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Sample records for dissolved silica fluxes

  1. High export of dissolved silica from the Greenland Ice Sheet

    NARCIS (Netherlands)

    Meire, L.; Meire, P.; Struyf, E.; Krawczyk, D.W.; Arendt, K.E.; Yde, J.C.; Juul-Pedersen, T.; Hopwood, M. J.; Rysgaard, S.; Meysman, F.J.R.

    2016-01-01

    Silica is an essential element for marine life and plays a key role in the biogeochemistry ofthe ocean. Glacial activity stimulates rock weathering, generating dissolved silica that is exported tocoastal areas along with meltwater. The magnitude of the dissolved silica export from large glacial area

  2. High export of dissolved silica from the Greenland Ice Sheet

    NARCIS (Netherlands)

    Meire, L.; Meire, P.; Struyf, E.; Krawczyk, D.W.; Arendt, K.E.; Yde, J.C.; Juul-Pedersen, T.; Hopwood, M.J.; Rysgaard, S.; Meysman, F.J.R.

    2016-01-01

    Silica is an essential element for marine life and plays a key role in the biogeochemistry of the ocean. Glacial activity stimulates rock weathering, generating dissolved silica that is exported to coastal areas along with meltwater. The magnitude of the dissolved silica export from large glacial

  3. A quantitative method for silica flux evaluation

    Science.gov (United States)

    Schonewille, R. H.; O'Connell, G. J.; Toguri, J. M.

    1993-02-01

    In the smelting of copper and copper/nickel concentrates, the role of silica flux is to aid in the removal of iron by forming a slag phase. Alternatively, the role of flux may be regarded as a means of controlling the formation of magnetite, which can severely hinder the operation of a furnace. To adequately control the magnetite level, the flux must react rapidly with all of the FeO within the bath. In the present study, a rapid method for silica flux evaluation that can be used directly in the smelter has been developed. Samples of flux are mixed with iron sulfide and magnetite and then smelted at a temperature of 1250 °C. Argon was swept over the reaction mixture and analyzed continuously for sulfur dioxide. The sulfur dioxide concentration with time was found to contain two peaks, the first one being independent of the flux content of the sample. A flux quality parameter has been defined as the height-to-time ratio of the second peak. The value of this parameter for pure silica is 5100 ppm/min. The effects of silica content, silica particle size, and silicate mineralogy were investigated. It was found that a limiting flux quality is achieved for particle sizes less than 0.1 mm in diameter and that fluxes containing feldspar are generally of a poorer quality. The relative importance of free silica and melting point was also studied using synthetic flux mixtures, with free silica displaying the strongest effect.

  4. High export of dissolved silica from the Greenland Ice Sheet

    Science.gov (United States)

    Meire, L.; Meire, P.; Struyf, E.; Krawczyk, D. W.; Arendt, K. E.; Yde, J. C.; Juul Pedersen, T.; Hopwood, M. J.; Rysgaard, S.; Meysman, F. J. R.

    2016-09-01

    Silica is an essential element for marine life and plays a key role in the biogeochemistry of the ocean. Glacial activity stimulates rock weathering, generating dissolved silica that is exported to coastal areas along with meltwater. The magnitude of the dissolved silica export from large glacial areas such as the Greenland Ice Sheet is presently poorly quantified and not accounted for in global budgets. Here we present data from two fjord systems adjacent to the Greenland Ice Sheet which reveal a large export of dissolved silica by glacial meltwater relative to other macronutrients. Upscaled to the entire Greenland Ice Sheet, the export of dissolved silica equals 22 ± 10 Gmol Si yr-1. When the silicate-rich meltwater mixes with upwelled deep water, either inside or outside Greenland's fjords, primary production takes place at increased silicate to nitrate ratios. This likely stimulates the growth of diatoms relative to other phytoplankton groups.

  5. Iron oxides, dissolved silica, and regulation of marine phosphate concentration

    Science.gov (United States)

    Planavsky, N.; Reinhard, C.; Lyons, T.

    2008-12-01

    Phosphorous concentrations in iron oxide-rich sediments reflect orthophosphate levels in the water column from which iron oxides precipitated. Sediment P/Fe ratios are also strongly influenced by the concentrations of dissolved species that inhibit orthophosphate-to-ferrihydrite sorption, most notably silica. It may, therefore, be possible to use P/Fe ratios in iron oxide-rich sediments to estimate past dissolved P concentrations, if one considers the evolution of the silica cycle. A compilation of Fe and P data in iron oxide-rich sediments through time reveals an increase in P/Fe ratios after the Jurassic. We propose that this trend indicates evolution of the iron-oxide phosphate removal mechanism caused by decreasing levels of sorption inhibition by dissolved silica. The large difference in P/Fe ratios in Cenozoic versus older iron-oxide rich sediments can be linked with Si drawdown caused by the proliferation of siliceous plankton in the Cretaceous. There is also a late Mesozoic or Cenozoic increase in V/Fe ratios, which provides additional evidence for lower ferrihydrite anion sorption efficiency prior to diatom radiation. P/Fe ratios in iron oxide-rich sediments from the early and middle Phanerozoic are comparable to the ratios in iron formations previously presented as evidence for an early Precambrian phosphate crisis (Bjerrum and Canfield, 2002, Nature, 417:159-162). Given the compelling evidence for higher Si concentrations in the Precambrian compared to the Phanerozoic and dissolved P concentrations comparable to modern levels throughout the Phanerozoic, the presented trend of P/Fe ratios suggests dissolved P concentrations were higher in Precambrian than Phanerozoic oceans. High dissolved P levels in the Precambrian may have been linked to inhibited carbonate fluorapatite (CFA) formation as a result of persistently high levels of carbonate supersaturation. Carbonate ion substitution into CFA scales with the ambient carbonate ion activity and increases

  6. Sediment flux modeling: Simulating nitrogen, phosphorus, and silica cycles

    Science.gov (United States)

    Testa, Jeremy M.; Brady, Damian C.; Di Toro, Dominic M.; Boynton, Walter R.; Cornwell, Jeffrey C.; Kemp, W. Michael

    2013-10-01

    Sediment-water exchanges of nutrients and oxygen play an important role in the biogeochemistry of shallow coastal environments. Sediments process, store, and release particulate and dissolved forms of carbon and nutrients and sediment-water solute fluxes are significant components of nutrient, carbon, and oxygen cycles. Consequently, sediment biogeochemical models of varying complexity have been developed to understand the processes regulating porewater profiles and sediment-water exchanges. We have calibrated and validated a two-layer sediment biogeochemical model (aerobic and anaerobic) that is suitable for application as a stand-alone tool or coupled to water-column biogeochemical models. We calibrated and tested a stand-alone version of the model against observations of sediment-water flux, porewater concentrations, and process rates at 12 stations in Chesapeake Bay during a 4-17 year period. The model successfully reproduced sediment-water fluxes of ammonium (NH4+), nitrate (NO3-), phosphate (PO43-), and dissolved silica (Si(OH)4 or DSi) for diverse chemical and physical environments. A root mean square error (RMSE)-minimizing optimization routine was used to identify best-fit values for many kinetic parameters. The resulting simulations improved the performance of the model in Chesapeake Bay and revealed (1) the need for an aerobic-layer denitrification formulation to account for NO3- reduction in this zone, (2) regional variability in denitrification that depends on oxygen levels in the overlying water, (3) a regionally-dependent solid-solute PO43- partitioning that accounts for patterns in Fe availability, and (4) a simplified model formulation for DSi, including limited sorption of DSi onto iron oxyhydroxides. This new calibration balances the need for a universal set of parameters that remain true to biogeochemical processes with site-specificity that represents differences in physical conditions. This stand-alone model can be rapidly executed on a

  7. Removing Dissolved Silica from Waste Water with Catechol and Active Carbon

    Energy Technology Data Exchange (ETDEWEB)

    Sasan, Koroush [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Nanoscale Sciences Dept.; Brady, Patrick [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Nuclear Energy Program; Krumhansl, James L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Geosciences Dept.; Nenoff, Tina M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Physical Chemical and Nano Sciences Center

    2017-01-01

    Fresh water scarcity is going to be a global great challenge in the near future because of the increasing population. Our water resources are limited and, hence, water treatment and recycling methods are the only alternatives for fresh water procurement in the upcoming decades. Water treatment and recycling methods serve to remove harmful or problematic constituents from ground, surface and waste waters prior to its consumption, industrial supply, or other uses. Scale formation in industrial and domestic installations is still an important problem during water treatment. In water treatment, silica scaling is a real and constant concern for plant operations. The focus of this study is on the viability of using a combination of catechol and active carbon to remove dissolved silica from concentrated cooling tower water (CCTW). Various analytical methods, such as ICP-MS and UV-vis, were used to understand the structure-property relationship between the material and the silica removal results. UV-Vis indicates that catechol can react with silica ions and form a silica-catecholate complex. The speciation calculation of catechol and silica shows that catechol and silica bind in the pH range of 8 – 10; there is no evidence of linkage between them in neutral and acidic pHs. The silica removal results indicate that using ~4g/L of catechol and 10g/L active carbon removes up to 50% of the dissolved silica from the CCTW.

  8. Modeling brine and nutrient dynamics in Antarctic sea ice: the case of dissolved silica

    Science.gov (United States)

    Vancoppenolle, M.; Goosse, H.; de Montety, A.; Fichefet, T.; Tremblay, B.; Tison, J.

    2009-12-01

    Sea ice ecosystems are characterized by micro-algae living in brine inclusions. The growth rate of ice algae depends on light and nutrient supply. Here, the interactions between nutrients and brine dynamics under the influence of algae are investigated using a one-dimensional model. The model includes snow and ice thermodynamics with brine physics and an idealized sea ice biological component, characterized by one nutrient, namely dissolved silica (DSi). In the model, DSi follows brine motion and is consumed by ice algae. Depending on physical ice characteristics, the brine flow is either advective, diffusive or turbulent. The vertical profiles of ice salinity and DSi concentration are solutions of advection-diffusion equations. The model is configured to simulate the typical thermodynamic regimes of first-year Antarctic pack ice. The simulated vertical profiles of salinity and DSi qualitatively reproduce observations. Analysis of results highlights the role of convection in the lowermost 5-10 cm of ice. Convection mixes saline, nutrient-poor brine with comparatively fresh, nutrient-rich seawater. This implies a rejection of salt to the ocean and a flux of DSi to the ice. In presence of growing algae, the simulated ocean-to-ice DSi flux increases by 0-115% compared to an abiotic situation. In turn, primary production and brine convection act in synergy to form a nutrient pump. The other important processes are the flooding of the surface by seawater and the percolation of meltwater. The former refills nutrients near the ice surface in spring. The latter, if present, tends to expell nutrients from the ice in summer. Sketch of salt (left) and nutrient (right) exchanges at the ice-ocean interface proposed in this paper.

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

    OpenAIRE

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

    2006-01-01

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

  10. Seasonal variability of total dissolved fluxes and origin of major dissolved elements within a large tropical river: The Orinoco, Venezuela

    Science.gov (United States)

    Laraque, Alain; Moquet, Jean-Sébastien; Alkattan, Rana; Steiger, Johannes; Mora, Abrahan; Adèle, Georges; Castellanos, Bartolo; Lagane, Christèle; Lopez, José Luis; Perez, Jesus; Rodriguez, Militza; Rosales, Judith

    2013-07-01

    Seasonal variations of total dissolved fluxes of the lower Orinoco River were calculated taking into account four complete hydrological cycles during a five-year period (2005-2010). The modern concentrations of total dissolved solids (TDS) of the Orinoco surface waters were compared with data collected during the second half of the last century published in the literature. This comparison leads to the conclusion that chemical composition did not evolve significantly at least over the last thirty to forty years. Surface waters of the Orinoco at Ciudad Bolivar are between bicarbonated calcic and bicarbonated mixed. In comparison to mean values of concentrations of total dissolved solids (TDS) of world river surface waters (89.2 mg l-1), the Orinoco River at Ciudad Bolivar presents mainly low mineralized surface waters (2005-10: TDS 30 mg l-1). The TDS fluxes passing at this station in direction to the Atlantic Ocean between 2005 and 2010 were estimated at 30 × 106 t yr-1, i.e. 36 t km-2 yr-1. It was observed that the seasonal variations (dry season vs wet season) of total dissolved fluxes (TDS and dissolved organic carbon (DOC)) are mainly controlled by discharge variations. Two groups of elements have been defined from dilution curves and molar ratio diagrams. Ca2+, Mg2+, HCO3-, Cl- and Na+ mainly come from the same geographic and lithologic area, the Andes. K+ and SiO2 essentially come from the Llanos and the Guayana Shield. These findings are important for understanding fundamental geochemical processes within the Orinoco River basin, but also as a baseline study in the perspective of the development of numerous mining activities related with aluminum and steel industries; and the plans of the Venezuelan government to construct new fluvial ports on the lower Orinoco for the transport of hydrocarbons.

  11. Impact of changes in river fluxes of silica on the global marine silicon cycle : a model comparison

    NARCIS (Netherlands)

    Bernard, C. Y.; Laruelle, G. G.; Slomp, C. P.; Heinze, C.

    2010-01-01

    The availability of dissolved silica (Si) in the ocean provides a major control on the growth of siliceous phytoplankton. Diatoms in particular account for a large proportion of oceanic primary production. The original source of the silica is rock weathering, followed by transport of dissolved and

  12. Urban Dissolved Silica: Quantifying the Role of Groundwater and Runoff in Wastewater Influent.

    Science.gov (United States)

    Maguire, Timothy J; Fulweiler, Robinson W

    2016-01-01

    Human impacts on silicon (Si) cycling are just being explored. In particular, we know little about the role of urban environments in altering the flux of Si from land to sea. Here we describe the annual load of dissolved Si (DSi) in the influent of the second largest wastewater treatment plant (by volume) in the United States (Deer Island Wastewater Facility, Boston, MA). We partition the ∼69 500 kmol DSi year(-1) influent load between three sources: runoff (12%), groundwater infiltration (39%), and sewage (49%). Based on these results, we hypothesized that instead of being delivered to local rivers, DSi in groundwater and runoff is redirected to the combined stormwater-sewage overflow system. To test this hypothesis we compared long-term (2007-2012) observations of DSi flux from the three urban rivers surrounding Boston to modeled DSi fluxes based on land use and land cover. As predicted, the modeled fluxes were higher than the measured fluxes indicating that the sewage infrastructure of Boston diverts watershed DSi to the treatment plant. This research increases our understanding of human changes to the Si cycle, demonstrates the potential usefulness of DSi as a groundwater infiltration tracer within sewage treatment systems, and highlights the underappreciated interannual variability of riverine DSi fluxes.

  13. Valorization by thermal cracking over silica of polyolefins dissolved in LCO

    Energy Technology Data Exchange (ETDEWEB)

    Arandes, Jose M.; Erena, Javier; Bilbao, Javier [Departamento de Ingenieria Quimica, Universidad del Pais Vasco, Apartado 644, 48080 Bilbao (Spain); Azkoiti, Miren J. [Departamento de Ingenieria Quimica y del Medio Ambiente, Universidad del Pais Vasco, Plaza de la Casilla 3, 48012 Bilbao (Spain); Lopez-Valerio, Danilo [Facultad de Ingenieria Quimica, Universidad Nacional de Ingenieria, Apartado 5595, Managua (Nicaragua)

    2003-02-15

    A study has been made of the cracking of polyethylene (PE) and polypropylene (PP) (which are the main components of post-consumer plastic wastes) dissolved in the Light Cycle Oil (LCO) product stream of a commercial Fluid Catalytic Cracking (FCC) unit. The cracking has been carried out on a mesoporous silica (pore size between 3 and 30 nm) in the 723-823 K range. This strategy for upgrading plastics and solvents together avoids heat transfer limitations and other problems inherent to the cracking of solid plastics. The polyolefins are transformed mainly into the components that make up the pool of gasoline (C{sub 5}-C{sub 12}). Furthermore, the incorporation of polyolefins has a synergistic effect on the cracking of LCO and causes a major decrease in the content of aromatics of the pool of gasoline and an increase in the content of olefins, paraffins and i-paraffins.

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

    Science.gov (United States)

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

    2001-01-01

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

  15. Ice sheets as a missing source of silica to the polar oceans

    Science.gov (United States)

    Hawkings, Jon R.; Wadham, Jemma L.; Benning, Liane G.; Hendry, Katharine R.; Tranter, Martyn; Tedstone, Andrew; Nienow, Peter; Raiswell, Rob

    2017-01-01

    Ice sheets play a more important role in the global silicon cycle than previously appreciated. Input of dissolved and amorphous particulate silica into natural waters stimulates the growth of diatoms. Here we measure dissolved and amorphous silica in Greenland Ice Sheet meltwaters and icebergs, demonstrating the potential for high ice sheet export. Our dissolved and amorphous silica flux is 0.20 (0.06-0.79) Tmol year-1, ~50% of the input from Arctic rivers. Amorphous silica comprises >95% of this flux and is highly soluble in sea water, as indicated by a significant increase in dissolved silica across a fjord salinity gradient. Retreating palaeo ice sheets were therefore likely responsible for high dissolved and amorphous silica fluxes into the ocean during the last deglaciation, reaching values of ~5.5 Tmol year-1, similar to the estimated export from palaeo rivers. These elevated silica fluxes may explain high diatom productivity observed during the last glacial-interglacial period.

  16. Benthic Fluxes of Dissolved Macro- and Micronutrients to the Water Column of Upper Klamath Lake, Oregon

    Science.gov (United States)

    Kuwabara, J. S.; Topping, B. R.; Lynch, D. D.; Murphy, F.; Carter, J. L.; Lindenberg, M.

    2007-12-01

    Hypoxic, environmentally stressful conditions for endangered fish populations have been generated over the past century by an annual phytoplankton bloom in Upper Klamath Lake, OR. The bloom is consistently dominated by the nitrogen-fixing cyanophyte Aphanizomenon flos-aquae (AFA), thus a quantitative understanding of processes affecting the transport of biologically available phosphorus (P), presumably the limiting nutrient, is critical for resource management in the lake. This work was undertaken to help develop sound remediation or restoration strategies, and to set realistic expectations for water-quality improvements. Particle-reactive phosphate can adsorb or complex onto particles that settle and accumulate in the lake bed. Biogeochemical processes near the sediment-water interface can remobilize particle-bound P and generate a benthic flux of bioavailable P. This study provides estimates of the benthic flux of dissolved macronutrients (i.e., phosphorus and nitrogen species) before, during and after the period of: (1) increased water-column nutrient concentrations that cannot be accounted for by riverine inputs, and (2) the annual bloom of AFA. Benthic flux of dissolved orthophosphate was consistently positive (i.e., out of the sediment into the overlying water column) and ranged between 0.5 and 6.1 mg m-2 d-1. Assuming a lake area of 200 km2, this converts to a mass flux to the entire lake of 8,000 to 100,000 kg over a 3-month AFA bloom season which is comparable in magnitude to riverine inputs. An additional concern related to fish toxicity was that dissolved ammonium also displayed consistently positive benthic fluxes of 4 to 100 mg m-2 d-1; also comparable to riverine inputs. In contrast, dissolved nitrate exhibited a consistently negative flux (consumed by the sediment) with values ranging between -20 to -0.1 mg m-2 d-1. Macroinvertebrate densities of the order of 105 individuals-m-2 suggest that the diffusive-flux estimates may be significantly lower

  17. Temporal variation and fluxes of dissolved rare earth elements in the lower Orinoco River

    Science.gov (United States)

    Mora, Abrahan; Laraque, Alain; Mahlknecht, Jürgen; Moreau, Cristina

    2017-04-01

    On a global scale, the Orinoco River ranks third in terms of water discharged to the oceans, with an annual mean discharge of about 37.000 m3/s; its basin covers an area of 990.000 km2 and the length of its main channel reaches 2000 km. Although the seasonal dynamics of dissolved rare earth elements (REE) has been documented in large rivers such as the Amazon and Yangtze, this issue has not yet been documented in the Orinoco River. Thus, we present a comprehensive dissolved REE data set for the Orinoco River in its lower section. Water samples of the Orinoco River were taken monthly between January 2007 and December 2008 in the Ciudad Bolivar gauging station. These water samples were filtered through 0.22 µm pore size membranes and preserved for REE determination. The concentrations of dissolved La, Ce, Pr, Nd, Sm, Gd, Dy, Er, and Yb were measured using an ICP-MS on a spectrometer equipped by collision cell. The two-year time series show that dissolved REE vary seasonally with discharge in the lower Orinoco, and indicate a hydrological dominated control. The higher concentrations of REE were observed during the high discharge period and the lower concentrations during the low water stage. The annual dissolved fluxes of REE from the Orinoco River to the Atlantic Ocean were 240 ± 67 T/yr for La, 628 ± 174 T/yr for Ce, 76 ± 20 T/yr for Pr, 336 ± 84 T/yr for Nd, 83 ± 20 T/yr for Sm, 92 ± 29 T/yr for Gd, 70 ± 17 T/yr for Dy, 35 ± 8 T/yr for Er, and 28 ± 7 T/yr for Yb. These results constitute the first estimate of dissolved REE fluxes from the Orinoco River to the Atlantic Ocean.

  18. Export of dissolved organic carbon from an upland peatland during storm events: Implications for flux estimates

    Science.gov (United States)

    Clark, Joanna M.; Lane, Stuart N.; Chapman, Pippa J.; Adamson, John K.

    2007-12-01

    SummaryMost of the dissolved organic carbon (DOC) exported from catchments is transported during storm events. Accurate assessments of DOC fluxes are essential to understand long-term trends in the transport of DOC from terrestrial to aquatic systems, and also the loss of carbon from peatlands to determine changes in the source/sink status of peatland carbon stores. However, many long-term monitoring programmes collect water samples at a frequency (e.g. weekly/monthly) less than the time period of a typical storm event (typically organo-mineral soils have shown that both concentration and flux of DOC increases during storm events, lower frequency monitoring could result in substantial underestimation of DOC flux as the most dynamic periods of transport are missed. However, our intensive monitoring study in a UK upland peatland catchment showed a contrasting response to these previous studies. Our results showed that (i) DOC concentrations decreased during autumn storm events and showed a poor relationship with flow during other seasons; and that (ii) this decrease in concentrations during autumn storms caused DOC flux estimates based on weekly monitoring data to be over-estimated, rather than under-estimated, because of over rather than under estimation of the flow-weighted mean concentration used in flux calculations. However, as DOC flux is ultimately controlled by discharge volume, and therefore rainfall, and the magnitude of change in discharge was greater than the magnitude of decline in concentrations, DOC flux increased during individual storm events. The implications for long-term DOC trends are therefore contradictory, as increased rainfall could increase flux but cause an overall decrease in DOC concentrations from peatland streams. Care needs to be taken when interpreting long-term trends in DOC flux rather than concentration; as flux is calculated from discharge estimates, and discharge is controlled by rainfall, DOC flux and rainfall/discharge will

  19. Technical Note: Mesocosm approach to quantify dissolved inorganic carbon percolation fluxes

    DEFF Research Database (Denmark)

    Thaysen, Eike Marie; Jessen, S.; Ambus, Per;

    2014-01-01

    unplanted soil. Carbon dioxide partial pressure (pCO(2)), alkalinity, soil moisture and temperature were measured with depth and time, and DIC in the percolate was quantified using a sodium hydroxide trap. Results showed good reproducibility between two replicate mesocosms. The pCO(2) varied between 0......Dissolved inorganic carbon (DIC) fluxes across the vadose zone are influenced by a complex interplay of biological, chemical and physical factors. A novel soil mesocosm system was evaluated as a tool for providing information on the mechanisms behind DIC percolation to the groundwater from.......2 and 1.1 %, and the alkalinity was 0.1-0.6 meq L-1. The measured cumulative effluent DIC flux over the 78-day experimental period was 185-196 mg L-1 m(-2) and in the same range as estimates derived from pCO(2) and alkalinity in samples extracted from the side of the mesocosm column and the drainage flux...

  20. Carbon Fluxes in Dissolved and Gaseous Forms for a Restored Peatland in British Columbia, Canada

    Science.gov (United States)

    D'Acunha, B.; Johnson, M. S.; Lee, S. C.; Christen, A.

    2016-12-01

    Peatlands are wetlands where gross primary production exceeds organic matter decomposition causing an accumulation of partially decomposed matter, also called peat. These ecosystems can accumulate more carbon than tropical rainforests. However, dissolved and gaseous fluxes of carbon (as dissolved organic carbon (DOC), CO2 and methane (CH4)) must also be considered to determine if these ecosystems are net sinks or sources of greenhouse gases (GHGs) to the atmosphere, which depends in part on the environmental conditions and the state of the ecosystem. We conducted research in Burns Bog, Delta, BC, Canada, a raised domed peat bog located in the Fraser River Delta and one of the largest raised peat bogs on the west coast of the Americas, but which has been heavily impacted by a range of human activities. Currently, ecological restoration efforts are underway by a large-scale ditch blocking program, with the aim to re-establish a high water table. This is approached in partnership with research on the ecosystem services that the bog provides, including its role in a regional GHG inventory. Here we present data on ecosystem-scale fluxes of CO2 and CH4 determined by eddy covariance (EC) on a floating tower platform, and complementary data on (i) evasion fluxes of CO2, CH4 and nitrous oxide (N2O) from the water surface to the atmosphere, and (ii) the flux and composition of dissolved organic carbon in water draining Burns Bog. Concentrations of dissolved CO2, CH4 and N2O were determined by headspace equilibration, and evasion rates from the water surface were quantified and are used to estimate the role of the hydrosphere in the ecosystem-scale measurements. Water samples collected from five saturated areas in the flux tower footprint were analyzed for DOC concentrations and composition. Results indicated that, even though the whole system is a net C sink, the water surface behaved as a source of CO2 and CH4, and a sink for N2O throughout the study period. Drainage waters

  1. Radium-derived porewater exchange and dissolved N and P fluxes in mangroves

    Science.gov (United States)

    Tait, D. R.; Maher, D. T.; Sanders, C. J.; Santos, I. R.

    2017-03-01

    Mangroves are increasingly being recognized as a major player in coastal hydrological and biogeochemical cycles with their complex belowground structure (i.e., crab burrows) facilitating porewater exchange and submarine groundwater discharge. Here, we quantify porewater exchange rates and associated fluxes of nutrients at six mangrove dominated sites covering a broad latitudinal gradient (∼12.4°S to ∼38.3°S) in Australia. Porewater exchange rates were calculated using the natural tracer radium (223Ra and 224Ra) and ranged from 1.5 cm day-1 in the temperate region to 30.9 cm day-1 in the tropics. When porewater exchange rates were multiplied by the global weighted area of mangroves in each of their respective climate zones, this would equate to global porewater exchange rates of 6.4 × 1012 m3 yr-1 (223Ra) and 7.2 × 1012 m3 yr-1 (224Ra) which is equivalent to 17-19% of global riverine freshwater flows. This porewater exchange rate could recirculate a volume of water equal to continental shelf waters adjacent to mangroves every 12.4 (223Ra) and 10.1 (224Ra) years. The radium-derived estimates are within 40% of previous values based on 222Rn (1.3 × 1013 m3 yr-1). The mangrove sites studied were seen to be both nitrogen (N) and phosphorous (P) limited which was driven by a combination of porewater exchange, low incoming surface water nutrient fluxes, and the high contribution of dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP). The average porewater total dissolved nitrogen (TDN) and total dissolved phosphorous (TDP) concentrations were ∼3.4 and 2.7 times greater respectively than in surface waters. The average surface water export of TDN was 2.39 ± 1.30 mmol N m-2 day-1. If upscaled to the global mangrove area, these TDN exports (1.69 Tg N yr-1) would be equal to 6 ± 3% of global river exports. In contrast, there was an overall import of total dissolved phosphorus (TDP) from coastal waters (0.95 ± 0.40 mmol P m-2 day-1) into the

  2. Macroalgae Mediation of Dissolved Organic Nitrogen Fluxes in a Temperate Coastal Lagoon

    Science.gov (United States)

    Tyler, A. C.; McGlathery, K. J.; Anderson, I. C.

    2001-08-01

    The activity of the benthos, including benthic plants, is important in driving the overall system dynamics in shallow lagoons, due to the high ratio of sediment surface area relative to water volume. In Hog Island Bay, benthic macroalgae appear to be a key regulator of DON dynamics, both while alive and following senescence. We investigated the role of macroalgae in mediating water column concentrations and sediment-water column fluxes of DON across a nutrient gradient in Hog Island Bay, a shallow macroalgal-dominated back-barrier lagoon located on the Virginia Coast. Sediment-water column exchanges of DON, urea and DIN were measured in sediment cores with and without macroalgae ( Ulva lactuca) at three subtidal sites from the mainland to the barrier islands in the fall of 1997 and the spring and summer of 1998. The summer sampling dates bracketed a large macroalgal bloom in the mid-lagoon. Dissolved organic nitrogen was an important component (52-98%) of the total dissolved nitrogen pool in Hog Island Bay waters and made up the majority of the sediment N flux to the water column. Macroalgae impacted benthic-pelagic coupling by preventing diffusion of DIN from the water column to the sediments and by intercepting urea fluxes from the sediment to the water column. Closest to the mainland and closest to the barrier islands, at sites with low macroalgal biomass, sediment-water column fluxes of DIN and urea-free DON were negligible or directed into the sediments. Fluxes of urea from the sediment to the water column were significant at both sites, and may play an important role in satisfying macroalgal N demand, especially at the low N island site. Overall, urea was 32% of the mean DON flux from the sediments to the water column. Fluxes of urea-free DON were highest in the mid-lagoon, where macroalgal biomass was highest. The highest overall flux rates of DON (>38 mmol m -2 d -1) and DIN (>33 mmol m -2 d -1) were measured following an isolated crash of a large

  3. Geomorphic controls on riparian zone hydrology, carbon pools and fluxes of dissolved organic carbon

    Science.gov (United States)

    Grabs, T.; Ledesma, J.; Laudon, H.; Seibert, J.; Kohler, S. J.; Bishop, K. H.

    2014-12-01

    Near stream (riparian) zones are an important link between terrestrial and aquatic ecosystems and influence a wide range of processes including solute transport or hydrologic behavior of headwater catchments. Understanding the links between geomorphology and riparian soils, vegetation and hydrology is, thus, a prerequisite for relating small scale processes to observations at the watershed scale. Geographic information systems (GIS) have traditionally been used to study links between geomorphology and properties of terrestrial ecosystems. Applying this approach to riparian zones, however, has only recently become feasible with the availability of high-resolution digital elevation models and the new development of suitable computational methods. In this study we present links between geomorphology and riparian zone hydrology, carbon pools and fluxes of dissolved organic carbon. Geomorphometric attributes were successfully used to predict (1) riparian groundwater levels and flow pathways, (2) the size of riparian soil carbon pools, (3) the vertical variation of dissolved organic carbon (DOC) in riparian soil profiles, as well as (4) riparian carbon fluxes and turnover times.

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

    DEFF Research Database (Denmark)

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

    2015-01-01

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

  5. Impact of changes in river fluxes of silica on the global marine silicon cycle: a model comparison

    Directory of Open Access Journals (Sweden)

    C. Y. Bernard

    2010-02-01

    Full Text Available The availability of dissolved silica (Si in the ocean provides a major control on the growth of siliceous phytoplankton. Diatoms in particular account for a large proportion of oceanic primary production. The original source of the silica is rock weathering, followed by transport of dissolved and biogenic silica to the coastal zone. This model study aims at assessing the sensitivity of the global marine silicon cycle to variations in the river input of silica on timescales ranging from several centuries to millennia. We compare the performance of a box model for the marine silicon cycle to that of a global biogeochemical ocean general circulation model (HAMOCC2 and 5. Results indicate that the average global ocean response to changes in river input of silica is comparable in the models on time scales up to 150 kyrs. While the trends in export production and opal burial are the same, the box model shows a delayed response to the imposed perturbations compared to the general circulation model. Results of both models confirm the important role of the continental margins as a sink for silica at the global scale. Our work also demonstrates that the effects of changes in riverine dissolved silica on ocean biogeochemistry depend on the availability of the other nutrients such as nitrogen, phosphorus and iron. The model results suggest that the effects of reduced silica inputs due to river damming are particularly pronounced in the Gulf of Bengal, Gulf of Mexico and the Amazon plume where they negatively affect opal production. While general circulation models are indispensable when assessing the spatial variation in opal export production and biogenic Si burial in the ocean, this study demonstrates that box models provide a good alternative when studying the average global ocean response to perturbations of the oceanic silica cycle (especially on longer time scales.

  6. Dissolved Carbon Flux and Mass Balance From a Wetland-Dominated Karstic Headwater Catchment

    Science.gov (United States)

    Duval, T. P.; Waddington, J. M.; Branfireun, B. A.

    2009-05-01

    The stream-borne dissolved carbon efflux of peatland-draining catchments is dominated by organic carbon, whereas inorganic carbon dominates the flux from calcareous bedrock catchments. The export of dissolved carbon from calcareous bedrock catchments with significant wetland coverage has not previously been determined. This study documents the spatiotemporal variability of dissolved carbon (inorganic + organic) along a headwater stream in southern Ontario, Canada, as it drains three distinct wetland types: a calcareous fen, a riparian cedar swamp, and a cattail marsh. Upon emergence from the groundwater seeps, the spring water contained 28 times more CO2 than in equilibrium with the atmosphere. This supersaturation decreased to just 5 times equilbrium as the stream leaves the catchment through the marsh, representing a decrease in CO2 concentration of 11 mg L-1, lost to the atmosphere as exsolution. The groundwater seeps contained an average of 1.25±0.75 mg L-1 of dissolved organic carbon (DOC) from May to November 2007, one of the driest years on record in the region. At the catchment outlet through the marsh, DOC concentrations were slightly higher and more variable during the same period at 2.27±1.29 mg L-1, as a fall flushing event resulted in concentrations > 7 mg L-1. This DOC concentration is small compared to the 58.72±3.9 mg L-1 of dissolved inorganic carbon (DIC, as bicarbonate ion) contained within the water leaving the catchment. At 0.21 and 0.17 g m-2 d-1 from May-July and August-November 2007, respectively, the DIC dominated the carbon flux out of the watershed, compared with 0.007 and 0.008 g m- 2 d-1 DOC and 0.015 and 0.009 g m-2 d-1 CO2 exsolution during the same period. Results of the 2007 season will be contrasted to the 2008 season, one of the wettest on record. The watershed is underlain by Silurian dolomite that exhibits karst fractures, resulting in a complex subsurface hydrogeology that influences carbon transport and mass balances

  7. Removal of Dissolved Silica using Calcinated Hydrotalcite in Real-life Applications.

    Energy Technology Data Exchange (ETDEWEB)

    Sasan, Koroush; Brady, Patrick Vane.; Krumhansl, James L.; Nenoff, Tina M.; Sasan, Koroush; Sasan, Koroush

    2017-09-01

    Water shortages are a growing global problem. Reclamation of industrial and municipal wastewater will be necessary in order to mitigate water scarcity. However, many operational challenges, such as silica scaling, prevent large scale water reuse. Previously, our team at Sandia has demonstrated the use of selective ion exchange materials, such as calcinated hydrotalcite (HTC, (Mg 6 Al 2 (OH) 16 (CO 3 )*4H 2 O)), for the low cost removal of silica from synthetic cooling tower water. However, it is not currently know if calcinated HTC has similar capabilities in realistic applications. The purpose of this study was to investigate the ability of calcinated HTC to remove silica from real cooling tower water. This was investigated under both batch and continuous conditions, and in the presence of competing ions. It was determined that calcinated HTC behaved similarly in real and synthetic cooling tower water; the HTC is highly selective for the silica even in the presence of competing cations. Therefore, the data concludes that calcinated HTC is a viable anti-scaling pretreatment for the reuse of industrial wastewaters.

  8. Major ion chemistry of the Son River, India: Weathering processes, dissolved fluxes and water quality assessment

    Indian Academy of Sciences (India)

    Chinmaya Maharana; Sandeep Kumar Gautam; Abhay Kumar Singh; Jayanth K Tripathi

    2015-08-01

    River Son, draining diverse lithologies in the subtropical climate of the peninsular sub-basin of the Ganga basin, is one of the major tributaries of the Ganga River. The chemistry of major ions in the surface water of the Son River was studied in detail to determine various source(s) and processes controlling its water chemistry, seasonal and spatial variations in water chemistry, dissolved fluxes and chemical denudation rate (CDR). The study shows that Ca2+, Mg2+ and HCO$^{-}_{3}$ are major ionic species in the river water. Most of the measured parameters exhibit a relatively lower concentration in the post-monsoon as compared to pre-monsoon season. The water chemistry highlights the influence of continental weathering aided by secondary contributions from ground water, saline/alkaline soils and anthropogenic activities in the catchment. Results also reflect the dominance of carbonate weathering over silicate weathering in controlling water composition. The Son River delivers about 4.2 million tons of dissolved loads annually to the Ganga River, which accounts for ∼6% of the total annual load carried by the Ganga River to the Bay of Bengal. The average CDR of the Son River is 59.5 tons km−2 yr−1, which is less than the reported 72 tons km−2 yr−1 of the Ganga River and higher than the global average of 36 tons km−2 yr−1. The water chemistry for the pre-monsoon and post-monsoon periods shows a strong seasonal control on solute flux and CDR values. The water chemistry indicates that the Son River water is good to excellent in quality for irrigation and also suitable for drinking purposes.

  9. Enhancing water flux of thin-film nanocomposite (TFN membrane by incorporation of bimodal silica nanoparticles

    Directory of Open Access Journals (Sweden)

    Jun Yin

    2016-03-01

    Full Text Available Modern reverse osmosis (RO/nanofiltration (NF membranes are primarily made of thin-film composites (TFC fabricated through interfacial polymerization of m-phenylene diamine (MPD and trimesoyl chloride (TMC on a polysulfone (PSF supporting membrane. In this study, two types of bimodal silica nanoparticles (~80 nm with different internal pore structures were synthesized and incorporated into the polyamide (PA thin-film layer during interfacial polymerization at concentrations varying from 0 to 0.1 wt%. The as-prepared membranes were characterized by scanning electron microscopy (SEM, atomic force microscopy (AFM, and attenuated total reflection Fourier transform infrared (ATR FT-IR spectroscopy, and their performances were evaluated in terms of the water permeability and salt rejection. The results showed the water permeability increased with increasing BSN concentrations, reaching a maximum of 53.5 L m−2 h−1 at a bimodal silica nanoparticle (BSN concentration of 0.5 wt% (pressure at 300 psi, NaCl concentration: 2000 ppm. This represented a flux increase of approximately 40%, while a near constant salt rejection of 95% was maintained. The study demonstrated that the internal micro-mesoporous structures of bimodal silica nanoparticles contributed significantly to the membrane performance, which is consistent with previous studies with relatively uniform internal pores.

  10. Concentration, sources and flux of dissolved organic carbon of precipitation at Lhasa city, the Tibetan Plateau

    Science.gov (United States)

    Li, C.

    2015-12-01

    Dissolved organic carbon (DOC) plays important role in climate system, but few data are available on the Tibetan Plateau (TP). In this study 89 precipitation samples were collected at Lhasa, the largest city of southern Tibet, from March to December 2013. The average concentration and wet deposition fluxes of DOC was 1.10 mg C/L and 0.62 g C m-2.yr-1, respectively. Seasonally, low DOC concentration and high flux appeared during monsoon period, which were in line with heavy precipitation amount, reflecting dilution effect of precipitation for the DOC. Compared to other regions, the values of Lhasa were lower than those of large cites (e.g. Beijing and Seoul) mainly because of less air pollution of Lhasa. The relationship between DOC and ion analysis showed that DOC of Lhasa was derived mainly from the natural sources, followed by burning activities. Furthermore, △14C value of DOC indicated that fossil combustion contributed around 20% of the precipitation DOC of Lhasa, indicating that the atmosphere of Lhasa has been influenced by vehicle emissions. Therefore, although atmosphere of Lhasa is relatively clean, pollutants emitted from local sources cannot be ignored.

  11. Dissolved and particulate Barium in the Ganga (Hooghly) River estuary, India: Solute-particle interactions and the enhanced dissolved flux to the oceans

    Science.gov (United States)

    Samanta, Saumik; Dalai, Tarun K.

    2016-12-01

    In this study, the sources and the cycling of Ba have been evaluated in the Ganga (Hooghly) River estuary using the composition of the suspended sediments and the water samples collected during six seasons of contrasting water discharge over two years (2012 and 2013). In addition, the data on the samples of groundwater from areas adjacent to the estuary, and the industrial effluent water and urban wastewater draining into the estuary are presented. Selective extraction experiments were also performed on the suspended particulate matter of two seasons to assess the distribution of exchangeable concentrations of major ions and Ba. In the mixing zone, the variation patterns of the dissolved Ba concentrations show mid-salinity maxima and are similar to the patterns of variation of the particulate Mg/Al and Mg/Fe, suggesting that the production of dissolved Ba is linked to the adsorption of major ions on to the clay minerals and Fe-Mn oxyhydroxides in the particulate matter. The inference of coupled adsorption-desorption processes is supported by the observations that the particulate Ba/Mg and Ba/K ratios exhibit significant to strong negative correlations with the concentrations of Al, Fe and Mn. The observations of mid-salinity maxima for the concentrations of exchangeable Mg and K, and of the exchangeable Ba concentrations that decrease with salinity provide strong evidence that the solute-particle interactions is the major driver in regulating the dissolved Ba distributions in the estuary. The estimates of the quantity of desorbed Ba based on three different approaches suggest that desorption is sufficient to account for the calculated excess Ba (Baxs) concentrations. The contribution of Ba to the dissolved load via dissolution of the particulate carbonate phases is minor, up to 3% of the maximum Baxs concentrations. The estimates of anthropogenic contributions are insignificant, and account for ⩽2% of maximum Baxs in the estuary. Groundwater contributions are

  12. Assessment of benthic flux of dissolved organic carbon in wetland and estuarine sediments using the eddy-correlation technique

    Science.gov (United States)

    Swett, M. P.; Amirbahman, A.; Boss, E.

