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Humic substances mineralization: the variation of pH, electrical conductivity and optical density  

Microsoft Academic Search

Humic substances mineralization: the variation of pH, electrical conductivity and optical density. The variation of pH, electrical conductivity and optical density was described during the mineralization of humic substances (humic acid: HA and fulvic acid: FA) extracted from different sources: sediment, dissolved organic matter from 120 days of decomposition of aquatic macrophytes (Scirpus cubensis and Cabomba piauhyensis) and from water

Rodovia Washington Luis


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.



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

Microsoft Academic Search

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

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



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



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.


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



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.



Influence of Dissolved Organic Carbon and pH on Containment Sorption to Sediment  

SciTech Connect

Low-Level Waste buried on the SRS contains cellulosic materials, Including wood, paper, and cardboard. Once buried, these materials are expected to degrade to form cellulose degradation products (CDP). Such materials are expected to influence radionuclide speciation in such a way that the radionuclides will sorb less to SRS Subsurface sediments and therefore would migrate more rapidly from the disposal site. The objective of this study was to quantify through laboratory work the influence of CDP and pH on radionuclide sorption to SRS subsurface sediments. The intent of this work was to create a Kd look-up table as a function of radionuclide, pH, and CDP concentration that could be used in future performance assessment calculations. Previous CDP-impacted Kd values were generated using two chemical analogues, UO2 2+ and Eu3+. This study collected data from a wider range of analogues to validate and/or refine this approach. An incomplete-randomized-block-statistical design was used in a laboratory sorption study involving 2 soil types (sandy and clay textured), 5 dissolved organic carbon concentrations (a measure of CDP), and 3 pH levels. Nonradioactive solutes were used as chemical analogues to the radionuclides of interest to the Low-Level Waste Performance Assessment: monovalent cations (K+ and Cs+), divalent cations (Ni2+ and Sr2+), trivalent cations (Ce3+ and Eu3+), tetravalent cations (Th4+ and Zr4+), and an anion (ReO4-). Analogues were matched to approximately 30 radionuclides based on similarities in periodicity and chemical properties. All CDP-impacted Kd values generated from this study were equal to or greater than those used in previous performance assessments. These larger Kd values may result in a greater Waste Acceptance Criteria (WAC), which in turn may permit greater amounts of Low-Level Waste to be safely disposed on site, saving the site the expense of shipping the waste off-site for disposal.




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

E-print Network

experimentation with pH and dissolved oxygen control{ Harry L. T. Lee,a Paolo Boccazzi,b Rajeev J. Ram21 ) without introducing bubbles, and closed loop control over dissolved oxygen and pH (¡0, with 100 mL working volume, comprising a peristaltic oxygenating mixer and microfluidic injectors

Sinskey, Anthony J.


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.



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

USGS Publications Warehouse

In July and August of 1994, the U. S. Geological Survey in cooperation with the Oregon Department of Environmental Quality (ODEQ) collected data to document the spatial extent and diel variability of dissolved oxygen (DO) concentrations and pH levels in selected reaches of streams in the upper Willamette River Basin. These data were also collected to identify primary factors that control DO concentrations downstream from major point sources as well as to provide ODEQ with data to refine calibration of their steady-state DO and nutrient models for the upper Willamette River Basin. All of the reaches studied had diel variations in DO and pH. The magnitude of the diel variations in DO ranged from 0.2 to 3.9 milligrams per liter (7 to 50 percent-saturation units based on ambient water temperature and barometric pressure) and in pH from 0.3 to 1.4 units. However, of the reaches studied, only the Coast Fork Willamette River from river mile (RM) 21.7 to 12.5 and the Willamette River from RM 151 to 141.6 had field measured violations of State standards for DO and pH. DO concentration and pH in water depend on many factors. Data were collected to examine several major factors, including BOD (biochemical oxygen demand), carbonaceous BOD, nitrogenous BOD, and measures of photosynthetic activity. Of the four study reaches, only a short stretch of the Coast Fork Willamette River has potential for important levels of oxygen consumption from BOD or nitrification. Additionally, water-column primary-productivity measurements indicated that respiration and photosynthesis by free-floating algae did not explain the observed diel variations in DO in the study reaches. Results from a simple mathematical model incorporating measures of community respiration and net primary productivities indicated that periphyton are capable of producing a diel variation of the order of magnitude observed during the August study period. In the Willamette River near Peoria, the combined periphyton DO consumption and production estimate at RM 151 (2.4 mg/L) and RM 144.6 (1.7 mg/L) would account for 90 and 63 percent, respectively, of the observed diel fluctuation. The estimates for the Corvallis reach at RM 132.6 (0.4 mg/L) and RM 130.7 (2.9 mg/L) had a considerably larger range of 36 to 264 percent of DO saturation, respectively. Therefore, because BOD and phytoplankton do not appear to be important contributors to diel DO fluctuations, periphyton are likely the primary contributor to diel fluctuations in the upper Willamette River Basin during July and August.

Pogue, T.R.; Anderson, C.W.




EPA Science Inventory

A recent conceptual model links high bulk electrical conductivities at hydrocarbon impacted sites to higher total dissolved solids (TDS) resulting from enhanced mineral weathering due to acids produced during biodegradation. In this study, we investigated the vertical distributio...


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

PubMed Central

Using a thermal polymerization approach and polymerizable pH and oxygen sensing monomers with green and red emission spectra, respectively, new pH, oxygen, and their dual sensing membranes were prepared using poly(2-hydroxyethyl methacrylate)-co-poly(acrylamide) as a matrix. The sensors were grafted on acrylate-modified quartz glass and characterized under different pH values, oxygen concentrations, ion strengths, temperatures and cell culture media. The pH and oxygen sensors were excited using the same excitation wavelength and exhibited well-separated emission spectra. The pH-sensing films showed good response over the pH range 5.5 to 8.5, corresponding to pKa values in the biologically-relevant range between 6.9 and 7.1. The oxygen-sensing films exhibited linear Stern-Volmer quenching responses to dissolved oxygen. As the sensing membranes were prepared using thermally initiated polymerization of sensing moiety-containing monomers, no leaching of the sensors from the membranes to buffers or medium was observed. This advantageous characteristic accounts in part for the sensors' biocompatibility without apparent toxicity to HeLa cells after 40 hours incubation. The dual-sensing membrane was used to measure pH and dissolved oxygen simultaneously. The measured results correlated with the set-point values. PMID:20543884

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



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

Microsoft Academic Search

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

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


Leachability and desorption of PCBs from soil and their dependency on pH and dissolved organic matter.  


pH affects both soil-water partitioning coefficient (Kd) of polychlorinated biphenyls (PCBs) and dissolved organic matter (DOM), thereby influencing PCBs' leachability from contaminated soils. To explore these incompletely understood interactions, the leachability of 11 selected PCBs in a naturally aged soil was investigated in pH static leaching tests spanning a wide pH range (2 to 9). The K(d) was calculated for each of the PCBs, based on their observed concentrations in the soil and leachates obtained from each test. The concentration and composition of DOM in each leachate were also determined, the latter using FTIR spectroscopy. Correlations between the DOM's FTIR spectra and K(d) values were investigated by orthogonal projections to latent structures. The log K(d)-values varied among the PCB congeners and were most variable at low pH, but the values for all studied congeners decreased with increasing pH, by up to 3 log units (for PCB 187). In the pH 5-7 interval, an abrupt decrease in log K(d) values with increases in pH was observed, although the total organic carbon content remained relatively stable. The FTIR data indicate that fulvic and humic acids in DOM partially deprotonate as the pH rises from 5 to 7. PMID:25192928

Badea, Silviu-Laurentiu; Mustafa, Majid; Lundstedt, Staffan; Tysklind, Mats



Stream Monitoring 1. Students learn how researchers test three stream parameters: temperature, dissolved  

E-print Network

: temperature, dissolved oxygen and pH. 2. Formulate a hypothesis and test it. Background Water quality flow, dissolved oxygen, temperature, pH, conductivity, nitrogen, phosphorus, total solids, turbidity, and fecal bacteria. Note: in this activity we are only measuring temperature, pH and dissolved oxygen

Schladow, S. Geoffrey


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...


Influence of pH, hardness, dissolved organic carbon concentration, and dissolved organic matter source on the acute toxicity of copper to Daphnia magna in soft waters: implications for the biotic ligand model.  


The influence of pH, dissolved organic carbon (DOC) concentration, water hardness, and dissolved organic matter (DOM) source on the acute toxicity of copper were investigated with standardized 48-h Daphnia magna toxicity tests. Toxicity tests were conducted according to a four-factor complete factorial design. Nominal factor levels were as follows: pH 6 and 8; DOC, 2.5 and 10 mg/L; hardness, 10, 20, and 40 mg/L as CaCO3; and two DOM sources (collected from the Black River and Edisto River, SC, USA). The experimental design resulted in 24 different factor level combinations. Results indicated that all factors had significant effects on copper toxicity. Furthermore, a strong interactive effect of DOC concentration and pH was detected. Because the biotic ligand model (BLM) has become a widely used tool for predicting toxicity and interpreting toxicity test results, its performance with these data was evaluated. Seventy percent of BLM predictions were within twofold of the observed median lethal concentrations. However, BLM parameters could be adjusted to improve model performance with this data set. This analysis suggested that in soft waters, the CuOH+ complex binds more strongly with the biotic ligand and that the competitive effect of hardness cations should be increased. The results of the present study may have implications for application of the BLM to some types of surface waters. Furthermore, a comprehensive analysis of BLM performance with all available data should be performed, and necessary updates to model parameters should be made to produce the most robust and widely applicable model. PMID:19265455

Ryan, Adam C; Tomasso, Joseph R; Klaine, Stephen J



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

NASA Astrophysics Data System (ADS)

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

Mammitzsch, K.; Jost, G.; Jürgens, K.



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



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



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

NSDL National Science Digital Library

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



Influence of dissolved oxygen concentration on intracellular pH for regulation of Aspergillus niger growth rate during citric acid fermentation in a stirred tank bioreactor.  


In this paper we report the regulation of Aspergillus niger growth rate during citric acid fermentation in a stirred tank bioreactor. For this, the influence of dissolved oxygen concentration in a medium on intracellular pH values and consequently on overall microbial metabolism was emphasized. Intracellular pH of mycelium grown under different concentrations of dissolved oxygen in the medium was determined. Sensitivity of proteins toward proton concentration is well recognized, therefore pH influences on the activities of key regulatory enzymes of Aspergillus niger were determined at pH values similar to those detected in the cells grown under lower dissolved oxygen concentrations. The results have shown significantly reduced specific activities of hexokinase, 6-phosphofructokinase and glucose-6-phosphate dehydrogenase in more acidic environment, while pyruvate kinase was found to be relatively insensitive towards higher proton concentration. As expected, due to the reduced specific activities of regulatory enzymes under more acidic conditions, overall metabolism should be hindered in the medium with lower dissolved oxygen concentration which was confirmed by detecting the reduced specific growth rates. From the studies, we conclude that dissolved oxygen concentration affects the intracellular pH and thus growth rate of Aspergillus niger during the fermentation process. PMID:15951848

Haq, Ikram-Ul; Ali, Sikander; Qadeer, M A



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.



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 ...


Anion Conductance of Frog Muscle Membranes: One Channel, Two Kinds of pH Dependence  

PubMed Central

Anion conductance and permeability sequences were obtained for frog skeletal muscle membranes from the changes in characteristic resistance and transmembrane potential after the replacement of one anion by another in the bathing solution. Permeability and conductance sequences are the same. The conductance sequence at pH = 7.4 is Cl- Br- > NO3- > I- > trichloroacetate ? benzoate > valerate > butyrate > proprionate > formate > acetate ? lactate > benzenesulfonate ? isethionate > methylsulfonate > glutamate ? cysteate. The anions are divided into two classes: (a) Chloride-like anions (Cl- through trichloroacetate) have membrane conductances that decrease as pH decreases. The last six members of the complete sequence are also chloride like. (b) Benzoate-like anions (benzoate through acetate) have conductances that increase as pH decreases. At pH = 6.7 zinc ions block Cl- and benzoate conductances with inhibitory dissociation constants of 0.12 and 0.16 mM, respectively. Chloride-like and benzoate-like anions probably use the same channels. The minimum size of the channel aperture is estimated as 5.5 x 6.5 Å from the dimensions of the largest permeating anions. A simple model of the channel qualitatively explains chloride-like and benzoate-like conductance sequences and their dependence on pH. PMID:4542368

Woodbury, J. W.; Miles, P. R.



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.



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

Microsoft Academic Search

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

Dimitrios Savvas; Konstantinos Adamidis



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

PubMed Central

Epsilonproteobacteria have been found globally distributed in marine anoxic/sulfidic areas mediating relevant transformations within the sulfur and nitrogen cycles. In the Baltic Sea redox zones, chemoautotrophic epsilonproteobacteria mainly belong to the Sulfurimonas gotlandica GD17 cluster for which recently a representative strain, S. gotlandica GD1T, could be established as a model organism. In this study, the potential effects of changes in dissolved inorganic carbon (DIC) and pH on S. gotlandica GD1T were examined. Bacterial cell abundance within a broad range of DIC concentrations and pH values were monitored and substrate utilization was determined. The results showed that the DIC saturation concentration for achieving maximal cell numbers was already reached at 800??mol?L?1, which is well below in situ DIC levels. The pH optimum was between 6.6 and 8.0. Within a pH range of 6.6–7.1 there was no significant difference in substrate utilization; however, at lower pH values maximum cell abundance decreased sharply and cell-specific substrate consumption increased. PMID:24376054

Mammitzsch, Kerstin; Jost, Günter; Jürgens, Klaus



Spatial and temporal variability of turbidity, dissolved oxygen, conductivity, temperature, and fluorescence in the lower Mekong River–Tonle Sap system identified using continuous monitoring  

Microsoft Academic Search

Continuous monitoring of turbidity, dissolved oxygen (DO), conductivity, temperature, and fluorescence was done at five locations on the Tonle Sap Lake and the Mekong–Bassac Rivers near Phnom Penh, Cambodia, between 2004 and 2010 using autonomous datasondes. Seasonal, daily, and spatial trends were clearly identified in the data and were related to the annual monsoon rainy season–dry season cycle, system metabolism,

K. N. Irvine; J. E. Richey; G. W. Holtgrieve; J. Sarkkula; M. Sampson



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 combined effects of hardness, pH, and dissolved organic carbon on the chronic toxicity of Zn to D. magna: development of a surface response model.  


The effect of changes in pH, hardness, and dissolved organic carbon (DOC) and the possible interactions among these parameters on the chronic toxicity of zinc to D. magna were investigated. Based on a Central Composite Design, models were developed that can explain the observed variation in EC(10) and EC(50) as a function of these toxicity modifying factors. All three parameters significantly altered the observed effect concentrations based on net reproductive rate. The largest differences in 21-day EC(10)s and EC(50)s caused by these factors were 10.1 and 4.9, respectively. An increase in pH and/or DOC decreased zinc toxicity. The significant interaction between pH and DOC on observed chronic Zn toxicity is in accordance with earlier reported increased sorption efficiency of Zn to humic substances at higher pH levels. Lowest Zn toxicity was observed in tests performed with moderately hard test media (between 200 and 300 mg/L as CaCO(3)). Lower or higher hardness of the test medium resulted in lower effect concentrations. Based on physico-chemical characteristics of the test media, developed models can be used to explain the variation between reported NOECs for Zn and may improve current environmental risk assessment procedures of metals. PMID:12520393

Heijerick, D G; Janssen, C R; De Coen, W 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?1 mg/L) and lower pH (pH = 6), ammonium was easily released into overlying water, potentially triggering algal blooms. Conversely aerobic conditions (DO = 8-10 mg/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



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.



Defining Dissolving  

NSDL National Science Digital Library

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

Kessler, James H.; Galvan, Patricia M.



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


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

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



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.



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


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

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



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



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

PubMed Central

Poly(ortho-phenylene diamine) synthesis enabled by the catalytic oxidase-like activity of nanoceria was accomplished for applications in electronics, medicine and biotechnology. The polymer shows unique morphology, conductivity and photoluminescence based on pH of the solution during synthesis. The various poly(ortho-phenylene diamine) preparations were characterized by UV-visible spectroscopy, scanning electron microscopy, fluorescence spectroscopy, fluorescence microscopy, high pressure liquid chromatography and cyclic voltammetry. Poly(ortho-phenylene diamine) synthesized at pH 1.0 by nanoceria was selected to be extensively studied based on the fast synthetic kinetics and the resulting conductive and photoluminiscent properties for various applications. PMID:22920917

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



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



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


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

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




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...


Determination of Proton Flux and Conductance at pH 6.8 through Single Fo Sectors from Escherichia coli  

PubMed Central

We have developed a mathematical model in concert with an assay that allows us to calculate proton (H+) flux and conductance through a single Fo of the F1Fo ATP synthase. Lipid vesicles reconstituted with just a few functional Fo from Escherichia coli were loaded with 250 mM K+ and suspended in a low K+ solution. The pH of the weakly buffered external solution was recorded during sequential treatment with the potassium ionophore valinomycin, the protonophore carbonyl cyanide 3-chlorophenylhydrazone, and HCl. From these pH traces and separate determinations of vesicle size and lipid concentration we calculate the proton conductance through a single Fo sector. This methodology is sensitive enough to detect small (15%) conductance changes. We find that wild-type Fo has a proton flux of 3100 ± 500 H+/s/Fo at a transmembrane potential of 106 mV (25°C and pH 6.8). This corresponds to a proton conductance of 4.4 fS. PMID:15339819

Franklin, Michael J.; Brusilow, William S. A.; Woodbury, Dixon J.



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.

Washington State University Department of Ecology


Numerical Simulations of Bubble Dynamics and Heat Transfer in Pool Boiling---Including the Effects of Conjugate Conduction, Level of Gravity, and Noncondensable Gas Dissolved in the Liquid  

NASA Astrophysics Data System (ADS)

Due to the complex nature of the subprocesses involved in nucleate boiling, it has not been possible to develop comprehensive models or correlations despite decades of accumulated data and analysis. Complications such as the presence of dissolved gas in the liquid further confound attempts at modeling nucleate boiling. Moreover, existing empirical correlations may not be suitable for new applications, especially with regards to varying gravity level. More recently, numerical simulations of the boiling process have proven to be capable of reliably predicting bubble dynamics and associated heat transfer by showing excellent agreement with experimental data. However, most simulations decouple the solid substrate by assuming constant wall temperature. In the present study complete numerical simulations of the boiling process are performed---including conjugate transient conduction in the solid substrate and the effects of dissolved gas in the liquid at different levels of gravity. Finite difference schemes are used to discretize the governing equations in the liquid, vapor, and solid phases. The interface between liquid and vapor phases is tracked by a level set method. An iterative procedure is used at the interface between the solid and fluid phases. Near the three-phase contact line, temperatures in the solid are observed to fluctuate significantly over short periods. The results show good agreement with the data available in the literature. The results also show that waiting and growth periods can be related directly to wall superheat. The functional relationship between waiting period and wall superheat is found to agree well with empirical correlations reported in the literature. For the case of a single bubble in subcooled nucleate boiling, the presence of dissolved gas in the liquid is found to cause noncondensables to accumulate at the top of the bubble where most condensation occurs. This results in reduced local saturation temperature and condensation rates. The numerical predictions show reasonable agreement with the results from experiments performed at microgravity. For nucleate boiling at microgravity the simulations predict a drastic change in vapor removal pattern when compared to Earth normal gravity. The predictions match well with experimental results. However, simulated heat transfer rates were significantly under-predicted.

Aktinol, Eduardo


Sensitivity of high-conductance potassium channels in synaptosomal membranes from the rat brain to intracellular pH  

Microsoft Academic Search

High-conductance potassium channels have been studied in inside-out patches excised from proteoliposomes reconstituted from giant liposomes and rat brain synaptosomes. Acid pH in the medium reduced single channel current amplitude and increased the mean open probability and the frequency of channel opening. This was accompanied by a shortening of the open time constant at positive potential and by shortening of

Alena Habartovfi; Jan Kr?šek; Hana Zemková



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.



Modelling Al competition for heavy metal binding by dissolved organic matter in soil and surface waters of acid and neutral pH  

Microsoft Academic Search

Published field data on the activity of Al3+ (aAl3+) in temperate soil and surface waters of pH 3.3–7.1 have been assembled, and empirical equations describing the dependence of log aAl3+ on pH derived. For soils, two equations are necessary, one describing mineral, or high-Al, soils and the other low-Al soils. In each case, the data at higher pH (>5.5 or

E. Tipping




E-print Network

ANISOTROPIC THERMAL CONDUCTIVITY IN A DIRTY TYPE II SUPERCONDUCTOR J.P.M. Van der Veeken, P.H. Kes, The Netherlands Abstract.- Thermal conductivity measurements have been carried out on a Pb - 21 at.% In alloy (PWTK) /l/. In this way they determined the electronic con- tribution to the thermal conductivity

Boyer, Edmond


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...


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



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




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...


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.



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.



Conduction of Electrical Current to and Through the Human Body: A Review Raymond M. Fish, PhD, MD, FACEP,a  

E-print Network

clinical effects. Conclusions: There are a variety of types of electrical contact, each with importantConduction of Electrical Current to and Through the Human Body: A Review Raymond M. Fish, PhD, MD is to explain ways in which electric current is conducted to and through the human body and how this influences

Illinois at Urbana-Champaign, University of


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



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.



pH aspects of transient changes in conduction velocity in isolated heart fibers after partial replacement of chloride with organic anions  

Microsoft Academic Search

Conduction velocity in isolated rabbit atrial fibers was continuously measured in solutions having a different anionic composition. When 20 mmol\\/l of chloride was replaced by 20 mmol\\/l lactate or other anions of weak organic acids at constant pH 6.8, biphasic initial transient changes in conduction velocity were observed. The produced transient changes had a greater amplitude with organic acids which

R. Marrannes; A. de Hemptinne; I. Leusen



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




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...



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...


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

Microsoft Academic Search

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

R. M. W. Amon; R. Benner



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


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

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



Spatial variability of exchangeable sodium, electrical conductivity, soil pH and boron content in salt- and sodium-affected areas of the Igdir plain (Turkey)  

Microsoft Academic Search

The objective of this study is to assess spatial distribution patterns of exchangeable sodium percentage (ESP), electrical conductivity (EC), soil pH and boron content (B) of salt-and sodium-affected soils in the Igdir plain. The research area, 1000 m×1000 m in size, was divided into 100 m×100 m grid squares. Soil samples from three different depths (0–30; 30–60; 60–90 cm) were

Osman Ardahanlioglu; Taskin Oztas; Salih Evren; Hasbi Yilmaz; Zeynep N Yildirim



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.




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...


Diphtheria toxin at low pH depolarizes the membrane, increases the membrane conductance and induces a new type of ion channel in Vero cells.  

PubMed Central

Receptor-dependent translocation of diphtheria toxin across the surface membrane of Vero cells was studied using patch clamp techniques. Translocation was induced by exposing cells with surface-bound toxin to low pH. Whole cell current and voltage clamp recordings showed that toxin translocation was associated with membrane depolarization and increased membrane conductance. The conductance increase was voltage independent, with a reversal potential of approximately 15 mV. This value was unaffected by changing the Cl- gradient across the membrane and microfluorometric measurements showed that the cytosolic Ca2+ concentration was only marginally elevated by the translocation. The conductance increase is thus mainly due to monovalent cations. Exposing outside-out and cell-attached patches with bound toxin to low pH induced a new type of ion channel in the membrane. The channel current was inward at negative membrane potentials and the single channel conductance was approximately 30 pS. This value is about three times larger than for receptor-independent channels induced by diphtheria toxin or toxin fragments in artificial lipid membranes. PMID:7523112

Eriksen, S; Olsnes, S; Sandvig, K; Sand, O



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.



Method for dissolving clay  

Microsoft Academic Search

A method is described for dissolving clay which comprises contacting the clay alternately with separate slugs of a hydrogen ion-containing chemical and a fluoride ion-containing chemical. The hydrogen ions and fluoride ions react on the surface of the clay to produce hydrofluoric acid to dissolve the clay. The method is particularly valuable in dissolving the clay in a mixture of




Partial nitrification under limited dissolved oxygen conditions  

Microsoft Academic Search

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

Wang Jianlong; Yang Ning



Influence of pH and TOC concentration on Cu, Zn, Cd, and Al speciation in rivers  

Microsoft Academic Search

Dissolved (dissolved) and particulate (total, minus <0.45?m filtered) concentrations of Cu, Zn, Cd, (Al) in eight (three) mining polluted rivers were determined by atomic absorption spectrometry (flame and graphite furnace). The metal size distribution in the rivers was compared to pH, Ca concentration, alkalinity, conductivity, and total organic carbon (TOC). Data plots

Pål Gundersen; Eiliv Steinnes



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.

Nancy P. Moreno



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

NASA Astrophysics Data System (ADS)

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

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



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


Dissolved aluminum in the Gulf of Mexico  

E-print Network

and unswerving Rickness, IMAX. Vl TABLE OF CONTENTS Page ABSTRACT ACKNOWLEDGEMENTS TABLE OF CONTENTS Vi LIST OF TABLES V1. 1. LIST OF FIGURES INTRODUCTION THE NORTHWESTERN GULF OF MEXICO PRECIPITATION AND DISSOLUTION OF ALUMINUM THE CONCENTRATION... and residence time estimates 4) Mississippi River flux and residence time estimates V I I I LIST OF FIGURES Figure Page 1) Location map, Northwestern Gulf of Mexico 2) Aluminum hydroxide pH diagram 3) Clay dissolution in sea water 4) Dissolved aluminum...

