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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.



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.



Daily and seasonal variability of pH, dissolved oxygen, temperature, and specific conductance in the Colorado River between the forebay of Glen Canyon, Dam and Lees Ferry, northeastern Arizona, 1998-99  

USGS Publications Warehouse

The productivity of the trout fishery in the tailwater reach of the Colorado River downstream from Glen Canyon Dam depends on the productivity of lower trophic levels. Photosynthesis and respiration are basic biological processes that control productivity and alter pH and oxygen concentration. During 1998?99, data were collected to aid in the documentation of short- and long-term trends in these basic ecosystem processes in the Glen Canyon reach. Dissolved-oxygen, temperature, and specific-conductance profile data were collected monthly in the forebay of Glen Canyon Dam to document the status of water chemistry in the reservoir. In addition, pH, dissolved-oxygen, temperature, and specific-conductance data were collected at five sites in the Colorado River tailwater of Glen Canyon Dam to document the daily, seasonal, and longitudinal range of variation in water chemistry that could occur annually within the Glen Canyon reach.

Flynn, Marilyn E.; Hart, Robert J.; Marzolf, G. Richard; Bowser, Carl J.




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...


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

E-print Network

with pH manipulation experiments and with data from two lake surveys. We hypothesized that: (1) light decrease among lakes with increasing pH. In experiments with filtered lake water both initial light and chemical composition of inland waters. Keywords Dissolved organic matter Á Light absorption Á pH Á Lakes Á

Pace, Michael L.


Dissolved oxygen and pH relationships in northern Australian mangrove waterways  

SciTech Connect

Consistent, highly significant linear correlations (R2 greater than or equal to 0.8) between pH and dissolved oxygen levels have been found in northern Australian mangrove waterways. These properties seem to be influenced by dissolved organic matter, mainly polyphenolic compounds, present in the creeks and tidal channel waters.

Boto, K.G.; Bunt, J.S.



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.




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....



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...


Conductance Regulator Bicarbonate Conductance and pH Regulatory Capability of Cystic Fibrosis Transmembrane  

E-print Network

Conductance Regulator Bicarbonate Conductance and pH Regulatory Capability of Cystic Fibrosis Bicarbonate conductance and pH regulatory capability of cystic fibrosis transmembrane conductance regulator J0 of California, Berkeley, CA 94720 Communicated by Hans H. Ussing, February 28, 1994 ABSTRACT The cystic fibrosis

Machen, Terry E.


Monitoring pH and dissolved oxygen in mammalian cell culture using optical sensors  

Microsoft Academic Search

Here, we have studied two parameters critical to process control in mammalian cell culture; dissolved oxygen (dO2) and pH, measured with fluorescent sensors thus allowing the study of the metabolic state of cells in culture without removing\\u000a or damaging cells during cultivation. Two cell lines, namely, NS0 and CHO were batch-grown in 24-well plates at different\\u000a serum concentrations with the

Mariam Naciri; Darrin Kuystermans; Mohamed Al-Rubeai



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

Microsoft Academic Search

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

Charles A. Cravotta III; Mary Kay Trahan



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.



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



Development of a Multianalyte Biosensor on a Single Chip to Monitor pH and Dissolved Oxygen  

Microsoft Academic Search

A hydrogel microarray biosensor has been fabricated to monitor pH and dissolved oxygen on the same chip. Precursor solutions with pH and oxygen sensitive fluorophores are injected into microchannels, which were etched into a PDMS mold. UV light is applied through a photomask for three seconds, curing the hydrogel solution and creating a microarray sensor. An optical system consisting of

Sarah C. Jeffords


Interactions Between Dissolved Oxygen, pH, and Temperature at Lake Merritt, Oakland, CA  

NASA Astrophysics Data System (ADS)

Lake Merritt is a saltwater tidal lagoon that forms a portion of a wildlife refuge in downtown Oakland, California. In the evening, a series of lamps strewn along its perimeter dubbed poetically a "Necklace of Lights" illuminates the night sky. By contrast, local residents describe the lake's water as having a foul odor, peculiar appearance, and being full of debris. Thus, our team has investigated many areas in and around Lake Merritt in the interest of assessing Lake Merritt's water quality. We made measurements of dissolved oxygen, pH, and temperature at twelve sites along the edge of the lake and six additional locations throughout the open waters. We then used these measurements to formulate a water quality index (WQI) using guidelines provided by the U.S. Geological Survey (U.S.G.S.). Because we focus on three measures, our water quality index is weighted differently from the U.S.G.S. index. Our index is weighted as follows: 0.5 for dissolved oxygen, 0.3 for pH, and 0.2 for temperature. The index is based on a 100-point scale that allows us to compare sites and determine the relative quality of the water. In addition, we used a special device to create digital images of columns of sampled water, which were then analyzed to determine the degree of water coloration due to dissolved material and algae content. We then used results of this analysis technique to determine the relationship between the color profile and the physical and chemical characteristic of the water. We devised this new strategy to measure water turbidity because we could not use Secchi discs, given the shallowness of the lake. Overall, preliminary analysis of our data indicates that the WQIs tend to be higher near tidal gates, where the lake receives water from the San Francisco Bay via an inlet. These results raise the immediate concern that water is not effectively being circulated throughout the entire lake.

Guzman, A.; Liang, J.; Mack, T.; Majors, A.; Ngilbus, K.; Pratt, D.; Unigarro, A.



Effects of pH, dissolved oxygen, and ionic strength on the survival of Escherichia coli O157:H7 in organic acid solutions.  


The ability of Escherichia coli O157:H7 to survive in acidified vegetable products is of concern because of previously documented outbreaks associated with fruit juices. A study was conducted to determine the survival of E. coli O157:H7 in organic acids at pH values typical of acidified vegetable products (pH 3.2 and 3.7) under different dissolved oxygen conditions (< or = 0.05 and 5 mg/liter) and a range of ionic strengths (0.086 to 1.14). All solutions contained 20 mM gluconic acid, which was used as a noninhibitory low pH buffer to compare the individual acid effect to that of pH alone on the survival of E. coli O157:H7. E. coli O157:H7 cells challenged in buffered solution with ca. 5-mg/liter dissolved oxygen (present in tap water) over a range of ionic strengths at pH 3.2 exhibited a decrease in survival over 6 h at 30 degrees C as the ionic strength was increased. Cells challenged in 40 mM protonated L-lactic and acetic acid solutions with ionic strength of 0.684 achieved a > 4.7-log CFU/ml reduction at pH 3.2. However, under oxygen-limiting conditions in an anaerobic chamber, with < or = 0.05-mg/ liter oxygen, E. coli O157:H7 cells showed < or = 1.55-log CFU/ml reduction regardless of pH, acid type, concentration, or ionic strength. Many acid and acidified foods are sold in hermetically sealed containers with oxygen-limiting conditions. Our results demonstrate that E. coli O157:H7 may survive better than previously expected from studies with acid solutions containing dissolved oxygen. PMID:19244891

Kreske, Audrey C; Bjornsdottir, Kristin; Breidt, Fred; Hassan, Hosni



Fertilization and pH effects on processes and mechanisms controlling dissolved inorganic phosphorus in soils  

NASA Astrophysics Data System (ADS)

We used of a set of mechanistic adsorption models (1-pK TPM, ion exchange and Nica-Donnan) within the framework of the component additive (CA) approach in an attempt to determine the effect of repeated massive application of inorganic P fertilizer on the processes and mechanisms controlling the concentration of dissolved inorganic phosphorus (DIP) in soils. We studied the surface layer of a Luvisol with markedly different total concentrations of inorganic P as the result of different P fertilizer history (i.e. massive or no application for 40 years). Soil pH was made to vary from acid to alkaline. Soil solutions were extracted with water and CaCl 2 (0.01 M). The occurrence of montmorillonite led us to determine the binding properties of P and Ca ions for this clay mineral. Satisfactory results were obtained using generic values for model parameters and soil-specific ones, which were either determined directly by measurements or estimated from the literature. We showed that adsorption largely controlled the variations of DIP concentration and that, because of kinetic constrains, only little Ca-phosphates may be precipitated under alkaline conditions, particularly in the P fertilized treatment. The mineral-P pool initially present in both P treatments did not dissolve significantly during the course of the experiments. The adsorption of Ca ions onto soil minerals also promoted adsorption of P ions through electrostatic interactions. The intensity of the mechanism was high under neutral to alkaline conditions. Changes in DIP concentration as a function of these environmental variables can be related to changes in the contribution of the various soil minerals to P adsorption. The extra P adsorbed in the fertilized treatment compared with the control treatment was mainly adsorbed onto illite. This clay mineral was the major P-fixing constituent from neutral to alkaline pH conditions, because the repulsion interactions between deprotonated hydroxyl surface sites and P ions were sufficiently counterbalanced by Ca ions. The drastic increase of DIP observed at acid pH was due to the effect of the lower concentration of surface sites of Fe oxides and kaolinite. In addition to confirming the validity of our approach to model DIP concentrations in soils, the present investigation showed that adsorption was the predominant geochemical process even in the P fertilized soil, and that Ca ions can have an important promoting effect on P adsorption. However the influence of the dissolution of the mineral-P pool under field conditions remained questionable.

Devau, Nicolas; Hinsinger, Philippe; Le Cadre, Edith; Colomb, Bruno; Grard, Frdric



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

Microsoft Academic Search

We describe a new device with parallel optical measurement of dissolved oxygen (DO) and pH in up to nine shake flasks applicable\\u000a in any conventional shaking incubator. Measurement ranges are 0500% of air saturation for oxygen and 5.58.5 for pH. It was\\u000a used to characterize growth profiles of different l-lysine producing strains of Corynebacterium glutamicum, of Saccharomyces cerevisiae and of

Konstantin Schneider; Verena Schtz; Gernot Thomas John; Elmar Heinzle




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...


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

USGS Publications Warehouse

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

Clark, Melanie L.; Davidson, Seth L.



Specific conductance and dissolved chloride concentrations of freshwater aquifers and streams in petroleum producing areas in Mississippi  

USGS Publications Warehouse

Specific conductance and dissolved chloride reconnasissance sampling was conducted in six oil-producing areas of Mississippi during periods of low streamflow in 1980 and 1981. Water samples were collected at 224 ground-water and 190 suface-water sites. Samples from 55 surface-water and 17 ground-water sites contained dissolved chloride concentrations in excess of 100 milligrams per liter. All data collected are presented in tables without interpretation. (USGS)

Kalkhoff, S.J.



Effects of pH and dissolved oxygen on cellulose production by Acetobacter xylinum BRC5 in agitated culture.  


Acetobacter xylinum BRC5 was cultivated in a jar fermentor using glucose as the sole carbon source. Strain BRC5 oxidized almost all of the glucose to gluconic acid; thereafter, it biosynthesized cellulose by utilizing gluconic acid accumulated in the broth. The optimal pH for metabolizing glucose to gluconic acid was 4.0, while a pH of 5.5 was preferred for cell growth and cellulose production from the accumulated gluconic acid in the medium. Shifting the pH from 4.0 to 5.5 during the cellulose production phase in batch cultures improved cellulose production and reduced the total fermentation time, compared to batch cultures at constant pH. In constant fed-batch culture, 10 g/l of cellulose was obtained from 40 g/l of glucose, a yield which was approximately 2-fold higher than in batch culture with the same initial glucose concentration, even without control of the level of dissolved oxygen. The highest cellulose yield was obtained in fed-batch cultures in which the dissolved oxygen concentration was controlled at 10% saturation. Control of pH and dissolved oxygen to optimal levels was effective for improving the production rate and yield of cellulose, to achieve a high cellulose productivity of 0.3 g cellulose/l x h. Approximately 15 g/l of cellulose was considered to be the highest yield obtainable using conventional fermentors because the culture broth then became too viscous to allow satisfactory aeration. PMID:16232595

Hwang, J W; Yang, Y K; Hwang, J K; Pyun, Y R; Kim, Y S



The Molecular Composition of Dissolved Organic Matter in Forest Soils as a Function of pH and Temperature.  


We examined the molecular composition of forest soil water during three different seasons at three different sites, using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS). We examined oxic soils and tested the hypothesis that pH and season correlate with the molecular composition of dissolved organic matter (DOM). We used molecular formulae and their relative intensity from ESI-FT-ICR-MS for statistical analysis. Applying unconstrained and constrained ordination methods, we observed that pH, dissolved organic carbon (DOC) concentration and season were the main factors correlating with DOM molecular composition. This result is consistent with a previous study where pH was a main driver of the molecular differences between DOM from oxic rivers and anoxic bog systems in the Yenisei River catchment. At a higher pH, the molecular formulae had a lower degree of unsaturation and oxygenation, lower molecular size and a higher abundance of nitrogen-containing compounds. These characteristics suggest a higher abundance of tannin connected to lower pH that possibly inhibited biological decomposition. Higher biological activity at a higher pH might also be related to the higher abundance of nitrogen-containing compounds. Comparing the seasons, we observed a decrease in unsaturation, molecular diversity and the number of nitrogen-containing compounds in the course of the year from March to November. Temperature possibly inhibited biological degradation during winter, which could cause the accumulation of a more diverse compound spectrum until the temperature increased again. Our findings suggest that the molecular composition of DOM in soil pore waters is dynamic and a function of ecosystem activity, pH and temperature. PMID:25793306

Roth, Vanessa-Nina; Dittmar, Thorsten; Gaupp, Reinhard; Gleixner, Gerd



The Molecular Composition of Dissolved Organic Matter in Forest Soils as a Function of pH and Temperature  

PubMed Central

We examined the molecular composition of forest soil water during three different seasons at three different sites, using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS). We examined oxic soils and tested the hypothesis that pH and season correlate with the molecular composition of dissolved organic matter (DOM). We used molecular formulae and their relative intensity from ESI-FT-ICR-MS for statistical analysis. Applying unconstrained and constrained ordination methods, we observed that pH, dissolved organic carbon (DOC) concentration and season were the main factors correlating with DOM molecular composition. This result is consistent with a previous study where pH was a main driver of the molecular differences between DOM from oxic rivers and anoxic bog systems in the Yenisei River catchment. At a higher pH, the molecular formulae had a lower degree of unsaturation and oxygenation, lower molecular size and a higher abundance of nitrogen-containing compounds. These characteristics suggest a higher abundance of tannin connected to lower pH that possibly inhibited biological decomposition. Higher biological activity at a higher pH might also be related to the higher abundance of nitrogen-containing compounds. Comparing the seasons, we observed a decrease in unsaturation, molecular diversity and the number of nitrogen-containing compounds in the course of the year from March to November. Temperature possibly inhibited biological degradation during winter, which could cause the accumulation of a more diverse compound spectrum until the temperature increased again. Our findings suggest that the molecular composition of DOM in soil pore waters is dynamic and a function of ecosystem activity, pH and temperature. PMID:25793306

Roth, Vanessa-Nina; Dittmar, Thorsten; Gaupp, Reinhard; Gleixner, Gerd



Evaluation of Total Dissolved Solids and Specific Conductance Water Quality Targets with Paired Single-Species and Mesocosm Community Exposures  

EPA Science Inventory

Isolated single-species exposures were conducted in parallel with 42 d mesocosm dosing studies that measured in-situ and whole community responses to different recipes of excess total dissolved solids (TDS). The studies were conducted with cultured species and native taxa from mo...


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



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.



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


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



In Situ Sensor Technology for Simultaneous Spectrophotometric Measurements of Seawater Total Dissolved Inorganic Carbon and pH.  


A new, in situ sensing system, Channelized Optical System (CHANOS), was recently developed to make high-resolution, simultaneous measurements of total dissolved inorganic carbon (DIC) and pH in seawater. Measurements made by this single, compact sensor can fully characterize the marine carbonate system. The system has a modular design to accommodate two independent, but similar measurement channels for DIC and pH. Both are based on spectrophotometric detection of hydrogen ion concentrations. The pH channel uses a flow-through, sample-indicator mixing design to achieve near instantaneous measurements. The DIC channel adapts a recently developed spectrophotometric method to achieve flow-through CO2 equilibration between an acidified sample and an indicator solution with a response time of only ?90 s. During laboratory and in situ testing, CHANOS achieved a precision of 0.0010 and 2.5 ?mol kg(-1) for pH and DIC, respectively. In situ comparison tests indicated that the accuracies of the pH and DIC channels over a three-week time-series deployment were 0.0024 and 4.1 ?mol kg(-1), respectively. This study demonstrates that CHANOS can make in situ, climatology-quality measurements by measuring two desirable CO2 parameters, and is capable of resolving the CO2 system in dynamic marine environments. PMID:25720851

Wang, Zhaohui Aleck; Sonnichsen, Frederick N; Bradley, Albert M; Hoering, Katherine A; Lanagan, Thomas M; Chu, Sophie N; Hammar, Terence R; Camilli, Richard



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.; Jrgens, K.



Multiplex bacterial growth monitoring in 24-well microplates using a dual optical sensor for dissolved oxygen and pH.  


Non-invasive, simultaneous optical monitoring of oxygen and pH during bacterial cultivation in 24-well microplates is presented using an integrated dual sensor for dissolved oxygen and pH values. The dual sensor is based on oxygen-sensitive organosilica microparticles and pH-sensitive microbeads from a polymethacrylate derivative embedded into a polyurethane hydrogel. The readout is based on a phase-domain fluorescence lifetime-based method referred to as modified frequency domain dual lifetime referencing using a commercially available detector system for 24-well microplates. The sensor was used for monitoring the growth of Pseudomonas putida bacterial cultures. The method is suitable for parallelized, miniaturized bioprocessing, and cell-based high-throughput screening applications. PMID:18383124

Kocincov, Anna S; Nagl, Stefan; Arain, Sarina; Krause, Christian; Borisov, Sergey M; Arnold, Matthias; Wolfbeis, Otto S



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.



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


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. PMID:24349823

Li, Haiyan; Liu, Liang; Li, Mingyi; Zhang, Xiaoran



Biochar-Induced Changes in Soil Hydraulic Conductivity and Dissolved Nutrient Fluxes Constrained by Laboratory Experiments  

PubMed Central

The addition of charcoal (or biochar) to soil has significant carbon sequestration and agronomic potential, making it important to determine how this potentially large anthropogenic carbon influx will alter ecosystem functions. We used column experiments to quantify how hydrologic and nutrient-retention characteristics of three soil materials differed with biochar amendment. We compared three homogeneous soil materials (sand, organic-rich topsoil, and clay-rich Hapludert) to provide a basic understanding of biochar-soil-water interactions. On average, biochar amendment decreased saturated hydraulic conductivity (K) by 92% in sand and 67% in organic soil, but increased K by 328% in clay-rich soil. The change in K for sand was not predicted by the accompanying physical changes to the soil mixture; the sand-biochar mixture was less dense and more porous than sand without biochar. We propose two hydrologic pathways that are potential drivers for this behavior: one through the interstitial biochar-sand space and a second through pores within the biochar grains themselves. This second pathway adds to the porosity of the soil mixture; however, it likely does not add to the effective soil K due to its tortuosity and smaller pore size. Therefore, the addition of biochar can increase or decrease soil drainage, and suggests that any potential improvement of water delivery to plants is dependent on soil type, biochar amendment rate, and biochar properties. Changes in dissolved carbon (C) and nitrogen (N) fluxes also differed; with biochar increasing the C flux from organic-poor sand, decreasing it from organic-rich soils, and retaining small amounts of soil-derived N. The aromaticity of C lost from sand and clay increased, suggesting lost C was biochar-derived; though the loss accounts for only 0.05% of added biochar-C. Thus, the direction and magnitude of hydraulic, C, and N changes associated with biochar amendments are soil type (composition and particle size) dependent. PMID:25251677

Barnes, Rebecca T.; Gallagher, Morgan E.; Masiello, Caroline A.; Liu, Zuolin; Dugan, Brandon



Rates of zinc and trace metal release from dissolving sphalerite at pH 2.0-4.0  

USGS Publications Warehouse

High-Fe and low-Fe sphalerite samples were reacted under controlled pH conditions to determine nonoxidative rates of release of Zn and trace metals from the solid-phase. The release (solubilization) of trace metals from dissolving sphalerite to the aqueous phase can be characterized by a kinetic distribution coefficient, (Dtr), which is defined as [(Rtr/X(tr)Sph)/(RZn/X(Zn) Sph)], where R is the trace metal or Zn release rate, and X is the mole fraction of the trace metal or Zn in sphalerite. This coefficient describes the relationship of the sphalerite dissolution rate to the trace metal mole fraction in the solid and its aqueous concentration. The distribution was used to determine some controls on metal release during the dissolution of sphalerite. Departures from the ideal Dtr of 1.0 suggest that some trace metals may be released via different pathways or that other processes (e.g., adsorption, solubility of trace minerals such as galena) affect the observed concentration of metals. Nonoxidative sphalerite dissolution (mediated by H+) is characterized by a "fast" stage in the first 24-30 h, followed by a "slow" stage for the remainder of the reaction. Over the pH range 2.0-4.0, and for similar extent of reaction (reaction time), sphalerite composition, and surface area, the rates of release of Zn, Fe, Cd, Cu, Mn and Pb from sphalerite generally increase with lower pH. Zinc and Fe exhibit the fastest rates of release, Mn and Pb have intermediate rates of release, and Cd and Cu show the slowest rates of release. The largest variations in metal release rates occur at pH 2.0. At pH 3.0 and 4.0, release rates show less variation and appear less dependent on the metal abundance in the solid. For the same extent of reaction (100 h), rates of Zn release range from 1.53 ?? 10-11 to 5.72 ?? 10-10 mol/m2/s; for Fe, the range is from 4.59 ?? 10-13 to 1.99 ?? 10-10 mol/m2/s. Trace metal release rates are generally 1-5 orders of magnitude slower than the Zn or Fe rates. Results indicate that the distributions of Fe and Cd are directly related to the rate of sphalerite dissolution throughout the reaction at pH 3.0 and 4.0 because these two elements substitute readily into sphalerite. These two metals are likely to be more amenable to usage in predictive acid dissolution models because of this behavior. The Pb distribution shows no strong relation to sphalerite dissolution and appears to be controlled by pH-dependent solubility, most likely related to trace amounts of galena. The distribution of Cu is similar to that of Fe but is the most-dependent of all metals on its mole fraction ratio (Zn:Cu) in sphalerite. The Mn distributions suggest an increase in the rate of Mn release relative to sphalerite dissolution occurs in low Mn samples as pH increases. The Mn distribution in high Mn samples is nearly independent of pH and sphalerite dissolution at pH 2.0 but shows a dependence on these two parameters at higher pH (3.0-4.0).

Stanton, M.R.; Gemery-Hill, P. A.; Shanks, W. C., III; Taylor, C.D.



Marine microbial production of dimethylsulfide from dissolved dimethylsulfoniopropionate. Ph. D. Thesis  

SciTech Connect

Dimethylsulfide (DMS) plays a central role in the transfer of sulfur from the ocean to the atmosphere and ultimately to land. The most abundant volatile organosulfur compound in seawater, DMS is believed to account for the bulk of the sea-to-air biogenic sulfur flux. DMS has also been implicated as the major precursor of submicron-sized sulfate aerosol over the ocean. This aerosol acts as an effective site for cloud droplet condensation suggesting a possibly important role for DMS in marine cloud formation. In the ocean, the precursor of DMS is presumed to be the zwitterionic sulfonium compound dimethylsulfoniopropionate (DMSP), a common osmoticum in certain classes of marine algae. While some algae can cleave DMSP intracellularly to form DMS, correlation of DMS concentrations with indicators of algal productivity on a local scale is poor. This thesis focuses on an alternative pathway of DMS formation: microbial cleavage of dissolved (extracellular) DMSP. In laboratory studies, bacteria able to cleave DMSP to form DMS were isolated from seawater by a DMSP enrichment technique, and the kinetics of DMSP uptake and DMS production were examined closely in pure cultures of a bacterial isolate from the Sargasso Sea. The isolate could grow with both DMSP and acrylic acid, one of the products of DMSP cleavage, as the sole source of carbon and energy, and the enzyme catalyzing DMSP cleavage appeared to be induced by both of these compounds. Kinetic parameters were estimated for DMSP uptake and cleavage by whole cells. Comparison of the 16S rRNA sequence of this isolate with that of known eubacteria showed that it was most closely related to Erythrobacter longus, an aerobic, bacteriochlorophyll-containing member of the alpha proteobacteria.

Ledyard, K.M.



Effects of pH, dissolved oxygen, and aqueous ferrous iron on the adsorption of arsenic to lepidocrocite.  


The adsorption of arsenic to iron oxyhydroxides strongly depends on water chemistry. Iron(III) oxyhydroxides can also participate in the oxidation of As(III) to As(V), which changes arsenic's toxicity and adsorption behavior. As(III) and As(V) adsorption to lepidocrocite (?-FeOOH) were examined in batch experiments that explored the effects of lepidocrocite dose, pH, availability of dissolved oxygen, and the presence of aqueous Fe(II) on adsorption. Lepidocrocite is an iron oxyhydroxide found in soils, and it is one of the major products of iron electrocoagulation for water treatment. A surface complexation model was able to describe the adsorption of both As(III) and As(V) to lepidocrocite over a broad range of conditions. The concentration and oxidation states of arsenic in solution were measured over the course of the reactions. At both oxic and anoxic conditions, As(III) was oxidized to As(V) in systems that contained lepidocrocite together with Fe(II); this oxidation led to overall enhanced arsenic adsorption at near neutral pH. With oxygen the pH-dependent generation of oxidants from the Fenton reaction drove the As(III) oxidation. In the absence of oxygen the As(III) was probably oxidized by Fe(III) in lepidocrocite that had become more reactive upon reaction with Fe(II). PMID:25746186

Wang, Lin; Giammar, Daniel E



Impact of pH, dissolved inorganic carbon, and polyphosphates for the initial stages of water corrosion of copper surfaces investigated by AFM and NEXAFS  

EPA Science Inventory

Nanoscale studies at the early stages of the exposure of copper surfaces after systematic treatments in synthesized water solutions can provide useful information about corrosion processes. The corrosion and passivation of copper surfaces as influenced by pH, dissolved inorganic ...


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


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

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



Improved curdlan fermentation process based on optimization of dissolved oxygen combined with pH control and metabolic characterization of Agrobacterium sp. ATCC 31749.  


A significant problem in scale-down cultures, rarely studied for metabolic characterization and curdlan-producing Agrobacterium sp. ATCC 31749, is the presence of dissolved oxygen (DO) gradients combined with pH control. Constant DO, between 5% and 75%, was maintained during batch fermentations by manipulating the agitation with PID system. Fermentation, metabolic and kinetic characterization studies were conducted in a scale-down system. The curdlan yield, intracellular nucleotide levels and glucose conversion efficiency into curdlan were significantly affected by DO concentrations. The optimum DO concentrations for curdlan production were 45-60%. The average curdlan yield, curdlan productivity and glucose conversion efficiency into curdlan were enhanced by 80%, 66% and 32%, respectively, compared to that at 15% DO. No apparent difference in the gel strength of the resulting curdlan was detected. The comparison of curdlan biosynthesis and cellular nucleotide levels showed that curdlan production had positive relationship with intracellular levels of UTP, ADP, AMP, NAD(+), NADH and UDP-glucose. The curdlan productivity under 45% DO and 60% DO was different during 20-50 h. However, after 60 h curdlan productivity of both conditions was similar. On that basis, a simple and reproducible two-stage DO control process for curdlan production was developed. Curdlan production yield reached 42.8 g/l, an increase of 30% compared to that of the single agitation speed control process. PMID:21739265

Zhang, Hong-Tao; Zhan, Xiao-Bei; Zheng, Zhi-Yong; Wu, Jian-Rong; English, Nike; Yu, Xiao-Bin; Lin, Chi-Chung



A Dilute Standard for pH, Conductivity, and Acid Neutralizing Capacity Measurement  

Microsoft Academic Search

A quality control standard suitable for assessing measurement errors of pH, conductivity, and acid neutralizing capacity (ANC, also known as titration alkalinity) of dilute, neutral pH waters has been developed and tested for field and laboratory use in ecological studies. A dilute phosphate standard is prepared as a 100-fold dilution (by mass) of 0.025 mol kg (of solvent) KH2PO4 and

Richard C. Metcalf; David V. Peck



The Impact of Environmental Factors on Changes in pH and Dissolved Oxygen Levels in Pond Water: A Probeware based activity  

NSDL National Science Digital Library

This teaching resource was developed by a K-12 science teacher in the American Physiologycal Society's 2006 Frontiers in Physiology Program. For more information on this program, please visit The purpose of this laboratory activity is to have students develop an experiment that tests the impact of environmental factors on levels of pH and dissolved oxygen in pond water using probeware.