    2009-12-01

    Wetland and estuarine sediments release significant amounts of dissolved organic carbon (DOC) due to high levels of microbial activity, particularly sulfate reduction. Changes in climate and hydrologic conditions have a potential to alter DOC release from these systems as well. This is a concern, as high levels of DOC can lead to mobilization of toxic metals and organics in natural waters. In addition, source waters high in DOC produce undesirable disinfection byproducts in water treatment. Various in situ methods, such as peepers and sediment core centrifugation, exist to quantify vertical benthic fluxes of DOC and other dissolved species from the sediment-water interface (SWI). These techniques, however, are intrusive and involve disturbance of the sediment environment. Eddy-correlation allows for real-time, non-intrusive, in situ flux measurement of important analytes, such as O2 and DOC. An Acoustic Doppler Velocimeter (ADV) is used to obtain three-dimensional fluid velocity measurements. The eddy-correlation technique employs the mathematical separation of fluid velocity into mean velocity and fluctuating velocity components, with the latter representing turbulent eddy velocity. DOC concentrations are measured using a colored dissolved organic matter (CDOM) fluorometer, and instantaneous vertical flux is determined from the correlated data. This study assesses DOC flux at three project sites: a beaver pond in the Lower Penobscot Watershed, Maine; a mudflat in Penobscot River, Maine; and a mudflat in Great Bay, New Hampshire. Eddy flux values are compared with results obtained using peepers and centrifugation, as well as vertical profiling.

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

    Science.gov (United States)

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

    2014-01-01

    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

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

    NARCIS (Netherlands)

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

    2009-01-01

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

  15. Analysis of maximum allowable fragment heights during dissolution of high flux isotope reactor fuel in an h-canyon dissolver

    Energy Technology Data Exchange (ETDEWEB)

    Daniel, G. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Rudisill, T. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2017-07-17

    As part of the Spent Nuclear Fuel (SNF) processing campaign, H-Canyon is planning to begin dissolving High Flux Isotope Reactor (HFIR) fuel in late FY17 or early FY18. Each HFIR fuel core contains inner and outer fuel elements which were fabricated from uranium oxide (U3O8) dispersed in a continuous Al phase using traditional powder metallurgy techniques. Fuels fabricated in this manner, like other SNF’s processed in H-Canyon, dissolve by the same general mechanisms with similar gas generation rates and the production of H2. The HFIR fuel cores will be dissolved using a flowsheet developed by the Savannah River National Laboratory (SRNL) in either the 6.4D or 6.1D dissolver using a unique insert. Multiple cores will be charged to the same dissolver solution maximizing the concentration of dissolved Al. The recovered U will be down-blended into low-enriched U for subsequent use as commercial reactor fuel. During the development of the HFIR fuel dissolution flowsheet, the cycle time for the initial core was estimated at 28 to 40 h. Once the cycle is complete, H-Canyon personnel will open the dissolver and probe the HFIR insert wells to determine the height of any fuel fragments which did not dissolve. Before the next core can be charged to the dissolver, an analysis of the potential for H2 gas generation must show that the combined surface area of the fuel fragments and the subsequent core will not generate H2 concentrations in the dissolver offgas which exceeds 60% of the lower flammability limit (LFL) of H2 at 200 °C. The objective of this study is to identify the maximum fuel fragment height as a function of the Al concentration in the dissolving solution which will provide criteria for charging successive HFIR cores to an H-Canyon dissolver.

  16. Benthic fluxes of dissolved organic nitrogen in the Lower St. Lawrence Estuary and implications for selective organic matter degradation

    Directory of Open Access Journals (Sweden)

    M. Alkhatib

    2013-05-01

    Full Text Available The distribution of dissolved organic nitrogen (DON and carbon (DOC in sediment pore waters was determined at nine locations along the St. Lawrence Estuary and in the Gulf of St. Lawrence. The study area is characterized by gradients in the sedimentary particulate organic matter (POM reactivity, bottom water oxygen concentrations, as well as benthic respiration rates. Based on pore water profiles we estimated the benthic diffusive fluxes of DON and DOC. Our results show that DON fluxed out of the sediments at significant rates (110 to 430 μmol m−2 d−1. DON fluxes were positively correlated with sedimentary POM reactivity and sediment oxygen exposure time (OET, suggesting direct links between POM quality, aerobic remineralization and the release of DON to the water column. DON fluxes were on the order of 30% to 64% of the total benthic inorganic fixed N loss due to denitrification, and often exceeded the diffusive nitrate fluxes into the sediments. Hence they represented a large fraction of the total benthic N exchange. This result is particularly important in light of the fact that DON fluxes are usually not accounted for in estuarine and coastal zone nutrient budgets. The ratio of the DON to nitrate flux increased from 0.6 in the Lower Estuary to 1.5 in the Gulf. In contrast to DON, DOC fluxes did not show any significant spatial variation along the Laurentian Channel (LC between the Estuary and the Gulf (2100 ± 100μmol m−2 d−1, suggesting that production and consumption of labile DOC components proceed at similar rates, irrespective of the overall benthic characteristics and the reactivity of POM. As a consequence, the molar C/N ratio of dissolved organic matter (DOM in pore water and the overlying bottom water varied significantly along the transect, with lowest C/N in the Lower Estuary (5–6 and highest C/N (> 10 in the Gulf. We observed large differences between the C/N of pore water DOM with respect to POM, and the degree of

  17. Forest disturbances trigger erosion controlled fluxes of nitrogen, phosphorus and dissolved carbon

    Science.gov (United States)

    Marek Matyjasik; Gretchen Moisen; Todd A. Schroeder; Tracy Frescino; Michael Hernandez

    2015-01-01

    The initial phase of the research that addressed correlation between annual forest disturbance maps produced from LANDSAT images and water quality and flow data indicate that forest disturbances in conjunction with intense atmospheric precipitation commonly trigger fluxes of several chemical constituents, such as nitrogen, phosphorus carbon. These fluxes appear to be...

  18. Sources and the flux pattern of dissolved carbon in rivers of the Yenisey basin draining the Central Siberian Plateau

    Science.gov (United States)

    Prokushkin, A. S.; Pokrovsky, O. S.; Shirokova, L. S.; Korets, M. A.; Viers, J.; Prokushkin, S. G.; Amon, R. M. W.; Guggenberger, G.; McDowell, W. H.

    2011-10-01

    Frequent measurements of dissolved organic (DOC) and inorganic (DIC) carbon concentrations in rivers during snowmelt, the entire ice-free season, and winter were made in five large watersheds (15 000-174 000 km2) of the Central Siberian Plateau (Yenisey River basin). These differ in the degree of continuous permafrost coverage, mean annual air temperature, and the proportion of tundra and forest vegetation. With an annual DOC export from the catchment areas of 2.8-4.7 gC m - 2 as compared to an annual DIC export of 1.0-2.8 gC m - 2, DOC was the dominant component of terrigenous C released to rivers. There was strong temporal variation in the discharge of DOC and DIC. Like for other rivers of the pan-arctic and boreal zones, snowmelt dominated annual fluxes, being 55-71% for water runoff, 64-82% for DOC and 37-41% for DIC. Likewise, DOC and DIC exhibited also a strong spatial variation in C fluxes, with both dissolved C species decreasing from south to north. The rivers of the southern part of the plateau had the largest flow-weighted DOC concentrations among those previously reported for Siberian rivers, but the smallest flow-weighted DIC concentrations. In the study area, DOC and DIC fluxes were negatively correlated with the distribution of continuous permafrost and positively correlated with mean annual air temperature. A synthesis of literature data shows similar trends from west to east, with an eastward decrease of dissolved C concentrations and an increased proportion of DOC in the total dissolved C flux. It appears that there are two contemporary limitations for river export of terrigenous C across Siberia: (1) low productivity of ecosystems with respect to potentially mobilizable organic C, slow weathering rates with concomitant small formation of bicarbonate, and/or wildfire disturbance limit the pools of organic and inorganic C that can be mobilized for transport in rivers (source-limited), and (2) mobilization of available pools of C is constrained by

  19. Patterns of dissolved organic carbon and nitrogen fluxes in deciduous and coniferous forests under historic high nitrogen deposition

    Science.gov (United States)

    Sleutel, S.; Vandenbruwane, J.; de Schrijver, A.; Wuyts, K.; Moeskops, B.; Verheyen, K.; de Neve, S.

    2009-12-01

    Numerous recent studies have indicated that dissolved organic carbon (DOC) and nitrogen (DON) play an important role in C and N cycling in natural ecosystems, and have shown that N deposition alters the concentrations and fluxes of dissolved organic substances and may increase leaching losses from forests. Our study was set up to accurately quantify concentrations and flux patterns of DOC, DON and dissolved inorganic nitrogen (DIN) in deciduous and coniferous forest in Flanders, Belgium, under historical high nitrogen deposition. We measured DOC, DON and DIN concentrations at two weekly intervals in a silver birch (SB) stand, a corsican pine (CP) stand and a pine stand with higher N deposition (CPN), and used the SWAP model (calibrated with PEST) for generating accurate water and matter fluxes. The input with precipitation was an important source of DON, but not for DOC. Release of DOC from the forest floor was minimally affected by forest type, but higher N deposition (CPN stand) caused an 82% increase of DOC release from the forest floor. Adsorption to mineral soil material rich in iron and/or aluminum oxyhydroxides was suggested to be the most important process removing DOC from the soil solution, responsible for substantial retention (67-84%) of DOC entering the mineral soil profile with forest floor leachate. Generally, DON was less reactive (i.e. less removal from the soil solution) than DOC, resulting in decreasing DOC/DON ratios with soil depth. We found increased DOC retention in the mineral soil as a result of higher N deposition (84 kg ha-1 yr-1 additional DOC retention in CPN compared to CP). Overall DON leaching losses were 2.2, 3.3 and 5.0 kg N yr-1 for SB, CP and CPN, respectively, contributing between 9-28% to total dissolved N (TDN) leaching. The relative contribution to TDN leaching from DON loss from SB and CP was mainly determined by (large) differences in DIN leaching. The large TDN leaching losses are alarming, especially in the CPN stand that

  20. Patterns of dissolved organic carbon (DOC) and nitrogen (DON) fluxes in deciduous and coniferous forests under historic high nitrogen deposition

    Science.gov (United States)

    Sleutel, S.; Vandenbruwane, J.; de Schrijver, A.; Wuyts, K.; Moeskops, B.; Verheyen, K.; de Neve, S.

    2009-07-01

    Numerous recent studies have indicated that dissolved organic carbon (DOC) and nitrogen (DON) play an important role in C and N cycling in natural ecosystems, and have shown that N deposition alters the concentrations and fluxes of dissolved organic substances and may increase leaching losses from forests. Our study was set up to accurately quantify concentrations and flux patterns of DOC, DON and dissolved inorganic nitrogen (DIN) in deciduous and coniferous forest in Flanders under historical high nitrogen deposition. We measured DOC, DON and DIN concentrations at two weekly intervals in a silver birch (SB) stand, a corsican pine (CP) stand and a pine stand with higher N deposition (CPN), and used the SWAP model (calibrated with PEST) for generating accurate water and matter fluxes. The input with precipitation was an important source of DON, but not for DOC. Release of DOC from the forest floor was minimally affected by forest type, but higher N deposition (CPN stand) caused an 82% increase of DOC release from the forest floor. Adsorption to mineral soil material rich in iron and/or aluminum oxyhydroxides was suggested to be the most important process removing DOC from the soil solution, responsible for substantial retention (67-84%) of DOC entering the mineral soil profile with forest floor leachate. Generally, DON was less reactive (i.e. less removal from the soil solution) than DOC, resulting in decreasing DOC/DON ratios with soil depth. We found increased DOC retention in the mineral soil as a result of higher N deposition (84 kg N ha-1 yr-1 additional DOC retention in CPN compared to CP). Overall DON leaching losses were 2.2, 3.3 and 5.0 kg N ha-1 yr-1 for SB, CP and CPN, respectively, contributing between 9-28% to total dissolved N (TDN) leaching. DON loss from SB and CP was not much higher than from unpolluted forests, and its relative contribution to TDN leaching was mainly determined by (large) differences in DIN leaching. The large TDN leaching losses

  1. Patterns of dissolved organic carbon (DOC and nitrogen (DON fluxes in deciduous and coniferous forests under historic high nitrogen deposition

    Directory of Open Access Journals (Sweden)

    S. Sleutel

    2009-07-01

    Full Text Available Numerous recent studies have indicated that dissolved organic carbon (DOC and nitrogen (DON play an important role in C and N cycling in natural ecosystems, and have shown that N deposition alters the concentrations and fluxes of dissolved organic substances and may increase leaching losses from forests. Our study was set up to accurately quantify concentrations and flux patterns of DOC, DON and dissolved inorganic nitrogen (DIN in deciduous and coniferous forest in Flanders under historical high nitrogen deposition. We measured DOC, DON and DIN concentrations at two weekly intervals in a silver birch (SB stand, a corsican pine (CP stand and a pine stand with higher N deposition (CPN, and used the SWAP model (calibrated with PEST for generating accurate water and matter fluxes. The input with precipitation was an important source of DON, but not for DOC. Release of DOC from the forest floor was minimally affected by forest type, but higher N deposition (CPN stand caused an 82% increase of DOC release from the forest floor. Adsorption to mineral soil material rich in iron and/or aluminum oxyhydroxides was suggested to be the most important process removing DOC from the soil solution, responsible for substantial retention (67–84% of DOC entering the mineral soil profile with forest floor leachate. Generally, DON was less reactive (i.e. less removal from the soil solution than DOC, resulting in decreasing DOC/DON ratios with soil depth. We found increased DOC retention in the mineral soil as a result of higher N deposition (84 kg N ha−1 yr−1 additional DOC retention in CPN compared to CP. Overall DON leaching losses were 2.2, 3.3 and 5.0 kg N ha−1 yr−1 for SB, CP and CPN, respectively, contributing between 9–28% to total dissolved N (TDN leaching. DON loss from SB and CP was not much higher than from unpolluted forests, and its relative contribution to TDN leaching was mainly determined by

  2. Patterns of dissolved organic carbon and nitrogen fluxes in deciduous and coniferous forests under historic high nitrogen deposition

    Directory of Open Access Journals (Sweden)

    S. Sleutel

    2009-12-01

    Full Text Available Numerous recent studies have indicated that dissolved organic carbon (DOC and nitrogen (DON play an important role in C and N cycling in natural ecosystems, and have shown that N deposition alters the concentrations and fluxes of dissolved organic substances and may increase leaching losses from forests. Our study was set up to accurately quantify concentrations and flux patterns of DOC, DON and dissolved inorganic nitrogen (DIN in deciduous and coniferous forest in Flanders, Belgium, under historical high nitrogen deposition. We measured DOC, DON and DIN concentrations at two weekly intervals in a silver birch (SB stand, a corsican pine (CP stand and a pine stand with higher N deposition (CPN, and used the SWAP model (calibrated with PEST for generating accurate water and matter fluxes. The input with precipitation was an important source of DON, but not for DOC. Release of DOC from the forest floor was minimally affected by forest type, but higher N deposition (CPN stand caused an 82% increase of DOC release from the forest floor. Adsorption to mineral soil material rich in iron and/or aluminum oxyhydroxides was suggested to be the most important process removing DOC from the soil solution, responsible for substantial retention (67–84% of DOC entering the mineral soil profile with forest floor leachate. Generally, DON was less reactive (i.e. less removal from the soil solution than DOC, resulting in decreasing DOC/DON ratios with soil depth. We found increased DOC retention in the mineral soil as a result of higher N deposition (84 kg ha−1 yr−1 additional DOC retention in CPN compared to CP. Overall DON leaching losses were 2.2, 3.3 and 5.0 kg N yr−1 for SB, CP and CPN, respectively, contributing between 9–28% to total dissolved N (TDN leaching. The relative contribution to TDN leaching from DON loss from SB and CP was mainly determined by (large differences in DIN leaching. The large TDN leaching

  3. Dissolved greenhouse gas concentrations and fluxes from Wetlands P7 and P8 of the Cottonwood Lake Study area, Stutsman County, North Dakota, 2015

    Science.gov (United States)

    Bansal, Sheel; Tangen, Brian

    2016-01-01

    A study was conducted to assess the relationships among carbon mineralization, sulfate reduction and greenhouse gas emissions in prairie pothole wetlands. These data are for dissolved methane and carbon dioxide concentrations and fluxes. Dissolved gas concentrations in the water column and fluxes to the atmosphere were estimated from April through November, 2015 for wetlands P7 and P8 of the Cottonwood Lake Study area, Stutsman County, North Dakota. Dissolved gases in the water column were collected every two weeks using a pumping-induced ebullition device. Gas flux samples were collected concurrently at the water-atmosphere interface using the vented static-chamber method. Gas concentrations of the gas samples were determined using gas chromatography. Air and water temperature and water depth also were collected concurrently. These data directly support the associated publication “Abundant carbon substrates drive extremely high sulfate reduction rates and methane fluxes in Prairie Pothole Wetlands” which is referenced within the Metadata.

  4. Ice sheets as a missing source of silica to the polar oceans

    Science.gov (United States)

    Hawkings, Jon R.; Wadham, Jemma L.; Benning, Liane G.; Hendry, Katharine R.; Tranter, Martyn; Tedstone, Andrew; Nienow, Peter; Raiswell, Rob

    2017-01-01

    Ice sheets play a more important role in the global silicon cycle than previously appreciated. Input of dissolved and amorphous particulate silica into natural waters stimulates the growth of diatoms. Here we measure dissolved and amorphous silica in Greenland Ice Sheet meltwaters and icebergs, demonstrating the potential for high ice sheet export. Our dissolved and amorphous silica flux is 0.20 (0.06–0.79) Tmol year−1, ∼50% of the input from Arctic rivers. Amorphous silica comprises >95% of this flux and is highly soluble in sea water, as indicated by a significant increase in dissolved silica across a fjord salinity gradient. Retreating palaeo ice sheets were therefore likely responsible for high dissolved and amorphous silica fluxes into the ocean during the last deglaciation, reaching values of ∼5.5 Tmol year−1, similar to the estimated export from palaeo rivers. These elevated silica fluxes may explain high diatom productivity observed during the last glacial–interglacial period. PMID:28120824

  5. Estimation of dissolved inorganic nutrients fluxes from the Changjiang River into estuary

    Institute of Scientific and Technical Information of China (English)

    刘新成; 沈焕庭

    2001-01-01

    Because the estuary acts as either a trap or a source or both for nutrient elements and will modify greatly the riverine transport to the ocean, it is necessary to calculate the flux from river into estuary and that from estuary into sea, respectively. The present work aims to use a long-term record of nutrients concentrations and runoff discharges on H.e Datong section (625 km inland from the Changjiang River mouth) to identify the variability of nutrients concentrations and to estimate nutrients fluxes from the Changjiang River into the estuary.

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

    Science.gov (United States)

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

    2012-12-01

    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 (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 μm size fraction, respectively

  7. Multi-decadal increases in dissolved organic carbon and alkalinity flux from the Mackenzie drainage basin to the Arctic Ocean

    Science.gov (United States)

    Tank, Suzanne E.; Striegl, Robert G.; McClelland, James W.; Kokelj, Steven V.

    2016-05-01

    Riverine exports of organic and inorganic carbon (OC, IC) to oceans are intricately linked to processes occurring on land. Across high latitudes, thawing permafrost, alteration of hydrologic flow paths, and changes in vegetation may all affect this flux, with subsequent implications for regional and global carbon (C) budgets. Using a unique, multi-decadal dataset of continuous discharge coupled with water chemistry measurements for the Mackenzie River, we show major increases in dissolved OC (DOC) and IC (as alkalinity) fluxes since the early 1970s, for a watershed that covers 1.8 M km2 of northwestern Canada, and provides substantial inputs of freshwater and biogeochemical constituents to the Arctic Ocean. Over a 39-year period of record, DOC flux at the Mackenzie mouth increased by 39.3% (44.5 ± 22.6 Gmol), while alkalinity flux increased by 12.5% (61.5 ± 60.1 Gmol). Isotopic analyses and substantial increases in sulfate flux indicate that increases in alkalinity are driven by accelerating sulfide oxidation, a process that liberates IC from rock and soils in the absence of CO2 consumption. Seasonal and sub-catchment trends suggest that permafrost thaw plays an important role in the observed increases in DOC and alkalinity: sub-catchment increases for all constituents are confined to northern, permafrost-affected regions, while observed increases in autumn to winter are consistent with documented landscape-scale changes that have resulted from changing thaw dynamics. This increase in DOC and sulfide-derived alkalinity represents a substantial intensification of land-to-ocean C mobilization, at a level that is significant within the regional C budget. The change we observe, for example, is similar to current and projected future rates of CO2 consumption by weathering in the Mackenzie basin.

  8. Dissolved methane and carbon dioxide fluxes in Subarctic and Arctic regions: Assessing measurement techniques and spatial gradients

    Science.gov (United States)

    Garcia-Tigreros Kodovska, Fenix; Sparrow, Katy J.; Yvon-Lewis, Shari A.; Paytan, Adina; Dimova, Natasha T.; Lecher, Alanna; Kessler, John D.

    2016-02-01

    Here we use a portable method to obtain high spatial resolution measurements of concentrations and calculate diffusive water-to-air fluxes of CH4 and CO2 from two Subarctic coastal regions (Kasitsna and Jakolof Bays) and an Arctic lake (Toolik Lake). The goals of this study are to determine distributions of these concentrations and fluxes to (1) critically evaluate the established protocols of collecting discrete water samples for these determinations, and to (2) provide a first-order extrapolation of the regional impacts of these diffusive atmospheric fluxes. Our measurements show that these environments are highly heterogeneous. Areas with the highest dissolved CH4 and CO2 concentrations were isolated, covering less than 21% of the total lake and bay areas, and significant errors can be introduced if the collection of discrete water samples does not adequately characterize these spatial distributions. A first order extrapolation of diffusive fluxes to all Arctic regions with similar characteristics as Toolik Lake suggests that these lakes are likely supplying 0.21 and 15.77 Tg of CH4 and CO2 to the atmosphere annually, respectively. Similarly, we found that the Subarctic Coastal Ocean is likely supplying 0.027 Tg of CH4 annually and is taking up roughly 524 Tg of CO2 per year. Although diffusive fluxes at Toolik Lake may not be as substantial when comparing against present seep ebullition and spring ice-out values, warming in the Arctic may result in the increase of methane discharge and methane emissions to the atmosphere. Thus further work is needed to understand this changing environment. This study suggests that high spatial resolution measurement protocols, similar to the one used here, should be incorporated into field campaigns to reduce regional uncertainty and refine global emission estimates.

  9. Multi-decadal increases in dissolved organic carbon and alkalinity flux from the Mackenzie drainage basin to the Arctic Ocean

    Science.gov (United States)

    Tank, Suzanne E.; Striegl, Robert G.; McClelland, James W.; Kokelj, Steven V.

    2016-01-01

    Riverine exports of organic and inorganic carbon (OC, IC) to oceans are intricately linked to processes occurring on land. Across high latitudes, thawing permafrost, alteration of hydrologic flow paths, and changes in vegetation may all affect this flux, with subsequent implications for regional and global carbon (C) budgets. Using a unique, multi-decadal dataset of continuous discharge coupled with water chemistry measurements for the Mackenzie River, we show major increases in dissolved OC (DOC) and IC (as alkalinity) fluxes since the early 1970s, for a watershed that covers 1.8 M km2 of northwestern Canada, and provides substantial inputs of freshwater and biogeochemical constituents to the Arctic Ocean. Over a 39-year period of record, DOC flux at the Mackenzie mouth increased by 39.3% (44.5 ± 22.6 Gmol), while alkalinity flux increased by 12.5% (61.5 ± 60.1 Gmol). Isotopic analyses and substantial increases in sulfate flux indicate that increases in alkalinity are driven by accelerating sulfide oxidation, a process that liberates IC from rock and soils in the absence of CO2 consumption. Seasonal and sub-catchment trends suggest that permafrost thaw plays an important role in the observed increases in DOC and alkalinity: sub-catchment increases for all constituents are confined to northern, permafrost-affected regions, while observed increases in autumn to winter are consistent with documented landscape-scale changes that have resulted from changing thaw dynamics. This increase in DOC and sulfide-derived alkalinity represents a substantial intensification of land-to-ocean C mobilization, at a level that is significant within the regional C budget. The change we observe, for example, is similar to current and projected future rates of CO2 consumption by weathering in the Mackenzie basin.

  10. Benthic Flux of Dissolved Nickel into the Water Column of South San Francisco Bay

    Science.gov (United States)

    2001-01-01

    Phosphorous (N:P) Benthic Flux Ratio Fig. 9 – Incubation Core Design Fig. 10 – Macroinvertebrate Taxonomy Fig. 11 – Benthic Chlorophyll Analyses Fig...l a r F l u x R a t i o Redfield Ratio Incubation Core Design Fig. 9 Benthic Macroinvertebrate Taxonomy Fig. 10 Benthic Chlorophyll...98 25-May-99 08-Apr-98 15-Sep-98 25-May-99 Phylum Mollusca Class Bivalvia Potamocorbula amurensis 520 303 195 Musculista senhousia 43 130 Mya

  11. Inorganic carbon dominates total dissolved carbon concentrations and fluxes in British rivers: Application of the THINCARB model - Thermodynamic modelling of inorganic carbon in freshwaters.

    Science.gov (United States)

    Jarvie, Helen P; King, Stephen M; Neal, Colin

    2017-01-01

    River water-quality studies rarely measure dissolved inorganic carbon (DIC) routinely, and there is a gap in our knowledge of the contributions of DIC to aquatic carbon fluxes and cycling processes. Here, we present the THINCARB model (THermodynamic modelling of INorganic CARBon), which uses widely-measured determinands (pH, alkalinity and temperature) to calculate DIC concentrations, speciation (bicarbonate, HCO3(-); carbonate, CO3(2-); and dissolved carbon dioxide, H2CO3(⁎)) and excess partial pressures of carbon dioxide (EpCO2) in freshwaters. If calcium concentration measurements are available, THINCARB also calculates calcite saturation. THINCARB was applied to the 39-year Harmonised Monitoring Scheme (HMS) dataset, encompassing all the major British rivers discharging to the coastal zone. Model outputs were combined with the HMS dissolved organic carbon (DOC) datasets, and with spatial land use, geology, digital elevation and hydrological datasets. We provide a first national-scale evaluation of: the spatial and temporal variability in DIC concentrations and fluxes in British rivers; the contributions of DIC and DOC to total dissolved carbon (TDC); and the contributions to DIC from HCO3(-) and CO3(2-) from weathering sources and H2CO3(⁎) from microbial respiration. DIC accounted for >50% of TDC concentrations in 87% of the HMS samples. In the seven largest British rivers, DIC accounted for an average of 80% of the TDC flux (ranging from 57% in the upland River Tay, to 91% in the lowland River Thames). DIC fluxes exceeded DOC fluxes, even under high-flow conditions, including in the Rivers Tay and Tweed, draining upland peaty catchments. Given that particulate organic carbon fluxes from UK rivers are consistently lower than DOC fluxes, DIC fluxes are therefore also the major source of total carbon fluxes to the coastal zone. These results demonstrate the importance of accounting for DIC concentrations and fluxes for quantifying carbon transfers from land

  12. Differentiation of colloidal and dissolved silica: Analytical separation using spectrophotometry and inductively coupled plasma atomic emission spectrometry

    Science.gov (United States)

    Lewis-Russ, A.; Ranville, J.; Kashuba, A.T.

    1991-01-01

    A method is described that differentiates between solutions containing silica-dominated colloids and solutions that are essentially free of colloids. Suspensions of tuff particles were treated to remove colloids by centrifugation, filtration or both. Agreement of silica concentrations determined by inductively coupled plasma atomic emission spectrometry and by a spectrophotometric method was taken as an indication of colloid-free solutions. For two tuffs, centrifugation was effective for removing colloids. For the third, highly altered tuff, filtration was more effective for removing colloids.

  13. Global patterns of dissolved silica export to the coastal zone: Results from a spatially explicit global model

    NARCIS (Netherlands)

    Beusen, A.H.W.; Bouwman, A.F.; Dürr, H.H.; Dekkers, A.L.M.; Hartmann, J.

    2009-01-01

    We present a multiple linear regression model developed for describing global river export of dissolved SiO2 (DSi) to coastal zones. The model, with river basin spatial scale and an annual temporal scale, is based on four variables with a significant influence on DSi yields (soil bulk density, preci

  14. Gold-coated silica as a preconcentration phase for the determination of total dissolved mercury in natural waters using atomic fluorescence spectrometry.

    Science.gov (United States)

    Leopold, Kerstin; Foulkes, Michael; Worsfold, Paul J

    2009-05-01

    A novel solid-phase preconcentration method is reported, using in-house gold-coated silica adsorbent packed in a microcolumn, for the determination of dissolved mercury in natural waters by atomic fluorescence spectrometry (AFS). The adsorbent was prepared by chemical reduction of a Au(III) solution with hydroxylamine in the presence of suspended silica particles. The resulting Au nanoparticles on the silica surface were highly efficient for adsorbing different mercury species from acidified waters without additional reagents. The acidified aqueous samples were passed over the microcolumn, either incorporated in a fully automated flow injection (FI) system directly coupled to the AFS or as part of a portable FI system for in situ preconcentration. After rinsing and drying of the column, Hg(0) was released by heating and directed to the AFS cell for quantification. The method offers significant advantages because no reagents are needed for species conversion, preconcentration, sample storage, or desorption and therefore the risk of contamination is minimized and blank values are lowered. This results in a low detection limit of 180 pg L(-1) using a sample volume of only 7 mL and good reproducibility, with relative standard deviations 90% in spiked river waters (spiked [Hg] = 0, 1, 5, 10 ng L(-1)), and the experimental value for the certified reference material ORMS-4 (elevated mercury in river water) was 22.3 +/- 2.6 ng Hg L(-1) which was in good agreement with the certified value of 22.0 +/- 1.6 ng Hg L(-1) (recovery = 101%). The method was successfully applied to seven different natural waters and wastewaters ([Hg] 0.5-4.6 ng L(-1)) from south west England.

  15. High flux, positively charged loose nanofiltration membrane by blending with poly (ionic liquid) brushes grafted silica spheres.

    Science.gov (United States)

    Yu, Liang; Zhang, Yatao; Wang, Yuanming; Zhang, Haoqin; Liu, Jindun

    2015-04-28

    Silica spheres modified by poly (ionic liquid) brushes, a novel positively charged nanomaterial is prepared by atom transfer radical polymerization (ATRP). A high flux positively charged loose nanofiltration membrane is fabricated via "blending-phase inversion" method. The morphology structures, hydrophilicity, thermal and mechanical properties, permeation performance of these membranes are investigated in detail. The results reveal that the hybrid membranes have enhanced surface hydrophilicity, water permeability, thermal stability, and mechanical properties. Characterization of membrane separation properties shows that the hybrid membranes possess higher salt permeability and relatively higher rejection for reactive dyes, which may open opportunities for the recycling of reactive dyes wastewater. Moreover, such hybrid membranes have an outstanding operational stability and salts concentration showed little effect on the separation properties.

  16. Adsorption of Pb and Zn from binary metal solutions and in the presence of dissolved organic carbon by DTPA-functionalised, silica-coated magnetic nanoparticles.

    Science.gov (United States)

    Hughes, D L; Afsar, A; Harwood, L M; Jiang, T; Laventine, D M; Shaw, L J; Hodson, M E

    2017-09-01

    The ability of diethylenetriaminepentaacetic acid (DTPA)-functionalised, silica-coated magnetic nanoparticles to adsorb Pb and Zn from single and bi-metallic metal solutions and from solutions containing dissolved organic carbon was assessed. In all experiments 10 mL solutions containing 10 mg of nanoparticles were used. For single metal solutions (10 mg L(-1) Pb or Zn) at pH 2 to 8, extraction efficiencies were typically >70%. In bi-metallic experiments, examining the effect of a background of either Zn or Pb (0.025 mmol L(-1)) on the adsorption of variable concentrations (0-0.045 mmol L(-1)) of the other metal (Pb or Zn, respectively) adsorption was well modelled by linear isotherms (R(2) > 0.60; p ≤ 0.001) and Pb was preferentially adsorbed relative to Zn. In dissolved organic carbon experiments, the presence of fulvic acid (0, 2.1 and 21 mg DOC L(-1)) reduced Pb and Zn adsorption from 0.01, 0.1 and 1.0 mmol L(-1) solutions. However, even at 21 mg DOC L(-1) fulvic acid, extraction efficiencies from 0.01 to 0.1 mmol L(-1) solutions remained >80% (Pb) and >50% (Zn). Decreases in extraction efficiency were significant between initial metal concentrations of 0.1 and 1.0 mmol L(-1) indicating that at metal loadings between c. 100 mg kg(-1) and 300 mg kg(-1) occupancy of adsorption sites began to limit further adsorption. The nanoparticles have the potential to perform effectively as metal adsorbents in systems containing more than one metal and dissolved organic carbon at a range of pH values. Copyright © 2017. Published by Elsevier Ltd.

  17. Seasonal hydrology drives rapid shifts in the flux and composition of dissolved and particulate organic carbon and major and trace ions in the Fraser River, Canada

    Science.gov (United States)

    Voss, B. M.; Peucker-Ehrenbrink, B.; Eglinton, T. I.; Spencer, R. G. M.; Bulygina, E.; Galy, V.; Lamborg, C. H.; Ganguli, P. M.; Montluçon, D. B.; Marsh, S.; Gillies, S. L.; Fanslau, J.; Epp, A.; Luymes, R.

    2015-10-01

    Rapid changes in the volume and sources of discharge during the spring freshet lead to pronounced variations in biogeochemical properties in snowmelt-dominated river basins. We used daily sampling during the onset of the freshet in the Fraser River (southwestern Canada) in 2013 to identify rapid changes in the flux and composition of dissolved material, with a focus on dissolved organic matter (DOM). Previous time series sampling (at twice monthly frequency) of dissolved inorganic species in the Fraser River has revealed smooth seasonal transitions in concentrations of major ions and tracers of water and dissolved load sources between freshet and base flow periods. In contrast, daily sampling reveals a significant increase in dissolved organic carbon (DOC) concentration (200 to 550 μmol L-1) occurring over a matter of days, accompanied by a shift in DOM optical properties, indicating a transition towards higher molecular weight, more aromatic DOM composition. Comparable changes in DOM composition, but not concentration, occur at other times of year, underscoring the role of seasonal climatology in DOM cycling. A smaller data set of total and dissolved Hg concentrations also showed variability during the spring freshet period, although dissolved Hg dynamics appear to be driven by factors beyond DOM as characterized here. The time series records of DOC and particulate organic carbon (POC) concentrations indicate that the Fraser River exports 0.25-0.35 % of its annual basin net primary productivity. The snowmelt-dominated hydrology, forested land cover, and minimal reservoir impoundment of the Fraser River may influence the DOC yield of the basin, which is high relative to the nearby Columbia River and of similar magnitude to that of the Yukon River to the north. Anticipated warming and decreased snowfall due to climate changes in the region may cause an overall decrease in DOM flux from the Fraser River to the coastal ocean in coming decades

  18. Variability in runoff fluxes of dissolved and particulate carbon and nitrogen from two watersheds of different tree species during intense storm events

    Science.gov (United States)

    Lee, Mi-Hee; Payeur-Poirier, Jean-Lionel; Park, Ji-Hyung; Matzner, Egbert

    2016-09-01

    Heavy storm events may increase the amount of organic matter in runoff from forested watersheds as well as the relation of dissolved to particulate organic matter. This study evaluated the effects of monsoon storm events on the runoff fluxes and on the composition of dissolved (coniferous/deciduous (mixed watershed) and a deciduous forested watershed (deciduous watershed) in South Korea. During storm events, DOC concentrations in runoff increased with discharge, while DON concentrations remained almost constant. DOC, DON and NO3-N fluxes in runoff increased linearly with discharge pointing to changing flow paths from deeper to upper soil layers at high discharge, whereas nonlinear responses of POC and PON fluxes were observed likely due to the origin of particulate matter from the erosion of mineral soil along the stream benches. The integrated C and N fluxes in runoff over the 2-month study period were in the order of DOC > POC and NO3-N > DON > PON. The integrated DOC fluxes in runoff during the study period were much larger at the deciduous watershed (16 kg C ha-1) than at the mixed watershed (7 kg C ha-1), while the integrated NO3-N fluxes were higher at the mixed watershed (5.2 kg N ha-1) than at the deciduous watershed (2.9 kg N ha-1). The latter suggests a larger N uptake by deciduous trees. Integrated fluxes of POC and PON were similar at both watersheds. The composition of organic matter in soils and runoff indicates that the contribution of near-surface flow to runoff was larger at the deciduous than at the mixed watershed. Our results demonstrate different responses of particulate and dissolved C and N in runoff to storm events as a combined effect of tree species composition and watershed specific flow paths.

  19. Concentrations and fluxes of dissolved organic carbon in runoff from a forested catchment: insights from high frequency measurements

    Directory of Open Access Journals (Sweden)

    S. Strohmeier

    2013-02-01

    Full Text Available Concentrations of dissolved organic carbon (DOC in runoff from catchments are often subject to substantial short-term variations. The aim of this study was to identify the compartmental sources of DOC in a forested catchment and the causes for short-term variations in runoff. Furthermore, we investigated the implication of short-term variations for the calculation of annual runoff fluxes. High frequency measurements (30 min intervals of DOC in runoff, of discharge and groundwater table were conducted for one year in the 4.2 km2 forested Lehstenbach catchment, Germany. Riparian wetland soils represent about 30% of the catchment area. The quality of DOC was investigated by three dimensional fluorescence excitation-emission matrices in samples taken from runoff, deep groundwater and shallow groundwater from the riparian wetland soils. The concentrations of DOC in runoff were highly variable at an hourly to daily time scale, ranging from 2.6 mg L−1 to 34 mg L−1 with an annual average of 9.2 mg L−1. The concentrations were positively related to discharge, with a counter clockwise hysteresis. Relations of DOC to discharge were steeper and the degree of hysteresis larger in the summer/fall than in the winter/spring period. Dynamics of groundwater table, discharge, DOC concentrations and DOC quality parameters indicated that DOC in runoff originated mainly from the riparian wetland soils, both under low and high flow conditions. The annual export of DOC from the catchment was 84 kg C ha−1 yr−1 when calculated from the high frequency measurements. If the annual export was calculated by simulated samplings of >2 days intervals substantial deviations resulted.

    Predicted changes in precipitation and discharge patterns as well as generally increasing temperatures likely will cause raising DOC exports from this catchment.

  20. Silicon Isotope Fractionation by Banana Under Continuous Nutrient and Silica Flux

    Science.gov (United States)

    Opfergelt, S.; Cardinal, D.; Henriet, C.; Delvaux, B.; André, L.

    2004-12-01

    Silicon is absorbed by plants as aqueous H4SiO4 with other essential nutrients, and precipitates in aerial parts of the plant as phytolith, a biogenic opal. Phytoliths are restored to the soil by decomposition of organic debris from plant material. The role of higher plants in the biogeochemical cycle of silicon is therefore major although it is still poorly studied. Biomineralization processes are known to fractionate the three stable silicon isotopes with a preferential uptake of light isotopes. Therefore, following some preliminary results from Douthitt (1982), and studies presented in recent conferences (Ziegler et al., 2002; Ding et al., 2003), we suspect that phytolith production by plants could also fractionate the silicon isotopes. Inversely, intensity of phytolith-related isotopic fractionations might contribute to a better understanding of the soil-plant silicon cycle. Our study focused on banana, a silicon accumulating plant (>1% Si, dry weight).Musa acuminata cv Grande Naine has been grown in hydroponics under controlled conditions (light, temperature, humidity, nutrients) during six weeks. The nutrient supply was kept constant: three batches of five plants were grown with a continuous nutrient solution flow of 5, 50 and 100 ppm SiO2 respectively. Si isotopic compositions were measured in the source solution, and in silica extracted from the various parts of banana (roots, pseudostems, midribs and petioles, leaves), using a Nu Plasma multicollector mass spectrometer (MC-ICP-MS) operating in dry plasma mode. The results are expressed as δ 29Si relatively to the NBS28 standard, with an average precision of ± 0.03‰ . Silicon contents and morphological studies of phytoliths were also achieved. Banana δ 29Si varied between -0.18 and -0.76‰ with a source solution at -0.02‰ . Values of δ 29Si were less fractionated, relatively to the nutrient solution, in roots, where no phytoliths have been observed until now, than in upper parts of banana where

  1. Concentration and flux of total and dissolved phosphorus, total nitrogen, chloride, and total suspended solids for monitored tributaries of Lake Champlain, 1990-2012

    Science.gov (United States)

    Medalie, Laura

    2014-01-01

    Annual and daily concentrations and fluxes of total and dissolved phosphorus, total nitrogen, chloride, and total suspended solids were estimated for 18 monitored tributaries to Lake Champlain by using the Weighted Regressions on Time, Discharge, and Seasons regression model. Estimates were made for 21 or 23 years, depending on data availability, for the purpose of providing timely and accessible summary reports as stipulated in the 2010 update to the Lake Champlain “Opportunities for Action” management plan. Estimates of concentration and flux were provided for each tributary based on (1) observed daily discharges and (2) a flow-normalizing procedure, which removed the random fluctuations of climate-related variability. The flux bias statistic, an indicator of the ability of the Weighted Regressions on Time, Discharge, and Season regression models to provide accurate representations of flux, showed acceptable bias (less than ±10 percent) for 68 out of 72 models for total and dissolved phosphorus, total nitrogen, and chloride. Six out of 18 models for total suspended solids had moderate bias (between 10 and 30 percent), an expected result given the frequently nonlinear relation between total suspended solids and discharge. One model for total suspended solids with a very high bias was influenced by a single extreme value; however, removal of that value, although reducing the bias substantially, had little effect on annual fluxes.