Myre, Peggy Lynne



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



Voltammetric determination of dissolved iron and its speciation in freshwater  

Microsoft Academic Search

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

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



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



A Dissolving Challenge  

NSDL National Science Digital Library

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

Kessler, James H.; Galvan, Patricia M.



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.



Dissolving Different Liquids in Water  

NSDL National Science Digital Library

In this activity, learners 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, learners can conclude that while some liquids may dissolve in water, different liquids dissolve in water to different extents. Adult supervision recommended.

James H. Kessler




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...


Monitoring pH and ORP in a SHARON reactor.  


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

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



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

NASA Astrophysics Data System (ADS)

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

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



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.



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



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



Artificial neural network modeling of dissolved oxygen in reservoir.  


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

Chen, Wei-Bo; Liu, Wen-Cheng



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


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

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



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.




The Measurement of Dissolved Oxygen  

ERIC Educational Resources Information Center

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

Thistlethwayte, D.; And Others



Monitoring diel dissolved oxygen dynamics through integrating wavelet denoising and temporal neural networks.  


Diel dissolved oxygen (DO) time series measured continuously using proximal sensors in situ for a temperate lake were denoised using discrete wavelet transform (DWT) with the orthogonal wavelet families of coiflet, daubechies, and symmlet with order of 10. Diel DO time series denoised were modeled using nine temporal artificial neural networks (ANNs) as a function of water level, water temperature, electrical conductivity, pH, day of year, and hour. Our results showed that time-lag recurrent network (TLRN) using denoised data emulated diel DO dynamics better than the best-performing TLRN using the original data, time-delay neural network (TDNN), and recurrent network (RNN). Daubechies basis dealt with diel DO data slightly better than the other bases given its coefficient of determination (r (2)?=?87.1 %), while symmlet performed slightly better than the other bases in terms of root mean square error (RMSE?=?1.2 ppm) and mean absolute error (MAE?=?0.9 ppm). PMID:24100799

Evrendilek, Fatih; Karakaya, Nusret



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

NASA Technical Reports Server (NTRS)

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

Viterna, Larry A.



Removal of dissolved metals by plant tissue  

SciTech Connect

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

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




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.




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.



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


The diffusion of dissolved silica in dilute aqueous solution  

NASA Astrophysics Data System (ADS)

The diffusion coefficient of dissolved silica at 25.5 ± .5° C was determined as a function of concentration using a non-steady-state method whereby agar-gelled solutions containing dissolved silica from 0.09 to 1.50 mM ( pH = 5.5) were placed in contact with distilled water in glass cells. Diffusion coefficients were obtained by measuring the dissolved silica content of the distilled water after a given length of time. The measured diffusion coefficients decreased as a function of increasing dissolved silica concentration, which is thought to reflect an increase in dimeric silica according to the equilibrium: 2 Si( OH) 4 = Si2O( OH) 6 + H2O. The tracer diffusion coefficients for Si(OH) 4 and Si 2O(OH) 6 and an association constant for the above reaction were determined by fitting the following equation to the experimental data: Dobs = ?Dmonomer + (1 - ?) Ddimer where ? is the fraction of total dissolved silica which is Si(OH) 4. The best fit yielded tracer D's for Si(OH) 4 and Si 2O(OH) 6 of 2.2 and 1.0 (in units of 10 -5 cm 2 sec -1), respectively, and an association constant of 330.

Applin, Kenneth R.



Dissolving a Substance in Different Liquids  

NSDL National Science Digital Library

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

James H. Kessler



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?=?27°C) and lower in the winter (average?=?235??M – WT?=?17°C), with no significant variability throughout the daily cycles. CO2 concentrations presented a different pattern, with a minimum in the warm waters of the summer period (8.31??M) and a maximum in the spring (37.13??M). Daily trends were observed for pH, DO, WT, and CO2. At an annual scale, both biological and physical-chemical controls were important regulators of CO2. HB abundance and biomass were higher in the winter sampling (5.60?×?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?×?108–0.68?×?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; Antônio, Regina V.; Petrucio, Maurício M.



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


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

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



Approved Module Information for PH3603, 2014/5 Module Title/Name: Pharmaceutical Formulation III Module Code: PH3603  

E-print Network

Module Code: PH3603 School: Life and Health Sciences Module Type: Standard Module New Module? No Module prodrugs and rapidly dissolving system. Design, release mechanisms, release rates and models. Factors

Neirotti, Juan Pablo


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

NASA Astrophysics Data System (ADS)

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

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



Wormhole formation in dissolving fractures  

Microsoft Academic Search

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

P. Szymczak; A. J. C. Ladd



Dissolved oxygen and fish behavior  

Microsoft Academic Search

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

Donald L. Kramer



Phase fluorometric dissolved oxygen sensor  

Microsoft Academic Search

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

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



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 170°C 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 170°C. 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



Use of iron salts to control dissolved sulfide in trunk sewers  

SciTech Connect

Sewer headspace H{sub 2}S reduction by precipitating dissolved sulfide in wastewater was investigated using iron salt (FeCl{sub 3} and FeCl{sub 2}). Full-scale experiments were conducted in a 40-km (25 mi) sewer with an average flow of 8.7 m{sup 3}/s (200 mgd). Results were sensitive to total Fe dosages and Fe(III)/Fe(II) blend ratios injected. A concentration of 16 mg/L total Fe and a blend ratio of 1.9:1 [Fe(III):Fe(II)] reduced dissolved sulfide levels by 97%. Total sulfide and headspace H{sub 2}S were reduced by 63% and 79%, respectively. Liquid and gas-phase sulfide reductions were largely due to the effective precipitation of sulfide with Fe(III) and Fe(II) and the limited volatilization of H{sub 2}S, respectively. Oxidation of sulfide in the presence of Fe(II) and minute amounts of O{sub 2} may have occurred. A combination of Fe(III) and Fe(II) proved more effective than either salt alone. By using excess Fe(III), dissolved sulfide can be reduced to undetectable levels. No specific relation between the concentration of Fe or Fe(III)/Fe(II) blend ratio and sewer crown pH was inferred. Iron salts may retard crown corrosion rates by precipitating free sulfide and reducing its release to the sewer headspace as H{sub 2}S. A mechanism to inhibit certain responsible bacteria was not established in the 40-km (25 mi) sewer.

Padival, N.A.; Kimbell, W.A. [County Sanitation District of Los Angeles County, Whittier, CA (United States); Redner, J.A. [County Sanitation District of Los Angeles County, Compton, CA (United States)



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

Microsoft Academic Search

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

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



An Approximate Solution for Ph/Ph/1 and Ph/Ph/1/N Queues  

E-print Network

An Approximate Solution for Ph/Ph/1 and Ph/Ph/1/N Queues Alexandre Brandwajn Baskin School approximation to assess the steady-state probabilities of the number of customers in Ph/Ph/1 and Ph/Ph/1/N for the Ph/Ph/1/N queue. The phase-type distributions considered are assumed to be acyclic. Our method

Begin, Thomas



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...


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

Microsoft Academic Search

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

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



The distribution and stabilisation of dissolved Fe in deep-sea hydrothermal plumes  

Microsoft Academic Search

We have conducted a study of hydrothermal plumes overlying the Mid-Atlantic Ridge near 5° S to investigate whether there is a significant export flux of dissolved Fe from hydrothermal venting to the oceans. Our study combined measurements of plume-height Fe concentrations from a series of 6 CTD stations together with studies of dissolved Fe speciation in a subset of those

Sarah A. Bennett; Eric P. Achterberg; Douglas P. Connelly; Peter J. Statham; Gary R. Fones; Christopher R. German




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



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

NASA Astrophysics Data System (ADS)

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

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



Photochemical flocculation of terrestrial dissolved organic matter and iron  

NASA Astrophysics Data System (ADS)

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

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



Uranium Isotope Fractionation during Oxidation of Dissolved U(iv) and Synthetic Solid UO2  

NASA Astrophysics Data System (ADS)

U isotopes (238U/235U) show promise as a tool for environmental monitoring of U contamination as well as a proxy for paleo-redox conditions. However, the isotopic fractionation mechanisms of U are still poorly understood. In groundwater systems, U(VI), a mobile contaminant, can be reduced to immobile U(IV) and thus remediated. Previous work shows that 238U/235U of the remaining U(VI) changes with the extent of reduction. Therefore, U(VI) isotope composition in groundwater can potentially be used to detect and perhaps quantify the extent of reduction. However, knowing if isotopic fractionation occurs during U(IV) oxidation is equally important. First, the reduced U(IV) (either solid or as dissolved organic complexes) potentially can be reoxidized to U(VI). If isotope fractionation occurs during oxidation, it would complicate the use of U isotope composition as a monitoring technique. Further, in natural weathering processes, U(IV) minerals are oxidized to form dissolved U(VI), which is carried to rivers and eventually to the ocean and deposited in marine sediments. The weathering cycle is thus sensitive to redox conditions, meaning the sedimentary U isotope record may serve as a paleoredox indicator, provided U isotope fractionation during oxidation and reduction are well known. We conducted experiments oxidizing 2 different U(IV) species by O2 and measuring isotopic fractionation factors. In one experiment, dissolved U(IV) in 0.1 N HCl (pH 1) was oxidized by entrained air. As oxidation proceeds at pH 1, the remaining dissolved U(IV) becomes progressively enriched in 238U in a linear trend, while the product U(VI) paralleled, but was offset to 1.0‰ lighter in 238U/235U. This linear progression of both remaining reactant and product suggests equilibrium fractionation during oxidation of dissolved U(IV) by O2. A second experiment oxidized synthetic, solid UO2 (in 20 mM NaHCO3, pH 7) with entrained air. The oxidative fractionation is very weak in this case with product U(VI) ~0.1‰ heavier than the remaining UO2. We attribute the lack of strong fractionation during oxidation of solid UO2 to a 'rind effect', where the surface layer must be completely oxidized before the next layer is exposed to oxidant. Hence, nearly complete, congruent conversion of each layer of U(IV) to U(VI) results in minimal isotope fractionation. A small amount of transient fractionation probably occurs initially, but this is quickly negated as the surface becomes isotopically fractionated. Interestingly, our measured ~0.1‰ U isotope fractionation during oxidation of solid U(IV) agrees with the natural observation that 238U/235U ratios in river water (mainly U(VI)) are ~0.1‰ greater than those in fresh continental rocks (primarily U(IV) minerals). Application of these results to natural settings should be done with caution, however. Oxidation of natural uraninite in continental rocks is a much slower process. If the U(VI) product and the U(IV) reactant remain in contact for long periods of time (e.g., months), they may evolve toward isotopic equilibrium. Measurements of 238U/235U in various natural weathering environments should be undertaken to examine this idea.

Wang, X.; Johnson, T. M.; Lundstrom, C. C.



Dissolved Oxygen and Biochemical Oxygen Demand  

NSDL National Science Digital Library

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

Agency, U. S.



E-print Network

_____________________________________________________ 168 Effects of filtering and centrifuging'______________________________ 168 Variations______________________________________ 183 Description of sampling device ~ ______________________________ 183 #12;EFFECT OF DISSOLVED


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

NASA Astrophysics Data System (ADS)

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

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



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.



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



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.



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



Hydrolysis of Naptalam and Structurally Related Amides: Inhibition by Dissolved Metal Ions and Metal (Hydr)Oxide Surfaces  

E-print Network

Hydrolysis of Naptalam and Structurally Related Amides: Inhibition by Dissolved Metal Ions hydrolysis between pH 3.6 and pH 6.5. Metal ion-naptalam complex formation is important since additionOOH inhibit naptalam hydrolysis to a lesser degree; inhibition is proportional to the extent of naptalam

Huang, Ching-Hua


Ph.D. Assessment Form Student Name  

E-print Network

Ph.D. Assessment Form Student Name: Major Advisor: Date: Outcome 1: Graduates will be able to successfully design and conduct original research in their specialty areas. Criterion: Ph.D. candidates related disciplinary areas. Criterion: Ph.D. students will pass their initial preliminary examination


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


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

Rahman, Safiur; Gagnon, Graham A



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.



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)



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


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



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.



Fast dissolving paracetamol/caffeine nanofibers prepared by electrospinning.  


A series of polyvinylpyrrolidone fibers loaded with paracetamol (PCM) and caffeine (CAF) was fabricated by electrospinning and explored as potential oral fast-dissolving films. The fibers take the form of uniform cylinders with smooth surfaces, and contain the drugs in the amorphous form. Drug-polymer intermolecular interactions were evidenced by infrared spectroscopy and molecular modeling. The properties of the fiber mats were found to be highly appropriate for the preparation of oral fast dissolving films: their thickness is around 120-130 ?m, and the pH after dissolution in deionized water lies in the range of 6.7-7.2. Except at the highest drug loading, the folding endurance of the fibers was found to be >20 times. A flavoring agent can easily be incorporated into the formulation. The fiber mats are all seen to disintegrate completely within 0.5s when added to simulated saliva solution. They release their drug cargo within around 150s in a dissolution test, and to undergo much more rapid dissolution than is seen for the pure drugs. The data reported herein clearly demonstrate that electrospun PCM/CAF fibers comprise excellent candidates for oral fast-dissolving films, which could be particularly useful for children and patients with swallowing difficulties. PMID:25455779

Illangakoon, U Eranka; Gill, Hardyal; Shearman, Gemma C; Parhizkar, Maryam; Mahalingam, Sunthar; Chatterton, Nicholas P; Williams, Gareth R



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.


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

PubMed Central

As the atmospheric CO2 concentration rises, more CO2 will dissolve in the oceans, leading to a reduction in pH. Effects of ocean acidification on bacterial communities have mainly been studied in biologically complex systems, in which indirect effects, mediated through food web interactions, come into play. These approaches come close to nature but suffer from low replication and neglect seasonality. To comprehensively investigate direct pH effects, we conducted highly-replicated laboratory acidification experiments with the natural bacterial community from Helgoland Roads (North Sea). Seasonal variability was accounted for by repeating the experiment four times (spring, summer, autumn, winter). Three dilution approaches were used to select for different ecological strategies, i.e. fast-growing or low-nutrient adapted bacteria. The pH levels investigated were in situ seawater pH (8.15–8.22), pH 7.82 and pH 7.67, representing the present-day situation and two acidification scenarios projected for the North Sea for the year 2100. In all seasons, both automated ribosomal intergenic spacer analysis and 16S ribosomal amplicon pyrosequencing revealed pH-dependent community shifts for two of the dilution approaches. Bacteria susceptible to changes in pH were different members of Gammaproteobacteria, Flavobacteriaceae, Rhodobacteraceae, Campylobacteraceae and further less abundant groups. Their specific response to reduced pH was often context-dependent. Bacterial abundance was not influenced by pH. Our findings suggest that already moderate changes in pH have the potential to cause compositional shifts, depending on the community assembly and environmental factors. By identifying pH-susceptible groups, this study provides insights for more directed, in-depth community analyses in large-scale and long-term experiments. PMID:23071704

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



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


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

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



pH dependent dissolution of sediment aluminum in six Danish lakes treated with aluminum.  


The possible pH dependent dissolution of aluminum hydroxides (Al(OH)(3)) from lake sediments was studied in six lakes previously treated with Al to bind excess phosphorus (P). Surface sediment was suspended for 2 h in lake water of pH 7.5, 8.5, or 9.5 with resulting stepwise increments in dissolved Al observed in all lakes. The amount of dissolved Al increased proportional to the sediment content of Al(OH)(3) as quantified by a sequential extraction technique. Up to 24% of the sediment Al(OH)(3) could dissolve within 2 h at pH 9.5 and a portion of sediment P was dissolved concomitantly. Lowering pH to 7 caused 30-100% of the dissolved Al to precipitate again after 24 h. Re-precipitation of mobilized P varied from 50% to more than 100%. A test with untreated sediment showed the same proportionality which means that also indigenous Al(OH)(3) can dissolve frequently in lakes with high pH water. Release rates of dissolved Al from intact sediment cores at the same three pH values was measured in three of the lakes, and showed increased Al release rates at pH 8.5 in one of the lakes and 9.5 in two of the lakes. Our study demonstrates a risk of dissolution of sediment Al(OH)(3) to form aluminate in shallow lakes, where resuspension and high pH in the water occurs frequently. In the worst case dissolved Al may reach toxic levels in lakes treated by Al but also the concomitant release of P and the possible loss of dissolved Al to downstream ecosystems are negative effects that may occur already at more modest dissolution of Al(OH)(3) and Al-bound P. PMID:23273857

Reitzel, Kasper; Jensen, Henning S; Egemose, Sara



Spatial distribution of soils determines export of nitrogen and dissolved organic carbon from an intensively managed agricultural landscape  

NASA Astrophysics Data System (ADS)

The surrounding landscape of a stream has crucial impacts on the aquatic environment. This study pictures the hydro-biogeochemical situation of the Tyrebækken creek catchment in central Jutland, Denmark. The intensively managed agricultural landscape is dominated by rotational croplands. The small catchment mainly consist of sandy soil types besides organic soils along the streams. The aim of the study was to characterise the relative influence of soil type and land use on stream water quality. Nine snapshot sampling campaigns were undertaken during the growing season of 2009. Total dissolved nitrogen (TDN), nitrate (NO3-), ammonium nitrogen and dissolved organic carbon (DOC) concentrations were measured, and dissolved organic nitrogen (DON) was calculated for each grabbed sample. Electrical conductivity, pH and flow velocity were measured during sampling. Statistical analyses showed significant differences between the northern, southern and converged stream parts, especially for NO3- concentrations with average values between 1.4 mg N l-1 and 9.6 mg N l-1. Furthermore, throughout the sampling period DON concentrations increased to 2.8 mg N l-1 in the northern stream contributing up to 81% to TDN. Multiple-linear regression analyses performed between chemical data and landscape characteristics showed a significant negative influence of organic soils on instream N concentrations and corresponding losses in spite of their overall minor share of the agricultural land (12.9%). On the other hand, organic soil frequency was positively correlated to the corresponding DOC concentrations. Croplands also had a significant influence but with weaker correlations. For our case study we conclude that the fractions of coarse textured and organic soils have a major influence on N and DOC export in this intensively used landscape. Meanwhile, the contribution of DON to the total N losses was substantial.

Wohlfart, T.; Exbrayat, J.-F.; Schelde, K.; Christen, B.; Dalgaard, T.; Frede, H.-G.; Breuer, L.



Impact of dissolved silica on arsenite removal by nano-particulate FeS and FeS-coated sand.  


This work evaluated the inhibitory effect of dissolved silica on arsenite adsorption to nanoparticulate FeS (NP-FeS) or mackinawite and FeS-coated sand (CS-FeS) sorbents. Arsenite retention by the NP-FeS solid was not affected by dissolved silicate over a wide range in pH, in contrast to the known inhibitory effect of dissolved silica on As(III) uptake by Fe-(hydr)oxide systems. However, some inhibition was observed in CS-FeS system at pH 9. This latter result is attributed to the co-existence of both FeS and small amounts of Fe-(hydr)oxide phases on the sand surface. Given the ubiquitous presence of dissolved Si in groundwater, FeS-based sorbents may have an advantage for As retention compared to those based on Fe-(hydr)oxides in reducing subsurface environments. PMID:23538091

Han, Young-Soo; Demond, Avery H; Hayes, Kim F



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))



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.



Dissolved Oxygen Data for Coos Estuary (Oregon)  

EPA Science Inventory

The purpose of this product is the transmittal of dissolved oxygen data collected in the Coos Estuary, Oregon to Ms. Molly O'Neill (University of Oregon), for use in her studies on the factors influencing spatial and temporal patterns in dissolved oxygen in this estuary. These d...


Dissolved organic matter fluorescence as a water-flow tracer in the tropical wetland of Pantanal of Nhecolândia, Brazil  

Microsoft Academic Search

The Nhecolândia is a sub-region of the Brazilian Pantanal wetland, where saline and freshwater lakes coexist in close proximity. Measurements of dissolved organic carbon (DOC) content and analysis of fluorescence excitation–emission matrices (EEM) were conducted in an effort to characterize spatial variability in concentration and source of dissolved organic matter (DOM) and to further understand the hydrochemical functioning of this

Mélody Mariot; Yves Dudal; Sônia Furian; Arnaldo Sakamoto; Vincent Vallès; Monique Fort; Laurent Barbiero



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 ...


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



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)




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...


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



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



Modelling of dissolved oxygen content using artificial neural networks: Danube River, North Serbia, case study.  


The aims of this study are to create an artificial neural network (ANN) model using non-specific water quality parameters and to examine the accuracy of three different ANN architectures: General Regression Neural Network (GRNN), Backpropagation Neural Network (BPNN) and Recurrent Neural Network (RNN), for prediction of dissolved oxygen (DO) concentration in the Danube River. The neural network model has been developed using measured data collected from the Bezdan monitoring station on the Danube River. The input variables used for the ANN model are water flow, temperature, pH and electrical conductivity. The model was trained and validated using available data from 2004 to 2008 and tested using the data from 2009. The order of performance for the created architectures based on their comparison with the test data is RNN > GRNN > BPNN. The ANN results are compared with multiple linear regression (MLR) model using multiple statistical indicators. The comparison of the RNN model with the MLR model indicates that the RNN model performs much better, since all predictions of the RNN model for the test data were within the error of less than ± 10 %. In case of the MLR, only 55 % of predictions were within the error of less than ± 10 %. The developed RNN model can be used as a tool for the prediction of DO in river waters. PMID:23764983

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



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)



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

SciTech Connect

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

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



Control of dissolved Al distributions in marine sediments by clay reconstitution reactions: Experimental evidence leading to a unified theory  

NASA Astrophysics Data System (ADS)

A set of sediment "resuspension" experiments was designed to test various aspects of previously hypothesized clay reconstitution reactions in nearshore sediments. Aliquots of wet sediment of approximately equal weight from Flax Pond, Long Island Sound were suspended in stirred and aerated, high salinity solutions having variable adjusted initial dissolved Si concentrations but otherwise nearly identical properties. Dissolved Al and Si and the water pH were monitored over the course of three days. Dissolved Si was removed from solution in the high initial Si (325 and 650 ?M) containers, while little change in Si concentration was observed in a "blank" and 0 Si-spike container. Short-term dissolved Al production in the experiments suggests that clay dissolution is important in these sediments. Long-term dissolved Al behavior agrees fairly well with quantitative predictions based upon previous studies of nearshore sediments, where authigenic clays were believed to cause observed inverse relationships between dissolved Al and Si. The unambiguous results give strong evidence that inverse Al-Si relations in dissolved Fe-poor sediments are a direct result of mineral precipitation, rather than being due to some fortuitous combination of unrelated reactions affecting Al and Si. The Si/Al composition of authigenic clay precipitates in marine sediments probably varies directly with the dissolved Si content of contacting waters. This indicates that a combination of "weathering" and "reverse weathering" of minerals may affect Si distributions, and provides a theoretical link between these two sets of previously suggested mechanisms for clay reconstitution in sediments.

Mackin, James E.



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

NSDL National Science Digital Library

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


Effects of dissolved oxygen concentration on biodegradation of 2,4-dichlorophenoxyacetic acid.  


Batch experiments were conducted to examine the effects of dissolved oxygen concentration on the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) by an enrichment culture of 2,4-D-utilizing bacteria. A modified Monod equation was found to describe the relationship between the specific growth rate and the concentrations of both the organic substrate and dissolved oxygen. Values for the maximum specific growth rate, yield, and Monod coefficient for growth on 2,4-D were 0.09 h-1, 0.14 g/g, and 0.6 mg/liter, respectively. The half-saturation constant for dissolved oxygen was estimated to be 1.2 mg/liter. These results suggest that dissolved oxygen concentrations below 1 mg/liter may be rate limiting for the biodegradation of chlorinated aromatic compounds such as 2,4-D, which have a requirement for molecular oxygen as a cosubstrate for metabolism. PMID:3729394

Shaler, T A; Klecka, G M



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

NASA Astrophysics Data System (ADS)

This study presents uranium and thorium concentrations and activity ratios for all riverine phases (bedload, suspended load, dissolved load and colloids) from basaltic terrains in Iceland and the Azores. Small basaltic islands, such as these, are thought to account for ~ 25% of CO2 consumed by global silicate weathering, and for ~ 45% of the flux of suspended material to the oceans. These data indicate that [U] and [Th] in the dissolved and colloidal fractions are strongly controlled by pH, and to a much lesser extent by levels of dissolved organic carbon (which are low in these environments). At high pH, basalt glass dissolution is enhanced, and secondary mineral formation (e.g. Fe-oxyhydroxides and allophane) is suppressed, resulting in high dissolved [U], and low colloidal [U] and [Th], indicating a direct chemical weathering control on elemental abundances. When the dissolved (234U/238U) activity ratio is >~1.3 (i.e. when physical weathering, groundwater contribution or soil formation are high), there is little isotope exchange between dissolved and colloidal fractions. At lower activity ratios, the dissolved load and colloids have indistinguishable activity ratios, suggesting that when chemical weathering rates are high, secondary clay formation is also high, and colloids rapidly adsorb dissolved U. Many of the suspended sediment samples have (234U/238U) activity ratios of > 1, which suggests that uptake of U onto the suspended load is important. Identical (230Th/232Th) in suspended, dissolved and colloidal samples suggests that Th, like U, is exchanged or sorbed rapidly between all riverine phases. This particle-reactivity, combined with poorly constrained contributions from groundwater and hydrothermal water, and short-term variations in input to soils (volcanic and glacial), suggests that U-series nuclides in riverine material from such basaltic terrains are unlikely to reflect steady state erosion processes.

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



Formulation and evaluation of aceclofenac mouth-dissolving tablet.  