Maria Winston (Edgemont Junior/Senior High School)



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



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

USGS Publications Warehouse

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

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



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


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

Zhang, Xiang-Shang; Zhang, Long-Jun



Ionic Conductance Changes in Voltage Clamped Crayfish Axons at Low pH  

PubMed Central

Giant axons from the crayfish have been voltage clamped with an axial wire system. General characterististics of observed ionic currents under normal conditions are similar to those measured in other giant axons and in nodes of Ranvier. As the pH of the external bath is lowered below 7, a marked, reversible slowing of potassium currents is seen with little effect on sodium currents. The steady-state potassium conductance-voltage curve is shifted along the voltage axis in a manner consistent with the development of a hyperpolarizing surface charge. Results suggest that this potential shift accounts for part, though not all, of the observed increase in ?n. From the behavior of the kinetics of the delayed current with external pH these alterations in potassium conductance are attributed to the titration of a histidine imidazole residue of a membrane protein. Chemical modification of histidine by carbethoxylation at pH 6 slows and strongly depresses potassium currents. The results suggest that in addition to the introduction of electrostatic forces, possibly resulting from a hyperpolarizing surface charge, protonation of a histidine group at low pH also alters the nonelectrostatic chemical interactions determining the ease with which potassium gates open and close. The evidence indicates that the modified histidine residue is closely associated with the membrane components involved in the control of potassium conductance. PMID:4443794

Shrager, Peter



Lab-scale fermentation tests of microchip with integrated electrochemical sensors for pH, temperature, dissolved oxygen and viable biomass concentration.  


This article shows the development and testing of a microchip with integrated electrochemical sensors for measurement of pH, temperature, dissolved oxygen and viable biomass concentration under yeast cultivation conditions. Measurements were done both under dynamic batch conditions as well as under prolonged continuous cultivation conditions. The response of the sensors compared well with conventional measurement techniques. The biomass sensor was based on impedance spectroscopy. The results of the biomass sensor matched very well with dry weight measurements and showed a limit of detection of approximately 1 g/L. The dissolved oxygen concentration was monitored amperometrically using an ultra-microelectrode array, which showed an accuracy of approximately 0.2 mg/L and negligible drift. pH was monitored using an ISFET with an accuracy well below 0.1 pH unit. The platinum thin-film temperature resistor followed temperature changes with approximately 0.1 degrees C accuracy. The dimensions of the multi sensor chip are chosen as such that it is compatible with the 96-well plate format. PMID:17929319

Krommenhoek, Erik E; van Leeuwen, Michiel; Gardeniers, Han; van Gulik, Walter M; van den Berg, Albert; Li, Xiaonan; Ottens, Marcel; van der Wielen, Luuk A M; Heijnen, Joseph J



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

Microsoft Academic Search

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

R. A. Ponce; N. S. Bloom



The synergistic effects of dissolved oxygen and pH on N2O production in biological domestic wastewater treatment under nitrifying conditions.  


Nitrous oxide (N2O) is a potent greenhouse gas, which is produced during nitrifying and denitrifying processes. Some factors and mechanisms affecting N2O emission have been reported in previous literature, but wastewater biological nitrification is accompanied by a dynamic process of dissolved oxygen (DO) consumption and pH reduction, it is more meaningful to study the synergistic effects between DO and pH on N2O production. In this study, the synergistic effects between DO and pH on N2O production were investigated with real domestic wastewater. The results showed that high DO levels and a high pH could improve the oxidation ratio of [Formula: see text] and the production ratio of [Formula: see text] while effectively reducing the accumulation ratio of N2O. The [Formula: see text] was a prerequisite for nitrifier denitrification; when [Formula: see text] was oxidized completely, there would be no N2O production and an even higher concentration of [Formula: see text] The pH factor is shown to directly affect N2O emission, although free ammonia and free nitrous acid which changed with pH had no correlation with N2O emission. There were two reasons: (1) pH can influence the flow direction of electrons afforded by NH2OH oxidation; at high pH, electrons were mainly used for combining H(+) and O2 (O2?+?4H(+)?+?4e(-)?=?2H2O), the accumulation of [Formula: see text] cannot be a result of denitrification, and a higher DO can get more electrons to prefer [Formula: see text] and (2) [Formula: see text] was the prerequisite for NH2OH oxidation, since NH2OH oxidation process was the way to provide electrons for nitrifier denitrification. PMID:25619120

Li, Pengzhang; Wang, Shuying; Peng, Yongzhen; Liu, Yue; He, Janzhong



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

Microsoft Academic Search

In this study, we examine the impact of increasing concentrations of dissolved organic carbon (DOC) on the recovery from acidification for 66 lakes in Southern Sweden. The lakes are small, weakly buffered, and have all been affected by acidifying deposition. A majority of the lakes (?75%) showed an increase in DOC concentrations between 1990 and 2008. The method used in

Martin Erlandsson; Neil Cory; Stephan Khler; Kevin Bishop



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

Microsoft Academic Search

In this study, we examine the impact of increasing concentrations of dissolved organic carbon (DOC) on the recovery from acidification for 66 lakes in Southern Sweden. The lakes are small, weakly buffered, and have all been affected by acidifying deposition. A majority of the lakes (75%) showed an increase in DOC concentrations between 1990 and 2008. The method used in

Martin Erlandsson; Neil Cory; Stephan Khler; Kevin Bishop



Ensuring PhD development of responsible conduct of research behaviors: who's responsible?  


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

Titus, Sandra L; Ballou, Janice M



Continuous-flow electrophoresis: Membrane-associated deviations of buffer pH and conductivity  

NASA Technical Reports Server (NTRS)

The deviations in buffer pH and conductivity which occur near the electrode membranes in continuous-flow electrophoresis were studied in the Beckman charged particle electrophoresis system and the Hanning FF-5 preparative electrophoresis instrument. The nature of the membranes separating the electrode compartments from the electrophoresis chamber, the electric field strength, and the flow rate of electrophoresis buffer were all found to influence the formation of the pH and conductivity gradients. Variations in electrode buffer flow rate and the time of electrophoresis were less important. The results obtained supported the hypothesis that a combination of Donnan membrane effects and the differing ionic mobilities in the electrophoresis buffer was responsible for the formation of the gradients. The significance of the results for the design and stable operation of continuous-flow electrophoresis apparatus was discussed.

Smolka, A. J. K.; Mcguire, J. K.



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


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

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



Coupling effect of pH and dissolved oxygen in water column on nitrogen release at water-sediment interface of Erhai Lake, China  

NASA Astrophysics Data System (ADS)

Nitrogen (N), in the form of ammonia or nitrate, is a key limiting nutrient in many aquatic systems. Under certain environmental conditions it can be released from sediments into overlying water, which may have significant impact on water quality and result in continuous eutrophication. However, few studies have examined the long-term (nearly two months) coupling effect of environmental parameters on N dynamics at the sediment-water interface. This is particularly pertinent to improve the understanding of lake eutrophication processes. This study examines the coupling effects of pH and dissolved oxygen (DO) on N release at the sediment-water interface for the shallow Erhai Lake in China, and analyzes recent changes in environmental conditions and water quality to predict the risk of nitrogen release from sediment in the near future. Experimental results indicated that under anaerobic condition (DO?1mg/L) and lower pH (pH=6), ammonium was easily released into overlying water, potentially triggering algal blooms. Conversely aerobic conditions (DO=8-10mg/L) and higher pH (pH=10) promoted nitrate release from sediment. The study also discusses possible mechanisms about the nitrogen dynamics at the sediment-water interface. Considering the overall effects of ammonium and nitrate on the trophic status of the water column, the recommended environmental condition in overlying water should be pH of around 8 under aerobic conditions. Based on the study findings, the nitrogen balance at the water-sediment interface was evaluated for different environmental conditions. Analysis of environmental conditions and water quality during 1992-2010 shows that present environmental conditions are not conducive to the release of nutrients from sediment, thereby protecting the water quality from serious endogenous pollution. However, the risk of nitrogen release from sediment sources might increase if environmental conditions change.

Zhang, Li; Wang, Shengrui; Wu, Zhihao



Effects of pH, dissolved oxygen, and ionic strength on the survival of Escherichia coli O157:H7 in organic acid solutions  

Technology Transfer Automated Retrieval System (TEKTRAN)

The ability of Escherichia coli O157:H7 to survive in acidified vegetable products is of concern because of previously documented outbreaks associated with fruit juices. A study was conducted to determine the survival of E. coli O157:H7 in organic acids at pH values typical of acidified vegetable pr...


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. Cot; Michael V. Pishko



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.



In situ optimization of pH for parts-per-billion electrochemical detection of dissolved hydrogen sulfide using boron doped diamond flow electrodes.  


A novel electrochemical approach to the direct detection of hydrogen sulfide (H2S), in aqueous solutions, covering a wide pH range (acid to alkali), is described. In brief, a dual band electrode device is employed, in a hydrodynamic flow cell, where the upstream electrode is used to controllably generate hydroxide ions (OH(-)), which flood the downstream detector electrode and provide the correct pH environment for complete conversion of H2S to the electrochemically detectable, sulfide (HS(-)) ion. All-diamond, coplanar conducting diamond band electrodes, insulated in diamond, were used due to their exceptional stability and robustness when applying extreme potentials, essential attributes for both local OH(-) generation via the reduction of water, and for in situ cleaning of the electrode, post oxidation of sulfide. Using a galvanostatic approach, it was demonstrated the pH locally could be modified by over five pH units, depending on the initial pH of the mobile phase and the applied current. Electrochemical detection limits of 13.6 ppb sulfide were achieved using flow injection amperometry. This approach which offers local control of the pH of the detector electrode in a solution, which is far from ideal for optimized detection of the analyte of interest, enhances the capabilities of online electrochemical detection systems. PMID:25263331

Bitziou, Eleni; Joseph, Maxim B; Read, Tania L; Palmer, Nicola; Mollart, Tim; Newton, Mark E; Macpherson, Julie V



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

PubMed Central

The ability of metabolically diverse hyperthermophilic archaea to withstand high temperatures, low pHs, high sulfide concentrations, and the absence of carbon and energy sources was investigated. Close relatives of our study organisms, Methanocaldococcus jannaschii, Archaeoglobus profundus, Thermococcus fumicolans, and Pyrococcus sp. strain GB-D, are commonly found in hydrothermal vent chimney walls and hot sediments and possibly deeper in the subsurface, where highly dynamic hydrothermal flow patterns and steep chemical and temperature gradients provide an ever-changing mosaic of microhabitats. These organisms (with the possible exception of Pyrococcus strain GB-D) tolerated greater extremes of low pH, high sulfide concentration, and high temperature when actively growing and metabolizing than when starved of carbon sources and electron donors/acceptors. Therefore these organisms must be actively metabolizing in the hydrothermal vent chimneys, sediments, and subsurface in order to withstand at least 24 h of exposure to extremes of pH, sulfide, and temperature that occur in these environments. PMID:16204562

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



Variation in Hydraulic Conductivity with Decreasing pH in a Biologically-Clogged Porous Medium  

NASA Astrophysics Data System (ADS)

Biological clogging can significantly lower the hydraulic conductivity of porous media, potentially helping to limit CO2 transport from geological carbon storage reservoirs. How clogging is affected by CO2 injection, however, is unclear. We used column experiments to examine how decreasing pH, a geochemical change associated with CO2 injection, will affect the hydraulic conductivity (K) of biologically clogged porous medium. Four biologically-active experiments and two control experiments were performed. Columns consisted of 1 mm2 capillary tubes filled with 105-150 ?m diameter glass beads. Artificial groundwater medium containing 1 mM glucose was pumped through the columns at a rate of 0.015 mL/min (q = 21.6 m/day; Re = 0.045). Each column was inoculated with 10^8 CFU of Pseudomonas fluorescens tagged with a green fluorescent protein; cells introduced to control columns were heat sterilized. Biomass distribution and transport was monitored using scanning laser confocal microscopy and effluent plating. Growth was allowed to occur for 5 days in medium with pH 7 in the biologically active columns. During that time, K decreased to values ranging from 10 to 27% of the average control K and effluent cell levels increased to about 10^8 CFU/mL. Next, the pH of the inflowing medium was lowered to 4 in three experiments and 5.5 in one experiment. After pH 4 medium was introduced, K increased to values ranging from 21 to 64% of the average control K and culturable cell levels in the effluent fell by about 4 log units. Confocal images show that clogging persisted in the columns at pH 4 because most of the microbial biomass remained attached to bead surfaces. In the experiment where pH was lowered to 5.5, K changed little because biological clogging remained entirely intact. The concentration of culturable cells in the effluent was also invariant. These results suggest that biomass in porous medium will largely remain in place following exposure to acidic water in a CO2 storage reservoir, particularly where buffering is able to limit the extent of acidification. 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.

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



[Variations of pH value and electrical conductivity in the Dongkemadi basin, Tanggula range].  


Investigation of meltwater chemistry may provide information to understand the significance of glacier in estimating of water provenance. Most notably, the role of electrical conductivity (EC) variation in meltwater during glacier melting season has attracted considerable attention, since this may reflect the water flux. Analyses for pH and EC in 229 bulk meltwater samples have provided information about water provenance at Dongkemadi Glacier basin, an outlet tongue from the Tanggula Pass, Tibetan Plateau. The samples were collected at 14:00 from 12th May to 27th September in 2005 at site of controlled meltwater flux. The results document the following findings. First phase of runoff was mainly supplied by snow and glacier ice meltwater, 31% and 65%, respectively, and the snow including fresh snow and winter deposited snow. Secondary phase of flux primarily was supplied by glacier ice meltwater and precipitation, but meltwater of frozen water in soil also has some contribute to flux, but only 2%. Third phase, ice bulk meltwater decreased and fresh snow meltwater increased. In different precipitation modalities variation trends of pH value and EC are following an orderd snow > rainwater > hailstone. PMID:18268996

Wang, Jian; Aihemaiti, Aximu; Ding, Yong-jian; Liu, Shi-yin; Wu, Jin-kui



An automated procedure for the simultaneous determination of specific conductance and pH in natural water samples  

USGS Publications Warehouse

An automated, continuous-flow system is utilized to determine specific conductance and pH simultaneously in natural waters. A direct electrometric procedure is used to determine values in the range pH 4-9. The specific conductance measurements are made with an electronically modified, commercially available conductivity meter interfaced to a separate module containing the readout control devices and printer. The system is designed to switch ranges automatically to accommodate optimum analysis of widely varying conductances ranging from a few ??mhos cm-1 to 15,000 ??mho cm-1. Thirty samples per hour can be analyzed. Comparison of manual and automated procedures for 40 samples showed that the average differences were 1.3% for specific conductance and 0.07 units for pH. The relative standard deviation for 25 replicate values for each of five samples was significantly less than 1% for the specific conductance determination; the standard deviation for the pH determination was ??? 0.06 pH units. ?? 1978.

Eradmann, D.E.; Taylor, H.E.



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

NASA Astrophysics Data System (ADS)

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

Bravin, Matthieu N.; Garnier, Cdric; Lenoble, Vronique; Grard, Frdric; Dudal, Yves; Hinsinger, Philippe



Theoretical constraints on the effects of pH, salinity, and temperature on clumped isotope signatures of dissolved inorganic carbon species and precipitating carbonate minerals  

NASA Astrophysics Data System (ADS)

The use of carbonate clumped isotope thermometry as a geochemical technique to determine temperature of formation of a carbonate mineral is predicated on the assumption that the mineral has attained an internal thermodynamic equilibrium. If true, then the clumped isotope signature is dependent solely upon the temperature of formation of the mineral without the need to know the isotopic or elemental composition of coeval fluids. However, anomalous signatures can arise under disequilibrium conditions that can make the estimation of temperatures uncertain by several degrees Celsius. Here we use ab initio calculations to examine the potential disequilibrium mineral signatures that may arise from the incorporation of dissolved inorganic carbon (DIC) species (predominantly aqueous carbonate and bicarbonate ions) into growing crystals without full equilibration with the crystal lattice. We explore theoretically the nature of clumping in the individual DIC species and the composite DIC pool under varying pH, salinity, temperature, and isotopic composition, and speculate about their effects upon the resultant disequilibrium clumping of the precipitates. We also calculate equilibrium clumped signatures for the carbonate minerals calcite, aragonite, and witherite. Our models indicate that each DIC species has a distinct equilibrium clumped isotope signature such that, ?47(H2CO3)>?47HCO3->?47 (equilibrium calcite)>?47 CO32-, and predict a difference between ?47HCO3- and ?47CO32->0.033 at 25 C, and that ?47 (aragonite) > ?47 (calcite) > ?47 (witherite). We define the calcite clumped crossover pH as the pH at which the composite ?47 (DIC pool) = ?47 (equilibrium calcite). If disequilibrium ?47 (calcite) is misinterpreted as equilibrium ?47 (calcite), it is possible to overestimate or underestimate the growth temperature by small but significant amounts. Increases in salinity lower the clumped crossover pH and may cause larger effects. Extreme effects of pH, salinity, and temperature, such as between cold freshwater lakes at high latitudes to hot hypersaline environments, are predicted to have sizeable effects on the clumped isotope composition of aqueous DIC pools. In order to determine the most reliable and efficient modeling methods to represent aqueous dissolved inorganic carbon (DIC) species and carbonate minerals, we performed convergence and sensitivity testing on several different levels of theory. We used 4 different techniques for modeling the hydration of DIC: gas phase, implicit solvation (PCM and SMD), explicit solvation (ion with 3 water molecules) and supermolecular clusters (ion plus 21 to 32 water molecules with geometries generated by molecular dynamics). For each solvation technique, we performed sensitivity testing by combining different levels of theory (up to 8 ab initio/hybrid methods, each with up to 5 different sizes of basis sets) to understand the limits of each technique. We looked at the degree of convergence with the most complex (and accurate) models in order to select the most reliable and efficient modeling methods. The B3LYP method combined with the 6-311++G(2d,2p) basis set with supermolecular clusters worked well.

Hill, Pamela S.; Tripati, Aradhna K.; Schauble, Edwin A.



Selective recovery of dissolved Fe, Al, Cu, and Zn in acid mine drainage based on modeling to predict precipitation pH.  


Mining activities have caused serious environmental problems including acid mine drainage (AMD), the dispersion of mine tailings and dust, and extensive mine waste. In particular, AMD contaminates soil and water downstream of mines and generally contains mainly valuable metals such as Cu, Zn, and Ni as well as Fe and Al. In this study, we investigated the selective recovery of Fe, Al, Cu, Zn, and Ni from AMD. First, the speciation of Fe, Al, Cu, Zn, and Ni as a function of the equilibrium solution pH was simulated by Visual MINTEQ. Based on the simulation results, the predicted pHs for the selective precipitation of Fe, Al, Cu, and Zn/Ni were determined. And recovery yield of metals using simulation is over 99 %. Experiments using artificial AMD based on the simulation results confirmed the selective recovery of Fe, Al, Cu, and Zn/Ni, and the recovery yields of Fe/Al/Cu/Zn and Fe/Al/Cu/Ni mixtures using Na2CO3 were 99.6/86.8/71.9/77.0 % and 99.2/85.7/73.3/86.1 %, respectively. After then, the simulation results were applied to an actual AMD for the selective recovery of metals, and the recovery yields of Fe, Al, Cu, and Zn using NaOH were 97.2, 74.9, 66.9, and 89.7 %, respectively. Based on the results, it was concluded that selective recovery of dissolved metals from AMD is possible by adjusting the solution pH using NaOH or Na2CO3 as neutralizing agents. PMID:25231736

Park, Sang-Min; Yoo, Jong-Chan; Ji, Sang-Woo; Yang, Jung-Seok; Baek, Kitae



Differences in conductance of M2 proton channels of two influenza viruses at low and high pH  

PubMed Central

The M2 protein of influenza A viruses forms a proton channel involved in modifying virion and trans Golgi pH during infection. Previous studies of the proton current using whole-cell patch clamp of mouse erythroleukaemia (MEL) cells expressing the M2 protein of the Weybridge strain provided evidence for two protonation sites, one involved in permeation, the other in activation by acid pH. The present report compares the M2 channels of two different strains of influenza virus, Weybridge (WM2) and Rostock (RM2). Whereas with external acid pH the current-voltage relations showed similar small degrees of inward rectification, a similar apparent Kd of approximately 10 ?m for proton permeation and a high selectivity for protons over Na+, the two M2 proteins differed in whole-cell conductance at low and high pH. The proton conductance of unit membrane area was on average 7-fold greater in RM2- than WM2-expressing MEL cells. At high external pH WM2 was shown previously to have small conductance for outward current at positive driving potential. In contrast, RM2 shows high conductance for outward current with high external pH, but shows small conductance for inward current with high internal pH, conditions in which WM2 shows high conductance for inward current. The different properties of the conductances due to the two channels at high pH were determined by three amino acids in their transmembrane domains. All intermediate mutants possessed one or other property and transformation of the WM2 phenotype into that of RM2 required substitution in all three residues V27I, F38L and D44N; single substitutions in RM2 effected the opposite phenotypic change. The significance of this difference for virus replication is not clear and it may be that the higher proton flux associated with RM2 is the main factor determining its increased ability to dissipate pH gradients. It is apparent, however, from the specific differences in the sidedness of the pH-induced changes in voltage dependence of the whole-cell current that this is an intrinsic property of the virus proton channel which may have parallels with regulation of other proton channels. PMID:12527729

Chizhmakov, I V; Ogden, D C; Geraghty, F M; Hayhurst, A; Skinner, A; Betakova, T; Hay, A J



Economic process to co-produce poly(?-l-lysine) and poly(l-diaminopropionic acid) by a pH and dissolved oxygen control strategy.  


This study tended to apply biorefinery of indigenous microbes to the fermentation of target-product generation through a novel control strategy. A novel strategy for co-producing two valuable homopoly(amino acid)s, poly(?-l-lysine) (?-PL) and poly(l-diaminopropionic acid) (PDAP), was developed by controlling pH and dissolved oxygen concentrations in Streptomyces albulus PD-1 fermentation. The production of ?-PL and PDAP got 29.4 and 9.6gL(-1), respectively, via fed-batch cultivation in a 5L bioreactor. What is more, the highest production yield (21.8%) of similar production systems was achieved by using this novel strategy. To consider the economic-feasibility, large-scale production in a 1t fermentor was also implemented, which would increase the gross profit of 54,243.5USD from one fed-batch bioprocess. This type of fermentation, which produces multiple commercial products from a unified process is attractive, because it will improve the utilization rate of raw materials, enhance production value and enrich product variety. PMID:25841184

Xu, Zhaoxian; Feng, Xiaohai; Sun, Zhuzhen; Cao, Changhong; Li, Sha; Xu, Zheng; Xu, Zongqi; Bo, Fangfang; Xu, Hong



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. PMID:7561747



The relationship of metals, bifenthrin, physical habitat metrics, grain size, total organic carbon, dissolved oxygen and conductivity to Hyalella sp. abundance in urban California streams.  


The objectives of this study were to determine the relationship between Hyalella sp. abundance in four urban California streams and the following parameters: (1) 8 bulk metals (As, Cd, Cr, Cu, Pb, Hg, Ni, and Zn) and their associated sediment Threshold Effect Levels (TELs); (2) bifenthrin sediment concentrations; (3) 10 habitat metrics and total score; (4) grain size (% sand, silt and clay); (5) Total Organic Carbon (TOC); (6) dissolved oxygen; and (7) conductivity. California stream data used for this study were collected from Kirker Creek (2006 and 2007), Pleasant Grove Creek (2006, 2007 and 2008), Salinas streams (2009 and 2010) and Arcade Creek (2009 and 2010). Hyalella abundance in the four California streams generally declined when metals concentrations were elevated beyond the TELs. There was also a statistically significant negative relationship between Hyalella abundance and % silt for these 4 California streams as Hyalella were generally not present in silt areas. No statistically significant relationships were reported between Hyalella abundance and metals concentrations, bifenthrin concentrations, habitat metrics, % sand, % clay, TOC, dissolved oxygen and conductivity. The results from this study highlight the complexity of assessing which factors are responsible for determining the abundance of amphipods, such as Hyalella sp., in the natural environment. PMID:23379940

Hall, Lenwood W; Anderson, Ronald D



Dissolved Organic Carbon Concentrations in Tempe Town Lake: biogDissolved Organic Carbon Concentrations in Tempe Town Lake: biogeochemical & hydrologic processeseochemical & hydrologic processes 1Department of Geological Sciences, 871404, Arizona State Un  

E-print Network

, Conductivity, pH, and turbidity are measured in the field with hand-held meters · Alkalinity is titrated using" to monitor basic water quality parameters (Temperature, pH, Conductivity, dissolved Oxygen May Jun Jul Aug Sep Oct Nov Dec Turbidity(NTU) 0 100 200 300 400 500 0 100 200 300 400 500 turbidity

Hall, Sharon J.



EPA Science Inventory

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


Defining Dissolving  

NSDL National Science Digital Library

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

James Kessler



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.



How to Measure Dissolved Oxygen  

NSDL National Science Digital Library

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


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.



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

Microsoft Academic Search

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

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



Early life stage brook trout (Salvelinus fontinalis) experiment to determine the effects of pH, calcium and aluminum in low conductivity water  

SciTech Connect

Recruitment failure has been suggested as a mechanism leading to loss of fish populations in acidified streams and lakes. Numerous laboratory studies have investigated the effects of pH, aluminum, and calcium, alone or in combination, on early life stages of fish; however, the exposures in these experiments have been of relatively short duration. The objective of the present study was to determine the chronic effects of elevated aluminum concentrations as a function of pH and calcium level on hatching success and subsequent fry survival of brook trout. Brook trout eyed eggs (25 per chamber) were exposed to a replicated matrix of four levels each of pH and calcium and five levels of aluminum totaling 64 different combinations in a 40-day test. The levels of pH, aluminum, and calcium were chosen to represent the chemistry of sensitive lakes and streams in eastern Canada, the northeastern United States, and Scandinavia. We exposed fish to higher aluminum concentrations at lower pH levels, based on the observation that in acidified natural waters, dissolved inorganic aluminum increases as pH decreases (e.g., Shofield 1982). The results presented are based on nominal pH, aluminum, and calcium levels. 9 refs., 12 figs., 4 tabs.

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



Carbon Dioxide Addition to Microbial Fuel Cell Cathodes Maintains Sustainable Catholyte pH and Improves Anolyte pH, Alkalinity, and Conductivity  

Technology Transfer Automated Retrieval System (TEKTRAN)

Bioelectrochemical system (BES) pH imbalances develop due to anodic proton-generating oxidation reactions and cathodic hydroxide-ion-generating reduction reactions. Until now, workers added unsustainable buffers to reduce the pH difference between the anode and cathode because the pH imbalance cont...


In-line application of electric field in capillary separation systems: Joule heating, pH and conductivity.  