  2. Atmospheric fluxes of organic matter to the Mediterranean Sea: contribution to the elemental C: N: P ratios of surface dissolved organic matter

    Science.gov (United States)

    Djaoudi, Kahina; Barani, Aude; Hélias-Nunige, Sandra; Van Wambeke, France; Pulido-Villena, Elvira

    2016-04-01

    It has become increasingly apparent that atmospheric transport plays an important role in the supply of macro- and micro-nutrients to the surface ocean. This atmospheric input is especially important in oligotrophic regions where the vertical supply from the subsurface is low particularly during the stratification period. Compared to its inorganic counterpart, the organic fraction of atmospheric deposition and its impact on surface ocean biogeochemistry has been poorly explored. In the ocean, carbon export to depth (and therefore, its long term storage with presumed consequences on climate) occurs both through particle sedimentation and through the transfer of dissolved organic matter (DOM) via diffusion or convection. DOM export from the surface ocean represents up to 50% of total organic carbon flux to the deep ocean in oligotrophic regions such as the Mediterranean Sea. The efficiency of this C export pathway depends, among others, on the elemental C: N: P ratios of surface DOM which might be affected by the relative contribution of microbial processes and allochthonous sources. This work reports a one-year time-series (April 2015-April 2016) of simultaneous measurements of (1) total (dry + wet) atmospheric fluxes of organic carbon, organic nitrogen, and organic phosphorus and (2) concentration of dissolved organic carbon, dissolved organic nitrogen, and dissolved organic phosphate at the surface layer (0-200 m) in the NW Mediterranean Sea. Atmospheric and oceanic surveys were conducted at the Frioul and ANTARES sites, respectively, operated by the long-term observation network MOOSE (Mediterranean Oceanic Observation System for the Environment).

  3. Soil CO2 flux in relation to dissolved organic carbon, soil temperature and moisture in a subtropical arable soil of China

    Institute of Scientific and Technical Information of China (English)

    LOU Yun-sheng; LI Zhong-pei; ZHANG Tao-lin

    2003-01-01

    Soil CO2 emission from an arable soil was measured by closed chamber method to quantify year-round soil flux and to develop an equation to predict flux using soil temperature, dissolved organic carbon(DOC) and soil moisture content. Soil CO2 flux, soil temperature, DOC and soil moisture content were determined on selected days during the experiment from August 1999 to July 2000, at the Ecological Station of Red Soil, the Chinese Academy of Sciences, in a subtropical region of China. Soil CO2 fluxes were generally higher in summer and autumn than in winter and spring, and had a seasonal pattern more similar to soil temperature and DOC than soil moisture. The estimation was 2.23 kgCO2/(m2·a) for average annual soil CO2 flux. Regressed separately, the reasons for soil flux variability were 86.6% from soil temperature, 58.8% from DOC, and 26.3% from soil moisture, respectively. Regressed jointly, a multiple equation was developed by the above three variables that explained approximately 85.2% of the flux variance, however by stepwise regression, soil temperature was the dominant affecting soil flux. Based on the exponential equation developed from soil temperature, the predicted annual flux was 2.49 kgCO2/(m2·a), and essentially equal to the measured one. It is suggested the exponential relationship between soil flux and soil temperature could be used for accurately predicting soil CO2 flux from arable soil in subtropical regions of China.

  4. Fluxes of dissolved organic matter and mineral weathering products from Corn Belt landscapes dominated by subsurface drainage: large-scale soil and hydrologic change

    Science.gov (United States)

    Jelinski, N. A.; Yoo, K.; Strock, J.; Dalzell, B. J.; Finlay, J. C.

    2011-12-01

    The human alteration of agricultural landscapes is one of the most important factors in pedologic and geomorphic change, and can influence hydrology and aquatic chemistry at large scales. Most of the Midwestern Corn Belt that is currently dominated by subsurface tile drainage (such as southern Minnesota) was historically prairie and wetland which had hydrologic flow-paths through organic-rich surface soil horizons, a condition that favored the export of dissolved organic matter. When hydrology is altered through subsurface drainage, adsorption of organic materials to mineral surfaces and increases in mineral weathering may result because more water is flowing through subsurface mineral soils. We suggest that the alteration of hydrologic flowpaths in agricultural landscapes can dramatically alter the rate of mineral weathering as well as surface export of weathering products and dissolved organic matter. This could be at least one contributing factor to observed increases in Mississippi River alkalinity over the past four decades. Here, we examine trends in dissolved organic carbon, total dissolved nitrogen, dissolved organic nitrogen, total suspended solids, and indicators of mineral weathering (Si, Ca, Na, K) from subsurface drainage systems located in southwestern MN. Then, using a simple conceptual model, we estimate the effects of subsurface drainage on the regional fluxes of these parameters and present directions for future research.

  5. High resolution measurements of methane and carbon dioxide in surface waters over a natural seep reveal dynamics of dissolved phase air-sea flux.

    Science.gov (United States)

    Du, Mengran; Yvon-Lewis, Shari; Garcia-Tigreros, Fenix; Valentine, David L; Mendes, Stephanie D; Kessler, John D

    2014-09-01

    Marine hydrocarbon seeps are sources of methane and carbon dioxide to the ocean, and potentially to the atmosphere, though the magnitude of the fluxes and dynamics of these systems are poorly defined. To better constrain these variables in natural environments, we conducted the first high-resolution measurements of sea surface methane and carbon dioxide concentrations in the massive natural seep field near Coal Oil Point (COP), California. The corresponding high resolution fluxes were calculated, and the total dissolved phase air-sea fluxes over the surveyed plume area (∼363 km(2)) were 6.66 × 10(4) to 6.71 × 10(4) mol day(-1) with respect to CH4 and -6.01 × 10(5) to -5.99 × 10(5) mol day(-1) with respect to CO2. The mean and standard deviation of the dissolved phase air-sea fluxes of methane and carbon dioxide from the contour gridding analysis were estimated to be 0.18 ± 0.19 and -1.65 ± 1.23 mmol m(-2) day(-1), respectively. This methane flux is consistent with previous, lower-resolution estimates and was used, in part, to conservatively estimate the total area of the dissolved methane plume at 8400 km(2). The influx of carbon dioxide to the surface water refutes the hypothesis that COP seep methane appreciably influences carbon dioxide dynamics. Seeing that the COP seep field is one of the biggest natural seeps, a logical conclusion could be drawn that microbial oxidation of methane from natural seeps is of insufficient magnitude to change the resulting plume area from a sink of atmospheric carbon dioxide to a source.

  6. Influence of neutron flux, frequency and temperature to electrical impedance of nano silica particles

    Energy Technology Data Exchange (ETDEWEB)

    Huseynov, Elchin, E-mail: hus.elchin@yahoo.com, E-mail: hus.elchin@gmail.com; Garibov, Adil; Mehdiyeva, Ravan [Institute of Radiation Problems of Azerbaijan National Academy of Sciences, AZ 1143, B.Vahabzadeh 9, Baku (Azerbaijan); Andreja, Eršte, E-mail: andreja.erste@ijs.si [Condensed Matter Physics Department, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana Slovenia (Slovenia); Rustamov, Anar, E-mail: a.rustamov@cern.ch [Goethe-Universität Frankfurt, Max-von-Laue-Str. 1, 60438 Frankfurt am Main (Germany)

    2014-11-15

    We studied electric impedance of SiO{sub 2} nanomaterial at its initial state and after being exposed to continuous neutron irradiation for up to 20 hours. In doing so we employed a flux of neutrons of 2x10{sup 13} n⋅cm{sup −2}s{sup −1} while the frequency and temperature ranges amounted to 0,09 – 2.3 MHz and 100 – 400 K correspondingly. Analysis in terms of the Cole-Cole expression revealed that with increasing irradiation period the polarization and relaxation times decrease as a result of combination of nanoparticles. Moreover, it is demonstrated that the electric conductivity of samples, on the other hand, increases with the increasing irradiation period. At low temperatures formations of clusters at three distinct states with different energies were resolved.

  7. Quantifying fluxes and characterizing compositional changes of dissolved organic matter in aquatic systems in situ using combined acoustic and optical measurements

    Science.gov (United States)

    Downing, B.D.; Boss, E.; Bergamaschi, B.A.; Fleck, J.A.; Lionberger, M.A.; Ganju, N.K.; Schoellhamer, D.H.; Fujii, R.

    2009-01-01

    Studying the dynamics and geochemical behavior of dissolved and particulate organic material is difficult because concentration and composition may rapidly change in response to aperiodic as well as periodic physical and biological forcing. Here we describe a method useful for quantifying fluxes and analyzing dissolved organic matter (DOM) dynamics. The method uses coupled optical and acoustic measurements that provide robust quantitative estimates of concentrations and constituent characteristics needed to investigate processes and calculate fluxes of DOM in tidal and other lotic environments. Data were collected several times per hour for 2 weeks or more, with the frequency and duration limited only by power consumption and data storage capacity. We assessed the capabilities and limitations of the method using data from a winter deployment in a natural tidal wetland of the San Francisco Bay estuary. We used statistical correlation of in situ optical data with traditional laboratory analyses of discrete water samples to calibrate optical properties suited as proxies for DOM concentrations and characterizations. Coupled with measurements of flow velocity, we calculated long-term residual horizontal fluxes of DOC into and out from a tidal wetland. Subsampling the dataset provides an estimate for the maximum sampling interval beyond which the error in flux estimate is significantly increased.?? 2009, by the American Society of Limnology and Oceanography, Inc.

  8. High flux, positively charged loose nanofiltration membrane by blending with poly (ionic liquid) brushes grafted silica spheres

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Liang [School of Chemical Engineering and Energy, Zhengzhou University, Zhengzhou 450001 (China); Zhang, Yatao, E-mail: zhangyatao@zzu.edu.cn [School of Chemical Engineering and Energy, Zhengzhou University, Zhengzhou 450001 (China); UNESCO Center for Membrane Science and Technology, School of Chemical Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Wang, Yuanming; Zhang, Haoqin [School of Chemical Engineering and Energy, Zhengzhou University, Zhengzhou 450001 (China); Liu, Jindun, E-mail: liujindun@zzu.edu.cn [School of Chemical Engineering and Energy, Zhengzhou University, Zhengzhou 450001 (China)

    2015-04-28

    Highlights: • SiO{sub 2} spheres were modified by poly (ionic liquid) brushes via RATRP. • Positively charged NF membranes were fabricated by incorporation of SiO{sub 2}-PIL. • The membranes exhibited higher rejection for dyes and superior penetration for salts. - Abstract: Silica spheres modified by poly (ionic liquid) brushes, a novel positively charged nanomaterial is prepared by atom transfer radical polymerization (ATRP). A high flux positively charged loose nanofiltration membrane is fabricated via “blending-phase inversion” method. The morphology structures, hydrophilicity, thermal and mechanical properties, permeation performance of these membranes are investigated in detail. The results reveal that the hybrid membranes have enhanced surface hydrophilicity, water permeability, thermal stability, and mechanical properties. Characterization of membrane separation properties shows that the hybrid membranes possess higher salt permeability and relatively higher rejection for reactive dyes, which may open opportunities for the recycling of reactive dyes wastewater. Moreover, such hybrid membranes have an outstanding operational stability and salts concentration showed little effect on the separation properties.

  9. Dissolved organic matter and lake metabolism: Biogeochemistry and controls of nutrient flux dynamics to fresh waters. Technical progress report, January 1, 1990--December 31, 1991

    Energy Technology Data Exchange (ETDEWEB)

    Wetzel, R.G.

    1992-12-31

    The land-water interface region consists of two major components: the wetland, and the down-gradient adjacent littoral floating-leaved and submersed, macrophyte communities. Because of the importance of very high production and nutrient turnover of attached microbiota, a major emphasis of this investigation was placed upon these biota and their metabolic capacities for assimilation and release of organic compounds and nutrient retention and cycling. Examination of the capacities of wetland littoral communities to regulate fluxes of nutrients and organic compounds often has been limited to input-output analyses. These input-output data are an integral part of these investigations, but most of the research effort concentrated on the biotic and metabolic mechanisms that control fluxes and retention capacities and their effects upon biota in the down-gradient waters. The important regulatory capacities of dissolved organic compounds on enzyme reactivity was examined experimentally and coupled to the wetland-littoral organic carbon flux budgets.

  10. Reduction of calcium flux from the extracellular region and endoplasmic reticulum by amorphous nano-silica particles owing to carboxy group addition on their surface

    Directory of Open Access Journals (Sweden)

    Akira Onodera

    2017-03-01

    Full Text Available Several studies have reported that amorphous nano-silica particles (nano-SPs modulate calcium flux, although the mechanism remains incompletely understood. We thus analyzed the relationship between calcium flux and particle surface properties and determined the calcium flux route. Treatment of Balb/c 3T3 fibroblasts with nano-SPs with a diameter of 70 nm (nSP70 increased cytosolic calcium concentration, but that with SPs with a diameter of 300 or 1000 nm did not. Surface modification of nSP70 with a carboxy group also did not modulate calcium flux. Pretreatment with a general calcium entry blocker almost completely suppressed calcium flux by nSP70. Preconditioning by emptying the endoplasmic reticulum (ER calcium stores slightly suppressed calcium flux by nSP70. These results indicate that nSP70 mainly modulates calcium flux across plasma membrane calcium channels, with subsequent activation of the ER calcium pump, and that the potential of calcium flux by nano-SPs is determined by the particle surface charge.

  11. Satellite-Derived Distributions, Inventories and Fluxes of Dissolved and Particulate Organic Matter Along the Northeastern U.S. Continental Margin

    Science.gov (United States)

    Mannino, A.; Hooker, S. B.; Hyde, K.; Novak, M. G.; Pan, X.; Friedrichs, M.; Cahill, B.; Wilkin, J.

    2011-01-01

    Estuaries and the coastal ocean experience a high degree of variability in the composition and concentration of particulate and dissolved organic matter (DOM) as a consequence of riverine and estuarine fluxes of terrigenous DOM, sediments, detritus and nutrients into coastal waters and associated phytoplankton blooms. Our approach integrates biogeochemical measurements, optical properties and remote sensing to examine the distributions and inventories of organic carbon in the U.S. Middle Atlantic Bight and Gulf of Maine. Algorithms developed to retrieve colored DOM (CDOM), Dissolved (DOC) and Particulate Organic Carbon (POC) from NASA's MODIS-Aqua and SeaWiFS satellite sensors are applied to quantify the distributions and inventories of DOC and POC. Horizontal fluxes of DOC and POC from the continental margin to the open ocean are estimated from SeaWiFS and MODIS-Aqua distributions of DOC and POC and horizontal divergence fluxes obtained from the Northeastern North Atlantic ROMS model. SeaWiFS and MODIS imagery reveal the importance of estuarine outflow to the export of CDOM and DOC to the coastal ocean and a net community production of DOC on the shelf.

  12. Distribution and production of reactive mercury and dissolved gaseous mercury in surface waters and water/air mercury flux in reservoirs on Wujiang River, Southwest China

    Science.gov (United States)

    Fu, Xuewu; Feng, Xinbin; Guo, Yanna; Meng, Bo; Yin, Runsheng; Yao, Heng

    2013-05-01

    Transformation and distribution of mercury (Hg) species play an important role in the biogeochemical cycling of mercury in aquatic systems. Measurements of water/air exchange fluxes of Hg, reactive mercury (RHg), and dissolved gaseous mercury (DGM) concentrations were conducted at 14 sites in five reservoirs on the Wujiang River, Guizhou, Southwest China. Clear spatial and temporal variations in Hg fluxes, RHg, and DGM concentrations were observed in the study area. Hg fluxes and RHg concentrations exhibited a consistent diurnal variation in the study area, with maximum fluxes and concentrations during daytime. A typical diurnal trend of DGM with elevated concentration at night was observed in a eutrophic reservoir with elevated bacteria abundance, suggesting a bacteria-induced production of DGM in this reservoir. For other reservoirs, a combination of sunlight-stimulated production and loss via photo-induced oxidation and evaporation regulated the diurnal trends of DGM. Seasonal variations with elevated Hg fluxes and RHg concentrations in warm season were noticeable in the study area, which highlighted the combined effect of interrelationships between Hg species in water and environmental parameters. Hg fluxes exhibited much more significant correlations with RHg and THg concentrations and air temperature compared to DGM concentrations and solar radiation. The measured fluxes were significantly higher than those simulated using the water/air thin film Hg0 gradient model. Aside from the potential limitations of dynamic flux chamber method, this may also suggest the thin film gas exchange model is not capable of predicting water/air Hg flux under low wind speed conditions. Additionally, it is speculated that DGM concentrations might vary significantly in surface waters with depth, and measurements of DGM at a depth of 2-4 cm below the water surface probably underestimated the DGM concentration that should be taken into account in simulations of water/air flux using

  13. Fluxes of dissolved aluminum and manganese to the Weddell Sea and indications for manganese co-limitation

    NARCIS (Netherlands)

    Middag, Rob; de Baar, Hein J. W.; Klunder, Maarten B.; Laan, Patrick

    The trace metals aluminum (Al) and manganese (Mn) were studied in the Weddell Sea in March 2008. Concentrations of dissolved Al ([Al]) were slightly elevated (0.23-0.35 nmol L-1) in the surface layer compared to the subsurface minimum (0.07-0.21 nmol L-1) observed in the winter water. Atmospheric

  14. Fluxes of dissolved aluminum and manganese to the Weddell Sea and indications for manganese co-limitation

    NARCIS (Netherlands)

    Middag, R.; de Baar, H.J.W.; Klunder, M.B.; Laan, P.

    2013-01-01

    The trace metals aluminum (Al) and manganese (Mn) were studied in the Weddell Sea in March 2008. Concentrations of dissolved Al ([Al]) were slightly elevated (0.23-0.35 nmol L-1) in the surface layer compared to the subsurface minimum (0.07-0.21 nmol L-1) observed in the winter water. Atmospheric

  15. Dissolved methane in the Beaufort Sea and the Arctic Ocean, 1992-2009; sources and atmospheric flux

    Science.gov (United States)

    Lorenson, Thomas D.; Greinert, Jens; Coffin, Richard B.

    2016-01-01

    Methane concentration and isotopic composition was measured in ice-covered and ice-free waters of the Arctic Ocean during eleven surveys spanning the years of 1992-1995 and 2009. During ice-free periods, methane flux from the Beaufort shelf varies from 0.14 to 0.43 mg CH4 m-2 day-1. Maximum fluxes from localized areas of high methane concentration are up to 1.52 mg CH4 m-2 day-1. Seasonal buildup of methane under ice can produce short-term fluxes of methane from the Beaufort shelf that varies from 0.28 to 1.01 to mg CH4 m-2 day-1. Scaled-up estimates of minimum methane flux from the Beaufort Sea and pan-Arctic shelf for both ice-free and ice-covered periods range from 0.02 Tg CH4 yr-1 and 0.30 Tg CH4 yr-1 respectively to maximum fluxes of 0.18 Tg CH4 yr-1 and 2.2 Tg CH4 yr-1 respectively. A methane flux of 0.36 Tg CH4 yr-1from the deep Arctic Ocean was estimated using data from 1993-94. The flux can be as much as 2.35 Tg CH4 yr-1 estimated from maximum methane concentrations and wind speeds of 12 m/s, representing only 0.42% of the annual atmospheric methane budget of ~560 Tg CH4 yr-1. There were no significant changes in methane fluxes during the time period of this study. Microbial methane sources predominate with minor influxes from thermogenic methane offshore Prudhoe Bay and the Mackenzie River delta and may include methane from gas hydrate. Methane oxidation is locally important on the shelf and is a methane sink in the deep Arctic Ocean.

  16. Natural Radium Detection and Inventory Flux of Isotopes in Particulate and Dissolved Phases of Seawater at Kapar Coastal Area Caused by Coal-Fired Power Plant

    Science.gov (United States)

    Mohamed, N.; Ariffin, N. A. N.; Mohamed, C. A. R.

    2016-07-01

    Distribution of 226Ra and 228Ra radioactive in marine have been studied at Kapar coastal area that closed to Sultan Salahudin Abdul Aziz Shah (SJSSAS) power station. The concentration level of 226Ra and 228Ra were measured in seawater include total suspended solids (TSSrw) and dissolved phases from September 2006 to February 2008. The measurement technique used for 226Ra and 228Ra was using cation exchange column and counted using Liquid Scintillator Ciunter (LSC). The radioactivities of 226Rasw and 228Rasw in the dissolved phase of seawater ranged from 1.29 ± 0.52 mBq/L - 3.69 ± 1.29 mBq/L and 2.12 ± 0.71 mbq/L - 17.07 ± 6.03 mBq/L respectively. The measurement of radioactivities of radium isotopes in the particulate phase of seawater ranged from 15.62 ± 1.99 Bq/kg - 241.76 ± 100.23 Bq/kg (226Ratsw) and 7.19 ± 3.21 Bq/kg - 879.66 ± 365.74 Bq/kg (228Ratsw). Radium isotopes inventory in this study showed that suspended solid have higher inventory value than seawater and sediment. Study also found that suspended solid play an important role for flux contribution at seawater. Based on the finding, the radioactivity concentration of 226Ra and 228Ra is higher in particulate phase than in dissolved phase.

  17. Dynamics of submarine groundwater discharge and associated fluxes of dissolved nutrients, carbon, and trace gases to the coastal zone (Okatee River estuary, South Carolina)

    Science.gov (United States)

    Porubsky, W.P.; Weston, N.B.; Moore, W.S.; Ruppel, C.; Joye, S.B.

    2014-01-01

    Multiple techniques, including thermal infrared aerial remote sensing, geophysical and geological data, geochemical characterization and radium isotopes, were used to evaluate the role of groundwater as a source of dissolved nutrients, carbon, and trace gases to the Okatee River estuary, South Carolina. Thermal infrared aerial remote sensing surveys illustrated the presence of multiple submarine groundwater discharge sites in Okatee headwaters. Significant relationships were observed between groundwater geochemical constituents and 226Ra activity in groundwater with higher 226Ra activity correlated to higher concentrations of organics, dissolved inorganic carbon, nutrients, and trace gases to the Okatee system. A system-level radium mass balance confirmed a substantial submarine groundwater discharge contribution of these constituents to the Okatee River. Diffusive benthic flux measurements and potential denitrification rate assays tracked the fate of constituents in creek bank sediments. Diffusive benthic fluxes were substantially lower than calculated radium-based submarine groundwater discharge inputs, showing that advection of groundwater-derived nutrients dominated fluxes in the system. While a considerable potential for denitrification in tidal creek bank sediments was noted, in situ denitrification rates were nitrate-limited, making intertidal sediments an inefficient nitrogen sink in this system. Groundwater geochemical data indicated significant differences in groundwater chemical composition and radium activity ratios between the eastern and western sides of the river; these likely arose from the distinct hydrological regimes observed in each area. Groundwater from the western side of the Okatee headwaters was characterized by higher concentrations of dissolved organic and inorganic carbon, dissolved organic nitrogen, inorganic nutrients and reduced metabolites and trace gases, i.e. methane and nitrous oxide, than groundwater from the eastern side

  18. Fluxes of dissolved organic carbon and nitrogen to the northern Indian Ocean from the Indian monsoonal rivers

    Digital Repository Service at National Institute of Oceanography (India)

    Krishna, M.S.; Prasad, V.R.; Sarma, V.V.S.S.; Reddy, N.P.C.; Hemalatha, K.P.J.; Rao, Y.V.

    [Bin and Longjun, 2011], domestic and industrial sewage, besides the input from autochthonous sources, such as phytoplankton [Carlson et al., 1994; Bianchi et al., 2004], bacteria and macrophytes [Bronk et al., 1994; Diaz and Raimbault, 2000... transport in the Columbia River, Estuar. Coast. Shelf Sci., 13, 645-658. Diaz, F., and P. Raimbault (2000), Nitrogen regeneration and dissolved organic nitrogen release during spring in a NW Mediterranean coastal zone (Gulf of Lions): implications...

  19. Using 224Ra/228Th disequilibrium to quantify benthic fluxes of dissolved inorganic carbon and nutrients into the Pearl River Estuary

    Science.gov (United States)

    Cai, Pinghe; Shi, Xiangming; Hong, Qingquan; Li, Qing; Liu, Lingfeng; Guo, Xianghui; Dai, Minhan

    2015-12-01

    The 224Ra/228Th disequilibrium that was recently observed in coastal sediments has been proven to be an excellent proxy for tracing the benthic processes that regulate solute transfer across the sediment-water interface. In order to better utilize this proxy, there is a need to understand the reaction kinetics of 224Ra in sediments. In this study, depth profiles of 224Ra and 228Th in bulk sediments were collected along a transect in the Pearl River Estuary (PRE). Together with bulk sediment measurements, dissolved 224Ra, dissolved inorganic carbon (DIC), and nutrients (NO2- + NO3-, NH4+) in pore water and in the overlying waters were also determined. A marked deficit of 224Ra with respect to 228Th with large spatial variations was observed in the PRE sediments. By use of a diagenetic model for the distributions of dissolved and adsorbed 224Ra in sediments, we infer that adsorption removes 224Ra from aqueous phase at a rate of 0.1 ± 1.1-2000 ± 400 d-1. In addition, adsorption of 224Ra exhibits a rate sequence of oxic freshwater > anoxic freshwater > anoxic brackish water, probably reflecting the effect of the redox conditions and ionic strength on the adsorption-desorption kinetics of 224Ra. Benthic fluxes of 224Ra were estimated from the observed deficit of 224Ra in the sediments using a one-dimensional (1D) mass balance exchange model. We demonstrated that irrigation was the predominant process that controls solute transfer across the sediment-water interface, whereas molecular diffusion and sediment mixing together contributed <5% of the total 224Ra fluxes from bottom sediments. We then utilized the 224Ra/228Th disequilibrium approach to quantify the benthic fluxes of DIC and nutrients. We showed that sediment interstitial waters delivered approximately 42 ± 6 × 109 mol of DIC and ˜16 ± 1 × 109 mol of NH4+ into the PRE in the dry season. In contrast, it removed about 13 ± 1 × 109 mol of NO3- from the overlying water column. The benthic flux of DIC is

  20. Evaluation of high-frequency mean streamwater transit-time estimates using groundwater age and dissolved silica concentrations in a small forested watershed

    Science.gov (United States)

    Peters, Norman E.; Burns, Douglas A.; Aulenbach, Brent T.

    2014-01-01

    Many previous investigations of mean streamwater transit times (MTT) have been limited by an inability to quantify the MTT dynamics. Here, we draw on (1) a linear relation (r 2 = 0.97) between groundwater 3H/3He ages and dissolved silica (Si) concentrations, combined with (2) predicted streamwater Si concentrations from a multiple-regression relation (R 2 = 0.87) to estimate MTT at 5-min intervals for a 23-year time series of streamflow [water year (WY) 1986 through 2008] at the Panola Mountain Research Watershed, Georgia. The time-based average MTT derived from the 5-min data was ~8.4 ± 2.9 years and the volume-weighted (VW) MTT was ~4.7 years for the study period, reflecting the importance of younger runoff water during high flow. The 5-min MTTs are normally distributed and ranged from 0 to 15 years. Monthly VW MTTs averaged 7.0 ± 3.3 years and ranged from 4 to 6 years during winter and 8–10 years during summer. The annual VW MTTs averaged 5.6 ± 2.0 years and ranged from ~5 years during wet years (2003 and 2005) to >10 years during dry years (2002 and 2008). Stormflows are composed of much younger water than baseflows, and although stormflow only occurs ~17 % of the time, this runoff fraction contributed 39 % of the runoff during the 23-year study period. Combining the 23-year VW MTT (including stormflow) with the annual average baseflow for the period (~212 mm) indicates that active groundwater storage is ~1,000 mm. However, the groundwater storage ranged from 1,040 to 1,950 mm using WY baseflow and WY VW MTT. The approach described herein may be applicable to other watersheds underlain by granitoid bedrock, where weathering is the dominant control on Si concentrations in soils, groundwater, and streamwater.

  1. Importance of dissolved organic carbon flux through submarine groundwater discharge to the coastal ocean: Results from Masan Bay, the southern coast of Korea

    Science.gov (United States)

    Oh, Yong Hwa; Lee, Yong-Woo; Park, Sang Rul; Kim, Tae-Hoon

    2017-09-01

    In order to estimate the fluxes of dissolved organic carbon (DOC) through submarine groundwater discharge (SGD), salinity and DOC concentrations in groundwater, stream water, and seawater were investigated in May 2006 and 2007 (dry season) and August 2006 (wet season) in Masan Bay, Korea. In both seasons, the average concentrations of DOC in groundwater (139 ± 23 μM in May and 113 ± 18 μM in August) were relatively lower than those in stream water (284 ± 104 μM in May and 150 ± 36 μM in August) but similar to those of the bay water (149 ± 17 μM in May and 117 ± 13 μM in August). The DOC concentrations in groundwater, stream water, and seawater showed negative relationships with salinity, but those in the surface bay water were observed above the theoretical mixing line, indicating that DOC may be produced by in situ primary production in this bay. Based on a simple DOC mass balance model, SGD-derived DOC fluxes in Masan Bay were estimated to be 6.7 × 105 mol d- 1 in the dry season and 6.4 × 105 mol d- 1 in the wet season, showing no remarkable seasonal variation. The DOC fluxes through SGD in Masan Bay accounted for approximately 65% of the total input fluxes. This result suggests that the DOC flux through SGD can be the most important source of DOC in this bay, and SGD may play an important role in carbon budget and biogeochemistry in coastal areas.

  2. Comparison of two measurement methods of dissolved gaseous mercury concentrations and estimations of supersaturation grade and mercury fluxes during a research campaign at the Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    Nerentorp M.

    2013-04-01

    Full Text Available Dissolved gaseous mercury (DGM concentrations and gaseous elemental mercury (GEM concentrations were measured during an oceanographic campaign in the Mediterranean Sea. The DGM concentrations were measured using two different methods, a manual- and an automated method. The manual method was used to obtain DGM depth profiles at several stations throughout the campaign. The automated device measured DGM concentrations continuously at a depth of 4 m. Gaseous elemental mercury (GEM concentrations in air were measured continuously at the bridge deck. The objectives were to achieve DGM depth profiles, compare the manual- and automated DGM measurement methods, to calculate the supersaturation grades of the sea and the evasional fluxes from the sea surface. Depth profiles of the four measured stations show no diurnal variations. The manual- and the automated method show good compliance. Supersaturation grades are high due to high DGM values and low GEM concentrations. Fluxes of Hg from the sea surface are more dependent on the wind speed than on the supersaturation grade according to the flux models used.

  3. Dissolved inorganic carbon and alkalinity fluxes from coastal marine sediments: model estimates for different shelf environments and sensitivity to global change

    Directory of Open Access Journals (Sweden)

    V. Krumins

    2012-07-01

    Full Text Available We present a one-dimensional reactive transport model to estimate benthic fluxes of dissolved inorganic carbon (DIC and alkalinity (AT from coastal marine sediments. The model incorporates the transport processes of sediment accumulation, molecular diffusion, bioturbation and bioirrigation, while the reactions included are the redox pathways of organic carbon oxidation, re-oxidation of reduced nitrogen, iron and sulfur compounds, pore water acid-base equilibria, and dissolution of particulate inorganic carbon (calcite, aragonite, and Mg-calcite. The coastal zone is divided into four environmental units with different particulate inorganic carbon (PIC and particulate organic carbon (POC fluxes: reefs, banks and bays, carbonate shelves and non-carbonate shelves. Model results are analyzed separately for each environment and then scaled up to the whole coastal ocean. The model-derived estimate for the present-day global coastal benthic DIC efflux is 126 Tmol yr−1, based on a global coastal reactive POC depositional flux of 117 Tmol yr−1. The POC decomposition leads to a~carbonate dissolution from shallow marine sediments of 7 Tmol yr−1 (on the order of 0.1 Pg C yr−1. Assuming complete re-oxidation of aqueous sulfide released from sediments, the effective net flux of alkalinity to the water column is 29 Teq yr−1, primarily from PIC dissolution (46% and ammonification (33%. Because our POC depositional flux falls in the high range of global values given in the literature, the reported DIC and alkalinity fluxes should be viewed as upper-bound estimates. Increasing coastal seawater DIC to what might be expected in year 2100 due to the uptake of anthropogenic CO2 increases PIC dissolution by 2.3 Tmol yr−1 and alkalinity efflux by 4.8 Teq yr−1. Our reactive transport modeling approach not only yields global estimates of benthic DIC, alkalinity

  4. Impact of the natural Fe-fertilization on the magnitude, stoichiometry and efficiency of particulate biogenic silica, nitrogen and iron export fluxes

    Science.gov (United States)

    Lemaitre, N.; Planquette, H.; Dehairs, F.; van der Merwe, P.; Bowie, A. R.; Trull, T. W.; Laurenceau-Cornec, E. C.; Davies, D.; Bollinger, C.; Le Goff, M.; Grossteffan, E.; Planchon, F.

    2016-11-01

    The Kerguelen Plateau is characterized by a naturally Fe-fertilized phytoplankton bloom that extends more than 1000 km downstream in the Antarctic Circumpolar Current. During the KEOPS2 study, in austral spring, we measured particulate nitrogen (PN), biogenic silica (BSi) and particulate iron (PFe) export fluxes in order to investigate how the natural fertilization impacts the stoichiometry and the magnitude of export fluxes and therefore the efficiency of the biological carbon pump. At 9 stations, we estimated elemental export fluxes based on element concentration to 234Th activity ratios for particulate material collected with in-situ pumps and 234Th export fluxes (Planchon et al., 2015). This study revealed that the natural Fe-fertilization increased export fluxes but to variable degrees. Export fluxes for the bloom impacted area were compared with those of a high-nutrient, low-chlorophyll (HNLC), low-productive reference site located to the south-west of Kerguelen and which had the lowest BSi and PFe export fluxes (2.55 mmol BSi m-2 d-1 and 1.92 μmol PFem-2 d-1) and amongst the lowest PN export flux (0.73 mmol PN m-2 d-1). The impact of the Fe fertilization was the greatest within a meander of the polar front (PF), to the east of Kerguelen, with fluxes reaching 1.26 mmol PN m-2 d-1; 20.4 mmol BSi m-2 d-1 and 22.4 μmol PFe m-2 d-1. A highly productive site above the Kerguelen Plateau, on the contrary, was less impacted by the fertilization with export fluxes reaching 0.72 mmol PN m-2 d-1; 4.50 mmol BSi m-2 d-1 and 21.4 μmol PFe m-2 d-1. Our results suggest that ecosystem features (i.e. type of diatom community) could play an important role in setting the magnitude of export fluxes of these elements. Indeed, for the PF meander, the moderate productivity was sustained by the presence of large and strongly silicified diatom species while at the higher productivity sites, smaller and slightly silicified diatoms dominated. Interestingly, our results suggest that

  5. Large increase in dissolved inorganic carbon flux from the Mississippi River to Gulf of Mexico due to climatic and anthropogenic changes over the 21st century.

    Science.gov (United States)

    Ren, Wei; Tian, Hanqin; Tao, Bo; Yang, Jia; Pan, Shufen; Cai, Wei-Jun; Lohrenz, Steven E; He, Ruoying; Hopkinson, Charles S

    2015-04-01

    It is recognized that anthropogenic factors have had a major impact on carbon fluxes from land to the ocean during the past two centuries. However, little is known about how future changes in climate, atmospheric CO2, and land use may affect riverine carbon fluxes over the 21st century. Using a coupled hydrological-biogeochemical model, the Dynamic Land Ecosystem Model, this study examines potential changes in dissolved inorganic carbon (DIC) export from the Mississippi River basin to the Gulf of Mexico during 2010-2099 attributable to climate-related conditions (temperature and precipitation), atmospheric CO2, and land use change. Rates of annual DIC export are projected to increase by 65% under the high emission scenario (A2) and 35% under the low emission scenario (B1) between the 2000s and the 2090s. Climate-related changes along with rising atmospheric CO2 together would account for over 90% of the total increase in DIC export throughout the 21st century. The predicted increase in DIC export from the Mississippi River basin would alter chemistry of the coastal ocean unless appropriate climate mitigation actions are taken in the near future.

  6. Dissolved inorganic nitrogen pools and surface flux under different brackish marsh vegetation types, common reed (Phragmites australis) and salt hay (Spartina patens)

    Science.gov (United States)

    Windham-Myers, L.

    2005-01-01

    The current expansion of Phragmites australis into the high marsh shortgrass (Spartina patens, Distichlis spicata) communities of eastern U.S. salt marshes provided an opportunity to identify the influence of vegetation types on pools and fluxes of dissolved inorganic nitrogen (DIN). Two brackish tidal marshes of the National Estuarine Research Reserve system were examined, Piermont Marsh of the Hudson River NERR in New York and Hog Island in the Jacques Coustaeu NERR of New Jersey. Pools of DIN in porewater and rates of DIN surface flux were compared in replicated pairs of recently-expanded P. australis and neighboring S. patens-dominated patches on the high marsh surface. Both marshes generally imported nitrate (NO3-) and exported ammonium (NH4+), such that overall DIN was exported. No differences in surface exchange of NO3- or NH4+ were observed between vegetation types. Depth-averaged porewater NH4+ concentrations over the entire growing season were 56% lower under P. australis than under S. patens (average 1.4 vs. 3.2 mg NH4+ L-1) with the most profound differences in November. Porewater profiles showed an accumulation of NH4+ at depth in S. patens and constant low concentrations in P. australis from the soil surface to 50 cm depth, with no significant differences in porewater salinity. Despite these profound differences in porewater, NH 4+ diffusion from soils of P. australis and S. patens were not measurably different, were similar to other published rates, and were well below estimated rates based on passive diffusion alone. Rapid adsorption and uptake by litter and microbes in surface soils of both communities may buffer NH4+ loss to flooding tides in both communities, thereby reducing the impact of P. australis invasion on NH4+ flux to flooding waters. ?? Springer 2005.

  7. Effects of wind farm construction on concentrations and fluxes of dissolved organic carbon and suspended sediment from peat catchments at Braes of Doune, central Scotland

    Directory of Open Access Journals (Sweden)

    I. Grieve

    2008-07-01

    Full Text Available This paper assesses the impacts of disturbance associated with the construction of a wind farm on fluxes of dissolved organic carbon (DOC and suspended sediment from a blanket peat catchment in central Scotland during the period immediately following completion of construction. Six streams draining the site were sampled on six dates from October 2006, when construction was completed, and an additional three control streams to the west of the site were sampled on the same dates. Turbidity and stage were recorded semi-continuously in the two largest streams (one disturbed and one control, which were also sampled during storm events. Absorbance (400 nm and DOC concentrations were determined on all samples, and suspended sediment was determined on the event samples. Absorbance and DOC were closely correlated in both the disturbed and undisturbed streams, with slightly greater absorbance per unit DOC in the disturbed streams. DOC concentrations in disturbed tributaries were always greater than those in undisturbed streams, with mean differences ranging from 2 to around 5 mg L-1. DOC and stage were positively correlated during events with maximum concentrations in excess of 30 mg L 1 at peak flow. Suspended sediment concentrations were markedly elevated in the disturbed stream with maximum concentrations at peak flow some 4–5 times greater than in the control. The colour of the sediment suggested that it was highly organic in nature at peak flow, and suspended particulate organic carbon represented a further loss of C from the site. Using flow-weighted mean DOC concentrations calculated for the storms monitored in autumn 2007, dissolved carbon losses can be estimated for the catchments of the disturbed and control streams. From these data the additional DOC loss related to disturbance associated with the wind farm is estimated at 5 g m-2.

  8. Assessing chromophoric dissolved organic matter (CDOM) distribution, stocks, and fluxes in Apalachicola Bay using combined field, VIIRS ocean color, and model observations

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Ishan D.; D' Sa, Eurico J.; Osburn, Christopher L.; Bianchi, Thomas S.; Ko, Dong S.; Oviedo-Vargas, Diana; Arellano, Ana R.; Ward, Nicholas D.

    2017-03-01

    Understanding the role of estuarine-carbon fluxes is essential to improve estimates of the global carbon budget. Dissolved organic matter (DOM) plays an important role in aquatic carbon cycling. The chromophoric fraction of DOM (CDOM) can be readily detected via in situ and remotely-sensed optical measurements. DOM properties, including CDOM absorption coefficient at 412 nm (ag412) and dissolved organic carbon (DOC) concentrations were examined in Apalachicola Bay, a national estuarine research reserve located in the northeast Gulf of Mexico, using in situ and satellite observations during the spring and fall of 2015. Synoptic and accurate representation of estuarine-scale processes using satellite ocean color imagery necessitates the removal of atmospheric contribu- tion (~90%) to signals received by satellite sensors to successfully link to in situ observations. Three atmospheric correction schemes (e.g., Standard NIR correction, Iterative NIR correction, and SWIR correction) were tested first to find a suitable correction scheme for the VIIRS imagery in low to moderately turbid Apalachicola Bay. The iterative NIR correction performed well, and validation showed high correlation (R2 = 0.95, N = 25) against in situ light measurements. A VIIRS-based CDOM algorithm was developed (R2 = 0.87, N = 9) and validated (R2 = 0.76, N = 20, RMSE = 0.29 m-1) against in situ observations. Subsequently, ag412 was used as a proxy ofDOCinMarch(DOC=1.08+0.94×ag412,R2 =0.88,N=13)andinNovember(DOC= 1.61 + 1.33 × ag412, R2 = 0.83, N = 24) to derive DOC maps that provided synoptic views of DOC distribution, sources, and their transport to the coastal waters during the wet and dry seasons. The estimated DOC stocks were ~3.71 × 106 kg C in March and ~4.07 × 106 kg C in November over an area of ~560 km2. Volume flux (out of the bay) almost doubled for March 24 (735 m3

  9. Export fluxes in a naturally fertilized area of the Southern Ocean, the Kerguelen Plateau: ecological vectors of carbon and biogenic silica to depth (Part 2

    Directory of Open Access Journals (Sweden)

    M. Rembauville

    2014-12-01

    Full Text Available The chemical (particulate organic carbon and nitrogen, biogenic silica and biological (diatoms and faecal pellets composition of the material exported to a moored sediment trap located under the winter mixed layer of the naturally-fertilized Kerguelen Plateau in the Southern Ocean was studied over an annual cycle. Despite iron availability in spring, the annual particulate organic carbon (POC export (98.2 mmol m−2 at 289 m was low but annual biogenic silica export was significant (114 mmol m−2. This feature was related to the abundance of empty diatom frustules and the ratio of full : empty cell exerted a first order control in BSi : POC export stoichiometry of biological pump. Chaetoceros Hyalochaete spp. and Thalassiosira antarctica resting spores were found to be responsible for more than 60% of the annual POC that occurred during two very short export events (80%. The seasonal progression of faecal pellet types revealed a clear transition from small spherical shapes (small copepods in spring, larger cylindrical and ellipsoid shapes in summer (euphausiids and large copepods and finally large tabular shapes (salps in autumn and winter. We propose that in this High Biomass, Low Export (HBLE environment, small, highly silicified, fast-sinking resting spores are able to bypass the high grazing pressure and efficient carbon transfer to higher trophic levels that are responsible for the low fluxes observed the during the remainder of the year. Our study also provides a statistical framework linking the ecological succession of diatom and zooplankton communities to the seasonality of carbon and silicon export within an iron-fertilized bloom region in the Southern Ocean.

