particles. In this case electrophoretic mobility was measured as a function of pH. In both systems the addition of dissolved aluminum caused significant changes in the charging behavior. The isoelectric point consistently shifted to higher pH values, the extent of the shift depending on the amount of aluminum present or added. The experimental results imply that published isoelectric points of clay minerals may have been affected by this phenomenon. The presence of dissolved aluminum in experimental studies may be caused by particular pre-treatment methods (such as washing in acids and subsequent adsorption of dissolved aluminum) or even simply by starting a series of measurements from extreme pH (causing dissolution), and subsequently varying the pH in the very same batch. This results in interactions of dissolved aluminum with the target surface. A possible interpretation of the experimental results could be that at low aluminum concentrations adatoms of aluminum (we will refer to adsorbed mineral constituents as adatoms) can form at the sapphire basal plane, which can be rather easily removed. Simultaneously, once the surface has been exposed to sufficiently high aluminum concentration, a visible change of the surface is seen by AFM which is attributed to a surface precipitate that cannot be removed under the conditions employed in the current study. In conclusion, whenever pre-treatment or the starting point of an experiment favor the dissolution of aluminum, dissolved Al may remain in the experimental system and interact with the target surfaces. The systems are then no longer pristine and points of zero charge or sorption data are those of aluminum-bearing systems.

2014-01-01

258

Studies of TPB dissolved in Toluene  

Microsoft Academic Search

Scintillation light in liquid argon calorimeters is produced at 128 nm. This must be shifted to the visible so that the light can be observed by phototubes. A traditional method for accomplishing this is to dissolve Tetraphenyl butadiene and plastic into toluene, and then use this mixture to coat surfaces. After the toluene evaporates, the TPB in the thin plastic

Ruel Jerry; Lindley Winslow; Janet Conrad

2010-01-01

259

Rapid dissolving polymer compositions and uses therefor  

Microsoft Academic Search

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

D. P. OMara; A. F. Hadermann; J. C. Trippe

1988-01-01

260

Method for dissolving delta-phase plutonium  

Microsoft Academic Search

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

Karraker

1992-01-01

261

Modeling Fish Growth in Low Dissolved Oxygen  

ERIC Educational Resources Information Center

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

Neilan, Rachael Miller

2013-01-01

262

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...

263

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

264

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

265

Coping with PH over the Long Term  

MedlinePLUS

... International PH News and Projects Let Me Breathe Music Video PATIENTS Patients Newly Diagnosed Request an Envelope ... International PH News and Projects Let Me Breathe Music Video Help spread PH awareness and share PH ...

266

Dissolved-solids budget of Lake Okeechobee, Florida, October 1964 to September 1974  

USGS Publications Warehouse

Lake Okeechobee is a major surface-water storage facility for south Florida. A dissolved-solids budget for Lake Okeechobee was computed for Oct. 1964 to Sept. 1974, a 10-year budget period. Calculations were based on records of daily discharge, daily specific conductance measurements, and regression equations relating dissolved-solids concentrations and specific conductance. The lake received more than 13 million acre-feet of rainfall during the budget period and lost more than 18 million acre-feet of water to evaporation. Lake Okeechobee received more than 20 million acre-feet of inflow and released almost 16 million acre-feet to distributaries. A water budget of 34.48 million acre-feet for the 10-year budget period was computed. Rainfall produced an input of 460,000 tons of dissolved solids to Lake Okeechobee. Inflow from tributaries and distributaries added 5.51 million tons of dissolved solids to the lake and outflow to distributaries removed 6.71 million tons. A dissolved-solids budget of 6.99 million tons for the 10-year budget period was computed. (Woodard-USGS)

Maddy, David V.

1978-01-01

267

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

268

The effect of the use of plastic sampling containers on laboratory measurements of dissolved oxygen  

Microsoft Academic Search

Dissolved oxygen (DO) concentrations are often used to define the water quality of a stream or reservoir. In the Tennessee Valley, there is a commonly held belief that water quality in general, and DO in particular, is declining in TVA reservoirs. In 1980, TVA conducted a study of DO trends in the tailraces of Tennessee River Dams and found a

Fehring

1990-01-01

269

DIEL DISSOLVED OXYGEN MONITORING OF THE SPOKANE RIVER DURING EXTREME LOW FLOW. KOOTENAI COUNTY, IDAHO, 1992  

EPA Science Inventory

Diel monitoring of dissolved oxygen and temperature was conducted on an impounded and free-flowing reach of the Spokane River, in north Idaho (17010303) on 2 occasions during an extreme low flow event in water year 1992. The objective was to document excursions from water qualit...

270

Dissolved organic carbon in forested and cutover drainage basins, Westland, New Zealand  

Microsoft Academic Search

Dissolved organic carbon (DOC) is an important component of water quality yet there are few studies of the effect of forest management on DOC and these have contradictory conclusions. Studies of DOC were conducted over 5 months at 2 sets of basins near Reefton. The Maimai set of 8 steep, well-drained basins had stream DOC concentrations ranging from 2 to

T. R. MOORE

271

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...

272

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...

273

Community-Level Effects of Excess Total Dissolved Solids Doses Using Model Streams  

EPA Science Inventory

Model stream chronic dosing studies (42 days) were conducted with four different total dissolved solids (TDS) recipes. The recipes differed in their relative dominance of major ions. One was made from sodium and calcium chloride salts only. Another was similar to the first, but a...

274

Transformation and characterisation of dissolved organic matter during the thermophilic aerobic biodegradation of faeces  

Microsoft Academic Search

We conducted a comparison of the characteristics of dissolved organic matter (DOM) taken from the bio-toilet and other sources. A characterisation of DOM was carried out to assess the stability of the compost generated during the thermophilic and aerobic biodegradation of faeces. In addition, levels of soluble microbial products generated in the bio-toilet composting reactor were compared with those taken

Hiroki Narita; Miguel Angel Lopez Zavala; Kaori Iwai; Ryusei Ito; Naoyuki Funamizu

2005-01-01

275

Quantitative and Qualitative Aspects of Dissolved Organic Carbon Leached from Senescent Plants in an Oligotrophic Wetland  

Microsoft Academic Search

We conducted a series of experiments whereby dissolved organic matter (DOM) was leached from various wetland and estuarine\\u000a plants, namely sawgrass (Cladium  jamaicense), spikerush (Eleocharis  cellulosa), red mangrove (Rhizophora  mangle), cattail (Typha  domingensis), periphyton (dry and wet mat), and a seagrass (turtle grass; Thalassia  testudinum). All are abundant in the Florida Coastal Everglades (FCE) except for cattail, but this species

Nagamitsu Maie; RUDOLF JAFFE ´; Toshikazu Miyoshi; Daniel L. Childers

2006-01-01

276

Updated determination of particulate and dissolved thorium-234  

NASA Astrophysics Data System (ADS)

The determination of particulate and dissolved 234Th is similar to the procedure of Anderson and Fleer [1982]. Samples are collected using 30 L Niskin bottles with Teflon- or epoxy-coated internal springs. On deck, the sample is pumped with a delrin impeller pump through a 0.45 ?m pore size 147-mm diameter Millipore filter and into a pre-rinsed 6 gallon plastic cubitainer held in a plastic milk crate. An in-line plastic water meter records volumes in gallons. The particulate sample filter is folded twice and stored in a polyethylene sample bag. To the ˜20 L filtered sample is added: 30 mL reagent grade 16 N HNO3; 500 mL 230Th tracer of ˜30 dpm mL-l and 5 mL 50 mg mL-l iron carrier previously cleaned by extraction into isopropyl ether from an 8 M HCl solution and back-extracted into 0.1 M HCl. The acidified sample is allowed to equilibrate for from one day to a maximum of several days. The sample is weighed on a Heathkit digital scale and the pH is adjusted to approximately 8 with about 40 mL 10 M NH4OH to precipitate iron hydroxide, which carries the thorium and uranium from the solution. The precipitate is allowed to settle for 12 to 24 hours. The supernate is drawn off, and the precipitate is spun down in a centrifuge tube to about an 8 mL volume. The precipitate is resuspended in distilled water and spun down again, then dissolved in three times its volume with 12 N HCl to make a 9 N HCl solution. A 1.5 cm×12 cm ion exchange column is filled with AG1×8 100-200 mesh resin and conditioned with 9 N HCl. The sample solution is run slowly through.

Fleer, Alan P.

277

Possible method for dissolved organic carbon speciation in forest soils  

NASA Astrophysics Data System (ADS)

Dissolved organic carbon (DOC) is a natural part of dissolved organic matter and it plays an important role in the biogeochemistry of soil processes. Low Molecular Mass Organic Acids (LMMOA) are an essential part of DOC. These acids play a key role in chemical processes that affect the entire soil environment. Knowing the amount of DOC and the speciation of LMMOA is required for realistic equilibrium modelling of soil chemical processes and transport mechanisms. There have been a number of proposed methods for the quantitative analysis of DOC and for speciation of LMMOA. The first aim of this contribution is to introduce and test a modified spectroscopic method for the determination of water-extractable organic carbon (WEOC) from forest soils. In general this method is based on the oxidization of WEOC by chromium-sulphuric acid. The presented method can be used as an economical alternative to the classical, more financially demanding elemental analysis. However, the main aim is to test the reliability of the method for LMMOA speciation. Ion exchange chromatography (IC) with hydroxide elution has proven to be a useful tool for the determination of LMMOA in many different water-based samples. However, the influence of multivalent cations (often present in environmental samples) on IC results has not yet been sufficiently studied. In order to assess the influence of Al, Fe, Mn, Mg and Ca on the amount of LMMOA determined by IC, an extensive set of model solutions was prepared and immediately analysed by means of IC. Moreover, the influence of pH on determined amounts of LMMOA in model solutions and representative soil aqueous extracts was investigated. These experimental results were compared to expected values and also to results provided by the chemical equilibrium model - PHREEQC. Based on the above listed research, some modifications to the common IC method for LMMOA speciation are presented.

Drabek, O.; Tejnecký, V.; Ash, C.; Hubova, P.; Boruvka, L.

2013-12-01

278

Conduction Activities  

NSDL National Science Digital Library

This page presents activities related to Conduction from the Science & Engineering in the Lives of Students project. Activities include Chemical Reactions in Construction, Everyday Heat Transfer, Heat Resistant Glass, Hot Cup, Speed Melting, and Wall R Value. Each activity includes a detailed description, list of the materials needed, science concepts covered, and reflection questions.

2013-07-10

279

Mobilization of cadmium by dissolved organic matter in the rhizosphere of hyperaccumulator Sedum alfredii.  

PubMed

Pot experiments were conducted to investigate the role of dissolved organic matter (DOM) in the Cd speciation in the rhizosphere of hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) of Sedum alfredii and its effects on Cd mobility. After growing HE S. alfredii, the rhizosphere soil solution pH of heavily polluted soil (HPS) and slightly polluted soil (SPS) was reduced by 0.49 and 0.40 units, respectively, due to enhanced DOC derived from root exudation. The total Cd concentration in soil solution decreased significantly but the decrease accounted for less than 1% of the total Cd uptake in the shoots of HE S. alfredii. Visual MINTEQ speciation predicted that Cd-DOM complexes were the dominant Cd species in soil solutions after the growth of S. alfredii for both soils, followed by the free metal Cd(2+) species. However, Cd-DOM complexes fraction in the rhizosphere soil solution of HE S. alfredii (89.1% and 74.6% for HPS and SPS, respectively) were much greater than NHE S. alfredii (82.8% and 64.7% for HPS and SPS, respectively). Resin equilibration experiment results indicated that DOM from the rhizosphere (R-DOM) of both ecotypes of S. alfredii had the ability to form complexes with Cd, whereas the degree of complexation was significantly higher for HE-R-DOM (79-89%) than NHE-R-DOM (63-74%) in the undiluted sample. The addition of HE-R-DOM significantly (P<0.05) increased the solubility of four Cd minerals while NHE-R-DOM was not as effective at the same concentration. It was concluded that DOM in the rhizosphere of hyperaccumulating ecotype of S. alfredii could significantly increase Cd mobility through the formation of soluble DOM-metal complexes. PMID:23466273

Li, Tingqiang; Liang, Chengfeng; Han, Xuan; Yang, Xiaoe

2013-05-01

280

The impact of blocking natural peat pipes on dissolved organic carbon  

NASA Astrophysics Data System (ADS)

Natural pipes transport water and aquatic carbon through peatlands. In 2010 pipes were blocked on Keighley Moor in northern England as part of a peatland restoration programme aimed at reducing water discolouration and dissolved organic carbon (DOC) release into stream waters used for potable water supply. Blocked and open pipes were monitored for water quality between June 2012 and October 2013. The DOC, water colour, conductivity and pH were not significantly different between open pipes and water flowing from areas where pipe blocking had occurred. A before-after control-treatment experiment was devised at another peatland site - Moor House World Biosphere Reserve in northern England. Here, the areas around six pipes were monitored for water quality, discharge, water tables, and overland flow. Four of the pipes were then blocked while monitoring continued on all six pipes. The Moor House investigation suggests that the overall effects of blocking on water colour and DOC in the following summer were small (5 % decrease in absorbance at 254 nm but 7 % increase in absorbance at 400 nm, and 2 % decrease in DOC relative to open pipe controls). There were large (40-117 %) local increases in colour and DOC in overland flow but decreases in soil water (7-10 %) relative to the areas around open pipes. Water tables rose by a few cm upslope of the pipe dams. However, downslope, water tables fell by a similar amount, thereby potentially counteracting any water quality benefits resulting from shallower water tables upslope. Pipe blocking is expensive, and our results to date suggest that any water quality benefits are outweighed by the cost of blocking. However, in highly-degraded sites where pipes are rapidly expanding to form gullies, pipe blocking may be useful as part of a larger suite of measures to help reduce peat erosion.