Aceclofenac has been shown to have potent analgesic and anti-inflammatory activities similar to indomethacin and diclofenac, and due to its preferential Cox-2 blockade, it has a better safety than conventional Non steroidal anti-inflammatory drug (NSAIDs) with respect to adverse effect on gastrointestinal and cardiovascular systems. Aceclofenac is superior from other NSAIDs as it has selectivity for Cox-2, a beneficial Cox inhibitor is well tolerated, has better Gastrointestinal (GI) tolerability and improved cardiovascular safety when compared with other selective Cox-2 inhibitor. To provide the patient with the most convenient mode of administration, there is need to develop a fast-disintegrating dosage form, particularly one that disintegrates and dissolves/disperses in saliva and can be administered without water, anywhere, any time. Such tablets are also called as "melt in mouth tablet." Direct compression, freeze drying, sublimation, spray drying, tablet molding, disintegrant addition, and use of sugar-based excipients are technologies available for mouth-dissolving tablet. Mouth-dissolving tablets of aceclofenac were prepared with two different techniques, wet granulation and direct compression, in which different formulations were prepared with varying concentration of excipients. These tablets were evaluated for their friability, hardness, wetting time, and disintegration time; the drug release profile was studied in buffer Phosphate buffered Saline (PBS) pH 7.4. Direct compression batch C3 gave far better dissolution than the wet granulation Batch F2, which released only 75.37% drug, and C3, which released 89.69% drug in 90 minutes. PMID:22171305

Solanki, Shailendra Singh; Dahima, Rashmi



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 (25.5 ± 12.5%) 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



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.


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


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

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



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)



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,


Influence of Calcite and Dissolved Calcium on Uranium(VI) Sorption to a Hanford Subsurface Sediment  

Microsoft Academic Search

The influence of calcite and dissolved calcium on U(VI) adsorption was investigated using a calcite-containing sandy silt\\/clay sediment from the U. S. Department of Energy Hanford site. U(VI) adsorption to sediment, treated sediment, and sediment size fractions was studied in solutions that both had and had not been preequilibrated with calcite, at initial [U(VI)] - 10-7-10-5 mol\\/L and final pH

Wenming Dong; William P. Ball; Chongxuan Liu; Zheming Wang; Alan T. Stone; Jing Bai; John M. Zachara



Electrochemical generation of hydrogen peroxide from dissolved oxygen in acidic solutions  

Microsoft Academic Search

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

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



Mobilization of actinides by dissolved organic compounds at the Nevada Test Site  

Microsoft Academic Search

The effect of dissolved organic matter (DOM) on Am(III), Pu(IV), Np(V), and U(VI) sorption was investigated with natural water (pH ?8) and zeolitized tuff samples collected from the Rainier Mesa tunnel system, Nevada Test Site, where the USA detonated underground nuclear tests prior to 1992. Perched vadose zone water at Rainier Mesa has high levels of DOM as a result

Pihong Zhao; Mavrik Zavarin; Roald N. Leif; Brian A. Powell; Michael J. Singleton; Rachel E. Lindvall; Annie B. Kersting




SciTech Connect

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

Williamson, B.



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

USGS Publications Warehouse

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

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



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

PubMed Central

The effect of dissolved oxygen concentrations on the behavior of Serratia marcescens and on yields of asparaginase and prodigiosin produced in shaken cultures and in a 55-liter stainless-steel fermentor was studied. A range of oxygen transfer rates was obtained in 500-ml Erlenmeyer flasks by using internal, stainless-steel baffles and by varying the volume of medium per flask, and in the fermentor by high speed agitation (375 rev/min) or low rates of aeration (1.5 volumes of air per volume of broth per min), or both. Dissolved oxygen levels in the fermentation medium were measured with a membrane-type electrode. Peak yields of asparaginase were obtained in unbaffled flasks (3.0 to 3.8 IU/ml) and in the fermentor (2.7 IU/ml) when the level of dissolved oxygen in the culture medium reached zero. A low rate of oxygen transfer was accomplished by limited aeration. Production of prodigiosin required a supply of dissolved oxygen that was obtainable in baffled flasks with a high rate of oxygen transfer and in the fermentor with a combination of high-speed agitation and low-rate aeration. The fermentation proceeded at a more rapid rate and changes in pH and cell populations were accelerated by maintaining high levels of dissolved oxygen in the growth medium. PMID:4912278

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



Dissolved carbon dynamics in large boreal rivers from eastern Canada following their impoundment  

NASA Astrophysics Data System (ADS)

The carbon cycling in Canadian boreal environments is the focus of a growing number of investigations mainly because of the importance of hydropower and its potential in the area. Here, we document the behaviour of dissolved inorganic and organic carbon as well as particulate organic carbon (DIC-DOC-POC henceforth) in 5 impounded and 2 pristine river systems (respectively: La Grande 3400 m 3s-1, Eastmain 990 m3s-1, St. Lawrence 12 100 m3s-1, Ottawa 1950 m3s-1, Nelson 2370 m3s-1; Great Whales 680 m3s-1 and Koksoak 1895 m3s-1) river systems. These major rivers were sampled monthly at their outlet for one year except at the St. Lawrence River that has been sampled since June of 1997 on a bi-weekly basis. Complementary synoptic surveys were undertaken in August 2008 on the La Grande and Great Whales Rivers. When sampling, water temperature, pH, alkalinity and specific conductivity were measured. Samples were collected for the analysis of i) major ions concentrations; ii) ?13C and concentration of DIC, DOC and POC); iii) ?18O and ?2H of the water molecule; and iv) U series and Sr isotopes. In all the sampled river systems, POC concentrations were at least an order of magnitude smaller than the dissolved forms. Rivers draining carbonates bedrocks (St.Lawrence and Nelson Rivers) present higher concentrations and ?13C-DIC values linked to carbonate dissolution in soils. Conversely, rivers draining silicate-rich watersheds present lower ?13C- DIC values linked to the production of an isotopically light CO2 through oxidation of organic matter in soils and that of soil-derived DOC along river courses. However, isotopic composition of DIC in impounded rivers draining silicate catchments indicate significant CO2 degassing and some isotopic exchange with atmospheric CO2 in reservoirs. A relatively strong relationship is observed between pCO2 and ?13C-DIC across the studied river systems suggesting a continuum between the production of CO2 through DOM oxidation and CO2 degassing. A relationship is also observed between ?13C-DIC values and [DOC]/[DIC] suggesting here that the more DOC is available for degradation, the more it will be oxidized to dissolved CO2. A striking feature of boreal systems is the homogeneity of the isotopic composition of its DOC (-27.4±0.2‰ vs. V-PDB). Moreover, C/N ratios and 14C activities >100% (vs. "modern" carbon) of bulk dissolved organic matter (MOD) measured in the impounded La Grande River also lead to conclude that that this DOC, mostly fresh and young, has a low overall residence time in the catchment basin.

Helie, J.; Rosa, E.; Lalonde, A.; Hillaire-Marcel, C.



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



Siderophore adsorption to and dissolution of kaolinite at pH 3 to 7 and 22°C  

NASA Astrophysics Data System (ADS)

Siderophores are Fe(III)-specific ligands produced by many aerobic microorganisms under conditions of iron stress. This study examined adsorption of the commercial trihydroxamate siderophore, desferrioxamine B (DFO-B), to an iron-containing kaolinite (0.1 bulk wt.% Fe) and examined DFO-B effects on initial kaolinite dissolution and iron release rates. Adsorption experiments were conducted at pH 3 to 8 in 0.01-M NaClO 4 in the dark and at 22°C; batch initial dissolution experiments were conducted to 96 h. The adsorption envelope (i.e., adsorption as a function of pH) of DFO-B on kaolinite was consistent with cation-like behavior, with adsorption increasing above kaolinite's pH pznpc of 4.9. DFO-B enhanced aluminum release from kaolinite at pH 3 to 7, relative to HNO 3, which is consistent with the ligand's high binding affinity for Al. Correlation between DFO-B adsorption and aluminum release suggested a surface-controlled, ligand-promoted dissolution mechanism. DFO-B had no effect relative to HNO 3 on silicon release at pH 3 and 5, but moderately enhanced silicon release at pH 7. DFO-B enhanced iron release from kaolinite, with dissolved iron concentrations in the 10-ppb range at 96-h reaction time. These results show that kaolinite may serve as a source of iron to aerobic microorganisms in iron-limited conditions and that siderophores may affect kaolinite dissolution and iron content.

Rosenberg, Dana R.; Maurice, Patricia A.



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



Process for coal liquefaction in staged dissolvers  


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

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



A Quantitative Evaluation of Dissolved Oxygen Instrumentation  

NASA Technical Reports Server (NTRS)

The implications of the presence of dissolved oxygen in water are discussed in terms of its deleterious or beneficial effects, depending on the functional consequences to those affected, e.g., the industrialist, the oceanographer, and the ecologist. The paper is devoted primarily to an examination of the performance of five commercially available dissolved oxygen meters. The design of each is briefly reviewed and ease or difficulty of use in the field described. Specifically, the evaluation program treated a number of parameters and user considerations including an initial check and trial calibration for each instrument and a discussion of the measurement methodology employed. Detailed test results are given relating to the effects of primary power variation, water-flow sensitivity, response time, relative accuracy of dissolved-oxygen readout, temperature accuracy (for those instruments which included this feature), error and repeatability, stability, pressure and other environmental effects, and test results obtained in the field. Overall instrument performance is summarized comparatively by chart.

Pijanowski, Barbara S.



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.



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

NASA Astrophysics Data System (ADS)

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

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



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

NASA Astrophysics Data System (ADS)

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

Frank, Stefan; Tiemeyer, Bärbel; Freibauer, Annette



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

USGS Publications Warehouse

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

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



Evaluation of planning alternatives for maintaining desirable dissolved-oxygen concentrations in the Willamette River, Oregon  

USGS Publications Warehouse

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

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



Effects of iron on optical properties of dissolved organic matter.  


Iron is a source of interference in the spectroscopic analysis of dissolved organic matter (DOM); however, its effects on commonly employed ultraviolet and visible (UV-vis) light adsorption and fluorescence measurements are poorly defined. Here, we describe the effects of iron(II) and iron(III) on the UV-vis absorption and fluorescence of solutions containing two DOM fractions and two surface water samples. In each case, regardless of DOM composition, UV-vis absorption increased linearly with increasing iron(III). Correction factors were derived using iron(III) absorption coefficients determined at wavelengths commonly used to characterize DOM. Iron(III) addition increased specific UV absorbances (SUVA) and decreased the absorption ratios (E2:E3) and spectral slope ratios (SR) of DOM samples. Both iron(II) and iron(III) quenched DOM fluorescence at pH 6.7. The degree and region of fluorescence quenching varied with the iron:DOC concentration ratio, DOM composition, and pH. Regions of the fluorescence spectra associated with greater DOM conjugation were more susceptible to iron quenching, and DOM fluorescence indices were sensitive to the presence of both forms of iron. Analyses of the excitation-emission matrices using a 7- and 13-component parallel factor analysis (PARAFAC) model showed low PARAFAC sensitivity to iron addition. PMID:25084347

Poulin, Brett A; Ryan, Joseph N; Aiken, George R




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...


Importance of Dissolved Organic Nitrogen to Water Quality in Narragansett Bay  

EPA Science Inventory

This preliminary analysis of the importance of the dissolved organic nitrogen (DON) pool in Narragansett Bay is being conducted as part of a five-year study of Narragansett Bay and its watershed. This larger study includes water quality and ecological modeling components that foc...



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...



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....


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)



Lithium ion conducting ionic electrolytes  


A liquid, predominantly lithium-conducting, ionic electrolyte is described which has exceptionally high conductivity at temperatures of 100 C or lower, including room temperature. It comprises molten lithium salts or salt mixtures in which a small amount of an anionic polymer lithium salt is dissolved to stabilize the liquid against recrystallization. Further, a liquid ionic electrolyte which has been rubberized by addition of an extra proportion of anionic polymer, and which has good chemical and electrochemical stability, is described. This presents an attractive alternative to conventional salt-in-polymer electrolytes which are not cationic conductors. 4 figs.

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




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...



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 ...


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



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


We have studied the impact of dissolved aluminum on interfacial properties of two aluminum bearing minerals, corundum and kaolinite. The effect of intentionally adding dissolved aluminum on electrokinetic potential of basal plane surfaces of sapphire was studied by streaming potential measurements as a function of pH and was complemented by a second harmonic generation (SHG) study at pH 6. The electrokinetic data show a similar trend as the SHG data, suggesting that the SHG electric field correlates to zeta-potential. A comparable study was carried out on kaolinite particles. In this case electrophoretic mobility was measured as a function of pH. In both systems the addition of dissolved aluminum caused significant changes in the charging behavior. The isoelectric point consistently shifted to higher pH values, the extent of the shift depending on the amount of aluminum present or added. The experimental results imply that published isoelectric points of clay minerals may have been affected by this phenomenon. The presence of dissolved aluminum in experimental studies may be caused by particular pre-treatment methods (such as washing in acids and subsequent adsorption of dissolved aluminum) or even simply by starting a series of measurements from extreme pH (causing dissolution), and subsequently varying the pH in the very same batch. This results in interactions of dissolved aluminum with the target surface. A possible interpretation of the experimental results could be that at low aluminum concentrations adatoms of aluminum (we will refer to adsorbed mineral constituents as adatoms) can form at the sapphire basal plane, which can be rather easily removed. Simultaneously, once the surface has been exposed to sufficiently high aluminum concentration, a visible change of the surface is seen by AFM which is attributed to a surface precipitate that cannot be removed under the conditions employed in the current study. In conclusion, whenever pre-treatment or the starting point of an experiment favor the dissolution of aluminum, dissolved Al may remain in the experimental system and interact with the target surfaces. The systems are then no longer pristine and points of zero charge or sorption data are those of aluminum-bearing systems. PMID:25045321

Lützenkirchen, Johannes; Abdelmonem, Ahmed; Weerasooriya, Rohan; Heberling, Frank; Metz, Volker; Marsac, Remi



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




Microsoft Academic Search

Electroflotation studies on sphalerite fine particles, conducted under careful pH control using buffer electrolytes, reveal that for either H2 or 02 electrolytic gases there exists an optimum pH range at which electroflotation is most effective. This can be explained by the observed dependence of electrolytic gas bubble size on the pH of the electrolyte.




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



Fractionation of Dissolved Solutes and Chromophoric Dissolved Organic Matter During Experimental Sea Ice Formation.  

E-print Network

In the past decade there has been an overall decrease in Arctic Ocean sea ice cover. Changes to the ice cover have important consequences for organic carbon cycling, especially over the continental shelves. When sea ice is formed, dissolved organic...

Smith, Stephanie 1990-



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



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, Stéphane; 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



Updated determination of particulate and dissolved thorium-234  

NASA Astrophysics Data System (ADS)

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

Fleer, Alan P.


Possible method for dissolved organic carbon speciation in forest soils  

NASA Astrophysics Data System (ADS)

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

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



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



The relationship of dissolved Pb to some dissolved trace metals (Al, Cr, Mn, and Zn) and to dissolved nitrate and phosphate in a freshwater aquatic system in Mauritius.  


The relationship of some dissolved trace metals (Al, Cr, Mn, Zn, and Pb) with one another and to dissolved phosphate and nitrate in a freshwater aquatic system at Flic en Flac and Grand River North West (GRNW) in Mauritius (1850 km2, 20 degrees S and 57 degrees E, Western Indian ocean) is reported following trace metal determination using inductively coupled plasma mass spectrometry (ICP-MS). Dissolved Al (<200 ng ml(-1)), Cr (<50 ng ml(-1)), Mn (<50 ng ml(-1)), Zn (< 100 ng ml(-1)), and Pb (<50 ng ml(-1)) upstream, downstream GRNW and in the marshes and rivulet at Flic en Flac were found to be below the recommended EEC maximum admissible concentrations and within the ambient drinking water quality standards in Mauritius. Dissolved Pb was significantly positively correlated to both dissolved Cr and Zn suggesting that the cycling for dissolved Pb is linked to the cycling of both dissolved Cr and Zn along GRNW. The common influential cycling of Pb and Zn was further reinforced as both dissolved Pb and Zn were significantly positively correlated to dissolved phosphate, which suggested a biological role in the cycling of Zn and Pb. The role of biological activity or adsorption to biological systems in Pb cycling along GRNW is further suggested as dissolved Pb was significantly correlated to dissolved nitrate. The apparent absence of the dissolved Al, Cr, and Mn with dissolved nitrate and phosphate could be attributed to factors such as the lower sensitivity of the GRNW to metal uptake during biological activity during the time frame considered. The cycling of dissolved Al and Mn was also not linked to the cycling of Cr, Zn, and Pb as no significant correlation was found along GRNW. PMID:11341289

Ramessur, R T; Parry, S J; Ramjeawon, T




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...


The effect of some dissolved constituents on the redox potential of water  

E-print Network

?Sa ?t the whee meC. 4SSSbseaaea. Rhea, basest, saalS?s 4 shah the eeeye at each each ?SSSsh 'be e?st lesms. CHANGE IN Eh WITH DISSOLVED OXYGEN, KEEPING THE pH CONSTANT IO t- LU x 0 CURVE pH D 4J 0 I EO 40 O 0. 5 I 2 3 4 S 6 8 O za 7... 5. 64 5e65 5e76 5. 57 Mjh le56 2e40 3 e 11 3 eV2 4, 26 4. 63 5eV, 7e 53 7~; L. 7 Sodium Chloride ~lotion Coat", iniqg F'eerie Zoo Clnogo af;~x & otanti 1 ~itb C~ ia 0'esolved (ugrgm Coneeatvetioo ~ pH 6o Tom ~ 33e50 33e35 33e2...

Wales, Robert David



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

SciTech Connect

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

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



Dissolving Polymer Microneedle Patches for Influenza Vaccination  

PubMed Central

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

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



Acidogenesis of dairy wastewater at various pH levels  

Microsoft Academic Search

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

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



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.



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



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.



An Introduction to Chemistry: Dissolving Sodium Chloride  

NSDL National Science Digital Library

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

Bishop, Mark



Enzymatic removal of hemicellulose from dissolving pulps  

Microsoft Academic Search

Hemicellulases and an endoglucanase from seven different fungi were assessed for their potential to solubilze mannan and xylan\\u000a from softwood sulfite dissolving pulps. A xylanase from Thermomyces lanuginosus and a mannanase from Sclerotium rolfsii acted\\u000a synergistically on the pulp solubilizing 50% more mannan and 11% more xylan than did the individual enzymes. The addition\\u000a of an endoglucanase further increased both

G. M Gübitz; T. Lischnig; D. Stebbing; J. N. Saddler



Elevated concentrations of formate, acetate and dissolved organic carbon found at the Lost City hydrothermal field  

NASA Astrophysics Data System (ADS)

Fluids from the ultramafic-hosted Lost City hydrothermal field were analyzed for total dissolved organic carbon and dissolved organic acids. Formate (36-158 ?mol/kg) and acetate (1-35 ?mol/kg) concentrations are higher than in other fluids from unsedimented hydrothermal vents, and are a higher ratio of the total dissolved organic carbon than has been found in most marine geothermal systems. Isotopic evidence is consistent with an abiotic formation mechanism for formate, perhaps during serpentinization processes in the sub-surface. Further support comes from previous studies where the abiological formation of low molecular weight organic acids has been shown to be thermodynamically favorable during hydrothermal alteration of olivine, and laboratory studies in which the reduction of carbon dioxide to formate has been confirmed. As the second most prevalent carbon species after methane, formate may be an important substrate to microbial communities in an environment where dissolved inorganic carbon is limited. Acetate is found in locations where sulfate reduction is believed to be important and is likely to be a microbial by-product, formed either directly by autotrophic metabolic activity or indirectly during the fermentative degradation of larger organic molecules. Given the common occurrence of exposed ultramafic rocks and active serpentinization within the worlds ocean basins, the abiotic formation of formate may be an important process supporting life in these high pH environments and may have critical implications to understanding the organic precursors from which life evolved.

Lang, Susan Q.; Butterfield, David A.; Schulte, Mitch; Kelley, Deborah S.; Lilley, Marvin D.



Dissolved organic nitrogen measurement using dialysis pretreatment.  


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

Lee, Wontae; Westerhoff, Paul



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



27 CFR 19.455 - Dissolving of denaturants.  

Code of Federal Regulations, 2010 CFR

...BUREAU, DEPARTMENT OF THE TREASURY LIQUORS DISTILLED SPIRITS PLANTS Denaturing Operations and Manufacture of Articles Denaturation § 19.455 Dissolving of denaturants. Denaturants which are difficult to dissolve in spirits at usual...




EPA Science Inventory

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


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)



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

NASA Astrophysics Data System (ADS)

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

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



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



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


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

Mazzei, Pierluigi; Piccolo, Alessandro



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

ERIC Educational Resources Information Center

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

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



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.



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.



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



Determination of Dissolved Oxygen in the Cryosphere: A Comprehensive  

E-print Network

Determination of Dissolved Oxygen in the Cryosphere: A Comprehensive Laboratory and Field communities, whose function and dynamics are often controlled by the concentrations of dissolved oxygen (DO tests and superior to traditional methods. Introduction Dissolved oxygen (DO) is a key parameter

Fountain, Andrew G.



E-print Network



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



Biogeochemical controls on Diel cycling of stable isotopes of dissolved O2 and dissolved inorganic carbon in the Big Hole River, Montana.  


Rivers with high biological productivity typically show substantial increases in pH and dissolved oxygen (DO) concentration during the day and decreases at night, in response to changes in the relative rates of aquatic photosynthesis and respiration. These changes, coupled with temperature variations, may impart diel (24-h) fluctuations in the concentration of trace metals, nutrients, and other chemical species. A better understanding of diel processes in rivers is needed and will lead to improved methods of data collection for both monitoring and research purposes. Previous studies have used stable isotopes of dissolved oxygen (DO) and dissolved inorganic carbon (DIC) as tracers of geochemical and biological processes in streams, lakes, and marine systems. Although seasonal variation in 6180 of DO in rivers and lakes has been documented, no study has investigated diel changes in this parameter. Here, we demonstrate large (up to 13%o) cycles in delta18O-DO for two late summer sampling periods in the Big Hole River of southwest Montana and illustrate that these changes are correlated to variations in the DO concentration, the C-isotopic composition of DIC, and the primary productivity of the system. The magnitude of the diel cycle in delta18O-DO was greater in August versus September because of the longer photoperiod and warmer water temperatures. This study provides another biogeochemical tool for investigating the O2 and C budgets in rivers and may also be applicable to lake and groundwater systems. PMID:16201639

Parker, Stephen R; Poulson, Simon R; Gammons, Christopher H; DeGrandpre, Michael D



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.



Appropriate Conduct  

ERIC Educational Resources Information Center

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

Di Lullo, Louis



Conduction Activities  

NSDL National Science Digital Library

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



Monday Tuesday Wednesday Thursday Friday PH 1110 PH 1110  

E-print Network

Monday Tuesday Wednesday Thursday Friday PH 1110 PH 1110 Muhammad Muhammad CS 1101 CS 1101 CS 1101 Mairaj Mairaj Mairaj Ph 1111 Ph 1111 PH 1111 Zhen Zhen Zhen CH 1010 CH 1010 Elisabeth Elisabeth MA 1023 MA 1021 MA 1023 MA 1021 Kushi Han Li Murtaza Jeffrey MA 1021 MA 1023 PH 1110 Han Li Murtaza Muhammad

Weekes, Suzanne L.


Decreased structure on dissolving methane in water  

NASA Astrophysics Data System (ADS)

There is a widely held view that hydrophobic entities such as alkanes and alkyl head groups enhance the local structure of water (greater tetrahedrality) when dissolved in it. The idea stems from an early paper by Frank and Evans who speak about ice-like structures forming around hydrophobic entities in solution. Here, we probe directly for the first time the structure of water in a methane-water solution using neutron diffraction with hydrogen isotope substitution. We find no evidence for enhanced water structure. If anything the structure is marginally less tetrahedral than in pure water at the same temperature and pressure.

Buchanan, P.; Aldiwan, N.; Soper, A. K.; Creek, J. L.; Koh, C. A.



Radiothermoluminescence sensitisation by dissolved oxygen in fluoropolymers  

NASA Astrophysics Data System (ADS)

The intensity of radiothermoluminescence (RTL) flashes in polytetrafluoroethylene (PTFE) and tetrafluoroethylene/hexafluoropropylene copolymer (trademark FEP) depending on the oxygen pressure in the outer atmosphere (from 10 -4 to 720 Torr) shows that dissolved oxygen plays an important role in the RTL phenomenon in fluoropolymers. On the basis of the established "pressure" dependence, it is proposed that physically adsorbed oxygen molecules can accumulate in defect regions of the polymer matrix and further interact with active centers that have escaped from the traps during heating of the polymer samples, resulting in RTL flashes. It is concluded that RTL in fluoropolymers may be oxygen-induced chemiluminescence.

Smolyanskii, A. S.; Shelukhov, I. P.; Podsoblyaev, A. P.; Tupikov, V. I.



pH control with silicates minerals for in situ bioremediation of chlorinated solventsfor in situ bioremediation of chlorinated solvents  

E-print Network

conditions inhibit the activity of anaerobic bacteria. Therefore, development of an efficient pH control in groundwater. It relies on ...the activity of specialized bacteria that Organohalide respiration Acidity and hydrogen Anaerobic conditionsResults5 Anaerobic conditions Measurements: pH, ....chloroethenes, dissolved


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


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



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

SciTech Connect

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

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



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

Microsoft Academic Search

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

S. E. Cabaniss; M. S. Shuman



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.



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



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



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

Microsoft Academic Search

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

Kunio Kaiho



pH Scale  

NSDL National Science Digital Library

Test the pH of things like coffee, spit, and soap to determine whether each is acidic, basic, or neutral. Visualize the relative number of hydroxide ions and hydronium ions in solution. Switch between logarithmic and linear scales. Investigate whether changing the volume or diluting with water affects the pH. Or you can design your own liquid!