This study concerns the technique electric field-assisted capillary liquid chromatography. In this technique, an electric field is applied over the separation capillary in order to provide an additional selectivity. In this technique, the electric field is applied in-line in the separation capillary and here the electric current is the factor limiting the magnitude of applied electric field. The influence of Joule heating and other factors on the current in such systems has been investigated. The temperature in the capillary was first measured within a standard CE set-up, as function of effect per unit of length. Then the same cooling system was applied to an in-line set-up, to replicate the conditions between the two systems, and thus the temperature. Thus Joule heating effects could then be calculated within the in-line system. It was found that for systems applying an electric field in line, the direct influence from Joule heating was only relatively small. The pH in the capillary was measured in the in-line set-up using cresol red/TRIS solutions as pH probe. Significant changes in pH were observed and the results suggested that electrolysis of water is the dominant electrode reaction in the in-line system. In summary, the observed conductivity change in in-line systems was found to be mainly due to the pH change by hydrolysis of water, but primarily not due the temperature change in the capillary column. PMID:18371851

Eriksson, Bjrn O; Skuland, Inger Lill; Marlin, Nicola D; Andersson, Magnus B O; Blomberg, Lars G



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

SciTech Connect

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

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



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



Landscape Influences on Dissolved Organic Carbon, pH, Fe, and Ca in 37 Lakes in the Forest-Tundra of Northern Manitoba, Canada  

Microsoft Academic Search

DOC, pH, Fe, and Ca are major influences on lake ecosystems, and all three may be impacted by the surrounding catchment, especially the presence of wetlands and coniferous forest. To better understand past and future lake responses to climate change in the sub-arctic forest-tundra of northern Manitoba, we measured DOC, SUVA, pH, Ca, and Fe in 37 lakes in 2008

C. E. Umbanhowar; P. Camill; M. Edlund; K. Passow; P. Henneghan




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,


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



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.



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

PubMed Central

We determined the effects of intracellular respiratory and metabolic acid or alkali loads, at constant or variable external pH, on the apical membrane Na+-specific conductance (ga) and basolateral membrane conductance (gb), principally due to K+, in the short-circuited isolated frog skin epithelium. Conductances were determined from the current-voltage relations of the amiloride-inhibitable cellular current pathway, and intracellular pH (pHi) was measured using double barreled H+-sensitive microelectrodes. The experimental set up permitted simultaneous recording of conductances and pHi from the same epithelial cell. We found that due to the asymmetric permeability properties of apical and basolateral cell membranes to HCO3- and NH+4, the direction of the variations in pHi was dependent on the side of addition of the acid or alkali load. Specifically, changing from control Ringer, gassed in air without HCO3- (pHo = 7.4), to one containing 25 mmol/liter HCO3- that was gassed in 5% CO2 (pHo = 7.4) on the apical side caused a rapid intracellular acidification whereas when this maneuver was performed from the basolateral side of the epithelium a slight intracellular alkalinization was produced. The addition of 15 mmol/liter NH4Cl to control Ringer on the apical side caused an immediate intracellular alkalinization that lasted up to 30 min; subsequent removal of NH4Cl resulted in a reversible fall in pHi, whereas basolateral addition of NH4Cl produced a prolonged intracellular acidosis. Using these maneouvres to change pHi we found that the transepithelial Na+ transport rate (Isc), and ga, and gb were increased by an intracellular alkalinization and decreased by an acid shift in pHi. These variations in Isc, ga, and gb with changing pHi occurred simultaneously, instantaneously, and in parallel even upon small perturbations of pHi (range, 7.1-7.4). Taken together these results indicate that pHi may act as an intrinsic regulator of epithelial ion transport. PMID:3265144




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...


Soil pH effects on the comparative toxicity of dissolved zinc, non-nano and nano ZnO to the earthworm Eisenia fetida.  


To determine how soil properties influence nanoparticle (NP) fate, bioavailability and toxicity, this study compared the toxicity of nano zinc oxide (ZnO NPs), non-nano ZnO and ionic ZnCl2 to the earthworm Eisenia fetida in a natural soil at three pH levels. NP characterisation indicated that reaction with the soil media greatly controls ZnO properties. Three main conclusions were drawn. First that Zn toxicity, especially for reproduction, was influenced by pH for all Zn forms. This can be linked to the influence of pH on Zn dissolution. Secondly, that ZnO fate, toxicity and bioaccumulation were similar (including relationships with pH) for both ZnO forms, indicating the absence of NP-specific effects. Finally, earthworm Zn concentrations were higher in worms exposed to ZnO compared to ZnCl2, despite the greater toxicity of the ionic form. This observation suggests the importance of considering the relationship between uptake and toxicity in nanotoxicology studies. PMID:23739012

Heggelund, Laura R; Diez-Ortiz, Maria; Lofts, Stephen; Lahive, Elma; Jurkschat, Kerstin; Wojnarowicz, Jacek; Cedergreen, Nina; Spurgeon, David; Svendsen, Claus



Statistical summary of daily values data and trend analysis of dissolved-solids data at National Stream Quality Accounting Network (NASQAN) stations  

USGS Publications Warehouse

A statistical summary is provided of the available continuous and once-daily discharge, specific-conductance, dissolved oxygen , water temperature, and pH data collected at NASQAN stations during the 1973-81 water years and documents the period of record on which the statistical calculations were based. In addition, dissolved-solids data are examined by regression analyses to determine the relation between dissolved solids and specific conductance and to determine if long-term trends can be detected in dissolved-solids concentrations. Statistical summaries, regression equations expressing the relation between dissolved solids and specific conductance, and graphical presentations of trend analyses of dissolved solids are presented for 515 NASQAN stations in the United States, Canada, Guam, and Puerto Rico. (USGS)

Wells, F.C.; Schertz, T.L.



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.



Monitoring the changes of redox potential, pH and electrical conductivity of the mangrove soils in northern Taiwan.  


The redox potential (Eh), pH and electrical conductivity (EC) of the marsh soils of the Chuwei mangrove, located in the estuarine of the Tansui River in northern Taiwan were monitored for two years (from October 1995 to September 1997). The soils of selected pedons were studied, and the soils were classified based on Keys to Soil Taxonomy. The soil pH values tended to be neutral due to the impact of seawater on the mangrove marsh. The amounts of organic carbon found in this study area were much less than those generally encountered in the wetland soils of temperate regions in the world. The base saturation percentages of the soils were almost 100%, the exchangeable Na being particularly predominant. The concentrations of various cations of water in this ecosystem were in the order of Na+ > Mg2+ > K+ = Ca2+, and those of anions of water were in the order of Cl- > SO4(2-) > NO3- > PO4(3-). In spite of seasonal flooding changes, highly reduced states (100 to -200 mV of Eh values) existed throughout the two-year study. The spatial and temporal variations of the Eh values of the surface soil (0-20 cm) were higher than those of the subsoils (20-100 cm). The EC values of the soils from the surface to a depth of 100-cm were generally more than 20 dS/m. The marsh soils of the Chuwei mangrove were, thus, classified as Halic Endoaquents or Halic Fluvaquents. PMID:10943948

Hseu, Z Y; Chen, Z S



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

NASA Astrophysics Data System (ADS)

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 Mouintains showed that rainfall acidity varied over the course of summer storms, with low initial pH values increasing as storm intensity increased.

Johnsson, Patricia A.; Reddy, Michael M.


Influence of pH, inorganic anions, and dissolved organic matter on the photolysis of antimicrobial triclocarban in aqueous systems under simulated sunlight irradiation.  


The photolysis of the antimicrobial triclocarban (TCC) in aqueous systems under simulated sunlight irradiation was studied. The effects of several abiotic parameters, including solution pH, initial TCC concentration, presence of natural organic matter, and most common inorganic anions in surface waters, were investigated. The results show that the photolysis of TCC followed pseudo-first-order kinetics. The TCC photolysis rate constant increased with increasing solution pH and decreasing the initial TCC concentration. Compared with the TCC photolysis in pure water, the presence of aqueous bicarbonate, nitrate, humic acids, and its sodium salt decreased the TCC photolysis rate, but fulvic acid increased the TCC photolysis rate. The electron spin resonance and reactive oxygen species scavenging experiments indicated that TCC may undergo two different types of phototransformation reactions: direct photolysis and energy transfer to generate (1)O2. The main degradation products were tentatively identified by gas chromatography interfaced with mass spectrometry (GC-MS), and a possible degradation pathway was also proposed. PMID:25354431

Ding, Shi-Ling; Wang, Xi-Kui; Jiang, Wen-Qiang; Zhao, Ru-Song; Shen, Ting-Ting; Wang, Chen; Wang, Xia



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


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

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




EPA Science Inventory

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


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



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

SciTech Connect

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

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




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...


Feasible metabolisms in high pH springs of the Philippines.  


A field campaign targeting high pH, H2-, and CH4-emitting serpentinite-associated springs in the Zambales and Palawan Ophiolites of the Philippines was conducted in 2012-2013, and enabled description of several springs sourced in altered pillow basalts, gabbros, and peridotites. We combine field observations of pH, temperature, conductivity, dissolved oxygen, and oxidation-reduction potential with analyses of major ions, dissolved inorganic carbon, dissolved organic carbon, and dissolved gas phases in order to model the activities of selected phases important to microbial metabolism, and to rank feasible metabolic reactions based on energy yield. We document changing geochemical inventories in these springs between sampling years, and examine how the environment supports or prevents the function of certain microbial metabolisms. In all, this geochemistry-based assessment of feasible metabolisms indicates methane cycling, hydrogen oxidation, some iron and sulfur metabolisms, and ammonia oxidation are feasible reactions in this continental site of serpentinization. PMID:25713561

Cardace, Dawn; Meyer-Dombard, D'Arcy R; Woycheese, Kristin M; Arcilla, Carlo A



Feasible metabolisms in high pH springs of the Philippines  

PubMed Central

A field campaign targeting high pH, H2-, and CH4-emitting serpentinite-associated springs in the Zambales and Palawan Ophiolites of the Philippines was conducted in 2012-2013, and enabled description of several springs sourced in altered pillow basalts, gabbros, and peridotites. We combine field observations of pH, temperature, conductivity, dissolved oxygen, and oxidation-reduction potential with analyses of major ions, dissolved inorganic carbon, dissolved organic carbon, and dissolved gas phases in order to model the activities of selected phases important to microbial metabolism, and to rank feasible metabolic reactions based on energy yield. We document changing geochemical inventories in these springs between sampling years, and examine how the environment supports or prevents the function of certain microbial metabolisms. In all, this geochemistry-based assessment of feasible metabolisms indicates methane cycling, hydrogen oxidation, some iron and sulfur metabolisms, and ammonia oxidation are feasible reactions in this continental site of serpentinization. PMID:25713561

Cardace, Dawn; Meyer-Dombard, D'Arcy R.; Woycheese, Kristin M.; Arcilla, Carlo A.



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)



Phase equilibria in subseafloor hydrothermal systems: A review of the role of redox, temperature, pH and dissolved Cl on the chemistry of hot spring fluids at mid-ocean ridges  

NASA Astrophysics Data System (ADS)

Time series measurements of the chemistry of hot spring fluids at mid-ocean ridges (MOR) have revealed steady state concentrations of dissolved species that indicate solubility control by mineral phases in subseafloor reaction zones [Campbell et al., 1988a; Bowers et al., 1988; Butterfield et al. 1994]. That MOR hot spring fluids have relatively low measured pH values (3.1 to 3.9), and are variably depleted in Mg and SO4, while enriched in Ca, K, and Si [Von Damm, 1990] relative to seawater, is entirely consistent with heterogeneous equilibria involving feldspar, chlorite, epidote quartz and NaCl fluids at temperatures in the vicinity of 375-400C [Seyfried et al., 1991]. The high concentrations of so-called "soluble" elements, such as Li, Rb, Cs, and B [Von Damm et al., 1985; Spivack and Edmond, 1987], however, require an abundance of fresh rock (basalt/diabase) relative to the mass of seawater (i.e., low fluid/rock ratio). That these elements also fall to reveal significant compositional changes in fluids from specific hot springs sampled several times over a six year period [Campbell et al., 1985a; Butterfield et al. 1994; Butterfield and Massoth 1994] indicates a non-static and expanding reaction zone caused by penetration of seawater into previously unaltered portions of a solidified magma chamber. Although most vent fluids reveal short term stability [Campbell et al. 1988a; Butterfield and Massoth 1994], this is not always the case, as evidenced by the temporal evolution of the composition of vent fluids at the North Cleft segment of the Juan de Fuca Ridge [Butterfield et al. 1991; Butterfield and Massoth, 1994], and at 9-10degN EPR [Von Damm et al. 1991].

Seyfried, W. E., Jr.; Ding, Kang


Dissolved Oxygen Protocol  

NSDL National Science Digital Library

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

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



Isotope fractionation during oxidation of tetravalent uranium by dissolved oxygen  

NASA Astrophysics Data System (ADS)

We conducted laboratory experiments to investigate isotopic fractionations during oxidation of tetravalent uranium, U(IV), by dissolved oxygen. In hydrochloric acid media with the U(IV) dissolved, the ?238U value of the remaining U(IV) increased as the extent of oxidation increased. The ?238U value of the product U(VI) paralleled, but was offset to 1.1 0.2 lower than the remaining U(IV). In contrast, oxidation of solid U(IV) by dissolved oxygen in 20 mM NaHCO3 solution at pH = 9.4 caused only a weak fractionation (?0.1 to 0.3), with ?238U being higher in the dissolved U(VI) relative to the solid U(IV). We suggest that isotope fractionation during oxidation of solid U(IV) is inhibited by a "rind effect", where the surface layer of the solid U(IV) must be completely oxidized before the next layer is exposed to oxidant. The necessity of complete conversion of each layer results in minimal isotopic effect. The weak shift in ?238U of U(VI) is attributed to adsorption of part of the product U(VI) to the solid U(IV) surfaces.

Wang, Xiangli; Johnson, Thomas M.; Lundstrom, Craig C.



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.

James Kessler




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...


Generalized regression neural network (GRNN)-based approach for colored dissolved organic matter (CDOM) retrieval: case study of Connecticut River at Middle Haddam Station, USA.  


The prediction of colored dissolved organic matter (CDOM) using artificial neural network approaches has received little attention in the past few decades. In this study, colored dissolved organic matter (CDOM) was modeled using generalized regression neural network (GRNN) and multiple linear regression (MLR) models as a function of Water temperature (TE), pH, specific conductance (SC), and turbidity (TU). Evaluation of the prediction accuracy of the models is based on the root mean square error (RMSE), mean absolute error (MAE), coefficient of correlation (CC), and Willmott's index of agreement (d). The results indicated that GRNN can be applied successfully for prediction of colored dissolved organic matter (CDOM). PMID:25112840

Heddam, Salim



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.



Correlation Between x18 and pH in Lakes  

Microsoft Academic Search

THERE is a definite relation between specific conductivity (x18 = n 10-6) and active reaction (expressed as pH, and indicating the concentration of hydroxonium (H3O+) ions) in lake waters. Within a single lake these values vary inversely, which really means that the concentrations of electrolytes and H3O+-ions move together. Biological processes deplete surface waters of carbon dioxide and dissolved

Kaare Mnster Strm



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.



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.



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  

SciTech Connect

Five intersite comparison studies for the field determination of pH and specific conductance, using simulated-precipitation samples, were conducted by the USGS 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 USGS 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. 19 refs., 6 figs., 18 tabs.

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



Dissolving Salts in Water  

NSDL National Science Digital Library

In this interactive activity adapted from Iowa State University, design and carry out an experiment: dissolve salts in water, see how different ionic compounds produce different reactions, and observe the resulting changes in temperature.



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,


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



Temperature Affects Dissolving  

NSDL National Science Digital Library

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

James Kessler



Dissolved Oxygen Activity  

NSDL National Science Digital Library

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

Steve Gordon


Dissolved Oxygen Model  

NSDL National Science Digital Library

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

Steve Gordon


Dissolved Organic Matter  

Microsoft Academic Search

Dissolved organic matter (DOM) is defined as the organic matter fraction in solution that passes through a 0.45 ?m filter. Although DOM is ubiquitous in terrestrial and aquatic ecosystems, it represents only a small proportion of the total organic matter in soil. However, DOM, being the most mobile and actively cycling organic matter fraction, influences a spectrum of biogeochemical processes

Nanthi S. Bolan; Domy C. Adriano; Anitha Kunhikrishnan; Trevor James; Richard McDowell; Nicola Senesi



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.



Dissolved-Oxygen Requirements of Three Species of Fish  

Microsoft Academic Search

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

D. D. Moss; D. C. Scott



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.



Field measurement of dissolved BTEX biodegradation  

SciTech Connect

Field measurements and analyses can provide real-time data about the potential for biodegradation of benzene, toluene, ethylbenzene, and total xylenes (BTEX) dissolved in ground water. Measurement of dissolved oxygen concentrations, pH, temperature, and redox potential in site ground water can be used to quickly assess the potential for biodegradation of BTEX contamination. Other chemical-specific analyses that can be rapidly performed on site provide valuable data on how BTEX may be biodegrading at the site by identifying chemical species that may be used to facilitate, or are produced, during the biodegradation of BTEX Field analyses for ferrous iron, total iron, nitrate, nitrite, sulfate, sulfide, carbon dioxide and alkalinity completed at Bolling, Carswell and Plattsburgh Air Force Bases can be used to determine the terminal electron acceptor used to facilitate BTEX biodegradation.

Hoffer, S. [Colorado School of Mines, Golden, CO (United States); Benson, L.A.; Schmiermund, R.L. [Parsons Engineering Science, Inc., Denver, CO (United States)] [and others



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


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

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



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.

James Kessler



Tried and True: Inquiry-based dissolving  

NSDL National Science Digital Library

This project highlights a dissolving unit that was part of an eighth-grade, semester-long investigation into matter. During the dissolving unit, students explored the concepts of mixture, solution, dissolving, saturation, and conservation of mass. Dissolv

Gregory Benedis-Grab




EPA Science Inventory

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


Dissolved heavy metal determination and ecotoxicological assessment: a case study of the corumbata river (so paulo, Brazil).  


The aim of this one-year study (August 2009 to July 2010) was to evaluate the Corumbata River water polluted by anthropogenic sources and see how it affects the reproduction of the microcrustacean Ceriodaphnia dubia (Richard, 1984) in laboratory conditions over seven days of exposure to water samples collected monthly at six different locations. We determined the concentrations of zinc (Zn), copper (Cu), nickel (Ni), lead (Pb), and cadmium (Cd), as well as physicochemical parameters such as dissolved oxygen, conductivity, water temperature, and pH. Dissolved oxygen and conductivity demonstrated anthropogenic influence, as dissolved oxygen concentration decreased and conductivity increased from the upstream to the downstream stretch of the river. The effects on C. dubia were observed in the months with high precipitation, but the toxicity cannot be associated with any particular contaminant. Heavy metal levels kept well below the limit values. Zn and Pb had the highest concentrations in the water during the sampling period, probably due to the industrial and agricultural influence. However, these levels do not seem to be associated with precipitation, which suggests that their primary source was industry. Physicochemical parameters, the ecotoxicological assay, and determination of heavy metals proved to be efficient tools to evaluate aquatic environments. PMID:25274936

Aparecida Maranho, Lucineide; Teresinha Maranho, Leila; Grossi Botelho, Rafael; Luiz Tornisielo, Valdemar




Microsoft Academic Search

Limnologic and water chemistry data from Echo Bay Mineral's Key West and Equinox Resources' Van Stone mines were collected between August, 2000 and September, 2001. Pit lake elevations, areas and depths are 1,318 and 1,050 m; 1.1 and 1.9 ha; and 28 and 31 m, respectively. Depth profiles of temperature, pH, specific conductivity, oxidation-reduction potential (ORP), and dissolved oxygen were

Rodney T. Lentz



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.



Yucca Mountain Area Saturated Zone Dissolved Organic Carbon Isotopic Data  

SciTech Connect

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

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



Pyrite oxidation at circumneutral pH  

Microsoft Academic Search

Previous studies of pyrite oxidation kinetics have concentrated primarily on the reaction at low pH, where Fe(III) has been assumed to be the dominant oxidant. Studies at circumneutral pH, necessitated by effective pH buffering in some pyrite oxidation systems, have often implicitly assumed that the dominant oxidant must be dissolved oxygen (DO), owing to the diminished solubility of Fe(III). In

C. O Moses; J. S Herman



Method of synthesis of proton conducting materials  


A method of producing a proton conducting material, comprising adding a pyrophosphate salt to a solvent to produce a dissolved pyrophosphate salt; adding an inorganic acid salt to a solvent to produce a dissolved inorganic acid salt; adding the dissolved inorganic acid salt to the dissolved pyrophosphate salt to produce a mixture; substantially evaporating the solvent from the mixture to produce a precipitate; and calcining the precipitate at a temperature of from about C. to about C.

Garzon, Fernando Henry; Einsla, Melinda Lou; Mukundan, Rangachary



Linking fluorescence spectroscopy to diffuse soil source for dissolved humic substances in the Daning River, China.  


Dissolved organic matter collected in Daning River (China) in July 2009 was investigated with parallel factor analysis (PARAFAC) and fluorescence spectroscopy with the aim of identifying the origin of dissolved humic substance (HS) components. Two HS-like fluorescence components (peak M and C) with excitation/emission (ex/em) maxima at 305/406 nm and 360/464 nm showed relatively uniform distribution in the vertical direction for each sampling site but a trend of accumulation down the river, independent of the highly heterogeneous water environment as implicated by water quality parameters (i.e., water temperature, algae density, chlorophyll a, dissolved oxygen, dissolved organic carbon, pH, conductivity and turbidity), while an amino acid/protein-like component (peak T; ex/em = 280/334 nm) was quite variable in its spatial distribution, implying strong influence from point sources (e.g. sewage discharge) and local microbial activities. The fluorescence intensity (F max in Raman units) at these ex/em wavelength pairs fell in the range of 0.031-0.358, 0.051-0.224 and 0.026-0.115 for peak T, M and C, respectively. In addition, the F max values of peak C covaried with M (i.e. C = 0.503 M, p < 0.01, R (2) = 0.973). Taken together, these results indicate that peak M and C originated primarily and directly from the same soil sources that were diffusive in the catchment, but peak T was more influenced by local point sources (e.g. wastewater discharge) and in situ microbial activities. This study presents new insights into the currently controversial origin of some HS components (e.g."peak M", as commonly referred to in the literature). This study highlights that natural water samples should be collected at various depths in addition to along a river/stream flow path so as to better evaluate the origin of HS fluorescence components. PMID:25208714

Chen, Hao; Zheng, Bing-Hui; Zhang, Lei



Experimental determination of equilibrium Fe isotopic fractionation between pyrite and dissolved Fe under hydrothermal conditions  

NASA Astrophysics Data System (ADS)

Fe isotope fractionation between pyrite (FeS2) and dissolved Fe in NaCl- and sulfur-bearing aqueous fluids was determined under hydrothermal conditions (300-350 C, 500 bars). The data were collected using two different, but complementary, experimental approaches, one involving classical Fe isotope exchange between Fe in pyrite and dissolved Fe in coexisting fluid, while the other involved homogenous precipitation of pyrite in a redox and pH buffered chemical system. Results from these experiments indicate equilibrium Fe isotopic fractionation between pyrite and fluid, ?56FePyr-Fe(aq), of 0.99 0.29 (2?), in 56Fe/54Fe. The experimentally determined equilibrium pyrite-fluid Fe isotopic fractionation agrees with theoretical and spectrally-based predictions. The second series of experiments were conducted to better constrain the effect of precipitation rate on the temporal evolution of the Fe isotopic composition of pyrite and Fe bearing fluids in dynamic mixing environments, such as hydrothermal vent sites at mid-ocean ridges. Rapid homogenous precipitation of pyrite at 300 and 350 C indicates that ?56Fe of dissolved Fe is significantly greater than pyrite that formed during the earliest stage of the experiment, possibly facilitated by either equilibrium or kinetic isotope effects involving FeS as a reactant during pyrite formation. Subsequent recrystallization of pyrite results in a Fe isotopic fractionation with dissolved Fe that moves towards the experimentally determined equilibrium Fe isotopic fractionation with reaction progress. The experimental data reported here may help to decipher the complex kinetic and thermodynamic processes involved in pyrite formation at deep sea vents, while also providing constraints for the rapidly developing theoretical models used to estimate equilibrium Fe isotope fractionation between pyrite and fluid at elevated temperatures and pressures.

Syverson, Drew D.; Borrok, David M.; Seyfried, William E.



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

SciTech Connect

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




Lisa B. Beever, PhD, AICP September 28, 2009  

E-print Network

Lisa B. Beever, PhD, AICP September 28, 2009 Estero Bay Watershed Public SymposiumEstero Bay- September 2004 #12;Chlorophyll a #12;Ammonia #12;Nitrate/Nitrite #12;Dissolved Oxygen #12;Turbidity #12 B. Beever, PhD, AICPDirector: Lisa B. Beever, PhD, AICP Deputy Director: Liz Donley,Deputy Director

Demers, Nora Egan


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

Microsoft Academic Search

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

Hyeog-Chan Kwon



Dissolving Different Liquids in Water  

NSDL National Science Digital Library

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

James Kessler



Miniaturization of cytotoxicity tests for concentration range-finding studies prior to conducting the pH 6.7 Syrian hamster embryo cell-transformation assay.  


The Syrian hamster embryo (SHE) cell-transformation assay (SHE assay) is a promising alternative method to animal testing for the identification of potential carcinogens in vitro. Prior to conducting the SHE assay the appropriate concentration range for each test chemical must be established, with a maximum concentration causing approximately 50% cytotoxicity. Concentration range-finding is done in separate experiments, which are similar to the final SHE assay but with less replicates and more concentrations. Here we present an alternative for the cytotoxicity testing by miniaturization of the test procedure by use of 24-well plates and surpluses from feeder-cell preparations as target cells. In addition, we integrated the photometry-based neutral red (NR) assay. For validation of the assay, incubations with dimethyl sulf-oxide, p-phenylenediamine-2HCl, aniline, o-toluidine-HCl, 2,4-diaminotoluene, and 2-naphthylamine were carried out in the miniaturized approach and compared with the standard procedure in terms of calculating the relative plating efficiencies (RPEs). To directly compare both methods, concentrations that produced 50% cytotoxicity (IC50) were calculated. Excellent associations were observed between the number of colonies and NR uptake. For all test substances a concentration-dependent, concomitant decrease of NR uptake in the miniaturized approach and RPEs in the standard test was observed after a 7-day incubation. The results from both test setups showed a comparable order of magnitude and the IC50 values differed by a factor <2 (1.4-1.9), depending on the substance in question. Overall, the miniaturized approach should be considered an improved alternative for cytotoxicity testing in the SHE assay, as it saves valuable SHE cells and speeds-up the time, to obtain test results more rapidly. PMID:23830925

Plttner, Sabine; Kfferlein, Heiko U; Brning, Thomas



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.



Impact of Stream Channel Urbanization on Dissolved Oxygen Concentrations  

NASA Astrophysics Data System (ADS)

Dissolved oxygen concentration in freshwater streams is an important regulator of ecosystem processes and indicator of stream health. This study attempts to investigate the impacts of urbanization and temperature on dissolved oxygen fluctuations in streams. Field measurements, laboratory experiments, and analysis of diurnal cycles of dissolved oxygen are evaluated in eight streams of the Baltimore and Anacostia watersheds along an urban to rural gradient. Temperature and dissolved oxygen measurements were taken from 8 long-term monitoring sites (5 Baltimore Long Term Ecological Research sites and 3 Anacostia branch sites monitored by the U.S. Geological Survey) in order to characterize fluctuations in dissolved oxygen influenced by changes in land use and temperature. Laboratory experiments investigating changes in 5-day biochemical oxygen demand across 3 different temperatures (4, 15, and 20 degrees Celsius) across land use were conducted using a temperature controlled incubator. Biochemical oxygen demand typically increased with increasing temperature and varied with land use. There were strong relationships between routine dissolved oxygen and temperature seasonally in streams of the Baltimore Long-Term Ecological Research site and Anacostia watershed. Land use and temperature may influence biochemical oxygen demand in streams and impact seasonal dynamics of dissolved oxygen.

Van Orden, E. T.



Controls on Flux Rates of Dissolved Gaseous Mercury Emitted from an Estuarine Water Column to the Atmosphere in Eastern New Jersey  

Microsoft Academic Search

The emission rate of mercury from a water surface is influenced by a matrix of water quality parameters, including dissolved organic material (DOM), incident radiation, pH, salinity, and dissolved oxygen. As part of a larger project examining the total flux of dissolved gaseous mercury (DGM) from water, land, and plant surfaces, this work attempts to characterize the variables that control

S. Peters; J. Wollenberg




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.




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


Online dissolved methane and total dissolved sulfide measurement in sewers.  