Holden, Joseph; Baird, Andy; Parry, Lauren; Chapman, Pippa; Palmer, Sheila; Wallage, Zoe; Wynne, Hannah

2014-05-01

281

[Geochemical distribution of dissolved bismuth in the Yellow Sea and East China Sea].  

PubMed

Occurrence level, geochemical distribution of dissolved bismuth and its coupling relationship to eco-environment were investigated in the Yellow Sea and East China Sea to explore the source and influencing factors. The results showed that the concentration of dissolved bismuth was within the range of 0-0. 029 microg x L(-1) at the surface and 0.001-0.189 microg x L(-1) at the bottom, with the averages of 0.008 and 0.016 microg x L(-1), respectively. Horizontally, low value of dissolved bismuth exhibited the bidirectional extension feature, indicating that it could trace the path of Changjiang Diluted Water. High value of dissolved bismuth was observed where the Subei Costal Current and Yellow Sea Warm Current flowed and the Changjiang Diluted Water and Zhejiang-Fujian Coastal Current met, suggesting that it was controlled by the cycle of current system. Vertically, the coastal water was fully mixed by water convection and eddy mixing, and was divided from the stratified water by strong tidal front, which blocked the transport of dissolved bismuth to the open sea. Thus, the concentration in front area was significantly higher than that in the open sea. Diurnal variation of dissolved bismuth was related to the hydrodynamic conditions (tide, suspension and thermocline) instead of the environmental factors (temperature and salinity). Positive relationship to SPM (suspended particulate matter) clarified that bismuth was prone to release from solid phase to liquid phase. Furthermore, conditions with temperature ranging 22-27 degrees C, salinity ranging 28-31 and pH ranging 7.9-8.1 were shown to be optimal for the release process. PMID:24720192

Wu, Xiao-Dan; Song, Jin-Ming; Wu, Bin; Li, Xue-Gang

2014-01-01

282

Influence of pH on microbial hydrogen metabolism in diverse sedimentary ecosystems.  

PubMed Central

Hydrogen transformation kinetic parameters were measured in sediments from anaerobic systems covering a wide range of environmental pH values to assess the influence of pH on hydrogen metabolism. The concentrations of dissolved hydrogen were measured and hydrogen transformation kinetics of the sediments were monitored in the laboratory by monitoring hydrogen consumption progress curves. The hydrogen turnover rate constants (kt) decreased directly as a function of decreasing sediment pH, and the maximum hydrogen uptake velocities (Vmax) varied as a function of pH within each of the trophic states. Conversely, the half-saturation concentrations (Km) were independent of pH. The steady-state hydrogen concentrations were at least 2 orders of magnitude lower than the half-saturation constants for hydrogen uptake. Dissolved hydrogen concentrations were at least fivefold higher in sediments from eutrophic systems than from oligotrophic and dystrophic systems. The rates of hydrogen production determined from the assumption of steady state decreased with sediment pH. These data indicate that progressively lower pH values inhibit microbial hydrogen-producing and -consuming processes within sedimentary ecosystems.

Goodwin, S; Conrad, R; Zeikus, J G

1988-01-01

283

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

284

Quantitative evaluation of noncovalent interactions between glyphosate and dissolved humic substances by NMR spectroscopy.  

PubMed

Interactions of glyphosate (N-phosphonomethylglycine) herbicide (GLY) with soluble fulvic acids (FAs) and humic acids (HAs) at pH 5.2 and 7 were studied by (1)H and (31)P NMR spectroscopy. Increasing concentrations of soluble humic matter determined broadening and chemical shift drifts of proton and phosphorus GLY signals, thereby indicating the occurrence of weak interactions between GLY and humic superstructures. Binding was larger for FAs and pH 5.2 than for HAs and pH 7, thus suggesting formation of hydrogen bonds between GLY carboxyl and phosphonate groups and protonated oxygen functions in humic matter. Changes in relaxation and correlation times of (1)H and (31)P signals and saturation transfer difference NMR experiments confirmed the noncovalent nature of GLY-humic interactions. Diffusion-ordered NMR spectra allowed calculation of the glyphosate fraction bound to humic superstructures and association constants (K(a)) and Gibbs free energies of transfer for GLY-humic complex formation at both pH values. These values showed that noncovalent interactions occurred most effectively with FAs and at pH 5.2. Our findings indicated that glyphosate may spontaneously and significantly bind to soluble humic matter by noncovalent interactions at slightly acidic pH and, thus, potentially pollute natural water bodies by moving through soil profiles in complexes with dissolved humus. PMID:22591574

Mazzei, Pierluigi; Piccolo, Alessandro

2012-06-01

285

The pH-dependence of organofluorine binding domain preference in dissolved humic acid.  

PubMed

In this study we explore the relationship between solution pH and the distribution of the binding interactions at different domains of a dissolved humic acid (HA) for three xenobiotics: pentafluoroaniline (PFA), pentafluorophenol (PFP), and hexafluorobenzene (HFB). The components of HA where xenobiotic interactions occur are identified using the (1)H{(19)F} Reverse Heteronuclear Saturation Transfer Difference (RHSTD) Nuclear Magnetic Resonance (NMR) spectroscopy experiment. At low pH, PFA and PFP interact preferentially with aromatic components of HA. Increasing pH reduces this preference. Conversely, HFB interacts with all components of HA equally, across the entire pH range. The possible roles of both aromatic-specific interactions and conformational changes of HA behind these observations are explored. It is shown that T-oriented ?-? interactions at ?-electron accepting HA structures are slightly stronger for PFA and PFP than for HFB. Using DOSY NMR it is shown that the pH-dependence of the interactions is correlated with changes in the conformation of the carbohydrate components of HA rather than with the aromatic components. It is argued that the observed preference for aromatic HA is caused by restricted access to the non-aromatic components of HA at low pH. These HA components form tightly bound hydrophobic domains due to strong inter- and intra-molecular hydrogen bonds. At high pH, these structures open up, making them more available for interactions with polar compounds. PMID:22863060

Longstaffe, James G; Courtier-Murias, Denis; Simpson, André J

2013-01-01

286

Arsenic adsorption and oxidation at manganite surfaces. 1. Method for simultaneous determination of adsorbed and dissolved arsenic species  

SciTech Connect

Arsenic occurs in the +III oxidation state as a metastable species in oxic waters. Under oxide conditions, As(III) is both more mobile in natural waters and less efficiently removed by water treatment processes than As(V). Other oxidants, however, can react with As(III) more rapidly than oxygen. The oxidation of As(III) by manganite occurs on the time scale of hours. Here, a method is introduced for the rapid determination of the total and dissolved concentrations of arsenic species in this heterogeneous system; absorbed arsenic concentrations are calculated by difference. The oxidation reaction is quenched by the addition of ascorbic acid to effect the reductive dissolution of manganite and concomitant release of adsorbed As(III) and As(V) into solution. Once in solution, As(III) and As(V) are separated using anion-exchange chromatography. Comparison of dissolved and total concentrations of As(III) and As(V) clearly illustrates that the overall conversion rate of As(III) to As(V) in this system would be overpredicted based solely on dissolved As(III) concentrations and underpredicted based solely on dissolved As(V) concentrations. The overall conversion of As(III) to As(V) was more rapid at pH 4 than at pH 6.3 and was unaffected by the presence of boric acid at 95 {micro}M or 3 mM. However, the presence of 200 {micro}M phosphate (at pH 4) decreased the overall rate of conversion of As(III) to As(V). Comparison of total and dissolved As(III) concentrations during the reaction time course demonstrates that the effects of pH and phosphate on adsorbed As(III) concentrations are generally consistent with these kinetic observations.

Chiu, V.Q.; Hering, J.G.

2000-05-15

287

Elementary PhUn Fair - PhUn Week Poster Session EB 2012  

NSDL National Science Digital Library

Approximately 40 high school students, enrolled in the Clinton High School Human Anatomy & Physiology course, organized and hosted a community PhUn Fair. During a week early in the semester, students researched various human physiological systems. The following week, students developed and planned learning stations based on their research. Students received input and feedback from a visiting physiologist, their instructor, and their peers. The culminating event was the PhUn Fair, during which more than 100 second-graders spent an afternoon rotating through eight active learning stations taught by the high school students. All learning stations introduced a different physiological concept through inquiry-based activities. The PhUn Fair concluded with a question and answer period with the visiting physiologist. While the high school students conducted the research and planning during the two weeks prior to the PhUn Fair, initial organization was conducted by the authors during the APS Frontiers in Physiology Fellowship summer research experience. P. Schork was supported by 2011 The American Physiological Society Frontiers in Physiology Fellowship.

Pauline Schork (Clinton High School)

2012-04-22

288

Copper binding by dissolved organic matter. II. Variation in type and source of organic matter  

SciTech Connect

Copper binding properties of several fulvic acid (FA) and whole water samples are compared by means of an empirical model that was calibrated using Suwannee River FA. Within the calibration limits of the model (pH 5.0-8.5, total Cu concentration 0.1-100 ..mu..M, ionic strength 0.1, and dissolved organic carbon, DOC, 1-10 mg C/1), pCu in solutions of a variety of FA samples are predicted with < 0.2 pCu units root mean square error (RMSE). Within the calibration limits, many whole water sample pCu's are predicted with < 0.3 pCu units RMSE if only one-half of the dissolved organic carbon is assumed to bind Cu. Agreement between prediction and experiment at lower ionic strength is not as good. Variations in Cu binding among different sources of dissolved organic matter appear to be much smaller than those due to chemical factors such as pH and ionic strength.

Cabaniss, S.E.; Shuman, M.S.

1988-01-01

289

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

290

Dissolving polymer microneedle patches for influenza vaccination.  

PubMed

Influenza prophylaxis would benefit from a vaccination method enabling simplified logistics and improved immunogenicity without the dangers posed by hypodermic needles. Here we introduce dissolving microneedle patches for influenza vaccination using a simple patch-based system that targets delivery to skin's antigen-presenting cells. Microneedles were fabricated using a biocompatible polymer encapsulating inactivated influenza virus vaccine for insertion and dissolution in the skin within minutes. Microneedle vaccination generated robust antibody and cellular immune responses in mice that provided complete protection against lethal challenge. Compared to conventional intramuscular injection, microneedle vaccination resulted in more efficient lung virus clearance and enhanced cellular recall responses after challenge. These results suggest that dissolving microneedle patches can provide a new technology for simpler and safer vaccination with improved immunogenicity that could facilitate increased vaccination coverage. PMID:20639891

Sullivan, Sean P; Koutsonanos, Dimitrios G; Del Pilar Martin, Maria; Lee, Jeong Woo; Zarnitsyn, Vladimir; Choi, Seong-O; Murthy, Niren; Compans, Richard W; Skountzou, Ioanna; Prausnitz, Mark R

2010-08-01

291

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

292

Measurements of the dissolved inorganic carbon system and associated biogeochemical parameters in the Canadian Arctic, 1974-2009  

NASA Astrophysics Data System (ADS)

We have assembled and conducted primary quality control on previously publicly unavailable water column measurements of the dissolved inorganic carbon system and associated biogeochemical parameters (oxygen, nutrients, etc.) made on 26 cruises in the subarctic and Arctic regions dating back to 1974. The measurements are primarily from the western side of the Canadian Arctic, but also include data that cover an area ranging from the North Pacific to the Gulf of St. Lawrence. The data were subjected to primary quality control (QC) to identify outliers and obvious errors. This data set incorporates over four thousand individual measurements of total inorganic carbon (TIC), alkalinity, and pH from the Canadian Arctic over a period of more than 30 years and provides an opportunity to increase our understanding of temporal changes in the inorganic carbon system in northern waters and the Arctic Ocean. The data set is available for download on the CDIAC (Carbon Dioxide Information Analysis Center) website: http://cdiac.ornl.gov/ftp/oceans/IOS_Arctic_Database/ (doi:10.3334/CDIAC/OTG.IOS_ARCT_CARBN).

Giesbrecht, K. E.; Miller, L. A.; Davelaar, M.; Zimmermann, S.; Carmack, E.; Johnson, W. K.; Macdonald, R. W.; McLaughlin, F.; Mucci, A.; Williams, W. J.; Wong, C. S.; Yamamoto-Kawai, M.