Simulations, Phet I.; Adams, Wendy; Barbera, Jack; Langdon, Laurie; Loeblein, Patricia; Malley, Chris



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?



Predation on fish larvae by moon jellyfish Aurelia aurita under low dissolved oxygen concentrations  

Microsoft Academic Search

Laboratory experiments were conducted to test the hypothesis that low dissolved oxygen concentrations have the potential to\\u000a enhance the predation rate on fish larvae by moon jellyfish Aurelia aurita which is increasing in abundance in the coastal waters of Japan. Larvae of the red sea bream Pagrus major in four size classes (2.9, 4.1, 6.2 and 8.6 mm in standard

Jun Shoji; Reiji Masuda; Yoh Yamashita; Masaru Tanaka



Analysis of RFSA Campaign No.2 Dissolver Solution for Hg(I) and Hg(II)  

SciTech Connect

TA 2-1083, under which RFSA processing is conducted, calls for a nominal mercuric ion concentration in the dissolver solution of 0.006M with a maximum of 0.01 M. The second RFSA campaign operated according to these guidelines with the initial Hg(II) concentration being 0.0068 M. Part of this study is to ascertain optimum excess Hg(I) for chloride removal.

Holcomb, H.P.



Influence of dissolution media pH and USP1 basket speed on erosion and disintegration characteristics of immediate release metformin hydrochloride tablets.  


Abstract Purpose: To investigate the influence of the pH of the dissolution medium on immediate release 850?mg metformin hydrochloride tablets. Methods: A traditional wet granulation method was used to manufacture metformin hydrochloride tablets with or without a disintegrant. Tablet dissolution was conducted using the USP apparatus I at 100?rpm. Results: In spite of its pH-independent high solubility, metformin hydrochloride tablets dissolved significantly slower in 0.1?N HCl (pH 1.2) and 50?mM pH 4.5 acetate buffer compared with 50?mM pH 6.8 phosphate buffer, the dissolution medium in the USP. Metformin hydrochloride API compressed into a round 1200?mg disk showed a similar trend. When basket rotation speed was increased from 100 to 250?rpm, the dissolution of metformin hydrochloride tablets was similar in all three media. Incorporation of 2% w/w crospovidone in the tablet formulation improved the dissolution although the pH-dependent trend was still evident, but incorporation of 2% w/w croscarmellose sodium resulted in rapid pH-independent tablet dissolution. Conclusion: In absence of a disintegrant in the tablet formulation, the dissolution was governed by the erosion-diffusion process. Even for a highly soluble drug, a super-disintegrant was needed in the formulation to overcome the diffusion layer limitation and change the dissolution mechanism from erosion-diffusion to disintegration. PMID:24621340

Desai, Divyakant; Wong, Benjamin; Huang, Yande; Tang, Dan; Hemenway, Jeffrey; Paruchuri, Srinivasa; Guo, Hang; Hsieh, Daniel; Timmins, Peter




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...


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

PubMed Central

Total dissolved inorganic carbon (?CO2) and aqueous carbon dioxide (H2CO3*) in nutrient solutions may be measured by the injection of small gas or liquid samples (1 microliter to 8 milliliters) into a gas stripping column connected in-line with an infrared gas analyzer. The measurement of ?CO2 in solution requires sample acidification, while H2CO3* and gaseous CO2 are measured without the addition of lactic acid. The standard curve for ?CO2 was linear up to 300 nanomoles CO2. Maximum sensitivity was approximately 300 picomoles. Measurements of H2CO3* were independent of pH. Consequently, ?CO2 and H2CO3* could be used to calculate the pH, HCO3?, and CO32? values of nutrient solutions. Injection and complete analyses required from 0.8 to 2 minutes. PMID:16662962

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



Influence of Calcite and Dissolved Calcium on Uranium(VI) Sorption to a Hanford Subsurface Sediment  

SciTech Connect

The influence of calcite and dissolved calcium on U(VI) adsorption was investigated using a calcite-containing sandy silt/clay sediment from the U. S. Department of Energy Hanford site. U(VI) adsorption to sediment, treated sediment, and sediment size fractions was studied in solutions that both had and had not been preequilibrated with calcite, at initial [U(VI)] - 10-7-10-5 mol/L and final pH - 6.0-10.0. Kinetic and reversibility studies (pH 8.4) showed rapid sorption (30 min), with reasonable reversibility in the 3-day reaction time. Sorption from solutions equilibrated with calcite showed maximum U(VI) adsorption at pH 8.4-0.1. In contrast, calcium-free systems showed the greatest adsorption at pH 6.0-7.2. At pH > 8.4, U(VI) adsorption was identical from calcium-free and calcium-containing solutions. For calcite-presaturated systems, both speciation calculations and laser-induced fluorescence spectroscopic analyses indicated that aqueous U(VI) was increasingly dominated by Ca2UO2(CO3)3 0(aq) at pH<8.4 and that formation of Ca2UO2(CO3)3 0(aq) is what suppresses U(VI) adsorption. Above pH 8.4, aqueous U(VI) speciation was dominated by UO2(CO3)3 4- in all solutions. Finally, results also showed that U(VI) adsorption was additive in regard to size fraction but not in regard to mineral mass: Carbonate minerals may have blocked U(VI) access to surfaces of higher sorption affinity.

Dong, Wenming; Ball, William P.; Liu, Chongxuan; Wang, Zheming; Stone, Alan T.; Bai, Jing; Zachara, John M.



Scattering measurements from a dissolving bubble.  


A laboratory-scale study on acoustic scattering from a single bubble undergoing dissolution in undersaturated fresh water is presented. Several experiments are performed with the acoustic source driven with five-cycle tone bursts, center frequency of 120 kHz, to insonify a single bubble located on axis of the combined beam of the set of transducers. The bubble is placed on a fine nylon thread located in the far field of the transducer set, arranged in bistatic configuration, in a tank filled with undersaturated water. Backscattered waveforms from the bubble target are acquired every few seconds for several hours until the bubble has completely dissolved, and detailed dissolution curves are produced from the acoustic data. The rate of bubble dissolution is calculated using the solution developed by Epstein and Plesset [J. Chem. Phys. 18, 1505-1509 (1950)]. The results of the experiments performed are in agreement with the calculations. PMID:22712899

Kapodistrias, George; Dahl, Peter H



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)



Method for dissolving delta-phase plutonium  

SciTech Connect

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



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.



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



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.



Oxidation of dissolved elemental mercury by thiol compounds under anoxic conditions  

SciTech Connect

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

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



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.



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

Microsoft Academic Search

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

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



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



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

NASA Astrophysics Data System (ADS)

A cupric ion-selective electrode measured free Cu in solutions of Suwannee River fulvic acid (FA) in a series of 30 titrations carried out both at variable and at constant (5.14, 7.00, 8.44) pH. Total Cu varied 0.1-100 ?M, dissolved organic carbon (DOC) 1-10 mg C/l, Ca and Mg 0-10 mM, and ionic strength 0.005-0.1. Copper complexation by FA is first order in DOC for 1-10 mg C/liter, and variable-order in pH. Increasing Ca ++ or Mg ++ from 0 to 10 mM slightly increases Cu ++ activity, while increasing ionic strength from 0.005 to 0.1 significantly increases Cu ++ activity. An empirical N- site model was calibrated using a pooled set of six titrations with varying pH and DOC. Five binding components of varying proton dependence predict Cu binding by FA over a range of pH, DOC and total Cu in two verification tests of the model parameters. Parameters in this and other models tested are only empirical constructs.

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



Experimental investigation and modeling of dissolved organic carbon removal by coagulation from seawater.  


Coagulation removes colloidal matters and dissolved organic carbon (DOC) which can cause irreversible membrane fouling. However, how DOC is removed by coagulant is not well-known. Jar test was used to study the removal of hydrophobic and hydrophilic DOC fractions at various doses (0.5-8.0 mg-Fe(+3) L(-1)) of ferric chloride (FeCl3) and pH (5.0-9.0). Natural organic matter (NOM) in seawater and treated seawater were fractionated by liquid chromatography-organic carbon detector (LC-OCD). Compared to surface water, the removal of DOC in seawater by coagulation was remarkably different. Majority of DOC could be easily removed with very low coagulant dose (<5.0 mg-Fe(+3) L(-1)) and the removal efficiency did not vary with pH, but the DOC composition in treated water had significantly changed. Hydrophobic fraction (HB) was better removed at high pH while hydrophilic fraction (HF) was better removed at low pH. A modified model of Kastl et al. (2004) which assumed that the removal occurred by adsorption of un-dissociated compounds onto ferric hydroxide was formulated and successfully validated against the jar test data. PMID:24095612

Jeong, Sanghyun; Sathasivan, Arumugam; Kastl, George; Shim, Wang Geun; Vigneswaran, Saravanamuthu



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

SciTech Connect

A cupric ion-selective electrode measured free Cu in solutions of Suwannee River fulvic acid (FA) in a series of 30 titrations carried out both at variable and at constant (5.14, 7.00, 8.44) pH. Total Cu varied 0.1-100, dissolved organic carbon (DOC) 1-10 mg C/l, Ca and Mg 0-10 mM, and ionic strength 0.005-0.1. Copper complexation by FA is first order in DOC for 1-10 mg C/liter, and variable-order in pH. Increasing Ca/sup + +/ or Mg/sup + +/ from 0 to 10 mM slightly increases Cu/sup + +/ activity, while increasing ionic strength from 0.005 to 0.1 significantly increases Cu/sup + +/ activity. An empirical N-site model was calibrated using a pooled set of six titrations with varying pH and DOC. Five binding components of varying proton dependence predict Cu binding by FA over a range of pH, DOC and total Cu in two verification tests of the model parameters. Parameters in this and other models tested are only empirical constructs.

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



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.



Dissolved aluminium in the Southern Ocean  

NASA Astrophysics Data System (ADS)

Dissolved aluminium (Al) occurs in a wide range of concentrations in the world oceans. The concentrations of Al in the Southern Ocean are among the lowest ever observed. An all-titanium CTD sampling system makes it possible to study complete deep ocean sections of Al and other trace elements with the same high vertical resolution of 24 depths as normal for traditional CTD/Rosette sampling. Overall, 470 new data points of Al are reported for 22 full depth stations and 24 surface sampling positions along one transect. This transect consisted of 18 stations on the zero meridian proper from 51°57' S until 69°24'S, and 4 stations somewhat to the northeast towards Cape Town from 42°20'S, 09°E to 50°17'S, 01°27'E. The actual concentrations of Al in the Southern Ocean were lower than previously reported. The concentration of Al in the upper 25 m was relatively elevated with an average concentration of 0.71 nM ( n=22; S.D.=0.43 nM), most likely due to atmospheric input by a suggested combination of direct atmospheric (wet and dry) input and indirect atmospheric input via melting sea ice. Below the surface waters there was a distinct Al minimum with an average concentration of 0.33 nM ( n=22; S.D.=0.13 nM) at an average depth of 120 m. In the deep southernmost Weddell Basin the concentration of Al increased with depth to ˜0.8 nM at 4000 m, and a higher concentration of ˜1.5 nM in the ˜4500-5200 m deep Weddell Sea Bottom Water. Over the Bouvet triple junction region, where three deep ocean ridges meet, the concentration of Al increased to ˜1.4 nM at about 2000 m depth over the ridge crest. In the deep basin north of the Bouvet region the concentration of Al increased to higher deep values of 4-6 nM due to influence of North Atlantic Deep Water. In general the intermediate and deep distribution of Al results from the mixing of water masses with different origins, the formation of deep water and additional input from sedimentary sources at sea floor elevations. No significant correlation between Al and silicate (Si) was observed. This is in contrast to some other ocean regions. In the Southern Ocean the supply of Al is extremely low and any signal from Al uptake and dissolution with biogenic silica is undetectable against the high dissolved Si and low dissolved Al concentrations. Here the Al-Si relation in the deep ocean is uncoupled. This is due to the scavenging and subsequent loss of the water column of Al, whereas the concentration of Si increases in the deep ocean due to its input from deep dissolution of biogenic diatom frustules settling from the surface layer.

Middag, R.; van Slooten, C.; de Baar, H. J. W.; Laan, P.



The Importance of Having a Ph.D., Career Advice  

Technology Transfer Automated Retrieval System (TEKTRAN)

A presentation on the importance of having a PhD to motivate Initiative to Maximize Student Diversity Program (IMSD) undergrads towards conducting research, pursuing careers in the biomedical field, applying to grad school, and getting a Ph.D., based upon ARS scientist's experiences as a student, a ...


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

ERIC Educational Resources Information Center

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

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



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



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



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


Dissolved humic substances of the Amazon River system1  

Microsoft Academic Search

Aquatic humic and fulvic acids from nine mainstem and seven major tributary sites in the Amazon River Basin are characterized by their elemental and lignin phenol compositions. Com- bined humic substances represent 60% of the riverine dissolved organic carbon (DOC), with fulvic to humic acid (FA : HA) ratios in the mainstem averaging 4.7 -t 1 .O. All dissolved humic

John R. Ertel; John I. Hedges; Allan H. Devol; Jefrey E. Richey



Enhanced Dissolution of Cinnabar (Mercuric Sulfide) by Dissolved  

E-print Network

(HgS), a solid with limited solubility. Hydrophobic (a mixture of both humic and fulvic) acids dissolved more mercury than hydrophilic acids and other nonacid fractions of dissolved organic matter (DOM of various inorganic (chloride, sulfate, or sulfide) and organic ligands (salicylic acid, acetic acid, EDTA

Ryan, Joe


Decomposition of dissolved organic matter from the continental margin  

Microsoft Academic Search

Decomposition of dissolved organic carbon, nitrogen and phosphorus (DOC, DON, DOP) was measured for surface and bottom waters of the middle Atlantic bight (MAB) and deep slope water adjacent to the MAB on two occasions in March and August 1996. We used standard bottle incubation techniques to measure the decrease in dissolved organic matter (DOM) concentrations over a 180-day interval.

Charles S. Hopkinson Jr; Joseph J. Vallino; Amy Nolin



A Novel Acoustic Dissolved Oxygen Transmitter for Fish Telemetry  

Microsoft Academic Search

The multiple responses of fishes to changes in dissolved oxygen saturations have been studied widely in the laboratory. In contrast, only a few studies have included field observa- tions. The objective of the present study was to evaluate the performance of a novel acoustic dissolved oxygen transmitter for field biotelemetry. The results demonstrated that the output of the transmitter was

Jon C. Svendsen; Kim Aarestrup; John F. Steffensen; Jannik Herskin



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 ...



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.



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.


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


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.



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.



Fast dissolving films made of maltodextrins.  


This work aimed to study maltodextrins (MDX) with a low dextrose equivalent as film forming material and their application in the design of oral fast-dissolving films. The suitable plasticizer and its concentration were selected on the basis of flexibility, tensile strength and stickiness of MDX films, and the MDX/plasticizer interactions were investigated by ATR-FTIR spectroscopy. Flexible films were obtained by using 16-20% w/w glycerin (GLY). This basic formulation was adapted to the main production technologies, casting and solvent evaporation (Series C) or hot-melt extrusion (Series E), by adding sorbitan monoleate (SO) or cellulose microcrystalline (MCC), respectively. MCC decreased the film ductility and significantly affected the film disintegration time both in vitro and in vivo (Series C<10s; Series E approximately 1min). To assess the film loading capacity, piroxicam (PRX), a water insoluble drug, was selected. The loading of a drug as a powder decreased the film ductility, but the formulation maintained satisfactory flexibility and resistance to elongation for production and packaging procedures. The films present a high loading capacity, up to 25mg for a surface of 6cm(2). The PRX dissolution rate significantly improved in Series C films independently of the PRX/MDX ratio. PMID:18667164

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



Composition of dissolved organic matter in groundwater  

NASA Astrophysics Data System (ADS)

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

Longnecker, Krista; Kujawinski, Elizabeth B.



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, Å.; 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.



High dissolved methane concentrations in the deep-water Ulleung Basin, East Sea of Korea  

NASA Astrophysics Data System (ADS)

As a part of the Korean National Gas Hydrate Program, a production test in the Ulleung Basin is planned to be performed in 2015. The targets are the gas hydrate-bearing sand reservoirs, which were found during the Second Ulleung Basin Gas Hydrate Drilling Expedition (UBGH2) in 2010. To ensure a safe production test, an environmental program has been conducted by the Korea Institute of Geoscience and Mineral Resources (KIGAM) since 2012. This program includes a baseline survey using a KIGAM Seafloor Observation System (KISOS) and R/V TAMHAE II of KIGAM, development of a KIGAM Seafloor Monitoring System (KIMOS), and seafloor monitoring on various potential hazards associated with the dissociated gas from gas hydrates using the KIMOS during the production test. A survey for measuring the dissolved methane concentrations in the area at and nearby the gas hydrate production testing site was performed using R/V TAMHAE II and the KISOS. The water samples were also collected and analyzed to measure the dissolved methane concentrations by the SBE carousel water sampler installed in the KISOS and gas chromatography (GC) at KIGAM. The dissolved methane concentrations were also measured using a Frantech METS methane sensor installed in the KISOS. No dissolved methane anomaly was detected at the site where any evidence of gas hydrate presence has not been observed. On the other hand, the water analysis showed high dissolved methane concentrations at the water depth above and within the gas hydrate stability zone (GHSZ) at the site where gas hydrates were identified by drilling. However, these dissolved methane anomalies within the GHSZ were not detected by methane sensor. To examine these uncertain dissolved methane anomalies within the GHSZ, the water samples will be collected and analyzed once again, and the analytical result will be also carefully compared with the data collected using the methane sensor and deep ocean mass spectrometer (DOMS) developed by the University of Hawaii. The results of baseline surveys will be used to set up the KIMOS efficiently.

Ryu, Byong-Jae; Chun, Jong-Hwa



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, Helinä; Yli-Halla, Markku



Selective Sorption of Dissolved Organic Carbon Compounds by Temperate Soils  

PubMed Central

Background Physico-chemical sorption onto soil minerals is one of the major processes of dissolved organic carbon (OC) stabilization in deeper soils. The interaction of DOC on soil solids is related to the reactivity of soil minerals, the chemistry of sorbate functional groups, and the stability of sorbate to microbial degradation. This study was conducted to examine the sorption of diverse OC compounds (D-glucose, L-alanine, oxalic acid, salicylic acid, and sinapyl alcohol) on temperate climate soil orders (Mollisols, Ultisols and Alfisols). Methodology Equilibrium batch experiments were conducted using 0–100 mg C L?1 at a solid-solution ratio of 1?60 for 48 hrs on natural soils and on soils sterilized by ?-irradiation. The maximum sorption capacity, Qmax and binding coefficient, k were calculated by fitting to the Langmuir model. Results Ultisols appeared to sorb more glucose, alanine, and salicylic acid than did Alfisols or Mollisols and the isotherms followed a non-linear pattern (higher k). Sterile experiments revealed that glucose and alanine were both readily degraded and/or incorporated into microbial biomass because the observed Qmax under sterile conditions decreased by 22–46% for glucose and 17–77% for alanine as compared to non-sterile conditions. Mollisols, in contrast, more readily reacted with oxalic acid (Qmax of 886 mg kg?1) and sinapyl alcohol (Qmax of 2031 mg kg?1), and no degradation was observed. The reactivity of Alfisols to DOC was intermediate to that of Ultisols and Mollisols, and degradation followed similar patterns as for Ultisols. Conclusion This study demonstrated that three common temperate soil orders experienced differential sorption and degradation of simple OC compounds, indicating that sorbate chemistry plays a significant role in the sorptive stabilization of DOC. PMID:23209742

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



Nanostructured conductive polymeric materials  

NASA Astrophysics Data System (ADS)

Conductive polymer composites (CPCs) are a suitable alternative to metals in many applications due to their light-weight, corrosion resistance, low cost, ease of processing and design flexibility. CPCs have been formulated using different types of conductive fillers. In this PhD thesis, the focus is on CPCs for electrostatic discharge (ESD) protection and electromagnetic interference (EMI) attenuation. Despite the versatility of conductive fillers, carbon black (CB) has been the dominant filler to make CPCs for ESD protection applications because CB/polymer composites have a cost advantage over all other CPCs. For EMI shielding, stainless steel fibres and metal coated fibers are the preferred fillers, however CPCs made of those fibers are not the dominant EMI shielding materials. Metal coated and polymer plated polymers are the most widely used EMI shielding options. The limited use of CPCs in the EMI shielding market is because the high filler loading required to formulate a composite with an adequate level of shielding remarkably increases the composite price. In order to increase the competitiveness of CPCs, percolation threshold should be minimized as much as possible and composites with high EMI shielding capabilities at low filler loading should be formulated because all conductive fillers are expensive compared to polymers. In this thesis, two different methodologies to reduce percolation threshold in CPCs have been successfully developed and a CPC with exceptional EMI shielding capability has been formulated using copper nanowires as conductive filler. The first percolation threshold reduction technique is based on the selective localization of CB at the interface of immiscible polymer blend. The technique requires adding a copolymer that prefers the blend's interface and for which CB nanoparticles has the highest affinity. The second method is based on producing a CPC powder and then using this powder as a conductive filler to produce composite by dry mixing with pure polymer powder followed by compression molding. The EMI shielding material was developed using copper nanowires. CuNW/Polystyrene composites exhibit EMI shielding effectiveness exceeding that of metal microfillers and carbon nanotube/polymer composites and approaching that of coating techniques have been formulated by solution processing and dry mixing.

Al-Saleh, Mohammed H.


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.



Ph.D. Manual PH.D. PROGRAM  

E-print Network

Ph.D. Manual 1 PH.D. PROGRAM IN SCHOOL PSYCHOLOGY Manual of Policies and Procedures College:// Approved: May 1985 Last Revision: July 2010 #12;Ph.D. Manual 2 Table of Contents Program Philosophy..................................................................................... 3 Differentiation of Ph.D. & Ed.S. Programs................................................... 8

Gilchrist, James F.


Hydrography and budget of dissolved total nitrogen and dissolved oxygen in the stratified season in Mikawa Bay, Japan  

Microsoft Academic Search

Distributions of salinity, dissolved total nitrogen (DTN) and dissolved oxygen (DO) were observed once a month throughout a year in Mikawa Bay, one of the most eutrophic bays in Japan. Supply of freshwater, DTN and DO from the land and precipitation was estimated. Hydrography, circulation and transformation of DTN and DO during the stratified period were investigated simultaneously by a

Teruaki Suzukit; Yasuo Matsukawa



Salicylhydroxamic acid (SHAM) inhibition of the dissolved inorganic carbon concentrating process in unicellular green algae  

SciTech Connect

Rates of photosynthetic O{sub 2} evolution, for measuring K{sub 0.5}(CO{sub 2} + HCO{sub 3}{sup {minus}}) at pH 7, upon addition of 50 micromolar HCO{sub 3}{sup {minus}} to air-adapted Chlamydomonas, Dunaliella, or Scenedesmus cells, were inhibited up to 90% by the addition of 1.5 to 4.0 millimolar salicylhydroxamic acid (SHAM) to the aqueous medium. The apparent K{sub i}(SHAM) for Chlamydomonas cells was about 2.5 millimolar, but due to low solubility in water effective concentrations would be lower. Salicylhydroxamic acid did not inhibit oxygen evolution or accumulation of bicarbonate by Scenedesmus cells between pH 8 to 11 or by isolated intact chloroplasts from Dunaliella. Thus, salicylhydroxamic acid appears to inhibit CO{sub 2} uptake, whereas previous results indicate that vanadate inhibits bicarbonate uptake. These conclusions were confirmed by three test procedures with three air-adapted algae at pH 7. Salicylhydroxamic acid inhibited the cellular accumulation of dissolved inorganic carbon, the rate of photosynthetic O{sub 2} evolution dependent on low levels of dissolved inorganic carbon (50 micromolar NaHCO{sub 3}), and the rate of {sup 14}CO{sub 2} fixation with 100 micromolar ({sup 14}C)HCO{sub 3}{sup {minus}}. Salicylhydroxamic acid inhibition of O{sub 2} evolution and {sup 14}CO{sub 2}-fixation was reversed by higher levels of NaHCO{sub 3}. Thus, salicylhydroxamic acid inhibition was apparently not affecting steps of photosynthesis other than CO{sub 2} accumulation. Although salicylhydroxamic acid is an inhibitor of alternative respiration in algae, it is not known whether the two processes are related.

Goyal, A.; Tolbert, N.E. (Michigan State Univ., East Lansing (USA))



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.



Dissolved organic carbon and chromophoric dissolved organic matter properties of rivers in the USA  

USGS Publications Warehouse

Dissolved organic carbon (DOC) concentration and chromophoric dissolved organic matter (CDOM) parameters were measured over a range of discharge in 30 U.S. rivers, covering a diverse assortment of fluvial ecosystems in terms of watershed size and landscape drained. Relationships between CDOM absorption at a range of wavelengths (a254, a350, a440) and DOC in the 30 watersheds were found to correlate strongly and positively for the majority of U.S. rivers. However, four rivers (Colorado, Colombia, Rio Grande and St. Lawrence) exhibited statistically weak relationships between CDOM absorption and DOC. These four rivers are atypical, as they either drain from the Great Lakes or experience significant impoundment of water within their watersheds, and they exhibited values for dissolved organic matter (DOM) parameters indicative of autochthonous or anthropogenic sources or photochemically degraded allochthonous DOM and thus a decoupling between CDOM and DOC. CDOM quality parameters in the 30 rivers were found to be strongly correlated to DOM compositional metrics derived via XAD fractionation, highlighting the potential for examining DOM biochemical quality from CDOM measurements. This study establishes the ability to derive DOC concentration from CDOM absorption for the majority of U.S. rivers, describes characteristics of riverine systems where such an approach is not valid, and emphasizes the possibility of examining DOM composition and thus biogeochemical function via CDOM parameters. Therefore, the usefulness of CDOM measurements, both laboratory-based analyses and in situ instrumentation, for improving spatial and temporal resolution of DOC fluxes and DOM dynamics in future studies is considerable in a range of biogeochemical studies.