  10. High Frequency Monitoring of the Quantity and Quality of Dissolved Organic Matter Flux Between Salt Marshes and Plum Island Sound, MA

    Science.gov (United States)

    Zhao, Y.; Raymond, P.

    2012-12-01

    Salt marshes are highly productive continental margin ecosystems, due to abundant solar radiation, water, and nutrients provided by tidal water. The unique bi-directional water movement introduced by tidal effect has a major impact on the formation and productivity of salt marsh and the material exchange between salt marsh and adjacent estuary. As a major term in carbon, energy, and nutrient budget for aquatic ecosystem, dissolved organic matter (DOM) has broad impact on food webs, carbon cycle, and nutrient retention/release. The frequency and period of DOM measurement is greatly increased by the use of reagent-free, low-cost, and reliable measurement with fluorescent and UV sensors measuring the chromophoric fraction of total DOM. Although fluorescent sensors can only measure concentration, UV absorbance in a wide spectral range (200nm-380nm) could potentially provide information on DOM composition. With the help of accurate direct real time water flux measurement and lab analysis of lability, DON, and 3D excitation emission matrix spectroscopy (EEMs), a database of DOM quantity and quality exchanged between several comparative salt marshes and Plum Island Sound, MA could be established to study the dynamics of DOM behavior in the salt marsh-estuary system. Understanding DOM source and fate is very important for evaluating the role of salt marsh in the carbon cycle and food web in coastal and global scale because coastal carbon cycling represents up to 21% of the ocean's primary production (Jahnke 2008). In addition, the approaches outlined in this proposal have broad applicability to study DOM quantity and quality in the material exchange theme between systems.

  11. How Population Growth and Land-Use Change Increased Fluvial Dissolved Organic Carbon Fluxes over 130 Years in the Thames Basin (UK)

    Science.gov (United States)

    Noacco, V.; Howden, N. J. K.; Wagener, T.; Worrall, F.; Burt, T. P.

    2015-12-01

    This study investigates drivers of changing dissolved organic carbon (DOC) export in the UK's River Thames basin between 1884 and 2014. Specifically, we consider how the impacts of land-use change and population growth drive increases in DOC concentrations and fluxes at the basin outlet. Such key factors for the long-term increase in riverine DOC in temperate, mineral-soil catchments are still widely debated. First, we estimate soil organic carbon (SOC) stocks in the Thames basin for the period. Second, we convert SOC losses due to land-use change into DOC loss to surface waters through runoff. Finally, we combine this input of DOC with an export coefficient model that considers catchment drivers for DOC release to the river. SOC stocks for each year are calculated from a large database of typical SOC levels for land-uses present in the Thames basin and are combined with literature values of transition times for SOC to adjust to a new level following land-use change. We also account for climate change effects on SOC stock due to temperature increases, which reduces SOC stocks as soil organic matter turnover rates increase. Our work shows that the major driver for DOC increase to the river Thames was the rise in the catchment population, where the increase in urban area was used as a proxy. This highlights the role of sewage effluent in contributing to the rise of fluvial DOC, even though wastewater treatments were in place since the early 1990s. Land-use change had significant but short-term impacts in the increase in DOC, mainly due to massive conversion of permanent grassland into arable land during World War II.

  12. Coupling simultaneous dissolved nitrate measurements with quantum cascade laser based nitrous oxide flux and isotopocule analysis to investigate the biogeochemical processes occurring in a denitrifying bioreactor.

    Science.gov (United States)

    Williams, D. J.; Maxwell, B.; Deshmukh, P.; Chen, H.

    2016-12-01

    Denitrifying bioreactors are used to treat nitrogen enriched water from agricultural operations. These systems may also be an important source of nitrous oxide emissions, a potent greenhouse gas. Bioreactors also provide researchers with an opportunity to investigate the biogeochemical processes occurring in soils under controlled conditions. A pilot-scale bioreactor with woodchip media was injected with KNO3 at a constant flow rate through the system. The water-filled-pore-space (WFPS) was varied in separate experiments to create differing aerobic conditions. A quantum cascade laser spectroscopy system was used to determine the flux and isotopic signature of N2O emissions from woodchip bioreactor media over time. Simultaneous nitrate concentration measurements were made using an optical method at multiple points in the bioreactor. Isotopic site-preference (SP) characterization of N2O emissions was used to estimate production sources from soil nitrification and denitrification. A dynamic gas sampling method was used to measure N2O mixing ratios, which required ambient air to equalize chamber atmospheric pressure during sampling. Precise instrument calibration using gas samples of known isotopic abundances, provided by the Swiss Federal Labs (EMPA), together with a Keeling plot method to account for variations in isotopocule composition in ambient air, produced reliable SP estimates. Initial experiments during 100% WFPS show that SP and δ15Nbulk values were varied from -6‰ to 3‰ and -23‰ to -12‰, respectively. The trend of these values indicated that the N2O source was slightly changed from partial nitrification to denitrification during the measuring period of time. The peak rate of nitrous oxide production occurred 7 hours after peak nitrate removal. These results and others to be presented show the utility of coupling real-time dissolved and gas phase measurements for studying nitrogen cycling in soils.

  13. Impact of atmospheric pollution inputs and climate change on dissolved inorganic carbon fluxes in karst aquifers: evidences from a 36 years past monitoring of karstic watersheds.

    Science.gov (United States)

    Binet, Stephane; Probst, Jean-Luc; Batiot-Guilhe, Christelle; Seidel, Jean-Luc; Emblanch, Christophe; Peyraube, Nicolas; Mangin, Alain; Bakalowicz, Michel; Probst, Anne

    2017-04-01

    Atmospheric pollution is known to modify the soil CO2 consumption associated with carbonate bedrock weathering. To evidence the long term feedbacks of atmospheric pollution and climate change on this chemical reaction, we investigated the inorganic carbon fluxes monitored weekly from 1979 to 2006 in a small forested karstic watershed in the Pyrénées Mountains, characterized by a large precipitation variability, a 0.025 °C air temperature increase per year and a low agricultural pressure. The yearly average concentrations of [Ca + Mg] and dissolved inorganic carbon increases of about 0.057 meq.L-1.yr-1 and the 0.1 meq.L-1.yr-1, respectively. The gap relative to the 1:2 relationship between [Ca + Mg] and HCO3 (in mmole. L-1), noted Delta-HCO3, was founded to be driven by the atmospheric pollution inputs, producing strong acids that inhibit the consumption of carbon from soil during the carbonate dissolution processes. In addition, atmospheric temperature increase is correlated with the [Ca +Mg] change, whereas the decrease of the atmospheric acid inputs observed since the seventies, is linked with a + 0.0022 meq.L-1.yr-1 increase in Delta-HCO3. Similar trends in Delta-HCO3 change were found over other karstic watersheds monitored more recently in the framework of the SNO KARST, one the observatory networks from the OZCAR Research Infrastructure, highlighting that Delta-HCO3 changes over time were partially controlled by atmospheric pollution inputs. The re-interpretation of hydrochemical databases using this Delta-HCO3 indicator enables to evaluate better the impact of atmospheric pollution load and climate change on surface waters. In an indirect way, the dephasing between atmospheric loads recorded in precipitation and Delta-HCO3 observed in groundwater could be a new tracer method to estimate groundwater residence times.

  14. The impact of damming on riverine fluxes to the ocean: A case study from Eastern Iceland.

    Science.gov (United States)

    Eiriksdottir, Eydis Salome; Oelkers, Eric H; Hardardottir, Jorunn; Gislason, Sigurdur Reynir

    2017-04-15

    Anthropogenic water management has extensively altered the world's river systems through impoundments and channel diversions to meet the human's need for water, energy and transportation. To illuminate the effect of such activities on the environment, this study describes the impact of the installation of the Kárahnjúkar Dam in Eastern Iceland on the transport of riverine dissolved- and particulate material to the ocean by the Jökulsá á Dal and the Lagarfljót rivers. This dam, completed in 2007, collects water into the 2.2 km(3) Hálslón reservoir and diverts water from the glacial Jökulsá á Dal river into the partially glaciated Lagarfljót lagoon via a headrace tunnel. The impact of the damming was evaluated by sampling water from both the Jökulsá á Dal and the Lagarfljót rivers over a 15 year period spanning from 1998 to 2013. The annual flux of most dissolved elements increased substantially due to the damming. The fluxes of dissolved Zn, Al, Co, Ti and Fe increased most by damming; these fluxes increased by 46-391%. These differences can be attributed to changed saturation states of common secondary minerals in the Jökulsá á Dal due to reduced discharge, increased residence time and dissolution of suspended material, and, to a lesser degree, reduced photosynthesis due to less transparency in the Lagarfljót lagoon. The removal of particulate material and thus decreasing adsorption potential in the Jökulsá á Dal is the likely reason for the Fe flux increase. In contrast, approximately 85% of the original riverine transported mass of particulate material is trapped by the dam; that which passes tends to be relatively fine grained, increasing the average specific surface area of that which continues to flow towards the ocean. Consequently, the particulate geometric surface area flux is decreased by only 50% due to the damming. The blooming of silica diatoms during the spring consumes dissolved silica from the coastal waters until it becomes

  15. The silica cycle in a Northeast Pacific fjord; the role of biological resuspension

    Science.gov (United States)

    Katz, Timor; Yahel, Gitai; Tunnicliffe, Verena; Herut, Barak; Whitney, Frank; Snelgrove, Paul V. R.; Lazar, Boaz

    2016-09-01

    This study is a quantitative assessment of the role fish-induced bio-resuspension plays in the silica cycle of coastal waters. We used new, published and archived oceanographic data to construct a comprehensive silica budget for Saanich Inlet (Vancouver Island, Canada), a highly productive Northeast Pacific fjord, where siliceous diatoms dominate primary productivity. Anoxia in the deep water of the inlet persists during most of the year, precluding animal life, whereas abundant groundfish continuously rework and resuspend bottom sediments in the shallower, oxygenated margins. This resuspension transfers settled biogenic silica fragments from the sediment, where they are immersed in porewater that is rich with dissolved silica, to the overlying water, where the much lower concentrations accelerate their dissolution rate. The budget shows that Saanich Inlet sediments constitute a sink for approximately 250 × 106 mol Si y-1. Most of this Si enters the inlet in advected, siliceous phytoplankton. Sediment resuspension by groundfish in the oxygenated margins of Saanich Inlet generates about 50% of the total flux of dissolved silica from the inlet seafloor. This resuspension also facilitates a massive transport of biogenic silica from the margins to the anoxic basin, where approximately 90% of all the biogenic silica is buried. The excess dissolution caused by fish activity reduces the burial efficiency of biogenic silica in the entire inlet sediments by about 20%. This case study emphasizes the link between the silica cycle and groundfish activity. Based on this study and because biological resuspension occurs in most regions of the ocean, we recommend that it will be taken into account when budgeting the silica cycle, and potentially other geochemical cycles, in marine environments.

  16. Mesoporous fluorocarbon-modified silica aerogel membranes enabling long-term continuous CO2 capture with large absorption flux enhancements.

    Science.gov (United States)

    Lin, Yi-Feng; Chen, Chien-Hua; Tung, Kuo-Lun; Wei, Te-Yu; Lu, Shih-Yuan; Chang, Kai-Shiun

    2013-03-01

    The use of a membrane contactor combined with a hydrophobic porous membrane and an amine absorbent has attracted considerable attention for the capture of CO2 because of its extensive use, low operational costs, and low energy consumption. The hydrophobic porous membrane interface prevents the passage of the amine absorbent but allows the penetration of CO2 molecules that are captured by the amine absorbent. Herein, highly porous SiO2 aerogels modified with hydrophobic fluorocarbon functional groups (CF3 ) were successfully coated onto a macroporous Al2 O3 membrane; their performance in a membrane contactor for CO2 absorption is discussed. The SiO2 aerogel membrane modified with CF3 functional groups exhibits the highest CO2 absorption flux and can be continuously operated for CO2 absorption for extended periods of time. This study suggests that a SiO2 aerogel membrane modified with CF3 functional groups could potentially be used in a membrane contactor for CO2 absorption. Also, the resulting hydrophobic SiO2 aerogel membrane contactor is a promising technology for large-scale CO2 absorption during the post-combustion process in power plants.

  17. Concentration, flux, and the analysis of trends of total and dissolved phosphorus, total nitrogen, and chloride in 18 tributaries to Lake Champlain, Vermont and New York, 1990–2011

    Science.gov (United States)

    Medalie, Laura

    2013-01-01

    Annual concentration, flux, and yield for total phosphorus, dissolved phosphorus, total nitrogen, and chloride for 18 tributaries to Lake Champlain were estimated for 1990 through 2011 using a weighted regression method based on time, tributary streamflows (discharges), and seasonal factors. The weighted regression method generated two series of daily estimates of flux and concentration during the period of record: one based on observed discharges and a second based on a flow-normalization procedure that removes random variation due to year-to-year climate-driven effects. The flownormalized estimate for a given date is similar to an average estimate of concentration or flux that would be made if all of the observed discharges for that date were equally likely to have occurred. The flux bias statistic showed that 68 of the 72 flux regression models were minimally biased. Temporal trends in the concentrations and fluxes were determined by calculating percent changes in flow-normalized annual fluxes for the full period of analysis (1990 through 2010) and for the decades 1990–2000 and 2000–2010. Basinwide, flow-normalized total phosphorus flux decreased by 42 metric tons per year (t/yr) between 1990 and 2010. This net result reflects a basinwide decrease in flux of 21 metric tons (t) between 1990 and 2000, followed by a decrease of 20 t between 2000 and 2010; both results were largely influenced by flux patterns in the large tributaries on the eastern side of the basin. A comparison of results for total phosphorus for the two separate decades of analysis found that more tributaries had decreasing concentrations and flux rates in the second decade than the first. An overall reduction in dissolved phosphorus flux of 0.7 t/yr was seen in the Lake Champlain Basin during the full period of analysis. That very small net change in flux reflects substantial reductions between 1990 and 2000 from eastern tributaries, especially in Otter Creek and the LaPlatte and Winooski

  18. Kinetics of silica polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Weres, O.; Yee, A.; Tsao, L.

    1980-05-01

    The polymerization of silicic acid in geothermal brine-like aqueous solutions to produce amorphous silica in colloidal form has been studied experimentally and theoretically. A large amount of high quality experimental data has been generated over the temperature rang 23 to 100{sup 0}C. Wide ranges of dissolved silica concentration, pH, and sodium chloride concentration were covered. The catalytic effects of fluoride and the reaction inhibiting effects of aluminum and boron were studied also. Two basic processes have been separately studied: the formation of new colloidal particles by the homogeneous nucleation process and the deposition of dissolved silica on pre-existing colloidal particles. A rigorous theory of the formation of colloidal particles of amorphous silica by homogeneous nucleation was developed. This theory employs the Lothe-Pound formalism, and is embodied in the computer code SILNUC which quantitatively models the homogeneous nucleation and growth of colloidal silica particles in more than enough detail for practical application. The theory and code were extensively used in planning the experimental work and analyzing the data produced. The code is now complete and running in its final form. It is capable of reproducing most of the experimental results to within experimental error. It is also capable of extrapolation to experimentally inaccessible conditions, i.e., high temperatures, rapidly varying temperature and pH, etc.

  19. Impact of catastrophic events on small mountainous rivers: Temporal and spatial variations in suspended- and dissolved-solid fluxes along the Choshui River, central western Taiwan, during typhoon Mindulle, July 2-6, 2004

    Science.gov (United States)

    Milliman, J. D.; Lee, T. Y.; Huang, J. C.; Kao, S. J.

    2017-05-01

    Small mountainous rivers deliver disproportionately large quantities of suspended and dissolved solids to the global ocean, often in response to catastrophic events such as earthquakes or floods. Here we report on the impact of a major flood on the Choshui River, central-western Taiwan, generated by typhoon Mindulle, July 2-6, 2004, five years after the nearby Mw 7.6 Chichi earthquake. Water samples taken at 3-h intervals at three stations along main stem, as well as from two downriver tributaries, allow us to delineate the temporal and spatial variability in concentrations and fluxes of suspended and dissolved constituents within the middle and lower portions of the river in response to this flood. High suspended-sediment concentrations, some as high as 200 g/l, reflected the rapid erosion of landslide scars and debris deposits generated by super-typhoon Herb in 1996 and the 1999 Chichi earthquake. Dissolved-solid and suspended-sediment discharges totaled 0.22 and 70 million tons (mt), 50 mt of which were discharged in just two days. Particulate organic carbon (POC) discharge, most of which was pre-modern in age, was 195,000 t. More than half of the discharged water, POC and dissolved solids came from upriver, whereas about 70% of the suspended sediment and 60% of the dissolved nitrate came from two downriver tributaries, the Chenyoulan and Qingshui rivers. Spatial and temporal differences in the character and discharge of suspended and dissolved solids within and between rivers in the Choshui drainage basin reflect different geologies, landslide histories, the effects of human impact, and the abrupt draining of the Tsaoling landslide lake in the Qingshui basin, as well as the possible shifting of importance of groundwater vs. overland flow. Neither wind-blown pollutants nor sea salts appear to have contributed significantly to dissolved solid character or discharge. Sediment contribution from the landslides in the Chenyoulan basin generated by super-typhoon Herb

  20. Throughfall and bulk deposition of dissolved organic nitrogen to holm oak forests in the Iberian Peninsula : flux estimation and identification of potential sources

    OpenAIRE

    Izquieta-Rojano, Sheila; García-Gomez, H.; Aguillaume Rodríguez-O'connor, Laura; Santamaría Ulecia, Jesús Miguel; Y. S. Tang; Santamaría, C.; Valiño, F.; Lasheras, E. (Esther); Alonso, R.; Àvila i Castells, Anna; Cape, J. N.; Elustondo, David

    2016-01-01

    Acknowledgments: the research leading to these results has received funding from the COST organism (European cooperation in science and technology), through the COST Action FP0903 “Climate change and forest mitigation and adaptation in the polluted environment” under the grant number COST-STSM-ECOST-STSM-FP0903-291012-019757. Deposition of dissolved organic nitrogen (DON) in both bulk precipitation (BD) and canopy throughfall (TF) has been measured for the first time in the western Mediter...

  1. Dissolved oxygen

    National Research Council Canada - National Science Library

    1981-01-01

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

  2. Study of silica coatings degradation under laser irradiation and in controlled environment; Etude de la degradation de couches minces de silice sous flux laser et en environnement controle

    Energy Technology Data Exchange (ETDEWEB)

    Becker, S

    2006-11-15

    Performances of optical components submitted to high laser intensities are usually determined by their laser-induced damage threshold. This value represents the highest density of energy (fluence) sustainable by the component before its damage. When submitted to laser fluences far below this threshold, optical performances may also decrease with time. The degradation processes depend on laser characteristics, optical materials, and environment around the component. Silica being the most used material in optics, the aim of this study was to describe and analyse the physical-chemical mechanisms responsible for laser-induced degradation of silica coatings in controlled environment. Experimental results show that degradation is due to the growth of a carbon deposit in the irradiated zone. From these results, a phenomenological model has been proposed and validated with numerical simulations. Then, several technological solutions have been tested in order to reduce the laser-induced contamination of silica coatings. (author)

  3. Application of in situ observations, high frequency radars, and ocean color, to study suspended matter, particulate carbon, and dissolved organic carbon fluxes in coastal waters of the Barents Sea - the NORDFLUX project

    Science.gov (United States)

    Stramska, Malgorzata; Yngve Børsheim, Knut; Białogrodzka, Jagoda; Cieszyńska, Agata; Ficek, Dariusz; Wereszka, Marzena

    2016-04-01

    There is still a limited knowledge about suspended and dissolved matter fluxes transported from coastal regions into the open sea regions in the Arctic. The land/sea interface is environmentally important and sensitive to climate change. Important biogeochemical material entering the oceans (including carbon) passes through this interface, but too little is known about the efficiency of this transport. Our goal in the NORDFLUX program is to improve quantitative understanding of the environmental feedbacks involved in these processes through an interdisciplinary study with innovative in situ observations. Completed work includes two in situ experiments in the Norwegian fiord (Porsangerfjorden) in the summers of 2014 and 2015. Experiments used research boat for collection of water samples and in situ bio-optical data, an autonomous glider, mooring with T S sensors, and a high frequency radar system. We have used these data to derive spatial maps of water temperature, salinity, surface currents, chlorophyll fluorescence, dissolved organic matter (DOM) fluorescence, and inherent optical properties (IOPs) of the water. The interpretation of these data in terms of suspended matter concentration and composition is possible by in situ 'calibrations' using water samples from discrete hydrographic stations. Total suspended matter (TSM), particulate carbon (POC and PIC), and dissolved organic carbon (DOC) concentrations together with measured water currents will allow us to estimate reservoirs and fluxes. Concentrations and fluxes will be related to physical conditions and meteorological data. An important aspect of this project is the work on regional ocean color algorithms. Global ocean color (OC) algorithms currently used by NASA do not perform sufficiently well in coastal Case 2 waters. Our data sets will allow us to derive such local algorithms. We will then use these algorithms for interpretation of OC data in terms of TSM concentrations and composition and DOC. After

  4. Contribution des surfaces saturées et des versants aux flux d'eau et d'éléments exportés en période de crue: traçage à l'aide du carbone organique dissous et de la silice. Cas du petit bassin versant du Strengbach (Vosges, France)

    Science.gov (United States)

    Idir, Samir; Probst, Anne; Viville, Daniel; Probst, Jean-Luc

    1999-01-01

    Two contributing areas have been determined in the small forested Strengbach catchment by using dissolved organic carbon (DOC) and dissolved silica as the most efficient chemical tracers of stream water origin during a storm event. Dissolved silica represents the deep layers of the hillslopes which contributes 71-75 % of the total storm runoff and 85-99 % of the fluxes of major elements exported by the Strengbach. DOC corresponds to the saturated areas which occupy only 2 % of the total catchment area but which supply 25-29 % of the total streamflow and 56 % of the DOC stream flux. The specific fluxes of water (L·s -1·ha -1) and elements (kg·ha -1) are much more important in the saturared areas than in the rest of the catchment.

  5. Eutrophication in the northern Adriatic Sea: Benthic fluxes and nutrient budgets

    Energy Technology Data Exchange (ETDEWEB)

    Berelson, W.M.; Hammond, D.E. (Univ. of Southern California, Los Angeles (United States)); Giordani, P. (Inst. di Geologia Marina-CNR, Bologna (Italy))

    1990-01-09

    The northern Adriatic Sea has been plagued by problems of eutrophication. This area is relatively shallow (maximum depth = 60m), becoming stratified during the summer months which inhibits oxygen transport to bottom waters. Anthropogenic nutrient loading in rivers entering the northern Adriatic has increased nutrient input to this system and stimulated algai growth. Five stations in the western Adriatic (south of the Po River Delta) were occupied during September, 1988 and benthic flux chambers used to measure nutrient fluxes. These sites included 3 stations previously studied in 1982. Flux measurements of dissolved silica, nitrate, oxygen, ammonia, phosphate, CO[sub 2], alkalinity and radon were made during 24 hour incubations of flux chambers (area covered - 0.07 m[sup 2], volume = [approximately]81) that were continuously stirred and sampled periodically. Nutrient fluxes measured were generally consistent with the fluxes measured previously in June, 1982 except for radon fluxes which were 203 times greater in the earlier field season. There was a general trend in nutrient fluxes to decrease offshore, a pattern probably controlled by the sedimentation patterns because fine grained, organic matter-rich sediment are concentrated in a zone near shore. Average regional fluxes were (in mmol m[sup -2]d[sup -1], negative values indicate flux into sediment): Oxygen (-12), CO[sub 2] (19), Alkalinity (4), Silica (3.3), Ammonia (1.5), Phosphate (0.1) and Nitrate (0.3). The carbon/ammonia flux ratio is about twice the C/N ratio in marine phytoplankton, suggesting that large amounts of denitrification may be occuring in these sediments. Comparisons of benthic fluxes and sediment burial rates indicate that 50-90% of the carbon, silica, phosphorus and nitrogen arriving at the sediment-water interface is recycled before burial. The nutrient input to the water column from NW Adriatic sediments is about equal to the input from coastal rivers.

  6. 溶氧对Candida glycerinogenes产甘油发酵代谢流分布的影响%Effect of dissolved oxygen on metabolic flux distribution during glycerol fermentation by Candida glycerinogenes

    Institute of Scientific and Technical Information of China (English)

    焦策; 诸葛斌; 方慧英; 诸葛健

    2012-01-01

    The glycerol production by fermentation in flasks by Candida glycerinogenes was studied. Dissolved oxygen (DO) was one of the most important factors in the cultivation of the strain by influencing cell growth and metabolites generated. Based on this result, batch fermentation of glycerol under diverse DO levels in a 5 L stirred fermentor was investigated. The metabolic flux analysis explained the phenomenon that sugar consumption was fast and glycerol synthesis was relatively less under low dissolved oxygen levels, mainly due to generated ethanol. Metabolic flux analysis also showed that HMP pathway played an important role in glycerol synthesis. Analysis of carbon metabolization and energy metabolization (oxidative phosphorylation and substrate level phosphorylation) of C. Glycerinogenes in the process of glycerol fermentation showed that a high level of ATP synthesis at high dissolved oxygen levels to a certain degree inhibited substrate level phosphorylation so that more carbon flowed to glycerol synthesis. The intracellular redox balance (NADH/NAD+ ratio) reflected the competition between glycerolproduction and ethanol synthesis.%分析了耐高渗高产甘油工业菌株产甘油假丝酵母(Candida glycerinogenes)的摇瓶发酵过程,发现溶氧水平是影响C.glycerinogenes生长、代谢产物生成的重要因素.在此基础上,以5L发酵罐研究了不同恒溶氧水平甘油的合成过程,通过代谢流分析表明,低溶氧环境下乙醇碳流量增加,导致糖耗快而甘油合成相对较少;碳流分布表明HMP途径在甘油过量合成中起着重要的作用.分析C.glycerinogenes发酵过程中能量代谢和物质代谢(氧化磷酸化和底物水平磷酸化)的变化发现高溶氧环境下ATP合成水平高,一定程度抑制底物水平磷酸化从而使碳流更多地流向了甘油合成;C.glycerinogenes胞内氧化还原平衡(NADH/NAD+比率)的研究进一步解释了产甘油假丝酵母中甘油合成和乙醇生成的竞争关系.

  7. Global spatial distribution of natural riverine silica inputs to the coastal zone

    Directory of Open Access Journals (Sweden)

    H. H. Dürr

    2011-03-01

    Full Text Available Silica, SiO2, in dissolved (DSi and particulate (PSi form, is both a major product of continental weathering as well as an essential nutrient in terrestrial and aquatic systems. Here we present estimates of the spatial distribution of riverine silica fluxes under natural conditions, i.e. without human influence, to ~140 segments of the global coastal zone. Focussing on the construction of the DSi budget, natural DSi concentration is multiplied with discharge of rivers for each segment for documented basins and segments. Segments with no documentation available are estimated using clustered information based mainly on considerations of local lithology, climate, and lake retention. We approximate fluxes of particulate silica in various forms (PSi from fluxes of suspended matter, calculated from existing models. Results have been established for silica fluxes, concentrations and yields for drainage basins of the different continents, oceans basins as well as coastal segment basins. For the continental surfaces actually draining into the oceans (exorheic regions, representing 114.7 million (M km2, 371 M t y−1 of DSi and 8835 M t y−1 of PSi are transported, corresponding to a mean concentration of 9.5 mg l−1 and 226 mg l−1, and to a mean yield of 3.3 t km−2 y−1 and 77 t km−2 y−1, respectively. DSi yields exceeding 6.6 t km−2 y−1, i.e. >2× the global average, represent 17.4% of the global continental ice-free exorheic area but correspond to 56.0% of DSi fluxes. Pacific catchments hold most of the hyper-active areas (>5× global average, suggesting a close connection between tectonic activity and DSi fluxes resulting from silicate weathering. The macro-filters of regional and marginal seas intercept 33% and 46% of the total dissolved and particulate silica fluxes. The mass of DSi received from rivers

  8. [Compared with colloidal silica and porous silica as baicalin solid dispersion carrier].

    Science.gov (United States)

    Yan, Hong-Mei; Ding, Dong-Mei; Wang, Jing; Sun, E; Jia, Xiao-Bin; Zhang, Zhen-Hai

    2014-07-01

    To compare the dissolution characteristics of colloidal silica and porous silica as the solid dispersion carrier, with baicalin as the model drug. The baicalin solid dispersion was prepared by the solvent method, with colloidal silica and porous silica as the carriers. In the in vitro dissolution experiment, the solid dispersion was identified by scanning electron microscopy, differential scanning and X-ray diffraction. The solid dispersion carriers prepared with both colloidal silica and porous silica could achieve the purpose of rapid release. Along with the increase in the proportion of the carriers, the dissolution rate is accelerated to more than 80% within 60 min. Baicalin existed in the solid dispersion carriers in the non-crystalline form. The release behaviors of the baicalin solid dispersion prepared with two types of carrier were different. Among the two solid dispersion carriers, porous silica dissolved slowly than colloidal silica within 60 min, and they showed similar dissolutions after 60 min.

  9. A Thin Film Nanocomposite Membrane with MCM-41 Silica Nanoparticles for Brackish Water Purification

    Directory of Open Access Journals (Sweden)

    Mohammed Kadhom

    2016-12-01

    Full Text Available Thin film nanocomposite (TFN membranes containing MCM-41 silica nanoparticles (NPs were synthesized by the interfacial polymerization (IP process. An m-phenylenediamine (MPD aqueous solution and an organic phase with trimesoyl chloride (TMC dissolved in isooctane were used in the IP reaction, occurring on a nanoporous polysulfone (PSU support layer. Isooctane was introduced as the organic solvent for TMC in this work due to its intermediate boiling point. MCM-41 silica NPs were loaded in MPD and TMC solutions in separate experiments, in a concentration range from 0 to 0.04 wt %, and the membrane performance was assessed and compared based on salt rejection and water flux. The prepared membranes were characterized via scanning electron microscopy (SEM, transmission electron microscopy (TEM, contact angle measurement, and attenuated total reflection Fourier transform infrared (ATR FT-IR analysis. The results show that adding MCM-41 silica NPs into an MPD solution yields slightly improved and more stable results than adding them to a TMC solution. With 0.02% MCM-41 silica NPs in the MPD solution, the water flux was increased from 44.0 to 64.1 L/m2·h, while the rejection virtually remained the same at 95% (2000 ppm NaCl saline solution, 25 °C, 2068 kPa (300 psi.

  10. Fluxes and 13C isotopic composition of dissolved carbon and pathways of methanogenesis in a fen soil exposed to experimental drought

    Directory of Open Access Journals (Sweden)

    C. Blodau

    2008-10-01

    Full Text Available Peatlands contain a carbon stock of global concern and significantly contribute to the global methane burden. The impact of drought and rewetting on carbon cycling in peatland ecosystems is thus currently debated. We studied the impact of experimental drought and rewetting on intact monoliths from a temperate fen over a period of ~300 days, using a permanently wet treatment and two treatments undergoing drought for 50 days. In one of the mesocosms, vegetation had been removed. Net production of CH4 was calculated from mass balances in the peat and emission using static chamber measurements. Results were compared to 13C isotope budgets of CO2 and CH4 and energy yields of acetoclastic and hydrogenotrophic methanogenesis. Drought retarded methane production after rewetting for days to weeks and promoted methanotrophic activity. Based on isotope and flux budgets, aerobic soil respiration contributed 32–96% in the wet treatment and 86–99% in the other treatments. Drying and rewetting did not shift methanogenic pathways according to δ13C ratios of CH4 and CO2. Although δ13C ratios indicated a prevalence of hydrogenotrophic methanogenesis, free energies of this process were small and often positive on the horizon scale. This suggests that methane was produced very locally. Fresh plant-derived carbon input apparently supported respiration in the rhizosphere and sustained methanogenesis in the unsaturated zone, according to a 13C-CO2 labelling experiment. The study documents that drying and rewetting in a rich fen soil may have little effect on methanogenic pathways, but result in rapid shifts between methanogenesis and methanotrophy. Such shifts may be promoted by roots and soil heterogeneity, as hydrogenotrophic methanogenesis occurred locally even when conditions were not conducive for this process in the bulk peat.

  11. 基于代谢通量分析的SAM和GSH联产溶氧控制策略%The Dissolved Oxygen Control Strategy Based on Metabolic Flux Analysis for Fermentative Co-Production of S-Adenosylmethionine and Glutathione

    Institute of Scientific and Technical Information of China (English)

    王大慧; 王玉磊; 卫功元; 邵娜; 周捷

    2013-01-01

    In order to improve the co-production of SAM and GSH under batch cultivation, the effect of dissolved oxygen (DO) level on fermentative co-production of S-adenosylmethionine (SAM) and glutathione (GSH) in a 5 L stirred fermentor with Candida utilis CCTCC M 209298 was investigated. The metabolic fluxes of intermediates and energy during batch fermentative co-production of SAM and GSH under different agitation rates were calculated by using metabolic flux analysis method. Based on the flux distribution of main intermediates, an optimum DO control strategy of a constant agitation rate of 350 r⋅min−1 maintained during the first 9 h of fermentation followed with a DO level not less than 30% after 9 h was proposed as an efficient approach for high co-production of SAM and GSH. Under this DO control mode, the product of 520.7 mg⋅L−1 for batch co-production of SAM and GSH with C.utilis CCTCC M 209298 was achieved. Furthermore, the reason for the improvement of the co-production of SAM and GSH under the proposed strategy was quantitatively interpreted by the fermentative kinetics, metabolic flux analysis and respiratory quotient, respectively.%  为了提高S-腺苷甲硫氨酸(SAM)和谷胱甘肽(GSH)的联产量,考察了溶氧条件对Candida utilis CCTCC M 209298发酵联产SAM和GSH的影响.采用代谢通量分析方法对不同转速下SAM和GSH联产发酵过程中的物质和能量代谢进行分析,确定了较优的溶氧控制策略:前9 h的发酵恒定转速350 r⋅min−1,9 h后控制溶氧不低于30%.在此策略下,C. utilis CCTCC M 209298分批发酵生产SAM和GSH的联产量为520.7 mg⋅L−1.最后分别从发酵动力学、代谢通量分析以及呼吸商变化规律对该溶氧控制策略促进SAM和GSH联合高产的原因进行了定量解释.

  12. Silica Nephropathy

    Directory of Open Access Journals (Sweden)

    N Ghahramani

    2010-06-01

    Full Text Available Occupational exposure to heavy metals, organic solvents and silica is associated with a variety of renal manifestations. Improved understanding of occupational renal disease provides insight into environmental renal disease, improving knowledge of disease pathogenesis. Silica (SiO2 is an abundant mineral found in sand, rock, and soil. Workers exposed to silica include sandblasters, miners, quarry workers, masons, ceramic workers and glass manufacturers. New cases of silicosis per year have been estimated in the US to be 3600–7300. Exposure to silica has been associated with tubulointerstitial disease, immune-mediated multisystem disease, chronic kidney disease and end-stage renal disease. A rare syndrome of painful, nodular skin lesions has been described in dialysis patients with excessive levels of silicon. Balkan endemic nephropathy is postulated to be due to chronic intoxication with drinking water polluted by silicates released during soil erosion. The mechanism of silica nephrotoxicity is thought to be through direct nephrotoxicity, as well as silica-induced autoimmune diseases such as scleroderma and systemic lupus erythematosus. The renal histopathology varies from focal to crescentic and necrotizing glomerulonephritis with aneurysm formation suggestive of polyarteritis nodosa. The treatment for silica nephrotoxicity is non-specific and depends on the mechanism and stage of the disease. It is quite clear that further research is needed, particularly to elucidate the pathogenesis of silica nephropathy. Considering the importance of diagnosing exposure-related renal disease at early stages, it is imperative to obtain a thorough occupational history in all patients with renal disease, with particular emphasis on exposure to silica, heavy metals, and solvents.

  13. Influence of amorphous silica on the hydration in ultra-high performance concrete

    Energy Technology Data Exchange (ETDEWEB)

    Oertel, Tina, E-mail: tina.oertel@isc.fraunhofer.de [Fraunhofer–Institute for Silicate Research ISC, Neunerplatz 2, 97082 Würzburg (Germany); Inorganic Chemistry I, Universität Bayreuth, Universitätsstr. 30, 95440 Bayreuth (Germany); Helbig, Uta, E-mail: uta.helbig@th-nuernberg.de [Crystallography and X-ray Methods, Technische Hochschule Nürnberg Georg Simon Ohm, Wassertorstraße 10, 90489 Nürnberg (Germany); Hutter, Frank [Fraunhofer–Institute for Silicate Research ISC, Neunerplatz 2, 97082 Würzburg (Germany); Kletti, Holger [Building Materials, Bauhaus–Universität Weimar, Coudraystr. 11, 99423 Weimar (Germany); Sextl, Gerhard [Fraunhofer–Institute for Silicate Research ISC, Neunerplatz 2, 97082 Würzburg (Germany); Chemical Technology of Advanced Materials, Julius Maximilian Universität, Röntgenring 11, 97070 Würzburg (Germany)

    2014-04-01

    Amorphous silica particles (silica) are used in ultra-high performance concretes to densify the microstructure and accelerate the clinker hydration. It is still unclear whether silica predominantly increases the surface for the nucleation of C–S–H phases or dissolves and reacts pozzolanically. Furthermore, varying types of silica may have different and time dependent effects on the clinker hydration. The effects of different silica types were compared in this study by calorimetric analysis, scanning and transmission electron microscopy, in situ X-ray diffraction and compressive strength measurements. The silica component was silica fume, pyrogenic silica or silica synthesized by a wet-chemical route (Stoeber particles). Water-to-cement ratios were 0.23. Differences are observed between the silica for short reaction times (up to 3 days). Results indicate that silica fume and pyrogenic silica accelerate alite hydration by increasing the surface for nucleation of C–S–H phases whereas Stoeber particles show no accelerating effect.

  14. Streamflow and Nutrient Fluxes of the Mississippi-Atchafalaya River Basin and Subbasins for the Period of Record Through 2005

    Science.gov (United States)

    Aulenbach, Brent T.; Buxton, Herbert T.; Battaglin, William A.; Coupe, Richard H.

    2007-01-01

    U.S. Geological Survey has monitored streamflow and water quality systematically in the Mississippi-Atchafalaya River Basin (MARB) for more than five decades. This report provides streamflow and estimates of nutrient delivery (flux) to the Gulf of Mexico from both the Atchafalaya River and the main stem of the Mississippi River. This report provides streamflow and nutrient flux estimates for nine major subbasins of the Mississippi River. This report also provides streamflow and flux estimates for 21 selected subbasins of various sizes, hydrology, land use, and geographic location within the Basin. The information is provided at each station for the period for which sufficient water-quality data are available to make statistically based flux estimates (starting as early as water year1 1960 and going through water year 2005). Nutrient fluxes are estimated using the adjusted maximum likelihood estimate, a type of regression-model method; nutrient fluxes to the Gulf of Mexico also are estimated using the composite method. Regression models were calibrated using a 5-year moving calibration period; the model was used to estimate the last year of the calibration period. Nutrient flux estimates are provided for six water-quality constituents: dissolved nitrite plus nitrate, total organic nitrogen plus ammonia nitrogen (total Kjeldahl nitrogen), dissolved ammonia, total phosphorous, dissolved orthophosphate, and dissolved silica. Additionally, the contribution of streamflow and net nutrient flux for five large subbasins comprising the MARB were determined from streamflow and nutrient fluxes from seven of the aforementioned major subbasins. These five large subbasins are: 1. Lower Mississippi, 2. Upper Mississippi, 3. Ohio/Tennessee, 4. Missouri, and 5. Arkansas/Red.

  15. Benthic Nutrient Fluxes from Mangrove Sediments of an Anthropogenically Impacted Estuary in Southern China

    Directory of Open Access Journals (Sweden)

    David Kaiser

    2015-06-01

    Full Text Available Mangroves serve as either sinks or sources for inorganic and organic nutrients and can mitigate anthropogenic nutrient pollution, control the production in adjacent systems, and prevent eutrophication. To better understand the nutrient dynamics in a subtropical mangrove, we employed a three-way approach in the Nanliu River Estuary, southern China: Pore water profiles and sediment incubations revealed benthic early diagenesis as well as sediment–water exchange of dissolved nutrients and oxygen, while tidal sampling of estuarine and mangrove water identified source and sink functions of the entire mangrove forest. Fluxes of oxygen during incubations were always directed into the sediment, indicating heterotrophy of the system. There was a net uptake of dissolved inorganic nitrogen, mainly caused by nitrate influx, while ammonium and nitrite showed variable flux direction. Despite high pore water concentrations, phosphate and silica showed net uptake. Fluxes of dissolved organic carbon were generally low except for high efflux in the dark following a storm event. Due to the combination of small forest area and strong anthropogenic nutrient input, the net sink function for dissolved nitrogen and phosphorus provides no significant buffer against the eutrophication of coastal waters.

  16. Silica Microcapsules Prepared by Interfacial Reaction Methods

    Institute of Scientific and Technical Information of China (English)

    M; Fujiwara; K; Shiokawa; Y; Nakahara

    2007-01-01

    1 Results Silica spherical particles with hollow structure are directly prepared by interfacial reaction methods using W/O/W emulsion (schematic diagram in Fig.1)[1].Fig.1 Silica microcapsule formationThe mixing of W/O emulsion consisting of sodium silicate solution (inner water phase) and n-hexane solution (oil phase) to outer water phase dissolving NH4HCO3 or other salts affords silica microcapsules.The critical feature of this method is the direct formation of hollow structure.Therefore,the core com...