2014-03-01

293

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

2012-01-01

294

Investigation of organic carbon transformation in soils of dominant dissolved organic carbon source zones  

NASA Astrophysics Data System (ADS)

Over the past 20 years both a decrease in soil organic matter (SOM) and an increase in the dissolved organic carbon (DOC) concentrations in surface water bodies, including drinking water reservoirs, have been recorded in the northern hemisphere. This development has severe consequences for soil fertility and for drinking water purification. As both processes occur simultaneously, we assume that microbial SOM degradation, which transforms SOM into CO2 and DOC, is a possible source of the additional DOC in the surface water. In addition we speculate that both processes are initially triggered by physical mechanisms, resulting in a modification of the organic matter solubility equilibria and thus in higher SOM availability and DOC mobilization. The general hypothesis of the study is therefore that SOM loss and DOC increase are combined consequences of enhanced microbial degradation of SOM and that this is a result of climate variations and global change, e.g. the increase of the temperature, the alteration of the water regime (i.e. increase of the frequency of drying and rewetting cycles and a higher number of heavy rain events), but also the decrease of the atmospheric acid deposition resulting in an increase of soil pH values. The general goal of the study is the identification of the dominant processes and controlling factors involved in soil microbial carbon turnover and mobilization of DOC in soils from catchment areas that contribute DOC to the receiving waters and the downstream Rappbode reservoir, which showed a pronounced increase in DOC concentration in recent years. This reservoir is the source of drinking water for about one million people in northern Germany. Preliminary screening experiments, consisting of 65-day soil batch incubation experiments, have been conducted in order to select the parameters (and the parameter ranges) of relevance for further in-depth experiments. During the experiments, different soil systems were exposed to different temperatures, pH, and water contents. The extractable DOC and the mineralization products (CO2) were monitored in order to obtain the mass balances of SOM turnover for the different systems. In addition, for each system the aromatic character of the DOC extracted was evaluated by analyzing the specific UV absorbance (SUVA) at 254 nm. Results from the preliminary experiments will be presented. All the environmental drivers which were studied influenced both organic matter degradation and DOC mobilization, which suggests a positive correlation between the two processes. The results of the screening experiments will be the basis for the experimental design of further experiments studying the mechanisms of these observed changes in detail.

Pissarello, Anna; Miltner, Anja; Oosterwoud, Marieke; Fleckenstein, Jan; Kästner, Matthias

2014-05-01

295

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

296

Method for dissolving delta-phase plutonium  

SciTech Connect

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

Karraker, D.G.

1992-08-04

297

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

298

Method of dissolving organic filter cake  

Microsoft Academic Search

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

K. H. Hollenbeck; L. R. Norman

1989-01-01

299

Method for dissolving delta-phase plutonium  

Microsoft Academic Search

A process for dissolving plutonium, and in particular, delta-phase plutonium. The process includes heating a mixture of nitric acid, hydroxylammonium nitrate and potassium fluoride (HAN) to a temperature between 40 and 70 C, then immersing the metal in the mixture. Preferably, the nitric acid has a concentration of not ore than 2M, the HAN approximately 0.66M, and the potassium fluoride

Karraker

1992-01-01

300

Method for dissolving delta-phase plutonium  

Microsoft Academic Search

A process for dissolving plutonium, and in particular, delta-phase plutonium. The process includes heating a mixture of nitric acid, hydroxylammonium nitrate (HAN) and potassium fluoride to a temperature between 40.degree. and 70.degree. C., then immersing the metal in the mixture. Preferably, the nitric acid has a concentration of not more than 2M, the HAN approximately 0.66M, and the potassium fluoride

Karraker; David G

1992-01-01

301

An Introduction to Chemistry: Dissolving Sodium Chloride  

NSDL National Science Digital Library

What happens at the molecular level when a compound dissolves in water? This interactive animation explores how negative and positive ions in sodium chloride (table salt) collide with water molecules and become separated from each other to become a solution. The model does an effective job of depicting how the water molecules disrupt the attraction between the positive sodium ions and the negative chloride ions, and then become stabilized by attractions to the atoms in the water molecule.

Bishop, Mark

2011-05-02

302

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

303

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

NASA Astrophysics Data System (ADS)

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

Zhang, Litao; Wang, Jianqiu

2014-03-01

304

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

305

Dissolved organic nitrogen measurement using dialysis pretreatment.  

PubMed

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

Lee, Wontae; Westerhoff, Paul

2005-02-01

306

Investigating Students' Understanding of the Dissolving Process  

NASA Astrophysics Data System (ADS)

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 symbolic-level questions were based on balanced equations, and the particulate-level questions used multiple-choice questions involving dynamic animations or static pictures. This paper analyzes students' responses to these questions to look for associations among four variables—Answer (the correct answer and three misconceptions), Representation (symbolic or particulate question), Visualization (static or animated pictures), and Representation Order (symbolic questions before or after the particulate questions). The results indicate that the correct answer and the acid-base misconception were more popular than the ion-pair or subscript error misconceptions, the ion-pair misconception was more popular for the particulate questions than the symbolic questions, and that participants were more likely to select the correct answer when viewing static particulate questions compared to animated particulate questions, especially if the particulate questions are seen first. These results suggest that the animated motion of dissolving these compounds in water may be distracting for students.

Naah, Basil M.; Sanger, Michael J.

2013-04-01

307

Philip Prorok, PhD  

Cancer.gov

Philip Prorok, PhD, mirum est notare quam littera gothica, quam nunc putamus parum claram, anteposuerit litterarum formas humanitatis per seacula quarta decima et quinta decima. Eodem modo typi, qui nunc nobis videntur parum clari, fiant sollemnes in futurum.

308

SUSPENDED AND DISSOLVED SOLIDS EFFECTS ON FRESHWATER BIOTA: A REVIEW  

EPA Science Inventory

It is widely recognized that suspended and dissolved solids in lakes, rivers, streams, and reservoirs affect water quality. In this report the research needs appropriate to setting freshwater quality criteria or standards for suspended solids (not including bedload) and dissolved...

309

Analytical Method for Dissolved-Organic Carbon Fractionation.  

National Technical Information Service (NTIS)

A standard procedure for analytical-scale dissolved organic carbon fractionation is presented, whereby dissolved organic carbon in water is first fractionated by a nonionic macroreticular resin into acid, base, and neutral hydrophobic organic solute fract...

J. A. Leenheer E. W. D. Huffman

1979-01-01

310

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

311

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

312

Diel behavior of iron and other heavy metals in a mountain stream with acidic to neutral pH: Fisher Creek, Montana, USA  

USGS Publications Warehouse

Three simultaneous 24-h samplings at three sites over a downstream pH gradient were conducted to examine diel fluctuations in heavy metal concentrations in Fisher Creek, a small mountain stream draining abandoned mine lands in Montana. Average pH values at the upstream (F1), middle (F2), and downstream (F3) monitoring stations were 3.31, 5.46, and 6.80, respectively. The downstream increase in pH resulted in precipitation of hydrous ferric oxide (HFO) and hydrous aluminum oxide (HAO) on the streambed. At F1 and F2, Fe showed strong diel cycles in dissolved concentration and Fe(II)/Fe(III) ratio; these cycles were attributed to daytime photoreduction of Fe(III) to Fe(II), reoxidation of Fe(II) to Fe(III), and temperature-dependent hydrolysis and precipitation of HFO. At the near-neutral downstream station, no evidence of Fe(III) photoreduction was observed, and suspended particles of HFO dominated the total Fe load. HFO precipitation rates between F2 and F3 were highest in the afternoon, due in part to reoxidation of a midday pulse of Fe2+ formed by photoreduction in the upper, acidic portions of the stream. Dissolved concentrations of Fe(II) and Cu decreased tenfold and 2.4-fold, respectively, during the day at F3. These changes were attributed to sorption onto fresh HFO surfaces. Results of surface complexation modeling showed good agreement between observed and predicted Cu concentrations at F3, but only when adsorption enthalpies were added to the thermodynamic database to take into account diel temperature variations. The field and modeling results illustrate that the degree to which trace metals adsorb onto actively forming HFO is strongly temperature dependent. This study is an example of how diel Fe cycles caused by redox and hydrolysis reactions can induce a diel cycle in a trace metal of toxicological importance in downstream waters. Copyright ?? 2005 Elsevier Ltd.

Gammons, C. H.; Nimick, D. A.; Parker, S. R.; Cleasby, T. E.; McCleskey, R. B.

2005-01-01

313

Conductivity Probe  

NASA Technical Reports Server (NTRS)

The Thermal and Electrical Conductivity Probe (TECP) for NASA's Phoenix Mars Lander took measurements in Martian soil and in the air.

The needles on the end of the instrument were inserted into the Martian soil, allowing TECP to measure the propagation of both thermal and electrical energy. TECP also measured the humidity in the surrounding air.

The needles on the probe are 15 millimeters (0.6 inch) long.

The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

2008-01-01

314

Photochemistry of Dissolved Organic Matter in Arctic Surface Waters  

NASA Astrophysics Data System (ADS)

It has been shown that persistent organic pollutants (POPs), transported to the Arctic by long-range processes, can potentially contaminate Arctic surface waters and affect both local ecosystems and human health. Once deposited, the behavior of these pollutants is poorly understood; particularly the processes that govern their lifetime and concentrations within the water column. Here, we discuss the photochemical degradation of several halogenated organic pollutants (e.g., lindane, hexachlorobenzene) as mediated by natural dissolved organic matter (DOM). These experiments were conducted both in a controlled laboratory setting using an artificial sunlight simulator, as well as in situ in Alaskan surface waters near Toolik Lake. Our findings to date show high variability in the photodegradation rates of the target POPs and can be correlated to both their structure and the type of DOM present.

Grannas, A. M.; Chin, Y.; Miller, P. L.

2003-12-01

315

Chapter A6. Section 6.3. Specific Electrical Conductance  

USGS Publications Warehouse

Electrical conductance is a measure of the capacity of a substance to conduct an electrical current. The specific electrical conductance (conductivity) of water is a function of the types and quantities of dissolved substances it contains, normalized to a unit length and unit cross section at a specified temperature. This section of the National Field Manual (NFM) describes U.S. Geological Survey (USGS) guidance and protocols for measurement of conductivity in ground and surface waters.

Radtke, Dean B.; Davis, Jerri V.; Wilde, Franceska D.

2005-01-01

316

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

NASA Technical Reports Server (NTRS)

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

Ganoe, Rene; DeYoung, Russell J.

2013-01-01

317

Dissolved sulfide-catalyzed precipitation of disordered dolomite: Implications for the formation mechanism of sedimentary dolomite  

NASA Astrophysics Data System (ADS)

Dolomite is a common mineral in the rock record. However, the rarity of modern dolomite and the notorious difficulty in synthesizing dolomite abiotically under normal Earth-surface conditions result in the long-standing "dolomite problem" in sedimentary geology. Some modern dolomites are associated with sediments where microbial sulfate reduction is active; however, the role of sulfate-reducing bacteria in dolomite formation is still under debate. In this study, we tested the effect of dissolved sulfide on the precipitation of Ca-Mg carbonates, which has been never explored before although dissolved sulfide is one of the major products of microbial sulfate reduction. Our results demonstrated that dissolved sulfide with a concentration of as low as several millimoles can enhance the Mg2+ incorporation into the calcitic structure, and promote the crystallization of high magnesian calcite and disordered dolomite. We also conducted seeded precipitation in experimental solutions containing dissolved sulfide, which showed that calcite seeds can inhibit the precipitation of aragonite and monohydrocalcite (CaCO3·H2O), and induce more Mg2+ incorporation. We propose that accumulated dissolved sulfide in pore waters in organic-rich sediments may trigger the precipitation of disordered dolomite which can be considered as a precursor of some sedimentary dolomite. Our adsorption experiments revealed a strong adsorption of dissolved sulfide onto calcite faces. We suggest that adsorbed dissolved sulfide can lower the energy barrier to the dehydration of Mg2+-water complexes on the growing carbonate surfaces. This study sheds new light on understanding the role of sulfate-reducing bacteria in dolomite formation and the formation mechanism of sedimentary dolomite.

Zhang, Fangfu; Xu, Huifang; Konishi, Hiromi; Kemp, Joshua M.; Roden, Eric E.; Shen, Zhizhang

2012-11-01

318

Benthic flux of dissolved nickel into the water column of south San Francisco Bay  

USGS Publications Warehouse

Field and laboratory studies were conducted between April, 1998 and May, 1999 to provide the first direct measurements of the benthic flux of dissolved (0.2-micron filtered) nickel between the bottom sediment and water column at three sites in the southern component of San Francisco Bay (South Bay), California. Dissolved nickel and predominant ligands (represented by dissolved organic carbon, and sulfides) were the solutes of primary interest, although a variety of ancillary measurements were also performed to provide a framework for interpretation. Results described herein integrate information needs identified by the State Water Resources Control Board and local stakeholders with fundamental research associated with the U.S. Geological Survey Toxic Substances Hydrology Program. Dissolved-Ni concentrations in the bottom water over the three sampling dates ranged from 34 to 43 nanomoles per liter. Dissolved-macronutrient concentrations in the bottom water were consistently higher (frequently by orders of magnitude) than surface-water determinations reported for similar times and locations (Regional Monitoring Program, 2001). This is consistent with measured positive benthic fluxes for the macronutrients. Benthic-flux estimates for dissolved nickel from core-incubations, when areally averaged over the South Bay, were significant (that is, of equivalent or greater order of magnitude) relative to previously reported freshwater point and non-point sources. This observation is consistent with previous determinations for other metals, and with the potential remobilization of sediment-associated metals that have been ubiquitously distributed in the South Bay. Similar to dissolved-nickel results, benthic flux of macronutrients was also consistently significant relative to surface-water inputs. These results add to a growing body of knowledge that strongly suggests a need to consider contaminant transport across the sediment-water interface when establishing future management strategies for the watershed.