Recent studies using short-term manual sampling of sewage followed by off-line laboratory gas chromatography (GC) measurement have shown that a substantial amount of dissolved methane is produced in sewer systems. However, only limited data has been acquired to date due to the low frequency and short span of this method, which cannot capture the dynamic variations of in-sewer dissolved methane concentrations. In this study, a newly developed online measuring device was used to monitor dissolved methane concentrations at the end of a rising main sewer network, over two periods of three weeks each, in summer and early winter, respectively. This device uses an online gas-phase methane sensor to measure methane under equilibrium conditions after being stripped from the sewage. The data are then converted to liquid-phase methane concentrations according to Henry's Law. The detection limit and range are suitable for sewer application and can be adjusted by varying the ratio of liquid-to-gas phase volume settings. The measurement presented good linearity (R > 0.95) during field application, when compared to off-line measurements. The overall data set showed a wide variation in dissolved methane concentration of 5-15 mg/L in summer and 3.5-12 mg/L in winter, resulting in a significant average daily production of 24.6 and 19.0 kg-CH?/d, respectively, from the network with a daily average sewage flow of 2840 m/day. The dissolved methane concentration demonstrated a clear diurnal pattern coinciding with flow and sulfide fluctuation, implying a relationship with the wastewater hydraulic retention time (HRT). The total dissolved sulfide (TDS) concentration in sewers can be determined simultaneously with the same principle. PMID:25462721

Liu, Yiwen; Sharma, Keshab R; Fluggen, Markus; O'Halloran, Kelly; Murthy, Sudhir; Yuan, Zhiguo



Transport of Proteins Dissolved in Organic Solvents Across Biomimetic Membranes  

NASA Astrophysics Data System (ADS)

Using lipid-impregnated porous cellulose membranes as biomimetic barriers, we tested the hypothesis that to afford effective transmembrane transfer of proteins and nucleic acids, the vehicle solvent should be able to dissolve both the biopolymers and the lipids. While the majority of solvents dissolve one or the other, ethanol and methanol were found to dissolve both, especially if the protein had been lyophilized from an aqueous solution of a pH remote from the protein's isoelectric point. A number of proteins, as well as RNA and DNA, dissolved in these alcohols readily crossed the lipidized membranes, whereas the same biopolymers placed in nondissolving solvents (e.g., hexane and ethyl acetate) or in those unable to dissolve lipids (e.g., water and dimethyl sulfoxide) exhibited little transmembrane transport. The solubility of biopolymers in ethanol and methanol was further enhanced by complexation with detergents and poly(ethylene glycol); significant protein and nucleic acid transport through the lipidized membranes was observed from these solvents but not from water.

Bromberg, Lev E.; Klibanov, Alexander M.



Dynamics of Planktonic Prokaryotes and Dissolved Carbon in a Subtropical Coastal Lake  

PubMed Central

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?=?27C) and lower in the winter (average?=?235??M WT?=?17C), 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??109?cells?L?1 and 20.83??mol?C?L?1) and lower in the summer (1.87??109?cells?L?1 and 3.95??mol?C?L?1). Filamentous cyanobacteria (0.23??1080.68??108?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; Antnio, Regina V.; Petrucio, Maurcio M.



Reducing emissions from uranium dissolving  

SciTech Connect

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

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



Reducing emissions from uranium dissolving  

SciTech Connect

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

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



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; )



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.

James Kessler



Influence of naturally occurring dissolved organic matter, colloids, and cations on nanofiltration of pharmaceutically active and endocrine disrupting compounds.  


This study examined the rejection of selected pharmaceutically active (PhAC) and endocrine disrupting compounds (EDCs) when using nanofiltration as a function of naturally occurring dissolved organic matter (DOM), colloidal particles, cations and their interactions. Lake Ontario water served as a source of natural DOM and colloidal particles. PhAC/EDC rejection experiments were conducted using raw Lake Ontario water and Lake Ontario water that was pre-treated with either ultrafiltration to remove colloidal particles, or fluidized ion exchange resins to remove DOM. Additionally, the concentration of cations (Ca(2+), Mg(2+), and Na(+)) in the raw and pre-treated water matrices was varied. While ionic PhACs and EDCs exhibited high rejections from all the water matrices examined, neutral compounds were most effectively rejected in water containing DOM and no colloids, and least effectively rejected from colloid-containing water with increased cations but no DOM. The presence of DOM significantly improved compound rejection and the increase in cation concentration significantly decreased rejection. The presence of colloids had comparatively little effect except to mitigate the impact of increased cation concentration, apparently providing some cation-buffering capacity. The sequence in which constituents are removed from waters during treatment may significantly impact PhAC and EDC removal, especially of neutral compounds. PMID:25016429

Sadmani, A H M Anwar; Andrews, Robert C; Bagley, David M



Dissolving pulp from jute stick.  


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

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



Group of Microbes Change Dissolved  

E-print Network

that thrive in environments where dissolved gold is found, such as hydrothermal vents and hot springs, could, the researchers placed iron- reducing microbes in a gold solution similar to that found in a hydrothermal vent on the bottom of the ocean, near hydrothermal vents, millions of years ago. Since the research was published

Lovley, Derek



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...


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



SciTech Connect

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

P. Bernot



Phosphorus and nitrogen sorption to soils in the presence of poultry litter-derived dissolved organic matter.  


Two environmental aspects associated with land application of poultry litter that have not been comprehensively evaluated are (i) the competition of dissolved organic matter (DOM) and P for soil sorption sites, and (ii) the sorption of dissolved organic nitrogen (DON) relative to inorganic nitrogen species (e.g., NO(3)(-) and NH(4)(+)) and dissolved organic carbon (DOC). The competition between DOM and P for sorption sites has often been assumed to increase the amount of P available for plant growth; however, elevating DOM concentrations may also increase P available for transport to water resources. Batch sorption experiments were conducted to (i) evaluate soil properties governing P sorption to benchmark soils of Southwestern Missouri, (ii) elucidate the impact of poultry litter-derived DOM on P sorption, and (iii) investigate DON retention relative to inorganic N species and DOC. Soils were reacted for 24 h with inorganic P (0-60 mg L(-1)) in the presence and absence of DOM (145 mg C L(-1)) using a background electrolyte solution comparable to DOM extracts (I = 10.8 mmol L(-1); pH 7.7). Soil P sorption was positively correlated with metal oxide (r(2) = 0.70) and clay content (r(2) = 0.79) and negatively correlated with Bray-1 extractable P (r(2) = 0.79). Poultry litter-derived DOM had no significant negative impact on P sorption. Dissolved organic nitrogen was preferentially removed from solution relative to (NO(3)(-)-N + NO(2)(-)-N), NH(4)(+)-N, and DOC. This research indicates that poultry litter-derived DOM is not likely to enhance inorganic P transport which contradicts the assumption that DOM released from organic wastes increases plant-available P when organic amendments and fertilizer P are co-applied. Additionally, this work demonstrates the need to further evaluate the fate and transport of DON in agroecosystem soils receiving poultry litter applications. PMID:18178888

Goyne, Keith W; Jun, Hee-Joong; Anderson, Stephen H; Motavalli, Peter P



Nutrient Management Module No. 8 Soil pH and  

E-print Network

by both acid and base-forming ions in the soil. Common acid-forming cations (positively charged dissolved with the focus on soil pH and organic matter: soil reactions and soil amendments, and soil test reportsH is a measure of the soil solution's acidity and alkalinity. By definition, pH is the `negative logarithm

Lawrence, Rick L.


Dissolving mechanism of strain P17 on insoluble phosphorus of yellow-brown soil  

PubMed Central

Strain P17 was a bacterial strain identified as Bacillus megaterium isolated from ground accumulating phosphate rock powder. The fermentation broth of strain P17 and the yellow-brown soil from Nanjing Agricultural University garden were collected to conduct this study. The simulation of fixed insoluble phosphorous forms after applying calcium superphosphate into yellow-brown soil was performed in pots, while available P and total P of soil were extremely positive correlative with those of groundwater. Then the dissolving effect of strain P17 on insoluble P of yellow-brown soil was studied. Results showed that Bacillus megaterium strain P17 had notable solubilizing effect on insoluble phosphates formed when too much water-soluble phosphorous fertilizer used. During 100 days after inoculation, strain P17 was dominant. Until the 120th day, compared with water addition, available P of strain P17 inoculation treated soil increased by 3 times with calcium superphosphate addition. Besides available P, pH, activity of acid and alkaline phosphatase and population of P-solubilizing microbes were detected respectively. P-solubilizing mechanism of P-solubilizing bacteria strain P17 seems to be a synergetic effect of pH decrease, organic acids, phosphatase, etc. PMID:25477929

Chuan-qing, Zhong; Guang-xiang, Cao; Wei-yi, Huang; Xing-she, Luan; Yi-fei, Yang



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


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

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



Summary PhD candidate satisfaction survey 2011 Introduction  

E-print Network

1 Summary PhD candidate satisfaction survey 2011 Introduction Nine years ago, Utrecht University asked its PhD candidates to rate a number of aspects of their PhD careers: were they on schedule; what completing their PhDs. Nine years later, a second survey is conducted on PhD candidate satisfaction

Utrecht, Universiteit


Dissolved Oxygen and Biochemical Oxygen Demand  

NSDL National Science Digital Library

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


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.



Dissolved oxygen as a key parameter to aerobic granule formation.  


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 velocities ranging from 1.2 to 0.4 cm s(-1). When less than 1 cm s(-1) shear was applied to the reactor, aerobic granules disintegrated into flocs, with corresponding increases in SVI and effluent suspended solids. However, the dissolved oxygen also decreased from 8 mg L(-1) to 5 mg L(-1), affecting the Feast/Famine regime in the SBR and the substrate removal kinetics. A second experiment operated two SBRs with an identical shear force of 1.2 cm s(-1), but two dissolved oxygen concentrations. Even when supplied a high shear force, aerobic granules could not form at a dissolved oxygen less than 5 mg L(-1), with a Static Fill. These results indicate that the substrate removal kinetics and dissolved oxygen are more significant to granule formation than shear force. PMID:18776612

Sturm, B S McSwain; Irvine, R L



Hydrodynamics of coal-liquefaction dissolver configurations  

Microsoft Academic Search

The hydrodynamics of two proposed dissolver configurations for the 63.6 kg\\/s (6000 tpd) SRC-I demonstration plant were examined. Correlations were used to predict the flow patterns, holdups, pressure drops, bubble-size distribution, and axial mixing in the dissolvers and piping. Calculations on the performance of dissolver internals revealed slug flow and related pressure fluctuations may present serious control problems. The dissolver

C. F. Irwin; A. J. Sincali; E. W. Wong



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



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


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



Azomethine H colorimetric method for determining dissolved boron in water  

USGS Publications Warehouse

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

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



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


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



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.



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.



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.



Secret Agents of Dissolved Oxygen  

NSDL National Science Digital Library

This activity explores how water chemistry is altered by the biological processes of phytoplankton (microscopic photosynthetic organisms). Students will discover what some of these water chemistry changes are, and what influences these changes (type of water, exposure to light, etc.). The students will design an activity based on experience gained from the first activity. They will determine the changes and causes thereof in different types of water in a sealed container over time, and learn to measure dissolved oxygen, temperature, and carbon dioxide with a calculator/computer probe-ware or by other means.

Besse Dawson


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.



Size and Chemical Affinity Fractionated Dissolved Cadmium, Copper and Nickel in Gulf of Mexico Surface Waters  

NASA Astrophysics Data System (ADS)

Dissolved trace metals Cd, Cu, and Ni in the surface waters of Gulf of Mexico exhibit distinct chemical reactivity and physical size distributions when using cross-flow ultrafiltration and ion exchange methods during a field survey conducted in May 2006. Variations of total dissolved metal concentrations in surface waters were found across the salinity gradient, which ranged as follows; Cd: 87-187 pM; Cu: 1.4-18.3nM; and Ni: 2.6-18.8nM. Dissolved Cd was predominantly present as a truly dissolved (97%) and cationic-labile fraction (94%) in the surface waters. The anionic-organic metal fractions accounted for just 31 % on average for Cd, 24% for Cu, and 9% for Ni. The dissolved inert metal fractions, on average, were 31% of total dissolved Cu and 29% of total dissolved Ni concentrations. Small but noticeable amounts (6%) of dissolved inert Cd fractions were also present. Some fractions of the total dissolved Cu (17%) and Ni (8%) could be adsorbed by both cation and anion exchange resins, suggesting binding to zwitterionic molecules. Despite evidence that partitioning among chemically and physically defined species is dynamic, mixing between freshwater and seawater end-members across the Mississippi River plume produced linear mixing curves, while trace metal concentrations determined within warm core and cold core rings in the Gulf of Mexico maintained significantly different concentrations and species distributions.

Wen, L.; Warnken, K. W.; Santschi, P. H.



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 (8.158.22), 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. PMID:23071704

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



pH Dependence of the Physical and Electronic Structure of a Supramolecular Porphyrin Assembly  

E-print Network

pH Dependence of the Physical and Electronic Structure of a Supramolecular Porphyrin Assembly nitrogens can result in physical and electronic distortions. · In acidic solutions (pH by dissolving solid TCPP in dilute ammonium hydroxide, then titrating with HCl to a desired pH1. UV

Collins, Gary S.


Biodegradable Materials and Their Effect on Dissolved Oxygen Levels  

NSDL National Science Digital Library

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


Fate of Acids in Clouds 1. Combination with bases dissolved in clouds: acids neutralized  

E-print Network

problems. E#11;ects of Acid Rain 1. Vegetation: SO 2 is toxic to plants #15; Leaves damaged below pH 3 rain { Athens and Rome cathedrals and statues: pollution leads to acid rain #15; SteelFate of Acids in Clouds 1. Combination with bases dissolved in clouds: acids neutralized NH 3 (g

Schofield, Jeremy


Behaviour of Sb(V) in the presence of dissolved sulfide under controlled anoxic aqueous conditions  

E-print Network

: Antimony Dissolved sulfide Metastibnite HG-AFS Antimony (Sb) exists in natural waters in two oxidation. 2009 Elsevier B.V. All rights reserved. 1. Introduction Until recently, antimony (Sb) had largely been oxidation state of antimony in oxic waters likely present as Sb(OH)6 - at pH conditions of natural systems

Belzile, Nelson


Neural network modeling of dissolved oxygen in the Grua reservoir, Serbia  

Microsoft Academic Search

The objective of this study is to develop a feedforward neural network (FNN) model to predict the dissolved oxygen in the Grua Reservoir, Serbia. The neural network model was developed using experimental data which are collected during a three years. The input variables of the neural network are: water pH, water temperature, chloride, total phosphate, nitrites, nitrates, ammonia, iron, manganese

Vesna Rankovi?; Jasna Radulovi?; Ivana Radojevi?; Aleksandar Ostoji?; Ljiljana ?omi?



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


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); Chiarizia, Renato (Argonne, IL)



Factors influencing concentrations of dissolved gaseous mercury (DGM) and total mercury (TM) in an artificial reservoir  

Microsoft Academic Search

The effects of various factors including turbidity, pH, DOC, temperature, and solar radiation on the concentrations of total mercury (TM) and dissolved gaseous mercury (DGM) were investigated in an artificial reservoir in Korea. Episodic total mercury accumulation events occurred during the rainy season as turbidity increased, indicating that the TM concentration was not controlled by direct atmospheric deposition. The DGM

Myung-Chan Ahn; Bomchul Kim; Thomas M. Holsen; Seung-Muk Yi; Young-Ji Han




E-print Network

contribution to total DIC dependent upon the pH of the water in question. Dissolved CO2 has the further Hydrologic exports of carbon (C) from watersheds represent a key connection between terrestrial and aquatic ecosystems. Hydrologic C exports occur in a variety of forms and size fractions, including organic C

Lehmann, Johannes


Ocean WarmingAcidification Synergism Undermines Dissolved Organic Matter Assembly  

PubMed Central

Understanding the influence of synergisms on natural processes is a critical step toward determining the full-extent of anthropogenic stressors. As carbon emissions continue unabated, two major stressorswarming and acidificationthreaten marine systems on several scales. Here, we report that a moderate temperature increase (from 30C to 32C) is sufficient to slow even hinderthe ability of dissolved organic matter, a major carbon pool, to self-assemble to form marine microgels, which contribute to the particulate organic matter pool. Moreover, acidification lowers the temperature threshold at which we observe our results. These findings carry implications for the marine carbon cycle, as self-assembled marine microgels generate an estimated global seawater budget of ~1016 g C. We used laser scattering spectroscopy to test the influence of temperature and pH on spontaneous marine gel assembly. The results of independent experiments revealed that at a particular point, both pH and temperature block microgel formation (32C, pH 8.2), and disperse existing gels (35C). We then tested the hypothesis that temperature and pH have a synergistic influence on marine gel dispersion. We found that the dispersion temperature decreases concurrently with pH: from 32C at pH 8.2, to 28C at pH 7.5. If our laboratory observations can be extrapolated to complex marine environments, our results suggest that a warmingacidification synergism can decrease carbon and nutrient fluxes, disturbing marine trophic and trace element cycles, at rates faster than projected. PMID:25714090

Chen, Chi-Shuo; Anaya, Jesse M.; Chen, Eric Y-T; Farr, Erik; Chin, Wei-Chun



Ocean warming-acidification synergism undermines dissolved organic matter assembly.  


Understanding the influence of synergisms on natural processes is a critical step toward determining the full-extent of anthropogenic stressors. As carbon emissions continue unabated, two major stressors-warming and acidification-threaten marine systems on several scales. Here, we report that a moderate temperature increase (from 30C to 32C) is sufficient to slow- even hinder-the ability of dissolved organic matter, a major carbon pool, to self-assemble to form marine microgels, which contribute to the particulate organic matter pool. Moreover, acidification lowers the temperature threshold at which we observe our results. These findings carry implications for the marine carbon cycle, as self-assembled marine microgels generate an estimated global seawater budget of ~1016 g C. We used laser scattering spectroscopy to test the influence of temperature and pH on spontaneous marine gel assembly. The results of independent experiments revealed that at a particular point, both pH and temperature block microgel formation (32C, pH 8.2), and disperse existing gels (35C). We then tested the hypothesis that temperature and pH have a synergistic influence on marine gel dispersion. We found that the dispersion temperature decreases concurrently with pH: from 32C at pH 8.2, to 28C at pH 7.5. If our laboratory observations can be extrapolated to complex marine environments, our results suggest that a warming-acidification synergism can decrease carbon and nutrient fluxes, disturbing marine trophic and trace element cycles, at rates faster than projected. PMID:25714090

Chen, Chi-Shuo; Anaya, Jesse M; Chen, Eric Y-T; Farr, Erik; Chin, Wei-Chun



Corals concentrate dissolved inorganic carbon to facilitate calcification.  


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

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



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


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.  


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



Dissolved air-flotation processes. Technical report  

Microsoft Academic Search

The theories and applications of various dissolved-air-flotation clarifiers (Supracell, Sandfloat, Floatpress, and Sedifloat) are presented. Supracell is a high-rate dissolved-air-flotation clarifier with only 3 to 5 minutes of detention time. Major application of Supracell is industrial-effluent treatment. Sandfloat is a package plant consisting of flocculation, dissolved-air floatation and automatic backwash filtration, and designed for either potable water treatment or tertiary

M. Krofta; L. K. Wang



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)



Ph.D. Recipients listed by recipient. 1 1937 Ablard, James Elbert D.Sc. Advisor: J. C. Warner Equivalent conductance, dissociation constants and heats of dissociation of triethylamine in  

E-print Network

.D. Advisor: D. J. Hartshorne Regulation of Mg ++- ATPase and contraction in smooth muscle 1956 Albright Almodovar, Ismael Ph.D. Advisor: T. P. Kohman Thorium isotopes method for dating marine sediments 1973 Synthesis, boron-11 shift assignments and correlations for halogenated decaboranes, carboranes

Kurnikova, Maria


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

SciTech Connect

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

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



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


Investigating Students' Understanding of the Dissolving Process  

ERIC Educational Resources Information Center

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

Naah, Basil M.; Sanger, Michael J.



Transient Dissolved Organic Carbon Through Soils  

Microsoft Academic Search

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

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



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



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 ...


Influence of Dissolved Organic Matter on Acute Toxicity of Zinc to Larval Fathead Minnows ( Pimephales promelas )  

Microsoft Academic Search

We conducted laboratory toxicity tests in support of the development of a biotic ligand model (BLM) to predict acute toxicity\\u000a of zinc (Zn) to fathead minnows (Pimephales promelas). To test the effect of dissolved organic matter (DOM) on Zn toxicity, we exposed larval fathead minnows to Zn in water containing\\u000a elevated concentrations of dissolved organic carbon (DOC) in 96-h static-renewal

Robert B. Bringolf; Brady A. Morris; Connie J. Boese; Robert C. Santore; Herbert E. Allen; Joseph S. Meyer



Effect of Abiotic and Biotic Factors on the Photo-Induced Production of Dissolved Gaseous Mercury  

Microsoft Academic Search

This study was conducted to evaluate the contribution of environmental factors such as solar radiation and dissolved organic\\u000a matter (DOM) on the photo-induced dissolved gaseous mercury (DGM) production through laboratory experiments using field water\\u000a samples collected from wetlands. DGM production was more significantly influenced by UVB intensity than UVA. DGM formation\\u000a was also significantly affected by DOM chemical structure\\/composition rather

Sehee Oh; Moon-Kyung Kim; Young-Min Lee; Kyung-Duk Zoh


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.



Dissolved gas and ultrasonic cavitation--a review.  


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

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



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



A unit for collection of dissolved oxygen and water column temperature at multiple depths  

Technology Transfer Automated Retrieval System (TEKTRAN)

A 2004 field study conducted during actual channel catfish Ictalurus punctatus harvests, and a small-scale research study conducted in 2005, required continuous collection of dissolved oxygen concentration and temperature at two depths in the water column. The on-farm study required data collection...



EPA Science Inventory

Model stream chronic dosing studies (42 d) were conducted with three total dissolved solids (TDS) recipes. The recipes differed in composition of major ions. Community scale emergence was compared with single-species responses conducted simultaneously using the whole effluent tox...


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).

Li, Xiuli; Hu, Chaoyong; Liao, Jin; Bao, Liangliang; Mao, Qixi



Integration of dissolved gas flotation and nanofiltration for M. aeruginosa and associated microcystins removal.  


The removal of Microcystis aeruginosa and associated microcystins was investigated by a dissolved gas flotation (preceded by coagulation/flocculation)-nanofiltration (NF) sequence. The experiments were conducted with a freshwater spiked with M. aeruginosa cell aggregates to simulate a naturally occurring bloom. Two types of gases were used in the flotation pre-treatment, air (DAF) and a mixture of CO(2)/air. Very good results in terms of NF fluxes, overall removal efficiencies and final water quality were achieved with both sequences. However, the CO(2)/air mixture presented no benefit to the overall sequence, both in terms of toxin release to water during flotation and lower natural organic matter removal by NF, which was due to an overall negative effect of the acid pH. NF was able to completely remove cyanobacteria (100% removal efficiency of chlorophyll a) and microcystins (always under the quantification limit), regardless of the pre-treatment used and the water recovery rate (up to 84%). Therefore, DAF-NF sequence is a safe barrier against M. aeruginosa and microcystins in drinking water. In addition, it ensures an excellent control of particles, disinfection by-products formation, and other micropollutants that may be present in raw water. PMID:16860837

Teixeira, Margarida Ribau; Rosa, Maria Joo



Tracing solid waste leachate in groundwater using ?13 C from dissolved inorganic carbon.  


Tracers can be used to monitor emissions of leachate from landfills in order to detect hydrological pathways and to evaluate environmental pollution. We investigated the stable carbon isotope ratio (?(13)C-? CO (2)) in dissolved inorganic carbon and tritium ((3)H) in water, in addition to the tracers of pollution commonly found in relatively high concentrations in leachate, such as chloride (Cl), organic matter (COD), nitrogen (total and NH(4)-N), iron (Fe), electrical conductivity (EC) and pH. The sampling was performed at seven landfills in the south-eastern part of Norway during a period of 5 years. The objective was to evaluate the potential for tracing leachate in the environment with emphasis on groundwater pollution. By measuring the ?(13)C-? CO (2) in leachates, groundwaters and surface waters, the influence of leachate can be identified. The value of ?(13)C-? CO (2) varied from-5.5 to 25.9 in leachate, from-25.4 to 14.7 in groundwater and from-19.7 to-13.1 in creeks. A comparison of the carbon isotope ratio with COD, EC and the concentrations of total and NH (4)-N, Cl and Fe showed that ?(13)C-? CO (2) is a good tracer for leachate due to higher sensitivity compared to other parameters. The mean concentrations of all the studied parameters were higher in the leachate samples; however, only the carbon isotope ratio showed significant differences between all the groups with strong and middle pollution and samples with low pollution, showing that it can be used as a convenient tracer for leachate in groundwater and surface water. The carbon isotope ratio showed strong correlation between nitrogen, EC and bicarbonate, but not with pH. Tritium was only sporadically found in measureable concentrations and is not considered as a suitable tracer at the sampled locations. PMID:22462764

Haarstad, Ketil; Mhlum, Trond



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


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



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)



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.



NSDL National Science Digital Library

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


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

NASA Astrophysics Data System (ADS)

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

Colman, J. A.



When dissolved is not truly dissolved--the importance of colloids in studies of metal sorption on organic matter.  


In controlled metal sorption experiments, the equilibrium distribution coefficient is a key variable quantifying sorbate partitioning across the solid-solution interface. Separation of metals into 'dissolved' and 'particulate' fractions is commonly achieved with syringe filtration, where the boundary is somewhat arbitrarily dictated by the limited selection of available pore sizes. Investigations involving natural organic matter, such as bacterial cells or plant tissues, are especially prone to experimental artifacts if the substrate releases abundant colloidal compounds that contribute to sorption by binding free metal cations in a pH-dependent fashion yet pass through conventional filters, causing the truly dissolved fraction to be grossly overestimated. We observed this phenomenon during a study of lanthanide sorption on a marine macroalga, Ulva lactuca, as a function of pH. At low ionic strength, distribution coefficients calculated for a 0.22-?m size cutoff falsely imply that metal sorption reverses to gradual release above pH 4.6, instead of continuing to increase. Centrifuging the filtrates in Amicon Ultra units (30 and 3 kDa molecular weight cutoff) revealed a mounting proportion of colloid-bound metal, constituting up to 95% of the 'dissolved' (<0.22 ?m) fraction near pH 8. Measurements of DOC concentrations suggest this being due to pH-dependent binding of free metal cations to a fixed pool of organic colloids. The process is well described with a simple 2-site Langmuir isotherm in 0.05, 0.5, and 5.0M NaCl. Using this model to correct the original distribution coefficients not only removed the spurious reversal at low ionic strength, but also uncovered a prominent suppressive effect on the intermediate and high ionic strength data that had initially gone undetected. Ultra-filtration may thus be an essential analytical tool for proper characterization and interpretation of metal sorption on organic matter over a wide range of experimental conditions. Some implications are discussed for the use of biosorbents in the remediation of metal-contaminated waste waters. PMID:21652006

Schijf, Johan; Zoll, Alison M



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.



Role of some organic inhibitors on the oxidation of dissolved sulfur dioxide by oxygen in rainwater medium.  


In August 2012, eight rainwater samples were collected and analyzed for pH and metal ions, viz., iron, copper, and manganese. The pH was within the range 6.84-7.65. The rate of oxidation of dissolved sulfur dioxide was determined using these rainwater samples as reaction medium. Kinetics was defined by the rate law: -d[S(IV)]/dt = R o = k o[S(IV)

Dhayal, Yogpal; Chandel, C P S; Gupta, K S



Dissolved organic carbon and sulfate sorption by spodosol mineral horizons  

SciTech Connect

Carbon cycling in soils is an important process that involves the movement of large amounts of dissolved organic carbon (DOC) within the soil profile. Recent work in a variety of soils has indicated that DOC sorption properties of mineral horizons play an important role in the retention of DOC. As part of the Watershed Manipulation Project at Bear Brook Watershed in Maine (BBWM), the solubilization and movement of carbon in terrestrial and aquatic ecosystems were evaluated. For the study, the objectives were to: (1) determine the sorption properties of mineral horizons present on the BBWM watersheds for SO4 and DOC; (2) evaluate the effect of solution pH and temperature on soil DOC sorption; and (3) examine competitive sorption effects between DOC and SO4.