  17. Groundfish overfishing, diatom decline, and the marine silica cycle: Lessons from Saanich Inlet, Canada, and the Baltic Sea cod crash

    Science.gov (United States)

    Katz, Timor; Yahel, Gitai; Yahel, Ruthy; Tunnicliffe, Verena; Herut, Barak; Snelgrove, Paul; Crusius, John; Lazar, Boaz

    2009-12-01

    In this study, we link groundfish activity to the marine silica cycle and suggest that the drastic mid-1980s crash of the Baltic Sea cod (Gadus morhua) population triggered a cascade of events leading to decrease in dissolved silica (DSi) and diatom abundance in the water. We suggest that this seemingly unrelated sequence of events was caused by a marked decline in sediment resuspension associated with reduced groundfish activity resulting from the cod crash. In a study in Saanich Inlet, British Columbia, Canada, we discovered that, by resuspending bottom sediments, groundfish triple DSi fluxes from the sediments and reduce silica accumulation therein. Using these findings and the available oceanographic and environmental data from the Baltic Sea, we estimate that overfishing and recruitment failure of Baltic cod reduced by 20% the DSi supply from bottom sediments to the surface water leading to a decline in the diatom population in the Baltic Sea. The major importance of the marginal ocean in the marine silica cycle and the associated high population density of groundfish suggest that groundfish play a major role in the silica cycle. We postulate that dwindling groundfish populations caused by anthropogenic perturbations, e.g., overfishing and bottom water anoxia, may cause shifts in marine phytoplankton communities.

  18. Astronomical pacing of the global silica cycle recorded in Mesozoic bedded cherts

    Science.gov (United States)

    Ikeda, Masayuki; Tada, Ryuji; Ozaki, Kazumi

    2017-06-01

    The global silica cycle is an important component of the long-term climate system, yet its controlling factors are largely uncertain due to poorly constrained proxy records. Here we present a ~70 Myr-long record of early Mesozoic biogenic silica (BSi) flux from radiolarian chert in Japan. Average low-mid-latitude BSi burial flux in the superocean Panthalassa is ~90% of that of the modern global ocean and relative amplitude varied by ~20-50% over the 100 kyr to 30 Myr orbital cycles during the early Mesozoic. We hypothesize that BSi in chert was a major sink for oceanic dissolved silica (DSi), with fluctuations proportional to DSi input from chemical weathering on timescales longer than the residence time of DSi (model support these hypotheses, excluding the volcanism-driven oceanic anoxic events of the Early-Middle Triassic and Toarcian that exceed model limits. We propose that the Mega monsoon of the supercontinent Pangea nonlinearly amplified the orbitally paced chemical weathering that drove BSi burial during the early Mesozoic greenhouse world.

  19. Benthic flux of nutrients and trace metals in the northern component of San Francisco Bay, California

    Science.gov (United States)

    Kuwabara, James S.; Topping, Brent R.; Parcheso, Francis; Engelstad, Anita C.; Greene, Valerie E.

    2009-01-01

    ), except for one site with statistically insignificant nitrate fluxes (Site 409 within Suisun Bay). The most negative nitrate flux (-7.3?0.1 mmole m-2d-1) was observed within Grizzly Bay (Site 416). Observed nitrate fluxes bracketed the estimated summer fluvial flux of nitrate (3,500 to 5,000 kg-N d-1). With the exception of the two Grizzly Bay sites (416 and 417), the consistently positive benthic flux of ammonia generally counteracted the negative flux of nitrate to yield a net balance of dissolved inorganic nitrogen. Ammonia benthic fluxes extrapolated for Suisun Bay ranged from 320 kg-N d-1 (Site SSB009 near the entrance to Honker Bay) to 1,900 kg-N d-1 (Montezuma Island). These values represent a significant ammonia source to the water column relative to summer riverine inputs (approximately 400 to 600 kg-N d-1). Dissolved silica also displayed a consistently positive benthic flux, except for Site 409 within Suisun Bay, which showed insignificant fluxes (also insignificant for nitrate and SRP). As with the nitrate fluxes, Grizzly Bay and Browns Island sites yielded the highest dissolved silica fluxes (1.3?1.2 to 2.5?0.6 mmole m-2d-1, respectively). These initial diffusive-flux estimates are greater than those measured in the South Bay using core-incubation experiments, which include bioturbation and bioirrigation effects, but they are nevertheless probably one to t

  20. Sediment DSi and DIP fluxes under simulated redox conditions

    Science.gov (United States)

    Nteziryayo, Love-Raoul; Danielsson, Åsa

    2017-04-01

    The Baltic Sea is one of the most eutrophic water bodies in the world. This eutrophication of the Baltic Sea has resulted in the expansion of areas of hypoxic bottom waters. Hypoxia is known to cause the release of dissolved inorganic phosphorus (DIP) from sediment. It is largely assumed that dissolved silica (DSi) reacts in an analogous way in hypoxic conditions. From sediment incubation experiments, we found that P reacts faster to oxygen changes than Si. Here we show that DSi and DIP behave differently to changing oxygen concentrations in the bottom waters, and that the adsorption and de-sorption on Fe oxihydroxides may control the release of P more efficiently than of Si. The results showed that DSi fluxes were higher under oxic conditions (2.21±0.28 mmol Si m-2d-1) than under hypoxic conditions (1.36±0.29 mmol Si m-2d-1). The opposite was observed for P fluxes (0.06 ±0.01 and 0.10±0.09 mmol P m-2d-1) under oxic respective hypoxic conditions). Our results indicate that the increase of hypoxic conditions in coastal areas may directly cause the decrease of Si fluxes from sediment and thereby contribute to the diminishing Si concentrations observed in the Baltic Sea waters.

  1. Sedimentary and mineral dust sources of dissolved iron to the world ocean

    Directory of Open Access Journals (Sweden)

    J. K. Moore

    2008-05-01

    Full Text Available Analysis of a global compilation of dissolved-iron observations provides insights into the processes controlling iron distributions and some constraints for ocean biogeochemical models. The distribution of dissolved iron appears consistent with the conceptual model developed for Th isotopes, whereby particle scavenging is a two-step process of scavenging mainly by colloidal and small particulates, followed by aggregation and removal on larger sinking particles. Much of the dissolved iron (<0.4 μm is present as small colloids (>~0.02 μm and, thus, is subject to aggregation and scavenging removal. This implies distinct scavenging regimes for dissolved iron consistent with the observations: 1 a high scavenging regime – where dissolved-iron concentrations exceed the concentrations of strongly binding organic ligands; and 2 a moderate scavenging regime – where dissolved iron is bound to both colloidal and soluble ligands. Within the moderate scavenging regime, biological uptake and particle scavenging decrease surface iron concentrations to low levels (<0.2 nM over a wide range of low to moderate iron input levels. Removal rates are also highly nonlinear in areas with higher iron inputs. Thus, observed surface-iron concentrations exhibit a bi-modal distribution and are a poor proxy for iron input rates. Our results suggest that there is substantial removal of dissolved iron from subsurface waters (where iron concentrations are often well below 0.6 nM, most likely due to aggregation and removal on sinking particles of Fe bound to organic colloids.

    We use the observational database to improve simulation of the iron cycle within a global-scale, Biogeochemical Elemental Cycling (BEC ocean model. Modifications to the model include: 1 an improved particle scavenging parameterization, based on the sinking mass flux of particulate organic material, biogenic silica, calcium carbonate, and mineral dust particles; 2 desorption of dissolved iron

  2. Preparation and Characterization of Silica-Enoxil Nanobiocomposites

    Science.gov (United States)

    Kuzema, Pavlo O.; Laguta, Iryna V.; Stavinskaya, Oksana N.; Kazakova, Olga A.; Borysenko, Mykola V.; Lupaşcu, Tudor

    2016-02-01

    Silica-Enoxil nanobiocomposites with 13 %w of Enoxil were prepared either by mechanical mixing of corresponding powders or by sorptive modification of fumed silica powder with aqueous Enoxil solution under fluidized bed conditions. The interaction of fumed silica with Enoxil and the properties of silica-Enoxil composites have been investigated using IR spectroscopy, thermogravimetric analysis, and quantum chemistry methods, as well as by means of water absorption, Enoxil desorption, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) test. It has been shown that the main biomolecules of Enoxil composition interact with silica involving their hydroxyl groups and surface silanol groups. The water absorption of silica-Enoxil nanocomposites was found to be less than that for the individual components. The Enoxil biomolecules are readily and completely desorbed from silica surface into water, and the antioxidant activity of desorbed Enoxil is practically the same as that for the just dissolved one.

  3. The silica dynamics of deforestation: new evidence for a biologically controlled Si cycle

    Science.gov (United States)

    Struyf, Eric; Smis, Adriaan; Clymans, Wim; Govers, Gerard; van Wesemael, Bas; Frot, Elisabeth; Batelaan, Okke; Goos, Peter; van Damme, Stefan; Meire, Patrick

    2010-05-01

    Amorphous, biogenic Si (ASi) is stored in large amounts in terrestrial ecosystems. The study of this terrestrial ASi pool and its influence on watershed scale silica fluxes, remains in an absolute pioneer research stage. These Si budget studies have not included the biogenic amorphous Si stock and related fluxes. This hampers our ability to accurately quantify terrestrial cycling of Si, which is -through ocean carbon burial and CO2 uptake during terrestrial Si weathering- intricately linked to global carbon budgets. We have studied detailed year-round concentration and flux patterns of dissolved (DSi) and amorphous Si in 60 small watersheds in the Scheldt river basin. Results show that transport of Si through the catchments is controlled by a complex set of terrestrial and aquatic processes, with land use and prominence of ecosystem types an important controlling factor. Based on high frequency discharge measurements and concurrent analysis of ASi and DSi concentrations during intense precipitation events, we were able to attribute a percentage of yearly ASi and DSi fluxes to both base flow and precipitation event related surface run-off. Our results show ASi and DSi concentrations in upstream river basins are intricately linked to each other and to discharge, and ASi transport constitutes an important part of the total transport of Si. The ASi mainly originates from agricultural cropland soils. We have also developed a new concept accounting for changes in silica fluxes after deforestation on different time-scales. Our concept is supported by previously collected datasets, and our new comprehensive dataset in the Scheldt River basin. The combined results indicate that immediately after deforestation, silica fluxes increase as a result of a recycling pulse of DSi from forest soil ASi, as well as increased ASi efflux. When the soil ASi pool is depleted, a new equilibrium is reached, where DSi fluxes are low compared to the pristine forest equilibrium phase. The

  4. Sedimentary and mineral dust sources of dissolved iron to the World Ocean

    Directory of Open Access Journals (Sweden)

    J. K. Moore

    2007-04-01

    Full Text Available A worldwide database of dissolved iron observations is used to improve simulations of the marine iron cycle within a global-scale, Biogeochemical Elemental Cycling (BEC ocean model. Modifications to the model include: 1 an improved particle scavenging parameterization based on the sinking mass flux of particulate organic material, biogenic silica, calcium carbonate, and mineral dust particles; 2 desorption of dissolved iron from sinking particles; and 3 an improved sedimentary source for dissolved iron. Most scavenged iron (90% is put on sinking particles to remineralize deeper in the water column. The model-observation mismatches are greatly reduced both in surface waters and in the deeper ocean. Inclusion of desorption has little effect on surface water iron concentrations where adsorption/scavenging is strongly dominant, but significantly increases simulated iron concentrations in the deep ocean. Our results suggest that there must be substantial removal of dissolved iron from subsurface waters (where iron concentrations are <0.6 nM in most regions to match observed distributions. Aggregation and removal on sinking particles of Fe bound to organic colloids is a likely mechanism.

    The improved BEC model is used to address the relative contributions of mineral dust and marine sediments in driving ocean productivity and observed dissolved iron distributions. The sedimentary iron source from the continental margins has a strong impact on open ocean iron concentrations, particularly in the North Pacific. Plumes of elevated dissolved iron concentrations develop at depth in the Southern Ocean, extending from source regions in the SW Atlantic and around New Zealand. The lower particle flux and weaker scavenging in this region allows the continental iron source to be advected far from source areas. Both the margin sediment and mineral dust Fe sources significantly impact global scale primary production, export production, and nitrogen fixation

  5. Silica cycling in the ultra-oligotrophic Eastern Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    M. D. Krom

    2014-03-01

    Full Text Available Although silica is a key plant nutrient there have been few studies aimed at understanding the Si cycle in the Eastern Mediterranean Sea (EMS. Here we use a combination of new measurements and literature values to explain the silicic acid distribution across the basin and to calculate a silica budget to identify the key controlling processes. The surface water concentration of ~ 1 μM, which is unchanging seasonally across the basin was due to the inflow of Western Mediterranean Sea (WMS water at the Straits of Sicily. It does not change seasonally because there is only a sparse population of diatoms due to the low nutrient (N and P supply to the photic zone in the EMS. The concentration of silicic acid in the deep water of the western Ionian Sea (6.3 μM close to the S. Adriatic area of formation was due to the preformed silicic acid (3 μM plus biogenic silica (BSi from the dissolution of diatoms from the winter phytoplankton bloom (3.2 μM. The increase of 4.4 μM across the deep water of the EMS was due to silicic acid formed from in-situ diagenetic weathering of alumina-silicate minerals fluxing out of the sediment. The major inputs to the EMS are silicic acid and BSi inflowing from the western Mediterranean (121 × 109 mol Si year−1 silicic acid and 16 × 109 mol Si year−1 BSi, silicic acid fluxing from the sediment (54 × 109 mol Si year−1, riverine (27 × 109 mol Si year−1 and subterranean ground water (9.7 × 109 mol Si year−1 inputs, with only a minor direct input from dissolution of dust in the water column (1 × 109 mol Si year−1. This budget shows the importance of rapidly dissolving BSi and in-situ weathering of alumino-silicate minerals as sources of silica to balance the net export of silicic acid at the Straits of Sicily. Future measurements to improve the accuracy of this preliminary budget have been identified.

  6. Biomimetic silica encapsultation of living cells

    Science.gov (United States)

    Jaroch, David Benjamin

    Living cells perform complex chemical processes on size and time scales that artificial systems cannot match. Cells respond dynamically to their environment, acting as biological sensors, factories, and drug delivery devices. To facilitate the use of living systems in engineered constructs, we have developed several new approaches to create stable protective microenvironments by forming bioinspired cell-membrane-specific silica-based encapsulants. These include vapor phase deposition of silica gels, use of endogenous membrane proteins and polysaccharides as a site for silica nucleation and polycondensation in a saturated environment, and protein templated ordered silica shell formation. We demonstrate silica layer formation at the surface of pluripotent stem-like cells, bacterial biofilms, and primary murine and human pancreatic islets. Materials are characterized by AFM, SEM and EDS. Viability assays confirm cell survival, and metabolite flux measurements demonstrate normal function and no major diffusion limitations. Real time PCR mRNA analysis indicates encapsulated islets express normal levels of genetic markers for β-cells and insulin production. The silica glass encapsulant produces a secondary bone like calcium phosphate mineral layer upon exposure to media. Such bioactive materials can improve device integration with surrounding tissue upon implantation. Given the favorable insulin response, bioactivity, and long-term viability observed in silica-coated islets, we are currently testing the encapsulant's ability to prevent immune system recognition of foreign transplants for the treatment of diabetes. Such hybrid silica-cellular constructs have a wide range of industrial, environmental, and medical applications.

  7. Vegetation and proximity to the river control amorphous silica storage in a riparian wetland (Biebrza National Park, Poland

    Directory of Open Access Journals (Sweden)

    E. Struyf

    2009-01-01

    Full Text Available Wetlands can modify and control nutrient fluxes between terrestrial and aquatic ecosystems, yet little is known of their potential as biological buffers and sinks in the biogeochemical silica cycle. We investigated the storage of amorphous silica (ASi in a central-European riparian wetland. The variation in storage of ASi in the soil of an undisturbed wetland was significantly controlled by two factors: dominance of sedges and grasses and distance to the river (combined R2=78%. Highest ASi storage was found near the river and in sites with a dominance of grasses and sedges, plants which are well known to accumulate ASi. The management practice of mowing reduced the amount of variation attributed to both factors (R2=51%. Although ASi concentrations in soils were low (between 0.1 and 1% of soil dry weight, ASi controlled the availability of dissolved silica (DSi in the porewater, and thus potentially the exchange of DSi with the nearby river system through both diffusive and advective fluxes. A depth gradient in ASi concentrations, with lower ASi in the deeper layers, indicates dissolution. Our results show that storage and recycling of ASi in wetland ecosystems can differ significantly on small spatial scales. Human management interferes with the natural control mechanisms. Our study demonstrates that wetlands have the potential to modify the fluxes of both DSi and ASi along the land-ocean continuum and supports the hypothesis that wetlands are important ecosystems in the biogeochemical cycling of silica.

  8. Winter climate change and fine root biogenic silica in sugar maple trees (Acer saccharum): Implications for silica in the Anthropocene

    Science.gov (United States)

    Maguire, Timothy J.; Templer, Pamela H.; Battles, John J.; Fulweiler, Robinson W.

    2017-03-01

    Winter temperatures are projected to increase over the next century, leading to reductions in winter snowpack and increased frequency of soil freezing in many northern forest ecosystems. Here we examine biogenic silica (BSi) concentrations in sugar maple (Acer saccharum) fine roots collected from a snow manipulation experiment at Hubbard Brook Experimental Forest (New Hampshire, USA). Increased soil freezing significantly lowered the BSi content of sugar maple fine roots potentially decreasing their capacity to take up water and dissolved nutrients. The reduced silica uptake (8 ± 1 kmol silica km-2) by sugar maple fine roots is comparable to silica export from temperate forest watersheds. We estimate that fine roots account for 29% of sugar maple BSi, despite accounting for only 4% of their biomass. These results suggest that increased frequency of soil freezing will reduce silica uptake by temperate tree roots, thereby changing silica availability in downstream receiving waters.

  9. Flux patterns and membrane fouling propensity during desalination of seawater by forward osmosis

    KAUST Repository

    Li, Zhenyu

    2012-01-01

    The membrane fouling propensity of natural seawater during forward osmosis was studied. Seawater from the Red Sea was used as the feed in a forward osmosis process while a 2. M sodium chloride solution was used as the draw solution. The process was conducted in a semi-batch mode under two crossflow velocities, 16.7. cm/s and 4.2. cm/s. For the first time reported, silica scaling was found to be the dominant inorganic fouling (scaling) on the surface of membrane active layer during seawater forward osmosis. Polymerization of dissolved silica was the major mechanism for the formation of silica scaling. After ten batches of seawater forward osmosis, the membrane surface was covered by a fouling layer of assorted polymerized silica clusters and natural organic matter, especially biopolymers. Moreover, the absorbed biopolymers also provided bacterial attachment sites. The accumulated organic fouling could be partially removed by water flushing while the polymerized silica was difficult to remove. The rate of flux decline was about 53% with a crossflow velocity of 16.7. cm/s while reaching more than 70% with a crossflow velocity of 4.2. cm/s. Both concentration polarization and fouling played roles in the decrease of flux. The salt rejection was stable at about 98% during seawater forward osmosis. In addition, an almost complete rejection of natural organic matter was attained. The results from this study are valuable for the design and development of a successful protocol for a pretreatment process before seawater forward osmosis and a cleaning method for fouled membranes. © 2011 Elsevier Ltd.

  10. Flux patterns and membrane fouling propensity during desalination of seawater by forward osmosis.

    Science.gov (United States)

    Li, Zhen-Yu; Yangali-Quintanilla, Victor; Valladares-Linares, Rodrigo; Li, Qingyu; Zhan, Tong; Amy, Gary

    2012-01-01

    The membrane fouling propensity of natural seawater during forward osmosis was studied. Seawater from the Red Sea was used as the feed in a forward osmosis process while a 2M sodium chloride solution was used as the draw solution. The process was conducted in a semi-batch mode under two crossflow velocities, 16.7 cm/s and 4.2 cm/s. For the first time reported, silica scaling was found to be the dominant inorganic fouling (scaling) on the surface of membrane active layer during seawater forward osmosis. Polymerization of dissolved silica was the major mechanism for the formation of silica scaling. After ten batches of seawater forward osmosis, the membrane surface was covered by a fouling layer of assorted polymerized silica clusters and natural organic matter, especially biopolymers. Moreover, the absorbed biopolymers also provided bacterial attachment sites. The accumulated organic fouling could be partially removed by water flushing while the polymerized silica was difficult to remove. The rate of flux decline was about 53% with a crossflow velocity of 16.7 cm/s while reaching more than 70% with a crossflow velocity of 4.2 cm/s. Both concentration polarization and fouling played roles in the decrease of flux. The salt rejection was stable at about 98% during seawater forward osmosis. In addition, an almost complete rejection of natural organic matter was attained. The results from this study are valuable for the design and development of a successful protocol for a pretreatment process before seawater forward osmosis and a cleaning method for fouled membranes.

  11. Rate equations for sodium catalyzed amorphous silica dissolution

    Science.gov (United States)

    Rimstidt, J. Donald; Zhang, Yilun; Zhu, Chen

    2016-12-01

    Newly measured amorphous silica dissolution rate data were combined with data from the literature to produce an equation that predicts the dissolution flux (J, mol/m2 s) of amorphous silica as a function of temperature (T, K), sodium concentration (mNa+, molal), and hydrogen ion activity (aH+).

  12. Complex coacervation between colloidal silica and polyacrylamide

    Energy Technology Data Exchange (ETDEWEB)

    Kawase, Kaoru; Sakami, Hiroshi; Hayakawa, Kiyoshi

    1989-03-01

    Complex coacervation introduced by gamma-ray induced polymerization of acrylamide in colloidal silica was studied. The complex coaservate was formed by polymerization of acrylamide dissolved in a colloidal silica and methanol mixture. Complex coacervation (two-phase separation of the mixture) was observed only when the concentration of methanol was between 33 and 41 percent by volume, and the concentration of colloidal silica did not affect it. Although two phase separation was not influenced by pH change, the content of polyacrylamide was bigger in the equilibrated solution in acidic regions. It was, however, bigger in the complex coacervate at neutral and in alkaline regions. The content of polyacrylamide was also calculated from the particle diameter of complex coacervate measured by small angle X-ray scattering, and the result was well coincided with the analytical result. The stability of the complex coacervate against the addition of salts was better than that of the untreated colloidal silica. The rate of electrophoretic transport of the complex coacervate was also lower than that of the colloidal silica. From these observation it was concluded that the hydrophobic colloidal silica particles were protected by the surrounding hydrophilic polyacrylamide. (author).

  13. Silica scaling in forward osmosis: From solution to membrane interface.

    Science.gov (United States)

    Xie, Ming; Gray, Stephen R

    2017-01-01

    Membrane silica scaling hinders sustainable water production. Understanding silica scaling mechanisms provides options for better membrane process management. In this study, we elucidated silica scaling mechanisms on an asymmetric cellulose triacetate (CTA) membrane and polyamide thin-film composite (TFC) membrane. Scaling filtration showed that TFC membrane was subjected to more severe water flux decline in comparison with the CTA membrane, together with different scaling layer morphology. To elucidate the silica scaling mechanisms, silica species in the aqueous solution were characterised by mass spectrometry as well as light scattering. Key thermodynamic parameters of silica surface nucleation on the CTA and TFC membranes were estimated to compare the surface nucleation energy barrier. In addition, high resolution X-ray photoelectron spectroscopy resolved the chemical origin of the silica-membrane interaction via identifying the specific silicon bonds. These results strongly support that silica scaling in the CTA membrane was driven by the aggregation of mono-silicic acid into large silica aggregates, followed by the deposition from bulk solution onto the membrane surface; by contrast, silica polymerised on the TFC membrane surface where mono-silicic acid interacted with TFC membrane surface, which was followed by silica surface polymerisation.

  14. Silica in Protoplanetary Disks

    CERN Document Server

    Sargent, B A; Tayrien, C; McClure, M K; Li, A; Basu, A R; Manoj, P; Watson, D M; Bohac, C J; Furlan, E; Kim, K H; Green, J D; Sloan, G C

    2008-01-01

    Mid-infrared spectra of a few T Tauri stars (TTS) taken with the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope show prominent narrow emission features indicating silica (crystalline silicon dioxide). Silica is not a major constituent of the interstellar medium; therefore, any silica present in the circumstellar protoplanetary disks of TTS must be largely the result of processing of primitive dust material in the disks surrouding these stars. We model the silica emission features in our spectra using the opacities of various polymorphs of silica and their amorphous versions computed from earth-based laboratory measurements. This modeling indicates that the two polymorphs of silica, tridymite and cristobalite, which form at successively higher temperatures and low pressures, are the dominant forms of silica in the TTS of our sample. These high temperature, low pressure polymorphs of silica present in protoplanetary disks are consistent with a grain composed mostly of tridymite named Ada found...

  15. Multifunctional mesoporous silica catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Victor Shang-Yi; Tsai, Chih-Hsiang; Chen, Hung-Ting; Pruski, Marek; Kobayashi, Takeshi

    2015-03-31

    The present invention provides bifunctional silica mesoporous materials, including mesoporous silica nanoparticles ("MSN"), having pores modified with diarylammonium triflate and perfluoroaryl moieties, that are useful for the acid-catalyzed esterification of organic acids with organic alcohols.

  16. Silica extraction from geothermal water

    Science.gov (United States)

    Bourcier, William L; Bruton, Carol J

    2014-09-23

    A method of producing silica from geothermal fluid containing low concentration of the silica of less than 275 ppm includes the steps of treating the geothermal fluid containing the silica by reverse osmosis treatment thereby producing a concentrated fluid containing the silica, seasoning the concentrated fluid thereby producing a slurry having precipitated colloids containing the silica, and separating the silica from the slurry.

  17. Concentration-discharge relationships during an extreme event: Contrasting behavior of solutes and changes to chemical quality of dissolved organic material in the Boulder Creek Watershed during the September 2013 flood: SOLUTE FLUX IN A FLOOD EVENT

    Energy Technology Data Exchange (ETDEWEB)

    Rue, Garrett P. [Institute of Arctic and Alpine Research, University of Colorado, Boulder Colorado USA; Rock, Nathan D. [Institute of Arctic and Alpine Research, University of Colorado, Boulder Colorado USA; Gabor, Rachel S. [Institute of Arctic and Alpine Research, University of Colorado, Boulder Colorado USA; Pitlick, John [Department of Geography, University of Colorado, Boulder Colorado USA; Tfaily, Malak [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland Washington USA; McKnight, Diane M. [Institute of Arctic and Alpine Research, University of Colorado, Boulder Colorado USA

    2017-07-01

    During the week of September 10-17, 2013, close to 20 inches of rain fell across Boulder County, Colorado, USA. This rainfall represented a 1000-year event that caused massive hillslope erosion, landslides, and mobilization of sediments. The resultant stream flows corresponded to a 100-year flood. For the Boulder Creek Critical Zone Observatory (BC-CZO), this event provided an opportunity to study the effect of extreme rainfall on solute concentration-discharge relationships and biogeochemical catchment processes. We observed base cation and dissolved organic carbon (DOC) concentrations at two sites on Boulder Creek following the recession of peak flow. We also isolated three distinct fractions of dissolved organic matter (DOM) for chemical characterization. At the upper site, which represented the forested mountain catchment, the concentrations of the base cations Ca, Mg and Na were greatest at the peak flood and decreased only slightly, in contrast with DOC and K concentrations, which decreased substantially. At the lower site within urban corridor, all solutes decreased abruptly after the first week of flow recession, with base cation concentrations stabilizing while DOC and K continued to decrease. Additionally, we found significant spatiotemporal trends in the chemical quality of organic matter exported during the flood recession, as measured by fluorescence, 13C-NMR spectroscopy, and FTICR-MS. Similar to the effect of extreme rainfall events in driving landslides and mobilizing sediments, our findings suggest that such events mobilize solutes by the flushing of the deeper layers of the critical zone, and that this flushing regulates terrestrial-aquatic biogeochemical linkages during the flow recession.

  18. Dissolved organic carbon and nitrogen leaching from Scots pine, Norway spruce and silver birch stands in southern Sweden

    OpenAIRE

    Fröberg, Mats; Hansson, Karna; Kleja, Dan Berggren; Alavi, Ghasem

    2011-01-01

    The effects of three common tree species – Scots pine, Norway spruce and silver birch – on leaching of dissolved organic carbon and dissolved nitrogen were studied in an experimental forest with podzolised soils in southern Sweden. We analyzed soil water collected with lysimeters and modeled water fluxes to estimate dissolved C and N fluxes. Specific UV absorbance (SUVA) was analyzed to get information about the quality of dissolved organic matter leached from the different stands. Under the ...

  19. Composition and variability in the export of biogenic silica in the Changjiang River and the effect of Three Gorges Reservoir.

    Science.gov (United States)

    Ran, Xiangbin; Liu, Sen; Liu, Jun; Zang, Jiaye; Che, Hong; Ma, Yongxing; Wang, Yibin

    2016-11-15

    Silicon (Si) plays an essential role in biogeochemical processes, but is still poorly characterized in the river system. This study addressed the biogenic silica (BSi) composition, origin and variation in the Changjiang River, and estimated the impacts of natural processes and human activities on the river Si cycling. Our results indicate that phytoliths comprised 14%-64% of BSi, while diatoms accounted for 34%-85% of BSi. The Changjiang River transported 620Ggyr(-1) of BSi and 2100Ggyr(-1) of dissolved silicate (DSi) loadings, respectively; 55% of the BSi and 51% of the DSi fluxes are transported during the high discharge period from June to September. The Changjiang River carried phytolith BSi mostly comes from the middle and lower reaches area. The ratio of BSi/(BSi+DSi) has decreased from 0.47 before 1980 to 0.19 in 2013-2014 due to the direct retention of BSi. The BSi sedimentation in the Three Gorges Reservoir would cause a decrease of total reactive silica, but contribute to approximately 4%-16% of the DSi loading at the Jiangyin station due to its dissolution. This study demonstrates that phytoliths represent a significant contribution to the biogeochemical cycle of silica in coastal waters, and in-stream process exerts a great influence on the river Si loading and cycling. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. A biorefinery scheme to fractionate bamboo into high-grade dissolving pulp and ethanol.

    Science.gov (United States)

    Yuan, Zhaoyang; Wen, Yangbing; Kapu, Nuwan Sella; Beatson, Rodger; Mark Martinez, D

    2017-01-01

    Bamboo is a highly abundant source of biomass which is underutilized despite having a chemical composition and fiber structure similar as wood. The main challenge for the industrial processing of bamboo is the high level of silica, which forms water-insoluble precipitates negetively affecting the process systems. A cost-competitive and eco-friendly scheme for the production of high-purity dissolving grade pulp from bamboo not only requires a process for silica removal, but also needs to fully utilize all of the materials dissolved in the process which includes lignin, and cellulosic and hemicellulosic sugars as well as the silica. Many investigations have been carried out to resolve the silica issue, but none of them has led to a commercial process. In this work, alkaline pretreatment of bamboo was conducted to extract silica prior to pulping process. The silica-free substrate was used to produce high-grade dissolving pulp. The dissolved silica, lignin, hemicellulosic sugars, and degraded cellulose in the spent liquors obtained from alkaline pretreatment and pulping process were recovered for providing high-value bio-based chemicals and fuel. An integrated process which combines dissolving pulp production with the recovery of excellent sustainable biofuel and biochemical feedstocks is presented in this work. Pretreatment at 95 °C with 12% NaOH charge for 150 min extracted all the silica and about 30% of the hemicellulose from bamboo. After kraft pulping, xylanase treatment and cold caustic extraction, pulp with hemicellulose content of about 3.5% was obtained. This pulp, after bleaching, provided a cellulose acetate grade dissolving pulp with α-cellulose content higher than 97% and hemicellulose content less than 2%. The amount of silica and lignin that could be recovered from the process corresponded to 95 and 77.86% of the two components in the original chips, respectively. Enzymatic hydrolysis and fermentation of the concentrated and detoxified sugar mixture

  1. Isotopic Clues on Factors Controlling Geochemical Fluxes From Large Watersheds in Eastern Canada

    Science.gov (United States)

    Rosa, E.; Helie, J.; Ghaleb, B.; Hillaire-Marcel, C.; Gaillardet, J.

    2008-12-01

    A monitoring and monthly sampling program of the Nelson, Ottawa, St. Lawrence, La Grande and Great Whale rivers was started in September 2007. It provides information on the seasonality and sources of geochemical fluxes into the Hudson Bay and the North Atlantic from watersheds covering more than 2.6 106 km2 of the eastern Canadian boreal domain. Measurements of pH and alkalinity, analyses of major ions, strontium and dissolved silica, 2H and 18O of water, concentrations and isotopic properties of dissolved organic and inorganic carbon (13C) and uranium (234U/238U) were performed. Lithology more than latitudinal climatic gradients controls the river geochemistry. Rivers draining silicate terrains show lower dissolved U concentrations but greater 234U/238U disequilibria than rivers draining carbonates (average of 1.38 vs. 1.23). Groundwater supplies might exert some control on these U- isotope signatures. No clear seasonality is observed in 234U/238U ratios, but U concentrations are correlated to dissolved organic carbon (DOC) concentrations in most rivers. Rivers draining carbonates present higher total dissolved carbon concentrations and higher 13C-contents in dissolved inorganic carbon (DIC), in response to the dissolution of soil carbonates. DOC/DIC ratios above 2.4 are observed in rivers draining silicates; their lower 13C-DIC content directly reflects the organic matter oxidation in soils. Total dissolved solids are one order of magnitude or more greater in rivers draining carbonates, showing the strong difference in chemical weathering rates according to the geological setting. The stability in chemical fluxes and water isotopic compositions in the La Grande River, which hosts hydroelectric reservoirs covering more than 12 000 km2, indicates that it is the most buffered hydrological system among the investigated watersheds. Seasonal fluctuations are observed elsewhere, with maximum geochemical fluxes during the spring snowmelt. 2H-18O content of river water

  2. Microporous Silica Based Membranes for Desalination

    Directory of Open Access Journals (Sweden)

    João C. Diniz da Costa

    2012-09-01

    Full Text Available This review provides a global overview of microporous silica based membranes for desalination via pervaporation with a focus on membrane synthesis and processing, transport mechanisms and current state of the art membrane performance. Most importantly, the recent development and novel concepts for improving the hydro-stability and separating performance of silica membranes for desalination are critically examined. Research into silica based membranes for desalination has focussed on three primary methods for improving the hydro-stability. These include incorporating carbon templates into the microporous silica both as surfactants and hybrid organic-inorganic structures and incorporation of metal oxide nanoparticles into the silica matrix. The literature examined identified that only metal oxide silica membranes have demonstrated high salt rejections under a variety of feed concentrations, reasonable fluxes and unaltered performance over long-term operation. As this is an embryonic field of research several target areas for researchers were discussed including further improvement of the membrane materials, but also regarding the necessity of integrating waste or solar heat sources into the final process design to ensure cost competitiveness with conventional reverse osmosis processes.

  3. Concentrations and Fluxes of Dissolved Organic Carbon in the Soil Percolating Water of Chinese Fir Plantation%杉木林土壤渗滤水溶解有机碳含量与迁移

    Institute of Scientific and Technical Information of China (English)

    俞元春; 何晟; Wang G.Geoff; 李淑芬

    2006-01-01

    森林是陆地生态系统中最重要的碳库,森林土壤中的碳占全球土壤有机碳的73%,在全球碳循环中起着重要作用(David et a1.,1988)。溶解有机碳(dissolved organic carbon,简称DOC)虽然仅占有机碳的很小部分,但对调节阳离子淋洗、金属溶解、矿物风化、土壤微生物活动以及其他土壤化学、物理和生物学过程具有重要意义。DOC是土壤活性物质,容易被土壤微生物分解,在提供森林土壤养分方面发挥着重要作用(Dosskey et al.,1997);DOC在水中可溶,对森林土壤生态系统中元素的迁移及铝毒性有深刻影响。

  4. Physicochemical and Biological Zonation of High Temperature Silica and Arsenic-Rich Streams at El Tatio Geyser Field, Chile

    Science.gov (United States)

    Myers, K. D.; Engel, A. S.; Omelon, C. R.; Bennett, P.

    2012-12-01

    El Tatio Geyser Field is a geothermal complex comprised of three main basins in the northern Atacama Desert (Region II), Chile. Located at 4400 m elevation in the Andes Mountains it experiences intense solar radiation and a UV flux 33% higher than at Yellowstone National Park (Wyoming). Local boiling point is 86°C, and geothermal waters are Na-Ca-Cl type with circumneutral pH, high dissolved silica, and high dissolved arsenic concentrations (30-50 ppm). Most thermal features contain scant dissolved inorganic carbon (DIC as CO2(aq) + HCO3- + CO3-2). There is a conspicuous lack of microbial mat development in temperature zones where thick mats are seen at other geothermal sites. This investigation focused on understanding the physicochemical controls on microbial diversity that lead to microbial mat colonization and development within specific thermal regions of the geothermal features. Temperature surveys were done at three geothermal features where microbial mats and water chemistry were sampled, and a high-resolution thermal survey was conducted at one geyser orifice through the discharge channel where chemistry and mineralogy have been characterized, and microbial diversity was evaluated from 16S rRNA gene sequences. At the main study geyser, the stream is 0.25 m wide near its source, and for the first 20 m, the discharge stream is constrained by a solid silica bank with a mineralized channel bottom and no obvious microbial mat development. Temperatures decrease from ~86°C to ~67°C. In this zone sparse filaments were observed on rare sediments below the water surface consisting of ~80% Thermus spp. with rare uncultured Chloroflexus spp. and Candidate Division OP1 sequences. At 12 m, visible red-orange mat development starts on the sides of the channel where bulk water temperature is 67°C. Photosynthetic Chloroflexus spp. dominate red-orange filaments that form the first conspicuous mats (between 43-88% of the 16S rRNA sequences from different samples), with

  5. Determination of silica coating efficiency on metal particles using multiple digestion methods.

    Science.gov (United States)

    Wang, Jun; Topham, Nathan; Wu, Chang-Yu

    2011-10-15

    Nano-sized metal particles, including both elemental and oxidized metals, have received significant interest due to their biotoxicity and presence in a wide range of industrial systems. A novel silica technology has been recently explored to minimize the biotoxicity of metal particles by encapsulating them with an amorphous silica shell. In this study, a method to determine silica coating efficiency on metal particles was developed. Metal particles with silica coating were generated using gas metal arc welding (GMAW) process with a silica precursor tetramethylsilane (TMS) added to the shielding gas. Microwave digestion and Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) were employed to solubilize the metal content in the particles and analyze the concentration, respectively. Three acid mixtures were tested to acquire the appropriate digestion method targeting at metals and silica coating. Metal recovery efficiencies of different digestion methods were compared through analysis of spiked samples. HNO(3)/HF mixture was found to be a more aggressive digestion method for metal particles with silica coating. Aqua regia was able to effectively dissolve metal particles not trapped in the silica shell. Silica coating efficiencies were thus calculated based on the measured concentrations following digestion by HNO(3)/HF mixture and aqua regia. The results showed 14-39% of welding fume particles were encapsulated in silica coating under various conditions. This newly developed method could also be used to examine the silica coverage on particles of silica shell/metal core structure in other nanotechnology areas.

  6. SILICA SURFACED CARBON FIBERS.

    Science.gov (United States)

    carbon fibers . Several economical and simple processes were developed for obtaining research quantities of silica surfaced carbon filaments. Vat dipping processes were utilized to deposit an oxide such as silica onto the surface and into the micropores of available carbon or graphite base fibers. High performance composite materials were prepared with the surface treated carbon fibers and various resin matrices. The ablative characteristics of these composites were very promising and exhibited fewer limitations than either silica or...treated

  7. Silica in higher plants.

    Science.gov (United States)

    Sangster, A G; Hodson, M J

    1986-01-01

    Opaline silica deposits are formed by many vascular (higher) plants. The capacity of these plants for silica absorption varies considerably according to genotype and environment. Plant communities exchange silica between soil and vegetation, especially in warmer climates. Silica deposition in epidermal cell walls offers mechanical and protective advantages. Biogenic silica particles from plants are also implicated in the causation of cancer. Recent techniques are reviewed which may aid in the identification of plant pathways for soluble silica movement to deposition sites and in the determination of ionic environments. Botanical investigations have focused on silicification of cell walls in relation to plant development, using scanning and transmission electron microscopy combined with X-ray microanalysis. Silica deposition in macrohair walls of the lemma of canary grass (Phalaris) begins at inflorescence emergence and closely follows wall thickening. The structure of the deposited silica may be determined by specific organic polymers present at successive stages of wall development. Lowering of transpiration by enclosure of Phalaris inflorescences in plastic bags reduced silica deposition in macrohairs. Preliminary freeze-substitution studies have located silicon, as well as potassium and chloride, in the cell vacuole and wall deposition sites during initial silicification.

  8. Porous Properties of Nano-fibriform Silica from Natural Chrysotile

    Institute of Scientific and Technical Information of China (English)

    WANG Lijuan; LU Anhuai; WANG Changqiu; LI Xuejun; ZHENG Xishen; ZHAO Dongjun; LIU Rui

    2006-01-01

    With the TEM and physical gas adsorption techniques, porous properties of nano-fibriform silica (MLD: 92.73 %) from natural chrysotile are studied in this paper. The results indicate that porous nano-fibriform silica results from brucite octahedral sheets of nature chrysotile dissolved completely and Si-O tetrahedral sheets collapsed by acid leaching. Its length is at a micron or nanometer scale.There are two types of pores: pores among neighboring fibers and pores in nanofiber. These pores (less than 6.5 nm in diameter, mostly 2.1 nm and 3.8 nm) all belong to mesopores. The pores in fibers consist of those among SiO2 particles, those among aggregates, remnant nanotubes and capillary tubes. Nanofibriform silica proves better than the traditional silica as a carrier of catalyzer and a filler for reinforce rubber and plastics.