Spencer, Robert G.M.; Butler, Kenna D.; Aiken, George R.



Dissolved organic carbon and chromophoric dissolved organic matter properties of rivers in the USA  

NASA Astrophysics Data System (ADS)

Dissolved organic carbon (DOC) concentration and chromophoric dissolved organic matter (CDOM) parameters were measured over a range of discharge in 30 U.S. rivers, covering a diverse assortment of fluvial ecosystems in terms of watershed size and landscape drained. Relationships between CDOM absorption at a range of wavelengths (a254, a350, a440) and DOC in the 30 watersheds were found to correlate strongly and positively for the majority of U.S. rivers. However, four rivers (Colorado, Colombia, Rio Grande and St. Lawrence) exhibited statistically weak relationships between CDOM absorption and DOC. These four rivers are atypical, as they either drain from the Great Lakes or experience significant impoundment of water within their watersheds, and they exhibited values for dissolved organic matter (DOM) parameters indicative of autochthonous or anthropogenic sources or photochemically degraded allochthonous DOM and thus a decoupling between CDOM and DOC. CDOM quality parameters in the 30 rivers were found to be strongly correlated to DOM compositional metrics derived via XAD fractionation, highlighting the potential for examining DOM biochemical quality from CDOM measurements. This study establishes the ability to derive DOC concentration from CDOM absorption for the majority of U.S. rivers, describes characteristics of riverine systems where such an approach is not valid, and emphasizes the possibility of examining DOM composition and thus biogeochemical function via CDOM parameters. Therefore, the usefulness of CDOM measurements, both laboratory-based analyses and in situ instrumentation, for improving spatial and temporal resolution of DOC fluxes and DOM dynamics in future studies is considerable in a range of biogeochemical studies.

Spencer, Robert G. M.; Butler, Kenna D.; Aiken, George R.



Bioavailability and characterization of dissolved organic nitrogen and dissolved organic phosphorus in wastewater effluents.  


There is still a great knowledge gap in the understanding of characteristics and bioavailability of dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) in wastewater effluents, which surmise implications related to both discharge regulation and treatment practice. In this study, we simultaneously investigated the characteristics and bioavailability of both DON and DOP, with separated hydrophilic versus hydrophobic fractions, in highly-treated wastewater effluents for the first time. The tertiary effluents from two wastewater treatment plants were separated into two fractions by XAD-8 resin coupled with anion exchange resin based on the hydrophobicity. Results showed that the majority of DON was present in hydrophilic forms while more DOP existed in hydrophobic forms. Hydrophilic DON contributed to 64.0%-72.2% of whole DON, while hydrophobic DOP accounted for 61.4%-80.7% of total DOP for the two plants evaluated. The effluents and their fractions were then subject to bioavailability assay based on 14-day algae growth. The results indicated that majority (~73-75%) of the effluent DOP, particularly the hydrophobic fraction with lower C/P ratio was more likely to be bioavailable for algal growth. The bioavailable fraction of DON varied widely (28%-61%) for the two plants studied and the hydrophilic fraction with lower C/N ratio seemed to exhibit higher bioavailability than the hydrophobic portion. The differences in bioavailable DON and DOP distributions of effluents from those two plants could be attributed to different receiving effluent compositions and wastewater treatment processes. In addition, fluorescence excitation-emission matrices (EEMs) combined with parallel factor analysis (PARAFAC) were used to characterize the dissolved organic matter (DOM) in wastewater effluent, which provided insights into the nature of organic matter in wastewater samples with different characteristics and originating sources. PMID:25527968

Qin, Chao; Liu, Haizhou; Liu, Lei; Smith, Scott; Sedlak, David L; Gu, April Z



A Multi-scale, Multi-method Approach to Examining the Effects of Landscape Age on Dissolved Organic Carbon and Nitrogen Movement in Arctic Alaska  

NASA Astrophysics Data System (ADS)

Studies of arctic terrestrial carbon cycling have emphasized gaseous carbon fluxes, with less attention to dissolved carbon fluxes. However, recent work suggests that dissolved fluxes could be significant components of arctic terrestrial carbon budgets. Nitrogen availability exerts a strong control on terrestrial C balance through effects on plant productivity. Although most nitrogen in arctic systems is found in the organic form, little is known about the controls on dissolved organic nitrogen (DON) production and transport at high latitudes. We examined regional patterns of dissolved organic carbon (DOC) and DON production and concentrations over a glacial age chronosequence in northern Alaska. We used soil incubations, lysimeters, and stream sampling to study the relative importance of glacial age and associated differences in geochemistry at the plot, hillslope and watershed scale. Landscape age significantly affected DOC and DON production in soil incubations and DOC and DON concentrations in soil water at the plot scale. The importance of landscape age diminished at the more integrative hillslope and watershed scales, perhaps due to the influence of hillslope vegetation or riparian soils. DOC and DON concentrations were more correlated in laboratory incubations without vegetation and than at the hillslope and watershed scale. Two possible influences on dissolved carbon production that vary with landscape age are differences in exchangeable calcium and pH, which decrease over time as a result of weathering. In a factorial soil manipulation experiment with samples from multiple sites across the glacial age chronosequence, both decreasing pH and increasing exchangeable calcium concentrations significantly reduced the production of dissolved organic carbon. Our results suggest that landscape age is an important control on dissolved fluxes of carbon and nitrogen, but the effect is dependent on the scale of measurement.

Whittinghill, K. A.; Hobbie, S. E.; Finlay, J. C.



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.



How much does fluvial dissolved organic carbon export from blanket bogs vary at the regional scale? An example from the Pennine region of Yorkshire, UK  

NASA Astrophysics Data System (ADS)

Often only one or a very small number of stream sampling points are used to infer wider regional export of fluvial carbon from peatlands. However, we suggest that the amount of fluvial carbon being exported varies enormously within regions even when blanket peat is the dominant land cover type. Here we present results from an extensive and comprehensive monitoring project covering blanket peat dominated catchments across the Pennine region of the UK using data from 2006 onwards. Up to the start of January 2014 the dataset contained dissolved organic carbon (DOC) data for approximately 11500 stream water samples (both routine spot samples and storm event samples). The majority of these DOC measurements also have associated UV-Vis absorbance data allowing an insight into the composition of the DOC present, specifically the dominance of humic versus fulvic acids and the degree of aromaticity (SUVA254). Additional data to support interpretation of the regional variability of DOC includes particulate organic carbon, discharge, pH, conductivity and turbidity, water table depth, soil water chemistry and meteorological data. We provide an unparalleled insight into the spatial and temporal variability of DOC in a region of blanket bogs showing how catchment attributes influence fluvial DOC, how there are hotspots of DOC production and how high flow events regulating DOC export and its composition.

Grayson, Richard; Blundell, Antony; Holden, Joseph



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.


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



Impact of circulation on export production, dissolved organic matter, and dissolved oxygen in the ocean: Results from Phase II of the Ocean  

E-print Network

Impact of circulation on export production, dissolved organic matter, and dissolved oxygen) and dissolved oxygen simulated by 12 global ocean models participating in the second phase of the Ocean Carbon matter, and dissolved oxygen in the ocean: Results from Phase II of the Ocean Carbon-cycle Model

Follows, Mick


Electrically conductive and thermally conductive materials for electronic packaging  

NASA Astrophysics Data System (ADS)

The aim of this dissertation is to develop electrically or thermally conductive materials that are needed for electronic packaging and microelectronic cooling. These materials are in the form of coatings and are made from pastes. The research work encompasses paste formulation, studying the process of converting a paste to a conductive material, relating the processing conditions to the structure and performance, and evaluating performance attributes that are relevant to the application of these conductive materials. The research has resulted in new information that is valuable to the microelectronic industry. Work on electrically conductive materials emphasizes the development of electrical interconnection materials in the form of air-firable glass-free silver-based electrically conductive thick films, which use the Ti-Al alloy as the binder and are in contrast to conventional films that use glass as the binder. The air-firability, as enabled by minor additions of tin and zinc to the paste, is in contrast to previous glass-free films that are not firable. The recommended firing condition is 930°C in air. The organic vehicle in the paste comprises ethyl cellulose, which undergoes thermal decomposition during burnout of the paste. The ethyl cellulose is dissolved in ether, which facilitates the burnout. Excessive ethyl cellulose hinders the burnout. A higher heating rate results in more residue after burnout. The presence of silver particles facilitates drying and burnout. Firing in air gives lower resistivity than firing in oxygen. Firing in argon gives poor films. Compared to conventional films that use glass as the binder, these films, when appropriately fired, exhibit lower electrical resistivity (2.5 x 10-6 and higher scratch resistance. Work on thermally conductive materials addresses thermal interface materials, which are materials placed at the interface between a heat sink and a heat source for the purpose of improving the thermal contact. Heat dissipation is the most critical problem in the microelectronic industry. This work emphasizes the development of thermal interface materials in the form of phase change materials, namely paraffin wax, which melts at 48°C. The addition of boron nitride particles to the wax improves the performance, as indicated by the thermal contact conductance between copper surfaces. The melting of the wax improves the conformability of the thermal interface material, thereby enhancing the conductance. Pressure applied in the direction perpendicular to the plane of the interface also enhances the conductance. With 15 wt. % BN and a pressure of 0.3 MPa, a thermal contact conductance comparable to that attained by using solder (applied in the molten state) as the thermal interface material has been attained.

Liu, Zongrong


Application of MODIS on monitoring dissolved inorganic nitrogen and dissolved inorganic phosphorus in Haizhou Gulf  

NASA Astrophysics Data System (ADS)

Red tides have been increasingly observed in the gulf of Haizhou and considered a serious environmental problem from the beginning of the new century. Eutrophication of water is an important reason of red tide occurrence. This paper used the observation data of the concentration of dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) in Haizhou Gulf from 2004 to 2006 and selected synchronous MODIS Terra 1B data with 500m spatial resolution in this period of time. We established factors with single band and multi-bands, and then calculated the correlation of each factor with DIN concentration, DIP concentration, and their logarithm respectively. The factors with stronger correlation were used to establish regression models of DIN and DIP's concentration. After comparing these models, we chose the linear model of DIN concentration established by factor ) 4, 3 ( 11 F and inverse model of the logarithm of DIP concentration established by factor ) 5, 6 ( 7 F as their final regression model. The relative accuracy of DIN concentration model achieved about 70%; the retrieving results of DIN concentration were consistent well with real conditions. The relative accuracy of the logarithm of DIP concentration achieved about 90%. The results prove the feasibility of monitoring DIN concentration and the exponential order of DIP concentration in offshore of Jiangsu Province.

Xu, Yong; Zhang, Ying; Zhang, Dong; Liu, Jitang



Effects of Dissolved Carbonate on Arsenate Adsorption and Surface Speciation at the Hematite-Water Interface  

USGS Publications Warehouse

Effects of dissolved carbonate on arsenate [As(V)] reactivity and surface speciation at the hematite-water interface were studied as a function of pH and two different partial pressures of carbon dioxide gas [PCO2 = 10 -3.5 atm and ???0; CO2-free argon (Ar)] using adsorption kinetics, pseudo-equilibrium adsorption/titration experiments, extended X-ray absorption fine structure spectroscopic (EXAFS) analyses, and surface complexation modeling. Different adsorbed carbonate concentrations, due to the two different atmospheric systems, resulted in an enhanced and/or suppressed extent of As(V) adsorption. As(V) adsorption kinetics [4 g L -1, [As(V)]0 = 1.5 mM and / = 0.01 M NaCl] showed carbonate-enhanced As(V) uptake in the air-equilibrated systems at pH 4 and 6 and at pH 8 after 3 h of reaction. Suppressed As(V) adsorption was observed in the air-equilibrated system in the early stages of the reaction at pH 8. In the pseudo-equilibrium adsorption experiments [1 g L-1, [As(V)] 0 = 0.5 mM and / = 0.01 M NaCl], in which each pH value was held constant by a pH-stat apparatus, effects of dissolved carbonate on As(V) uptake were almost negligible at equilibrium, but titrant (0.1 M HCl) consumption was greater in the air-equilibrated systems (PCO2 = 10-3.5 atm)than in the CO2-free argon system at pH 4-7.75. The EXAFS analyses indicated that As(V) tetrahedral molecules were coordinated on iron octahedral via bidentate mononuclear (???2.8 A??) and bidentate binuclear (???3.3 A??) bonding at pH 4.5-8 and loading levels of 0.46-3.10 ??M m-2. Using the results of the pseudoequilibrium adsorption data and the XAS analyses, the pH-dependent As(V) adsorption under the PCO2 = 10-3.5 atm and the CO2-free argon system was modeled using surface complexation modeling, and the results are consistent with the formation of nonprotonated bidentate surface species at the hematite surfaces. The results also suggest that the acid titrant consumption was strongly affected by changes to electrical double-layer potentials caused by the adsorption of carbonate in the air-equilibrated system. Overall results suggest that the effects of dissolved carbonate on As(V) adsorption were influenced by the reaction conditions [e.g., available surface sites, initial As(V) concentrations, and reaction times]. Quantifying the effects of adsorbed carbonate may be important in predicting As(V) transport processes in groundwater, where iron oxide-coated aquifer materials are exposed to seasonally fluctuating partial pressures of CO2(g).

Arai, Y.; Sparks, D.L.; Davis, J.A.



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



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.D. shortage  

NASA Astrophysics Data System (ADS)

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


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

NASA Astrophysics Data System (ADS)

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

Harries, Dennis; Pollok, Kilian; Langenhorst, Falko



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...


17-4 PH and 15-5 PH  

NASA Technical Reports Server (NTRS)

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

Johnson, Howard T.



Population differentiation of the African cyprinid Barbus neumayeri across dissolved oxygen regimes  

E-print Network

Population differentiation of the African cyprinid Barbus neumayeri across dissolved oxygen regimes structure was associated with (i) dissolved oxygen regime (hypoxia or normoxia), (ii) geographical distance, or (iii) a combination of dissolved oxygen regime and geographical distance. Our results indicate

Chapman, Lauren J.


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

Code of Federal Regulations, 2010 CFR

...Applicability; description of the dissolving kraft subcategory. 430.10 Section 430...PAPERBOARD POINT SOURCE CATEGORY Dissolving Kraft Subcategory § 430.10 Applicability; description of the dissolving kraft subcategory. The provisions of...



Evaluation of specific ultraviolet absorbance as an indicator of the chemical composition and reactivity of dissolved organic carbon  

USGS Publications Warehouse

Specific UV absorbance (SUVA) is defined as the UV absorbance of a water sample at a given wavelength normalized for dissolved organic carbon (DOC) concentration. Our data indicate that SUVA, determined at 254 nm, is strongly correlated with percent aromaticity as determined by 13C NMR for 13 organic matter isolates obtained from a variety of aquatic environments. SUVA, therefore, is shown to be a useful parameter for estimating the dissolved aromatic carbon content in aquatic systems. Experiments involving the reactivity of DOC with chlorine and tetramethylammonium hydroxide (TMAH), however, show a wide range of reactivity for samples with similar SUVA values. These results indicate that, while SUVA measurements are good predictors of general chemical characteristics of DOC, they do not provide information about reactivity of DOC derived from different types of source materials. Sample pH, nitrate, and iron were found to influence SUVA measurements.

Weishaar, J.L.; Aiken, G.R.; Bergamaschi, B.A.; Fram, M.S.; Fujii, R.; Mopper, K.



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




EPA Science Inventory

The measurement and interpretation of geochemical redox parameters are key components of ground water remedial investigations. Dissolved oxygen (DO) is perhaps the most robust geochemical parameter in redox characterization; however, recent work has indicated a need for proper da...



EPA Science Inventory

The classical assumption that the lowest dissolved oxygen (DO) occurs at the highest temperature may not always hold. The DO saturation concentration decreases monotonically with increasing temperature, lowering the DO, but the reaeration coefficient increases monotonically with ...


The effect of membrane filtration on dissolved trace element concentrations  

USGS Publications Warehouse

The almost universally accepted operational definition for dissolved constituents is based on processing whole-water samples through a 0.45-??m membrane filter. Results from field and laboratory experiments indicate that a number of factors associated with filtration, other than just pore size (e.g., diameter, manufacturer, volume of sample processed, amount of suspended sediment in the sample), can produce substantial variations in the 'dissolved' concentrations of such elements as Fe, Al, Cu, Zn, Pb, Co, and Ni. These variations result from the inclusion/exclusion of colloidally- associated trace elements. Thus, 'dissolved' concentrations quantitated by analyzing filtrates generated by processing whole-water through similar pore- sized membrane filters may not be equal/comparable. As such, simple filtration through a 0.45-??m membrane filter may no longer represent an acceptable operational definition for dissolved chemical constituents. This conclusion may have important implications for environmental studies and regulatory agencies.

Horowitz, A.J.; Lum, K.R.; Garbarino, J.R.; Hall, G.E.M.; Lemieux, C.; Demas, C.R.




EPA Science Inventory

Fluctuations of dissolved oxygen concentrations and water temperatures in their natural spawning sites were measured during embryo through larva stages of northern pike (Esox lucius), and during embryo and sac larva stages of bluegills (Lepomis macrochirus) and pumpkinseeds (Lepo...



EPA Science Inventory

This study reports on the operation of a plant scale dissolved air flotation system installed to define and evaluate attainable shrimp cannery wastewater treatment levels. The system was operated in all three modes of DAF pressurization. Destabilizing coagulants investigation inc...


Dissolved hydrogen and nitrogen fixation in the oligotrophic North Pacific Subtropical Gyre.  


The production of hydrogen (H2) is an inherent component of biological dinitrogen (N2) fixation, and there have been several studies quantifying H2 production relative to N2 fixation in cultures of diazotrophs. However, conducting the relevant measurements for a field population is more complex as shown by this study of N2 fixation, H2 consumption and dissolved H2 concentrations in the oligotrophic North Pacific Ocean. Measurements of H2 oxidation revealed microbial consumption of H2 was equivalent to 1-7% of ethylene produced during the acetylene reduction assay and 11-63% of (15)N2 assimilation on a molar scale. Varying abundances of Crocosphaera and Trichodesmium as revealed by nifH gene abundances broadly corresponded with diel changes observed in both N2 fixation and H2 oxidation. However, no corresponding changes were observed in the dissolved H2 concentrations which remained consistently supersaturated (147-560%) relative to atmospheric equilibrium. The results from this field study allow the efficiency of H2 cycling by natural populations of diazotrophs to be compared to cultured representatives. The findings indicate that dissolved H2 concentrations may depend not only on the community composition of diazotrophs but also upon relevant environmental parameters such as light intensity or the presence of other H2-metabolizing microorganisms. PMID:24115620

Wilson, Samuel T; del Valle, Daniela A; Robidart, Julie C; Zehr, Jonathan P; Karl, David M



Upwelling and dissolved oxygen variability over the continental shelf off Central Chile  

NASA Astrophysics Data System (ADS)

In contrast to the legendary upwelling that is present along the Peruvian and northern Chilean coasts, the coastal ocean off central Chile presents a highly seasonal upwelling regime that extends from early spring to mid fall. This region is also affected by a strong subsurface poleward flow, which transports southward low-oxygen water from the eastern equatorial Pacific. Coastal waters are highly productive due to upwelling, but the upwelled source waters are very low in oxygen and may produce hypoxia near the bottom over the continental shelf. The spatial structure and main scales of variability of the upwelling cells and dissolved oxygen are poorly understood off central Chile. One of the main limitations has been the lack of direct information. During the last years an observational program has been conducted over the relatively wide continental shelf off Concepción (36°30' S). This program has included ship-based (monthly) time-series, underwater glider observations and time-series based on moored sensors. Here, based on physical (temperature, salinity, pressure, velocity), biological (chlorophyll fluorescence) and chemical (dissolved oxygen) information, we analyze the main scales of time variability of the upwelling, the coastal currents and their impact on the dissolved oxygen. The cross-shelf structure of the upwelling region was sampled using underwater gliders capable of sampling the entire water column to a maximum of 1000 m and from near shore to 200 km offshore.

Pizarro, Oscar



Dissolved hydrogen and nitrogen fixation in the oligotrophic North Pacific Subtropical Gyre  

PubMed Central

The production of hydrogen (H2) is an inherent component of biological dinitrogen (N2) fixation, and there have been several studies quantifying H2 production relative to N2 fixation in cultures of diazotrophs. However, conducting the relevant measurements for a field population is more complex as shown by this study of N2 fixation, H2 consumption and dissolved H2 concentrations in the oligotrophic North Pacific Ocean. Measurements of H2 oxidation revealed microbial consumption of H2 was equivalent to 1–7% of ethylene produced during the acetylene reduction assay and 11–63% of 15N2 assimilation on a molar scale. Varying abundances of Crocosphaera and Trichodesmium as revealed by nifH gene abundances broadly corresponded with diel changes observed in both N2 fixation and H2 oxidation. However, no corresponding changes were observed in the dissolved H2 concentrations which remained consistently supersaturated (147–560%) relative to atmospheric equilibrium. The results from this field study allow the efficiency of H2 cycling by natural populations of diazotrophs to be compared to cultured representatives. The findings indicate that dissolved H2 concentrations may depend not only on the community composition of diazotrophs but also upon relevant environmental parameters such as light intensity or the presence of other H2-metabolizing microorganisms. PMID:24115620

Wilson, Samuel T; del Valle, Daniela A; Robidart, Julie C; Zehr, Jonathan P; Karl, David M



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

USGS Publications Warehouse

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

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



Loading and utilization of dissolved organic carbon from emergent macrophytes  

Microsoft Academic Search

The very high productivity of emergent macrophytes can provide major sources of dissolved organic matter to recipient aquatic ecosystems. Leachate was collected from live and senescent tissues of Juncus effusus L. and Typha latifolia L. and analyzed for dissolved organic carbon (DOC; mg C 1?1 cm?2 surface area) and its availability to wetland bacteria. Leachate DOC ranged from 1.9 to

Carroll J. Mann; Robert G. Wetzel



Microbial uptake of dissolved organic matter in Mcmurdo Sound, Antarctica  

Microsoft Academic Search

The distribution and activity of bacterioplankton, and the turnover of dissolved organic matter (DOM) were examined in McMurdo Sound, Antarctica. On the eastern side of the Sound, bacteria averaged 6.5×108 l-1, and turnover rates of dissolved adenosine triphosphate, D-glucose and l-leucine averaged 16, 116 and 124 h, respecitvely. These molecules as well as thymidine were taken up maximally from 0°

R. E. Hodson; F. Azam; A. F. Carlucci; J. A. Fuhrman; D. M. Karl; O. Holm-Hansen



Colored dissolved organic matter in Tampa Bay, Florida  

Microsoft Academic Search

Absorption and fluorescence of colored dissolved organic matter (CDOM) and concentrations of dissolved organic carbon (DOC), chlorophyll and total suspended solids in Tampa Bay and its adjacent rivers were examined in June and October of 2004. Except in Old Tampa Bay (OTB), the spatial distribution of CDOM showed a conservative relationship with salinity in June, 2004 (aCDOM(400)=?0.19×salinity+6.78, R2=0.98, n=17, salinity

Zhiqiang Chen; Chuanmin Hu; Robyn N. Conmy; Frank Muller-Karger; Peter Swarzenski



Bacterial utilization of different size classes of dissolved organic matter  

Microsoft Academic Search

Bacterial utilization of high-molecular-weight (HMW; > 1 kDa) and low-molecular-weight (LMW; < 1 kDa) dissolved organic C (DOC) was investigated in freshwater and marine systems by measuring dissolved oxygen consumption, bacterial abundance, and bacterial production in size-fractionated samples. Tangential- flow ultrafiltration was used to separate HMW and LMW DOC. More than 80% of the DOC in Amazon River samples was

Rainer M. W. Arnon; Ronald Benner



Oxygen isotope fractionation in dissolved oxygen in the deep sea  

Microsoft Academic Search

18O variations in dissolved oxygen have been measured at five stations from the eastern equatorial Pacific, at the GEOSECS-I and -II intercalibration stations in the North Pacific and North Atlantic, and along an Antarctic-South Pacific section from MONSOON expedition. Relative to atmospheric oxygen, dissolved oxygen in the ocean is enriched in 18O up to a maximum of 140\\/00, the extreme

P. Kroopnick; H. Craig



Characterisation of dissolved combined amino acids in marine waters.  


Dissolved combined amino acids (DCAA) are important constituents of the dissolved organic nitrogen (DON) pool in marine environments, although little is known about their sources, dynamics and sinks. The DCAA pool consists of various compounds including proteins and peptides, proteins linked to sugars and amino acids adsorbed to humic and fulvic acids, clays and other materials. The proportions of each of these components and the extent to which they are used by microplankton living within the photic zone are not known. An investigation was carried out, using (15)N isotope dilution techniques, to determine the concentration and composition of dissolved amino acid pools in the marine environment. A near-shore seawater sample was collected and split into fractions to determine the concentrations of dissolved free amino acids (DFAA), DCAA and a <3 kDa dissolved peptide fraction (DPEP; obtained by ultrafiltration). DCAA and DPEP fractions were hydrolysed to yield free amino acids and all samples were analysed by gas chromatography/mass spectrometry (GC/MS) as isobutyloxycarbonyl/tert-butyldimethylsilyl derivatives. The DFAA was the smallest fraction representing approximately 1% of total dissolved amino acids. The majority of DCAA was contained in the low molecular weight DPEP fraction (90%) and was probably as a result of release from phytoplankton and degradation by heterotrophic bacteria. PMID:11466786

Sommerville, K; Preston, T



Characterization of urban runoff pollution between dissolved and particulate phases.  