Vance, G.F.; David, M.B.



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,


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

NASA Astrophysics Data System (ADS)

Reduced iron, Fe(II), accounts for a significant fraction of dissolved Fe across many natural surface waters despite its rapid oxidation under oxic conditions. Here we investigate the temporal and spatial variation in dissolved Fe redox state in a high dissolved organic matter (DOM) estuarine system, the River Beaulieu. We couple manual sample collection with the deployment of an autonomous in situ analyser, designed to simultaneously measure dissolved Fe(II) and total dissolved Fe, in order to investigate processes operating on the diurnal timescale and to evaluate the performance of the analyser in a high DOM environment. Concentrations of dissolved Fe available to the ligand ferrozine are elevated throughout the estuary (up to 21?M in freshwater) and notably higher than those previously reported likely due to seasonal variation. Fe(II) is observed to account for a large, varying fraction of the dissolved Fe available to ferrozine (25.512.5%) and this fraction decreases with increasing salinity. We demonstrate that the very high DOM concentration in this environment and association of this DOM with dissolved Fe, prevents the accurate measurement of dissolved Fe concentrations in situ using a sensor reliant on rapid competitive ligand exchange.

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



Redox and pH constraints in the subseafloor root zone of the TAG hydrothermal system, 26^o N Mid-Atlantic Ridge [rapid communication  

NASA Astrophysics Data System (ADS)

Experiments were conducted at 375-400 C, 500 bars to assess the role of redox and pH on Fe, Cu and H 2S concentrations at temperatures, pressures and total dissolved chloride concentrations applicable to the Trans-Atlantic Geo-Traverse (TAG) hydrothermal system at 26 N, Mid-Atlantic Ridge. The magnetite-bornite-anhydrite mineral assemblage imposed redox constraints, while pH was buffered with a 0.65 molal Na-K-Cl-bearing aqueous fluid coexisting with K-feldspar, muscovite and quartz. Results indicate a strong inverse correlation between dissolved Cu and H 2S (aq), whereas dissolved Fe is more sensitive to pH. Magnetite-bornite-anhydrite-fluid equilibria is characterized by unusually low mFe / mCu (molar) ratio and low H 2(aq)-H 2S (aq) activities. To form this mineral assemblage during subseafloor hydrothermal alteration, however, requires elevated fluid / rock mass ratios, such that the ferrous iron and sulfur in the rock become sufficiently depleted to render pyrite and chalcopyrite unstable. The relatively high Cu concentrations, the low H 2S (aq) and mFe / mCu ratios observed at TAG vent fluids are consistent with constraints imposed by magnetite-bornite-anhydrite-fluid equilibria at pH of approximately 4.9. Available chemical data confirm that the TAG hydrothermal system has experienced elevated fluid / rock mass ratios in keeping with the extent of mass transfer needed to generate oxidizing, low H 2S (aq) conditions.

Foustoukos, Dionysis I.; Seyfried, W. E.



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)



Complexation with dissolved organic matter and solubility control of heavy metals in sandy soil  

Microsoft Academic Search

The complexation of heavy metals with dissolved organic matter (DOM) in the environment influences the solubility and mobility of these metals. In this paper, we measured the complexation of Cu, Cd, Zn, Ni, and Pb with DOM in the soil solution at pH 3.7-6.1 using a Donnan membrane technique. The results show that the DOM-complexed species is generally more significant

Liping Weng; Erwin J. M. Temminghoff; Stephen Lofts; Edward Tipping; Riemsdijk van W. H




Microsoft Academic Search

The reaction rate of sodium sulfite was studied as a function of oxygen ;\\u000a concentration, NaSO\\/O ratio, temperature, catalyst, pH and ;\\u000a surface\\/volume ratio.The reaction rate of hydrazine with dissolved oxygen was ;\\u000a also studied. Oxygen removal is incomplete when the sulfite to oxygen ratio is ;\\u000a leas than the stoichiometric quantity. With the stoichiometric quantities of ;\\u000a oxygen and



Design and research on the optical sensor of dissolved oxygen in water based on fluorescence quenching  

Microsoft Academic Search

A novel optical technology for on-line monitoring of DO (Dissolved Oxygen) is reported. As a DO sensor in water, Ruthenium (II) complex (Ru(ph2phen)2+3) adsorbed on silica 60 gel particles emitted strong pink fluorescence steadily when a 470 nm wavelength blue LED (light-emitting diode) shined. The fluorescence could be quenched with molecule oxygen sufficiently; the higher DO concentration is, the weaker

Li Sun; Wen-yuan Dai; Jian Bao; Jin-zu Wang



The ozonation of pyruvic acid in aqueous solutions catalyzed by suspended and dissolved manganese  

Microsoft Academic Search

Reaction mechanisms and kinetics of manganese-catalyzed ozonation of pyruvic acid in aqueous solution are investigated. Experiments performed in the pH range 2.04.0 show that the reactivity is strongly enhanced by heterogeneous and homogeneous catalytic mechanisms, which are activated by suspended MnO2 particles and by dissolved Mn ions, respectively. Homogeneous mechanisms and related kinetics are elucidated.

R. Andreozzi; V. Caprio; A. Insola; R. Marotta; V. Tufano



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.



Targeted, needle-free vaccinations in skin using multilayered, densely-packed dissolving microprojection arrays.  


Targeting of vaccines to abundant immune cell populations within our outer thin skin layers using miniaturized devices-much thinner than a needle and syringe, could improve the efficacy of vaccines (and other immunotherapies). To meet this goal, a densely packed dissolving microprojection array (dissolving Nanopatch) is designed, achieving functional miniaturization by 1) formulating small microneedles (two orders of magnitude smaller than a standard needle and syringe) and 2) multiple layering of the payload within microprojections with tight tolerances (of the order of a micrometer). The formulation method is suitable to many vaccines because it is without harsh or complex chemical processes, and it is performed at low temperatures and at a neutral pH. When the formulated dNPs are applied to skin, consistent and robust penetration is achieved, rapidly targeting the skin strata of interest (<5 min; significantly faster than larger dissolving microneedles that have been previously reported). Resultant diffusion is significantly enhanced within the dermis compared with the epidermis. Using two different antigens (ovalbumin and a commercial trivalent influenza vaccine [Fluvax2008]), the administration of these dissolving patches generate robust systemic immune responses in a mouse model. To the authors' knowledge, this is the first report of successful vaccination with any form of dissolving microneedles. The patches made by this method therefore have the potential for pain-free, needle-free, and effective vaccination in humans. PMID:20665628

Raphael, Anthony P; Prow, Tarl W; Crichton, Michael L; Chen, Xianfeng; Fernando, Germain J P; Kendall, Mark A F



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



Lithium ion conducting electrolytes  


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

Angell, C.A.; Liu, C.



Lithium ion conducting electrolytes  


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

Angell, C. Austen (Tempe, AZ); Liu, Changle (Tempe, AZ)



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



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

Microsoft Academic Search

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

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



A simple headspace equilibration method for measuring dissolved methane  

USGS Publications Warehouse

Dissolved methane concentrations in the ocean are close to equilibrium with the atmosphere. Because methane is only sparingly soluble in seawater, measuring it without contamination is challenging for samples collected and processed in the presence of air. Several methods for analyzing dissolved methane are described in the literature, yet none has conducted a thorough assessment of the method yield, contamination issues during collection, transport and storage, and the effect of temperature changes and preservative. Previous extraction methods transfer methane from water to gas by either a "sparge and trap" or a "headspace equilibration" technique. The gas is then analyzed for methane by gas chromatography. Here, we revisit the headspace equilibration technique and describe a simple, inexpensive, and reliable method to measure methane in fresh and seawater, regardless of concentration. Within the range of concentrations typically found in surface seawaters (2-1000 nmol L-1), the yield of the method nears 100% of what is expected from solubility calculation following the addition of known amount of methane. In addition to being sensitive (detection limit of 0.1 ppmv, or 0.74 nmol L-1), this method requires less than 10 min per sample, and does not use highly toxic chemicals. It can be conducted with minimum materials and does not require the use of a gas chromatograph at the collection site. It can therefore be used in various remote working environments and conditions.

Magen, C; Lapham, L.L.; Pohlman, John; Marshall, Kristin N.; Bosman, S.; Casso, Michael; Chanton, J.P.



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, Brbel; Freibauer, Annette



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 g/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, Brbel; Freibauer, Annette



Lithium ion conducting ionic electrolytes  


A liquid, predominantly lithium-conducting, ionic electrolyte is described which has exceptionally high conductivity at temperatures of 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)



Stella Koutros, Ph.D.

Dr. Koutros received her M.P.H. and Ph.D. in epidemiology from Yale University. She completed her doctoral work through the Yale-NCI partnership training program in cancer epidemiology, conducting research in the Occupational and Environmental Epidemiology Branch (OEEB). In 2008, upon completion of her doctorate she became a fellow in OEEB; she was appointed to the position of tenure-track investigator in 2015.


Nonideal binding between dissolved humic acids and polyaromatic hydrocarbons.  


Interactions between hydrophobic organic chemicals (HOCs) and dissolved organic matter (DOM) are of environmental significance due to their influence on mobility and bioavailability of HOCs. The linear dissolution concept has been widely used to describe the interactions between HOCs and DOM, but it may not be correct. To date there is no systematic evaluation of nonideal interactions between HOCs and DOM. Therefore, this study employed a dialysis method to investigate sorption, desorption, and competition of two polyaromatic hydrocarbons (PAHs), phenanthrene (PHE) and pyrene (PYR), by two DOMs at pHs of 4, 7, and 11. Nonlinear interactions between PAHs and DOM and desorption hysteresis were consistently observed. The isotherm nonlinearity factor, nvalue, increased significantly after the addition of cosolutes, indicating the occupation of specific binding sites by the cosolute molecules. Significant influence of pH on PAHs-DOM interaction was also observed (higher binding coefficients, stronger desorption hysteresis, and increased nonlinearity at lower pH). This study for the first time systematically showed the nonideal binding behavior of PAHs by DOM. A more complete model rather than linear distribution is required to describe the interactions between HOCs and DOM. Conformation changes of DOM molecules were proposed to explain the interactions between HOCs and DOM. PMID:17948796

Pan, Bo; Ghosh, Saikat; Xing, Baoshan



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



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


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

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



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

USGS Publications Warehouse

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

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



Dissolved aluminum in the Gulf of Mexico  

E-print Network

similarity of the Gulf of Mexico and Mediterranean profiles may be a function of the residence time of the water in each basin. The concentration of dissolved aluminum in the deeper waters of the Gulf of Mexico may be a combination of resuspension... occurs at a depth of approximately 1 5 0 t o 2 0 0 meters, and i s attributed t o biological uptake or particle adsorption in the productive waters above the t he rmocl i ne . The residence time of dissolved aluminum i s shown t o be partially a...

Myre, Peggy Lynne



Effect of pH values on surface modification and solubility of phosphate bioglass-ceramics in the CaO-P 2O 5-Na 2O-SrO-ZnO system  

NASA Astrophysics Data System (ADS)

The bioactive glass-ceramics in the CaO-P 2O 5-Na 2O-SrO-ZnO system were synthesized by the sol-gel technique, and then chemically treated at different pH values to study the solubility and surface modification. Samples sintered at 650 C for 4 h consisted of the crystalline phase ?-Ca 2P 2O 7 and the glass matrix. After soaking in the solution at pH 1.0, the residual glass matrix on the surface appeared entirely dissolved and no new phase could be detected. Whereas at pH 3.0, web-like layer exhibiting peaks corresponding to CaP 2O 6 was formed and covered the entire surface of the sample. When conducted at pH 10.0, only part of the glass matrix was dissolved and a new phase Ca 4P 6O 19 was precipitated, forming the petaline layer. The chemical treatment can easily change the surface morphologies and phase composition of this bioactive glass-ceramics. The higher level of surface roughness resulting from the new-formed layer would improve the interface bonding and benefit for cell adhesion.

Li, Xudong; Cai, Shu; Zhang, Wenjuang; Xu, Guohua; Zhou, Wei



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...


Dissolved\\/dispersed Petroleum Aromatic Hydrocarbons in the So Sebastio Channel, So Paulo, Brazil  

Microsoft Academic Search

A monitoring programme at So Sebastio Channel, So Paulo, Brazil, was conducted in terms of dissolved\\/dispersed petroleum aromatic hydrocarbons (DDPAH) in water analysed by flourescence spectroscopy. The study was done in order to establish a baseline data for this area and verify the petroleum hydrocarbon influence from the oil terminal (DTCS) and other human activities over the channel. The DDPAH

Eliete Zanardi; Mrcia Caruso B??cego; Rolf Roland Weber




EPA Science Inventory

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



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...


A community-wide intercomparison exercise for the determination of dissolved iron in seawater  

Microsoft Academic Search

The first large-scale international intercomparison of analytical methods for the determination of dissolved iron in seawater was carried out between October 2000 and December 2002. The exercise was conducted as a rigorously blind comparison of 7 analytical techniques by 24 international laboratories. The comparison was based on a large volume (700 L), filtered surface seawater sample collected from the South

Andrew R. Bowie; Eric P. Achterberg; Peter L. Croot; Hein J. W. de Baar; Patrick Laan; James W. Moffett; Simon Ussher; Paul J. Worsfold




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...



Technology Transfer Automated Retrieval System (TEKTRAN)

The objective of this study was to evaluate the suitability of a hand-held reflectometer, hydrometers, and measurements of electrical conductivity (EC) and manure total solids (TS) concentrations for determining dissolved phosphorus (DP) in dairy manure suspensions, and to compare the estimated DP c...



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...


Dissolved air flotation of polishing wastewater from semiconductor manufacturer.  


The feasibility of the dissolved air flotation (DAF) process in treating chemical mechanical polishing (CMP) wastewater was evaluated in this study. Wastewater from a local semiconductor manufacturer was sampled and characterised. Nano-sized silica (77.6 nm) with turbidity of 130 +/- 3 NTU was found in the slightly alkaline wastewater with traces of other pollutants. Experimental results indicated removal efficiency of particles, measured as suspended particle or turbidity, increased with increasing concentration of cationic collector cetyltrimethyl ammonium bromide (CTAB). When CTAB concentration was 30 mg/L, pH of 6.5 +/- 0.1 and recycle ratio of 30%, very effective removal of particles (> 98%) was observed in saturation pressure range of 4 to 6 kg/cm2, and the reaction proceeded faster under higher pressure. Similarly, the reaction was faster under the higher recycle ratio, while final removal efficiency improved slightly as the recycle ratio increased from 20 to 40%. An insignificant effect of pH on treatment efficiency was found as pH varied from 4.5 to 8.5. The presence of activator, Al3+ and Fe3+, enhanced the system performance. It is proposed that CTAB adsorbs on silica particles in polishing wastewater through electrostatic interaction and makes particles more hydrophobic. The increase in hydrophobicity results in more effective bubble-particle collisions. In addition, flocculation of silica particles through bridging effect of collector was found; it is believed that flocculation of particles also contributed to flotation. Better attachment between gas bubble and solid, higher buoyancy and higher air to solid ratio all lead to effective flotation. PMID:16752774

Liu, J C; Lien, C Y



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

USGS Publications Warehouse

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

Cravotta, C.A., III



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 pH6. 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. PMID:25045321



Monitor for Hydrogen Dissolved in Transformer Oil  

Microsoft Academic Search

A new monitor of hydrogen gas dissolved in transformer oil is described and tested under different conditions. Hydrogen diffuses from the oil through a permeable membrane into the monitor and reacts electrochemically with oxygen from the ambiant air in a fuel cell type arrangement. The monitor can be installed on a transformer for in-service continuous analysis of evolved hydrogen. It

G. Belanger; M. Duval




EPA Science Inventory

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


Light water: how the nuclear dream dissolved  

Microsoft Academic Search

This book is an interpretation of how the nuclear dream which emerged at the end of World War II and seemed to be on the verge of realization in the aftermath of the 1973 OPEC embargo dissolved during the ensuing four years. The central argument is that the origin of this disappointment can be found in circumstances that span the

I. C. Bupp; J. C. Derian



Dissolving Microneedles for Transdermal Drug Delivery  

PubMed Central

Microfabrication technology has been adapted to produce micron-scale needles as a safer and painless alternative to hypodermic needle injection, especially for protein biotherapeutics and vaccines. This study presents a design that encapsulates molecules within microneedles that dissolve within the skin for bolus or sustained delivery and leave behind no biohazardous sharp medical waste. A fabrication process was developed based on casting a viscous aqueous solution during centrifugation to fill a micro-fabricated mold with biocompatible carboxymethylcellulose or amylopectin formulations. This process encapsulated sulforhodamine B, bovine serum albumin, and lysozyme; lysozyme was shown to retain full enzymatic activity after encapsulation and to remain 96% active after storage for two months at room temperature. Microneedles were also shown to be strong enough to insert into cadaver skin and then to dissolve within minutes. Bolus delivery was achieved by encapsulating molecules just within microneedle shafts. For the first time, sustained delivery over hours to days was achieved by encapsulating molecules within the microneedle backing, which served as a controlled release reservoir that delivered molecules by a combination of swelling the backing with interstitial fluid drawn out of the skin and molecule diffusion into the skin via channels formed by dissolved microneedles. We conclude that dissolving microneedles can be designed to gently encapsulate molecules, insert into skin, and enable bolus or sustained release delivery. PMID:18261792

Lee, Jeong Woo; Park, Jung-Hwan; Prausnitz, Mark R.



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



Oceanography June 200450 Colored Dissolved Organic  

E-print Network

Oceanography June 200450 Colored Dissolved Organic in the Coastal Ocean A N O P T I C A L TO O L F been published in Oceanography, Volume 17, Number 2, a quarterly journal of The Oceanography Society. Copyright 2003 by The Oceanography Society. All rights reserved. Reproduction of any portion of this arti

Oregon, University of



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...


Acidogenesis of dairy wastewater at various pH levels  

Microsoft Academic Search

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

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



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

Microsoft Academic Search

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

Michael Bau



Assessing the concentration, speciation, and toxicity of dissolved metals during mixing of acid-mine drainage and ambient river water downstream of the Elizabeth Copper Mine, Vermont, USA  

Microsoft Academic Search

The authors determine the composition of a river that is impacted by acid-mine drainage, evaluate dominant physical and geochemical processes controlling the composition, and assess dissolved metal speciation and toxicity using a combination of laboratory, field and modeling studies. Values of pH increase from 3.3 to 7.6 and the sum of dissolved base metal (Cd+Co+Cu+Ni+Pb+Zn) concentrations decreases from 6270 to

Laurie S. Balistrieri; Robert R. Seal; Nadine M. Piatak; Barbara Paul



Effect of Livestock Slurry Ozonation and Separation on pH, Particles, and Phosphate.  


Applying slurry to arable land as fertilizer increases the risk of phosphorus (P) runoff and thereby increases the risk of eutrophication. Solid-liquid separation can reduce the excess application of P, and this study focused on the use of ozonation as an alternative chemical pretreatment for separation to improve P separation efficiency. Sow and cattle slurries were separated by screw press and flocculation+filtration. The screw press and flocculation liquid fractions and raw slurries were treated with no ozone or with low-, medium-, or high-ozone doses and then separated by centrifugation. The pH, particle size distribution, dry matter, and dissolved phosphate (PO) concentrations were measured. For separations without ozonation, pH increased by 0.15 to 0.87 pH units, and correlation analysis showed that the dissolved PO concentration decreased with increasing pH and particle removal efficiency. During ozonation, pH increased, and a shift in particle size distribution in the liquid fraction combined with an improved dry matter separation indicated particle aggregation. Ozonation thus affected the parameters found to affect dissolved PO separation, and at the highest ozone dose, dissolved PO separation efficiency increased by 7 to 81%. An ozonation pretreatment may therefore promote removal of dissolved PO from the liquid fraction during separation. PMID:25602833

Pedersen, Christina ; Hjorth, Maibritt; Hutchings, Nicholas J



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



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



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



PhD students work conditions and study environment in university- and industry-based PhD programmes  

Microsoft Academic Search

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 impact these

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



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


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

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



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


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



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.



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.; Tejneck, V.; Ash, C.; Hubova, P.; Boruvka, L.



Dissolved organic nitrogen in precipitation: Collection, analysis and atmospheric flux  

SciTech Connect

Recent studies have documented the importance of atmosphere inorganic nitrogen deposition to coastal waters. However, due to the limited number of field measurements and concerns about the reliability of measurement techniques, the aeolian flux of organic N is very uncertain. Coordinated studies have been initiated at Lewes, DE and Charlottesville, VA to evaluate collection and analysis techniques for dissolved organic nitrogen (DON) in precipitation and to provide preliminary estimate of DON wet fluxes. Sampling was conducted both manually and employing an automated wet-only collector (ACM) on a daily basis. A total of 37 events were analyzed from October 1993 through December 1994. Side-by-side comparisons of standard white HDPE buckets and stainless steel and glass collection vessels indicate sampling artifacts associate with plastic buckets. DON in precipitation appears to be highly labile, with significant losses observed in some samples within 12 hours. Analytical methods evaluated include persulfate wet chemical oxidation, UV photo-oxidation and a modified high temperature instrumental (ANTEK 7000) technique. Based on preliminary results, the volume-weighted average concentration of DON in precipitation at the mid-Atlantic coast is 9.1 {micro}moles/1. On an annual basis, DON compromises 23% of the total dissolved nitrogen in precipitation, varying from 0--64% on an event basis. From an ecological perspective, DON wet flux represents a quantitatively important exogenous source of N to coastal waters such as Chesapeake Bay.

Scudlark, J.R.; Church, T.M. [Univ. of Delaware, Lewes, DE (United States). Graduate Coll. of Marine Studies; Russell, K.M. [Univ. of Virginia, Charlottesville, VA (United States). Dept. of Environmental Sciences; [Univ. of Delaware, Lewes, DE (United States). Graduate Coll. of Marine Studies; Montag, J.A.; Maben, J.R.; Keene, W.C.; Galloway, J.N. [Univ. of Virginia, Charlottesville, VA (United States). Dept. of Environmental Sciences



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



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


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

Heddam, Salim



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: (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.



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 publically-unavailable water column measurements of the dissolved inorganic carbon system and associated biogeochemical parameters (oxygen, nutrients, etc.) made on 25 cruises in the subarctic and Arctic regions dating from as far back as 1974. The measurements are primarily from the western side of the Canadian Arctic, but also include data 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 dataset 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 yr and provides an opportunity to increase our understanding of temporal changes in the inorganic carbon system in northern waters and the Arctic Ocean. The dataset is available for download on the CDIAC website: (doi:10.3334/CDIAC/OTG.IOS_ARCT_CARBN).

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



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.



Fast dissolving strips: A novel approach for the delivery of verapamil  

PubMed Central

Objective: Fast dissolving drug delivery system offers a solution for those patients having difficulty in swallowing tablets/capsules etc. Verapamil is a calcium channel blocker used as an antianginal, antiarrhythmic, and antihypertensive agent with extensive first pass metabolism which results in less bioavailability. This work investigated the possibility of developing verapamil fast dissolving strips allowing fast, reproducible drug dissolution in the oral cavity; thus bypassing first pass metabolism. Materials and methods: The fast dissolving strips were prepared by solvent casting technique with the help of HPMC E6 and maltodextrin. The strips were evaluated for drug content uniformity, film thickness, folding endurance, in vitro disintegration time, in vitro dissolution studies, surface pH study, and palatability study. Results: Official criteria for evaluation parameters were fulfilled by all formulations. Disintegration time showed by formulations was found to be in range of 20.428.6 sec. Based on the evaluation parameters, the formulation containing 2% HPMC E6 and 3.5% maltodextrin showed optimum performance against other formulations. Conclusion: It was concluded that the fast dissolving strips of verapamil can be made by solvent casting technique with enhanced dissolution rate, taste masking, and hence better patient compliance and effective therapy PMID:21180465

Kunte, S.; Tandale, P.



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; Kstner, Matthias



Modelling of dissolved oxygen in the Danube River using artificial neural networks and Monte Carlo Simulation uncertainty analysis  

NASA Astrophysics Data System (ADS)

This paper describes the training, validation, testing and uncertainty analysis of general regression neural network (GRNN) models for the forecasting of dissolved oxygen (DO) in the Danube River. The main objectives of this work were to determine the optimum data normalization and input selection techniques, the determination of the relative importance of uncertainty in different input variables, as well as the uncertainty analysis of model results using the Monte Carlo Simulation (MCS) technique. Min-max, median, z-score, sigmoid and tanh were validated as normalization techniques, whilst the variance inflation factor, correlation analysis and genetic algorithm were tested as input selection techniques. As inputs, the GRNN models used 19 water quality variables, measured in the river water each month at 17 different sites over a period of 9 years. The best results were obtained using min-max normalized data and the input selection based on the correlation between DO and dependent variables, which provided the most accurate GRNN model, and in combination the smallest number of inputs: Temperature, pH, HCO3-, SO42-, NO3-N, Hardness, Na, Cl-, Conductivity and Alkalinity. The results show that the correlation coefficient between measured and predicted DO values is 0.85. The inputs with the greatest effect on the GRNN model (arranged in descending order) were T, pH, HCO3-, SO42- and NO3-N. Of all inputs, variability of temperature had the greatest influence on the variability of DO content in river body, with the DO decreasing at a rate similar to the theoretical DO decreasing rate relating to temperature. The uncertainty analysis of the model results demonstrate that the GRNN can effectively forecast the DO content, since the distribution of model results are very similar to the corresponding distribution of real data.

Antanasijevi?, Davor; Pocajt, Viktor; Peri?-Gruji?, Aleksandra; Risti?, Mirjana



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.



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)



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.



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



Dissolving A Substance in Different Liquids  

NSDL National Science Digital Library

In this activity, students make colored sugar and add it to water, alcohol, and oil to discover some interesting differences in dissolving. 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.

James Kessler



Fast-response sensors for dissolved oxygen  

Microsoft Academic Search

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

A. Sheila Holmes-Smith; Alan Hamill; Mahesh Uttamlal; Michael Campbell; David Bailly



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 26.5N x 38.5W, 32.5N x 30.0W, and 22.5N x 28.5W) of 5.7 moles of oxygen consumed m?2 yr?1 for

R. M. Key



Conductive plastics  

Microsoft Academic Search

Plastics have been widely used for several decades, due to their many advantageous properties including moldability, ruggedness, and low cost. For applications in electricity and electronics, applications for plastics have always been as dielectrics, due to their inherent property as electrical insulators. The invention of conductive plastics has enabled the creation of many products that have previously not existed. This

Barry M. Lunt; A. Brent Strong



Conduct Disorder  


... They often break laws or behave in an antisocial manner. Treatment of children with conduct disorder can be complex and challenging. Treatment can be provided in a variety of different settings depending on the severity of the behaviors. Adding to the challenge of treatment are the ...


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.



Superhydrophobic porous surfaces: dissolved oxygen sensing.  


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

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



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

NASA Astrophysics Data System (ADS)

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

De Young, R.; Ganoe, R.



Qualitative changes of riverine dissolved organic matter at low salinities due to flocculation  

NASA Astrophysics Data System (ADS)

The flocculation of dissolved organic matter (DOM) was studied along transects through three boreal estuaries. Besides the bulk concentration parameters, a suite of DOM quality parameters were investigated, including colored DOM (CDOM), fluorescent DOM, and the molecular weight of DOM as well as associated dissolved iron concentrations. We observed significant deviations from conservative mixing at low salinities (<2) in the estuarine samples of dissolved organic carbon (DOC), UV absorption (a(CDOM254)), and humic-like fluorescence. The maximum deviation from conservative mixing for DOC concentration was -16%, at salinities between 1 and 2. An associated laboratory experiment was conducted where an artificial salinity gradient between 0 and 6 was created. The experiment confirmed the findings from the estuarine transects, since part of the DOC and dissolved iron pools were transformed to particulate fraction (>0.2 m) and thereby removing them from the dissolved phase. We also measured flocculation of CDOM, especially in the UV region of the absorption spectrum. Protein-like fluorescence of DOM decreased, while humic-like fluorescence increased because of salt-induced flocculation. Additionally, there was a decrease in molecular weight of DOM. Consequently, the quantity and quality of the remaining DOM pool was significantly changed after influenced to flocculation. Based on these results, we constructed a mechanistic, two-component flocculation model. Our findings underline the importance of the coastal filter, where riverine organic matter is flocculated and exported to the sediments.