  9. 柳江流域柳州断面水化学特征及无机碳汇通量分析%Hydrochemical Characteristics and the Dissolved Inorganic Carbon Flux in Liuzhou Section of Liujiang Basin

    Institute of Scientific and Technical Information of China (English)

    原雅琼; 李瑞; 张华生; 何师意; 于奭; 孙平安; 王艳雪; 武招云; 李新桂; 谢明鲜; 刘文

    2015-01-01

    lowest value was observed in summer. Due to the interaction of effect of dilution and effect of CO2 , the seasonal variation of Ca2 +and HCO -3 showed that the highest value was in autumn and the lowest value was in summer. The seasonal variation law of other ions should be attributed to the effect of dilution or agricultural activities or combined action of them. Both carbonic acid and sulfuric acid took part in the chemical weathering of carbonate rocks as evidenced by stoichiometric analysis. Besides, the δ34S of sulfate ion of the river waters (δ34S: from 7. 65‰ to 8. 55‰)showed that SO2 -4 was originated mainly from oxidation of sulfide minerals in ore deposits and acid rain. Chemical mass balance method was applied to estimate the proportion of HCO -3 coming from carbonate weathering by sulfuric acid. The result was 28. 26℅ . On this basis, the total carbon flux of carbon ( by CO2 calculation) in Liuzhou section calculated month by month was about 8. 95 × 105 t.a - 1 . What’s more, the carbon flux showed a positive correlation with flow, which implied that the discharge of catchment was the main influencing factor of carbon flux rather than the HCO -3 concentration.

  10. Speciation of Dissolved Cadmium

    DEFF Research Database (Denmark)

    Holm, Peter Engelund; Andersen, Sjur; Christensen, Thomas Højlund

    1995-01-01

    Equilibrium dialysis and ion exchange methods, as well as computer calculations (GEOCHEM), were applied for speciation of dissolved cadmium (Cd) in test solutions and leachate samples. The leachate samples originated from soil, compost, landfill waste and industrial waste. The ion exchange (IE...

  11. Crystalline Silica Primer

    Science.gov (United States)

    ,

    1992-01-01

    Crystalline silica is the scientific name for a group of minerals composed of silicon and oxygen. The term crystalline refers to the fact that the oxygen and silicon atoms are arranged in a threedimensional repeating pattern. This group of minerals has shaped human history since the beginning of civilization. From the sand used for making glass to the piezoelectric quartz crystals used in advanced communication systems, crystalline silica has been a part of our technological development. Crystalline silica's pervasiveness in our technology is matched only by its abundance in nature. It's found in samples from every geologic era and from every location around the globe. Scientists have known for decades that prolonged and excessive exposure to crystalline silica dust in mining environments can cause silicosis, a noncancerous lung disease. During the 1980's, studies were conducted that suggested that crystalline silica also was a carcinogen. As a result of these findings, crystalline silica has been regulated under the Occupational Safety and Health Administration's (OSHA) Hazard Communication Standard (HCS). Under HCS, OSHAregulated businesses that use materials containing 0.1% or more crystalline silica must follow Federal guidelines concerning hazard communication and worker training. Although the HCS does not require that samples be analyzed for crystalline silica, mineral suppliers or OSHAregulated

  12. Silica Refractory Bricks

    Institute of Scientific and Technical Information of China (English)

    Yu Lingyan; Peng Xigao

    2011-01-01

    @@ 1.Scope This standard specifies the classification,technical requirements,test methods,quality appraisal procedures,packing,marking,transportation,storage,and quality certificate of silica refractory bricks.This standard is applicable to silica refractory bricks with single weight≤40 kg.

  13. Speciation of Dissolved Cadmium

    DEFF Research Database (Denmark)

    Holm, Peter Engelund; Andersen, Sjur; Christensen, Thomas Højlund

    1995-01-01

    Equilibrium dialysis and ion exchange methods, as well as computer calculations (GEOCHEM), were applied for speciation of dissolved cadmium (Cd) in test solutions and leachate samples. The leachate samples originated from soil, compost, landfill waste and industrial waste. The ion exchange (IE...... leachates showed different Cd speciation patterns as expected. Some leachates were dominated by free divalent Cd (1-70%), some by inorganic complexes (1-87%), and some by organic complexes (7-98%)....

  14. Selected methods for dissolved iron (II, III) and dissolved sulfide (-II) determinations in geothermal waters

    Science.gov (United States)

    Vivit, D.V.; Jenne, E.A.

    1985-01-01

    Dissolved sulfide (-II) and dissolved iron (II, III) were determined in geothermal well water samples collected at Cerro Prieto, Mexico. Most samples consisted of liquid and gas (two phases) at the instant of collection; and a subset of samples, referred to as ' flashed ' samples, consisted of pressurized steam samples which were allowed to condense. Sulfide was determined by sulfide specific ion electrode; Fe(II) and Fe(III) plus Fe(II) were determined spectrophotometrically. The precision and accuracy of the methods were evaluated for these high-silica waters with replicate analyses, spike recoveries, and an alternate method. Direct current (d.c.) argon plasma emission spectrometry was the alternate method used for Fe(III)-plus-Fe(II) analyses. Mean dissolved iron concentrations ranged from 20.2 to 834 micrograms/L (ug/L) as Fe(II) and 26.8 to 904 ug/L as Fe(III) plus Fe(II). Mean sulfide concentrations ranged from about 0.01 to 5.3 mg/L (S-II) Generally, higher S(-II) values and larger Fe(II)/Fe(III) ratios were found in the two-phase samples. These findings suggest that the ' flashed ' samples are at a less reduced state than the two-phase samples. (Author 's abstract)

  15. A photochemically resistant component in riverine dissolved black carbon

    Science.gov (United States)

    Dittmar, Thorsten; Riedel, Thomas; Niggemann, Jutta; Vähätalo, Anssi

    2015-04-01

    Rivers transport combustion-derived dissolved black carbon (DBC) to the oceans at an annual flux that is much higher than required to balance the oceanic inventory of DBC. To resolve this mismatch we studied the long-term stability of DBC in ten major world rivers that together account for approximately 1/3 of the global freshwater discharge to the oceans. Riverine DBC was remarkably resistant against microbial degradation, but decomposition of nearly all chromophoric dissolved organic matter under extensive irradiation with simulated sunlight removed almost 80% of DBC. Photochemically transformed DBC was further microbially decomposed by more than 10% in a subsequent one-year long bioassay. Based on these findings, on a global scale, the estimated riverine flux of microbially degraded and photo-resistant DBC is sufficient to replenish the oceans with DBC and likely contributes to the dissolved organic matter pool that persists in the oceans and sequesters carbon for centuries to millennia.

  16. Soluble polymers in sol-gel silica

    Science.gov (United States)

    Beaudry, Christopher Laurent

    In the last few years, the inherent versatility of sol-gel processing has led to a significant research effort on inorganic/organic materials. One method of incorporating an organic phase into sol-gel silica is dissolving an organic polymer in a tetraethylorthosilicate (TEOS) solution, followed by in situ polymerization of silica in the presence of organic polymer. The first part of the study involved the development of a two-step (acid-base) synthesis procedure to allow systematic control of acidity in TEOS solutions. With this procedure, it was possible to increase the pH of the TEOS solution while correlating the acidity and properties. The properties were the gelation time, syneresis rate, drying behavior, and xerogel pore structure, as determined by nitrogen sorption. Furthermore, controlling the acidity was shown to control the silica xerogel pore structure. In the second part of the study, the two-step procedure was used to synthesize silica/poly(ethylene glycol) (PEG), and silica/poly(vinyl acetate) (PVAc) composite materials. The content of organic polymer and the molecular weight were varied. The gelation time, the syneresis rate, the drying behavior, and the pore structure were determined for compositions with 10% PEG (M.W. 2,000), 5, 10, and 15% PEG (M.W. 3,400), and 10 and 25% PVAc (M.W. 83,000). Other compositions and molecular weights of PEG lead to sedimentation. In the PEG compositions, the tendency to phase separate was correlated with the effects of the processing variables on the segregation strength and polymerization rate. The PVAc compositions did not show any visible phase separation during processing, giving the composite xerogels an appearance similar to pure silica. The property differences between gels with PEG and gels with PVAc show the relative strength of the interactions with silica. Both polymers exhibit hydrogen bonding between the phases. In the case of PEG, hydrogen bonding between the ether oxygens of the polymer and silanol

  17. Understanding Your Watershed Fact Sheet: Dissolved Oxygen

    OpenAIRE

    Mesner, Nancy; Geiger, John

    2010-01-01

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

  18. Dissolved organic carbon release by marine macrophytes

    Directory of Open Access Journals (Sweden)

    C. Barrón

    2012-02-01

    Full Text Available Estimates of dissolved organic carbon (DOC release by marine macrophyte communities (seagrass meadows and macroalgal beds were obtained experimentally using in situ benthic chambers. The effect of light availability on DOC release by macrophyte communities was examined in two communities both by comparing net DOC release under light and dark, and by examining the response of net DOC release to longer-term (days experimental shading of the communities. All most 85% of the seagrass communities and almost all of macroalgal communities examined acted as net sources of DOC. There was a weak tendency for higher DOC fluxes under light than under dark conditions in seagrass meadow. There is no relationship between net DOC fluxes and gross primary production (GPP and net community production (NCP, however, this relationship is positive between net DOC fluxes and community respiration. Net DOC fluxes were not affected by shading of a T. testudinum community in Florida for 5 days, however, shading of a mixed seagrass meadow in the Philippines led to a significant reduction on the net DOC release when shading was maintained for 6 days compared to only 2 days of shading. Based on published and unpublished results we also estimate the global net DOC production by marine macrophytes. The estimated global net DOC flux, and hence export, from marine macrophyte is about 0.197 ± 0.015 Pg C yr−1 or 0.212 ± 0.016 Pg C yr−1 depending if net DOC flux by seagrass meadows was estimated by taking into account the low or high global seagrass area, respectively.

  19. pH-Dependent biodegradable silica nanotubes derived from Gd(OH)3 nanorods and their potential for oral drug delivery and MR imaging.

    Science.gov (United States)

    Hu, Kuo-Wei; Hsu, Kang-Che; Yeh, Chen-Sheng

    2010-09-01

    We report a pH dependence of degradable silica nanotubes, which dissolved to the biodegradation product monosilicic acid, Si(OH)(4). The silica nanotubes, potentially acting as oral-based administration carriers, were resistant to dissolution in the extreme acidic condition of pH 1, but degraded quickly at pH 8, and the degradation rate can be tuned by tailoring the thickness of silica nanotubes with thicker nanotubes dissolving more slowly. Because Gd(OH)(3) nanorods were used as templates, the silica nanotubes could be further developed as MR imaging contrast agents as well as drugs carriers. The released Gd(3+) ions resulting from the etching of Gd(OH)(3) nanorods were chelated by the pre-modified DOTA, yielding Gd-DOTA complexes grafted onto silica nanotubes. The Gd-DOTA grafted silica nanotubes loaded with doxorubicin revealed enhanced T(1) imaging contrast and anticancer activity.

  20. Methane Flux

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Methane (CH4) flux is the net rate of methane exchange between an ecosystem and the atmosphere. Data of this variable were generated by the USGS LandCarbon project...

  1. Fractals of Silica Aggregates

    Institute of Scientific and Technical Information of China (English)

    ZhinhongLi; DongWu; Yuhansun; JunWang; YiLiu; BaozhongDong; Zhinhong

    2001-01-01

    Silica aggregates were prepared by base-catalyzed hydrolysis and condensation of alkoxides in alcohol.Polyethylene glycol(PEG) was used as organic modifier.The sols were characterized using Small Angle X-ray Scattering (SAXS) with synchrotron radiation as X-ray source.The structure evolution during the sol-gel process was determined and described in terms of the fractal geometry.As-produced silica aggregates were found to be mass fractals.The fractl dimensions spanned the regime 2.1-2.6 corresponding to more branched and compact structures.Both RLCA and Eden models dominated the kinetic growth under base-catalyzed condition.

  2. Silica reinforced triblock copolymer gels

    DEFF Research Database (Denmark)

    Theunissen, E.; Overbergh, N.; Reynaers, H.

    2004-01-01

    The effect of silica and polymer coated silica particles as reinforcing agents on the structural and mechanical properties of polystyrene-poly(ethylene/butylene)-polystyrene (PS-PEB-PS) triblock gel has been investigated. Different types of chemically modified silica have been compared in order...... a viscoclastic rubber to a plastic fluid and from a plastic fluid to a viscoelastic liquid are shifted to more elevated temperatures when silica is added to the triblock copolymer gel. (C) 2004 Elsevier Ltd. All rights reserved....

  3. Implications for oxygen, nutrient fluxes and denitrification rates during the early stage of sediment colonisation by the polychaete Nereis spp. in four estuaries

    Science.gov (United States)

    Nizzoli, Daniele; Bartoli, Marco; Cooper, Martin; Welsh, David T.; Underwood, Graham J. C.; Viaroli, Pierluigi

    2007-10-01

    In this work, bioturbation effects by the polychaete Nereis spp. on oxygen demand, denitrification and solute fluxes in four European coastal areas (Goro lagoon in Italy, Tagus estuary in Portugal, Colne estuary in England and Tjärnö bay in Sweden) are compared. The studied areas are very heterogeneous with respect to tidal regimes, primary producers communities, sediment composition and organic matter content and nutrient concentrations in the water column. At each site, with the same methodological approach, undisturbed sediment cores and cores with different numbers of polychaetes added were incubated in the dark. Oxygen, inorganic nutrients (NH 4+, NO 3-, Dissolved Reactive Silica-SiO 2 and Soluble Reactive Phosphorous-SRP) fluxes and coupled-uncoupled denitrification rates were quantified on the same set of cores. Nereis bioturbation had a considerable effect on biogeochemical processes and, at all sites, resulted in an immediate stimulation (from 1.5- to 4-fold higher) of oxygen and ammonium fluxes between the sediment and the water column; on the contrary bioturbation had site specific effects on reactive silica and phosphorus fluxes. Bioturbation also stimulated denitrification of water column nitrate ( Dw, from 1.3 to 3 times higher than in control sediments); this process removed a major fraction (>50%) of the nitrogen lost through denitrification. Overall, the strong relationship between benthic macrofauna activity and sediment biogeochemistry is confirmed by this study. Comparison of the relative stimulation of processes in different geographical areas reveals that the degree by which processes and fluxes (intensity and direction) are affected are site specific and influenced by initial macrofauna densities and sediment and water chemistry.

  4. Preparation of Methylene Blue-Silica Composite Microcapsules

    Energy Technology Data Exchange (ETDEWEB)

    Ono, Hideo. [Nihon Millipore Corp., Yamagata (Japan); Takahashi, Koji. [Yamagata University, Yamagata (Japan). Department of Materials Science and Engineering

    1999-06-01

    Silica microcapsules comprising methylene blue (MB-SiO{sub 2}) of mean diameter 4.0 {mu}m were prepared by solgel and water-in-oil emulsion techniques where water pools are use as microreactors in which methylene blue is dissolved at a high water to surfactant molar ratio. It is confirmed that the cationic methylene blue is incorporated in the silica microcapsule wall during hydrolysis and condensation of tetraethoxysilane. Fixation of methylene blue in the silica wall is examined by passing water or acetic acid aq. soln. (pH 2-4) through a cartridge in which MB-SiO{sub 2} is packed and then measuring the fractions using UV-VIS analysis. The elution behavior is affected drastically by the pH value of the eluent. Methylene blue tends to stay in the wall when the pH value of eluent is above the isoelectric point (IEP) of the silica microcapsules. However, release of methylene blue cation occurs when it is below the IEP. These results reveal that coulomb interaction has an important role to fix methylene blue in the silica microcapsule. (author)

  5. Thin supported silica membranes

    NARCIS (Netherlands)

    Zivkovic, Tijana

    2007-01-01

    This thesis discusses several transport-related aspects relevant for the application of thin supported silica membranes for gas separation and nanofiltration. The influence of support geometry on overall membrane performance is investigated. Planar (i.e., flat plate), tubular, and multichannel suppo

  6. Waste Water for Power Generation via Energy Efficient Selective Silica Separations.

    Energy Technology Data Exchange (ETDEWEB)

    Nenoff, Tina M.; Brady, Patrick Vane.; Sasan, Koroush; Paap, Scott M; Heimer, Brandon Walter; Krumhansl, J.; Howe, K.; Stoll, Z.; Stomp, J.

    2017-09-01

    Silica is ubiquitous in produced and industrial waters, and plays a major disruptive role in water recycle. Herein we have investigated the use of mixed oxides for the removal of silica from these waters, and their incorporation into a low cost and low energy water purification process. High selectivity hydrotalcite (HTC, (Mg 6 Al 2 (OH) 16 (CO 3 )*4H 2 O)), is combined in series with high surface area active alumina (AA, (Al 2 O 3 )) as the dissolved silica removal media. Batch test results indicated that combined HTC/AA is a more effective method for removing silica from industrial cooling tower wasters (CTW) than using HTC or AA separately. The silica uptake via ion exchange on the mixed oxides was confirmed by Fourier transform infrared (FTIR), and Energy dispersive spectroscopy (EDS). Furthermore, HTC/AA effectively removes silica from CTW even in the presence of large concentrations of competing anions, such as Cl - , NO 3 - HCO 3 - , CO 3 2- and SO 4 2- . Similar to batch tests, Single Path Flow Through (SPFT) tests with sequential HTC/AA column filtration has very high silica removal too. Technoeconomic Analysis (TEA) was simultaneously performed for cost comparisons to existing silica removal technologies.

  7. Dissolution-rate enhancement of fenofibrate by adsorption onto silica using supercritical carbon dioxide.

    Science.gov (United States)

    Sanganwar, Ganesh P; Gupta, Ram B

    2008-08-06

    Dissolution rate of a poorly water-soluble drug, fenofibrate, is increased by adsorbing the drug onto silica. The adsorption is achieved by first dissolving the drug in supercritical carbon dioxide and then depressurizing the solution onto silica. Loadings of up to 27.5 wt.% drug onto silica are obtained. Since solvents are not used in the loading process, the fenofibrate/silica formulation is free of any residual solvent, and carbon dioxide is freely removed upon depressurization. The formulation is characterized using infrared spectroscopy, ultraviolet spectroscopy, X-ray diffraction, differential scanning calorimetry and scanning electron microscopy. Based on in vitro dissolution study, a significant increase in the dissolution rate (approximately 80% drug release in 20 min) of drug-silica formulation is observed as compared to micronized fenofibrate (approximately 20% drug release in 20 min), which can be attributed to increase in the surface area and decrease in the crystallinity of drug after adsorption onto silica. Two different formulations are compared: (A) amorphous fenofibrate/silica and (B) slightly crystalline fenofibrate/silica. The second formulation is found to be more stable on storage.

  8. Rayleigh scattering by aqueous colloidal silica as a cause for the blue color of hydrothermal water

    Science.gov (United States)

    Ohsawa, Shinji; Kawamura, Takao; Takamatsu, Nobuki; Yusa, Yuki

    2002-03-01

    Thermal waters in hydrothermal ponds, bathing pools and the brines of geothermal electric power plants commonly have a characteristic blue color. Although many researchers have assumed that the blue color is due to a colloidal suspension and/or absorption by dissolved ferrous iron or by water itself, there has been no specific effort to identify the physical nature of this phenomenon. We have tested, in synthetic and natural solutions, whether aqueous colloidal silica is responsible for the blue color. Aqueous colloidal silica is formed by silica polymerization in thermal waters of the neutral-chloride type which contain initially monomeric silica in concentrations up to three times above the solubilities of amorphous silica. The hue of the blue thermal waters in the pools tested agrees with that of a synthesized colloidal silica solution. Grain-size analyses of aqueous colloidal silica in the blue-colored thermal waters demonstrate that the color is caused by Rayleigh scattering from aqueous colloidal silica particles with diameters (0.1-0.45 μm) smaller than the wavelengths of visible radiation.

  9. The Measurement of Dissolved Oxygen

    Science.gov (United States)

    Thistlethwayte, D.; And Others

    1974-01-01

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

  10. Aniline incorporated silica nanobubbles

    Indian Academy of Sciences (India)

    M J Rosemary; V Suryanarayanan; Ian Maclaren; T Pradeep

    2006-09-01

    We report the synthesis of stearate functionalized nanobubbles of SiO2 with a few aniline molecules inside, represented as C6H5NH2@SiO2@stearate, exhibiting fluorescence with red-shifted emission. Stearic acid functionalization allows the materials to be handled just as free molecules, for dissolution, precipitation, storage etc. The methodology adopted involves adsorption of aniline on the surface of gold nanoparticles with subsequent growth of a silica shell through monolayers, followed by the selective removal of the metal core either using sodium cyanide or by a new reaction involving halocarbons. The material is stable and can be stored for extended periods without loss of fluorescence. Spectroscopic and voltammetric properties of the system were studied in order to understand the interaction of aniline with the shell as well as the monolayer, whilst transmission electron microscopy has been used to study the silica shell.

  11. Fluvial filtering of land-to-ocean fluxes: from natural Holocene variations to Anthropocene

    Science.gov (United States)

    Meybeck, Michel; Vörösmarty, Charles

    2005-02-01

    The evolution of river systems and their related fluxes is considered at various time scales: ( i) over the last 18 000 years, under climatic variability control, ( ii) over the last 50 to 200 years (Anthropocene) due to direct human impacts. Natural Holocene variations in time and space depend on ( i) land-to-ocean connections (endorheism, glacial cover, exposure of continental shelf); ( ii) types of natural fluvial filters (e.g., wetlands, lakes, floodplains, estuaries). Anthropocene changes concern ( i) land-ocean connection (e.g., partial to total runoff reduction resulting from water management), ( ii) modification and removal of natural filters, ( iii) creation of new filters, particularly irrigated fields and reservoirs, ( iv) acceleration and/or development of material sources from human activities. The total river basin area directly affected by human activities is of the same order of magnitude ( >40 Mkm) as the total area affected over the last 18 000 years. A tentative analysis of 38 major river systems totaling 55 Mkm is proposed for several criteria: ( i) trajectories of Holocene evolution, ( ii) occurrence of natural fluvial filters, ( iii) present-day fluvial filters: most river basins are unique. Riverine fluxes per unit area are characterized by hot spots that exceed the world average by one order of magnitude. At the Anthropocene (i.e., since 1950), many riverine fluxes have globally increased (sodium, chloride, sulfate, nitrogen, phosphorous, heavy metals), others are stable (calcium, bicarbonate, sediments) or likely to decrease (dissolved silica). Future trajectories of river fluxes will depend on the balance between increased sources of material (e.g., soil erosion, pollution, fertilization), water abstraction for irrigation and the modification of fluvial filters, particularly the occurrence of reservoirs that already intercept half of the water and store at least 30% of river sediment fluxes. In some river systems, retention actually

  12. MOUTH DISSOLVING TABLET: AN OVERVIEW

    Directory of Open Access Journals (Sweden)

    Kulkarni S. D.

    2011-04-01

    Full Text Available Mouth dissolving Tablets disintegrate and/or dissolve rapidly in the saliva without the need for water. Some tablets are designed to dissolve in saliva extremely fast, within a few seconds, and are true fast-dissolving tablets. Others contain agents to enhance the rate of tablet disintegration in the oral cavity, and are more appropriately termed fast-disintegrating tablets, as they may take up to a minute to completely disintegrate. Mouth or Fast dissolving tablets have been formulated for pediatric, geriatric and bedridden patients and in the many elderly persons will have difficulties in taking conventional oral dosage forms because of hand tremors and dysphagia. The technologies used for manufacturing fast-dissolving tablets are freeze-drying, spray-drying, molding, sublimation, sugar-based excipients, compression, and disintegration addition. As a result of increased life expectancy, the elderly constitute a large portion of the worldwide population today. These people eventually will experience deterioration of their physiological and physical abilities.

  13. The Influence of Silica on the Reactivity of Iron Towards Chlorinated Hydrocarbons

    Science.gov (United States)

    Kohn, T.; Himmelheber, D. W.; Vikesland, P. J.; Fairbrother, D.; Roberts, A.

    2001-12-01

    Previous work has illustrated that dissolved silica present in groundwater can adsorb onto the iron media of a permeable reactive barrier. To date, little is known about the effect of adsorbed silica on the reactivity of iron towards chlorinated contaminants. Silica is a known corrosion inhibitor, and therefore silica sorption may affect the reactivity of cast iron towards redox-active species such as chlorinated ethanes. To determine the effect of silica sorption on iron reactivity towards chlorinated hydrocarbons, it is necessary to examine contaminant degradation rates under conditions where silica adsorption has been carefully accounted for. In this study we couple measurements of chlorinated hydrocarbon (CHC) (either trichloroethane (TCA) or trichloroethene) degradation rates with measurements of silica surface content. Both batch and columns studies were conducted as part of this effort. Batch studies were performed using electrolytic iron powder or iron coupons (1 cm2) in solutions containing sodium metasilicate and TCA. To evaluate the potential long-term effect of silica sorption, columns packed with untreated sieved Master Builder's iron were fed with simulated groundwater containing low levels of sodium metasilicate and chlorinated hydrocarbons (CHCs). Batch studies showed that at pH 8.5 the rate of TCA degradation decreased significantly with increasing silica concentration. Silica concentrations of 50 mg/L or more led to a two-fold decrease in the reaction rate, and a shift in the distribution of the reaction products towards less chlorinated compounds was observed. This shift could also be discerned at pH 7.5, even though the overall reaction rates were unaffected by the presence of silica. We ascribe the loss of reactivity at pH 8.5 but not at pH 7.5 to the fact that silica adsorbs onto iron more readily at higher pH. A decrease in iron reactivity towards CHCs was also observed in column experiments. Addition of silica to the feed resulted in

  14. Diatomite releases silica during spirit filtration.

    Science.gov (United States)

    Gómez, J; Gil, M L A; de la Rosa-Fox, N; Alguacil, M

    2014-09-15

    The purpose of this study was to ascertain whether diatomite is an inert filter aid during spirit filtration. Surely, any compound with a negative effect on the spirit composition or the consumer's health could be dissolved. In this study different diatomites were treated with 36% vol. ethanol/water mixtures and the amounts and structures of the extracted compounds were determined. Furthermore, Brandy de Jerez was diatomite- and membrane-filtered at different temperatures and the silicon content was analysed. It was found that up to 0.36% by weight of diatomite dissolved in the aqueous ethanol and amorphous silica, in the form of hollow spherical microparticles, was the most abundant component. Silicon concentrations in Brandy de Jerez increased by up to 163.0% after contact with diatomite and these changes were more marked for calcined diatomite. In contrast, reductions of more than 30% in silicon concentrations were achieved after membrane filtration at low temperatures. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Online dissolved methane and total dissolved sulfide measurement in sewers.

    Science.gov (United States)

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

    2015-01-01

    Recent studies using short-term manual sampling of sewage followed by off-line laboratory gas chromatography (GC) measurement have shown that a substantial amount of dissolved methane is produced in sewer systems. However, only limited data has been acquired to date due to the low frequency and short span of this method, which cannot capture the dynamic variations of in-sewer dissolved methane concentrations. In this study, a newly developed online measuring device was used to monitor dissolved methane concentrations at the end of a rising main sewer network, over two periods of three weeks each, in summer and early winter, respectively. This device uses an online gas-phase methane sensor to measure methane under equilibrium conditions after being stripped from the sewage. The data are then converted to liquid-phase methane concentrations according to Henry's Law. The detection limit and range are suitable for sewer application and can be adjusted by varying the ratio of liquid-to-gas phase volume settings. The measurement presented good linearity (R² > 0.95) during field application, when compared to off-line measurements. The overall data set showed a wide variation in dissolved methane concentration of 5-15 mg/L in summer and 3.5-12 mg/L in winter, resulting in a significant average daily production of 24.6 and 19.0 kg-CH₄/d, respectively, from the network with a daily average sewage flow of 2840 m³/day. The dissolved methane concentration demonstrated a clear diurnal pattern coinciding with flow and sulfide fluctuation, implying a relationship with the wastewater hydraulic retention time (HRT). The total dissolved sulfide (TDS) concentration in sewers can be determined simultaneously with the same principle.

  16. Preparation of stable silica surfaces for surface forces measurement

    Science.gov (United States)

    Ren, Huai-Yin; Mizukami, Masashi; Kurihara, Kazue

    2017-09-01

    A surface forces apparatus (SFA) measures the forces between two surfaces as a function of the surface separation distance. It is regarded as an essential tool for studying the interactions between two surfaces. However, sample surfaces used for the conventional SFA measurements have been mostly limited to thin (ca. 2-3 μm) micas, which are coated with silver layers (ca. 50 nm) on their back, due to the requirement of the distance determination by transmission mode optical interferometry called FECO (fringes of equal chromatic order). The FECO method has the advantage of determining the absolute distance, so it should be important to increase the availability of samples other than mica, which is chemically nonreactive and also requires significant efforts for cleaving. Recently, silica sheets have been occasionally used in place of mica, which increases the possibility of surface modification. However, in this case, the silver layer side of the sheet is glued on a cylindrical quartz disc using epoxy resin, which is not stable in organic solvents and can be easily swollen or dissolved. The preparation of substrates more stable under severe conditions, such as in organic solvents, is necessary for extending application of the measurement. In this study, we report an easy method for preparing stable silica layers of ca. 2 μm in thickness deposited on gold layers (41 nm)/silica discs by sputtering, then annealed to enhance the stability. The obtained silica layers were stable and showed no swelling in organic solvents such as ethanol and toluene.

  17. Iron Oxide Silica Derived from Sol-Gel Synthesis

    Directory of Open Access Journals (Sweden)

    João Carlos Diniz da Costa

    2011-02-01

    Full Text Available In this work we investigate the effect of iron oxide embedded in silica matrices as a function of Fe/Si molar ratio and sol pH. To achieve homogeneous dispersion of iron oxide particles, iron nitrate nonahydrate was dissolved in hydrogen peroxide and was mixed with tetraethyl orthosilicate and ethanol in a sol-gel synthesis method. Increasing the calcination temperature led to a reduction in surface area, although the average pore radius remained almost constant at about 10 Å, independent of the Fe/Si molar ratio or sol pH. Hence, the densification of the matrix was accompanied by similar reduction in pore volume. However, calcination at 700 °C resulted in samples with similar surface area though the iron oxide content increased from 5% to 50% Fe/Si molar ratio. As metal oxide particles have lower surface area than polymeric silica structures, these results strongly suggest that the iron oxides opposed the silica structure collapse. The effect of sol pH was found to be less significant than the Fe/Si molar ratio in the formation of molecular sieve structures derived from iron oxide silica.

  18. Hydrothermal stability of microporous silica and niobia-silica membranes

    NARCIS (Netherlands)

    Boffa, V.; Blank, David H.A.; ten Elshof, Johan E.

    2008-01-01

    The hydrothermal stability of microporous niobia–silica membranes was investigated and compared with silica membranes. The membranes were exposed to hydrothermal conditions at 150 and 200 °C for 70 h. The change of pore structure before and after exposure to steam was probed by single-gas permeation

  19. Synthesis and separation performance of silicalite-1 membranes on silica tubes

    Institute of Scientific and Technical Information of China (English)

    CHEN HongLiang; LI YanShuo; ZHU GuangQi; YANG WeiShen

    2009-01-01

    High-performance silicalite-1 membranes were synthesized on silica tubes by in-situ hydrothermal synthesis. By using the "solution-filling (SF)" method, the average flux of membranes with the SF method was improved by about 25% compared to that of the membranes without using the SF method; the flux and the separation factor of the membranes prepared with the SF method for an ethanol/water mixture at 60℃ were 0.99 kg/(m2.h) and 73, respectively. It was found that the membranes synthesized on silica tubes exhibited high thermal stability and high reproducibility, and the relatively standard deviations (R.S.D.) of the average flux and separation factor were only 9.6% and 5.6%, respectively, which suggests that the silica support is more suitable than other kinds of supports for preparing high-performance silicalite-1 membranes.

  20. Synthesis and separation performance of silicalite-1 membranes on silica tubes

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    High-performance silicalite-1 membranes were synthesized on silica tubes by in-situ hydrothermal synthesis. By using the "solution-filling (SF)" method, the average flux of membranes with the SF method was improved by about 25% compared to that of the membranes without using the SF method; the flux and the separation factor of the membranes prepared with the SF method for an ethanol/water mixture at 60 ℃ were 0.99 kg/(m2·h) and 73, respectively. It was found that the membranes synthesized on silica tubes exhibited high thermal stability and high reproducibility, and the relatively standard deviations (R.S.D.) of the average flux and separation factor were only 9.6% and 5.6%, respectively, which suggests that the silica support is more suitable than other kinds of supports for preparing high-performance silicalite-1 membranes.

  1. Silica Micro Encapsulation

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, P.; Whitbread-Jordan, M. [KEECO (United Kingdom)

    2001-04-01

    The article explains how Silica Micro Encapsulation (SME) water treatment technology may be transferred from metal mining to coal mining operations. KEECO has been developing a unique solution for treating acid rock drainage in the metal sulphide mining sector and following trials in metal mining operations (described in the article), is preparing to transfer the technology to the coal industry. SME technology comprises metal precipitation and encapsulation accomplished with proprietary chemical, KB-1, and a group of patented chemical dosing systems, the K-series, to dose KB-1 into contaminated liquid wastes as a dry powder. 4 figs., 4 tabs.

  2. ZBLAN, Silica Fiber Comparison

    Science.gov (United States)

    1998-01-01

    This graph depicts the increased signal quality possible with optical fibers made from ZBLAN, a family of heavy-metal fluoride glasses (fluorine combined zirconium, barium, lanthanum, aluminum, and sodium) as compared to silica fibers. NASA is conducting research on pulling ZBLAN fibers in the low-g environment of space to prevent crystallization that limits ZBLAN's usefulness in optical fiber-based communications. In the graph, a line closer to the black theoretical maximum line is better. Photo credit: NASA/Marshall Space Flight Center

  3. Critical flux determination by flux-stepping

    DEFF Research Database (Denmark)

    Beier, Søren; Jonsson, Gunnar Eigil

    2010-01-01

    In membrane filtration related scientific literature, often step-by-step determined critical fluxes are reported. Using a dynamic microfiltration device, it is shown that critical fluxes determined from two different flux-stepping methods are dependent upon operational parameters such as step......, such values are more or less useless in itself as critical flux predictors, and constant flux verification experiments have to be conducted to check if the determined critical fluxes call predict sustainable flux regimes. However, it is shown that using the step-by-step predicted critical fluxes as start...

  4. Explosives Dissolved from Unexploded Ordnance

    Science.gov (United States)

    2011-10-01

    moisture content) also result in higher corrosion rates especially if the moisture has high dissolved oxygen content ( Manahan 1994). Corrosion of metal is...R. 1993. Handbook of hydrology. New York: McGraw-Hill, Inc. Manahan , S. 1994. Environmental Chemistry. Boca Raton, FL: Lewis Publishers. McCormick

  5. Dissolving pulp from jute stick.

    Science.gov (United States)

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

    2015-01-22

    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 α-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% α-cellulose and 89% brightness after D0EpD1EpD1 bleaching. The produced dissolving pulp can be used in rayon production. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Release of dissolved carbohydrates by

    NARCIS (Netherlands)

    Van Oostende, N.; Moerdijk-Poortvliet, T.C.W.; Boschker, H.T.S.; Vyverman, W.; Sabbe, K.

    2013-01-01

    The coccolithophore Emiliania huxleyi plays a pivotal role in the marine carbon cycle. However, we have only limited understanding of how its life cycle and bacterial interactions affect the production and composition of dissolved extracellular organic carbon and its transfer to the particu

  7. Silaffins in Silica Biomineralization and Biomimetic Silica Precipitation

    Directory of Open Access Journals (Sweden)

    Carolin C. Lechner

    2015-08-01

    Full Text Available Biomineralization processes leading to complex solid structures of inorganic material in biological systems are constantly gaining attention in biotechnology and biomedical research. An outstanding example for biomineral morphogenesis is the formation of highly elaborate, nano-patterned silica shells by diatoms. Among the organic macromolecules that have been closely linked to the tightly controlled precipitation of silica in diatoms, silaffins play an extraordinary role. These peptides typically occur as complex posttranslationally modified variants and are directly involved in the silica deposition process in diatoms. However, even in vitro silaffin-based peptides alone, with and without posttranslational modifications, can efficiently mediate biomimetic silica precipitation leading to silica material with different properties as well as with encapsulated cargo molecules of a large size range. In this review, the biomineralization process of silica in diatoms is summarized with a specific focus on silaffins and their in vitro silica precipitation properties. Applications in the area of bio- and nanotechnology as well as in diagnostics and therapy are discussed.

  8. Erosion patterns on dissolving blocks

    Science.gov (United States)

    Courrech du Pont, Sylvain; Cohen, Caroline; Derr, Julien; Berhanu, Michael

    2016-04-01

    Patterns in nature are shaped under water flows and wind action, and the understanding of their morphodynamics goes through the identification of the physical mechanisms at play. When a dissoluble body is exposed to a water flow, typical patterns with scallop-like shapes may appear [1,2]. These shapes are observed on the walls of underground rivers or icebergs. We experimentally study the erosion of dissolving bodies made of salt, caramel or ice into water solutions without external flow. The dissolving mixture, which is created at the solid/liquid interface, undergoes a buoyancy-driven instability comparable to a Rayleigh-Bénard instability so that the dissolving front destabilizes into filaments. This mechanism yields to spatial variations of solute concentration and to differential dissolution of the dissolving block. We first observe longitudinal stripes with a well defined wavelength, which evolve towards chevrons and scallops that interact and move again the dissolving current. Thanks to a careful analysis of the competing physical mechanisms, we propose scaling laws, which account for the characteristic lengths and times of the early regime in experiments. The long-term evolution of patterns is understood qualitatively. A close related mechanism has been proposed to explain structures observed on the basal boundary of ice cover on brakish lakes [3] and we suggest that our experiments are analogous and explain the scallop-like patterns on iceberg walls. [1] P. Meakin and B. Jamtveit, Geological pattern formation by growth and dissolution in aqueous systems, Proc. R. Soc. A 466, 659-694 (2010). [2] P.N. Blumberg and R.L. Curl, Experimental and theoretical studies of dissolution roughness, J. Fluid Mech. 65, 735-751 (1974). [3] L. Solari and G. Parker, Morphodynamic modelling of the basal boundary of ice cover on brakish lakes, J.G.R. 118, 1432-1442 (2013).

  9. A Thermodynamic Consideration on the Mechanism of Ultrasensitive Moisture Sensing by Amorphous Silica

    Science.gov (United States)

    Tsukahara, Y.; Tsuji, T.; Oizumi, T.; Akao, S.; Takeda, N.; Yamanaka, K.

    2017-07-01

    We detected the change in the phase velocity of surface acoustic waves propagating along the amorphous silica layer on a spherical single-crystal quartz due to the very small amount of moisture at less than 1 μmol{\\cdot } mol^{-1} in the ambient N2 gas. This was made possible for the first time because this system, called a ball SAW moisture sensor, was extremely sensitive. The measured phase velocity changed as a function of moisture density and temperature and was fitted strikingly well with a thermodynamic model assuming that dissociated H+ and OH- dissolved into the amorphous silica layer at room temperature.

  10. Biogenic nanostructured silica

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Silicon is by far the most abundant element in the earth crust and also is an essential element for higher plants, yet its biology and mechanisms in plant tolerance of biotic and abiotic stresses are poorly understood. Based on the molecular mechanisms of the biosilicification in marine organisms such as diatoms and sponges, the cell wall template-mediated self-assembly of nanostructured silica in marine organisms and higher plants as well as the related organic molecules are discussed. Understanding of the templating and structure-directed effects of silicon-processing organic molecules not only offers the clue for synthesizing silicon-based materials, but also helps to recognize the anomaly of silicon in plant biology.

  11. Factors controlling vertical fluxes of prrticles in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, T.M.B.; Ramaswamy, V.; Parthiban, G.; Shankar, R.

    in the mixed layer depth which, in turn, is controlled by the strength of the Findlater Jet and the curl of the wind stress. The increase in biogenic silica fluxes during the late SW monsoon is related to the advection of nutrient-rich water from the Oman...

  12. 21 CFR 582.1711 - Silica aerogel.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam...

  13. 21 CFR 182.1711 - Silica aerogel.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Silica aerogel. 182.1711 Section 182.1711 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam...

  14. 21 CFR 584.700 - Hydrophobic silicas.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Hydrophobic silicas. 584.700 Section 584.700 Food... DRINKING WATER OF ANIMALS Listing of Specific Substances Affirmed as GRAS § 584.700 Hydrophobic silicas. (a) Product. Amorphous fumed hydrophobic silica or precipitated hydrophobic silica (CAS Reg. No....

  15. Tracing natural gas transport into shallow groundwater using dissolved nitrogen and alkane chemistry in Parker County, Texas

    Science.gov (United States)

    Larson, T.; Nicot, J. P.; Mickler, P. J.; Darvari, R.

    2015-12-01

    Dissolved methane in shallow groundwater drives public concern about the safety of hydraulic fracturing. We report dissolved alkane and nitrogen gas concentrations and their stable isotope values (δ13C and δ15N, respectively) from 208 water wells in Parker county, Texas. These data are used to differentiate 'stray' natural gas and low temperature microbial methane, and (2) estimate the ratio of stray gas to groundwater. The ratio of (gas-phase) stray natural gas to groundwater is estimated by correlating dissolved methane and nitrogen concentrations and dissolved nitrogen δ15N values. Our hypothesis is groundwater exposed to high volumes of stray natural gas have high dissolved methane concentrations and low dissolved nitrogen concentrations and δ15N values. Alternatively, groundwater exposed to low volumes of stray gas-phase natural gas have elevated dissolved methane, but the concentration of dissolved nitrogen and its d15N value is atmospheric. A cluster of samples in Parker county have high concentrations of dissolved methane (>10mg/L) with d13Cmethane and alkane ratios (C1/C2+C3) typical of natural gas from the Barnett Shale and the Strawn Formation. Coupling dissolved nitrogen concentrations and δ15N values with these results, we suggest that few of the wells in this cluster preserve large gas to water ratios. Many samples with high dissolved methane concentrations have atmospheric dissolved nitrogen concentrations and δ15N values, providing evidence against high flux natural gas transport into shallow groundwater. These results demonstrate that dissolved nitrogen chemistry, in addition to dissolved alkane and noble gas measurements, may be useful to discern sources of dissolved methane and estimate ratios of stray natural gas-water ratios.