Topping, B. R.; Kuwabara, J. S.; Parchaso, Francis; Hager, S. W.; Arnsberg, A. J.; Murphy, Fred

2001-01-01

319

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

320

Detecting oil dissolved gases using carbon nanotubes sensor  

Microsoft Academic Search

The detection and analysis of dissolved gases in oil is an important means to determine the early latent faults of oil-immersed power transformer. A dissolved gases in oil detection method is presented based on carbon nanotubes sensor. A kind of MWNTs (Multi-wall carbon nanotubes) gas sensor modified by mixed acid was developed based on printed circuit board to detect dissolved

Tao Chang; Xiaoxing Zhang; Wangting Liu; Caixin Sun

2010-01-01

321

The surface chemistry of dissolving labradorite feldspar  

SciTech Connect

Elastic recoil detection (ERD) analysis was used in conjunction with Rutherford backscattering (RBS) analysis to determine depth profiles of hydrogen, silicon, aluminum and calcium in labradorite crystals reacted under various pH conditions. The inventory of hydrogen in the mineral is strongly affected by solution pH. Hydrogen extensively infiltrates the mineral during reaction for 264 hours with solutions in the pH range 1-3. Infiltration is accompanied by extensive removal of sodium, calcium and aluminum from the mineral. This incongruent reaction proceeds to several hundreds of angstroms of depth and produces a silicon-rich surface which is amorphous to electron diffraction. The amount of hydrogen in the reacted layer is much less than is predicted from knowledge of the quantity of cations leached from the feldspar. These low inventories of hydrogen suggest that hydrogen-bearing groups in the reacted layer repolymermize subsequent to ion exchange and depolymerization reactions. This repolymerization eliminates hydrogen from the layer. At higher pH conditions (pH > 5), hydrogen inventories in the crystals decrease with time relative to an unreacted reference crystal. Hydrogen does not infiltrate beyond the first few unit cells of feldspar. Thus, dissolution in slightly acid, near-neutral, and basic solutions proceeds at the immediate surface of the feldspar. Within the limit of the RBS technique, there is no evidence for incongruent dissolution at these conditions.

Casey, W.H.; Westrich, H.R.; Arnold, G.W. (Sandia National Laboratories, Albuquerque, NM (USA)); Banfield, J.F. (Johns Hopkins Univ., Baltimore, MD (USA))

1989-04-01

322

Fast Dissolving Tablets of Fexofenadine HCl by Effervescent Method  

PubMed Central

In the present work, fast dissolving tablets of fexofenadine HCl were prepared by effervescent method with a view to enhance patient compliance. Three super-disintegrants viz., crospovidone, croscarmellose sodium and sodium starch glycolate along with sodium bicarbonate and anhydrous citric acid in different ratios were used and directly compressible mannitol (Pearlitol SD 200) to enhance mouth feel. The prepared batches of tablets were evaluated for hardness, friability, drug content uniformity and in vitro dispersion time. Based on the in vitro dispersion time (approximately 20 s), three formulations were tested for in vitro drug release pattern in pH 6.8 phosphate buffer, short-term stability at 40°/75% RH for 3 mo and drug-excipient interaction (IR spectroscopy). Among the three promising formulations, the formulation ECP3 containing 8% w/w of crospovidone and mixture of 24% w/w sodium bicarbonate 18% w/w of anhydrous citric acid emerged as the best (t50% 4 min) based on the in vitro drug release characteristics compared to conventional commercial tablet formulation (t50% 15 min). Short-term stability studies on the formulations indicated that there are no significant changes in drug content and in vitro dispersion time (P<0.05).

Nagendrakumar, D.; Raju, S. A.; Shirsand, S. B.; Para, M. S.; Rampure, M. V.

2009-01-01

323

Fast Dissolving Tablets of Fexofenadine HCl by Effervescent Method.  

PubMed

In the present work, fast dissolving tablets of fexofenadine HCl were prepared by effervescent method with a view to enhance patient compliance. Three super-disintegrants viz., crospovidone, croscarmellose sodium and sodium starch glycolate along with sodium bicarbonate and anhydrous citric acid in different ratios were used and directly compressible mannitol (Pearlitol SD 200) to enhance mouth feel. The prepared batches of tablets were evaluated for hardness, friability, drug content uniformity and in vitro dispersion time. Based on the in vitro dispersion time (approximately 20 s), three formulations were tested for in vitro drug release pattern in pH 6.8 phosphate buffer, short-term stability at 40 degrees /75% RH for 3 mo and drug-excipient interaction (IR spectroscopy). Among the three promising formulations, the formulation ECP(3) containing 8% w/w of crospovidone and mixture of 24% w/w sodium bicarbonate 18% w/w of anhydrous citric acid emerged as the best (t(50%) 4 min) based on the in vitro drug release characteristics compared to conventional commercial tablet formulation (t(50%) 15 min). Short-term stability studies on the formulations indicated that there are no significant changes in drug content and in vitro dispersion time (P<0.05). PMID:20336204

Nagendrakumar, D; Raju, S A; Shirsand, S B; Para, M S; Rampure, M V

2009-03-01

324

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

2011-04-01

325

Correlating on-line monitoring parameters, pH, DO and ORP with nutrient removal in an intermittent cyclic process bioreactor system.  

PubMed

The paper presents the study correlating the profile of on-line monitoring parameters and nutrient removal in an intermittent cyclic process bioreactor (ICPBR) system, thereby utilizing the parameters as operational tool. A laboratory scale ICPBR was employed to treat low C/N ratio domestic wastewater from a township. The study was conducted for correlating biological nutrient removal and on-line monitored parameters pH, dissolved oxygen (DO) and oxidation-reduction potential (ORP). The results revealed that pH, DO and ORP related with the dynamic behavior of nutrient concentration (NH4-N, NO3-N, and PO4-P) during treatment in an ICPBR system. The variation in pH and ORP of the reactor liquor correlate to conversion of ammonia (NH4-N) and nitrate (NO3-N) concentrations, respectively. As the bioconversion of ammonia nitrogen and phosphorus are related to the varying profile of the on-line monitored parameters, the profiles could possibly be used as onsite process control parameters. PMID:18358714

Tanwar, Pankaj; Nandy, Tapas; Ukey, Pallavi; Manekar, Pravin

2008-11-01

326

Dissolved organic matter in the subterranean estuary of a volcanic island, Jeju: Importance of dissolved organic nitrogen fluxes to the ocean  

NASA Astrophysics Data System (ADS)

We observed the origin, behavior, and flux of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), colored dissolved organic matter (CDOM), and dissolved inorganic nitrogen (DIN) in the subterranean estuary of a volcanic island, Jeju, Korea. The sampling of surface seawater and coastal groundwater was conducted in Hwasun Bay, Jeju, in three sampling campaigns (October 2010, January 2011, and June 2011). We observed conservative mixing of these components in this subterranean environment for a salinity range from 0 to 32. The fresh groundwater was characterized by relatively high DON, DIN, and CDOM, while the marine groundwater showed relatively high DOC. The DON and DIN fluxes through submarine groundwater discharge (SGD) in the groundwater of Hwasun Bay were estimated to be 1.3 × 105 and 2.9 × 105 mol d- 1, respectively. In the seawater of Hwasun Bay, the groundwater-origin DON was almost conservative while about 91% of the groundwater-origin DIN was removed perhaps due to biological production. The DON flux from the entire Jeju was estimated to be 7.9 × 108 mol yr- 1, which is comparable to some of the world's large rivers. Thus, our study highlights that DON flux through SGD is potentially important for delivery of organic nitrogen to further offshore while DIN is readily utilized by marine plankton in near-shore waters under N-limited conditions.

Kim, Tae-Hoon; Kwon, Eunhwa; Kim, Intae; Lee, Shin-Ah; Kim, Guebuem

2013-04-01

327

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

328

Kaolinite dissolution and precipitation kinetics at 22 °C and pH 4  

NASA Astrophysics Data System (ADS)

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 ?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(mol/ms)=1.15×10-131-exp (-?G2RT). Stopping of flow in a close to equilibrium dissolution experiment yielded a solubility constant for kaolinite at 22 °C of 10 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 h 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(mol/ms)=3.38×10-14exp-181776}/{T2ln?}. 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 R. and Tisserand D. (2006) Dissolution kinetics as a function of the Gibbs free energy of reaction: an experimental study based on albite feldspar. Geochim. Cosmochim. Acta 70(2) 1037-1052) 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.

Yang, Li; Steefel, Carl I.

2008-01-01

329

Variation in pH Optima of Hydrolytic Enzyme Activities in Tropical Rain Forest Soils ?  

PubMed Central

Extracellular enzymes synthesized by soil microbes play a central role in the biogeochemical cycling of nutrients in the environment. The pH optima of eight hydrolytic enzymes involved in the cycles of carbon, nitrogen, phosphorus, and sulfur, were assessed in a series of tropical forest soils of contrasting pH values from the Republic of Panama. Assays were conducted using 4-methylumbelliferone-linked fluorogenic substrates in modified universal buffer. Optimum pH values differed markedly among enzymes and soils. Enzymes were grouped into three classes based on their pH optima: (i) enzymes with acidic pH optima that were consistent among soils (cellobiohydrolase, ?-xylanase, and arylsulfatase), (ii) enzymes with acidic pH optima that varied systematically with soil pH, with the most acidic pH optima in the most acidic soils (?-glucosidase, ?-glucosidase, and N-acetyl-?-glucosaminidase), and (iii) enzymes with an optimum pH in either the acid range or the alkaline range depending on soil pH (phosphomonoesterase and phosphodiesterase). The optimum pH values of phosphomonoesterase were consistent among soils, being 4 to 5 for acid phosphomonoesterase and 10 to 11 for alkaline phosphomonoesterase. In contrast, the optimum pH for phosphodiesterase activity varied systematically with soil pH, with the most acidic pH optima (3.0) in the most acidic soils and the most alkaline pH optima (pH 10) in near-neutral soils. Arylsulfatase activity had a very acidic optimum pH in all soils (pH ?3.0) irrespective of soil pH. The differences in pH optima may be linked to the origins of the enzymes and/or the degree of stabilization on solid surfaces. The results have important implications for the interpretation of hydrolytic enzyme assays using fluorogenic substrates.

Turner, Benjamin L.

2010-01-01

330

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

SciTech Connect

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

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

1988-12-01

331

Combined ion selective electrode and fluorescence quenching detection for copper-dissolved organic matter titrations  

SciTech Connect

Copper-dissolved organic matter binding is observed for Black Lake, NC, fulvic acid by measuring free metal with a copper ion selective electrode (ISE) and the unbound organic ligand by fluorescence. The two detectors agree at low, aquatic levels of copper loading; a discrepancy at high copper concentrations may result from precipitation or inappropriate assumptions about the fluorescence technique. Complementary error properties of combined detection provide low-error titration data over a wider range of pH and pCu than either detector alone. Calibration by ISE is more reliable than curve fitting for relating fluorescence to bound copper concentrations. 24 references, 6 figures.

Cabaniss, S.E.; Shuman, M.S.

1986-02-01

332

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

333

Conducting a thermal conductivity survey  

NASA Technical Reports Server (NTRS)

A physically transparent approximate theory of phonon decay rates is presented starting from a pair potential model of the interatomic forces in an insulator or semiconductor. The theory applies in the classical regime and relates the 3-phonon decay rate to the third derivative of the pair potential. Phonon dispersion relations do not need to be calculated, as sum rules relate all the needed quantities directly to the pair potential. The Brillouin zone averaged phonon lifetime turns out to involve a dimensionless measure of the anharmonicity multiplied by an effective density of states for 3-phonon decay. Results are given for rare gas and alkali halide crystals. For rare gases, the results are in good agreement with more elaborate perturbation calculations. Comparison to experimental data on phonon linewidths and thermal conductivity are made.

Allen, P. B.

1985-01-01

334

Radka Stoyanova, PhD  

Cancer.gov

Dr. Radka Stoyanova, PhD has extensive background in developing approaches to best utilize imaging techniques in cancer research, diagnosis and treatment, as well as in developing approaches for the analysis, mining, and interpretation of "big data" generated by high-throughput approaches such as genomics, proteomics, and metabolomics. She received her Masters Degree in Mathematics from the University of Sofia, Bulgaria. Dr. Stoyanova obtained her doctoral training and PhD degree at the Imperial College London, under the mentorship of Profs.

335

pH Optrode Instrumentation  

NASA Technical Reports Server (NTRS)

pH-sensitive chromophoric reagents immobilized in porous optical fibers. Optoelectronic instrumentation system measures acidity or alkalinity of aqueous nutrient solution. Includes one or more optrodes, which are optical-fiber chemical sensors, in sense, analogous to electrodes but not subject to some of spurious effects distorting readings taken by pH electrodes. Concept of optrodes also described in "Ethylene-Vapor Optrodes" (KSC-11579). pH optrode sensor head, with lead-in and lead-out optical fibers, convenient for monitoring solutions located away from supporting electronic equipment.