Asmala, Eero; Bowers, David G.; Autio, Riitta; Kaartokallio, Hermanni; Thomas, David N.



Water What-ifs: Water Quality and Dissolved Oxygen  

NSDL National Science Digital Library

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

April J. Cleveland


pH Calculation  

NSDL National Science Digital Library

This pair of pH calculation programs serves as an excellent tool for anyone wishing to calculate the pH of a solution containing multiple acids and bases. These programs allow practitioners to predict the pH of simple and complex acid/base solutions and buffers. They may be downloaded free of charge via the website. Users are encouraged to carefully read the guides provided by the author.

Johansson, Stig


Polarographic behaviors of diclofenac sodium in the presence of dissolved oxygen and its analytical application.  


The polarographic response characteristics of diclofenac sodium were investigated in 0.25 M HAc-NaAc (pH 5.0) supporting electrolyte in the absence and the presence of dissolved oxygen. The results demonstrate that the reduction peak at ca. -1.10 V is a catalytic hydrogen wave after deaeration, and the reduction peak in the presence of dissolved oxygen is a so-called parallel catalytic hydrogen wave. Based on the parallel catalytic hydrogen wave, a novel method has been proposed for the determination of diclofenac sodium by single-sweep polarography. The calibration curve is linear in the range 1.2 x 10(-7)-2.6 x 10(-6)M and the detection limit is 6.0 x 10(-8)M. The proposed method is applied to the direct determination of diclofenac sodium in tablet forms and biological samples. PMID:15136163

Xu, Maotian; Chen, Liangfeng; Song, Junfeng



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



Composition, Dynamics, and Fate of Leached Dissolved Organic Matter  

E-print Network

Composition, Dynamics, and Fate of Leached Dissolved Organic Matter in Terrestrial Ecosystems Fluxes of dissolved organic matter (DOM) are an important vector for the movement of carbon (C dissolve organic carbon (DOC) and dis- solved organic nitrogen (DON) fractions], as well as DOM chemical

Neff, Jason


Conduct Disorders  

Microsoft Academic Search

Disruptive behaviorsdefined here as behaviors that are associated with diagnoses of Oppositional Defiant Disorder (ODD) or\\u000a Conduct Disorder (CD)are the most common reason for referral to mental health services for children and adolescents (Kazdin,\\u000a 2003). The behaviors that comprise these diagnoses include argumentativeness, temper tantrums, often being angry or resentful,\\u000a lying, stealing, hurting or threatening to hurt others, cruelty to

Christopher T. Barry; Lisa L. Ansel; Jessica D. Pickard; Heather L. Harrison


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.



HB-Line Dissolver Dilution Flows and Dissolution Capability with Dissolver Charge Chute Cover Off  

SciTech Connect

A flow test was performed in Scrap Recovery of HB-Line to document the flow available for hydrogen dilution in the dissolvers when the charge chute covers are removed. Air flow through the dissolver charge chutes, with the covers off, was measured. A conservative estimate of experimental uncertainty was subtracted from the results. After subtraction, the test showed that there is 20 cubic feet per minute (cfm) air flow through the dissolvers during dissolution with a glovebox exhaust fan operating, even with the scrubber not operating. This test also showed there is 6.6 cfm air flow through the dissolvers, after subtraction of experimental uncertainty if the scrubber and the glovebox exhaust fans are not operating. Three H-Canyon exhaust fans provide sufficient motive force to give this 6.6 cfm flow. Material charged to the dissolver will be limited to chemical hydrogen generation rates that will be greater than or equal to 25 percent of the Lower Flammability Limit (LFL) during normal operations. The H-Canyon fans will maintain hydrogen below LFL if electrical power is lost. No modifications are needed in HB-Line Scrap Recovery to ensure hydrogen is maintained less that LFL if the scrubber and glovebox exhaust fans are not operating.

Hallman, D.F.



Dissolved oxygen and pH monitoring within cell culture media using a hydrogel microarray sensor  

E-print Network

fluorescent agent was immobilized into a hydrogel structure via a soft lithography technique and the intensity image of the sensor varied from the target analyte concentration. A compact detection system was developed to quantify concentration of each analyte...

Lee, Seung Joon



The measurement of dissolved and gaseous carbon dioxide concentration  

NASA Astrophysics Data System (ADS)

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

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



Detoxification of Dissolved SO2 (Bisulfite) by Terricolous Mosses  

PubMed Central

Background and Aims The widespread calcifuge moss Pleurozium schreberi is moderately tolerant of SO2, whereas Rhytidiadelphus triquetrus is limited to calcareous soils in regions of the UK that were strongly affected by SO2 pollution in the 20th century. The proposition that tolerance of SO2 by these terricolous mosses depends on metabolic detoxification of dissolved bisulfite was investigated. Methods The capacities of the two mosses to accelerate loss of bisulfite from aqueous solutions of NaHSO3 were studied using DTNB [5, 5-dithio-(2-nitrobenzoic acid)] to assay bisulfite, and HPLC to assay sulfate in the incubation solutions. Incubations were performed for different durations, in the presence and absence of light, at a range of solution pH values, in the presence of metabolic inhibitors and with altered moss apoplastic Ca2+ and Fe3+ levels. Key Results Bisulfite disappearance was markedly stimulated in the light and twice as great for R. triquetrus as for P. schreberi. DCMU, an inhibitor of photosynthetic electron chain transport, significantly reduced bisufite loss. Conclusions Bisulfite (SO2) tolerance in these terricolous mosses involves extracellular oxidation using metabolic (photo-oxidative) energy, passive oxidation by adsorbed Fe3+ (only available to the calcifuge) and probably also internal metabolic detoxification. PMID:16319108




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


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



Oxidation process of dissolvable sulfide by synthesized todorokite in aqueous systems.  


Todorokite, formed from Mn(II) in supergene environments, can affect the transformation and migration of dissolvable sulfides in soils and water. In this work, todorokite was synthesized with different degrees of crystallinity, and the redox mechanism of dissolvable sulfide and todorokite was studied in both closed and open aqueous systems. The influences of pH, temperature, crystallinity, the amount of manganese oxides, and oxygen gas on S(2-) oxidation process were investigated. It is found that S(2-) was oxidized to S(0), SO3(2-), S2O3(2-) and SO4(2-), and about 90% of S(2-) was converted into S(0) in closed systems. The participation of oxygen facilitated the further oxidation of S(0) to S2O3(2-). S(0) and S2O3(2-) were formed with the conversion rates of S(2-) about 45.3% and 38.4% after 1h of reaction, respectively, and the conversion rate for S2O3(2-) increased as reaction prolonged for a longer period. In addition, todorokite was reduced to Mn(OH)2 in the presence of nitrogen gas, and its chemical stability increased when oxygen gas was admitted into the reaction system during the process. The oxidation rate of dissolvable sulfide followed a pseudo-first-order kinetic law in the initial stage (within 10min), and the initial oxidation rate constant of S(2-) increased with elevating temperature, increasing the quantity and decreasing crystallinity of todorokite. The initial oxidation rate of dissolvable sulfide decreased with continuous feeding of O2 into the test solution, possibly due to a decrease in active Mn(III) content in todorokite. The present work demonstrates the redox behaviors and kinetics of dissolvable sulfide and todorokite in aquatic environments. PMID:25746570

Gao, Tianyu; Shi, Ying; Liu, Fan; Zhang, Yashan; Feng, Xionghan; Tan, Wenfeng; Qiu, Guohong



Improved Arterial Blood Oxygenation Following Intravenous Infusion of Cold Supersaturated Dissolved Oxygen Solution  

PubMed Central

BACKGROUND One of the primary goals of critical care medicine is to support adequate gas exchange without iatrogenic sequelae. An emerging method of delivering supplemental oxygen is intravenously rather than via the traditional inhalation route. The objective of this study was to evaluate the gas-exchange effects of infusing cold intravenous (IV) fluids containing very high partial pressures of dissolved oxygen (>760 mm Hg) in a porcine model. METHODS Juvenile swines were anesthetized and mechanically ventilated. Each animal received an infusion of cold (13 C) Ringers lactate solution (30 mL/kg/hour), which had been supersaturated with dissolved oxygen gas (39.7 mg/L dissolved oxygen, 992 mm Hg, 30.5 mL/L). Arterial blood gases and physiologic measurements were repeated at 15-minute intervals during a 60-minute IV infusion of the supersaturated dissolved oxygen solution. Each animal served as its own control. RESULTS Five swines (12.9 0.9 kg) were studied. Following the 60-minute infusion, there were significant increases in PaO2 and SaO2 (P < 0.05) and a significant decrease in PaCO2 (P < 0.05), with a corresponding normalization in arterial blood pH. Additionally, there was a significant decrease in core body temperature (P < 0.05) when compared to the baseline preinfusion state. CONCLUSIONS A cold, supersaturated dissolved oxygen solution may be intravenously administered to improve arterial blood oxygenation and ventilation parameters and induce a mild therapeutic hypothermia in a porcine model. PMID:25249764

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



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


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?



Dissolving variables in connectionist combinatory logic  

NASA Technical Reports Server (NTRS)

A connectionist system which can represent and execute combinator expressions to elegantly solve the variable binding problem in connectionist networks is presented. This system is a graph reduction machine utilizing graph representations and traversal mechanisms similar to ones described in the BoltzCONS system of Touretzky (1986). It is shown that, as combinators eliminate variables by introducing special functions, these functions can be connectionistically implemented without reintroducing variable binding. This approach 'dissolves' an important part of the variable binding problem, in that a connectionist system still has to manipulate complex data structures, but those structures and their manipulations are rendered more uniform.

Barnden, John; Srinivas, Kankanahalli



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

SciTech Connect

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

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



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



Beneficial and detrimental interactive effects of dissolved organic matter and ultraviolet radiation on Zooplankton in a transparent lake  

Microsoft Academic Search

While changes in dissolved organic matter (DOM) concentrations are expected to affect zooplankton species through attenuation\\u000a of potentially damaging ultraviolet (UV) radiation, generation of potentially beneficial or harmful photoproducts, pH alteration,\\u000a and microbial food web stimulation, the combined effects of such changes on zooplankton community structure have not been\\u000a studied previously. Our purpose was to determine how an increase in

Sandra L. Cooke; Craig E. Williamson; Bruce R. Hargreaves; Donald P. Morris



Role of dissolved organic carbon in the attenuation of photosynthetically active and ultraviolet radiation in Adirondack lakes  

Microsoft Academic Search

SUMMARY 1. We surveyed eighty-five lakes located in the Adirondack Mountain Region of New York State, U.S.A., to characterize the attenuation of photosynthetically active (PAR) and ultraviolet radiation (UVR) in relation to dissolved organic carbon (DOC) concentrations and pH. Attenuation of PAR was quantified in situ. Attenuation was also inferred by measuring the light absorption of filtered lake water samples




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


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 (66.820.1%)>pyrene (48.826.4%)>chrysene (5.53.3%) 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



Scholarly Integrity Julie Simpson, Ph.D.  

E-print Network

Board site #12;Upcoming RCR Trainings New PhD student required training ~ Friday, September 27, 12 & scholarship Variable (2-3) credit Fulfills UNH doctoral and NSF RCR training requirements Tuesdays, 4 Public trust #12;Responsible Conduct of Research (RCR) & Scholarship Program Standing faculty committee

New Hampshire, University of


Photoluminescent detection of dissolved underwater trace explosives.  


A portable, rapid, and economical method for in situ trace explosive detection in aqueous solutions was demonstrated using photoluminescence. Using europium/ thenoyltrifluoroacetone as the reagent, dissolved nitroglycerin was fluorescently tagged and detected in seawater solutions without sample preparation, drying, or preconcentration. The chemical method was developed in a laboratory setting and demonstrated in a flow-through configuration using lightweight, inexpensive, commercial components by directly injecting the reagents into a continually flowing seawater stream using a small amount of organic solvent (approximately 8% of the total solution). Europium's vulnerability to vibrational fluorescence quenching by water provided the mode of detection. Without nitroglycerin in the seawater solution, the reagent's fluorescence was quenched, but when dissolved nitroglycerin was present, it displaced the water molecules from the europium/thenoyltrifluoroacetone compound and restored fluorescence. This effort focused on developing a seawater sensor, but performance comparisons were made to freshwater. The method was found to perform better in freshwater and it was shown that certain seawater constituents (such as calcium) have an adverse impact. However, the concentrations of these constituents are not expected to vary significantly from the natural seawater used herein. PMID:20364240

Langston, Tye



Novel approach of aceclofenac fast dissolving tablet.  


Fast disintegrating tablets (FDTs) have received ever increasing demand during the last decade, and the ?eld has become a hastily growing area in the pharmaceutical industry. Upon introduction into the mouth, these tablets dissolve or disintegrate in the mouth in the absence of additional water for easy administration of active pharmaceutical ingredients. Aceclofenac, an NSAID, has been recommended orally for the treatment of bone and connective tissue disorder and thus the formulation of the same resulted in development of several FDT technologies. The present aim is to formulate a tablet which disintegrate and dissolve rapidly and give its rapid onset of action: analgesic, antipyretic and anti-inflammatory action. Besides, the conventional tablets also show poor patient compliance an attempt had been made to formulate for FDT of aceclofenac by using various super disintegrants like sodium starch glycolate, croscarmellose sodium and crosspovidone (polyplasdone XL) and PEG 6000 followed by novel technique. The tablets were evaluated for friability, hardness, weight variation, disintegration time, wetting time, in vitro dissolution studies and drug content studies. It was concluded that the batch which was prepared by using combination of crosspovidone and sodium starch glycolate as a super disintegrant shows excellent disintegration time, enhance dissolution rate, taste masking and hence lead to improve efficacy and bioavailability of drug. PMID:25553683

Dave, Vivek; Yadav, Sachdev; Sharma, Swapnil; Vishwakarma, Pushpendra; Ali, Nasir



Development of a geometrically favorable canyon dissolver  

SciTech Connect

A prototype has been constructed for initial full-scale evaluation using nonfissile materials. There are four charging ports, 6 inches in diameter, connected to a 3-inch annulus. The fuel element or scrap would be loaded into disposable containers, which would be charged to the dissolver ports. For high fissile material, only the bottom four feet of the container would be used, completely isolating the fissile material in a 6-inch well below the annulus. Recirculation and mixing are provided with a central air lift which is capable of recirculating 50 to 100 gallons per minute. Dissolver solution flows up the central air lift pipe, down a conical spillway to the annulus. Flow continues from the annulus to the charging ports through a series of holes in each charging port. The solution then contacts the charge and continues down the ports to the central air lift. Extensive flow studies have been done on one-eighth, one-quarter, and full-scale models.

Graham, F R



Dissolved organic matter in the Baltic Sea  

NASA Astrophysics Data System (ADS)

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

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



The pH of Enceladus' ocean  

E-print Network

Observational data from the Cassini spacecraft are used to obtain a chemical model of ocean water on Enceladus. The model indicates that Enceladus' ocean is a Na-Cl-CO3 solution with an alkaline pH of ~11-12. The dominance of aqueous NaCl is a feature that Enceladus' ocean shares with terrestrial seawater, but the ubiquity of dissolved Na2CO3 suggests that soda lakes are more analogous to the Enceladus ocean. The high pH implies that the hydroxide ion should be relatively abundant, while divalent metals should be present at low concentrations owing to buffering by clays and carbonates on the ocean floor. The high pH is interpreted to be a key consequence of serpentinization of chondritic rock, as predicted by prior geochemical reaction path models; although degassing of CO2 from the ocean may also play a role depending on the efficiency of mixing processes in the ocean. Serpentinization leads to the generation of H2, a geochemical fuel that can support both abiotic and biological synthesis of organic molecule...

Glein, Christopher; Waite, Hunter



was induced by a controlled titration (0.4 M NaOH, 0.4 M HCl) in a phosphate-based buffer system (0.05 M per liter, pH 8.6, 0.15 M ion  

E-print Network

enables an optical and noninvasive measurement of the pH value and the dissolved oxygen saturation (DO an optical and noninvasive measurement of pH and dissolved oxygen saturation in shake flasks.This technology contains nine independent optical sensors. Optical fibers integrated into the shak- er tray transmit light

Cai, Long



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 also concentrated onto a macroreticular resin and fractionation into three operationally defined fract...


Redox and pH Evolution of the Subseafloor Hydrothermal System at the Main Endeavour Field, JDF: Constraints From Time Series Measurement Using In-Situ Chemical Sensors  

NASA Astrophysics Data System (ADS)

Geochemical studies have long revealed that redox reactions play a critical role in the temporal evolution of hydrothermal systems at mid-ocean ridges. These reactions are best expressed by changes in dissolved H2 and H2S concentrations in the vent fluids, which tend to evolve towards more oxidized conditions from an initially more reducing state, consistent with the mineral assemblage, pyrite-pyrrhotite-magnetite (PPM). It is likely, however, that changes in redox also influence pH owing to constraints imposed by mineral- fluid equilibria. This linkage can be examined by time series analysis of the composition of vent fluids on the Juan de Fuca Ridge in the aftermath of the 1999 seismic event. Accordingly, field investigations with DSV Alvin conducted in 1999 (AT 03-39) shortly after this event together with data obtained in the same area six years later (2005, AT 11-31) have confirmed dramatic changes in vent fluids of Main Endeavour Field. Although vent fluid temperature (~360C) in 2005 decreased only modestly from 1999, significant redox variability was observed as indicated by dissolved H2 and H2S concentrations, which decreased with time from values in excess of 0.7 mm/kg and 20 mm/kg to approximately 0.12-0.18 mm/kg and 7.96-8.90 mm/kg, respectively. Concomitantly, pH, which was measured in-situ with a high temperature pH sensor, decreased from a value around 5 to values a range of 4.43-4.89. Phase equilibria calculations indicate that compositional changes in the vent fluids of the type observed require corresponding changes in coexisting minerals in subseafloor reaction zones. For example, using the measured chemistry of the vent fluids with constraints imposed by plagioclase and epidote solid solutions demonstrate that decreasing temperature and increasing oxidative conditions can result in more acidic fluids. Assuming a subseafloor pressure of 500 bars, these data suggest that redox evolution from PPM at 400C to HM (hematite-magnetite) at 375C results in a pH decrease of approximately 0.3 units. Thus, approximately one third of the pH change is due to redox owing to the effect of redox on the stability epidote solid solution. Therefore, as the MEF system evolves towards more oxidizing conditions, fluid pH tends to decrease. Redox and pH effects on mineral alteration processes in subseafloor reaction zones are highly relevant to the flux of biogeochemical components essential for the origin and evolution of seafloor biologic communities. This research was supported by NSF grants OCE-0117117 and OCE-0525907.

Ding, K.; Seyfied, W. E.; Zhang, Z.; Foustoukos, D.; Pester, N. J.



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



A simple model for predicting the pH values of acidic natural waters  

Microsoft Academic Search

This paper presents a simple computer model for predicting the pH values of acidic natural waters. Effects of various factors (such as, aluminum concentration, dissolved inorganic carbon (DIC), solubility product KSP of A1(OH)3 mineral phase and temperature) on the theoretical prediction of the pH values were discussed. Some valuable conclusions were obtained. This model has been applied to practical analysis

Shuping Bi



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.



Characterizing natural dissolved organic matter in a freshly submerged catchment (Three Gorges Dam, China) using UV absorption, fluorescence spectroscopy and PARAFAC.  


This study applied parallel factor analysis (PARAFAC) to fluorescence excitation-emission matrices (EEMs) of natural water samples in a freshly submerged catchment in the upper reach of Three Gorges Dam (China). Two fluorescent natural dissolved organic matter (NDOM) components (humic/fulvic-like) were uncovered and were positively correlated with selected water quality parameters, i.e. dissolved oxygen concentration, dissolved organic carbon concentration, dissolved Kjeldahl nitrogen concentration and total (dissolved plus particulate) phosphorus concentration, respectively. To other water quality parameters (i.e. total nitrogen, particulate nitrogen, particulate phosphorus, dissolved phosphorus, dissolved nitrate, pH, and chemical oxygen demand), either the two components did not show any correlation or only one component showed correlation. In particular, particulate N correlated significantly to the fulvic acid, but not to the humic acid. Meanwhile, two conventional spectroscopic indices i.e. specific UV absorbance at 254 nm (SUVA254) and fluorescence index (FI) indicated that the whole NDOM in the waters were low in aromaticity and predominantly derived from aquatic microbial processes. Given together, it concludes that N and P did not function equally in the NDOM production, and the two components were not derived from the same microbial processes. The EEMs-PARAFAC has proven to be of potential as an effective tool in investigation of the interlink between NDOM and nutrients which may be utilized as an indicator of water environment. PMID:22339034

Chen, Hao; Zheng, Binghui



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


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

Tam, Y S; Elefsiniotis, P



Earth & Space Science PhDs, Class of 2001.  

ERIC Educational Resources Information Center

This study documents the employment patterns and demographic characteristics of recent PhDs in earth and space science. It summarizes the latest annual survey of recent earth and space science PhDs conducted by the American Geological Institute, the American Geophysical Union, and the Statistical Research Center of the American Institute of

Claudy, Nicholas; Henly, Megan; Migdalski, Chet


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



Formulation of rizatriptan benzoate fast dissolving buccal films by emulsion evaporation technique  

PubMed Central

Aim: The present study deals with the formulation of fast dissolving films of Rizatriptan benzoate that is used for the treatment of Migraine. The concept of fast-dissolving drug delivery emerged from the desire to provide patient with more conventional means of taking their medication. Materials and Methods: In the present research work, various trials were carried out using film forming agents such as maltodextrin, gum karaya and xanthan gum to prepare an ideal film. Emulsion evaporation method was used for the preparation of films. The prepared films were evaluated for weight uniformity, drug content, film thickness, folding endurance, dispersion test and curling. The in vitro dissolution studies were carried out using simulated salivary fluid (pH 6.8 phosphate buffer). Results: About 97% of the drug was found to be released from the film within 10 min that is a desirable character for fast absorption. The drug excipient interaction studies carried out by differential scanning calorimetry analysis and Fourier transform infrared studies revealed that there were no major interactions between the drugs and excipients used for the preparation of films. Conclusion: Fast dissolving films of Rizatriptan benzoate prepared by emulsion evaporation technique were found to be suitable for eliciting better therapeutic effect in the treatment of migraine. PMID:25838995

Vidyadhara, Suryadevara; Sasidhar, Reddyvallam Lankapalli; Balakrishna, Thalamanchi; Vardhan, Malapolu Santha



Removal of actinides from dissolved ORNL MVST sludge using the TRUEX process  

SciTech Connect

Experiments were conducted to evaluate the transuranium extraction process for partitioning actinides from actual dissolved high-level radioactive waste sludge. All tests were performed at ambient temperature. Time and budget constraints permitted only two experimental campaigns. Samples of sludge from Melton Valley Storage Tank W-25 were rinsed with mild caustic (0.2 M NaOH) to reduce the concentrations of nitrates and fission products associated with the interstitial liquid. In one campaign, the rinsed sludge was dissolved in nitric acid to produce a solution containing total metal concentrations of ca. 1.8 M with a nitric acid concentration of ca. 2.9 M. About 50% of the dry mass of the sludge was dissolved. In the other campaign, the sludge was neutralized with nitric acid to destroy the carbonates, then leached with ca. 2.6 M NaOH for ca. 6 h before rinsing with the mild caustic. The sludge was then dissolved in nitric acid to produce a solution containing total metal concentrations of ca. 0.6 M with a nitric acid concentration of ca. 1.7 M. About 80% of the sludge dissolved. The dissolved sludge solution form the first campaign began gelling immediately, and a visible gel layer was observed after 8 days. In the second campaign, the solution became hazy after ca. 8 days, indicating gel formation, but did not display separated gel layers after aging for 20 days. Batch liquid-liquid equilibrium tests of both the extraction and stripping operations were conducted. Chemical analyses of both phases were used to evaluate the process. Evaluation was based on two metrics: the fraction of TRU elements removed from the dissolved sludge and comparison of the results with predictions made with the Generic TRUEX Model (GTM). The fractions of Eu, Pu, Cm, Th, and U species removed from aqueous solution in only one extraction stage were > 95% and were close to the values predicted by the GTM. Mercury was also found to be strongly extracted, with a one-stage removal of > 92%.

Spencer, B.B.; Egan, B.Z.; Chase, C.W.



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



Method for dissolving delta-phase plutonium  


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 and 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)



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

USGS Publications Warehouse

The U.S. Geological Survey, Washington State Department of Ecology, and Puyallup Tribe of Indians conducted a study in August and September 2001 to assess factors affecting concentrations of dissolved oxygen in the lower Puyallup and White Rivers, Washington. The study was initiated because observed concentrations of dissolved oxygen in the lower Puyallup River fell to levels ranging from less than 1 milligram per liter (mg/L) to about 6 mg/L on several occasions in September 2000. The water quality standard for the concentration of dissolved oxygen in the Puyallup River is 8 mg/L.This study concluded that inundation of the sensors with sediment was the most likely cause of the low concentrations of dissolved oxygen observed in September 2000. The conclusion was based on (1) knowledge gained when a dissolved-oxygen sensor became covered with sediment in August 2001, (2) the fact that, with few exceptions, concentrations of dissolved oxygen in the lower Puyallup and White Rivers did not fall below 8 mg/L in August and September 2001, and (3) an analysis of other mechanisms affecting concentrations of dissolved oxygen.The analysis of other mechanisms indicated that they are unlikely to cause steep declines in concentrations of dissolved oxygen like those observed in September 2000. Five-day biochemical oxygen demand ranged from 0.22 to 1.78 mg/L (mean of 0.55 mg/L), and river water takes only about 24 hours to flow through the study reach. Photosynthesis and respiration cause concentrations of dissolved oxygen in the lower Puyallup River to fluctuate as much as about 1 mg/L over a 24-hour period in August and September. Release of water from Lake Tapps for the purpose of hydropower generation often lowered concentrations of dissolved oxygen downstream in the White River by about 1 mg/L. The effect was smaller farther downstream in the Puyallup River at river mile 5.8, but was still observable as a slight decrease in concentrations of dissolved oxygen caused by photosynthesis and respiration. The upper limit on oxygen demand caused by the scour of anoxic bed sediment and subsequent oxidation of reduced iron and manganese is less than 1 mg/L. The actual demand, if any, is probably negligible.In August and September 2001, concentrations of dissolved oxygen in the lower Puyallup River did not fall below the water-quality standard of 8 mg/L, except at high tide when the saline water from Commencement Bay reached the monitor at river mile 2.9. The minimum concentration of dissolved oxygen (7.6 mg/L) observed at river mile 2.9 coincided with the maximum value of specific conductance. Because the dissolved-oxygen standard for marine water is 6.0 mg/L, the standard was not violated at river mile 2.9. The concentration of dissolved oxygen at river mile 1.8 in the White River dropped below the water-quality standard on two occasions in August 2001. The minimum concentration of 7.8 mg/L occurred on August 23, and a concentration of 7.9 mg/L was recorded on August 13. Because there was some uncertainty in the monitoring record for those days, it cannot be stated with certainty that the actual concentration of dissolved oxygen in the river dropped below 8 mg/L. However, at other times when the quality of the monitoring record was good, concentrations as low as 8.2 mg/L were observed at river mile 1.8 in the White River.

Ebbert, J.C.



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.