  16. Composition and flux of nurtients transport to the Changjiang Estuary

    Institute of Scientific and Technical Information of China (English)

    ZHANGShen; JIHongbing; YANWeijin; DUANShuiwang

    2003-01-01

    Based on the results of water sample measurements of nutrient concentrations at the Datong Station of Changjiang River from 1998 to 1999,combined with historiceal data of water quality,seasonal variations of nutrient concentrations and nutrient transports are discussed.Tthe following results have been obtained:(1)the fluxes of the nitrate nitrogen,ammonium nitrogen and nitrite nitrogen increased by time0series from 1962 to 1990,even if runoff volume had a little variation;(2)the concentrations and fluxes of the dissolved inorganic nitrogen (DIN)and dissolved inorganic phosphorus (DIP)increased notably with time,but those of th dissolved silicon(DSI)decreased pronouncedly,and (3) the concentrations and fluxes changed synchronously with time between the Datong Station and the Changjiang Estuary.

  17. First flush of dissolved compounds

    DEFF Research Database (Denmark)

    Krebs, P.; Holzer, P.; Huisman, J.L.

    1999-01-01

    In a crude conceptual approach it is commonly assumed that in a combined sewer system the concentration of dissolved compounds is diluted by an increasing flow rate due to rainwater inflow. However, theory of hydraulics suggests that these compounds are influenced by hydrodynamic effects....... It is known that since the wave celerity is higher than the flow velocity of the water, the increase of flow rate induced through rain runoff is recognised earlier at a certain downstream section of the combined sewer than the concentration increase of typical rain-water compounds originating from surface...... wash-off. This description implies that the wave front is formed from the fluid that was present in the sewer before the Bow rare increased, that is the sewage! By means of measurements and numerical simulations, it is shown that this effect may cause a significant impact of dissolved compounds...

  18. Functionalized silica materials for electrocatalysis

    Indian Academy of Sciences (India)

    Vellaichamy Ganesan

    2015-02-01

    Electrocatalysis is an important phenomenon which is utilized in metal–air batteries, fuel cells, electrochemical sensors, etc. To increase the efficiency of the electrocatalytic process and to increase the electrochemical accessibility of the immobilized electrocatalysts, functionalized and non-functionalized mesoporous organo-silica (MCM41-type-materials) are used in this study. These materials possess several suitable properties to be durable catalysts and/or catalyst supports. Owing to the uniform dispersion of electrocatalysts (metal complex and/or metal nanoparticles (NPs)) on the functionalized and non-functionalized silica, an enormous increase in the redox current is observed. Long range channels of silica materials with pore diameter of 15–100 Å allowed metal NPs to accommodate in a specified manner in addition to other catalysts. The usefulness of MCM-41-type silica in increasing the efficiency of electrocatalysisis demonstrated by selecting oxygen, carbon dioxide and nitrite reduction reactions as examples

  19. Silica exposure and systemic vasculitis.

    OpenAIRE

    Mulloy, Karen B

    2003-01-01

    Work in Department of Energy (DOE) facilities has exposed workers to multiple toxic agents leading to acute and chronic diseases. Many exposures were common to numerous work sites. Exposure to crystalline silica was primarily restricted to a few facilities. I present the case of a 63-year-old male who worked in DOE facilities for 30 years as a weapons testing technician. In addition to silica, other workplace exposures included beryllium, various solvents and heavy metals, depleted uranium, a...

  20. Improved Reactivity of Fly Ash-Slag Geopolymer by the Addition of Silica Fume

    Directory of Open Access Journals (Sweden)

    N. K. Lee

    2016-01-01

    Full Text Available This study investigates the improved reactivity of a geopolymer based on a combination of fly ash and blast furnace slag (BFS by the addition of silica fume. The geopolymer was synthesized by activating a mixture of fly ash, BFS, and three different types of silica fume with alkali activator. X-ray diffraction (XRD and inductively coupled plasma-optical emission spectroscopy (ICP-OES were utilized to characterize the reaction. The silicate structure was also analyzed by nuclear magnetic resonance (NMR spectroscopy. From these results, it was found that the replacement of fly ash with the silica fume led to a significant decrease in the Q4(1Al and an increase in the Q4(2Al, Q4(3Al, and Q4(4Al. The Si/Al ratio of the aluminosilicate gel was relatively constant, ranging from 2.0 to 2.6, while the Si/Al ratio of the C-S-H gel increased with the addition of silica fume. Therefore, some of the Al dissolved from the slag contributed to the formation of aluminosilicate gel, and the remnant slag particles mostly participated in the formation of the C-(A-S-H gel with a decrease in the Q2(1Al. The increase in the reactivity of slag caused by the addition of silica fume was attributed to the reaction of the Al in the slag with the silica fume.

  1. Preparation of the methylene blue silica compound microcapsule; Mechirenburushirika fukugo maikuro kapuseru no chosei

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Koji [Yamagata University, Yamagata (Japan); Ono, Hideo

    1999-07-05

    By using methylene blue aqueous solution of the cationy for the dispersed phase of the W/0 emulsion, and using this for hydrolysis of TEOS and reaction field of the degeneracy conjunction, force - methylene blue compound microcapsule of 4.0 {mu}m mean particle sizes was prepared. When the water was supplied, though there was elution behavior of the methylene blue from this microcapsule in the condition that the methylene blue was fixed in the silica microcapsule without completely dissolving, the elution amount of methylene blue increased eluate isoelectric point silica, and the pH dependence was shown. Therefore, a part of methylene blue in dispersed phase combines with the silica in Coulomb force like during hydrolysis and degeneracy conjunction of TEOS, and it is fixed in the silica microcapsule resistant, and by the consistency of pH of the eluate, it is meanwhile regarded out for acidic as a dissolution of the methylene blue of the isoelectric point of the silica from the silica microcapsule. (translated by NEDO)

  2. The role of alkalinity generation in controlling the fluxes of CO

    NARCIS (Netherlands)

    Faber, P.A.; Kessler, A.J.; Bull, J.K.; McKelvie, I.D.; Meysman, F.J.R.; Cook, P.L.M.

    2012-01-01

    Dissolved inorganic carbon (DIC), gaseous CO2 and alkalinity fluxes from intertidal sediments were investigated during periods of exposure and inundation, using laboratory core incubations, previously published field data and reactive transport model simulations. In the incubations and previous fiel

  3. Physical controls of oxygen fluxes at pelagic and benthic oxyclines in a lake

    DEFF Research Database (Denmark)

    Kreling, Julika; Bravidor, Jenny; McGinnis, Daniel F.;

    2014-01-01

    from the epilimnion; chemical oxygen consumption associated with the upward flux of reduced substances is negligible. Our findings indicate that under such conditions, dissolved oxygen consumption and therewith mineralization within the oxycline can be comparable with the corresponding rates occurring...

  4. Flux-P: Automating Metabolic Flux Analysis

    OpenAIRE

    Ebert, Birgitta E.; Anna-Lena Lamprecht; Bernhard Steffen; Blank, Lars M.

    2012-01-01

    Quantitative knowledge of intracellular fluxes in metabolic networks is invaluable for inferring metabolic system behavior and the design principles of biological systems. However, intracellular reaction rates can not often be calculated directly but have to be estimated; for instance, via 13C-based metabolic flux analysis, a model-based interpretation of stable carbon isotope patterns in intermediates of metabolism. Existing software such as FiatFlux, OpenFLUX or 13CFLUX supports experts in ...

  5. Dynamics of dissolved inorganic carbon and aquatic metabolism in the Tana River basin, Kenya

    NARCIS (Netherlands)

    Tamooh, F.; Borges, A.V.; Meysman, F.J.R.; Van Den Meersche, K.; Dehairs, F.; Merckx, R.; Bouillon, S.

    2013-01-01

    A basin-wide study was conducted in the Tana River basin (Kenya) in February 2008 (dry season), September–November 2009 (wet season) and June–July 2010 (end of the wet season) to assess the dynamics and sources of dissolved inorganic carbon (DIC) as well as to quantify CO2 fluxes, community respirat

  6. Silica research in Glasgow

    CERN Document Server

    Barr, B W; Casey, M M; Clubley, D; Crooks, D R M; Danzmann, K; Elliffe, E J; Gossler, S; Grant, A; Grote, H; Heptonstall, A; Hough, J; Jennrich, O; Lück, H B; McIntosh, S A; Newton, G P; Palmer, D A; Plissi, M V; Robertson, D I; Robertson, N A; Rowan, S; Skeldon, K D; Sneddon, P; Strain, K A; Torrie, C I; Ward, H; Willems, P A; Willke, B; Winkler, W

    2002-01-01

    The Glasgow group is involved in the construction of the GEO600 interferometer as well as in R and D activity on technology for advanced gravitational wave detectors. GEO600 will be the first GW detector using quasi-monolithic silica suspensions in order to decrease thermal noise significantly with respect to steel wire suspensions. The results concerning GEO600 suspension mounting and performance will be shown in the first section. Section 2 is devoted to the present results from the direct measurement of thermal noise in mirrors mounted in the 10 m interferometer in Glasgow which has a sensitivity limit of 4 x 10 sup - sup 1 sup 9 m Hz sup - sup 1 sup / sup 2 above 1 kHz. Section 3 presents results on the measurements of coating losses. R and D activity has been carried out to understand better how thermal noise in the suspensions affects the detector sensitivity, and in section 4 a discussion on the non-linear thermoelastic effect is presented.

  7. Dust inputs and bacteria influence dissolved organic matter in clear alpine lakes.

    Science.gov (United States)

    Mladenov, N; Sommaruga, R; Morales-Baquero, R; Laurion, I; Camarero, L; Diéguez, M C; Camacho, A; Delgado, A; Torres, O; Chen, Z; Felip, M; Reche, I

    2011-01-01

    Remote lakes are usually unaffected by direct human influence, yet they receive inputs of atmospheric pollutants, dust, and other aerosols, both inorganic and organic. In remote, alpine lakes, these atmospheric inputs may influence the pool of dissolved organic matter, a critical constituent for the biogeochemical functioning of aquatic ecosystems. Here, to assess this influence, we evaluate factors related to aerosol deposition, climate, catchment properties, and microbial constituents in a global dataset of 86 alpine and polar lakes. We show significant latitudinal trends in dissolved organic matter quantity and quality, and uncover new evidence that this geographic pattern is influenced by dust deposition, flux of incident ultraviolet radiation, and bacterial processing. Our results suggest that changes in land use and climate that result in increasing dust flux, ultraviolet radiation, and air temperature may act to shift the optical quality of dissolved organic matter in clear, alpine lakes.

  8. Uptake of CO2 in the Pelagic Ocean by the Biological Pump; the Global Flux and the Regional Variability

    Science.gov (United States)

    Honjo, S.; Francois, R. H.; Manganini, S. J.; Eglinton, T. I.

    2010-12-01

    Ocean occupies about 80% of the present world pelagic ocean between the two major oceanographic fronts, the North Pacific Polar Front and the Antarctic Polar Front, and the Silica Ocean is found on the polar sides of these fronts. The location of these biogeochemical fronts shift with global climate changes. The total global annual fluxes of Fm/bCorg, Fm/bCinorg, and Fm/bSibio at m/b calculated by parameterizations of the export flux data from 134 stations are surprisingly similar; 36.2, 33.8, and 34.6 teramol yr-1 (120, 112, and 114 mmol m-2yr-1), respectively. The global ternary % ratios estimated from 152 TS-trap samples of the three elements are 35:32:33. From our global Fm/bCorg and a published model estimate of the global export production, we estimate the regeneration rate of CO2 through the mesopelagic zone by the biological pump is 441 teramolC yr-1. Based on our global Fm/bCorg and recently estimated global primary production of PIC, 36 to 86 teramolC yr-1 of PIC is assumed to be dissolved within the upper 2 km of the water column.

  9. Mercury in the Lot-Garonne River system (France): Sources, fluxes and anthropogenic component

    OpenAIRE

    Schafer, Jörg; Blanc, Gerard; Audry, S; Cossa, Daniel; Bossy, C.

    2006-01-01

    Dissolved and particulate Hg fluxes in the Lot-Garonne-Gironde fluvial-estuarine system were obtained from observation of daily discharge and suspended particulate matter (SPM) concentrations. In addition to the measurements of the total dissolved ( 0.45 gm), called HgTD and HgTp respectively, the dissolved inorganic Hg species (HgRD) were determined monthly. Geochemical background values for HgTp in sediments and SPM were similar to crustal values and to typic...

  10. PROCESS OF DISSOLVING ZIRCONIUM ALLOYS

    Science.gov (United States)

    Shor, R.S.; Vogler, S.

    1958-01-21

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

  11. Properties of silica fume procured from natural diatomite and its usage in the production of vacuum insulation panels

    Directory of Open Access Journals (Sweden)

    V.P. Selyaev

    2013-11-01

    Full Text Available The article shows the results of the research of silica fume particles procured from diatomite from Atemar deposit by means of separating silicic acid from colloidal dissolved state into the sediment. The objective of the work was to define thermal-physical and structural characteristics of the silica fume. The research included IR-spectrometry, granulometry, thermal gravimetric analysis, X-ray structural analysis, optical microscopy, and small angle X-Ray scattering. As a result of the research, the silica fume was defined to predominantly consist of amorphous silicon dioxide and had the developed pore structure of particles. A large number of nanosized particles and pores decreases heat transmission and increases reactive capability, that gives opportunity of using the powder silica fume as an active agent in dry mixes and concrete composites, as a component of sponge-glass, and as a filler material in vacuum insulation panel.

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

    Science.gov (United States)

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

    2008-06-01

    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 samples. At 2.5 km down plume from the nearest known vent site dissolved Fe concentrations were ˜ 20 nM. This is much higher than would be predicted from a combination of plume dilution and dissolved Fe(II) oxidation rates, but consistent with stabilisation due to the presence of organic Fe complexes and Fe colloids. Using Competitive Ligand Exchange-Cathodic Stripping Voltammetry (CLE-CSV), stabilised dissolved Fe complexes were detected within the dissolved Fe fraction on the edges of one non-buoyant hydrothermal plume with observed ligand concentrations high enough to account for stabilisation of ˜ 4% of the total Fe emitted from the 5° S vent sites. If these results were representative of all hydrothermal systems, submarine venting could provide 12-22% of the global deep-ocean dissolved Fe budget.

  13. Iron persistence in a distal hydrothermal plume supported by dissolved-particulate exchange

    Science.gov (United States)

    Fitzsimmons, Jessica N.; John, Seth G.; Marsay, Christopher M.; Hoffman, Colleen L.; Nicholas, Sarah L.; Toner, Brandy M.; German, Christopher R.; Sherrell, Robert M.

    2017-02-01

    Hydrothermally sourced dissolved metals have been recorded in all ocean basins. In the oceans' largest known hydrothermal plume, extending westwards across the Pacific from the Southern East Pacific Rise, dissolved iron and manganese were shown by the GEOTRACES program to be transported halfway across the Pacific. Here, we report that particulate iron and manganese in the same plume also exceed background concentrations, even 4,000 km from the vent source. Both dissolved and particulate iron deepen by more than 350 m relative to 3He--a non-reactive tracer of hydrothermal input--crossing isopycnals. Manganese shows no similar descent. Individual plume particle analyses indicate that particulate iron occurs within low-density organic matrices, consistent with its slow sinking rate of 5-10 m yr-1. Chemical speciation and isotopic composition analyses reveal that particulate iron consists of Fe(III) oxyhydroxides, whereas dissolved iron consists of nanoparticulate Fe(III) oxyhydroxides and an organically complexed iron phase. The descent of plume-dissolved iron is best explained by reversible exchange onto slowly sinking particles, probably mediated by organic compounds binding iron. We suggest that in ocean regimes with high particulate iron loadings, dissolved iron fluxes may depend on the balance between stabilization in the dissolved phase and the reversibility of exchange onto sinking particles.

  14. Infrared spectra of silica polymorphs

    Science.gov (United States)

    Koike, C.; Noguchi, R.; Chihara, H.; Suto, H.; Ohtaka, O.; Imai, Y.; Matsumoto, T.; Tsuchiyama, A.

    The existence of silica within several debris disks has been suggested. We investigate the annealing conditions of α-cristobalite, and further prepare various types of silica, including α-cristobalite, α-quartz, coesite, stishovite, and fused quartz, which are natural, synthetic or commercial samples. We compare the results to previous studies and find that α-cristobalite synthesized at higher temperature than annealed silica. The interesting result of features similar to those of forsterite should be highlighted, where αcristobalite and coesite showed similar peaks at 16, 33, and 69 μm as forsterite. The 69 μm band for αcristobalite is especially very broad and strong, and shifts largely to a shorter wavelengths under cooling to low temperatures. The band for coesite, however, is very sharp, and shifts only a small amount to longer wavelengths under cooling to low temperatures. The peak positions of 16 and 69-μm band due to α-cristobalite can become index for temperature of silica dust. We discuss the possibility of silica detection around debris disks.

  15. Exposure to crystalline silica in abrasive blasting operations where silica and non-silica abrasives are used.

    Science.gov (United States)

    Radnoff, Diane L; Kutz, Michelle K

    2014-01-01

    Exposure to respirable crystalline silica is a hazard common to many industries in Alberta but particularly so in abrasive blasting. Alberta occupational health and safety legislation requires the consideration of silica substitutes when conducting abrasive blasting, where reasonably practicable. In this study, exposure to crystalline silica during abrasive blasting was evaluated when both silica and non-silica products were used. The crystalline silica content of non-silica abrasives was also measured. The facilities evaluated were preparing metal products for the application of coatings, so the substrate should not have had a significant contribution to worker exposure to crystalline silica. The occupational sampling results indicate that two-thirds of the workers assessed were potentially over-exposed to respirable crystalline silica. About one-third of the measurements over the exposure limit were at the work sites using silica substitutes at the time of the assessment. The use of the silica substitute, by itself, did not appear to have a large effect on the mean airborne exposure levels. There are a number of factors that may contribute to over-exposures, including the isolation of the blasting area, housekeeping, and inappropriate use of respiratory protective equipment. However, the non-silica abrasives themselves also contain silica. Bulk analysis results for non-silica abrasives commercially available in Alberta indicate that many contain crystalline silica above the legislated disclosure limit of 0.1% weight of silica per weight of product (w/w) and this information may not be accurately disclosed on the material safety data sheet for the product. The employer may still have to evaluate the potential for exposure to crystalline silica at their work site, even when silica substitutes are used. Limited tests on recycled non-silica abrasive indicated that the silica content had increased. Further study is required to evaluate the impact of product recycling

  16. Tracing the origin of dissolved silicon transferred from various soil-plant systems towards rivers: a review

    Directory of Open Access Journals (Sweden)

    J.-T. Cornelis

    2011-01-01

    Full Text Available Silicon (Si released as H4SiO4 by weathering of Si-containing solid phases is partly recycled through vegetation before its land-to-rivers transfer. By accumulating in terrestrial plants to a similar extent as some major macronutrients (0.1–10% Si dry weight, Si becomes largely mobile in the soil-plant system. Litter-fall leads to a substantial reactive biogenic silica pool in soil, which contributes to the release of dissolved Si (DSi in soil solution. Understanding the biogeochemical cycle of silicon in surface environments and the DSi export from soils into rivers is crucial given that the marine primary bio-productivity depends on the availability of H4SiO4 for phytoplankton that requires Si. Continental fluxes of DSi seem to be deeply influenced by climate (temperature and runoff as well as soil-vegetation systems. Therefore, continental areas can be characterized by various abilities to transfer DSi from soil-plant systems towards rivers. Here we pay special attention to those processes taking place in soil-plant systems and controlling the Si transfer towards rivers. We aim at identifying relevant geochemical tracers of Si pathways within the soil-plant system to obtain a better understanding of the origin of DSi exported towards rivers. In this review, we compare different soil-plant systems (weathering-unlimited and weathering-limited environments and the variations of the geochemical tracers (Ge/Si ratios and δ30Si in DSi outputs. We recommend the use of biogeochemical tracers in combination with Si mass-balances and detailed physico-chemical characterization of soil-plant systems to allow better insight in the sources and fate of Si in these biogeochemical systems.

  17. Hydrology controls dissolved organic matter (DOM) quality and dynamics

    Science.gov (United States)

    Fasching, Christina; Schelker, Jakob; Ulseth, Amber; Singer, Gabriel; Steniczka, Gertraud; Battin, Tom

    2014-05-01

    Headwater streams are major contributors to carbon cycling. It is therefore of utmost importance to understand the dynamics of dissolved organic matter (DOM) and its drivers in these ecosystems. Here we present data from more than 4,000 individual DOM measurements from Oberer Seebach, a 3rd-order stream draining a largely pristine alpine catchment (Lunz am See, Austria). We determined the concentration of streamwater and hyporheic dissolved organic carbon and a suite of optical properties of DOM based on a diurnal sampling design over almost three years; we also monitored various hydrological and climate parameters over that same time. Optical properties were determined from absorbance measurements and parallel factor analysis (PARAFAC) modelling of Excitation emission matrices. We also estimated DOM export fluxes from Oberer Seebach and the contributions of the various chromophoric and fluorescent components to these exports. Preliminary results suggest that DOM in Oberer Seebach was largely of terrigenous origin throughout the year. However during periods of low discharge autochthonous DOM export increased, indicating freshly produced DOM possibly from benthic algae. Hyphoreic and streamwater DOM composition and its dynamics were tightly coupled in time at baseflow, yet displaying higher variability as discharge increased. Our timeseries studies highlight the relevance of the flow regime on the dynamics, origin and composition of DOM in a headwater stream. We discuss these findings in the context of extreme hydrological events on carbon fluxes.

  18. Silica Aerogel: Synthesis and Applications

    Directory of Open Access Journals (Sweden)

    Jyoti L. Gurav

    2010-01-01

    Full Text Available Silica aerogels have drawn a lot of interest both in science and technology because of their low bulk density (up to 95% of their volume is air, hydrophobicity, low thermal conductivity, high surface area, and optical transparency. Aerogels are synthesized from molecular precursors by sol-gel processing. Special drying techniques must be applied to replace the pore liquid with air while maintaining the solid network. Supercritical drying is most common; however, recently developed methods allow removal of the liquid at atmospheric pressure after chemical modification of the inner surface of the gels, leaving only a porous silica network filled with air. Therefore, by considering the surprising properties of aerogels, the present review addresses synthesis of silica aerogels by the sol-gel method, as well as drying techniques and applications in current industrial development and scientific research.

  19. Synthesis and Characterization of Bimodal Mesoporous Silica

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiaofang; GUO Cuili; WANG Xiaoli; WU Yuanyuan

    2012-01-01

    Mesoporous silica with controllable bimodal pore size distribution was synthesized with cetyltrimethylammonium bromide (CTAB) as chemical template for small mesopores and silica gel as physical template for large mesopores.The structure of synthesized samples were characterized by Fourier transform infrared (FT-IR) spectroscopy,X-ray diffraction (XRD),scanning electron microscopy (SEM),transmission electron microscopy (TEM) and N2 adsorption-desorption measurements.The experimental results show that bimodal mesoporous silica consists of small mesopores of about 3 nm and large mesopores of about 45 nm.The small mesopores which were formed on the external surface and pore walls of the silica gel had similar characters with those of MCM-41,while large mesopores were inherited from parent silica gel material.The pore size distribution of the synthesized silica can be adjusted by changing the relative content of TEOS and silica gel or the feeding sequence of silica gel and NH4OH.

  20. Dissolved gaseous mercury formation and mercury volatilization in intertidal sediments.

    Science.gov (United States)

    Cesário, Rute; Poissant, Laurier; Pilote, Martin; O'Driscoll, Nelson J; Mota, Ana M; Canário, João

    2017-12-15

    Intertidal sediments of Tagus estuary regularly experiences complex redistribution due to tidal forcing, which affects the cycling of mercury (Hg) between sediments and the water column. This study quantifies total mercury (Hg) and methylmercury (MMHg) concentrations and fluxes in a flooded mudflat as well as the effects on water-level fluctuations on the air-surface exchange of mercury. A fast increase in dissolved Hg and MMHg concentrations was observed in overlying water in the first 10min of inundation and corresponded to a decrease in pore waters, suggesting a rapid export of Hg and MMHg from sediments to the water column. Estimations of daily advective transport exceeded the predicted diffusive fluxes by 5 orders of magnitude. A fast increase in dissolved gaseous mercury (DGM) concentration was also observed in the first 20-30min of inundation (maximum of 40pg L(-1)). Suspended particulate matter (SPM) concentrations were inversely correlated with DGM concentrations. Dissolved Hg variation suggested that biotic DGM production in pore waters is a significant factor in addition to the photochemical reduction of Hg. Mercury volatilization (ranged from 1.1 to 3.3ngm(-2)h(-1); average of 2.1ngm(-2)h(-1)) and DGM production exhibited the same pattern with no significant time-lag suggesting a fast release of the produced DGM. These results indicate that Hg sediment/water exchanges in the physical dominated estuaries can be underestimated when the tidal effect is not considered. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Optothermal nonlinearity of silica aerogel

    CERN Document Server

    Braidotti, Maria Chiara; Fleming, Adam; Samuels, Michiel C; Di Falco, Andrea; Conti, Claudio

    2016-01-01

    We report on the characterization of silica aerogel thermal optical nonlinearity, obtained by z-scan technique. The results show that typical silica aerogels have nonlinear optical coefficient similar to that of glass $(\\simeq 10^{-12} $m$^2/$W), with negligible optical nonlinear absorption. The non\\-li\\-near coefficient can be increased to values in the range of $10^{-10} $m$^2/$W by embedding an absorbing dye in the aerogel. This value is one order of magnitude higher than that observed in the pure dye and in typical highly nonlinear materials like liquid crystals.

  2. Dissolved Organic Matter in Freshwaters

    Science.gov (United States)

    Perdue, E. M.; Ritchie, J. D.

    2003-12-01

    Organic matter in freshwaters exists as dissolved molecules, colloids, and particles. It is appropriate to regard these distinctions as dynamic, however, because organic matter can be interconverted readily between these forms by dissolution and precipitation, sorption and desorption, aggregation and disaggregation, etc. Dissolved organic matter (DOM), the subject of this chapter, is defined operationally as the fraction of organic matter in a water sample that passes through a 0.45 μm filter. In the authors' opinion, the scientific literature on organic matter in freshwaters will be better reflected in this review, if data are considered without regard to the manner in which water samples may have been filtered. This more general approach is warranted because: * many submicron colloids and some microorganisms can pass through 0.45 μm filters; * the effective pore size of a 0.45 μm filter is usually unknown, because it is decreased by partial clogging during the filtration of a water sample; * some important studies have been conducted on unfiltered samples or on samples that were filtered through other types of filters; and * some important studies have been conducted on samples that were concentrated with ultrafiltration (UF), nanofiltration (NF), or reverse osmosis (RO) membranes.As methods for fractionation and isolation of organic matter in freshwaters have evolved, and as the intensity of research has waxed and waned in various academic disciplines, a rich and potentially confusing nomenclature has evolved for organic matter in freshwaters. Some of the more commonly encountered descriptors and their associated acronyms, if any, are yellow organic acids (YOAs), aquatic humus, DOM, and natural organic matter (NOM). Regardless of the terminology used in the original literature, the organic matter in freshwaters is referred to as DOM in this review, except when it is necessary to be more specific.

  3. Niobia-silica and silica membranes for gas separation

    NARCIS (Netherlands)

    Boffa, Vittorio

    2008-01-01

    This thesis describes the development of ceramic membranes suitable for hydrogen separation and CO2 recovery from gaseous streams. The research work was focused on the three different parts of which gas selective ceramic membranes are composed, i.e., the microporous gas selective silica layer, the m

  4. Leaching of Particulate and Dissolved Organic Carbon from Compost Applied to Bioretention Systems

    Science.gov (United States)

    Iqbal, Hamid; Flury, Markus; Mullane, Jessica; Baig, Muhammad

    2015-04-01

    Compost is used in bioretention systems to improve soil quality, to promote plant growth, and to remove metal contaminants from stormwater. However, compost itself, particularly when applied freshly, can be a source of contamination of the stormwater. To test the potential contamination caused by compost when applied to bioretention systems, we continuously leached a compost column with water under unsaturated conditions and characterized dissolved and particulate organic matter in the leachate. Freshly applied, mature compost leached up to 400 mg/L of dissolved organic carbon and 2,000 mg/L of suspended particulate organic carbon. It required a cumulative water flux of 4,000 mm until concentrations of dissolved and particulate organic carbon declined to levels typical for surface waters. Although, dissolved and particulate organic carbon are not contaminants per se, they can facilitate the movement of metals, thereby enhancing the mobility of toxic metals present in stormwater. Therefore, we recommended that compost is washed before it is applied to bioretention systems. Keywords compost; leachate; alkali extract; dissolved organic carbon; flux

  5. Martian Hot Springs? Silica deposits in the Nili Patera Caldera.

    Science.gov (United States)

    Skok, J. R.; Mustard, J. F.; Ehlmann, B. L.; Murchie, S. L.

    2011-12-01

    The caldera of the Syrtis Major volcanic complex shows evidence of a late-stage, chemically evolved eruption that emplaced a volcanic cone and an evolved dacitic lava flow. This cone and flow contain several light-toned deposits, spectrally defined, with the CRISM instrument, by a broad asymmetrical absorption centered at 2.21 μm that is characteristic of a Si-OH bond. Additional weak 1.4 and 1.9 μm OH- and H2O related absorption features were detected that combined with the 2.21 μm feature confirms the detection of hydrated silica (SiO2 nH2O). The deposits are expressed morphologically as low mounds in stereo HiRISE data that superpose and post-date the volcanic flows. This mineral detection and volcanic context is consistent with several formation mechanisms, notably volcanic outgassing leading to fumarole surface alteration or silica deposition in volcanically driven hot springs. Since current orbital observations do not allow conclusive determination of precise mechanism, we here focus on the hot spring silica depositional hypothesis and investigate what the current observations tell us about such a system. These deposits would occur as post-eruption volcanic heat-driven hydrothermal convection of ground and possibly magmatic waters. Convecting, heated water would dissolve the igneous minerals in the basalt that forms the majority of the caldera mobilizing significant silica. Silica saturated fluids that reach the surface cool and deposit amorphous silica as the silica solubility in the fluids decreases. The large size and mound building nature of individual deposits require a significant and sustained fluid source for deposition. That amorphous silica deposits were detected in several distinct regions illustrates the prevalence of this process in this volcanic complex. The largest deposit is located on the southern flank of the cone and forms a fan-shaped morphology as the material is sourced from a vent and flows downslope. Another small deposit was

  6. A thermodynamic and kinetic model for paste–aggregate interactions and the alkali–silica reaction

    Energy Technology Data Exchange (ETDEWEB)

    Guthrie, George D., E-mail: geo@lanl.gov; Carey, J. William

    2015-10-15

    A new conceptual model is developed for ASR formation based on geochemical principles tied to aqueous speciation, silica solubility, kinetically controlled mineral dissolution, and diffusion. ASR development is driven largely by pH and silica gradients that establish geochemical microenvironments between paste and aggregate, with gradients the strongest within the aggregate adjacent to the paste boundary (i.e., where ASR initially forms). Super-saturation of magadiite and okenite (crystalline ASR surrogates) occurs in the zone defined by gradients in pH, dissolved silica, Na{sup +}, and Ca{sup 2} {sup +}. This model provides a thermodynamic rather than kinetic explanation of why quartz generally behaves differently from amorphous silica: quartz solubility does not produce sufficiently high concentrations of H{sub 4}SiO{sub 4} to super-saturate magadiite, whereas amorphous silica does. The model also explains why pozzolans do not generate ASR: their fine-grained character precludes formation of chemical gradients. Finally, these gradients have interesting implications beyond the development of ASR, creating unique biogeochemical environments.

  7. Dissolved iron and iron isotopes in the southeastern Pacific Ocean

    Science.gov (United States)

    Fitzsimmons, Jessica N.; Conway, Tim M.; Lee, Jong-Mi; Kayser, Richard; Thyng, Kristen M.; John, Seth G.; Boyle, Edward A.

    2016-10-01

    The Southeast Pacific Ocean is a severely understudied yet dynamic region for trace metals such as iron, since it experiences steep redox and productivity gradients in upper waters and strong hydrothermal iron inputs to deep waters. In this study, we report the dissolved iron (dFe) distribution from seven stations and Fe isotope ratios (δ56Fe) from three of these stations across a near-zonal transect from 20 to 27°S. We found elevated dFe concentrations associated with the oxygen-deficient zone (ODZ), with light δ56Fe implicating porewater fluxes of reduced Fe. However, temporal dFe variability and rapid δ56Fe shifts with depth suggest gradients in ODZ Fe source and/or redox processes vary over short-depth/spatial scales. The dFe concentrations decreased rapidly offshore, and in the upper ocean dFe was controlled by biological processes, resulting in an Fe:C ratio of 4.2 µmol/mol. Calculated vertical diffusive Fe fluxes were greater than published dust inputs to surface waters, but both were orders of magnitude lower than horizontal diffusive fluxes, which dominate dFe delivery to the gyre. The δ56Fe data in the deep sea showed evidence for a -0.2‰ Antarctic Intermediate Water end-member and a heavy δ56Fe of +0.55‰ for distally transported hydrothermal dissolved Fe from the East Pacific Rise. These heavy δ56Fe values were contrasted with the near-crustal δ56Fe recorded in the hydrothermal plume reaching Station ALOHA in the North Pacific. The heavy hydrothermal δ56Fe precludes a nanopyrite composition of hydrothermal dFe and instead suggests the presence of oxides or, more likely, binding of hydrothermal dFe by organic ligands in the distal plume.

  8. Ringing phenomenon in silica microspheres

    Institute of Scientific and Technical Information of China (English)

    Chunhua Dong; Changling Zou; Jinming Cui; Yong Yang; Zhengfu Han; Guangcan Guo

    2009-01-01

    Whispering gallery modes in silica microspheres are excited by a tunable continuous-wave laser through the fiber taper. Ringing phenomenon can be observed with high frequency sweeping speed. The thermal nonlinearity in the microsphere can enhance this phenomenon. Our measurement results agree very well with the theoretical predictions by the dynamic equation.

  9. Flux-P: Automating Metabolic Flux Analysis

    Directory of Open Access Journals (Sweden)

    Birgitta E. Ebert

    2012-11-01

    Full Text Available Quantitative knowledge of intracellular fluxes in metabolic networks is invaluable for inferring metabolic system behavior and the design principles of biological systems. However, intracellular reaction rates can not often be calculated directly but have to be estimated; for instance, via 13C-based metabolic flux analysis, a model-based interpretation of stable carbon isotope patterns in intermediates of metabolism. Existing software such as FiatFlux, OpenFLUX or 13CFLUX supports experts in this complex analysis, but requires several steps that have to be carried out manually, hence restricting the use of this software for data interpretation to a rather small number of experiments. In this paper, we present Flux-P as an approach to automate and standardize 13C-based metabolic flux analysis, using the Bio-jETI workflow framework. Exemplarily based on the FiatFlux software, it demonstrates how services can be created that carry out the different analysis steps autonomously and how these can subsequently be assembled into software workflows that perform automated, high-throughput intracellular flux analysis of high quality and reproducibility. Besides significant acceleration and standardization of the data analysis, the agile workflow-based realization supports flexible changes of the analysis workflows on the user level, making it easy to perform custom analyses.

  10. Silica-Coated Liposomes for Insulin Delivery

    Directory of Open Access Journals (Sweden)

    Neelam Dwivedi

    2010-01-01

    Full Text Available Liposomes coated with silica were explored as protein delivery vehicles for their enhanced stability and improved encapsulation efficiency. Insulin was encapsulated within the fluidic phosphatidylcholine lipid vesicles by thin film hydration at pH 2.5, and layer of silica was formed above lipid bilayer by acid catalysis. The presence of silica coating and encapsulated insulin was identified using confocal and electron microscopy. The native state of insulin present in the formulation was evident from Confocal Micro-Raman spectroscopy. Silica coat enhances the stability of insulin-loaded delivery vehicles. In vivo study shows that these silica coated formulations were biologically active in reducing glucose levels.

  11. MOUTH DISSOLVING FILM AND THEIR PATENT: AN OVERVIEW

    OpenAIRE

    2012-01-01

    Now days the researchers are focusing on the fast dissolving dosage form (FDDF’s).The fast dissolving dosage forms includes the mouth dissolving tablets, mouth dissolving thin films .The alternative words used for these dosage forms are fast disintegrating, orodispersible, fast dissolving. The oral thin film technology (OTF’s) is a dissolvable film technology have evolved from a purely confectionery novelty from a drug delivery platform. The OTH dosage form dissolves in the moth without nee...

  12. Dissolved carbohydrate in the central Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Dhople, V.M.; Bhosle, N.B.

    Seawater samples (161), collected from 8 depths (0 to 1000 m) at 21 stations were analysed for total dissolved carbohydrate. Dissolved carbohydrate concentrations varied from 0.072 to 1.15 mg.l-1. Carbohydrate concentrations did not decrease...

  13. The Pozzolanic reaction of silica fume

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede

    2012-01-01

    Silica fume is a very important supplementary cementitious binder in High-Performance and Ultra High-Performance Concretes. Through its pozzolanic reaction the silica fume densifies the concrete micro-structure, in particular it strengthens the paste-aggregate interfacial transition zone. In the ...... of activation of the pozzolanic reaction of silica fume is estimated. The results show that the pozzolanic reaction of silica fume has notable differences from Portland cement hydration.......Silica fume is a very important supplementary cementitious binder in High-Performance and Ultra High-Performance Concretes. Through its pozzolanic reaction the silica fume densifies the concrete micro-structure, in particular it strengthens the paste-aggregate interfacial transition zone....... In the present paper different aspects of the pozzolanic reaction of silica fume are investigated. These include chemical shrinkage, isothermal heat development and strength development. Key data for these are given and compared with theoretical calculations, and based on presented measurements the energy...

  14. Silica Pigments for Glossy Ink Jet Media

    Institute of Scientific and Technical Information of China (English)

    Sun Qi; Michael R. Sestrick; Yoshi Sugimoto; William A. Welsh

    2004-01-01

    Silica is a versatile pigment for ink jet media. Micronized silica gel is the worldwide standard for high performance matte ink jet media. For glossy ink jet media, several different forms of silica are widely used. Submicron silica gel dispersions, with either anionic or cationic surfaces, can be employed in either absorptive basecoat layers or in the glossy ink receptive top layer. Colloidal silica, with a variety of particle sizes and surface modifications, is utilized extensively in glossy top layers. It will show how various silica pigments can be utilized in glossy ink receptive coatings, both in cast based glossy media and RC based glossy media. Several novel silica pigments will be examined by relating the physical properties of the pigments and the formula variables to the print quality of the ink jet media.

  15. Dissolved air flotation and me.

    Science.gov (United States)

    Edzwald, James K

    2010-04-01

    This paper is mainly a critical review of the literature and an assessment of what we know about dissolved air flotation (DAF). A few remarks are made at the outset about the author's personal journey in DAF research, his start and its progression. DAF has been used for several decades in drinking water treatment as an alternative clarification method to sedimentation. DAF is particularly effective in treating reservoir water supplies; those supplies containing algae, natural color or natural organic matter; and those with low mineral turbidity. It is more efficient than sedimentation in removing turbidity and particles for these type supplies. Furthermore, it is more efficient in removing Giardia cysts and Cryptosporidium oocysts. In the last 20 years, fundamental models were developed that provide a basis for understanding the process, optimizing it, and integrating it into water treatment plants. The theories were tested through laboratory and pilot-plant studies. Consequently, there have been trends in which DAF pretreatment has been optimized resulting in better coagulation and a decrease in the size of flocculation tanks. In addition, the hydraulic loading rates have increased reducing the size of DAF processes. While DAF has been used mainly in conventional type water plants, there is now interest in the technology as a pretreatment step in ultrafiltration membrane plants and in desalination reverse osmosis plants. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

  16. Amazon River dissolved load: temporal dynamics and annual budget from the Andes to the ocean.

    Science.gov (United States)

    Moquet, Jean-Sébastien; Guyot, Jean-Loup; Crave, Alain; Viers, Jérôme; Filizola, Naziano; Martinez, Jean-Michel; Oliveira, Tereza Cristina; Sánchez, Liz Stefanny Hidalgo; Lagane, Christelle; Casimiro, Waldo Sven Lavado; Noriega, Luis; Pombosa, Rodrigo

    2016-06-01

    The aim of the present study is to estimate the export fluxes of major dissolved species at the scale of the Amazon basin, to identify the main parameters controlling their spatial distribution and to identify the role of discharge variability in the variability of the total dissolved solid (TDS) flux through the hydrological cycle. Data are compiled from the monthly hydrochemistry and daily discharge database of the "Programa Climatologico y Hidrologico de la Cuenca Amazonica de Bolivia" (PHICAB) and the HYBAM observatories from 34 stations distributed over the Amazon basin (for the 1983-1992 and 2000-2012 periods, respectively). This paper consists of a first global observation of the fluxes and temporal dynamics of each geomorphological domain of the Amazon basin. Based on mean interannual monthly flux calculations, we estimated that the Amazon basin delivered approximately 272 × 10(6) t year(-1) (263-278) of TDS during the 2003-2012 period, which represents approximately 7 % of the continental inputs to the oceans. This flux is mainly made up by HCO3, Ca and SiO2, reflecting the preferential contributions of carbonate and silicate chemical weathering to the Amazon River Basin. The main tributaries contributing to the TDS flux are the Marañon and Ucayali Rivers (approximately 50 % of the TDS production over 14 % of the Amazon basin area) due to the weathering of carbonates and evaporites drained by their Andean tributaries. An Andes-sedimentary area-shield TDS flux (and specific flux) gradient is observed throughout the basin and is first explained by the TDS concentration contrast between these domains, rather than variability in runoff. This observation highlights that, under tropical context, the weathering flux repartition is primarily controlled by the geomorphological/geological setting and confirms that sedimentary areas are currently active in terms of the production of dissolved load. The log relationships of concentration vs discharge have

  17. KOMBINASI ULTRAFILTRASI DAN DISSOLVED AIR FLOTATION UNTUK PEMEKATAN MIKROALGA

    Directory of Open Access Journals (Sweden)

    I Nyoman Widiasa

    2014-05-01

    study is aimed to investigate the potential of combination of ultrafiltration (UF and dissolved air flotation  (DAF for concentration of microalgae in laboratory scale. The experimental results showed that fluxes of the UF membrane decreased sharply due to deposition of microalgae biomass during first 20 minutes of filtration. Periodically backwash using the UF permeate (backwash  interval = 20 minutes;  backwash duration = 10 seconds;  backwash pressure = 1 bar gave an effective fouling control to maintain reasonable stable fluxes. In addition,  the UF membrane gave separation of microalgae biomass ~ 100%. Permeate quality is strongly stable in which turbidity < 0.5 NTU, organic content < 10 mg/L, and color < 10 PCU.  Moreover, concentration of the UF retentate by DAF under saturation pressure of 6 bars was able to produced microalgae feedstock having 20 g/L dry microalgae. PAC is required for DAF feed with dosage of 1.3–1.6 mg PAC/mg suspended solids.