Tabacco, Mary Beth; Zhou, Quan

1995-01-01

336

Towards an understanding of feedbacks between plant productivity, acidity and dissolved organic matter  

NASA Astrophysics Data System (ADS)

The recent origin of much dissolved organic carbon (DOC) (Tipping et al., 2010) implies that plant productivity is a major control on DOC fluxes. However, the flocculation, sorption and release of potentially-dissolved organic matter are governed by pH, and widespread increases in DOC concentrations observed in northern temperate freshwater systems seem to be primarily related to recovery from acidification (Monteith et al., 2007). We explore the relative importance of changes in productivity and pH using a model, MADOC, that incorporates both these effects (Rowe et al., 2014). The feedback whereby DOC affects pH is included. The model uses an annual timestep and relatively simple flow-routing, yet reproduces observed changes in DOC flux and pH in experimental (Evans et al., 2012) and survey data. However, the first version of the model probably over-estimated responses of plant productivity to nitrogen (N) deposition in upland semi-natural ecosystems. There is a strong case that plant productivity is an important regulator of DOC fluxes, and theoretical reasons for suspecting widespread productivity increases in recent years due not only to N deposition but to temperature and increased atmospheric CO2 concentrations. However, evidence that productivity has increased in upland semi-natural ecosystems is sparse, and few studies have assessed the major limitations to productivity in these habitats. In systems where phosphorus (P) limitation prevails, or which are co-limited, productivity responses to anthropogenic drivers will be limited. We present a revised version of the model that incorporates P cycling and appears to represent productivity responses to atmospheric N pollution more realistically. Over the long term, relatively small fluxes of nutrient elements into and out of ecosystems can profoundly affect productivity and the accumulation of organic matter. Dissolved organic N (DON) is less easily intercepted by plants and microbes than mineral N, and DON leaching rates may thus control soil formation (Vitousek et al., 2010). Large observed DON concentrations that were observed in an experimental study are difficult to reconcile with the amount of N retention necessary to have accumulated observed organic matter stocks. We examine potential reasons for this discrepancy. - Evans CD, Jones TG, Burden A et al. (2012) Acidity controls on dissolved organic carbon mobility in organic soils. Global Change Biology 18, 3317-3331. - Monteith DT, Stoddard JL, Evans CD et al. (2007) Rising freshwater dissolved organic carbon driven by changes in atmospheric deposition. Nature 450, 537-540. - Rowe EC, Tipping E, Posch M et al. (2014) Predicting nitrogen and acidity effects on long-term dynamics of dissolved organic matter. Environmental Pollution 184, 271-282. - Tipping E, Billett MF, Bryant CL et al. (2010) Sources and ages of dissolved organic matter in peatland streams: evidence from chemistry mixture modelling and radiocarbon data. Biogeochemistry 100, 121-137. - Vitousek PM, Porder S, Houlton BZ et al. (2010) Terrestrial phosphorus limitation: mechanisms, implications, and nitrogen-phosphorus interactions. Ecological Applications 20, 5-15.

Rowe, Ed; Tipping, Ed; Davies, Jessica; Monteith, Don; Evans, Chris

2014-05-01

337

The influence of dissolved organic carbon on sorption of heavy metals on urea-treated pine bark  

Microsoft Academic Search

A previous study showed considerably higher metal adsorption by urea-treated pine bark (UTB) compared to non-treated bark (NTB) at metal adsorption from their individual relatively concentrated solutions. Comparison of the sorption characteristics of the two pine barks at low but environmentally relevant metal concentrations, and investigation of the influence of pH and dissolved organic carbon (DOC) on the sorption process

Oleksandr Khokhotva; Sylvia Waara

2010-01-01

338

Photosynthetic kinetics determine the outcome of competition for dissolved inorganic carbon by freshwater microalgae: implications for acidified lakes  

Microsoft Academic Search

Photosynthetic kinetics with respect to dissolved inorganic carbon were used to predict the outcome of competition for DIC between the green alga Selenastrum minutum and the cyanobacterium Synechococcus leopoliensis at pH 6.2, 7.5, and 10. Based on measured values of the maximum rate of photosynthesis, the half-saturation value of photosynthesis with respect to DIC (K12\\/DIC), and the DIC compensation point,

T. G. Williams; D. H. Turpin

1987-01-01

339

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

340

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

2012-02-21

341

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

342

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

2011-07-14

343

Making pH Tangible.  

ERIC Educational Resources Information Center

Presents a laboratory exercise in which students test the pH of different substances, study the effect of a buffer on acidic solutions by comparing the behavior of buffered and unbuffered solutions upon the addition of acid, and compare common over-the-counter antacid remedies. (MKR)

McIntosh, Elizabeth; Moss, Robert

1995-01-01

344

Sashwati Roy, PhD  

Cancer.gov

Dr. Sashwati Roy is an Associate Professor of Surgery and Director of the Laser Capture Molecular Core at The Ohio State University, Columbus, Ohio. In 1994 she received her PhD degree in Physiology and Environmental Sciences and later completed her postdoctoral training at the University of California, Berkeley. Dr.

345

Karl Krueger, PhD  

Cancer.gov

Dr. Karl Krueger received a PhD in biochemistry from Vanderbilt University and continued his research training at NIH as a postdoctoral fellow before joining the faculty at Georgetown University School of Medicine. His research throughout this period focused on different aspects of drug receptors and their role in the nervous system.

346

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

347

Diel behavior of rare earth elements in a mountain stream with acidic to neutral pH  

USGS Publications Warehouse

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. Copyright ?? 2005 Elsevier Ltd.

Gammons, C. H.; Wood, S. A.; Nimick, D. A.

2005-01-01

348

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

349

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

PubMed

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

Xia, Xinghui; Zhai, Yawei; Dong, Jianwei

2013-02-01

350

HYDROXYL RADICAL/OZONE RATIOS DURING OZONATION PROCESSES. II. THE EFFECT OF TEMPERATURE, PH, ALKALINITY, AND DOM PROPERTIES  

EPA Science Inventory

The influence of temperature, pH, alkalinity, and type and concentration of the dissolved organic matter (DOM) on the rate of ozone (O3) decomposition, O3-exposure, .OH-exposure and the ratio Rct of the concentrations of .OH and O3 has been studied. For a standardized single ozon...

351

Dissolved and particulate heavy metals distribution in coastal lagoons. A case study from Mar Chiquita Lagoon, Argentina  

NASA Astrophysics Data System (ADS)

Mar Chiquita Coastal Lagoon is located on the Atlantic coast of Argentina, and it has been declared a Biosphere Reserve under the UNESCO Man and Biosphere Programme (MAB). This coastal lagoon constitutes an estuarine environment with a very particular behaviour and it is ecologically important due to its biological diversity. The aim of the present study was to evaluate the distribution and geochemical behaviour of several heavy metals in this coastal system, focusing on their distribution in both the dissolved phase (<0.45 ?m) and the suspended particulate matter. Therefore, the general hydrochemical parameters (salinity, temperature, turbidity, pH and dissolved oxygen) and concentration of total particulate and dissolved metals (Cd, Cu, Ni, Zn, Fe, Pb, Cr and Mn) were measured along 2 years (2004-2006) at two different sites. As regards their distribution, hydrological parameters did not present any evidence of deviation with respect to historical values. Suspended particulate matter showed no seasonal variation or any relationship with the tide, thus indicating that in this shallow coastal lagoon neither tides nor freshwater sources regulate the particulate matter input. Heavy metals behaviour, both in dissolved and particulate phases did not reveal any relationship with tide or seasons. Mar Chiquita Coastal Lagoon showed a large input of dissolved and particulate metals, which is probably due to intensive agriculture within the drainage basin of this system.

Beltrame, María Ornela; De Marco, Silvia G.; Marcovecchio, Jorge E.

2009-10-01

352

pH optrode for the complete working range  

NASA Astrophysics Data System (ADS)

We report a fast response and inexpensive optical sensor capable of measuring pH in the range of 0.5 to 13.5 units with good resolution. Three indicator dyes viz. Bromocresol Green, Bromothymol Blue and Nile Blue were used to fabricate the sensor head. ion-exchange resin, Amberlite IRA 400, was powdered and immobilized by these dye solutions. In order to prepare sensing membranes, Polyvinyl chloride was dissolved in Tetrahydrofuran and the solution was poured on to a glass plate. Before the membrane was completely dry, the immobilized resin powder was uniformly sprinkled so that the granules are properly glued to it. A bundle of fibers was attached to the membrane mechanically to carry the light from the source to the membrane and collect the reflected optical signal. He-He laser was used as a light source. The experimental results show a linear dependence of pH value on reflected optical signal for the pH range of 0.5 to 13.5 with the resolution of 0.02 unit. The optrode was also characterized by studying the effect of ionic strength and temperature of the solution on the probe response.

Vishnoi, Gargi; Goel, Tara C.; Pillai, P. K.

1999-01-01

353

Metallurgical Evaluation of 17-4 PH Stainless Steel Castings,  

National Technical Information Service (NTIS)

A metallurgical evaluation was conducted to determine if selected castings of 17-4 PH stainless steel used in head caps on missile weapon systems had been properly heat treated as required by SAE specification AMS-5355D. Optical metallographic analysis an...

G. E. Hicho J. H. Smith

1989-01-01

354

PhDs by Publications: An "Easy Way Out"?  

ERIC Educational Resources Information Center

PhDs by publications are a relatively new model for doctoral research, especially in the context of the Humanities or Education. This paper describes two writers' experiences of conducting doctoral studies in this genre and in these faculties. Each discover alternative ways of employing a body of published research papers in development of an…

Niven, Penelope; Grant, Carolyn

2012-01-01

355

Impact of dissolved organic matter on colloid transport in the vadose zone: deterministic approximation of transport deposition coefficients from polymeric coating characteristics.  

PubMed

Although numerous studies have been conducted to discern colloid transport and stability processes, the mechanistic understanding of how dissolved organic matter (DOM) affects colloid fate in unsaturated soils (i.e., the vadose zone) remains unclear. This study aims to bridge the gap between the physicochemical responses of colloid complexes and porous media interfaces to solution chemistry, and the effect these changes have on colloid transport and fate. Measurements of adsorbed layer thickness, density, and charge of DOM-colloid complexes and transport experiments with tandem internal process visualization were conducted for key constituents of DOM, humic (HA) and fulvic acids (FA), at acidic, neutral and basic pH and two CaCl(2) concentrations. Polymeric characteristics reveal that, of the two tested DOM constituents, only HA electrosterically stabilizes colloids. This stabilization is highly dependent on solution pH which controls DOM polymer adsorption affinity, and on the presence of Ca(+2) which promotes charge neutralization and inter-particle bridging. Transport experiments indicate that HA improved colloid transport significantly, while FA only marginally affected transport despite having a large effect on particle charge. A transport model with deposition and pore-exclusion parameters fit experimental breakthrough curves well. Trends in deposition coefficients are correlated to the changes in colloid surface potential for bare colloids, but must include adsorbed layer thickness and density for sterically stabilized colloids. Additionally, internal process observations with bright field microscopy reveal that, under optimal conditions for retention, experiments with FA or no DOM promoted colloid retention at solid-water interfaces, while experiments with HA enhanced colloid retention at air-water interfaces, presumably due to partitioning of HA at the air-water interface and/or increased hydrophobic characteristics of HA-colloid complexes. PMID:21193215

Morales, Verónica L; Zhang, Wei; Gao, Bin; Lion, Leonard W; Bisogni, James J; McDonough, Brendan A; Steenhuis, Tammo S

2011-02-01

356

Long-term patterns in dissolved organic carbon, major elements and trace metals in boreal headwater catchments: trends, mechanisms and heterogeneity  

NASA Astrophysics Data System (ADS)

The boreal landscape is a complex, spatio-temporally varying mosaic of forest and mire landscape elements that control surface water hydrology and chemistry. Here, we assess long-term water quality time series from three nested headwater streams draining upland forest (C2), peat/mire (C4) and mixed (C7) (forest and mire) catchments. Acid deposition in this region is low and is further declining. Temporal trends in weather and runoff (1981-2008), dissolved organic carbon concentration [DOC] (1993-2010) and other water quality parameters (1987-2011) were assessed. There was no significant annual trend in precipitation or runoff. However, runoff increased in March and declined in May. This suggested an earlier snowmelt regime in recent years. Significant monotonic increasing trends in air temperature and length of growing season suggested a decrease in snowfall and less spring runoff. Stream [DOC] was positively correlated with some trace metals (copper, iron and zinc) and negatively with several other chemical parameters (e.g. sulfate, conductivity, calcium). Both sulfate and conductivity showed declining trends, while a significant increase was observed in pH during winter and spring. Calcium and magnesium showed monotonic decreasing trends. The declining trajectories of stream base cation and sulfate concentrations during other times of the year were not accompanied by changes in pH and alkalinity. These results indicate subtle effects of recovery from acidification. Water temperature increased significantly both annually and in most months. A simultaneous monotonic increase in iron (Fe) and [DOC] in autumn suggests co-transport of Fe-DOC in the form of organometallic complexes. A monotonic increase in UV absorbance in most months without co-occurring changes in DOC trend suggests a shift in DOC quality to a more humic-rich type. The observed increase in soil solution [DOC] and subtle trends in stream [DOC] suggest that climate rather than recovery from acidification is the dominant driver of DOC trends in the Svartberget catchment.

Oni, S. K.; Futter, M. N.; Bishop, K.; Köhler, S. J.; Ottosson-Löfvenius, M.; Laudon, H.

2013-04-01

357

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

358

Fast-response sensors for dissolved oxygen  

NASA Astrophysics Data System (ADS)

In this work we have been developing fast response optical sensors for dissolved oxygen determination based on measuring the luminescence lifetime of a metalloporphyrin polymer. The sensor is produced by electropolymerization of the metalloporphyrin monomer units of platinum tetraphenylporphyrin (Pt-TPP), platinum octaethylporphyrin (Pt-OEP), palladium tetraphenylporphyrin (Pd-TPP) or palladium octaethylporphyrin (Pd-OEP). The polymerization process results in films which are in the region of micrometers thick. The Stern-Volmer quenching constants as determined from luminescence lifetime measurements for these sensors range from 0.90 (mg 1-1)-1) for Pt-TPP to 1.83 (mg 1-1)-1) for Pd-OEP. The response time of these sensors to a step change from an oxygen free to an oxygen saturated solution is in the millisecond region.