Study of dissolved chlorofluorocarbons in Lake Washington  

NASA Astrophysics Data System (ADS)

Measurements of three chlorofluorocarbons (CFCs): trichlorofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12) and trichlorotrifluoroethane (CFC-113), along with methyl chloroform (CH3CCl3) and carbon tetrachloride (CCl4) were made in water samples from Lake Washington, using Electron Capture-Gas Chromatography (EC-GC). The samples were collected in mid-autumn, a period when the lake's upper layer undergoes rapid cooling. At the time of sampling, a strong vertical temperature gradient was present in the lake, with surface temperatures of 14C, and near bottom (50 meters) temperatures of 8C. The concentrations of dissolved CFC-12 and CFC-11 increased with depth, as expected from the higher solubilities of these gases at lower temperatures. Atmospheric measurements made at the sampling site at the time of the cruise, showed that CFC-11 and CFC-12 saturations in the near surface samples were 100 % and 106 %, respectively. For the deepest sample (52 meters) CFC-11 and CFC-12 saturations were 102 % and 126 %. Because the surface layer of the lake responds to changes in atmospheric CFCs on a time scale of several weeks, the higher than equilibrium concentrations of CFC-12 observed at the time of sampling may reflect earlier episodes of elevated levels of atmospheric CFC-12 in this urban area. High concentrations of dissolved CFCs in runoff or industrial effluent might also lead to elevated CFC levels in the lake. The cold, deep water of Lake Washington is relatively isolated from the effects of surface gas exchange except during winter, and the supersaturations observed in the deep layer may reflect periods of elevated atmospheric CFC-12 levels from the previous winter season. These results were compared to summertime profiles of CFC-11 and CFC-12 made in 1994.

Han, Lijun; Bullister, John L.; Wisegarver, David P.



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 radioactive elements under possible repository conditions, based on geochemical modeling calculations using geochemical modeling tools, thermodynamic databases, and measurements made in laboratory experiments and field work. The scope of this modeling activity is to predict dissolved concentrations or solubility limits for 14 radioactive elements (actinium, americium, carbon, cesium, iodine, lead, neptunium, plutonium, protactinium, radium, strontium, technetium, thorium, and uranium), which are important to calculated dose. Model outputs are mainly in the form of look-up tables plus one or more uncertainty terms. The rest are either in the form of distributions or single values. The results of this analysis are fundamental inputs for total system performance assessment to constrain the release of these elements from waste packages and the engineered barrier system. Solubilities of plutonium, neptunium, uranium, americium, actinium, thorium, protactinium, lead, and radium have been re-evaluated using the newly updated thermodynamic database (Data0.ymp.R2). For all of the actinides, identical modeling approaches and consistent environmental conditions were used to develop solubility models in this revision. 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, activity coefficients, and selection of solubility controlling phase have been quantified or otherwise addressed. Moreover, a new blended plutonium solubility model has been developed in this revision, which gives a mean solubility that is three orders of magnitude lower than the plutonium solubility model used for the Total System Performance Assessment for the Site Recommendation. Two alternative neptunium solubility models have also been developed in this revision. The base-case models have been validated to the level of confidence required by their relative importance to the potential performance of the repository system. The plutonium and neptunium solubility models have been validated to a higher level of confidence than the rest.

Y. Chen; E.R. Thomas; F.J. Pearson; P.L. Cloke; T.L. Steinborn; P.V. Brady



Centrifugo-pneumatic valving utilizing dissolvable films.  


In this article we introduce a novel technology that utilizes specialized water dissolvable thin films for valving in centrifugal microfluidic systems. In previous work (William Meathrel and Cathy Moritz, IVD Technologies, 2007), dissolvable films (DFs) have been assembled in laminar flow devices to form efficient sacrificial valves where DFs simply open by direct contact with liquid. Here, we build on the original DF valving scheme to leverage sophisticated, merely rotationally actuated vapour barriers and flow control for enabling comprehensive assay integration with low-complexity instrumentation on "lab-on-a-disc" platforms. The advanced sacrificial valving function is achieved by creating an inverted gas-liquid stack upstream of the DF during priming of the system. At low rotational speeds, a pocket of trapped air prevents a surface-tension stabilized liquid plug from wetting the DF membrane. However, high-speed rotation disrupts the metastable gas/liquid interface to wet the DF and thus opens the valve. By judicious choice of the radial position and geometry of the valve, the burst frequency can be tuned over a wide range of rotational speeds nearly 10 times greater than those attained by common capillary burst valves based on hydrophobic constrictions. The broad range of reproducible burst frequencies of the DF valves bears the potential for full integration and automation of comprehensive, multi-step biochemical assay protocols. In this report we demonstrate DF valving, discuss the biocompatibility of using the films, and show a potential sequential valving system including the on-demand release of on-board stored liquid reagents, fast centrifugal sedimentation and vigorous mixing; thus providing a viable basis for use in lab-on-a-disc platforms for point-of-care diagnostics and other life science applications. PMID:22692574

Gorkin, Robert; Nwankire, Charles E; Gaughran, Jennifer; Zhang, Xin; Donohoe, Gerard G; Rook, Martha; O'Kennedy, Richard; Ducre, Jens



Automated dispersive solid-phase extraction using dissolvable Fe3O4-layered double hydroxide core-shell microspheres as sorbent.  


Automation of dispersive solid-phase extraction (d-SPE) presents significant challenges. Separation of the sorbent from the spent sample cannot be conducted without manual operations, including centrifugation, a widely used means of isolating a solid material from solution. In this work, we report an approach to d-SPE using dissolvable magnetic Fe3O4-layered double hydroxide core-shell microspheres as sorbent to enable automation of the integrative extraction and analytical processes. Through magnetic force, the sorbent, after extraction, was isolated from the sample and then dissolved by acid to release the analytes. Thus the customary analyte elution step in conventional SPE was unnecessary. The automated d-SPE step was coupled to high-performance liquid chromatography (HPLC) with photodiode array detection for determination of several pharmaceuticals and personal care products (PPCPs) [acetylsalicylic acid (ASA), 2,5-dihydroxybenzoic acid (DBA), 2-phenylphenol (PP), and fenoprofen (FP)] in aqueous samples. For the automated d-SPE process, experimental parameters such as agitation speed, temperature, time, and pH were optimized. The results showed that this method provided low limits of detection (between 0.021 and 0.042 ?g/L), good linearity (r(2) ? 0.9956), and good repeatability of extractions (relative standard deviations ?4.1%, n = 6). The optimized procedure was then applied to determination of PPCPs in a sewage sample and ASA and FP in drug preparations. This fully automated extraction-HPLC approach was demonstrated to be an efficient procedure for extraction and analysis of ASA, DBA, PP, and FP in these samples. PMID:25320871

Tang, Sheng; Chia, Guo Hui; Chang, Yuepeng; Lee, Hian Kee



Dissolution of Mercury from Dental Amalgam at Different pH Values  

Microsoft Academic Search

Dissolution of mercury from dental amalgam has been shown to be diminished by the formation of a tin oxide film on the surface of the mercury-rich ? 1 phase (Marek, 1990b). Since tin oxides dissolve at low pH values (Deltombe et al., 1974), acidic conditions in the oral cavity may cause an increase in the mercury release. The purpose of

M. Marek



1. Constituents of rainwater 2. pH and pKa  

E-print Network

Acid Rain Outline: 1. Constituents of rainwater 2. pH and pKa 3. Sources of acid rain 4. Adverse e#11;ects of acid rain 5. Controls 1: Constituents of rainwater #15; Gases are soluble in water: Henry. Strong acids formed upon dissolving: H 2 SO 4 and H 2 SO 3 . #12; Chemistry of Acid Rain #15; NO 2

Schofield, Jeremy


Thorium speciation in seawater P.H. Santschi a,*, J.W. Murray b  

E-print Network

Thorium speciation in seawater P.H. Santschi a,*, J.W. Murray b , M. Baskaran c , C.R. Benitez October 2005 Available online 7 February 2006 Abstract Since the 1960s, thorium isotopes occupy a special of these applications are possible with little knowledge of the dissolved chemical properties of thorium, other than its

Murray, James W.


Spectral studies of pH dye films for detection of toxic chemicals  

NASA Astrophysics Data System (ADS)

The molecular absorption spectra of pH dyes, employed for ammonia sensing are investigated. Differences of absorption spectra of Bromothymol Blue and Bromocresol Purple dyes, dissolved in water and entrapped in Polymethylphenylsiloxane film are discussed. Correspondence of dye-films absorption bands shape to the Gauss distribution shape in the spectral region of light source emission band was determined.

Wojcik, Wieslaw; Potyrailo, Radislav A.; Golubkov, Sergei P.; Borsuk, Pavel S.



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

Microsoft Academic Search

Photosynthesis is the primary carbon fixation process in thermal waters below 70C, 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

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




EPA Science Inventory

A year-long experiment, using reconstructed spodosol and intact alfisol soil columns, was conducted to examine the effects of various simulated throughfall solutions on soil C dynamics. oil organic C solubilization, dissolved organic C fractions, and decomposition rates were stud...


Effect of Elicitation and Changes in Extracellular pH on the Cytoplasmic and Vacuolar pH of Suspension-Cultured Soybean Cells 1  

PubMed Central

We have employed both 31P nuclear magnetic resonance spectroscopy and two intracellular fluorescent pH indicator dyes to monitor the pH of the vacuole and cytoplasm of suspension-cultured soybean cells (Glycine max Merr cv Kent). For the 31P nuclear magnetic resonance studies, a flow cell was constructed that allowed perfusion of the cells in oxygenated growth medium throughout the experiment. When the perfusion medium was transiently adjusted to a pH higher than that of the ambient growth medium, a rapid elevation of vacuolar pH was observed followed by a slow (approximately 30 minute) return to near resting pH. In contrast, the concurrent pH changes in the cytoplasm were usually fourfold smaller. These data indicate that extracellular pH changes are rapidly communicated to the vacuole in soybean cells without significantly perturbing cytoplasmic pH. When elicitors were dissolved in a medium of altered pH and introduced into the cell suspension, the pH of the vacuole, as above, quickly reflected the pH of the added elicitor solution. In contrast, when the pH of either a polygalacturonic acid or Verticillium dahliae elicitor preparation was adjusted to the same pH as the ambient medium, no significant change in either vacuolar or cytoplasmic pH was observed during the 35 minute experiment. These results were confirmed in experiments with pH-sensitive fluorescent dyes. We conclude that suspension-cultured soybean cells do not respond to elicitation by significantly changing the pH of their vacuolar or cytoplasmic compartments. ImagesFigure 1 PMID:16668695

Horn, Mark A.; Meadows, Robert P.; Apostol, Izydor; Jones, Claude R.; Gorenstein, David G.; Heinstein, Peter F.; Low, Philip S.



Photolytic processing of secondary organic aerosols dissolved in cloud droplets  

SciTech Connect

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 hours. 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 reduced by photolysis relative to the monomeric compounds. Direct pH measurements showed that compounds containing carboxylic acids increased upon photolysis. Methanol reactivity analysis revealed significant photodissociation of molecules containing carbonyl groups and formation of carboxylic acids. Aldehydes, such as limononaldehyde, were almost completely removed. The removal of carbonylswas 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 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.

Bateman, Adam P.; Nizkorodov, Serguei; Laskin, Julia; Laskin, Alexander



Complexation with dissolved organic matter and solubility control of heavy metals in a sandy soil.  


The complexation of heavy metals with dissolved organic matter (DOM) in the environment influences the solubility and mobility of these metals. In this paper, we measured the complexation of Cu, Cd, Zn, Ni, and Pb with DOM in the soil solution at pH 3.7-6.1 using a Donnan membrane technique. The results show that the DOM-complexed species is generally more significant for Cu and Pb than for Cd, Zn, and Ni. The ability of two advanced models for ion binding to humic substances, e.g., model VI and NICA-Donnan, in the simulation of metal binding to natural DOM was assessed by comparing the model predictions with the measurements. Using the default parameters of fulvic and humic acid, the predicted concentrations of free metal ions from the solution speciation calculation using the two models are mostly within 1 order of magnitude difference from the measured concentrations, except for Ni and Pb in a few samples. Furthermore, the solid-solution partitioning of the metals was simulated using a multisurface model, in which metal binding to soil organic matter, dissolved organic matter, clay, and iron hydroxides was accounted for using adsorption and cation exchange models (NICA-Donnan, Donnan, DDL, CD-MUSIC). The model estimation of the dissolved concentration of the metals is mostly within 1 order of magnitude difference from those measured except for Ni in some samples and Pb. The solubility of the metals depends mainly on the metal loading over soil sorbents, pH, and the concentration of inorganic ligands and DOM in the soil solution. PMID:12487303

Weng, Liping; Temminghoff, Erwin J M; Lofts, Stephen; Tipping, Edward; Van Riemsdijk, Willem H



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.



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.



Formation of haloacetic acids from dissolved organic matter fractions during chloramination.  


The objective of this study was to investigate the roles of dissolved organic matter (DOM) fractions, pH and bromide concentration in the formation of haloacetic acids (HAA) during chloramination. DOM from two surface waters with a low (2.9 L/mg-m) and high (5.1 L/mg-m) specific UV absorbance (SUVA(254)) values was isolated and fractionated into three fractions based on the hydrophobicity [i.e., hydrophobic (HPO), transphilic (TPH) and hydrophilic (HPI)]. DOM mass balances and DBP reactivity checks were performed to characterize the effects of isolation and fractionation steps. The fractions were chloraminated at three pHs and three bromide concentrations. The results showed that pH was the most important factor controlling HAA formation and speciation. The HAA yields significantly decreased with increase in pH from 6.3 to 9.0. The impact of bromide in the formation of brominated HAA species also became less important with increasing pH, and no brominated specie was detectable at pH 9. HPO fractions of the two source waters consistently showed higher HAA yields than TPH and HPI fractions. On the other hand, HPI fractions showed higher bromine incorporation than HPO and TPH fractions. To maintain higher and relatively stable combined chlorine residuals while reducing HAA formation, water utilities may consider keeping pH above 7.5 as one strategy. This will also lower the formation of brominated HAA species which have been shown to be more cyto- and geno-toxic than their chlorinated analogs. PMID:23245540

Hong, Ying; Song, Hocheol; Karanfil, Tanju



Dissolved organic carbon reduces the toxicity of aluminum to three tropical freshwater organisms.  


The influence of dissolved organic carbon (DOC) on the toxicity of aluminum (Al) at pH 5 (relevant to acid mine drainage conditions), to the tropical green hydra (Hydra viridissima), green alga (Chlorella sp.), and cladoceran (Moinodaphnia macleayi) was assessed. Two DOC sources, a natural in situ DOC in soft billabong water (SBW) and Suwannee River fulvic acid (SRFA) standard, were compared. The order of sensitivity of the test organisms to dissolved Al (0.1 m fraction) was Hydra viridissima > Moinodaphnia macleayi > Chlorella sp. with DOC reducing dissolved Al toxicity most for Hydra viridissima. However, colloidal or precipitated Al may contribute indirectly to the toxicity for M. macleayi and Chlorella sp. The toxicity of dissolved Al was up to six times lower in test waters containing 10 mg L(-1) DOC (in the form of SRFA), relative to toxicity observed at 1 mg L(-1) DOC. In contrast, the toxicity of Al was up to two times lower in SBW containing 10 mg L(-1) DOC, relative to water containing 1 mg L(-1) DOC. The increased ability of SRFA in reducing Al toxicity was linked to its greater affinity for complexing Al compared with the in situ DOC. This has important implications for studies that use commercial standards of humic substances to predict Al toxicity in local environments. Speciation modeling demonstrated that Al(3+) and AlOH(2+) provided a strong relationship with toxicity. An empirical relationship is provided for each organism that can be used to predict Al toxicity at a given Al and DOC concentration. PMID:22105345

Trenfield, Melanie A; Markich, Scott J; Ng, Jack C; Noller, Barry; van Dam, Rick A



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.



Fabrication and characterization of conducting polyvinyl alcohol nanofibers  

Microsoft Academic Search

Conducting polyvinyl alcohol (PVA) nanofibers with diameters ranging from 100nm to 300nm were fabricated by an electrospinning method from spinning dopes of the dissolved PVA polymer in aqueous dispersion of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS). Using a chemical cross-linking agent, glutaraldehyde (GA), water insoluble conducting PVA nanofibers were obtained through an in-situ crosslinking of PVA polymer during electrospinning. The cross-linked conducting nanofibers

Daehwan Cho; Nikolas Hoepker; Margaret W. Frey


The pH Game  

NSDL National Science Digital Library

This learning activity engages students in measurement of pH in water and soil samples, plants and other natural materials. By mixing different substances, they observe how pH changes, and become familiar with the pH of common household products. Through discussion, they learn how pH can be modified in the environment.


pH Scale  

NSDL National Science Digital Library

In this online interactive simulation, learners will test the pH of liquids like coffee, spit, and soap to determine whether each is acidic, basic, or neutral. Learners will visualize the relative number of hydroxide ions and hydronium ions in a solution, and they can switch between logarithmic and linear scales. Learners will also investigate whether changing the volume or diluting with water affects the pH. They can experiment by designing their own liquids! This activity includes an online simulation, sample learning goals, a teacher's guide, and translations in over 30 languages.

Wendy Adams



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.



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 Brosus; John Cigana; Benoit Barbeau; Catherine Daines-Martinez; Herv Suty



Dissolved Oxygen in Guadalupe Slough and Pond A3W, South San Francisco Bay, California, August and September 2007  

USGS Publications Warehouse

Initial restoration of former salt evaporation ponds under the South Bay Salt Pond Restoration Project in San Francisco Bay included the changing of water-flow patterns and the monitoring of water quality of discharge waters from the ponds. Low dissolved oxygen (DO) concentrations became evident in discharge waters when the ponds first were opened in 2004. This was a concern, because of the potential for low-DO pond discharge to decrease the DO concentrations in the sloughs that receive water from the ponds. However, as of summer 2007, only limited point-measurements of DO concentrations had been made in the receiving sloughs adjacent to the discharge ponds. In this report, we describe two short studies aimed at understanding the natural variability of slough DO and the effect of pond discharge on the DO concentrations in the sloughs. Pond A3W (a discharge pond) and the adjacent Guadalupe Slough were instrumented in August and September 2007 to measure DO, temperature, conductivity, and pH. In addition, Mowry and Newark Sloughs were instrumented during the August study to document DO variability in nearby sloughs that were unaffected by pond discharge. The results showed that natural tidal variability in the slough appeared to dominate and control the slough DO concentrations. Water-quality parameters between Guadalupe Slough and Mowry and Newark Sloughs could not be directly compared because deployment locations were different distances from the bay. Pond-discharge water was identified in Guadalupe Slough using the deployed instruments, but, counter to the previous assumption, the pond discharge, at times, increased DO concentrations in the slough. The effects of altering the volume of pond discharge were overwhelmed by natural spring-neap tidal variability in the slough. This work represents a preliminary investigation by the U.S. Geological Survey of the effects of pond discharge on adjacent sloughs, and the results will be used in designing a comprehensive DO study to determine normal variability for this region.

Shellenbarger, Gregory G.; Schoellhamer, David H.; Morgan, Tara L.; Takekawa, John Y.; Athearn, Nicole D.; Henderson, Kathleen D.



A multi-scale comparison of dissolved Al, Fe and S in a boreal acid sulphate soil.  


Acid sulphate (AS) soils are most prevalent in the tropics, but the acidic discharge from cultivated AS soils also threatens water bodies under boreal conditions. Feasible options to reduce the acid load are needed. In this study, the groundwater of an AS field was monitored for 3.5 years, and the efficiency of waterlogging in mitigating the environmental risks caused by acidic discharge was investigated in a 2.5-year experiment with 10 monolithic lysimeters taken from the same field. In order to unravel the transferability of the results from lysimeters to the field scale, the Al, Fe and S concentrations in discharge water from the lysimeters were compared with those in the groundwater of the AS field (pedon and field scale), and in pore water (pedon and horizon scale). In the waterlogged bare lysimeters (HWB), the Al, Fe and S concentrations in discharge waters were broadly similar to those measured in the groundwater and followed the changes in the pore water. In the waterlogged cropped (reed canary grass, Phalaris arundinacea) lysimeters (HWC), in contrast, the discharge waters were markedly higher in Fe and lower in Al than the groundwater in the field. This outcome was attributable to the reduction of Fe(3+) to the more soluble Fe(2+) and the reduction-induced increase in pH, which enhanced the formation of Al(3+) hydroxy species. Lowering of the water table (LWC) caused soil ripening, which resulted in increased saturated hydraulic conductivity and porosity and enhanced the oxidation of sulphidic materials and acid formation. The responses of Al, Fe and S in drainage waters from HWC and LWC lysimeters resembled previous findings in AS soils. Based on this and the similarity between dissolved element concentrations in the discharge water of HWB lysimeters and groundwater in the field, we conclude that our monolithic lysimeters yielded realistic results concerning the efficiency of various methods in mitigating environmental risks related to cultivated AS soils. PMID:25203826

Virtanen, Seija; Simojoki, Asko; Rita, Hannu; Toivonen, Janne; Hartikainen, Helin; Yli-Halla, Markku



Free Zinc Ion and Dissolved Orthophosphate Effects on  

E-print Network

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


Transport of dissolved oxygen through silicone rubber membrane  

Microsoft Academic Search

The transport of dissolved oxygen in water through a silicone rubber membrane was studied theoretically and experimentally. The apparent oxygen permeability coefficients of silicone rubber were measured at various membrane thicknesses, temperatures, and concentration levels. The permeation flux was measured under both steady-and unsteady-state conditions. For the first time, the thickness effect of dissolved gas permeation has been studied. It

Sun-Tak Hwang; Thomas E. S. Tang; Karl Kammermeyer



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




Dissolved silver in European estuarine and coastal waters  

Microsoft Academic Search

Silver is one of the most toxic elements for the marine microbial and invertebrate community. However, little is known about the distribution and behaviour of dissolved silver in marine systems. This paper reports data on dissolved and sediment-associated silver in European estuaries and coastal waters which have been impacted to different extents by past and present anthropogenic inputs. This is

Alan D. Tappin; Jose L. Barriada; Charlotte B. Braungardt; E. Hywel Evans; Matthew D. Patey; Eric P. Achterberg



Constraining oceanic dust deposition using surface ocean dissolved Al  

E-print Network

Constraining oceanic dust deposition using surface ocean dissolved Al Qin Han,1 J. Keith Moore,1; accepted 7 December 2007; published 12 April 2008. [1] We use measurements of ocean surface dissolved Al (DEAD) model to constrain dust deposition to the oceans. Our Al database contains all available

Zender, Charles


Interactions of Arsenic and the Dissolved Substances Derived from  

E-print Network

Interactions of Arsenic and the Dissolved Substances Derived from Turf Soils Z H A N G R O N G C H for the control of weeds in turf grasses at golf courses in Florida. There are concerns about arsenic (As for arsenic species (arsenite, AsIII and arsenate, AsV), dissolved organic matter, and additional constituents

Florida, University of


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



What controls dissolved iron concentrations in the world ocean?  

Microsoft Academic Search

Dissolved (< 0.4 ?m) iron has been measured in 354 samples at 30 stations in the North and South Pacific, Southern Ocean and North Atlantic by the Trace Metals Laboratory at Moss Landing Marine Laboratories. These stations are all more than 50 km from a continental margin. The global distribution of dissolved iron, which is derived from these profiles, is

Kenneth S. Johnson; R. Michael Gordon; Kenneth H. Coale



Dissolved P in streams in dry years and wet years  

Technology Transfer Automated Retrieval System (TEKTRAN)

Dissolved phosphorus (P) has often been identified as the nutrient of concern in lakes, reservoirs, and streams especially where there is evidence of eutrophication. We analyzed contiguous-spatial and temporal variability of dissolved P [soluble reactive P (SRP)] stream concentrations during times ...


Influence of Ca, humic acid and pH on lead accumulation and toxicity in the fathead minnow during prolonged water-borne lead exposure  

E-print Network

of these processes, surface waters may contain elevated Pb concentrations, especially in industrialized areas (World The present study examines the influence of Ca2+ as (CaSO4), dissolved organic carbon (DOC) and pH on chronic; Calcium; DOM; pH; Pimephales promelas 1. Introduction Lead (Pb) is not required for normal physiology

Grosell, Martin



PubMed Central

Background Dissolvable tobacco products (DTPs) have been introduced into test markets in the U.S. We sought to gauge level of interest in trying these products and correlates of interest among potential consumers. Methods A web-based survey of freshman at 11 universities in North Carolina (NC) and Virginia (VA) was conducted in fall 2010. Multivariable logistic regression analyses were used to identify correlates of students likelihood to try DTPs. Results Weighted prevalence of likelihood to try DTPs was 3.7%. Significant correlates of likelihood to try included male gender, current cigarette smoking, current snus use, sensation seeking, lifetime illicit drug use, and perceived health risk of using DTPs. Among current smokers, current snus use, current use of chewing tobacco, and considering quitting smoking were associated with likelihood to try DTPs. Conclusions While overall interest in trying these products was low, current users of cigarettes and snus were much more likely than others in trying a free sample. Some current smokers may consider DTPs to be an aid to smoking cessation, although the population-level impact of introducing these products is unknown. PMID:24309296

Wolfson, Mark; Pockey, Jessica R.; Reboussin, Beth A.; Sutfin, Erin L.; Egan, Kathleen L.; Wagoner, Kimberly G.; Spangler, John G.



Urothelial injury to the rabbit bladder from various alkaline and acidic solutions used to dissolve kidney stones.  


Different irrigating solutions are used clinically to dissolve uric acid, cystine and struvite stones. These studies were undertaken to assess the toxicity to the rabbit bladder epithelium of several commonly used formulations. Test solutions were infused antegrade through a left ureterotomy overnight. Bladders were removed and routine histological sections made. A pH 7.6 solution of NaHCO3 appeared harmless. The same solution with two per cent acetylcysteine produced slight injury. All pH 4 solutions caused significant damage to the urothelium. Hemiacidrin, which contains magnesium, produced less damage than did other pH 4 solutions without that cation. Our data tend to support Suby's conclusions that addition of magnesium reduces urothelial injury even though the presence of magnesium will slow dissolution of struvite. PMID:3712608

Reckler, J; Rodman, J S; Jacobs, D; Rotterdam, H; Marion, D; Vaughan, E D



Dissolved gas quantification and bubble formation in liquid chemical dispense  

NASA Astrophysics Data System (ADS)

Gas dissolved in liquids such as photoresist comes out of solution as bubbles after the liquid experiences a pressure drop in a dispense train and may cause on-wafer defects. Reservoirs in the dispense train can assist in removing bubbles but are incapable of effectively removing dissolved gas. This study demonstrates the importance of maintaining the amount of dissolved gas in a liquid below a critical value to reduce bubbles generated after a pressure drop in the dispense train occurs. The methodology used to quantify dissolved gas during liquid dispense cycle using gas chromatography is discussed. The amount of dissolved gas is correlated to the amount of bubbles downstream of a pressure drop. This study also analyzes sources of bubbles in the dispense train and techniques to mediate the sources.

Tom, Glenn; Liu, Wei



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.



Production and characterization of rapidly dissolving cryopellets.  


The procedure described in this study provides a platform technology for rapidly dissolving, single-dosed cryopellets. The different steps during cryopellet production were investigated, covering droplet generation, droplet freezing in liquid nitrogen (LN2 ) as well as cryopellet properties. With the setup developed, uniform droplets between 4 and 14 ?L were produced. The freezing behavior was similar to approaches reported in the literature. A weight loss reported for droplets frozen in LN2 could not be confirmed. Mechanical stability as observed with texture analysis as well as dissolution time increased with increasing solid content. All cryopellets immediately disintegrated when in contact with the dissolution medium. The dissolution times of amorphous sucrose and trehalose-based cryopellets at different solid content levels were comparable. Crystalline mannitol cryopellets showed in general a higher dissolution time. The formation of ?-mannitol potentially makes the cryopellets suitable as an intermediate product for tableting. 2015 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 104:1668-1676, 2015. PMID:25631983

Erber, Matthias; Lee, Geoffrey



Dissolved silica budget for the Baltic Sea  

NASA Astrophysics Data System (ADS)

A budget model covering the Baltic Sea was developed for the time period 1980-2000 to estimate water and dissolved silica (DSi) fluxes as well as internal DSi sinks/sources. The Baltic Sea was resolved by eight basins, where the largest basin the Baltic Proper was divided laterally into north/west and southern/east parts as well as vertically to take into account the existence of the permanent halocline. The basins demonstrated rather different patterns with regard to silica cycling. The Gulfs of Finland and Riga together with the northernmost basins, Bothnian Bay and Bothnian Sea, are distinguished by substantial specific rates of silica removal accounting for 1.6-4.9 g Si m - 2 yr - 1 . Bearing in mind the large total primary production, the basins comprising the Baltic Proper with the specific removal rates 0.2 and 1.2 g Si m - 2 yr - 1 , do not appear as regions with a high silica accumulation. The Arkona and the Kattegat mainly behave as regions of rapid through-flows. These results point out the northernmost Gulf of Bothnia, the Gulfs of Riga and Finland as areas with a larger share of biogenic silica accumulation than in the Baltic Proper. It is attributed to hydrographic and hydrochemical features. An estimate of diatom export production was made for the Baltic Proper showing that the diatom contribution accounts for 19-44% of the net export production.