To develop urban stormwater management effectively, characterization of urban runoff pollution between dissolved and particulate phases was studied by 12 rainfall events monitored for five typical urban catchments. The average event mean concentration (AEMC) of runoff pollutants in different phases was evaluated. The AEMC values of runoff pollutants in different phases from urban roads were higher than the ones from urban roofs. The proportions of total dissolved solids, total dissolved nitrogen, and total dissolved phosphorus in total ones for all the catchments were 26.19%-30.91%, 83.29%-90.51%, and 61.54-68.09%, respectively. During rainfall events, the pollutant concentration at the initial stage of rainfall was high and then sharply decreased to a low value. Affected by catchments characterization and rainfall distribution, the highest concentration of road pollutants might appear in the later period of rainfall. Strong correlations were also found among runoffs pollutants in different phases. Total suspended solid could be considered as a surrogate for particulate matters in both road and roof runoff, while dissolved chemical oxygen demand could be regarded as a surrogate for dissolved matters in roof runoff. PMID:23935444

Wei, Zhang; Simin, Li; Fengbing, Tang



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 ...


Cooperative interactions of metal nanoparticles in the ion-exchange matrix with oxygen dissolved in water  

NASA Astrophysics Data System (ADS)

The kinetics of the reduction of molecular oxygen dissolved in water with nanocomposites consisting of an ion-exchange matrix and copper nanoparticles deposited in it in various amounts was studied. As the metal content in the polymer increased, the amount of reduced oxygen initially increased and then reached the limiting value. At a certain metal content, ionization of individual particles with formation of metal counterions changes to the oxidation of particles assembly giving layers of oxide products. The mechanism changes at the percolation threshold of the electron conductivity of the nanocomposite and determines the maximum amount of absorbed oxygen.

Khorolskaya, S. V.; Polyanskii, L. N.; Kravchenko, T. A.; Konev, D. V.



Method for the determination of dissolved chloride, nitrate, and sulfate in natural water using ion chromatography  

USGS Publications Warehouse

Ion chromatography was used for the determination of dissolved chloride, nitrate and sulfate in natural water where concentrations ranged from a detection limit of 0.02 milligrams per liter to 80 milligrams per liter for chloride, to 18 milligrams per liter for nitrate, and to 280 milligrams per liter for sulfate. Specific conductance was the mode of detection used. Three analytical sample size loops of 11, 61, and 250 microliters, were used to include the analytical ranges described. U.S. Geological Survey Standard Reference Water Samples were analyzed to test the precision and accuracy of the analyses.

Brinton, Terry I.; Antweiler, Ronald C.; Taylor, Howard E.



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.



Seasonal Changes in Arctic Dissolved Organic Matter  

NASA Astrophysics Data System (ADS)

The Arctic is a landscape in flux. Temperatures are shifting upward and plant communities are transitioning from tussock to shrub tundra in some regions. Decomposition processes sensitive to temperature, moisture, and plant inputs are controls on the source/sink dynamics of the Arctic C pool. The response of decomposition to warming will, in part, determine if the Arctic C pool feeds back positively or negatively to climate change. The portion of the C pool immediately available to decomposers is dissolved organic matter (DOM). The aim of this is study is to examine the molecular composition of DOM to determine which components vary seasonally in soil pore water among three vegetation types at Toolik Field Station in Alaska. Vegetation types include wet sedge (Carex aquatilis and Eriophorum angustifolium), moist acidic tussock (E. vaginatum) and shrub tundra (Betula nana and Salix sp.). These sites were sampled during winter/summer transitions in 2010 in order to capture both growing season and winter dynamics. We expected the chemical composition of DOM in pore water to be distinct among plant communities due to differences in root exudates, litter chemistry and microbial community; and vary seasonally due to shifting temperature and water availability and their impacts on decomposition of DOM. Soil pore water was isolated through centrifugation and is being characterized with ultra high performance liquid chromatography (UPLC) in line with a quadrupole time of flight mass spectrometer (QTOF-MS) as well as with specific UV absorbance at 254 nm (SUVA), and excitation emission matrices (EEMs) generated by fluorescence spectroscopy. The DOM concentrations across vegetation types show consistent seasonal patterns, spiking at thaw, and declining through late summer. As soils freeze these patterns diverge-in tussock soils DOM concentration decreases slightly, while in shrub and wet sedge sites it increases. SUVA values (indicator of aromaticity) were consistent among vegetation types across seasons; starting low in late winter and at thaw, increasing over the course of the summer and decreasing at the summer to winter transition. Metabolite profiles generated with UPLC-MS were evaluated using principle component analysis. Sampling date explained the most variation in this dataset, with metabolite profiles of the DOM most different in the summer to winter transition. Over 6000 mass features were detected in the metabolite profiles and at least 1500 of these features were significantly different between late summer and early winter. Fluorescence EEMs have been collected for the complete dataset and analysis is underway. Overall, these data suggest the composition of DOM varies more due to season than vegetation type, with changes in quantity, aromaticity, and shifts in the metabolite profiles occurring at seasonal transitions. Efforts are continuing to identify some of the most variable components with MS and EEMs data. By understanding which chemical components of DOM shift seasonally, we can anticipate what portions of the DOM are most subject to change in a warming arctic; and how the gain/loss of those components will play into the sink/source C dynamics under future climate scenarios.

Boot, C. M.; Wallenstein, M. D.; Schimel, J.



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

NASA Astrophysics Data System (ADS)

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 orders of magnitude less than loads associated with historic floods. Conversely, floods exiting the former impoundment following dam removal produced TSS, DOC, and TDN loads comparable to, but slightly greater (1.2-1.75 times) than historic floods. Exported loads were greatest following the complete removal of the dam, most likely because of increased channel gradient. We assert that the disturbances (i.e., concentrations and loads) associated with dam removal should be compared to those generated by floods within the same system rather than comparing the impacts of dam removal with base flow conditions. During the dewatering, impounded floodplain wetlands were found to contribute the following percentages to total impoundment loads: 44% of stored water, 12.6 % of TSS, 49% of DOC, and 33% of TDN. Moreover, the dewatering flood wave was sampled at various points along a 19.2-km reach below the dam to characterize the routing of TSS, DOC, and TDN. TSS released by the impoundment was retained within 10 km of the dam, while TDN and DOC loads increased slightly. Finally, we used our results with those from other removals to provide insight into regional and morphologic controls on exports of impounded materials following dam removal.

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



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

NASA Astrophysics Data System (ADS)

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 systems. During a 57 day irradiation experiment, Congo River DOM was shown to be highly photoreactive with a decrease in DOC, chromophoric DOM (CDOM), lignin phenol concentrations (?8) and carbon-normalized yields (?8), equivalent to losses of ˜45, 85-95, >95 and >95% of initial values, respectively, and a +3.1 ‰ enrichment of the ?13C-DOC signature. The loss of ?8 and enrichment of ?13C-DOC during irradiation was strongly correlated (r = 0.99, p < 0.01) indicating tight coupling between these biomarkers. Furthermore, the loss of CDOM absorbance was correlated to the loss of ?8 (e.g., a355 versus ?8; r = 0.98, p < 0.01) and ?13C-DOC (e.g., a355 versus ?13C; r = 0.97, p < 0.01), highlighting the potential of CDOM absorbance measurements for delineating the photochemical degradation of lignin and thus terrigenous DOM. It is apparent that these commonly used measurements for examination of terrigenous DOM in the oceans have a higher rate of photochemical decay than the bulk DOC pool. Further process-based studies are required to determine the selective removal rates of these biomarkers for advancement of our understanding of the fate of this material in the ocean.

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



Bacterial contribution to dissolved organic matter in eutrophic Lake Kasumigaura, Japan.  


Incubation experiments using filtered waters from Lake Kasumigaura were conducted to examine bacterial contribution to a dissolved organic carbon (DOC) pool. Bacterial abundance, bacterial production, concentrations of DOC, total dissolved amino acids (TDAA), and total dissolved neutral sugars (TDNS) were monitored during the experiments. Bacterial production during the first few days was very high (20 to 35 ?g C liter(-1) day(-1)), accounting for 40 to 70% of primary production. The total bacterial production accounted for 34 to 55% of the DOC loss during the experiment, indicating high bacterial activities in Lake Kasumigaura. The DOC degradation was only 12 to 15%, whereas the degradation of TDAA and TDNS ranged from 30 to 50%, suggesting the preferential usage of TDAA and TDNS. The contribution of bacterially derived carbon to a DOC pool in Lake Kasumigaura was estimated using d-amino acids as bacterial biomarkers and accounted for 30 to 50% of the lake DOC. These values were much higher than those estimated for the open ocean (20 to 30%). The ratio of bacterially derived carbon to bulk carbon increased slightly with time, suggesting that the bacterially derived carbon is more resistant to microbial degradation than bulk carbon. This is the first study to estimate the bacterial contribution to a DOC pool in freshwater environments. These results indicate that bacteria play even more important roles in carbon cycles in freshwater environments than in open oceans and also suggests that recent increases in recalcitrant DOC in various lakes could be attributed to bacterially derived carbon. The potential differences in bacterial contributions to dissolved organic matter (DOM) between freshwater and marine environments are discussed. PMID:24038686

Kawasaki, Nobuyuki; Komatsu, Kazuhiro; Kohzu, Ayato; Tomioka, Noriko; Shinohara, Ryuichiro; Satou, Takayuki; Watanabe, Fumiko Nara; Tada, Yuya; Hamasaki, Koji; Kushairi, M R M; Imai, Akio



A novel kinetic determination of dissolved chromium species in natural and industrial waste water.  


A highly sensitive, selective and simple kinetic method was developed for the determination of dissolved chromium species based on the catalytic effect of Cr(III) and/or Cr(VI) on the oxidation of 2-amino-5-methylphenol (AMP) with H(2)O(2). The fixed time and initial rate variants were used for kinetic spectrophotometric measurements by tracing the oxidized product at 400nm for 10min after starting the reaction. Boric acid and Tween-40 exerted pronounced activating and micellar sensitizing effects on the studied redox reaction, respectively. The optimum reaction conditions were: 3.0mmoll(-1) AMP, 0.45moll(-1) H(2)O(2), 0.50moll(-1) boric acid, 4v/v% Tween-40, 10mmoll(-1) phosphate buffer and pH 6.45+/-0.02 at 35 degrees C. Both Cr(III) and Cr(VI) ions exerted the same catalytic effect on the studied reaction. Linear calibration graphs were obtained for the determination of up to 6.0ngml(-1) Cr with detection limits of 0.054 and 0.10ngml(-1) Cr; following the fixed time and initial rate methods, respectively. The proposed method was successfully applied to the speciation and determination of trace levels of dissolved Cr(III) and Cr(VI) in natural and effluents of industrial waste water. The total dissolved Cr(III) and Cr(VI) species was determined first. In a second run, Cr(VI) was determined alone after precipitation of Cr(III) ions in presence of Al(OH)(3) collector, where Cr(III) is then determined by difference. Moreover, published catalytic-spectrophotometric methods for chromium determination were reviewed. PMID:18970793

Mohamed, Ashraf A; Mubarak, Ahmed T; Marstani, Zakaria M H; Fawy, Khaled F



Association of dissolved aluminum with silica: Connecting molecular structure to surface reactivity using NMR  

NASA Astrophysics Data System (ADS)

We studied uptake mechanisms for dissolved Al on amorphous silica by combining bulk-solution chemistry experiments with solid-state Nuclear Magnetic Resonance techniques ( 27Al magic-angle spinning (MAS) NMR, 27Al{ 1H} cross-polarization (CP) MAS NMR and 29Si{ 1H} CP-MAS NMR). We find that reaction of Al (1 mM) with amorphous silica consists of at least three reaction pathways; (1) adsorption of Al to surface silanol sites, (2) surface-enhanced precipitation of an aluminum hydroxide, and (3) bulk precipitation of an aluminosilicate phase. From the NMR speciation and water chemistry data, we calculate that 0.20 (±0.04) tetrahedral Al atoms nm -2 sorb to the silica surface. Once the surface has sorbed roughly half of the total dissolved Al (˜8% site coverage), aluminum hydroxides and aluminosilicates precipitate from solution. These precipitation reactions are dependent upon solution pH and total dissolved silica concentration. We find that the Si:Al stoichiometry of the aluminosilicate precipitate is roughly 1:1 and suggest a chemical formula of NaAlSiO 4 in which Na + acts as the charge compensating cation. For the adsorption of Al, we propose a surface-controlled reaction mechanism where Al sorbs as an inner-sphere coordination complex at the silica surface. Analogous to the hydrolysis of Al(OH)63+, we suggest that rapid deprotonation by surface hydroxyls followed by dehydration of ligated waters results in four-coordinate (>SiOH) 2Al(OH) 2 sites at the surface of amorphous silica.

Houston, J. R.; Herberg, J. L.; Maxwell, R. S.; Carroll, S. A.



Co-precipitation of dissolved organic matter by calcium carbonate in Pyramid Lake, Nevada  

USGS Publications Warehouse

Our previous research has demonstrated that dissolved organic matter (DOM) influences calcium carbonate mineral formation in surface and ground water. To better understand DOM mediation of carbonate precipitation and DOM co-precipitation and/or incorporation with carbonate minerals, we characterized the content and speciation of DOM in carbonate minerals and in the lake water of Pyramid Lake, Nevada, USA. A 400-gram block of precipitated calcium carbonate from the Pyramid Lake shore was dissolved in 8 liters of 10% acetic acid. Particulate matter not dissolved by acetic acid was removed by centrifugation. DOM from the carbonate rock was fractionated into nine portions using evaporation, dialysis, resin adsorption, and selective precipitations to remove acetic acid and inorganic constituents. The calcium carbonate rock contained 0.23% DOM by weight. This DOM was enriched in polycarboxylic proteinaceous acids and hydroxy-acids in comparison with the present lake water. DOM in lake water was composed of aliphatic, alicyclic polycarboxylic acids. These compound classes were found in previous studies to inhibit calcium carbonate precipitation. DOM fractions from the carbonate rock were 14C-age dated at about 3,100 to 3,500 years before present. The mechanism of DOM co-precipitation and/or physical incorporation in the calcium carbonate is believed to be due to formation of insoluble calcium complexes with polycarboxylic proteinaceous acids and hydroxy-acids that have moderately large stability constants at the alkaline pH of the lake. DOM co-precipitation with calcium carbonate and incorporation in precipitated carbonate minerals removes proteinaceous DOM, but nearly equivalent concentrations of neutral and acidic forms of organic nitrogen in DOM remain in solution. Calcium carbonate precipitation during lime softening pretreatment of drinking water may have practical applications for removal of proteinaceous disinfection by-product precursors.

Leenheer, Jerry A.; Reddy, Michael M.



Photochemical Flocculation of Terrestrial Dissolved Organic Matter (tDOM) and Iron: Mechanisms and Geochemical Implications  

NASA Astrophysics Data System (ADS)

Photoflocculation of DOM has received relatively little attention. No previous studies have examined the chemical composition of the flocs nor investigated the coagulation mechanisms. We observed that, after 30 days of simulated solar UV irradiation of 0.1-um filtered Great Dismal Swamp (Virginia) water, 7.1% of the DOC was converted to POC while 75% was remineralized. Approximately 87% of the iron was removed from the dissolved phase after 30 days, but iron did not flocculate until a major fraction of DOM was removed by photochemical degradation and flocculation (>10 days); thus, during the initial 10 days, there were sufficient organic ligands present and/or the pH was low enough to keep iron in solution. Although photoflocculation of iron did eventually occur, it is not clear if iron is required for the initial flocculation of DOM. Using NMR and FT-IR techniques, we found that photochemically flocculated POM was enriched in aliphatics and amide functionality relative to the residual non-flocculated DOM, while carbohydrate-like material was neither photochemical degraded nor flocculated. Based on this spectroscopic evidence, we propose several mechanisms for the formation of the flocs during irradiation. We also speculate that abiotic photochemical flocculation may remove a significant fraction of tDOM and iron from the upper water column between headwaters and the ocean, including estuaries. Fig. 1. Concentrations of dissolved (gray), particulate (black), and adsorbed (white) material as a function of irradiation time: (a) organic carbon, (b) absorption at 300 nm, (c) total iron by atomic absorption, and (d) total nitrogen. Error bars represent the combined standard deviations of the 'total,' 'dissolved,' and 'adsorbed' terms from which the 'particulate' term was calculated. Total nitrogen was not determined for the 'adsorbed' material

Mopper, K.; Helms, J. R.; Mao, J.; Abdulla, H. A.; Schmidt-Rohr, K.



Data on dissolved pesticides and volatile organic compounds in surface and ground waters in the San Joaquin-Tulare basins, California, water years 1992-1995  

USGS Publications Warehouse

This report contains pesticide, volatile organic compound, major ion, nutrient, tritium, stable isotope, organic carbon, and trace-metal data collected from 149 ground-water wells, and pesticide data collected from 39 surface-water stream sites in the San Joaquin Valley of California. Included with the ground-water data are field measurements of pH, specific conductance, alkalinity, temperature, and dissolved oxygen. This report describes data collection procedures, analytical methods, quality assurance, and quality controls used by the National Water-Quality Assessment Program to ensure data reliability. Data contained in this report were collected during a four year period by the San Joaquin?Tulare Basins Study Unit of the United States Geological Survey's National Water-Quality Assessment Program. Surface-water-quality data collection began in April 1992, with sampling done three times a week at three sites as part of a pilot study conducted to provide background information for the surface-water-study design. Monthly samples were collected at 10 sites for major ions and nutrients from January 1993 to March 1995. Additional samples were collected at four of these sites, from January to December 1993, to study spatial and temporal variability in dissolved pesticide concentrations. Samples for several synoptic studies were collected from 1993 to 1995. Ground-water-quality data collection was restricted to the eastern alluvial fans subarea of the San Joaquin Valley. Data collection began in 1993 with the sampling of 21 wells in vineyard land-use settings. In 1994, 29 wells were sampled in almond land-use settings and 9 in vineyard land-use settings; an additional 11 wells were sampled along a flow path in the eastern Fresno County vineyard land-use area. Among the 79 wells sampled in 1995, 30 wells were in the corn, alfalfa, and vegetable land-use setting, and 1 well was in the vineyard land-use setting; an additional 20 were flow-path wells. Also sampled in 1995 were 28 wells used for a regional assessment of ground-water quality in the eastern San Joaquin Valley.

Kinsey, Willie B.; Johnson, Mark V.; Gronberg, JoAnn M.



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.



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

PubMed Central

Ecological investigations were made of habitats containing natural populations of the snail Oncomelania hupensis quadrasi and of habitats free from the snail in the island of Leyte, Philippines. This species of snail is a vector of Schistosoma japonicum in the Philippines. Snail-infested habitats had dissolved oxygen levels of 3.8-9.85 ppm but snail-free habitats had levels of only 0.08-3.6 ppm. Snail-infested habitats were less polluted by organic matter than habitats that were snail-free. Larger numbers of chlorophyll-bearing algae were present in both the water and the soil of snail-infested habitats. Other factors, including temperature, pH, hydrogen carbonate alkalinity, and relative humidity, were also investigated. PMID:4538906

Garcia, Rolando G.



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  

USGS Publications Warehouse

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 100 ??g/L in the dynamic mixing and reaction zone that is downstream of the river's confluence with acid-mine drainage. Mixing diagrams and PHREEQC calculations indicate that mixing and dilution affect the concentrations of all dissolved elements in the reach, and are the dominant processes controlling dissolved Ca, K, Li, Mn and SO4 concentrations. Additionally, dissolved Al and Fe concentrations decrease due to mineral precipitation (gibbsite, schwertmannite and ferrihydrite), whereas dissolved concentrations of Cd, Co, Cu, Ni, Pb and Zn decrease due to adsorption onto newly formed Fe precipitates. The uptake of dissolved metals by aquatic organisms is dependent on the aqueous speciation of the metals and kinetics of complexation reactions between metals, ligands and solid surfaces. Dissolved speciation of Cd, Cu, Ni and Zn in the mixing and reaction zone is assessed using the diffusive gradients in thin films (DGT) technique and results of speciation calculations using the Biotic Ligand Model (BLM). Data from open and restricted pore DGT units indicate that almost all dissolved metal species are inorganic and that aqueous labile or DGT available metal concentrations are generally equal to total dissolved concentrations in the mixing zone. Exceptions occur when labile metal concentrations are underestimated due to competition between H+ and metal ions for Chelex-100 binding sites in the DGT units at low pH values. Calculations using the BLM indicate that dissolved Cd and Zn species in the mixing and reaction zone are predominantly inorganic, which is consistent with the DGT results. Although the DGT method indicates that the majority of aqueous Cu species are inorganic, BLM calculations indicate that dissolved Cu is inorganic at pH 5.5. Integrated dissolved labile concentrations of Cd, Cu and Zn in the mixing and reaction zone are compared to calculated acute toxicity concentrations (LC50 values) for fathead minnows (Pimephales promelas) (Cd, Cu and Zn) and water fleas (Ceriodaphnia dubia) (Cd and Cu) using the BLM, and to national recommended water quality criteria [i.e., criteria maximum concentration (CMC) and criterion continuous concentration (CCC)]. Observed labile concentrations of Cd and Zn are below LC50 values and CMC for Cd, but above CCC and CMC for Zn at sites <30 m downstream of the confluence. In contrast, labile Cu concentrations exceed LC50 values for the organisms as well as CCC and CMC at sites <30 m downstream of the confluence. These results suggest that environmental conditions at sites closest to the confluence of the river and acid-mine drainage should not support healthy aquatic organisms. ?? 2007 Elsevier Ltd. All rights reserved.

Balistrieri, L.S.; Seal, R.R., II; Piatak, N.M.; Paul, B.



SON 68 nuclear glass alteration kinetics between pH 7 and pH 11.5  

NASA Astrophysics Data System (ADS)

The effect of the pH was investigated on the mechanisms of SON 68 (R7T7-type) glass alteration under `saturation' conditions in order to delimit the pH range within which a stable, protective gel is formed. Static experiments were conducted at 90°C with an S/ V ratio of 50 cm-1 at various imposed pH values: 7, 8, 9.5, 10, 10.5, 11 and 11.5. An additional experiment was conducted with no restriction on the pH. The kinetic study showed that a protective gel formed in all the test media, although its stability was pH-dependent: at pH 11 or higher, the precipitation of a potassium and sodium aluminosilicate led to the degradation of the gel and the lose of its protective properties. This phenomenon resulted in renewed glass alteration, leading to complete and rapid degradation of the glass into alteration products. The aluminosilicate precipitation was found to be limited by the solubility of aluminum. Below pH 10, this type of secondary phase is unlikely to precipitate and the gel should remain stable. This study, based on thermodynamic and kinetic considerations, suggests that aqueous alteration of the French SON 68 nuclear glass results in the formation of a protective gel with long-term stability between pH 7 and pH 10.

Gin, S.; Mestre, J. P.



Dissolved carbonic anhydrase for enhancing post-combustion carbon dioxide hydration in aqueous ammonia  

SciTech Connect

Aqueous ammonia solvents that capture CO2 as ionic complexes of carbonates with ammonium have recently been advanced as alternatives to amine-based solvents due to their lower energy requirements for thermal regeneration. In ammonia based solvents, the hydration of CO2 to form bicarbonate may become a rate-limiting step as the CO2 loading increases and the resulting pH level of the solvent decreases. Variants of the enzyme carbonic anhydrase can accelerate the reversible hydration of CO2 to yield bicarbonate by more than 10(6)-fold. The possible benefit of bovine carbonic anhydrase (BCA) addition to solutions of aqueous ammonia to enhance CO2 hydration was investigated in semi-batch reactions within continuously stirred tank reactors or in a bubble column gas-liquid contactor. Adding 154 mg/liter of BCA to 2 M aqueous ammonia provided a 34.1% overall increase in the rate of CO2 hydration (as indicated by the production of [H+]) as the pH declined from 9.6 to 8.6 during sparging with a 15% CO2, 85% N-2 gas at a flow rate of 3 lpm. The benefits of adding BCA to enhance CO2 hydration were only discernable below similar to pH 9. The implications of the apparent pH limitations on the utility of BCA are discussed in the context of absorber unit operation design. Possible embodiments of carbonic anhydrase as either an immobilized catalyst or as a dissolved, recirculating catalyst in potential plant scale aqueous ammonia systems are considered as well. (C) 2010 Published by Elsevier Ltd.

Collett, James R.; Heck, Robert W.; Zwoster, Andy



Growth limitation of three Arctic sea ice algal species: effects of salinity, pH, and inorganic carbon availability  

Microsoft Academic Search

The effect of salinity, pH, and dissolved inorganic carbon (TCO2) on growth and survival of three Arctic sea ice algal species, two diatoms (Fragilariopsis nana and Fragilariopsis sp.), and one species of chlorophyte (Chlamydomonas sp.) was assessed in controlled laboratory experiments. Our results suggest that the chlorophyte and the two diatoms have\\u000a different tolerance to fluctuations in salinity and pH.

Dorte Haubjerg SøgaardPer; Per Juel Hansen; Søren Rysgaard; Ronnie Nøhr Glud



Esophageal pH monitoring  


pH monitoring - esophageal; Esophageal acidity test ... to stay in the hospital for the esophageal pH monitoring. ... Esophageal pH monitoring is used to check how much stomach acid is entering the esophagus. It also checks how ...


The pH scale  

NSDL National Science Digital Library

Some animals tolerate broad changes in pH well while others do not. Human activities can create acid rain. Acid rain can change the pH of the environment and destroy entire ecosystems and habitats. For an ecosystem to function properly, its pH must be able to accommodate all of the organisms living in it.