Smith, Sheila; Hamill, Alan; Uttamlal, Mahesh; Campbell, Michael; Bailly, David

1999-12-01

359

Modeling CO 2 degassing and pH in a stream-aquifer system  

NASA Astrophysics Data System (ADS)

Pinal Creek, Arizona receives an inflow of ground water with high dissolved inorganic carbon (57-75 mg/l) and low pH (5.8-6.3). There is an observed increase of in-stream pH from approximately 6.0-7.8 over the 3 km downstream of the point of groundwater inflow. We hypothesized that CO 2 gas-exchange was the most important factor causing the pH increase in this stream-aquifer system. An existing transport model, for coupled ground water-surface water systems (OTIS), was modified to include carbonate equilibria and CO 2 degassing, used to simulate alkalinity, total dissolved inorganic carbon ( CT), and pH in Pinal Creek. Because of the non-linear relation between pH and CT, the modified transport model used the numerical iteration method to solve the non-linearity. The transport model parameters were determined by the injection of two tracers, bromide and propane. The resulting simulations of alkalinity, CT and pH reproduced, without fitting, the overall trends in downstream concentrations. A multi-parametric sensitivity analysis (MPSA) was used to identify the relative sensitivities of the predictions to six of the physical and chemical parameters used in the transport model. MPSA results implied that CT and pH in stream water were controlled by the mixing of ground water with stream water and CO 2 degassing. The relative importance of these two processes varied spatially depending on the hydrologic conditions, such as stream flow velocity and whether a reach gained or lost stream water caused by the interaction with the ground water. The coupled transport model with CO 2 degassing and generalized sensitivity analysis presented in this study can be applied to evaluate carbon transport and pH in other coupled stream-ground water systems.

Choi, J.; Hulseapple, S. M.; Conklin, M. H.; Harvey, J. W.

1998-08-01

360

Solubility of pentachlorophenol in aqueous solutions: The pH effect  

Microsoft Academic Search

As indicated in most literature reports, the solubility of pentachlorophenol (PCP) in water ranges between 10 and 20 mg l?1. Since PCP is a weak acid (pKa 4.35), its solubility increases drastically with increasing pH. When PCP dissolves in water two forms are normally present: undissociated PCP (PCP°) and a dissociated anionic form, i.e. pentachlorophenolate (PCP?). Both forms differ in

Yves Arcand; Jalal Hawari; Serge R. Guiot

1995-01-01

361

Internal R and D task summary report: large-scale dissolver cold-flow modeling  

Microsoft Academic Search

Cold-flow simulation of the SRC-I dissolvers has been performed on three columns with different height-to-diameter ratios to provide a better understanding of the fluid dynamics and operation of a three-phase gas\\/liquid\\/solid system. The experiments were conducted in 5-in.-, 12-in.-, and 6-ft-diameter columns. The effects of various parameters on gas holdup, liquid axial dispersion coefficients, solids axial distribution, and gas\\/liquid mass-transfer

Moujaes

1984-01-01

362

Interactions between dissolved organic carbon and mercury species in surface waters of the Florida Everglades  

Microsoft Academic Search

An ultrafiltration procedure has been developed to study the interaction between organic C and Hg species in natural waters, and a pilot study was conducted in the surface waters of the Florida Everglades. Compared to total Hg, CH3Hg shows different distribution patterns in the suspended particulate, colloidal, and truly dissolved phases. Colloidal forms (0.22 ?m, 3 kDa) contain the majority

Yong Cai; Rudolf Jaff; Ronald D. Jones

1999-01-01

363

Interactions between dissolved organic matter and mercury in the Florida Everglades  

Microsoft Academic Search

Experiments were conducted using organic matter isolated from various surface waters in the Florida Everglades to study the interactions between dissolved organic matter (DOM) and Hg (II). Conditional distribution coefficients (K_{DOM^prime}), obtained using an equilibriurn dialysis ligand exchange method, were strongly affected by the Hg\\/DOM concentration ratio. Very strong interactions (K_{DOM^prime} = 10^{23.2 ± 05} L kg^{-1}), indicative of Hg-thiol

G. Aiken; M. Haitzer; J. N. Ryan; K. Nagy

2003-01-01

364

Numerical simulation of dissolved oxygen in Jakarta Bay  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

365

Sorption of trace metals by standard and micro suction cups in the absence and presence of dissolved organic carbon.  

PubMed

Both the bioavailability of a trace metal (TM) in a soil and the risk of leaching to the ground water are linked to the metals concentration in the soil solution. Sampling soil solution by tension lysimetry with suction cups is a simple and established technique that is increasingly used for monitoring dissolved TM in soils. Of major concern, however, is the sorption of TM by the walls of the samplers. Metal sorption by different materials used in suction cups can vary widely, depending also on the chemistry of the soil solution. We compared the sorption of Cu, Zn, Cd, and Pb by different standard-size and micro suction cups in the laboratory at two pH values (4.5 and 7.5 or 8.0) in absence and presence of dissolved organic carbon (DOC). In addition, we investigated the sorption of DOC from different origins by the cup materials. At both pH values, the weakest sorption of all four TMs was exhibited by standard-size suction cups based on nylon membranes and by hollow fibers made from polyvinyl alcohol (PVA). At alkaline pH, borosilicate glass, ceramic materials, and polytetrafluorethylene (PTFE) mixed with silicate were characterized by generally strong sorption of all investigated TMs. In addition, Cu and Pb were strongly sorbed at low pH by PTFE-silicate and a ceramic material used for the construction of standard-size suction cups. On the other hand, sorption of Cu, Zn, and Cd by ceramic capillaries produced from pure aluminum oxide was negligible at low pH. Micro suction cups made of an unknown polymerous tube sorbed Cu strongly, but were well suited to monitor Zn, Cd, and Pb at low pH, and, in the presence of DOC, also at high pH. Major cations (Na+, Mg2+, K+, Ca2+) and anions (Cl-, NO3-, SO4(2-)) were not or very weakly sorbed by all cup materials, except for Mg2+, K+, and Ca2+ by borosilicate glass at pH 7.5. Trace metal sorption by suction cups was generally greatly reduced in the presence of DOC, especially at alkaline pH. The sorption of DOC itself depended on its source. Dissolved organic carbon from leaf litter extracts with a probably large hydrophobic fraction was sorbed more strongly than mainly hydrophilic DOC from a mineral soil solution. PMID:16391276

Rais, D; Nowack, B; Schulin, R; Luster, J

2006-01-01

366

Oxidation of dissolved elemental mercury by thiol compounds under anoxic conditions  

SciTech Connect

Mercuric mercury, Hg(II), forms strong complexes with thiol compounds that commonly dominate Hg(II) speciation in natural freshwater. However, reactions between dissolved elemental Hg(0) and thiols are not well understood although these processes are likely to be important in determining Hg speciation and geochemical cycling in the environment. In this study, reaction rates and mechanisms between dissolved Hg(0) and a number of selected organic ligands with varying molecular structures and sulfur (S) oxidation states were determined to assess the role of these ligands in Hg(0) redox transformation. We found that all thiols caused oxidation of Hg(0) under anoxic conditions but, contrary to expectation, compounds with higher S-oxidation states (e.g., disulfide) than thiols exhibited little or no reactivity with Hg(0) at pH 7. The rate and extent of Hg(0) oxidation varied widely, with smaller aliphatic thiols showing the greatest degree of oxidation. The mechanism of the oxidation is attributed to a two-step process involving adsorption of Hg(0) to thiols followed by the charge transfer from Hg(0) to electron acceptors. These observations demonstrate a unique thiol-induced oxidation pathway of dissolved Hg(0), with important implications for the redox transformation, speciation, and bioavailability of Hg for microbial methylation in anoxic environments.

Zheng, Wang [ORNL] [ORNL; Lin, Hui [ORNL] [ORNL; Mann, Benjamin F [ORNL] [ORNL; Liang, Liyuan [ORNL] [ORNL; Gu, Baohua [ORNL] [ORNL

2013-01-01

367

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

368

Method to Estimate the Dissolved Air Content in Hydraulic Fluid  

NASA Technical Reports Server (NTRS)

In order to verify the air content in hydraulic fluid, an instrument was needed to measure the dissolved air content before the fluid was loaded into the system. The instrument also needed to measure the dissolved air content in situ and in real time during the de-aeration process. The current methods used to measure the dissolved air content require the fluid to be drawn from the hydraulic system, and additional offline laboratory processing time is involved. During laboratory processing, there is a potential for contamination to occur, especially when subsaturated fluid is to be analyzed. A new method measures the amount of dissolved air in hydraulic fluid through the use of a dissolved oxygen meter. The device measures the dissolved air content through an in situ, real-time process that requires no additional offline laboratory processing time. The method utilizes an instrument that measures the partial pressure of oxygen in the hydraulic fluid. By using a standardized calculation procedure that relates the oxygen partial pressure to the volume of dissolved air in solution, the dissolved air content is estimated. The technique employs luminescent quenching technology to determine the partial pressure of oxygen in the hydraulic fluid. An estimated Henry s law coefficient for oxygen and nitrogen in hydraulic fluid is calculated using a standard method to estimate the solubility of gases in lubricants. The amount of dissolved oxygen in the hydraulic fluid is estimated using the Henry s solubility coefficient and the measured partial pressure of oxygen in solution. The amount of dissolved nitrogen that is in solution is estimated by assuming that the ratio of dissolved nitrogen to dissolved oxygen is equal to the ratio of the gas solubility of nitrogen to oxygen at atmospheric pressure and temperature. The technique was performed at atmospheric pressure and room temperature. The technique could be theoretically carried out at higher pressures and elevated temperatures.

Hauser, Daniel M.

2011-01-01

369

PhET Simulation: Density  

NSDL National Science Digital Library

This simulation provides a highly visual, intuitive way for students to explore how density is related to an object's mass and volume. Using a virtual water tank, users drop various objects to see what floats and what sinks. Use the mouse to submerge the object and see how much fluid it displaces. A scale is provided to measure the mass of the objects, with a density table available for view. Students can easily see why the density formula works, especially when they identify the "mystery" objects. Editor's Note: Scroll down on the page for exemplary lesson plans for grades 6-12 developed by the PhET project specifically to accompany the "Density" simulation. This item is part of a larger collection of simulations developed by the Physics Education Technology project (PhET).

2011-02-16

370

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

2013-02-15

371

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

SciTech Connect

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 order in DOC for 1-10 mg C/liter, and variable-order in pH. Increasing Ca/sup + +/ or Mg/sup + +/ from 0 to 10 mM slightly increases Cu/sup + +/ activity, while increasing ionic strength from 0.005 to 0.1 significantly increases Cu/sup + +/ activity. An empirical N-site model was calibrated using a pooled set of six titrations with varying pH and DOC. Five binding components of varying proton dependence predict Cu binding by FA over a range of pH, DOC and total Cu in two verification tests of the model parameters. Parameters in this and other models tested are only empirical constructs.

Cabaniss, S.E.; Shuman, M.S.

1988-01-01

372

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)] [Univ. of Idaho, Moscow, ID (United States)

1999-01-15

373

Christos Patriotis, PhD  

Cancer.gov

Dr. Christos Patriotis obtained his MSc in Biochemistry from the University of Sofia, Bulgaria in 1985 and his PhD in Molecular Biology from the Bulgarian Academy of Sciences in 1990. Postdoctoral training focused on signal transduction and tumor cell biology. He joined the faculty at Fox Chase Cancer Center in 1998; his research was directed toward understanding mechanisms of breast and ovarian cancer pathogenesis and identification of biomarkers associated with the early stages of the two types of cancer.

374

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

375

Molecular simulation of a model of dissolved organic matter  

SciTech Connect

A series of atomistic simulations was performed to assess the ability of the Schulten dissolved organic matter (DOM) molecule, a well-established model humic molecule, to reproduce the physical and chemical behavior of natural humic substances. The unhydrated DOM molecule had a bulk density value appropriate to humic matter, but its Hildebrand solubility parameter was lower than the range of current experimental estimates. Under hydrated conditions, the DOM molecule went through conformational adjustments that resulted in disruption of intramolecular hydrogen bonds (H-bonds), although few water molecules penetrated the organic interior. The radius of gyration of the hydrated DOM molecule was similar to those measured for aquatic humic substances. To simulate humic materials under aqueous conditions with varying pH levels, carboxyl groups were deprotonated, and hydrated Na{sup +} or Ca{sup 2+} were added to balance the resulting negative charge. Because of intrusion of the cation hydrates, the model metal- humic structures were more porous, had greater solvent-accessible surface areas, and formed more H-bonds with water than the protonated, hydrated DOM molecule. Relative to Na{sup +}, Ca{sup 2+} was both more strongly bound to carboxylate groups and more fully hydrated. This difference was attributed to the higher charge of the divalent cation. The Ca-DOM hydrate, however, featured fewer H-bonds than the Na-DOM hydrate, perhaps because of the reduced orientational freedom of organic moieties and water molecules imposed by Ca{sup 2+}. The present work is, to our knowledge, the first rigorous computational exploration regarding the behavior of a model humic molecule under a range of physical conditions typical of soil and water systems.

Sutton, Rebecca; Sposito, Garrison; Diallo, Mamadou S.; Schulten,Hans-Rolf

2004-11-08

376

Effect of Ph on Human Complement Activity.  

National Technical Information Service (NTIS)

The influence of pH on the haemolytic activity of human complement (HuC') was investigated over the pH range 5.55-8.20. Maximum haemolytic activity of HuC' was observed at pH 6.77 and not at the pH level (7.2) usually used. Adjustment of pH to either the ...