Papush, L.; Danielsson, .; Rahm, L.



Methanex, Hoechst Celanese dissolve methanol partnership  

SciTech Connect

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

Morris, G.D.L.



pH optrode  


A process is provided for forming a long-lasting, stable, pH-sensitive dye-acrylamide copolymer useful as a pH-sensitive material for use in an optrode or other device sensitive to pH. An optrode may be made by mechanically attaching the copolymer to a sensing device such as an optical fiber.

Northrup, M. Allen (Berkeley, CA); Langry, Kevin C. (Tracy, CA)



pH Basics  

ERIC Educational Resources Information Center

The exposition of the pervasive concept of pH, of its foundations and implementation as a meaningful quantitative measurement, in nonspecialist university texts is often not easy to follow because too many of its theoretical and operative underpinnings are neglected. To help the inquiring student we provide a concise introduction to the depth just

Lunelli, Bruno; Scagnolari, Francesco



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 0100 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 2246% for glucose and 1777% 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. PMID:23209742

Jagadamma, Sindhu; Mayes, Melanie A.; Phillips, Jana R.



Distribution of dissolved pesticides and other water quality constituents in small streams, and their relation to land use, in the Willamette River Basin, Oregon, 1996  

USGS Publications Warehouse

Water quality samples were collected at sites in 16 randomly selected agricultural and 4 urban subbasins as part of Phase III of the Willamette River Basin Water Quality Study in Oregon during 1996. Ninety-five samples were collected and analyzed for suspended sediment, conventional constituents (temperature, dissolved oxygen, pH, specific conductance, nutrients, biochemical oxygen demand, and bacteria) and a suite of 86 dissolved pesticides. The data were collected to characterize the distribution of dissolved pesticide concentrations in small streams (drainage areas 2.6? 13 square miles) throughout the basin, to document exceedances of water quality standards and guidelines, and to identify the relative importance of several upstream land use categories (urban, agricultural, percent agricultural land, percent of land in grass seed crops, crop diversity) and seasonality in affecting these distributions. A total of 36 pesticides (29 herbicides and 7 insecticides) were detected basinwide. The five most frequently detected compounds were the herbicides atrazine (99% of samples), desethylatrazine (93%), simazine (85%), metolachlor (85%), and diuron (73%). Fifteen compounds were detected in 12?35% of samples, and 16 compounds were detected in 1?9% of samples. Water quality standards or criteria were exceeded more frequently for conventional constituents than for pesticides. State of Oregon water quality standards were exceeded at all but one site for the indicator bacteria E. coli, 3 sites for nitrate, 10 sites for water temperature, 4 sites for dissolved oxygen, and 1 site for pH. Pesticide concentrations, which were usually less than 1 part per billion, exceeded State of Oregon or U.S. Environmental Protection Agency aquatic life toxicity criteria only for chlorpyrifos, in three samples from one site; such criteria have been established for only two other detected pesticides. However, a large number of unusually high concentrations (1?90 parts per billion) were detected, indicating that pesticides in the runoff sampled in these small streams were more highly concentrated than in the larger streams sampled in previous studies. These pulses could have had short term toxicological implications for the affected streams; however, additional toxicological assessment of the detected pesticides was limited because of a lack of available information on the response of aquatic life to the observed pesticide concentrations. Six pesticides, including atrazine, diuron, and metolachlor, had significantly higher (p<0.08 for metolachlor, p<0.05 for the other five) median concentrations at agricultural sites than at urban sites. Five other compounds ?carbaryl, diazinon, dichlobenil, prometon, and tebuthiuron?had significantly higher (p<0.05) concentrations at the urban sites than at the agricultural sites. Atrazine, metolachlor, and diuron also had significantly higher median concentrations at southern agricultural sites (dominated by grass seed crops) than northern agricultural sites. Other compounds that had higher median concentrations in the south included 2,4-D and metribuzin, which are both used on grass seed crops, and triclopyr, bromacil, and pronamide. A cluster analysis of the data grouped sites according to their pesticide detections in a manner that was almost identical to a grouping made solely on the basis of their upstream land use patterns (urban, agricultural, crop diversity, percentage of basin in agricultural production). In this way inferences about pesticide associations with different land uses could be drawn, illustrating the strength of these broad land use categories in determining the types of pesticides that can be expected to occur. Among the associations observed were pesticides that occurred at a group of agricultural sites, but which have primarily noncropland uses such as vegetation control along rights-of-way. Also, the amount of forested land in a basin was negatively associated with pesticide occurrence, sugges

Anderson, Chauncey W.; Wood, Tamara M.; Morace, Jennifer L.



Assessment of temporal patterns in dissolved organic carbon in Tempe Town Lake Monica M. Palta1 and Hilairy E.Hartnett1,2  

E-print Network

criteria; data from NWS and the Maricopa County Flood Control District Monsoon characteristics Summary and flood control for the city of Phoenix · Sources of water to the lake are CAP (Colorado River) water Discharge(CFS) 101 102 103 104 105 Conductivity(S) 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Dissolved

Hall, Sharon J.


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

Technology Transfer Automated Retrieval System (TEKTRAN)

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


Electrostatic Spraying With Conductive Liquids  

NASA Technical Reports Server (NTRS)

Thin, uniform polymer coatings applied in water base normally impossible to charge. Electrostatic sprayer modified so applies coatings suspended or dissolved in electrically conductive liquids. Nozzle and gun constructed of nonconductive molded plastic. Liquid passageway made long enough electrical leakage through it low. Coaxial hose for liquid built of polytetrafluoroethylene tube, insulating sleeve, and polyurethane jacket. Sprayer provided with insulated seal at gun-to-hose connection, nonconductive airhose, pressure tank electrically isolated from ground, and special nozzle electrode. Supply of atomizing air reduced so particle momentum controlled by electrostatic field more effectively. Developed to apply water-base polyurethane coating to woven, shaped polyester fabric. Coating provides pressure seal for fabric, which is part of spacesuit. Also useful for applying waterproof, decorative, or protective coatings to fabrics for use on Earth.

Kosmo, Joseph J.; Dawn, Frederic S.; Erlandson, Robert E.; Atkins, Loren E.



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. PMID:3355143

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



Influence of dissolved hydrogen on the fatigue crack growth behaviour of AISI 4140 steel  

NASA Astrophysics Data System (ADS)

Many metallic structural components come into contact with hydrogen during manufacturing processes or forming operations such as hot stamping of auto body frames and while in service. This interaction of metallic parts with hydrogen can occur due to various reasons such as water molecule dissociation during plating operations, interaction with atmospheric hydrogen due to the moisture present in air during stamping operations or due to prevailing conditions in service (e.g.: acidic or marine environments). Hydrogen, being much smaller in size compared to other metallic elements such as Iron in steels, can enter the material and become dissolved in the matrix. It can lodge itself in interstitials locations of the metal atoms, at vacancies or dislocations in the metallic matrix or at grain boundaries or inclusions (impurities) in the alloy. This dissolved hydrogen can affect the functional life of these structural components leading to catastrophic failures in mission critical applications resulting in loss of lives and structural component. Therefore, it is very important to understand the influence of the dissolved hydrogen on the failure of these structural materials due to cyclic loading (fatigue). For the next generation of hydrogen based fuel cell vehicles and energy systems, it is very crucial to develop structural materials for hydrogen storage and containment which are highly resistant to hydrogen embrittlement. These materials should also be able to provide good long term life in cyclic loading, without undergoing degradation, even when exposed to hydrogen rich environments for extended periods of time. The primary focus of this investigation was to examine the influence of dissolved hydrogen on the fatigue crack growth behaviour of a commercially available high strength medium carbon low alloy (AISI 4140) steel. The secondary objective was to examine the influence of microstructure on the fatigue crack growth behaviour of this material and to determine the hydrogen induced failure mechanism in this material during cyclic loading. The secondary objective of this investigation was to determine the role of inclusions and their influence in affecting the fatigue crack growth rate of this material. Compact tension and tensile specimens were prepared as per ASTM E-647, E-399 and E-8 standards. The specimens were tested in three different heat treated conditions i.e. annealed (as received) as well as two austempered conditions. These specimens were precharged with hydrogen (ex situ) using cathodic charging method at a constant current density at three different time periods ranging from 150 to 250 hours before conducting fatigue crack growth tests. Mode 1 type fatigue tests were then performed in ambient atmosphere at constant amplitude using load ratio R of 0.1. The near threshold fatigue crack growth rate, fatigue threshold and the fatigue crack growth rate in the linear region were determined. Fatigue crack growth behaviour of specimens without any dissolve hydrogen were then compared with the specimens with different concentration of dissolved hydrogen. The test results show that the dissolved hydrogen concentration increases with the increase in charging time in all three heat treated conditions and the hydrogen uptake shows a strong dependence on the microstructure of the alloy. It was also observed that the microstructure has a significant influence of on the fatigue crack growth and SCC behaviour of the alloy with dissolved hydrogen. As the dissolved hydrogen concentration increases, the fatigue threshold was found to decrease and the near threshold crack growth rate increases in all three heat treated conditions showing the deleterious effect of hydrogen, but to a different extent in each condition. Current test results also indicate that the fatigue crack growth rates in the linear region increases as the dissolved hydrogen content increases in all three heat treated conditions. It is also observed that increasing the austempering temperature decreases the resistance to hydrogen embrittlement. An interesting p

Ramasagara Nagarajan, Varun


Asad Umar, DVM, PhD

Dr. Asad Umar received his PhD in Biochemistry and Immunology at the Johns Hopkins University in Baltimore, MD, in 1993. He conducted his postdoctoral training in the laboratories of Patricia Gearhart in Baltimore, MD and Thomas Kunkel at the National Institutes of Environmental Health Sciences in Research Triangle Park, NC. Dr. Umar's main scientific interest is to understand the molecular pathways during gastrointestinal carcinogenesis and applying molecularly targeted and immunologic interventions to prevent cancer.


Fertigation with micronized sulfur rapidly reduces soil pH in highbush blueberry  

Technology Transfer Automated Retrieval System (TEKTRAN)

Blueberry is adapted to low soil pH in the range of 4-5.5. At higher pH, soil is often modified with elemental sulfur (S) prior to planting. A 2-year study was conducted to determine the potential of applying micronized wettable S by fertigation through the drip system to reduce soil pH in highbush ...


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


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

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



PHPostharvest 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 20C and moisture contents from 12 to 303% 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



Recycle of electrolytically dissolved struvite as an alternative to enhance phosphate and nitrogen recovery from swine wastewater.  


Operational parameters such as electric voltage, NaCl, reaction time (RT) and initial struvite amount were optimized for struvite dissolution with a designed electrolysis reactor, and the effect of recycling the dissolved solution on the performance of struvite crystallization was also assessed. The electrolytic reactor was made of plexiglas having titanium plate coated with iridium oxide as anode (surface area: 400 cm(2)) and stainless steel plates as cathodes. For reutilization of dissolved struvite, four runs were conducted with different recycle ratio of the solution. Optimum conditions for the electric voltage, NaCl, RT and initial struvite amount were 7 V, 0.06%, 1.5h and 1.25 g/L, respectively. At the above optimized conditions, 49.17 mg/L phosphate (PO(4)(3-)-P) was dissolved and ammonium-nitrogen (NH(4)-N) got completely removed from the solution. When 0.0, 0.5, 1.0 and 2.0 moles of the dissolved struvite with respect to PO(4)(3-)-P in swine wastewater were recycled along with 0.5M magnesium chloride (MgCl(2)), the PO(4)(3-)-P removal was 63, 69, 71 and 79%, and NH(4)-N was 9, 31, 40 and 53%, respectively. Hence, the performance of struvite formation process was proportionally increased. It is concluded that struvite can be re-dissolved by electrolysis and reused as a source of P and Mg. PMID:21885192

Liu, YingHao; Kumar, Sanjay; Kwag, JungHoon; Kim, JaeHwan; Kim, JeongDae; Ra, ChangSix



Chapter A6. Section 6.2. Dissolved Oxygen  

USGS Publications Warehouse

Accurate data for the concentration of dissolved oxygen in surface and ground waters are essential for documenting changes in environmental water resources that result from natural phenomena and human activities. Dissolved oxygen is necessary in aquatic systems for the survival and growth of many aquatic organisms and is used as an indicator of the health of surface-water bodies. This section of the National Field Manual (NFM) includes U.S. Geological Survey (USGS) guidance and protocols for four methods to determine dissolved-oxygen concentrations: the amperometric, luminescent-sensor, spectrophotometric, and iodometric (Winkler) methods.

Revised by Lewis, Michael Edward



GLOBE Videos: Hydrology Protocols - Dissolved Oxygen (12:06 min)  

NSDL National Science Digital Library

This video introduces the measurement of dissolved oxygen in a water body as an important indicator of ecosystem health, and demonstrates students analyzing a water sample for dissolved oxygen. The resource includes a video and a written transcript, and is supported by the Dissolved Oxygen Protocol in the GLOBE Teacher's Guide. This is one of seven videos on hydrology in the 24-part instructional video series describing scientific protocols used by GLOBE (Global Learning and Observation to Benefit the Environment), a worldwide, hands-on, K-12 school-based science education program.


Effects of gas dissolved in water on critical heat loadings  

SciTech Connect

Surveys have been published of data obtained in experiments with outgassed water and with water in which the gas concentration either was not measured at all or else was measured after outgassing with an inadequate accuracy. It is desirable to estimate the size of the difference between the critical heat loadings calculated and the values found by experiment with nearly zero dissolved gas. For this purpose a system is described having a gas and steam volume compensation system for the coolant, as well as a system for simulating and monitoring the dissolved gas. The error in determining the dissolved gas concentration was not more than /plus or minus/5%. 3 refs.

Fisenko, V.; Katkov, Yu.D.; Lastochkin, A.P.; Maksimov, V.I.



Isolation and chemical characterization of dissolved and colloidal organic matter  

USGS Publications Warehouse

Commonly used techniques for the concentration and isolation of organic matter from water, such as preparative chromatography, ultrafiltration and reverse osmosis, and the methods used to analyze the organic matter obtained by these methods are reviewed. The development of methods to obtain organic matter that is associated with fractions of the dissolved organic carbon other than humic substances, such as organic bases, hydrophilic organic acids and colloidal organic matter are discussed. Methods specifically used to study dissolved organic nitrogen and dissolved organic phosphorous are also discussed. -from Authors

Aiken, G.; Leenheer, J.



Dissolved oxygen as an indicator of bioavailable dissolved organic carbon in groundwater  

USGS Publications Warehouse

Concentrations of dissolved oxygen (DO) plotted vs. dissolved organic carbon (DOC) in groundwater samples taken from a coastal plain aquifer of South Carolina (SC) showed a statistically significant hyperbolic relationship. In contrast, DO-DOC plots of groundwater samples taken from the eastern San Joaquin Valley of California (CA) showed a random scatter. It was hypothesized that differences in the bioavailability of naturally occurring DOC might contribute to these observations. This hypothesis was examined by comparing nine different biochemical indicators of DOC bioavailability in groundwater sampled from these two systems. Concentrations of DOC, total hydrolysable neutral sugars (THNS), total hydrolysable amino acids (THAA), mole% glycine of THAA, initial bacterial cell counts, bacterial growth rates, and carbon dioxide production/consumption were greater in SC samples relative to CA samples. In contrast, the mole% glucose of THNS and the aromaticity (SUVA254) of DOC was greater in CA samples. Each of these indicator parameters were observed to change with depth in the SC system in a manner consistent with active biodegradation. These results are uniformly consistent with the hypothesis that the bioavailability of DOC is greater in SC relative to CA groundwater samples. This, in turn, suggests that the presence/absence of a hyperbolic DO-DOC relationship may be a qualitative indicator of relative DOC bioavailability in groundwater systems.

Chapelle, Francis H.; Bradley, Paul M.; McMahon, Peter B.; Kaiser, Karl; Benner, Ron



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

USGS Publications Warehouse

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

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



Selective Sorption of Dissolved Organic Carbon Compounds by Temperate Soils  

SciTech Connect

Physico-chemical sorption of dissolved organic carbon (DOC) on soil minerals is one of the major processes of organic carbon (OC) stabilization in soils, especially in deeper layers. The attachment of C on soil solids is related to the reactivity of the soil minerals and the chemistry of the sorbate functional groups, but the sorption studies conducted without controlling microbial activity may overestimate the sorption potential of soil. This study was conducted to examine the sorptive characteristics of a diverse functional groups of simple OC compounds (D-glucose, L-alanine, oxalic acid, salicylic acid, and sinapyl alcohol) on temperate climate soil orders (Mollisols, Ultisols and Alfisols) with and without biological degradative processes. Equilibrium batch experiments were conducted using 0-100 mg C L-1 at a solid-solution ratio of 1:60 for 48 hrs and the sorption parameters were calculated by Langmuir model fitting. The amount of added compounds that remained in the solution phase was detected by high performance liquid chromatography (HPLC) and total organic C (TOC) analysis. Soil sterilization was performed by -irradiation technique and experiments were repeated to determine the contribution of microbial degradation to apparent sorption. Overall, Ultisols did not show a marked preference for apparent sorption of any of the model compounds, as indicated by a narrower range of maximum sorption capacity (Smax) of 173-527 mg kg soil-1 across compounds. Mollisols exhibited a strong preference for apparent sorption of oxalic acid (Smax of 5290 mg kg soil-1) and sinapyl alcohol (Smax of 2031 mg kg soil-1) over the other compounds. The propensity for sorption of oxalic acid is mainly attributed to the precipitation of insoluble Ca-oxalate due to the calcareous nature of most Mollisol subsoils and its preference for sinapyl alcohol could be linked to the polymerization of this lignin monomer on 2:2 mineral dominated soils. The reactivity of Alfisols to DOC was in between that of Ultisols and Mollisols. HPLC results revealed significantly higher sorption of D-glucose and L-alanine than did TOC results, and duplicate experiments with sterilized soils confirmed that glucose and alanine were mineralized leading to higher apparent sorption values via HPLC. This study demonstrated that three common temperate soil orders experienced differential sorption of simple OC compounds, indicating that sorbate chemistry plays a significant role in the sorptive stabilization of DOC.

Jagadamma, Sindhu [ORNL; Mayes, Melanie [ORNL; Phillips, Jana Randolph [ORNL



Exercise and Pulmonary Hypertension (PH)  


... Young Adult Issues Dating and Relationships College and Scholarships Family Planning Considering Adoption with PH The Adoption ... Young Adult Issues Dating and Relationships College and Scholarships Family Planning Considering Adoption with PH The Adoption ...


40 CFR 430.10 - Applicability; description of the dissolving kraft subcategory.  

Code of Federal Regulations, 2010 CFR

...GUIDELINES AND STANDARDS THE PULP, PAPER, AND PAPERBOARD...SOURCE CATEGORY Dissolving Kraft Subcategory 430.10...description of the dissolving kraft subcategory. The provisions...production of dissolving pulp at kraft...



Photoreactivity of chromophoric dissolved organic matter transported by the Mackenzie River to the Beaufort Sea  

E-print Network

Photoreactivity of chromophoric dissolved organic matter transported by the Mackenzie River: Chromophoric dissolved organic matter Dissolved organic carbon Photodegradation Mackenzie River Arctic Ocean and min) for the Mackenzie River and a sample from the Mackenzie Shelf. The photoreactivity of Mackenzie

Vincent, Warwick F.


Effect of bacteria and dissolved organics on mineral dissolution kinetics:  

NASA Astrophysics Data System (ADS)

Quantification of the effect of microorganisms and associated organic ligands on mineral dissolution rate is one among the last remaining challenges in modeling of water-rock interactions under earth surface and subsurface environments. This is especially true for deep underground settings within the context of CO2 capture, sequestration and storage. First, elevated CO2 pressures create numerous experimental difficulties for performing robust flow-through experiments at a given saturation state. Second, reactivity of main rock-forming minerals in abiotic systems at pCO2 >> 1 atm and circumneutral pH is still poorly constrained. And third, most of microbial habitats of the subsurface biosphere are not suitable for routine culturing in the laboratory, many of them are anaerobic and even strictly anaerobic, and many bacteria and archae cultures can live only in the consortium of microorganisms which is very hard to maintain at a controlled and stable biomass concentration. For experimental modeling of bio-mineral interactions in the laboratory, two other main conceptual challenges exist. Typical concentration of dissolved organic carbon that serves as a main nutrient for heterotrophic bacteria in underground waters rarely exceeds 3-5 mg/L. Typical concentration of DOC in nutrient media used for bacteria culturing is between 100 and 10,000 mg/L. Therefore, performing mineral-bacteria interactions in the laboratory under environmentally-sound conditions requires significant dilution of the nutrient media or the use of flow-through reactors. Concerning the effect of organic ligands and bacterial excudates on rock-forming mineral dissolution, at the present time, mostly empirical (phenomenological) approach can be used. Indeed, the pioneering studies of Stumm and co-workers have established a firm basis for modeling the catalyzing and inhibiting effects of ligands on metal oxide dissolution rate. This approach, very efficient for studying the interaction of organic and inorganic ligands with trivalent metal oxides, is based on applying multiple spectroscopic techniques allowing to reveal the chemical structure of adsorbed complexes. However, due to i) low surface area of most rock-forming minerals (carbonates, non-clay silicates), ii) difficulties of applying surface spectroscopic techniques at elevated pressures, and iii) very complex nature of bacterial exometabolites, it is not possible at the present time, to use rigorous surface complexation approach for rationalizing ligand- and bacteria-affected mineral dissolution under sub-surface CO2 storage environment. In this work, we present examples of overcoming these difficulties via concerted study of olivine, wollastonite and calcite interaction with heterotrophic bacteria and methanogenic archaes.

Pokrovsky, Oleg; Shirokova, Liudmila; Benezeth, Pascale; Zabelina, Svetlana



Dissolution of phosphate rocks in soils. 2. Effect of pH on the dissolution and plant availability of phosphate rock in soil with pH dependent charge  

Microsoft Academic Search

The effect of soil pH on the dissolution of phosphate rocks (PRs) and the subsequent availability of the dissolved inorganic phosphorus (Pi) to plants was examined in a volcanic soil adjusted to different pH values. Potassium dihydrogen orthophosphate (KH2PO4) and three PRs, Nauru (NPR), Jordan (JPR) and North Carolina (NCPR) were incubated with the pH-amended soils at a rate of

N. S. Bolan; M. J. Hedley



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

USGS Publications Warehouse

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 1300 m study area. All four metals were transported through this mixing zone without significant losses to the streambed, and they exhibited transformations from dissolved to colloidal forms to varying degrees during the mixing process. Nearly all of the Al formed colloidal hydrous Al oxides (HAO) as pH increased (4.8-6.5), whereas colloidal hydrous Fe oxides (HFO) were supplied by Cement Creek as well as formed in the mixing zone primarily at higher pH (>6.5). The short travel time through the mixing zone (approx. 40 min) and pH limited the formation of HFO from dissolved Fe2+ supplied by Cement Creek. Although the proportions of HAO and HFO varied as the streams mixed, the colloidal sorbent typically was enriched in HAO relative to HFO by a factor of 1.5-2.1 (by mole) in the pH range where dissolved-to-colloidal partitioning of Cu and Zn was observed. Model simulations of sorption by HFO (alone) greatly underestimated the dissolved-to-colloidal partitioning of Zn. Previous studies have shown that HAO-HFO mixtures can sorb greater amounts of Zn than HFO alone, but the high Zn-to-sorbent ratio in this mixing zone could also account for greater partitioning. In contrast to Zn, comparisons with model simulations did not show that Cu sorption was greater than that for HFO alone, and also indicated that sorption was possibly less than what would be expected for a non-interactive mixture of these two sorbents. These field results for Cu, however, might be influenced by (organic) complexation or other factors in this natural system. Laboratory mixing experiments using natural source waters (upstream of the confluence) showed that the presence of HFO in the mixed sorbent resulted in greater Cu partitioning than for HAO alone, and that the effect was greater with increasing (mole fraction) HFO. This was consistent with field results that showed greater Cu sorption when additional HFO was formed in the downstream reach of the mixing zone. Further research is needed to identify the significance of surface-related mechanisms specific to HAO-HFO mixtures that could affect the partitioning of Cu in natural systems.

Schemel, L.E.; Kimball, B.A.; Runkel, R.L.; Cox, M.H.



Sediment-water interactions affecting dissolved-mercury distributions in Camp Far West Reservoir, California  

USGS Publications Warehouse

Field and laboratory studies were conducted in April and November 2002 to provide the first direct measurements of the benthic flux of dissolved (0.2-micrometer filtered) mercury species (total and methylated forms) between the bottom sediment and water column at three sampling locations within Camp Far West Reservoir, California: one near the Bear River inlet to the reservoir, a second at a mid-reservoir site of comparable depth to the inlet site, and the third at the deepest position in the reservoir near the dam (herein referred to as the inlet, midreservoir and near-dam sites, respectively; Background, Fig. 1). Because of interest in the effects of historic hydraulic mining and ore processing in the Sierra Nevada foothills just upstream of the reservoir, dissolved-mercury species and predominant ligands that often control the mercury speciation (represented by dissolved organic carbon, and sulfides) were the solutes of primary interest. Benthic flux, sometimes referred to as internal recycling, represents the transport of dissolved chemical species between the water column and the underlying sediment. Because of the affinity of mercury to adsorb onto particle surfaces and to form insoluble precipitates (particularly with sulfides), the mass transport of mercury in mining-affected watersheds is typically particle dominated. As these enriched particles accumulate at depositional sites such as reservoirs, benthic processes facilitate the repartitioning, transformation, and transport of mercury in dissolved, biologically reactive forms (dissolved methylmercury being the most bioavailable for trophic transfer). These are the forms of mercury examined in this study. In contrast to typical scientific manuscripts, this report is formatted in a pyramid-like structure to serve the needs of diverse groups who may be interested in reviewing or acquiring information at various levels of technical detail (Appendix 1). The report enables quick transitions between the initial summary information (figuratively at the top of the pyramid) and the later details of methods or results (figuratively towards the base of the pyramid) using hyperlinks to supporting figures and tables, and an electronically linked Table of Contents. During two sampling events, two replicate sediment cores (Coring methods; Fig. 2) from each of three reservoir locations (Fig. 1) were used in incubation experiments to provide flux estimates and benthic biological characterizations. Incubation of these cores provided ?snapshots? of solute flux across the sediment-water interface in the reservoir, under benthic, environmental conditions representative of the time and place of collection. Ancillary data, including nutrient and ligand fluxes, were gathered to provide a water-quality framework from which to compare the results for mercury. The following major observations from interdependent physical, biological, and chemical data were made:

Kuwabara, James S.; Alpers, Charles N.; Marvin-DiPasquale, Mark; Topping, Brent R.; Carter, James L.; Stewart, A. Robin; Fend, Steven V.; Parchaso, Francis; Moon, Gerald E.; Krabbenhoft, David P.



The marine biogeochemistry of dissolved and colloidal iron  

E-print Network

Iron is a redox active trace metal micronutrient essential for primary production and nitrogen acquisition in the open ocean. Dissolved iron (dFe) has extremely low concentrations in marine waters that can drive phytoplankton ...

Fitzsimmons, Jessica Nicole




EPA Science Inventory

This report presents design procedures and guidelines for the selection of aeration equipment and dissolved (DO) control systems for activated sludge treatment plants. Aeration methods, equipment and application techniques are examined and selection procedures offered. Various DO...