Olivia Worland (Purdue University;Biological Sciences)



Soil redox and pH effects on methane production in a flooded rice soil  

Microsoft Academic Search

Methane formation in soil is a microbiological process controlled by many factors. Of them soil redox potential (Eh) and soil pH are considered as critical controls. A laboratory incubation experiment was conducted to study the critical initiation soil Eh, the optimum soil pH, and the interaction of Eh and pH on methane production. A small decrease in pH resulting from

Z. P. Wang; R. D. DeLaune; P. H. Masscheleyn; W. H. Patrick



The Effect of pH on Nickel Alloy SCC and Corrosion Performance  

Microsoft Academic Search

Alloy X-750 condition HTH stress corrosion crack growth rate (SCCGR) tests have been conducted at 360 C (680 F) with 50 cc\\/kg hydrogen as a function of coolant pH. Results indicate no appreciable influence of pH on crack growth in the pH (at 360 C) range of â 6.2 to 8.7, consistent with previous alloy 600 findings. These intermediate pH

D. S. Morton; M. Hansen



Effect of pH and chloride on nitrite-induced lethality in bluegill ( Lepomis macrochirus )  

Microsoft Academic Search

Experiments were conducted to evaluate the combined effects of hydrogen ion and chloride concentrations on nitrite toxicity in bluegill (Lepomis macrochirus). Our working hypotheses proposed (1) no chloride amelioration of nitrite toxicity at low pH, (2) significant toxicity reduction at high pH and (3) increased nitrite toxicity in all groups at low pH relative to neutral pH.

D. W. Huey; M. C. Wooten; L. A. Freeman; T. L. Beitinger



Effect of pH and chloride on nitrite-induced lethality in bluegill (Lepomis macrochirus)  

SciTech Connect

Experiments were conducted to evaluate the combined effects of hydrogen ion and chloride concentrations on nitrite toxicity in bluegill (Lepomis macrochirus). Our working hypotheses proposed (1) no chloride amelioration of nitrite toxicity at low pH, (2) significant toxicity reduction at high pH and (3) increased nitrite toxicity in all groups at low pH relative to neutral pH.

Huey, D.W.; Wooten, M.C.; Freeman, L.A.; Beitinger, T.L.



Calcium and pH in north and central Swedish mire waters  

Microsoft Academic Search

Summary 1 We present data on calcium concentrations and pH in mire waters collected from different mire types in central and northern Sweden, compiled from published literature or calculated from field determinations of electrical conductivity and pH. 2 Measurements of electrical conductivity (after subtracting that of H + ions) were used to calculate the most probable Ca concentrations, but only

H. Sjors; U. Gunnarsson



Role of Hydrous Iron Oxide Formation in Attenuation and Diel Cycling of Dissolved Trace Metals in a Stream Affected by Acid Rock Drainage  

Microsoft Academic Search

Mining-impacted streams have been shown to undergo diel (24-h) fluctuations in concentrations of major and trace elements.\\u000a Fisher Creek in south-central Montana, USA receives acid rock drainage (ARD) from natural and mining-related sources. A previous\\u000a diel field study found substantial changes in dissolved metal concentrations at three sites with differing pH regimes during\\u000a a 24-h period in August 2002. The

Stephen R. Parker; Christopher H. Gammons; Clain A. Jones; David A. Nimick



Dissolved Oxygen in Allen CreekDissolved Oxygen in Allen Creek Dissolved oxygen (DO) enters the water by diffusion from air, as a by-product of photosynthesis and  

E-print Network

Dissolved Oxygen in Allen CreekDissolved Oxygen in Allen Creek Dissolved oxygen (DO) enters and rapids. There is an inverse relationship between temperature and DO, i.e. colder water holds more oxygen it supplies oxygen to aquatic organisms. Higher DO levels also give the water a better taste. Figure 2. During

Tyler, Christy


Dissolved organic matter release and retention in ultisols in relation to land use patterns.  


The application of organic fertilizer to maintain soil fertility and crop yield has been practiced for thousands of years in China. This practice improves soil carbon sequestration, due to the high level of dissolved organic matter (DOM) in organic manure. In this study, batch equilibrium studies were conducted to examine the capacity of three ultisols from areas under different land use patterns to retain dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) extracted from rape cake and chicken manure. The results showed that the amount of DOM removed or released in solution by the soil was a linear function of the initial amount added to the soil-water system; therefore, analysis of sorption isotherms was best conducted using the initial mass isotherm IM method. The ultisol retained, on average, 19.9% of the total DOC and 41.7% of the total DON in solution, suggesting that ultisol has a relatively low DOC adsorption capacity. The ultisol from a bamboo forest was found to have a higher capacity than that from a pear orchard to retain DOC and DON. The adsorption affinities of DOM according to soil type were in the following order: bamboo forest (BF)>tea garden (TG)>pear orchard (PO). These results suggested that the continuous application of high doses of organic manure, particularly rape cake, may saturate the DOC adsorptive sites, thereby permitting increased leaching of DOC and the possibility of ground water contamination. Furthermore, we note that amorphous Fe and Al oxides play an important role in the adsorption capacity of both DOC and DON in ultisols. PMID:24704143

Zhang, Qichun; Hou, Changping; Liang, Yingying; Feng, Ying



Seasonal variability of dissolved organic carbon and total dissolved nitrogen in Arctic streams and rivers  

NASA Astrophysics Data System (ADS)

Changes in the quantity, seasonality, and flow paths of water through catchments have been documented throughout much of the Arctic, with further changes projected to occur over the coming century due to increasing temperatures and altered precipitation regimes. These changes in hydrology are expected to have a significant impact on biogeochemical cycles in Arctic watersheds. An improved understanding of the controls that impact water chemistry in Arctic rivers under varying hydrologic conditions will help to better project how these systems may respond to anticipated climate change. During 2009 and 2010, we collected surface waters from six streams on the North Slope of Alaska from mid-May through mid-October. The catchments of all six streams are underlain by continuous permafrost and range in size from 1.6 km2 to 610 km2. Three of the catchments drain predominantly tussock tundra while the other three are located in more mountainous terrain with exposed bedrock and less tundra coverage. This presentation will focus on the seasonality of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) in these streams. As observed in previous studies, DOC concentrations are highest during the spring snowmelt period and decline as the summer progresses. Concentrations of TDN show similar patterns to those of DOC during the spring and early summer. However, the pattern for TDN diverges from that of DOC later in the summer, with a substantial increase at some locations that is primarily attributed to the nitrate fraction. While the seasonal patterns are qualitatively similar in the tundra and mountain streams, DOC concentrations are much higher in the tundra streams and nitrate concentrations are much higher in the mountain streams. Our study places particular emphasis on dynamics during the spring and fall. Historically, these are times of the year that Arctic streams and rivers have been understudied. However, these are also times when the anticipated responses to warming in the Alaskan Arctic are most likely to be manifest: an earlier spring melt transition from winter to summer and the downward movement of the seasonally thawed “active” layer. During the spring, frozen ground largely constrains water flow to the organic-rich soil surface, whereas maximum thaw depths (active layer) in the fall facilitate water flow thorough deeper soil layers.

Khosh, M. S.; McClelland, J. W.; Douglas, T. A.; Jacobson, A. D.; Lehn, G. O.; Barker, A.



Ocean metabolism and dissolved organic matter: How do small dissolved molecules persist in the ocean?  

NASA Astrophysics Data System (ADS)

The ocean reservoir of dissolved organic matter (DOM) is among the largest global reservoirs (~700 Pg C) of reactive organic carbon. Marine primary production (~50 Pg C/yr) by photosynthetic microalgae and cyanobacteria is the major source of organic matter to the ocean and the principal substrate supporting marine food webs. The direct release of DOM from phytoplankton and other organisms as well as a variety of other processes, such as predation and viral lysis, contribute to the ocean DOM reservoir. Continental runoff and atmospheric deposition are relatively minor sources of DOM to the ocean, but some components of this material appear to be resistant to decomposition and to have a long residence time in the ocean. Concentrations of DOM are highest in surface waters and decrease with depth, a pattern that reflects the sources and diagenesis of DOM in the upper ocean. Most (70-80%) marine DOM exists as small molecules of low molecular weight (<1 kDalton). Surprisingly, high-molecular-weight (>1 kDalton) DOM is relatively enriched in major biochemicals, such as combined neutral sugars and amino acids, and is more bioavailable than low-molecular-weight DOM. The observed relationships among the size, composition, and reactivity of DOM have led to the size-reactivity continuum model, which postulates that diagenetic processes lead to the production of smaller molecules that are structurally altered and resistant to microbial degradation. The radiocarbon content of these small dissolved molecules also indicates these are the most highly aged components of DOM. Chemical signatures of bacteria are abundant in DOM and increase during diagenesis, indicating bacteria are an important source of slowly cycling biochemicals. Recent analyses of DOM isolates by ultrahigh-resolution mass spectrometry have revealed an incredibly diverse mixture of molecules. Carboxyl-rich alicyclic molecules are abundant in DOM, and they appear to be derived from diagenetically-altered terpenoids, such as sterols and hopanoids. Thermally-altered molecules, including black carbon, also appear to be important components of DOM, but their origins are unclear. We are rapidly acquiring novel information about the composition and molecular identity of DOM, and novel insights about the origins, transformations and fates this vast reservoir of DOM are emerging. This presentation will review and synthesize this information for comparison with non-living organic matter in other systems.

Benner, Ronald



Chapter 3 -Basic Water Quality in the Boulder Creek Watershed, Colorado, During High-Flow and Low-Flow Conditions, 2000  

E-print Network

, organic nitrogen, orthophosphate, pH, specific conductance, temperature, total dissolved solids, total constituents. The Stormwater program samples waters that contain higher levels of dissolved and suspended


The Influence of Redox Reactions on the Uptake of Dissolved Ce by Suspended Fe and Mn Oxide Particles  

Microsoft Academic Search

Laboratory experiments were conducted to evaluate the partitioning ofrare earth elements (REE) between solution and suspended\\u000a particles. Becauseof their strong tendency to complex, the REE can be used to study a varietyof marine processes and in particular\\u000a particle scavenging. In this study, anemphasis was placed on examining abiotic redox processes that influence theuptake of\\u000a dissolved Ce by particles. Batch sorption

Eric Heinen De Carlo; Xi-Yuan Wen; Mark Irving



The Effect of Natural Dissolved Organic Carbon on the Acute Toxicity of Copper to Larval Freshwater Mussels (Glochidia)  

Microsoft Academic Search

The present study examined the effect of dissolved organic carbon (DOC), both added and inherent, on Cu toxicity in glochidia, the larvae of freshwater mussels. Using incremental additions of natural DOC concentrate and reconstituted water, a series of acute copper toxicity tests were conducted. An increase in DOC from 0.7 to 4.4 mg C\\/L resulted in a fourfold increase (36–150

Patricia L. Gillis; James C. McGeer; Gerald L. Mackie; Michael P. Wilkie; Josef D. Ackerman



Quantification of dissolved iron sources to the North Atlantic Ocean  

NASA Astrophysics Data System (ADS)

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

Conway, Tim M.; John, Seth G.



Scavenging rates of dissolved manganese in a hydrothermal vent plume  

NASA Astrophysics Data System (ADS)

The biogeochemical scavenging of dissolved manganese (Mn) from hydrothermal plumes was investigated using radiotracer ( 54Mn) techniques. The measured scavenging rate constant, k 1, was lowest in the buoyant plume (<0.2 y -1), increasing to ˜2 y -1 in the non-buoyant plume at distances of 20 km from the ridge valley axis. The direct biological contribution to the dissolved Mn scavenging rate (i.e the fraction suppressed by the addition of a metabolic poison) also increased over the same distances, being minor or absent at plume depths in the proximal plume, yet the major component at distal plume stations. These and other data suggest that the capacity for scavenging dissolved Mn onto particles evolves with increasing age of the plume, suggestive of a microbial response to changing conditions within the plume. Estimated maximum scavenging rates of dissolved Mn onto particles ( RDMn = k 1 [DMn])were noted at plume depths for all stations, a function of very high dissolved Mn concentrations in the case of the buoyant plume and proximal non-buoyant plume. RDMn values, integrated over plume depths, ranged from 3.4 to 1.7 mM m -2 y -1 for the non-buoyant plume at on-axis and off-axis stations, respectively. The application of the data to the dispersal of hydrothermal constituents and to plume aging is discussed.

Cowen, James P.; Massoth, Gary J.; Feely, Richard A.



Effect of membrane filtration artifacts on dissolved trace element concentrations  

USGS Publications Warehouse

Among environment scientists, the current and almost universally accepted definition of dissolved constituents is an operational one; only those materials which pass through a 0.45-??m membrane filter are considered to be dissolved. Detailed laboratory and field studies on Fe and Al indicate that a number of factors associated with filtration, other than just pore size, can substantially alter 'dissolved' trace element concentrations; these include: filter type, filter diameter, filtration method, volume of sample processed, suspended sediment concentration, suspended sediment grain-size distribution, concentration of colloids and colloidally associated trace elements and concentration of organic matter. As such, reported filtered-water concentrations employing the same pore size filter may not be equal. Filtration artifacts may lead to the production of chemical data that indicate seasonal or annual 'dissolved' chemical trends which do not reflect actual environmental conditions. Further, the development of worldwide averages for various dissolved chemical constituents, the quantification of geochemical cycles, and the determination of short- or long-term environmental chemical trends may be subject to substantial errors, due to filtration artifacts, when data from the same or multiple sources are combined. Finally, filtration effects could have a substantial impact on various regulatory requirements.

Horowitz, Arthur J.; Elrick, Kent A.; Colberg, Mark R.



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

USGS Publications Warehouse

Diel (24-h) changes in concentrations of rare earth elements (REE) were investigated in Fisher Creek, a mountain stream in Montana that receives acid mine drainage in its headwaters. Three simultaneous 24-h samplings were conducted at an upstream station (pH = 3.3), an intermediate station (pH = 5.5), and a downstream station (pH = 6.8). The REE were found to behave conservatively at the two upstream stations. At the downstream station, REE partitioned into suspended particles to a degree that varied with the time of day, and concentrations of dissolved REE were 2.9- to 9.4-fold (190% to 830%) higher in the early morning vs. the late afternoon. The decrease in dissolved REE concentrations during the day coincided with a corresponding increase in the concentration of REE in suspended particles, such that diel changes in the total REE concentrations were relatively minor (27% to 55% increase at night). Across the lanthanide series, the heavy REE partitioned into the suspended solid phase to a greater extent than the light REE. Filtered samples from the downstream station showed a decrease in shale-normalized REE concentration across the lanthanide series, with positive anomalies at La and Gd, and a negative Eu anomaly. As the temperature of the creek increased in the afternoon, the slope of the REE profile steepened and the magnitude of the anomalies increased. The above observations are explained by cyclic adsorption of REE onto suspended particles of hydrous ferric and aluminum oxides (HFO, HAO). Conditional partition coefficients for each REE between the suspended solids and the aqueous phase reached a maximum at 1700 hours and a minimum at 0700 hours. This pattern is attributed to diel variations in stream temperature, possibly reinforced by kinetic factors (i.e., slower rates of reaction at night than during the day). Estimates of the enthalpy of adsorption of each REE onto suspended particles based on the field results averaged +82 kJ/mol and are similar in magnitude to estimates in the literature for adsorption of divalent metal cations onto clays and hydrous metal oxides. The results of this study have important implications to the use of REE as hydrogeochemical tracers in streams. Copyright ?? 2005 Elsevier Ltd.

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



Seasonal ice and hydrologic controls on dissolved organic carbon and nitrogen concentrations in a borealrich fen  

E-print Network

Seasonal ice and hydrologic controls on dissolved organic carbon and nitrogen concentrations and hydrologic controls on dissolved organic carbon and nitrogen concentrations in a borealrich fen, J. Geophys of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) across an experimental manipulation

Turetsky, Merritt


Effect of pH alkaline salts of fatty acids on the inhibition of bacteria associated with poultry processing  

Technology Transfer Automated Retrieval System (TEKTRAN)

The agar diffusion assay was used to examine the effect of pH on the ability of alkaline salts of three fatty acids (FA) to inhibit growth of bacteria associated with poultry processing. FA solutions were prepared by dissolving 0.5 M concentrations of caprylic, capric, or lauric acid in separate ali...


Iron traps terrestrially derived dissolved organic matter at redox interfaces  

PubMed Central

Reactive iron and organic carbon are intimately associated in soils and sediments. However, to date, the organic compounds involved are uncharacterized on the molecular level. At redox interfaces in peatlands, where the biogeochemical cycles of iron and dissolved organic matter (DOM) are coupled, this issue can readily be studied. We found that precipitation of iron hydroxides at the oxic surface layer of two rewetted fens removed a large fraction of DOM via coagulation. On aeration of anoxic fen pore waters, >90% of dissolved iron and 27 ± 7% (mean ± SD) of dissolved organic carbon were rapidly (within 24 h) removed. Using ultra-high-resolution MS, we show that vascular plant-derived aromatic and pyrogenic compounds were preferentially retained, whereas the majority of carboxyl-rich aliphatic acids remained in solution. We propose that redox interfaces, which are ubiquitous in marine and terrestrial settings, are selective yet intermediate barriers that limit the flux of land-derived DOM to oceanic waters. PMID:23733946

Riedel, Thomas; Zak, Dominik; Biester, Harald; Dittmar, Thorsten



Dissolved mercury behaviour in the Saint Lawrence estuary  

NASA Astrophysics Data System (ADS)

Dissolved mercury concentrations have been measured in the waters of the St Lawrence estuary. The typical concentration of the riverine end-member is 12·0±3·0 p M; the oceanic end-member samples exhibit a mean mercury concentration of 2·4 p M. The graphical pattern of the relationship between mercury concentration and salinity shows a departure from a dilution line. We suggest that a removal of mercury from the dissolved phase during the estuarine mixing is responsible for this observation. Based on the results, the actual input of dissolved mercury from the St Lawrence River to the Gulf is evaluated to be approximately 0·52 T a -1.

Cossa, Daniel; Gobeil, Charles; Courau, Philippe



Effects of dissolved organic matter from a eutrophic lake on the freely dissolved concentrations of emerging organic contaminants.  


The authors studied the effects of dissolved organic matter (DOM) on the bioavailability of bisphenol A (BPA) and chloramphenicol by measuring the freely dissolved concentrations of the contaminants in solutions containing DOM that had been isolated from a mesocosm in a eutrophic lake. The abundance and aromaticity of the chromophoric DOM increased over the 25-d mesocosm experiment. The BPA freely dissolved concentration was 72.3% lower and the chloramphenicol freely dissolved concentration was 56.2% lower using DOM collected on day 25 than using DOM collected on day 1 of the mesocosm experiment. The freely dissolved concentrations negatively correlated with the ultraviolent absorption coefficient at 254 nm and positively correlated with the spectral slope of chromophoric DOM, suggesting that the bioavailability of these emerging organic contaminants depends on the characteristics of the DOM present. The DOM-water partition coefficients (log KOC ) for the emerging organic contaminants positively correlated with the aromaticity of the DOM, measured as humic acid-like fluorescent components C1 (excitation/emission=250[313]/412 nm) and C2 (excitation/emission=268[379]/456 nm). The authors conclude that the bioavailability of emerging organic contaminants in eutrophic lakes can be affected by changes in the DOM. PMID:24839192

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



Dissolved gas concentrations of the geothermal fluids in Taiwan  

NASA Astrophysics Data System (ADS)

Taiwan, a geologically active island, is located on the boundary of the Philippine Sea Plate and the Eurasian Plate. High heat flow and geothermal gradient generated by the complex collision and orogeny, warm up the meteoric water and/or the ground water. The heated water becomes geothermal fluids. In previous studies, researchers tried to categorize hot springs based on the appearance, chemical compositions and lithological areas. Because of the chemical inertness, the concentrations and isotopic composition of dissolved noble gases are good indicators of the mantle degassing, geothermal conditions, and so on. In this study, 55 hot springs were collected from different tectonic units. It is the first time to systematically study the hot springs in Taiwan in terms of dissolved gases. Hot spring water is sampled and stored in pre-evacuated glass bottles for analyzing gas compositions. The abundances of noble gases were determined by a quadrupole mass spectrometer based on the isotope dilution technique. Samples with glass vials are introduced to RAD 7 and GC for dissolved Rn and major dissolved gases analyses. Furthermore, helium isotopic ratios and helium-neon ratios are measured on a conventional noble gas mass spectrometer. For hydrochemistry analysis, water samples are analyzed by IC, ICP-MS and titration. We can classify the hot springs samples into three major groups from main anion concentration data; and then, subdivide them into nine minor groups by cation concentration data. Moreover, according to major dissolved gases compositions, three major gas components: CH4, N2 and CO2, are identified. Dissolved noble gases provided more detailed clues about hot springs sources in Taiwan, such as the degree of mixing between meteoric water and deep-source water, which will be further discussed in this study.

Chen, Ai-Ti; Yang, Tsanyao Frank



Influence of temperature and dissolved oxygen on the acute toxicity of profenofos to fathead minnows (Pimephales promelas).  


The purpose of this study was to investigate the influence of temperature and dissolved oxygen levels on the acute toxicity of profenofos to fathead minnows (Pimephales promelas). Exposure conditions were as follows: normal temperature and normal dissolved oxygen (NTNO; 20 +/- 2 degrees C and 6.0-9.0 mg/L, respectively); normal temperature and low dissolved oxygen (NTLO; 20 +/- 2 degrees C and 1.7-2.6 mg/L, respectively); high temperature and normal dissolved oxygen (HTNO; 30 +/- 2 degrees C and 6.6-6.9 mg/L, respectively); high temperature and low dissolved oxygen (HTLO; 30 +/- 2 degrees C and 1.5-3.0 mg/L, respectively). Initial 96-h acute toxicity studies with profenofos were conducted at NTNO and HTLO exposure conditions. The 96-h LC50 at NTNO was 333 micrograms/L with 95% confidence limits ranging from 244 to 558 micrograms/L. However, the 96-h LC50 at HTLO was significantly lower at 21.5 micrograms/L with 95% confidence limits ranging from 17.4 to 28.8 micrograms/L. Acetylcholinesterase (AChE) activity was measured in the head and torso of surviving fish at 96-h. A weak dose-related decrease in AChE was observed at NTNO but no dose-response relationship was observed at HTLO exposure condition. Additional experiments were conducted using 50 micrograms/L profenofos at NTNO, NTLO, HTNO, and HTLO exposure conditions. Mortality, sublethal effects (erratic and hyperactive swimming), and AChE activity in the head and torso were measured at 2, 4, and 12-h following exposure to profenofos. No mortality or significant sublethal effects were observed in controls or profenofos-treated groups in NTNO and NTLO exposure conditions. However, significant mortality and sublethal effects were observed in profenofos-treated fish in HTNO at 12 h and at all time points in HTLO. Both high temperature and low dissolved oxygen, as well as combinations of high temperature and low dissolved oxygen significantly decreased AChE activity in control fish. Exposure to 50 micrograms/L profenofos in all exposure conditions further decreased AChE activity, but no apparent correlations between mortality and AChE activity were observed. These results suggest that the acute toxicity of profenofos to fathead minnows may be exacerbated during summer conditions in southern U.S. aquatic ecosystems. PMID:12173245

Baer, K N; Olivier, K; Pope, C N



Simulation Analysis for HB-Line Dissolver Mixing  

SciTech Connect

In support of the HB-Line Engineering agitator mixing project, flow pattern calculations have been made for a 90{sup o} apart and helical pitch agitator submerged in a flat tank containing dissolver baskets. The work is intended to determine maximum agitator speed to keep the dissolver baskets from contacting the agitator for the nominal tank liquid level. The analysis model was based on one dissolver basket located on the bottom surface of the flat tank for a conservative estimate. The modeling results will help determine acceptable agitator speeds and tank liquid levels to ensure that the dissolver basket is kept from contacting the agitator blade during HB-Line dissolver tank operations. The numerical modeling and calculations have been performed using a computational fluid dynamics approach. Three-dimensional steady-state momentum and continuity equations were used as the basic equations to estimate fluid motion driven by an agitator with four 90{sup o} pitched blades or three flat blades. Hydraulic conditions were fully turbulent (Reynolds number about 1 x 10{sup 5}). A standard two-equation turbulence model ({kappa},{var_epsilon}), was used to capture turbulent eddy motion. The commercial finite volume code, Fluent [5], was used to create a prototypic geometry file with a non-orthogonal mesh. Hybrid meshing was used to fill the computational region between the round-edged tank bottom and agitator regions. The nominal calculations and a series of sensitivity runs were made to investigate the impact of flow patterns on the lifting behavior of the dissolver basket. At high rotational speeds and low tank levels, local turbulent flow reaches the critical condition for the dissolver basket to be picked up from the tank floor and to touch the agitator blades during the tank mixing operations. This is not desirable in terms of mixing performance. The modeling results demonstrate that the flow patterns driven by the agitators considered here are not strong enough to lift up the dissolver basket for the agitator speeds up to 2500 rpm. The results also show that local velocity magnitudes for the three-blade flat plate agitator are at maximum three times smaller than the helical fourblade one. Table 5 and Table 6 summarize the results.

Lee, S



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

SciTech Connect

This report summarizes the work conducted under ICRC's Program Area 12.1.7, on the effects of staged vessels on dissolver performance. Results showed that operating the dissolvers in series decreased the preasphaltenes yield. From a process viewpoint, this should increase the amount of recoverable product, because recovery from the plant's critical solvent deashing unit will increase when preasphaltene content decreases. Neither conversion nor oil, asphaltene, or gas yields were affected by reactor configuration. Process data taken at residence times from 20 to 60 min and temperatures from 780 to 840/sup 0/F showed that oil yields were directly affected by reaction time, but relatively insensitive to temperature. Operating the dissolvers at staged temperatures may have some potential advantages. For Lafayette Kentucky number 9 coal, operating the first dissolver at 810/sup 0/F and the second at 840/sup 0/F, agreed with the results observed under similar conditions on Lafayette coal. By operating the first reactor at a lower temperature, the oil yields were improved, compared to operating both reactors at the same temperature. The hydrocarbon gas yields and hydrogen consumption were lower in the staged-temperature than in the isothermal mode. 8 references, 9 figures, 26 tables.