B. J. Fogel W. A. Hook E. H. Fife

1966-01-01

377

Phenol removal using zero-valent iron powder in the presence of dissolved oxygen: roles of decomposition by the Fenton reaction and adsorption/precipitation.  

PubMed

The mechanism for removal of phenol by zero-valent iron (ZVI) was quantitatively evaluated in the presence of dissolved oxygen by varying the pH from 2 to 8.1 (natural). The measurement of OH radical concentration suggests that the removal of phenol by ZVI was occurred due to the decomposition by the Fenton reaction besides the adsorption/precipitation to the iron surface. From the measurements of dissolved organic carbon (DOC) in the filtrate with the 0.45 ?m syringe filter and the solution obtained from acidification of suspended precipitates, the roles of decomposition by the Fenton reaction and adsorption/precipitation were separately evaluated. At solution pH 3, 91% of phenol removal was achieved and 24% of TOC (total organic carbon) decreased. The contribution of the Fenton reaction was found to be 77% of overall TOC reduction. When the pH values were 4 and 5, the overall TOC removal was found to be mainly due to the adsorption/precipitation. At pH 2 and 8.1, the reduction of TOC was very small. The pH and dissolved oxygen significantly affected the dissolution of iron and the production of OH radicals and changed the roles of phenol removal by the Fenton reaction and adsorption/precipitation. PMID:22119308

Shimizu, Ayana; Tokumura, Masahiro; Nakajima, Koshiro; Kawase, Yoshinori

2012-01-30

378

Effects of pH on aquatic biodegradation processes  

NASA Astrophysics Data System (ADS)

To date, little is known about the pH-stimulated mineralization of organic matter in aquatic environments. In this study, we investigated biodegradation processes in alkaline waters. Study site is a large shallow soda lake in Central Europe (Neusiedler See/Ferto). The decomposition rate of plant litter was measured as a function of pH by incubating air-saturated lake-water samples in contact with Phragmites litter (leaves) from the littoral vegetation. All samples showed high decomposition rates (up to 32% mass loss within 35 days) and a characteristic two-step degradation mechanism. During the degradation process, the solid plant litter was dissolved forming humic colloids. Subsequently, the humic colloids were mineralized to CO2 in the water column. The decomposition rate was linearly related to pH. Increasing pH values accelerated significantly the leaching of humic colloids as well as the final degradation process. The observed two-step mechanism controls the wetland/lake/air carbon fluxes, since large quantities of humic colloids are currently produced in the reed belt, exported through wind-driven circulations and incorporated into the open lake foodweb. At present, the lake is rapidly shrinking due to peat deposition in the littoral zone, whereas it has been resistant to silting-up processes for thousands of years. In order to investigate the cause of this abrupt change, the chemical composition of the lake-water was measured during 1995-2007. A thorough analysis of these data revealed that major lake-water discharges through the lake's artificial outlet channel led to a decline in salinity and alkalinity. According to our estimates, the lake's original salinity and alkalinity was 70-90% higher compared to the present conditions, with the consequence of substantially lower pH values in the present lake. The observed pH dependence of reed litter biodegradation rates points to a causal connection between low pH values and accumulation of peat in the lake basin. Our results suggest that the pH stimulated remineralisation of organic matter plays a major role in maintaining the long-term integrity of saline lake/wetland systems.

Krachler, R. F.; Krachler, R.; Stojanovic, A.; Wielander, B.; Herzig, A.

2009-01-01

379

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

380

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

381

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

Microsoft Academic Search

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

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

2003-01-01

382

Impact of salinity and pH on the UVC/H2O2 treatment of reverse osmosis concentrate produced from municipal wastewater reclamation.  

PubMed

While reverse osmosis (RO) technology is playing an increasingly important role in the reclamation of municipal wastewater, safe disposal of the resulting RO concentrate (ROC), which can have high levels of effluent organic pollutants, remains a challenge to the water industry. The potential of UVC/H(2)O(2) treatment for degrading the organic pollutants and increasing their biodegradability has been demonstrated in several studies, and in this work the impact of the water quality variables pH, salinity and initial organic concentration on the UVC/H(2)O(2) (3 mM) treatment of a municipal ROC was investigated. The reduction in chemical oxygen demand and dissolved organic carbon was markedly faster and greater under acidic conditions, and the treatment performance was apparently not affected by salinity as increasing the ROC salinity 4-fold had only minimal impact on organics reduction. The biodegradability of the ROC (as indicated by biodegradable dissolved organic carbon (BDOC) level) was at least doubled after 2 h UVC/H(2)O(2) treatment under various reaction conditions. However, the production of biodegradable intermediates was limited after 30 min treatment, which was associated with the depletion of the conjugated compounds. Overall, more than 80% of the DOC was removed after 2 h UVC/3 mM H(2)O(2) treatment followed by biological treatment (BDOC test) for the ROC at pH 4-8.5 and electrical conductivity up to 11.16 mS/cm. However, shorter UV irradiation time gave markedly higher energy efficiency (e.g., EE/O 50 kWh/m(3) at 30 min (63% DOC removal) cf. 112 kWh/m(3) at 2 h). No toxicity was detected for the treated ROC using Microtox(®) tests. Although the trihalomethane formation potential increased after the UVC/H(2)O(2) treatment, it was reduced to below that of the raw ROC after the biological treatment. PMID:22542130

Liu, Kai; Roddick, Felicity A; Fan, Linhua

2012-06-15

383

Dissolved organic C export is highly dynamic - capturing this variability and challenges in modelling  

NASA Astrophysics Data System (ADS)

High resolution, field-deployable sensors offer opportunities to deepen our understanding of natural environmental systems, and measure the ';riverine pulse'. Studies utilising high-resolution equipment have demonstrated that sampling hydrological variables on traditional low frequency rates (such as once a week) creates a simplified picture of conditions that does not capture a true reflection of how fluvial systems operate. Dissolved organic carbon (DOC) represents a large and diverse mixture of compounds (including sugars, amino acids and humic substances) and concentration and composition of this pool varies globally. Understanding transport of this C pool in fluvial systems is important as it 1) represents the lateral export of C no longer sequestered in the terrestrial system, 2) surface water concentrations have been observed to have increased globally and we need to know if this trend is continuing and 3) when water is abstracted the purification processes removing DOC from the water, can create harmful by-products and so prior knowledge of inflow loading is valuable. Traditionally [DOC] has been measured using manual sampling methods, where a water sample would be collected in the field and returned to the lab. This approach can provide reliable data but the resource required to sustain this make it nearly impossible to measure the ';riverine pulse' through the information in long and detailed time series. In recent years new technology designed to estimate [DOC] in-situ has been developed. We have used one of these devices, which measures absorption in both the visible and UV wavelength regions of the electromagnetic spectrum and from this absorbance profile an algorithm estimates [DOC]. We have deployed this system in the field environment and after overcoming initial challenges have an almost continuous time series of [DOC], measured at 30 minute intervals, since May 2012. The logger has been functioning over a temperature range of 0.5 - 23 °C and a [DOC] range of 8 - 55.6 mg/l C, with the greatest shift in a single day being 23.5 mg/l C. We will present this highly dynamic [DOC] time series and also contemporaneous data from an in-situ water chemistry sonde profiling other measures of the ';riverine circulation system': pH, conductivity, temperature and stage height. The challenge now is how to allow data series of ~17,500 measurements per annum to interact to better understand and model drivers of carbon export. We are exploring the application of wavelet analysis to identify periods of coherence between [DOC] and these other variables. Our initial results indicate show that coherence with [DOC] can be intermittent and irregular, and so the challenge sensor technology presents continues.

Waldron, S.; Coleman, M.; Scott, E. M.; Drew, S.

2013-12-01

384

Transient Dissolved Organic Carbon Through Soils  

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

385

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

386

Contribution of ferric iron to the absorption by chromophoric dissolved matter  

NASA Astrophysics Data System (ADS)

Chromophoric dissolved organic matter (CDOM) is a major absorber of ultraviolet and visible radiation in surface waters. CDOM consists primarily of humic substances (HS), which can adsorb inorganic cations such as ferric iron. Often more than 99% of dissolved iron is complexed by CDOM in natural waters. Our study assessed the contribution of ferric iron to the absorption of CDOM by mixing dissolved humic substance (HS) standards with iron(III) in acidic conditions and later adjusting the pH to 8. The maximum iron-binding capacities for Suwannee River humic acid, Suwannee River fulvic acid and Pony Lake fulvic acid were 13.0, 13.5 and 7.64 ?mol iron [mg C]-1, respectively, suggesting higher iron-binding capacity for terrestrial- than microbial-derived CDOM. Iron(III) associated with HS increased the absorption coefficient by CDOM by 1.73-5.33 times (?=254-550 nm). Inorganic iron, thus, contributed up to 4/5 of the absorption by CDOM (?=550 nm). In other words, only less than 1/5 of the absorption by CDOM-iron mixture was generated by organic chromophores. The associated iron decreased spectral slope coefficients of HS. This finding indicates that changes of the spectral slope by CDOM can be solely caused by inorganic interference (e.g. iron). The increase of absorption by associated iron(III) was always spectrally similar among different HS standards. We calculated a specific absorption spectrum for iron associated with dissolved HS standards. This spectrum allows estimates for the absorption by iron associated with HS in circum neutral natural waters. For Löytynlähde spring water, iron contributed over 1/10 (ca. 0.108, ?=400 nm) to the total absorption. The contribution of iron to total absorption increased with wavelength. In typical CDOM absorption measurement, water samples are filtered for the removal of particulate constituents but no attempts are implemented for separating the organic chromophores from inorganic chromophores. Our findings show that inorganic chromophores can contribute remarkably to the absorption of filtered water. So, if inorganic chromophores cannot be separated from organic chromophores, we recommend a change in the current terminology. "Chromophoric dissolved matter, CDM" should be used instead of the earlier term "chromophoric dissolved organic matter, CDOM".

Xiao, Y. H.; Sara-aho, T.; Vähätalo, A. V.

2012-04-01

387

Electrochemical Stability of Polyaniline Beyond pH 9  

NASA Astrophysics Data System (ADS)

Conductive polymer films are promising candidates for solution-based biosensor and organic electrochemical transistor devices. For many conducting polymers, however, stable electrochemical activity often demands restrictively acidic solutions. This need has in turn limited the use of conductive polymers in near-neutral and physiological conditions. Using spectroelectrochemical methods, we studied the stability of polyaniline that is template synthesized on poly(2-acrylamido-2-methyl-1-propanesulfonic acid) as a function of pH. Transitions between the different oxidation states of polyaniline are stable and reversible in solutions as high as pH 10. This range of sustained electroactivity far exceeds that of previously reported polyaniline systems. In comparison, polyaniline that is doped with small-molecule acids loses its electroactivity in solutions beyond pH 4. Immobilization of polyaniline within a polymer acid matrix retards dopant diffusivity and reduces proton mobility. The preservation of local acidic conditions within the film greatly extends the pH range of stable electroactivity.

Tarver, Jacob; Yoo, Joung Eun; Loo, Yueh-Lin

2009-03-01

388

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

389

Removal of Dissolved Organic Carbon and Color from Dyeing Wastewater by Pre-ozonation and Subsequent Biological Treatment  

Microsoft Academic Search

The effects of pre-ozonation and subsequent biological treatment on the decrease in dissolved organic carbon (DOC) and color from dyeing wastewater were investigated. Moreover, the compositions of organic compounds in raw wastewater (RW) and the respective treated waters were estimated, and microscopic observations of the mixed liquor were conducted. The amount of ozone required to remove 1 mg of DOC

Nobuyuki Takahashi; Tomoya Kumagai

2006-01-01

390

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

391

Composition of dissolved organic matter in groundwater  

NASA Astrophysics Data System (ADS)

Groundwater constitutes a globally important source of freshwater for drinking water and other agricultural and industrial purposes, and is a prominent source of freshwater flowing into the coastal ocean. Therefore, understanding the chemical components of groundwater is relevant to both coastal and inland communities. We used electrospray ionization coupled with Fourier-transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) to examine dissolved organic compounds in groundwater prior to and after passage through a sediment-filled column containing microorganisms. The data revealed that an unexpectedly high proportion of organic compounds contained nitrogen and sulfur, possibly due to transport of surface waters from septic systems and rain events. We matched 292 chemical features, based on measured mass:charge ( m/z) values, to compounds stored in the Kyoto Encyclopedia of Genes and Genomes (KEGG). A subset of these compounds (88) had only one structural isomer in KEGG, thus supporting tentative identification. Most identified elemental formulas were linked with metabolic pathways that produce polyketides or with secondary metabolites produced by plants. The presence of polyketides in groundwater is notable because of their anti-bacterial and anti-cancer properties. However, their relative abundance must be quantified with appropriate analyses to assess any implications for public health.

Longnecker, Krista; Kujawinski, Elizabeth B.

2011-05-01

392

Porewater oxidation, dissolved phosphate and the iron curtain  

Microsoft Academic Search

The process of dissolved phosphate removal from aqueous solution, which occurs during oxidation of soluble ferrous compounds to insoluble ferric forms, was examined in soils of two tidal freshwater marshes. Sites of amorphous iron deposition and sorption or co-precipitation of phosphate were found to be in surface soils and along creekbanks, where both ion diffusion and porewater advection move dissolved

Randolph M. Chambers; William E. Odum

1990-01-01

393

Radiation aspects of the Redox multipurpose dissolver incident  

Microsoft Academic Search

This report is a record of the radiation and contamination effect of the Redox multipurpose dissolver incident and the steps taken after the incident to control the contamination. The new multipurpose dissolver was installed in R cell in March, 1960. It was used successfully until the evening of April 17, 1960, at which time some of the uranium metal ignited

Uebelacker

1960-01-01

394

Spectroscopic characterization of dissolved organic matter isolated from rainwater  

Microsoft Academic Search

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

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

2009-01-01

395

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

396

CHECK-OUT OF BETTIS DISSOLVED OXYGEN ANALYZER, MODEL 3  

Microsoft Academic Search

A Bettis Dissolved Oxygen Analyzer was constructed, calibrated, tested ; on 100A-loop D, and installed at the HRT. The analyzer was sensitive to less ; than 10 parts per billion of oxygen dissolved in water circulating at 200 deg C ; in 100A-loop D, gave readings in the 0.1 to 30 parts per million range in ; agreement with chemical

R. S. Greeley; P. D. Neumann; S. E. Bolt; J. C. Griess

1960-01-01

397

Temperature and Dissolved Oxygen Data for Lake Ontario, 1972 (IFYGL).  

National Technical Information Service (NTIS)

Continuous dissolved oxygen profiles taken in Lake Ontario in 1972 (IFYGL) have been edited, corrected, and averaged over 2-m intervals and over up and down traces to give temperature, dissolved oxygen, and oxygen percent saturation profiles at up to 27 d...

J. D. Boyd B. J. Eadie

1978-01-01

398

Black Carbon in Estuarine and Coastal Ocean Dissolved Organic Matter  

NASA Technical Reports Server (NTRS)

Analysis of high-molecular-weight dissolved organic matter (DOM) from two estuaries in the northwest Atlantic Ocean reveals that black carbon (BC) is a significant component of previously uncharacterized DOM, suggesting that river-estuary systems are important exporters of recalcitrant dissolved organic carbon to the ocean.

Mannino, Antonio; Harvey, H. Rodger

2003-01-01

399

Rheological, surface and colorbvietric properties of egg albumen gel affected by pH  

Microsoft Academic Search

Studies were conducted to evaluate the effects of albumen at naturally existing pH ranges on the functional and gel characteristics. Albumen was obtained from freshly laid shell eggs. The pH of albumen was altered using either IN NaOH or IN HC1 to obtain a pH of 7.5, 8.0, 8.5, 9.0, 9.5 and 10.0. The altered albumen was tested for its

T. C. Chen

1999-01-01

400

Kinetic rates of amorphous As 2S 3 oxidation at 25 to 40°C and initial pH of 7.3 to 9.4  

NASA Astrophysics Data System (ADS)

The experimental studies of As 2S 3 (am) oxidative dissolution were investigated by use of particle sizes of 8 to 44 ?m in a mixed flow reactor at 25 to 40°C and initial pH 7.3 to 9.4 to determine the effect of dissolved oxygen content, temperature, sulfate, and pH at 0.01 M ionic strength. Most experiments ran for ˜30 h; however, some longer (52 h) and shorter (6-10 h) experiments were also conducted. In most experiments, the As and S release rates had reached an apparent steady state after 20 h. For most experiments, oxidation became stoichiometric after a steady state condition was achieved. The arsenic and sulfur release rates after 20 h in most experiments are in the order of 2.70 × 10 -10 to 4.90 × 10 -9 mol m -2 s -1 in the presence of oxygen. The rate laws of As 2S 3 (am) oxidation were only determined for experiments that ran for ˜30 h at 25 to 40°C and steady state pH 6.9 to 7.9 and are given as follows: Rate law: Activation energy:R( As) =10 -16.77[ DO] 0.42[ H+] -1.26 16.8±5.0 kJ mol-1R( S) =10 -16.99[ DO] 0.35[ H+] -1.25 16.3±5.4 kJ mol-1, where R is the rate of As 2S 3 (am) destruction (mol m -2s -1), [DO] is the concentration of dissolved oxygen (M), and [H +] is the concentration of protons (M). The low activation energy of As 2S 3 (am) oxidative dissolution indicates diffusion control as the dominant mechanism. Moreover, most solid surfaces after the experiments appear smooth and undisturbed. In all experiments, As(III) is present in proportions ranging from ˜49 to 92% of total As at steady-state conditions. Sulfur oxyanions occurred as sulfate (SO 42-), sulfite (SO 32-), and polythionates (S nO 62-) where polythionates are found to be the dominant sulfur species. The acid generated from As 2S 3 (am) at 25°C and pH 7 to 9 can be expressed as follows: [ H+] prod=7.89[ H+] initial+(2.37×10 -7), where [H +] prod is the proton release from the oxidation of As 2S 3 (am) (mol/g), [H +] initial is the initial amount of proton, and 2.37 × 10 -7 is an empirical factor.

Lengke, Maggy F.; Tempel, Regina N.

2001-07-01

401

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

PubMed Central

Rates of photosynthetic O2 evolution, for measuring K0.5(CO2 + HCO3?) at pH 7, upon addition of 50 micromolar HCO3? to air-adapted Chlamydomonas, Dunaliella, or Scenedesmus cells, were inhibited up to 90% by the addition of 1.5 to 4.0 millimolar salicylhydroxamic acid (SHAM) to the aqueous medium. The apparent K1(SHAM) for Chlamydomonas cells was about 2.5 millimolar, but due to low solubility in water effective concentrations would be lower. Salicylhydroxamic acid did not inhibit oxygen evolution or accumulation of bicarbonate by Scenedesmus cells between pH 8 to 11 or by isolated intact chloroplasts from Dunaliella. Thus, salicylhydroxamic acid appears to inhibit CO2 uptake, whereas previous results indicate that vanadate inhibits bicarbonate uptake. These conclusions were confirmed by three test procedures with three air-adapted algae at pH 7. Salicylhydroxamic acid inhibited the cellular accumulation of dissolved inorganic carbon, the rate of photosynthetic O2 evolution dependent on low levels of dissolved inorganic carbon (50 micromolar Na-HCO3), and the rate of 14CO2 fixation with 100 micromolar [14C] HCO3?. Salicylhydroxamic acid inhibition of O2 evolution and 14CO2-fixation was reversed by higher levels of NaHCO3. Thus, salicylhydroxamic acid inhibition was apparently not affecting steps of photosynthesis other than CO2 accumulation. Although salicylhydroxamic acid is an inhibitor of alternative respiration in algae, it is not known whether the two processes are related.

Goyal, Arun; Tolbert, N. Edward

1990-01-01

402

Natural Attenuation of Zn, Cu, Pb and Cd in Three Biosolids-Amended Soils of Contrasting pH Measured Using Rhizon Pore Water Samplers  

Microsoft Academic Search

The effects of application of biosolids, at four rates, to an alkaline (pH 8.4), neutral (pH 7.0) and acidic (pH 4.0) soil\\u000a on concentrations of Cu, Zn, Pb, Cd and dissolved organic C in soil solution were measured over a 170-day period in a laboratory\\u000a incubation study using Rhizon pore water samplers. Applications of biosolids decreased solution pH in the alkaline soil, increased

Ghulam Murtaza; Richard John Haynes; Ravindra Naidu; Oxana N. Belyaeva; Kwon-Rae Kim; Dane T. Lamb; Nanthi S. Bolan

403

The pH of antiseptic cleansers  

PubMed Central

Background Daily bathing with antiseptic cleansers are proposed by some physicians as an adjunctive management of atopic dermatitis (AD). As atopic skin is sensitive, selection of cleansing products becomes a topic of concern. Objective Our purpose is to evaluate the pH of various antiseptic body cleansers to give an overview for recommendation to patients with AD. Methods Commonly bar and liquid cleansers consisted of antiseptic agents were measured for pH using pH meter and pH-indicator strips. For comparison, mild cleansers and general body cleansers were also measured. Results All cleansing bars had pH 9.8-11.3 except syndet bar that had neutral pH. For liquid cleansers, three cleansing agents had pH close to pH of normal skin, one of antiseptic cleansers, one of mild cleansers and another one of general cleansers. The rest of antiseptic cleansers had pH 8.9-9.6 while mild cleansers had pH 6.9-7.5. Syndet liquid had pH 7 and general liquid cleansers had pH 9.6. Conclusion The pH of cleanser depends on composition of that cleanser. Adding antiseptic agents are not the only factor determining variation of pH. Moreover, benefit of antiseptic properties should be considered especially in cases of infected skin lesions in the selection of proper cleansers for patients with AD.

Kulthanan, Kanokvalai; Varothai, Supenya; Nuchkull, Piyavadee

2014-01-01

404

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

405

The effect of aerosols on pH of snow  

NASA Astrophysics Data System (ADS)

The pH and electrolytic conductivity of meltwater from fresh snow and snow covered by fly ash were examined to study the effect of aerosols from a coal-burning power plant in Fairbanks, Alaska, and an oil-burning heating plant in Hanover, New Hampshire. New Hampshire fresh snow samples collected in 1985-1987 were found to have pH values from 3.76 to 5.20 and electrolytic conductivities from 4.23 to 104.5 ?S cm -1. Snow accompanied by southerly winds from densely populated areas averaged 3.69 times higher in hydrogen ion concentration than snow accompanied by northerly winds. Oil fly ash examined by SEM and EDX analyzer were spherical in shape with a porous structure and were carbonaceous in nature with a relatively high content of sulfur and low content of calcium. The correlations among pH, electrolytic conductivity, and oil fly ash concentration in snow were examined. The snow pH was slightly increased from 4.66 to 4.82 by increasing concentration of fly ash from 2.3 to 3314 mg kg -1 due to the relatively low solubility of alkaline ions in the oil fly ash. The electrolytic conductivity was decreased from 10.0 to 7.1 ?S cm -1 by increasing concentration of oil fly ash due to its carbonaceous nature. Alaskan fresh snow samples in 1985 were measured to have a mean pH of 5.60 and electrolytic conductivity of 6.10 ?S cm -1. Alaskan coal fly ash particles were spherical in shape with high contents of calcium, silicon and aluminium and low contents of iron, titanium and sulfur. The snow pH was increased from 5.40 to 8.51 by increasing the concentration of coal fly ash from 5.9 to 520 mg kg -1; the electrolytic conductivity was also increased from 6.93 to 46.4 ?S cm -1 due to the relatively large solubility of alkaline ions in the calcium-rich coal fly ash.

Kumai, Motoi

406

Memristive sensors for pH measure in dry conditions  

NASA Astrophysics Data System (ADS)

A large progress in pH sensing with nanowire based ion-sensitive field-effect transistors (ISFETs) has been demonstrated over the years. The electrochemical reactions occurring at the wire surface-to-electrolyte interface play a key role in the detection of ions. In this letter, we show that pH sensing can also be performed on dried samples, through electrical measurements in air with a new kind of memristive sensor. The detection of different concentrations of [H+] is confirmed by both the increased conductance and hysteretic voltage gap of the wires. The observed change in the electrical properties with pH in dry conditions is related to the formation of a wet film at the nanowire surface. Ions from the initial solution are free to move in the final water thin film at the sensing interface with consequent polarization of the NW surface.

Puppo, Francesca; Di Ventra, Massimiliano; De Micheli, Giovanni; Carrara, Sandro

2014-06-01

407

PhET Teacher Activities: Experimental Design with Forces  

NSDL National Science Digital Library

This middle school lesson plan blends a classroom experiment with the interactive PhET simulation Masses and Springs. Students design and conduct an experiment to test their predictions about the behavior of springs with masses attached. The simulation is used to explore kinetic and potential energy of spring motion and to visualize how the spring moves on different planets with varied gravitational constants. The lesson provides extensive background information for both educators and learners, scripted teacher discussion, student guides, and assessment materials with answer keys. The "Masses & Springs" simulation (which is required to complete this activity) is available from PhET at: Masses & Springs. This lesson is part of the PhET (Physics Education Technology Project), a large collection of free interactive science simulations.

Texas, Uteach -.

2012-09-24

408

PhET Teacher Ideas: The Greenhouse Effect Lab  

NSDL National Science Digital Library

This page features an inquiry-based lab, created by a high school teacher for use with the PhET simulation Greenhouse Effect. The author gives explicit instructions for using the simulation to conduct an experiment. The experimental question: "Which atmospheric gas -- methane, water, carbon dioxide, oxygen, or nitrogen -- is the best absorber of infrared photons?" Students will be using the "Photon Absorption" section of the simulation, in which they shoot infrared and visible photons from a virtual emission gun. They can change and adjust levels of each gas to build their own atmospheric conditions. A comprehensive rubric is included. The related simulation, which is required to complete this activity, is available from PhET at: Greenhouse Effect Simulation. This item is part of a growing collection of simulations by the Physics Education Technology Project (PhET). Simulations were designed using principles from physics education research and refined based on student interviews and classroom observations.

Van Houten, Greg

409

Removal of total dissolved solids, nitrates and ammonium ions from drinking water using charge-barrier capacitive deionisation  

Microsoft Academic Search

A charge-barrier capacitive deionisation system was tested for electrochemical removal of Total Dissolved Solids (TDS), nitrates and ammonium ions. Several experiments were conducted with inorganic species spiked in tap water. The system efficiency was first evaluated using experimental statistical designs with different concentrations of NaCl (150 to 3000mg\\/L). The raw water conductivity and the targeted residual TDS in treated water

Romain Broséus; John Cigana; Benoit Barbeau; Catherine Daines-Martinez; Hervé Suty

2009-01-01

410