Sivasubramanian, R.; Givens, E.N.



Structural properties of dissolved organic carbon in deep soil horizons of an arable and temporarily grassland.  

NASA Astrophysics Data System (ADS)

It is commonly accepted that dissolved organic carbon (DOC) is the bio-available fraction of the largest amount of soil organic matter (SOM), even if it does represent only a very small proportion. Because most of the studies on DOC dynamics were mainly restricted to forest soils, studies on the factors governing the dynamics of DOC in deep soil horizons (>1 m) in arable system are still very little limited. The objective of this work is to better define the proportion of DOC in deep soil horizons and indicate their main characteristics and structural properties. The study was conducted on the long term observatory for environmental research- biogeochemical cycles and biodiversity Lusignan site). DOC collected using lysimeters plates inserted to a depth of 105 cm was fractionated into 3 fractions using the two column array of XAD-8 and XAD-4 resins. The HPO (hydrophobic) fraction (i.e. humic substances) isolated from the XAD-8 resin, the TPH (Transphilic) fraction from the XAD-4 resin and the HPI (hydrophilic) fraction which corresponds to the DOC that does not adsorbed onto the two resins under the acid condition used (pH 2). DOM adsorbed onto the resins is recovered with a 75%/25% acetonitrile/water mixture and lyophilized. Depend on the amount of material; the chemical composition of DOC was performed using UV254 nm, fluorescence EEM, NMR and HPSEC/UV/COD. The results show that the concentration and structural properties of DOC in deep soil horizon were similar to those of groundwater (low SUVA (1.2 C-1), structures composed mainly of low molecular weight). Because of the relatively recent establishment of the treatment, the monitoring of the dynamics of the DOC concentrations did not show significant differences between arable and grassland. However, the temporal dynamic shows a slight increase in the DOC content regardless of the of land use. DOC concentrations between winter and the middle of spring tend to double going from 1 to 2.5 mg / L and then to 4-5 mg / L in summer time. The structural analysis reveals significant input of terpenoid derived organic matter was confirmed in the HPO fraction of DOC a results supported by the data of 13C NMR, Infra Red and Micro Scale Sealed Vessel / pyrolysis GC / MS. The chromatographic profiles obtained by flash pyrolysis GC / MS highlight the presence of phenol and alkyl phenols, generally attributed to structures polyhydroxyaromatiques (lignin / tannins), but acetamide, pyrolysis product of amino sugars constituents of the wall microbial cells. The thermochimiolyse (TMAH) / GC / MS confirmed the presence of hydroxy aromatic structures in the extracts, however, their precise origin (lignin, tannins ...) remains uncertain. The results so far indicate that the DOC in deep soil horizons is marked by low aromaticity and dominated by small size molecules. This would consist of carbon derived from terpenoids, lignin degraded and amino sugars.

Lavaud, A.; Chabbi, A.; Croue, J. P.



Dissolved organic carbon (DOC) in soil extracts investigated by FT-ICR-MS  

NASA Astrophysics Data System (ADS)

Soil drying and rewetting usually increases the release of xenobiotics like pesticides present in agricultural soils. Besides the effect on the release of two aged 14C-labeled pesticide residues we focus on the characterisation of simultaneously remobilized dissolved organic carbon (DOC) to gain new insights into structure and stability aspects of soil organic carbon fractions. The test soil (gleyic cambisol; Corg 1.2%, pH 7.2) was obtained from the upper soil layer of two individual outdoor lysimeter studies containing either environmentally long-term aged 14C residues of the herbicide ethidimuron (0-10 cm depth; time of aging: 9 years) or methabenzthiazuron (0-30 cm depth; time of aging: 17 years). Soil samples (10 g dry soil equivalents) were (A=dry/wet) previously dried (45°C) or (B=wet/wet) directly mixed with pure water (1+2, w:w), shaken (150 rpm, 1 h), and centrifuged (2000 g). This extraction procedure was repeated several individual times, for both setups. The first three individual extractions, respectively were used for further investigations. Salt was removed from samples prior analysis because of a possible quench effect in the electrospray (ESI) source by solid phase extraction (SPE) with Chromabond C18 Hydra-cartridges (Macherey-Nagel) and methanol as backextraction solvent. The so preconcentrated and desalted samples were introduced by flow injection analysis (FIA) in a fourier transform ion cyclotron resonance mass spectrometer (FT-ICR-MS), equipped with an ESI source and a 7 T supra-conducting magnet (LTQ-FT Ultra, ThermoFisher Scientific). This technique is the key technique for complex natural systems attributed by their outstanding mass resolution (used 400.000 at m/z 400 Da) and mass accuracy (? 1ppm) by simultaneously providing molecular level details of thousands of compounds and was successful applied for the investigations of natural organic matter (NOM) different sources like marine and surface water, soil, sediment, bog and crude oil. The characteristics of measured DOM mass spectra were demonstrated. Furthermore, an algorithm to compute all chemically relevant C,H,O-, C,H,(O,S),N- as well as C,H,(O),S molecular compositions, designed and exercised by ourself using Scilab routines, was used for entire structure elucidation. Various methods for data evaluation of such an amount of peaks are applied to describe the characteristics of DOC. The van Krevelen diagram is widely used to classify the DOC compounds regarding polarity and aromaticity, whereas the Kendrick diagram allow to identify ions with elemental formulas that differ only in CH2, and molecular formulas with similar Kendrick Mass Defect (KMD) can be sorted by nominal mass series. Both kind of diagrams were developed and results are discussed together with the findings of ETD, MBT, and metabolites after soil drying and rewetting. Overall, the results suggest that intermittent soil drying and rewetting alters the disaggregation of soil aggregates, resulting in a release of entrapped organic carbon as well as pesticide molecules.

Hofmann, D.; Steffen, D.; Jablonowski, N. D.; Burauel, P.



Response surface modeling for optimization heterocatalytic Fenton oxidation of persistence organic pollution in high total dissolved solid containing wastewater.  


The rice-husk-based mesoporous activated carbon (MAC) used in this study was precarbonized and activated using phosphoric acid. N2 adsorption/desorption isotherm, X-ray powder diffraction, electron spin resonance, X-ray photoelectron spectroscopy and scanning electron microscopy, transmission electron microscopy, (29)Si-NMR spectroscopy, and diffuse reflectance spectroscopy were used to characterize the MAC. The tannery wastewater carrying high total dissolved solids (TDS) discharged from leather industry lacks biodegradability despite the presence of dissolved protein. This paper demonstrates the application of free electron-rich MAC as heterogeneous catalyst along with Fenton reagent for the oxidation of persistence organic compounds in high TDS wastewater. The heterogeneous Fenton oxidation of the pretreated wastewater at optimum pH (3.5), H2O2 (4 mmol/L), FeSO4[Symbol: see text]7H2O (0.2 mmol/L), and time (4 h) removed chemical oxygen demand, biochemical oxygen demand, total organic carbon and dissolved protein by 86, 91, 83, and 90%, respectively. PMID:23925658

Sekaran, G; Karthikeyan, S; Boopathy, R; Maharaja, P; Gupta, V K; Anandan, C



Effects of dissolved organic carbon and salinity on bioavailability of mercury.  

PubMed Central

Hypotheses that dissolved organic carbon (DOC) and electrochemical charge affect the rate of methylmercury [CH3Hg(I)] synthesis by modulating the availability of ionic mercury [Hg(II)] to bacteria were tested by using a mer-lux bioindicator (O. Selifonova, R. Burlage, and T. Barkay, Appl. Environ. Microbiol. 59:3083-3090, 1993). A decline in Hg(II)-dependent light production was observed in the presence of increasing concentrations of DOC, and this decline was more pronounced at pH 7 than at pH 5, suggesting that DOC is a factor controlling the bioavailability of Hg(II). A thermodynamic model (MINTEQA2) was used to select assay conditions that clearly distinguished among various Hg(II) species. By using this approach, it was shown that negatively charged forms of mercuric chloride (HgCl3-/HgCl(4)2-) induced less light production than the electrochemically neutral form (HgCl2), and no difference was observed between the two neutral forms, HgCl2 and Hg(OH)2. These results suggest that the negative charge of Hg(II) species reduces their availability to bacteria and may be one reason why accumulation of CH3Hg(I) is more often reported to occur in freshwater than in estuarine and marine biota. PMID:9361413

Barkay, T; Gillman, M; Turner, R R



Increases in dissolved organic carbon accelerate loss of toxic Al in Adirondack lakes recovering from acidification.  


Increasing pH and decreasing Al in surface waters recovering from acidification have been accompanied by increasing concentrations of dissolved organic carbon (DOC) and associated organic acids that partially offset pH increases and complicate assessments of recovery from acidification. To better understand the processes of recovery, monthly chemistry from 42 lakes in the Adirondack region, NY, collected from 1994 to 2011, were used to (1) evaluate long-term changes in DOC and associated strongly acidic organic acids and (2) use the base-cation surplus (BCS) as a chemical index to assess the effects of increasing DOC concentrations on the Al chemistry of these lakes. Over the study period, the BCS increased (p < 0.01) and concentrations of toxic inorganic monomeric Al (IMAl) decreased (p < 0.01). The decreases in IMAl were greater than expected from the increases in the BCS. Higher DOC concentrations that increased organic complexation of Al resulted in a decrease in the IMAl fraction of total monomeric Al from 57% in 1994 to 23% in 2011. Increasing DOC concentrations have accelerated recovery in terms of decreasing toxic Al beyond that directly accomplished by reducing atmospheric deposition of strong mineral acids. PMID:23751119

Lawrence, Gregory B; Dukett, James E; Houck, Nathan; Snyder, Phil; Capone, Sue



Elementary PhUn Fair - PhUn Week Poster Session EB 2012  

NSDL National Science Digital Library

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

Pauline Schork (Clinton High School)



Electrical pH control in aqueous solutions  

NASA Astrophysics Data System (ADS)

This paper describes a method and instrumentation for electrical pH control in aqueous solutions. It is targeted to environmental and industrial on-line chemical and optic fiber sensors measurement, calibration and process control. The method is an alternative to the existing automatic pH controllers based on correction chemical addition. The on- line measurement of dissolved gaseous species which produce acidic and basic waters is of great concern for environmental monitoring applications. Such measurements are maintained by using preconditioned water samples and ion- selective electrodes or absorption spectrometry. A gas- permeable membrane can be used to allow only the transport of the molecular form of the measured species where the solution pH is controlled to ensure the reversible transition of the species of interest from ionic to molecular form and to allow their permeation through the membrane. An electrochemical instrument for electrolysis- based feedback controlled pH regulation has been attempted. The choice of galvanostatic, potentiostatic and combined methods of modulation electrodes biasing with their speed, settling time and accuracy are discussed. Different feedback control approaches, involving electrochemical and optical sensors, are compared.

Bourilkov, Jordan; Belz, Mathias; Boyle, William J. O.; Grattan, Kenneth T. V.



Dissolved Organic Matter Along a North South Transect of the Yenisei River  

NASA Astrophysics Data System (ADS)

The molecular composition of dissolved organic matter (DOM) contains important information on properties and processes like decomposition in terrestrial and aquatic systems. To explore the source characteristics of DOM in relation to environmental factors, tributaries and bogs along the Yenisei River between 56° N near Krasnoyarsk and 68° N at Khantayka River were sampled. This includes a transect of 1000 km across a climatic gradient with different vegetation zones and permafrost influence. The sampling took place in July and August 1998 during the one-month BOBCAT (Boat on a Boreal Carbon Tour) campaign of the Max Planck Institute for Biogeochemistry (Jena, Germany) and the Institute of Forest (Krasnoyarsk, Russia). After filtration with GF/F, the samples were freeze-dried for following analysis. To unravel the complexity of DOM in our samples on a molecular basis, we applied Electrospray Ionization Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry (ESI-FT-ICR-MS). For ESI-FT-ICR-MS freeze-dried material was re-dissolved and extracted by solid phase extraction (SPE) with Varian Bond Elute PPL according to Dittmar et al. 2008. The desalted samples were measured in negative ionization mode at the Bruker Solarix 15 T FT-ICR-MS at the University of Oldenburg (Germany). The data of the highly resolved and accurately calibrated masses was used to calculate the corresponding molecular formulas. Different multivariate statistical tools, like principal component analysis (PCA) in combination with environmental parameters, and graphical display methods are applied to the data to explore differences and similarities between samples and as well possible correlations with environmental parameters. In our contribution we show the results of our comparative study. Major outcomes are the correlation between molecular composition of DOM and environmental parameters like DOC concentration, pH and geographical latitude. We found, that the pH in water is a driving factor for the molecular composition of DOM. Since, DOM reflects decomposition processes in general, it is a fundamental finding that the molecular composition of DOM is dependent on the pH conditions.

Roth, V.; Dittmar, T.; Gaupp, R.; Gleixner, G.



Modeling CO2 degassing and pH in a stream-aquifer system  

USGS Publications Warehouse

Pinal Creek, Arizona receives an inflow of ground water with high dissolved inorganic carbon (57-75 mg/l) and low pH (5.8-6.3). There is an observed increase of in-stream pH from approximately 6.0-7.8 over the 3 km downstream of the point of groundwater inflow. We hypothesized that CO2 gas-exchange was the most important factor causing the pH increase in this stream-aquifer system. An existing transport model, for coupled ground water-surface water systems (OTIS), was modified to include carbonate equilibria and CO2 degassing, used to simulate alkalinity, total dissolved inorganic carbon (C(T)), and pH in Pinal Creek. Because of the non-linear relation between pH and C(T), the modified transport model used the numerical iteration method to solve the non-linearity. The transport model parameters were determined by the injection of two tracers, bromide and propane. The resulting simulations of alkalinity, C(T) and pH reproduced, without fitting, the overall trends in downstream concentrations. A multi-parametric sensitivity analysis (MPSA) was used to identify the relative sensitivities of the predictions to six of the physical and chemical parameters used in the transport model. MPSA results implied that C(T) and pH in stream water were controlled by the mixing of ground water with stream water and CO2 degassing. The relative importance of these two processes varied spatially depending on the hydrologic conditions, such as stream flow velocity and whether a reach gained or lost stream water caused by the interaction with the ground water. The coupled transport model with CO2 degassing and generalized sensitivity analysis presented in this study can be applied to evaluate carbon transport and pH in other coupled stream-ground water systems.An existing transport model for coupled groundwater-surface water systems was modified to include carbonate equilibria and CO2 degassing. The modified model was used to simulate alkalinity, total dissolved inorganic carbon (CT) and pH in Pinal Creek. The model used the numerical iteration method to solve the nonlinear relation between pH and CT. A multi-parametric sensitivity analysis (MPSA) was used to identify the relative sensitivities of the predictions to six of the physical and chemical parameters used in the transport model. MPSA results implied that CT and pH in the stream water were controlled by the mixing of groundwater with stream water and CO2 degassing.

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



Dissolved, Exsolved and Re-dissolved H2O in Volcanology: Rheology, Glass Transition, and Thermodynamics  

NASA Astrophysics Data System (ADS)

All natural magmas originate with dissolved H2O. All such magmas degas during transport and eruption. The presence, abundance, and state of H2O in magmas control phase relations and the transport properties of melts and magmas. For example, dissolved H2O lowers viscosity, lowers glass transition temperatures (Tg), and controls the temperature and nature of crystallization. The effects of exsolved water are also substantial in terms of modifying the bulk transport properties of the magma, facilitating egress of volatiles and, thus, promoting crystallization. Of great interest is the coupling this component (H2O) creates between the thermodynamic processes (i.e. cooling, crystallization, vesiculation) and the properties (i.e. density, viscosity) controlling the mechanical behaviour (i.e. flow and fracture) of magma during transport and eruption. The coupling allows for strong feedbacks between system variables. The component H2O also has a retrograde solubility in silicate melts wherein H2O solubility in the melt increases with decreasing T. Here, we explore some of the consequences of retrograde solubility of H2O for volcanic systems using a new preliminary experimental dataset. These data establish the 1-atmosphere solubility limits of H2O in silicic melt at volcanic temperatures and are complementary to the growing literature on the low pressure (<50 MPa) solubility of volatiles in silicate melts (e.g., Behrens et al. 2009; DiMatteo et al. 2004; Liu et al. 2005; Zhang 1999). We specifically look at the implications of these data, especially the retrograde solubility limits, for welding of pyroclastic deposits (e.g. ignimbrites, conduit fill, fall out). The cessation of welding and compaction processes in pyroclastic deposits is reached when deposits cool below Tg. However, the fact that H2O has a retrograde solubility means that inter- and intraclast water will be resorbed by vitric pyroclasts as the deposit cools (regardless of load). This has the immediate consequence of reducing the viscosity of the pyroclasts and, more importantly, reducing Tg. The reduction in pyroclast viscosity facilitates sintering, welding and compaction processes. The reduced Tg, due to resorbed H2O, extends the T-time window for porosity reduction via viscous flow. Variations in welding intensity can, therefore, be an expression of the competition between cooling of the deposit and the re-hydration of vitric pyroclasts during cooling driven by retrograde solubility of H2O. In essence, the temperature of the cooling deposit chases a descending Tg; once the deposit temperature catches and drops below Tg, viscous deformation processes are quenched. This allows for the H2O contents of vitric pyroclasts to preserve higher water contents that they had at the time they erupted. The analysis of the relationships between eruptive, emplacement and glass transition temperatures are discussed further. References Cited: Behrens H. et al. 2009: Am Min 94, 105-120. Di Matteo V. et al. 2004: Chemical Geology 213, 187-196. Liu Y et al. 2005: . J Volc Geotherm Res 143, 219-235. Zhang Y 1999: Rev Geophys 37, 493-516.

Russell, K.; kennedy, B.; Giordano, D.; Friedlander, E. A.



Impact of Dissolved Oxygen on Feed Conversion, Feed Consumption, and Growth of Blue Catfish Ictalurus furcatus, Channel Catfish I. punctatus, and Blue X Channel Catfish Hybrids  

Technology Transfer Automated Retrieval System (TEKTRAN)

Studies were conducted in 15 1-acre and six ¼-acre ponds over several years to determine the effect of low dissolved oxygen (DO) concentration on food conversion ratio (FCR), food consumption, growth, and net production of blue catfish (BC), channel catfish (CC), and their hybrid (BC X CC). Control ...


Reclamation of cadmium-contaminated soil using dissolved organic matter solution originating from wine-processing waste sludge.  


Soil washing using an acid solution is a common practice for removing heavy metals from contaminated soil in Taiwan. However, serious loss of nutrients from soil is a major drawback of the washing. Distillery sludge can be used to prepare a dissolved organic matter (DOM) solution by extracting its organic constituents with alkaline solutions. This study employed DOM solutions to remediate Cd-contaminated soil (with concentrations up to 21.5 mg kg(-1)) and determine the factors affecting removal of Cd, such as pH, initial concentration of DOM solution, temperature, and washing frequency. When washing with pH 3.0 and 1250 mg L(-1) DOM solution, about 80% and 81% of Cd were removed from the topsoil at 27 °C and subsoil at 40 °C, respectively. To summarize the changes in fertility during DOM washing with various pH solutions: the increase in organic matter content ranged from 7.7% to 23.7%; cation exchange capacity (CEC) ranged from 4.6% to 13.9%; available ammonium (NNH(4)) content ranged from 39.4% to 2175%; and available phosphorus content ranged from 34.5% to 182%. Exchangeable K, Ca, and Mg remained in the topsoil after DOM washing, with concentrations of 1.1, 2.4, and 1.5 times higher than those treated with HCl solution at the same pH, respectively. PMID:23183341

Liu, Cheng-Chung; Chen, Guan-Bu



Effects of Dissolved Carbonate on Arsenate Adsorption and Surface  

E-print Network

, University of Delaware, Newark, Delaware 19717 Effects of dissolved carbonate on arsenate [As(V)] reactivity kinetics, pseudo-equilibrium adsorption/titration experiments, extended X-ray absorption fine structure,andtheresultsareconsistent with the formation of nonprotonated bidentate surface species at the hematite surfaces. The results also suggest

Sparks, Donald L.


Effects of elevated total dissolved solids on bivalves  

EPA Science Inventory

A series of experiments were performed to assess the toxicity of different dominant salt recipes of excess total dissolved solids (TDS) to organisms in mesocosms. Multiple endpoints were measured across trophic levels. We report here the effects of four different TDS recipes on b...



EPA Science Inventory

Conductometric replacement titrations of humic and fulvic acids dissolved in a slight excess of hydroxide were carried out with standard acid. The slope of the titration curve corresponding to the protonation of humate/fulvate was related to the electrophoretic mobility of the...


Dissolved organic matter and nutrients in two Eastern Mediterranean rivers  

Microsoft Academic Search

The role of both inorganic and organic riverine nutrient fluxes in regulating the autotrophy vs eterotrophy in coastal seas is well recognized. Eastern Mediterranean rivers have been studied for the most part, for their inorganic nutrient fluxes, whereas little information is available for their organic nutrient content. This study presents new data on dissolved organic matter composition for two permanent

Elli Pitta; Christina Zeri; Maria Tzortziou; Elias Dimitriou; Elias Moussoulis; Vassiliki Paraskevopoulou; Emanouil Dassenakis




EPA Science Inventory

We examined photochemical alterations of dissolved organic matter (DOM) from the Satilla River, a high DOC (10-40 mg/liter) blackwater river of southeast Georgia. Water samples were filtered to remove most organisms, placed in quartz tubes, and incubated under natural sunlight a...



Technology Transfer Automated Retrieval System (TEKTRAN)

The amount of dissolved oxygen (DO) in water is one of the most commonly used indicators of river and stream health. In most fresh water systems, aquatic fauna become stressed as DO drops below 4 or 5 mg L-1. Under extended hypoxic (low DO) or anoxic (no DO) conditions, most higher forms of life are...



EPA Science Inventory

Water samples were collected from various depths in a pristine sand and gravel water table aquifer at monthly intervals over a period of one year. Dissolved oxygen concentrations were near saturation 9 feet below the water table and decreased to nearly zero at 78 feet below the w...


Investigating Factors that Affect Dissolved Oxygen Concentration in Water  

ERIC Educational Resources Information Center

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

Jantzen, Paul G.



Dissolving Carboxylic Acids and Primary Amines on the Overhead Projector  

ERIC Educational Resources Information Center

Liquid carboxylic acids (or primary amines) with limited solubility in water are dissolved by addition of aqueous sodium hydroxide (or hydrochloric acid) on the stage of an overhead projector using simple glassware and very small quantities of chemicals. This effective and colorful demonstration can be used to accompany discussions of the…

Solomon, Sally D.; Rutkowsky, Susan A.




EPA Science Inventory

A literature search was performed for dissolved organic carbon/water partition coefficients for nonionic chemicals (Kdoc) and Kdoc data was taken from more than sixty references. The Kdoc data were evaluated as a function of the n-octanol/water partition coefficients (Kow). A pre...



EPA Science Inventory

The ability to confidently measure the concentration of dissolved oxygen (D.O.) in ground water is a key aspect of remedial selection and assessment. Presented here is a comparison of the commonly practiced methods for determining D.O. concentrations in ground water, including c...


Biological Uptake of Dissolved Silica in the Amazon River Estuary  

Microsoft Academic Search

Approximately 25 percent of the dissolved silica carried by the Amazon River is depleted through diatom production in the inner estuary. Annual production of opaline frustules is estimated to be 15 million tons. However, few diatoms accumulate in modern shelf sediments and chemical recycling appears to be slight. Instead, many frustules apparently are transported landward into the river system, where

John D. Milliman; Edward Boyle



Transformer Fault Diagnosis by Dissolved-Gas Analysis  

Microsoft Academic Search

The great majority of incipient faults occurring in power transformers gives evidence of their presence early in their developmental stages. Oil and oil-impregnated electrical insulating materials can decompose under the influence of thermal and electrical stresses generating gaseous decomposition products which dissolve in the mineral oil. The nature and the amount of the individual component gases extracted from the oil

Joseph J. Kelly



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) contamination of local shallow groundwater from the application of MSMA. The distinction between "free

Florida, University of



EPA Science Inventory

Dissolved metals in water and total metals in sediments have been measured at marina areas in Lake Texoma during June 1999 to October 2001, and October 2001, respectively. The metals most often found in the highest concentrations in marina water were Na and Ca, followed by Mg an...



Technology Transfer Automated Retrieval System (TEKTRAN)

This paper presents an extended abstract of a research paper describing four commonly used dissolved oxygen (DO) simulation models. The concentration of DO in surface waters is one of the most commonly used indicators of river and stream health. Regulators and other professionals are increasingly r...



EPA Science Inventory

Thrush Lake is a small, highly transparent lake in northeastern Minnesota. rom 1986 to 1991, vertical profiles of water temperature, dissolved oxygen, chlorophyll a concentration, underwater light irradiance, and Secchi depths were measured at monthly intervals during the ice-fre...


Atmospheric inputs and river transport of dissolved substances  

Microsoft Academic Search

Several different types of behaviour can be observed for elements between atmospheric input and river transport including very limited chemical or biological reactivity (CI-, in most cases), change of speciation (C, N, P), recycling to atmosphere (C, N, S, K), increase of dissolved contents through weathering (Si, Ca, Mg, Na), and build-up in soil or vegetation (C, N, P, Ca,