  18. Active silica sources in the Sele formation and quartz cementation in mudstone-Examples from the Siri Canyon, Danish North Sea

    DEFF Research Database (Denmark)

    Kazerouni, Afsoon Moatari; Friis, Henrik; Svendsen, Johan B.

    The deep marine sandstones in the Siri Canyon (Fig.1) have been reported to import significant amounts of dissolved silica from adjacent Palaeocene shales during early diagenesis (Stokkendal et al. 2009; Weibel et al. 2010). We have studied the diagenesis of one of these shales, the Sele Formation...

  19. Clustering of Emerging Flux

    Science.gov (United States)

    Ruzmaikin, A.

    1997-01-01

    Observations show that newly emerging flux tends to appear on the Solar surface at sites where there is flux already. This results in clustering of solar activity. Standard dynamo theories do not predict this effect.

  20. Ordered mesoporous silica: microwave synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Fantini, M.C.A. [IF-USP, CP 66318, 05315-970, Sao Paulo, SP (Brazil)]. E-mail: mfantini@if.usp.br; Matos, J.R. [IQ-USP, CP 26077, 05599-970, Sao Paulo, SP (Brazil); Silva, L.C. Cides da [IQ-USP, CP 26077, 05599-970, Sao Paulo, SP (Brazil); Mercuri, L.P. [IQSC-USP, CP 780, 13560-970, Sao Carlos, SP (Brazil); Chiereci, G.O. [IQSC-USP, CP 780, 13560-970, Sao Carlos, SP (Brazil); Celer, E.B. [Department of Chemistry, Kent State University, Kent, OH 44240 (United States); Jaroniec, M. [Department of Chemistry, Kent State University, Kent, OH 44240 (United States)

    2004-09-25

    Ordered mesoporous silicas, FDU-1, synthesized by using triblock copolymer, EO{sub 39}BO{sub 47}EO{sub 39}, as template were hydrothermally treated in a microwave oven at 373 K for different periods of time. The structural and morphological properties of these silicas were investigated by X-ray diffraction and nitrogen adsorption and compared with those for the FDU-1 samples prepared by conventional hydrothermal treatment at 373 K. All samples were calcined at 813 K in N{sub 2} and air. This procedure succeeded in producing ordered cage-like mesoporous structures even after 15 min of the microwave treatment. The best sample was obtained after 60 min of the microwave treatment, which is reflected by narrow pore size distribution, uniform pore size entrances and thick mesopore walls. Longer time of the microwave treatment increased nonuniformity of the pore entrance sizes as evidenced by changes in the hysteresis loops of nitrogen adsorption isotherms.

  1. FLUXES FOR MECHANIZED ELECTRIC WELDING,

    Science.gov (United States)

    WELDING FLUXES, WELDING ), (* WELDING , WELDING FLUXES), ARC WELDING , WELDS, STABILITY, POROSITY, WELDING RODS, STEEL, CERAMIC MATERIALS, FLUXES(FUSION), TITANIUM ALLOYS, ALUMINUM ALLOYS, COPPER ALLOYS, ELECTRODEPOSITION

  2. Purging dissolved oxygen by nitrogen bubble aeration

    Science.gov (United States)

    Yamashita, Tatsuya; Ando, Keita

    2016-11-01

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

  3. Silica exposure and systemic vasculitis.

    Science.gov (United States)

    Mulloy, Karen B

    2003-12-01

    Work in Department of Energy (DOE) facilities has exposed workers to multiple toxic agents leading to acute and chronic diseases. Many exposures were common to numerous work sites. Exposure to crystalline silica was primarily restricted to a few facilities. I present the case of a 63-year-old male who worked in DOE facilities for 30 years as a weapons testing technician. In addition to silica, other workplace exposures included beryllium, various solvents and heavy metals, depleted uranium, and ionizing radiation. In 1989 a painful macular skin lesion was biopsied and diagnosed as leukocytoclastic vasculitis. By 1992 he developed gross hematuria and dyspnea. Blood laboratory results revealed a serum creatinine concentration of 2.1 mg/dL, ethrythrocyte sedimentation rate of 61 mm/hr, negative cANCA (antineutrophil cytoplasmic antibody cytoplasmic pattern), positive pANCA (ANCA perinuclear pattern), and antiglomerular basement membrane negative. Renal biopsy showed proliferative (crescentric) and necrotizing glomerulonephritis. The patient's diagnoses included microscopic polyangiitis, systemic necrotizing vasculitis, leukocytoclastic vasculitis, and glomerulonephritis. Environmental triggers are thought to play a role in the development of an idiopathic expression of systemic autoimmune disease. Crystalline silica exposure has been linked to rheumatoid arthritis, scleroderma, systemic lupus erythematosus, rapidly progressive glomerulonephritis and some of the small vessel vasculitides. DOE workers are currently able to apply for compensation under the federal Energy Employees Occupational Illness Compensation Program (EEOICP). However, the only diseases covered by EEOICP are cancers related to radiation exposure, chronic beryllium disease, and chronic silicosis.

  4. Simulated changes in dissolved Iron deposition to the global ocean driven by human activity

    Science.gov (United States)

    Myriokefalitakis, Stelios; Daskalakis, Nikos; Mihalopoulos, Nikos; Baker, Alex R.; Nenes, Athanassios; Kanakidou, Maria

    2015-04-01

    The global 3-d chemistry transport atmospheric model TM4-ECPL is used to simulate the atmospheric cycle of iron (Fe) and evaluate its atmospheric deposition to the ocean by accounting for both Fe natural and anthropogenic sources as well as of the proton and ligand promoted iron mobilisation from dust aerosol. Model evaluation is performed by comparison to available observations. Present day dissolved Fe deposition presents strong spatial and temporal variability with an annual deposition flux about 0.489 Tg(Fe)/yr from which about 25% are deposited over the ocean. The model simulates past, present and future iron deposition accounting for changes in anthropogenic emissions. We show that dissolved iron deposition has significantly increased since 1850 while it is expected to decrease in the future due to air pollution regulations. These changes affect the atmospheric dissolved Fe supply to High-Nutrient-Low-Chlorophyll oceanic areas characterized by Fe scarcity.

  5. Patterns of Flux Emergence

    Science.gov (United States)

    Title, A.; Cheung, M.

    2008-05-01

    The high spatial resolution and high cadence of the Solar Optical Telescope on the JAXA Hinode spacecraft have allowed capturing many examples of magnetic flux emergence from the scale of granulation to active regions. The observed patterns of emergence are quite similar. Flux emerges as a array of small bipoles on scales from 1 to 5 arc seconds throughout the region that the flux eventually condenses. Because the fields emerging from the underlying flux rope my appear many in small segments and the total flux (absolute sum) is not a conserved quantity the amount of total flux on the surface may vary significantly during the emergence process. Numerical simulations of flux emergence exhibit patterns similar to observations. Movies of both observations and numerical simulations will be presented.

  6. Seasonal variations of dissolved and particulate copper species in estuarine waters

    Science.gov (United States)

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

    2005-01-01

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

  7. Preparation of polystyrene/silica nanocomposites by radical copolymerization of styrene with silica macromonomer

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A two-stage process has been developed to generate the silica-based macromonomer through surface-modification of silica with polymerizable vinyl groups. The silica surfaces were treated with excess 2,4-toluene diisocynate (TDI), after which the residual isocyanate groups were converted into polymerizable vinyl groups by reaction with hydroxypropylacrylate (HPA). Thus, polystyrene/silica nanocomposites were prepared by conventional radical copolymerization of styrene with silica macromonomer. The main effecting factors, such as ratios of styrene to the macromonomer, together with polymerization time on the copolymerization were studied in detail. FTIR, DSC and TGA were utilized to characterize the nanocomposites. Experimental results revealed that the silica nanoparticles act as cross-linking points in the polystytene/silica nanocomposites, and the glass transition temperatures of the nanocomposites are higher than that of the corresponding pure polystyrene. The glass transition temperatures of nanocomposites increased with the increasing of silica contents, which were further ascertained by DSC.

  8. Preparation of polyamide 6/silica nanocomposites from silica surface initiated ring-opening anionic polymerization

    Directory of Open Access Journals (Sweden)

    2007-07-01

    Full Text Available Polyamide 6/silica nanocomposites were synthesized by in situ ring-opening anionic polymerization of ε-caprolactam in the presence of sodium caprolactamate as a catalyst and caprolactam-functionalized silica as an initiator. The initiator precursor, isocyanate-functionalized silica, was prepared by directly reacting commercial silica with excess toluene 2,4-diisocyanate. This polymerization was found to occur in a highly efficient manner at relatively low reaction temperature (170°C and short reaction times (6 h. FTIR spectroscopy was utilized to follow the introduction and consumption of isocyanate groups on the silica surface. Thermogravimetric analysis indicated that the polyamide 6 was successfully grown from the silica surface. Transmission electron microscopy was utilized to image polymer-functionalized silica, showing fine dispersion of silica particles and their size ranging from 20 to 40 nm.

  9. Chromophoric dissolved organic matter export from U.S. rivers

    Science.gov (United States)

    Spencer, Robert G. M.; Aiken, George R.; Dornblaser, Mark M.; Butler, Kenna D.; Holmes, R. Max; Fiske, Greg; Mann, Paul J.; Stubbins, Aron

    2013-01-01

    Chromophoric dissolved organic matter (CDOM) fluxes and yields from 15 major U.S. rivers draining an assortment of terrestrial biomes are presented. A robust relationship between CDOM and dissolved organic carbon (DOC) loads is established (e.g., a350 versus DOC; r2 = 0.96, p export from ungauged watersheds. A large variation in CDOM yields was found across the rivers. The two rivers in the north-eastern U.S. (Androscoggin and Penobscot), the Edisto draining into the South Atlantic Bight, and some rivers draining into the Gulf of Mexico (Atchafalaya and Mobile) exhibit the highest CDOM yields, linked to extensive wetlands in these watersheds. If the Edisto CDOM yield is representative of other rivers draining into the South Atlantic Bight, this would result in a CDOM load equivalent to that of the Mississippi from a region of approximately 10% of the Mississippi watershed, indicating the importance of certain regions with respect to the role of terrigenous CDOM in ocean color budgets.

  10. Seasonal Variation and Sources of Dissolved Nutrients in the Yellow River, China

    Directory of Open Access Journals (Sweden)

    Yao Gong

    2015-08-01

    Full Text Available The rapid growth of the economy in China has caused dramatic growth in the industrial and agricultural development in the Yellow River (YR watershed. The hydrology of the YR has changed dramatically due to the climate changes and water management practices, which have resulted in a great variation in the fluxes of riverine nutrients carried by the YR. To study these changes dissolved nutrients in the YR were measured monthly at Lijin station in the downstream region of the YR from 2002 to 2004. This study provides detailed information on the nutrient status for the relevant studies in the lower YR and the Bohai Sea. The YR was enriched in nitrate (average 314 μmol·L−1 with a lower concentration of dissolved silicate (average 131 μmol·L−1 and relatively low dissolved phosphate (average 0.35 μmol·L−1. Nutrient concentrations exhibited substantial seasonal and yearly variations. The annual fluxes of dissolved inorganic nitrogen, phosphate, and silicate in 2004 were 5.3, 2.5, and 4.2 times those in 2002, respectively, primarily due to the increase in river discharge. The relative contributions of nutrient inputs to nitrogen in the YR were: wastewater > fertilizer > atmospheric deposition > soil; while to phosphorus were: wastewater > fertilizer > soil > atmospheric deposition. The ratios of N, P and Si suggest that the YR at Lijin is strongly P-limited with respect to potential phytoplankton growth.

  11. Dissolved barium and radium isotopes in the Chao Phraya River estuarine mixing zone in Thailand

    Science.gov (United States)

    Nozaki, Yoshiyuki; Yamamoto, Yoshiyuki; Manaka, Toshiki; Amakawa, Hiroshi; Snidvongs, Anond

    2001-08-01

    New data on dissolved Ba, 226Ra and 228Ra were obtained in the Chao Phraya River estuarine mixing zone in 1996. Although desorption of Ba from river-suspended sediments gives rise to elevated dissolved Ba concentrations in the low salinity ( S10) region have been observed depending upon the sampling periods. Under a dinofragellates ( Noctiluca) red tide condition in January, significant biological removal of dissolved Ba took place in the mid-salinity ( S=10 -16) region, whereas under normal condition in July and November, the dissolved Ba followed a conservative linear mixing trend. 226Ra is also supplied to the coastal waters by desorption from river-transported sediments in a delayed fashion compared to Ba, at least, in the latter seasons, whereas 228Ra is predominantly supplied by diffusion from underlying sediments to the water largely in the higher salinity ( S>15) region. These geochemical observations in July and November fit well to the previous studies done for other estuarine environments. Total riverine fluxes to the Gulf of Thailand were estimated to be 6.2×10 6 mol Ba/yr and 1.5×10 13 dpm 226Ra/yr, about half of which is contributed by the Chao Phraya River. Although there is a sign indicating that ground water input may be contributing to the fluxes of 226Ra and Ba, we were unable to quantify them due to lack of information on the exchange rate of the coastal waters with open seawater.

  12. Dissolved Trace Metals in the Tay Estuary

    Science.gov (United States)

    Owens, R. E.; Balls, P. W.

    1997-04-01

    Dissolved trace metals have been studied over an annual cycle in the relatively pristine Tay estuary (Scotland). The absence of a major anthropogenic signal has enabled some of the more subtle natural processes controlling trace metal distributions to be identified. Concentration ranges of dissolved metals in the Tay are similar to, or lower than, those observed in more industrialized estuaries. All metals behave non-conservatively in the Tay. Interactions with biogenic and detrital particulate phases are important in controlling dissolved trace metal concentrations. The degradation of organic matter appears to be particularly important for Cu. Removal of dissolved metals was observed in the turbidity maximum zone; a simple model was used to demonstrate that this could be accounted for by adsorption onto suspended particulate matter. At high salinity, coincident peaks of all six metals with ammonia and phosphate are attributed to sewage inputs from Dundee at the mouth of the estuary.

  13. Production of macroaggregates from dissolved exopolymeric substances (EPS) of bacterial and diatom origin

    Digital Repository Service at National Institute of Oceanography (India)

    Bhaskar, P.V.; Grossart, H.P.; Bhosle, N.B.; Simon, M.

    -1 1 Production of macroaggregates from dissolved exopolymeric substances (EPS) of bacterial and diatom origin P V Bhaskar1*, Hans-Peter Grossart2, 3, N B Bhosle1 and Meinhard Simon2. 1National Institute of Oceanography, Dona Paula, GOA- 403 004...-cycles [14]. Moreover, the composition and quality of these aggregates influence feeding and grazing rates of filter feeders [15], bacterial re-mineralization of organic matter, and POM-DOM conversion [16, 17, 18], thereby regulating the vertical flux...

  14. Sealed silica pressure ampoules for crystal growth

    Science.gov (United States)

    Holland, L. R.

    1984-01-01

    The properties of vitreous silica and the mechanics of thick walled pressure vessels are reviewed with regard to the construction of sealed silica crucibles such as are used in the growth of mercury-cadmium telluride crystals. Data from destructive rupture tests are reported, failure modes discussed, and recommendations for design given. Ordinary commercial clear vitreous silica from flame fused quartz can withstand a surface stress of 20 MPa or more in this application.

  15. Mesoporous Silica: A Suitable Adsorbent for Amines

    Directory of Open Access Journals (Sweden)

    Abdollahzadeh-Ghom Sara

    2009-01-01

    Full Text Available Abstract Mesoporous silica with KIT-6 structure was investigated as a preconcentrating material in chromatographic systems for ammonia and trimethylamine. Its adsorption capacity was compared to that of existing commercial materials, showing its increased adsorption power. In addition, KIT-6 mesoporous silica efficiently adsorbs both gases, while none of the employed commercial adsorbents did. This means that KIT-6 Mesoporous silica may be a good choice for integrated chromatography/gas sensing micro-devices.

  16. MASS BALANCE OF SILICA IN STRAW FROM THE PERSPECTIVE OF SILICA REDUCTION IN STRAW PULP

    OpenAIRE

    Celil Atik; Saim Ates

    2012-01-01

    The high silica content of wheat straw is an important limiting factor for straw pulping. High silica content complicates processing and black liquor recovery, wears out factory installations, and lowers paper quality. Each section of wheat straw has different cells and chemical compositions and thus different silica content. In this work, the silica content of balled straw samples were examined according to their physical components, including internodes, nodes, leaves (sheath and blade), ra...

  17. Enhanced pervaporative desulfurization by polydimethylsiloxane membranes embedded with silver/silica core-shell microspheres.

    Science.gov (United States)

    Cao, Ruijian; Zhang, Xiongfei; Wu, Hong; Wang, Jingtao; Liu, Xiaofei; Jiang, Zhongyi

    2011-03-15

    Pervaporative desulfurization based on membrane technology provides a promising alternative for removal of sulfur substances (as represented by thiophene) in fluid catalytic cracking (FCC) gasoline. The present study focused on the performance enhancement of polydimethylsiloxane (PDMS) membrane by incorporation of core-shell structured silver/silica microspheres. A silane coupling agent, N-[3-(trimethoxysily)propyl]-ethylenediamine (TSD), was used to chelate the Ag(+) via its amino groups and attach the silver seeds onto the silica surface via condensation of its methoxyl groups. The resultant microspheres were characterized by Zeta-positron annihilation lifetime spectroscopy (ZetaPALS), inductively coupled plasmaoptical emission spectrophotometer (ICP), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The Ag(+)/SiO(2)-PDMS composite membranes were prepared by blending PDMS with the as-synthesized silver/silica microspheres. PALS analysis was used to correlate the apparent fractional free volume with permeation flux. The sorption selectivity towards thiophene was enhanced after incorporation of silver/silica microspheres due to the π-complexation between the silver on the microsphere surface and the thiophene molecules. The pervaporative desulfurization performance of the composite membrane was investigated using thiophene/n-octane mixture as a model gasoline. The composite membrane exhibited an optimum desulfurization performance with a permeation flux of 7.76 kg/(m(2)h) and an enrichment factor of 4.3 at the doping content of 5%. Copyright © 2011 Elsevier B.V. All rights reserved.

  18. Enhanced pervaporative desulfurization by polydimethylsiloxane membranes embedded with silver/silica core-shell microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Cao Ruijian; Zhang Xiongfei [Key Laboratory for Green Chemical Technology, Ministry of Education of China, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Wu Hong, E-mail: wuhong2000@gmail.com [Key Laboratory for Green Chemical Technology, Ministry of Education of China, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Tianjin Key Laboratory of Membrane Science and Desalination Technology, Tianjin University, Tianjin 300072 (China); Wang Jingtao; Liu Xiaofei [Key Laboratory for Green Chemical Technology, Ministry of Education of China, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Jiang Zhongyi [Key Laboratory for Green Chemical Technology, Ministry of Education of China, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology, Nanjing 210009 (China)

    2011-03-15

    Pervaporative desulfurization based on membrane technology provides a promising alternative for removal of sulfur substances (as represented by thiophene) in fluid catalytic cracking (FCC) gasoline. The present study focused on the performance enhancement of polydimethylsiloxane (PDMS) membrane by incorporation of core-shell structured silver/silica microspheres. A silane coupling agent, N-[3-(trimethoxysily)propyl]-ethylenediamine (TSD), was used to chelate the Ag{sup +} via its amino groups and attach the silver seeds onto the silica surface via condensation of its methoxyl groups. The resultant microspheres were characterized by Zeta-positron annihilation lifetime spectroscopy (ZetaPALS), inductively coupled plasmaoptical emission spectrophotometer (ICP), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The Ag{sup +}/SiO{sub 2}-PDMS composite membranes were prepared by blending PDMS with the as-synthesized silver/silica microspheres. PALS analysis was used to correlate the apparent fractional free volume with permeation flux. The sorption selectivity towards thiophene was enhanced after incorporation of silver/silica microspheres due to the {pi}-complexation between the silver on the microsphere surface and the thiophene molecules. The pervaporative desulfurization performance of the composite membrane was investigated using thiophene/n-octane mixture as a model gasoline. The composite membrane exhibited an optimum desulfurization performance with a permeation flux of 7.76 kg/(m{sup 2} h) and an enrichment factor of 4.3 at the doping content of 5%.

  19. Surface modification to produce hydrophobic nano-silica particles using sodium dodecyl sulfate as a modifier

    Energy Technology Data Exchange (ETDEWEB)

    Qiao, Bing; Liang, Yong; Wang, Ting-Jie, E-mail: wangtj@tsinghua.edu.cn; Jiang, Yanping

    2016-02-28

    Graphical abstract: Nano silica particle was modified to produce hydrophobic surface with contact angle of 107° using the water soluble SDS as a modifier through a new route. The grafted density reached 1.82–2 nm. Brønsted acid sites supply proton to react with SDS via generating carbocation, forming a Si–O–C structure. - Highlights: • Silica was modified to produce hydrophobic surface using SDS as modifier. • The route is free of organic solvent and gets perfect contact of SDS and silica. • Contact angle of modified silica particles reached 107°. • Grafted density on the silica surface reached 1.82 SDS nm{sup −2}. • Brønsted acid sites supply proton to react with SDS via generating carbocation. - Abstract: Hydrophobic silica particles were prepared using the surfactant sodium dodecyl sulfate (SDS) as a modifier by a new route comprising three processes, namely, aqueous mixing, spray drying and thermal treatment. Since SDS dissolves in water, this route is free of an organic solvent and gave a perfect dispersion of SDS, that is, there was excellent contact between SDS and silica particles in the modification reaction. The hydrophobicity of the modified surface was verified by the contact angle of the nano-sized silica particles, which was 107°. The SDS grafting density reached 1.82 nm{sup −2}, which is near the highest value in the literature. The optimal parameters of the SDS/SiO{sub 2} ratio in the aqueous phase, process temperature and time of thermal treatment were determined to be 20%, 200 °C and 30 min, respectively. The grafting mechanism was studied by comparing the modification with that on same sized TiO{sub 2} particles, which indicated that the protons of the Brønsted acid sites on the surface of SiO{sub 2} reacted with SDS to give a carbocation which then formed a Si–O–C structure. This work showed that the hydrophilic surface of silica can be modified to be a hydrophobic surface by using a water soluble modifier SDS in a

  20. Silica deactivation of bead VOC catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Libanati, C.; Pereira, C.J. [Research Division, W. R. Grace and Co., Columbia, MD (United States); Ullenius, D.A. [Grace TEC Systems, De Pere, WI (United States)

    1998-01-15

    Catalytic oxidation is a key technology for controlling the emissions of Volatile Organic Compounds (VOCs) from industrial plants. The present paper examines the deactivation by silica of bead VOC catalysts in a flexographic printing application. Post mortem analyses of field-aged catalysts suggest that organosilicon compounds contained in the printing ink diffuse into the catalyst and deposit as silica particles in the micropores. Laboratory activity evaluation of aged catalysts suggests that silica deposition is non-selective and that silica masks the noble metal active site

  1. Cellular membrane trafficking of mesoporous silica nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Fang, I-Ju [Iowa State Univ., Ames, IA (United States)

    2012-01-01

    This dissertation mainly focuses on the investigation of the cellular membrane trafficking of mesoporous silica nanoparticles. We are interested in the study of endocytosis and exocytosis behaviors of mesoporous silica nanoparticles with desired surface functionality. The relationship between mesoporous silica nanoparticles and membrane trafficking of cells, either cancerous cells or normal cells was examined. Since mesoporous silica nanoparticles were applied in many drug delivery cases, the endocytotic efficiency of mesoporous silica nanoparticles needs to be investigated in more details in order to design the cellular drug delivery system in the controlled way. It is well known that cells can engulf some molecules outside of the cells through a receptor-ligand associated endocytosis. We are interested to determine if those biomolecules binding to cell surface receptors can be utilized on mesoporous silica nanoparticle materials to improve the uptake efficiency or govern the mechanism of endocytosis of mesoporous silica nanoparticles. Arginine-glycine-aspartate (RGD) is a small peptide recognized by cell integrin receptors and it was reported that avidin internalization was highly promoted by tumor lectin. Both RGD and avidin were linked to the surface of mesoporous silica nanoparticle materials to investigate the effect of receptor-associated biomolecule on cellular endocytosis efficiency. The effect of ligand types, ligand conformation and ligand density were discussed in Chapter 2 and 3. Furthermore, the exocytosis of mesoporous silica nanoparticles is very attractive for biological applications. The cellular protein sequestration study of mesoporous silica nanoparticles was examined for further information of the intracellular pathway of endocytosed mesoporous silica nanoparticle materials. The surface functionality of mesoporous silica nanoparticle materials demonstrated selectivity among the materials and cancer and normal cell lines. We aimed to determine

  2. Practical Hydrogen Loading of Air Silica Fibres

    DEFF Research Database (Denmark)

    Sørensen, Henrik Rokkjær; Jensen, Jesper Bevensee; Jensen, Jesper Bo Damm

    2005-01-01

    A method for hydrogen-loading air-silica optical fibres has been developed allowing out-diffusion times comparable to standard step-index fibres. Examples of the first grating written in Ge-doped air-silica fibres using a 266nm UV-laser are shown.......A method for hydrogen-loading air-silica optical fibres has been developed allowing out-diffusion times comparable to standard step-index fibres. Examples of the first grating written in Ge-doped air-silica fibres using a 266nm UV-laser are shown....

  3. Nanoporous silica membranes with high hydrothermal stability

    DEFF Research Database (Denmark)

    Boffa, Vittorio; Magnacca, Giualiana; Yue, Yuanzheng

    Despite the use of sol-gel derived nanoporous silica membranes in substitution of traditional separation processes is expected leading to vast energy savings, their intrinsic poor steam-stability hampers their application at an industrial level. Transition metal ions can be used as dopant...... to improve the stability of nanoporous silica structure. This work is a quantitative study on the impact of type and concentration of transition metal ions on the microporous structure and stability of amorphous silica-based membranes, which provides information on how to design chemical compositions...... and synthetic paths for the fabrication of silica-based membranes with a well accessible and highly stabile nanoporous structure...

  4. Composition of dispersed sedimentary matter and fluxes in the water column of the Caspian Sea

    Science.gov (United States)

    Lisitzin, A. P.; Lukashin, V. N.

    2015-09-01

    This article presents the first data on the chemical composition of dispersed matter from sediment traps with analysis of the sedimentary components that constitute suspended particulate matter (amorphous silica, organic matter (OM), carbonates, and lithogenic matter). It is established that the annual variability of fluxes demonstrates its seasonal growth in spring and summer. High fluxes of these components over the northern and southern slopes of the Derbent Basin are determined by deposition of material from the nepheloid layer formed by the contour current.

  5. Resonance Fluorescence of Fused Silica by the Depopulation of the Ground State

    Directory of Open Access Journals (Sweden)

    Fuat Bayrakceken

    2012-01-01

    Full Text Available Spectroscopically pure fused silica has been used in many applications ranging from optoelectronics and optical fibers to laser flash spectroscopy. Although ultraviolet light irradiated optical absorption spectra and coherence fluorescence of silicon dioxide have been studied in the past, we present discrete absorption and resonance coherent fluorescence line of silicon dioxide which were recorded photographically at 288.2 nm. This discrete fluorescence is observed at room temperature using high photon flux (1024 photon/pulse excitation spectroscopy.

  6. Synthesis of nano-forsterite powder by making use of natural silica sand

    Energy Technology Data Exchange (ETDEWEB)

    Nurbaiti, Upik, E-mail: upik-nurbaiti@mail.unnes.ac.id [Department of Physics, Faculty of Mathematics and Natural Sciences Institut Teknologi Sepuluh Nopember Jl. Arief Rahman Hakim, Surabaya 60111 (Indonesia); Department of Physics, Faculty of Mathematics and Natural Sciences Semarang State University Jl. Raya Sekaran GunungPati, Semarang 50221 (Indonesia); Suud, Fikriyatul Azizah; Darminto,; Triwikantoro,; Zainuri, Mochamad; Pratapa, Suminar, E-mail: suminar-pratapa@physics.its.ac.id [Department of Physics, Faculty of Mathematics and Natural Sciences Institut Teknologi Sepuluh Nopember Jl. Arief Rahman Hakim, Surabaya 60111 (Indonesia)

    2016-02-08

    Nano-forsterite powder with natural silica sand and magnesium powder as the raw materials have been succesfully synthesized. The silica sand was purified followed by a coprecipitation process to obtain colloidal silica. The magnesium powder was dissolved in a chloric acid solution to obtain MgCl{sub 2} solution. The nanoforsterite powder was synthesised using a sol-gel method which included the mixing the colloidal silica and the MgCl{sub 2} solution with various aging and filtering processes. The samples were dried at 100 °C using a hot plate and then the dried powders were calcinated at 900 °C for 2 hours. The samples were characetised for their elements and phase compositions using X-ray Flourescence (XRF) and X-ray Diffraction (XRD) methods, respectively. The diffraction data were qualitatively analyzed using Match!2 software and quantitatively using Rietica software. The crystallite size was verified using Transmission Electron Microscopy (TEM). Results of XRD data analysis showed that the forsterite content reached up to 90.5% wt. The TEM average crystallite size was approximately 53(6) nm.

  7. Chemical interactions of aluminum with aqueous silica at 25 degrees Celsius

    Science.gov (United States)

    Hem, John David; Roberson, C.E.; Lind, Carol J.; Polxer, W.L.

    1973-01-01

    Solutions containing from 10 -5 to 10 -2 moles per liter of aluminum and dissolved silica in various ratios were aged at pH levels between 4 and 10 at 25?C. A colloidal amorphous product having the composition of halloysite was produced in most solutions. It had a consistent and reversible equilibrium solubility equivalent to a standard free energy of formation of -8974 ? 1.0 kcal per mole for the formula A12Si2O5(OH)4. Some aging times were longer than 4 years, but most solutions gave consistent solubilities after only a few months of aging. Where silica concentrations were below about 10 -4 molar, microcrystalline gibbsite was formed below pH 6.0 and crystalline bayerite above pH 7.0, but only after much longer aging than was required for crystallization in silica-free solutions. Electron micrographs and diffraction patterns of the synthesized material indicate some crystallinity in the aluminosilicate, but no X-ray diffraction patterns could be obtained even in the material aged 4 years. Solubility relationships for solutions containing fluoride as well as silica and aluminum are explainable by using cryolite stabilities determined in previous work. Aluminum contents of 51 samples of water analyzed for other purposes are in reasonable agreement with the assumption of equilibrium with amorphous clay mineral species similar to the material synthesized in this work. Solubility calculations are summarized graphically for solutions of ionic strength of 0.01 and 0.10.

  8. Prompt atmospheric neutrino flux

    CERN Document Server

    Jeong, Yu Seon; Enberg, Rikard; Kim, C S; Reno, Mary Hall; Sarcevic, Ina; Stasto, Anna

    2016-01-01

    We evaluate the prompt atmospheric neutrino flux including nuclear correction and $B$ hadron contribution in the different frameworks: NLO perturbative QCD and dipole models. The nuclear effect is larger in the prompt neutrino flux than in the total charm production cross section, and it reduces the fluxes by $10\\% - 30\\%$ depending on the model. We also investigate the uncertainty using the QCD scales allowed by the charm cross section data from RHIC and LHC experiments.

  9. Enhanced antireflection properties of silica thin films via redox deposition and hot-water treatment

    Energy Technology Data Exchange (ETDEWEB)

    Chigane, Masaya; Hatanaka, Yoshiro; Shinagawa, Tsutomu [Department of Electronic Materials, Osaka Municipal Technical Research Institute, 1-6-50 Morinomiya, Joto-ku, Osaka 536-8553 (Japan)

    2010-06-15

    Silicon oxide (SiO{sub x}) thin film was deposited onto poly(ethylene terephthalate) substrate by the reduction of an aqueous solution containing ammonium hexafluorosilicate, dimethylamine borane and cetyltrimethylammonium bromide (CTAB). Post-deposition hot water treatment: immersion of the film in water at 333 K dissolved CTAB producing nanopores in silica (SiO{sub 2}) film and remarkably enhanced the antireflection property of the film: 0.1% at 550 nm of wavelength. The films before and after the treatment were compared via characterization by means of X-ray photoelectron spectroscopic depth profile, X-ray diffraction and transmission electron microscopy. The decrease of refractive index dispersion by the porous silica films, attributing to the low reflection, was verified by effective medium approximation analysis. (author)

  10. Black Carbon in Estuarine and Coastal Ocean Dissolved Organic Matter

    Science.gov (United States)

    Mannino, Antonio; Harvey, H. Rodger

    2003-01-01

    Black carbon (BC) in ultrafiltered high-molecular-weight DOM (UDOM) was measured in surface waters of Delaware Bay, Chesapeake Bay and the adjacent Atlantic Ocean (USA) to ascertain the importance of riverine and estuarine DOM as a source of BC to the ocean. BC comprised 5-72% of UDOM-C (27+/-l7%) and on average 8.9+/-6.5% of dissolved organic carbon (DOC) with higher values in the turbid region of the Delaware Estuary and lower yields in the river and coastal ocean. The spatial and seasonal distributions of BC along the salinity gradient of Delaware Bay suggest that the higher levels of BC in surface water UDOM originated from localized sources, possibly from atmospheric deposition or released from resuspended sediments. Black carbon comprised 4 to 7% of the DOC in the coastal Atlantic Ocean, revealing that river-estuary systems are important exporters of colloidal BC to the ocean. The annual flux of BC from Delaware Bay UDOM to the Atlantic Ocean was estimated at 2.4x10(exp 10) g BC yr(exp -1). The global river flux of BC through DOM to the ocean could be on the order of 5.5x1O(exp 12)g BC yr (exp -1). These results support the hypothesis that the DOC pool is the intermediate reservoir in which BC ages prior to sedimentary deposition.

  11. Video Meteor Fluxes

    Science.gov (United States)

    Campbell-Brown, M. D.; Braid, D.

    2011-01-01

    The flux of meteoroids, or number of meteoroids per unit area per unit time, is critical for calibrating models of meteoroid stream formation and for estimating the hazard to spacecraft from shower and sporadic meteors. Although observations of meteors in the millimetre to centimetre size range are common, flux measurements (particularly for sporadic meteors, which make up the majority of meteoroid flux) are less so. It is necessary to know the collecting area and collection time for a given set of observations, and to correct for observing biases and the sensitivity of the system. Previous measurements of sporadic fluxes are summarized in Figure 1; the values are given as a total number of meteoroids striking the earth in one year to a given limiting mass. The Gr n et al. (1985) flux model is included in the figure for reference. Fluxes for sporadic meteoroids impacting the Earth have been calculated for objects in the centimeter size range using Super-Schmidt observations (Hawkins & Upton, 1958); this study used about 300 meteors, and used only the physical area of overlap of the cameras at 90 km to calculate the flux, corrected for angular speed of meteors, since a large angular speed reduces the maximum brightness of the meteor on the film, and radiant elevation, which takes into account the geometric reduction in flux when the meteors are not perpendicular to the horizontal. They bring up corrections for both partial trails (which tends to increase the collecting area) and incomplete overlap at heights other than 90 km (which tends to decrease it) as effects that will affect the flux, but estimated that the two effects cancelled one another. Halliday et al. (1984) calculated the flux of meteorite-dropping fireballs with fragment masses greater than 50 g, over the physical area of sky accessible to the MORP fireball cameras, counting only observations in clear weather. In the micron size range, LDEF measurements of small craters on spacecraft have been used to

  12. Active and passive silica waveguide integration

    DEFF Research Database (Denmark)

    Hübner, Jörg; Guldberg-Kjær, Søren Andreas

    2001-01-01

    in existing and future networks without affecting the power budget of the system. Silica on silicon technology offers a unique possibility to selectively dope sections of the integrated circuit with erbium where amplification is desired. Some techniques for active/passive integration are reviewed and a silica...

  13. Chemical immobilisation of humic acid on silica

    NARCIS (Netherlands)

    Koopal, L.K.; Yang, Y.; Minnaard, A.J.; Theunissen, P.L.M.; Riemsdijk, W.H. van

    1998-01-01

    Immobilisation of purified Aldrich humic acid (PAHA) on aminopropyl silica and glutaraldehyde-activated aminopropyl silica has been investigated. In general the humic acid is bound to the solid by both physical and chemical bonds. The physically adsorbed HA can be released to a large extent at high

  14. Magnetic core-shell silica particles

    NARCIS (Netherlands)

    Claesson, E.M.

    2007-01-01

    This thesis deals with magnetic silica core-shell colloids and related functionalized silica structures. Synthesis routes have been developed and optimized. The physical properties of these colloids have been investigated, such as the magnetic dipole moment, dipolar structure formation and

  15. Chemical immobilisation of humic acid on silica

    NARCIS (Netherlands)

    Koopal, L.K.; Yang, Y.; Minnaard, A.J.; Theunissen, P.L.M.; Riemsdijk, W.H. van

    1998-01-01

    Immobilisation of purified Aldrich humic acid (PAHA) on aminopropyl silica and glutaraldehyde-activated aminopropyl silica has been investigated. In general the humic acid is bound to the solid by both physical and chemical bonds. The physically adsorbed HA can be released to a large extent at high

  16. Silica-Immobilized Enzyme Reactors (Postprint)

    Science.gov (United States)

    2007-09-01

    Non-solubilized UDPGT from rat liver microsomes was covalently immobilized to a func- tionalized silica support by Schiff base chemistry and a number...activity within a day. GADPH isolated from rabbit was covalently immobilized to a wide-pore silica support by glutaraldehyde activation and Schiff - base chemistry

  17. Magnetic core-shell silica particles

    NARCIS (Netherlands)

    Claesson, E.M.

    2007-01-01

    This thesis deals with magnetic silica core-shell colloids and related functionalized silica structures. Synthesis routes have been developed and optimized. The physical properties of these colloids have been investigated, such as the magnetic dipole moment, dipolar structure formation and rotationa

  18. Metal flux from hydrothermal vents increased by organic complexation

    Science.gov (United States)

    Sander, Sylvia G.; Koschinsky, Andrea

    2011-03-01

    Hydrothermal vents in the sea floor release large volumes of hot, metal-rich fluids into the deep ocean. Until recently, it was assumed that most of the metal released was incorporated into sulphide or oxide minerals, and that the net flux of most hydrothermally derived metals to the open ocean was negligible. However, mounting evidence suggests that organic compounds bind to and stabilize metals in hydrothermal fluids, increasing trace-metal flux to the global ocean. In situ measurements reveal that hydrothermally derived chromium, copper and iron bind to organic molecules on mixing with sea water. Geochemical model simulations based on data from two hydrothermal vent sites suggest that complexation significantly increases metal flux from hydrothermal systems. According to these simulations, hydrothermal fluids could account for 9% and 14% of the deep-ocean dissolved iron and copper budgets respectively. A similar role for organic complexation can be inferred for the hydrothermal fluxes of other metals, such as manganese and zinc.

  19. Characterizing In Situ Uranium and Groundwater Flux

    Science.gov (United States)

    Cho, J.; Newman, M. A.; Stucker, V.; Peacock, A.; Ranville, J.; Cabaniss, S.; Hatfield, K.; Annable, M. D.; Klammler, H.; Perminova, I. V.

    2010-12-01

    The goal of this project is to develop a new sensor that incorporates the field-tested concepts of the passive flux meter to provide direct in situ measures of uranium and groundwater fluxes. The sensor uses two sorbents and resident tracers to measure uranium flux and specific discharge directly; but, sensor principles and design should also apply to fluxes of other radionuclides. Flux measurements will assist with obtaining field-scale quantification of subsurface processes affecting uranium transport (e.g., advection) and transformation (e.g., uranium attenuation) and further advance conceptual and computational models for field scale simulations. Project efforts will expand our current understanding of how field-scale spatial variations in uranium fluxes and those for salient electron donor/acceptors, and groundwater are coupled to spatial variations in measured microbial biomass/community composition, effective field-scale uranium mass balances, attenuation, and stability. The new sensor uses an anion exchange resin to measure uranium fluxes and activated carbon with resident tracers to measure water fluxes. Several anion-exchange resins including Dowex 21K and 21K XLT, Purolite A500, and Lewatit S6328 were tested as sorbents for capturing uranium on the sensor and Lewatit S6328 was determined to be the most effective over the widest pH range. Four branched alcohols proved useful as resident tracers for measuring groundwater flows using activated carbon for both laboratory and field conditions. The flux sensor was redesigned to prevent the discharge of tracers to the environment, and the new design was tested in laboratory box aquifers and the field. Geochemical modeling of equilibrium speciation using Visual Minteq and an up-to-date thermodynamic data base suggested Ca-tricarbonato-uranyl complexes predominate under field conditions, while calculated uranyl ion activities were sensitive to changes in pH, dissolved inorganic carbon (DIC) and alkaline earth

  20. Electron heat flux instability

    Science.gov (United States)

    Saeed, Sundas; Sarfraz, M.; Yoon, P. H.; Lazar, M.; Qureshi, M. N. S.

    2017-02-01

    The heat flux instability is an electromagnetic mode excited by a relative drift between the protons and two-component core-halo electrons. The most prominent application may be in association with the solar wind where drifting electron velocity distributions are observed. The heat flux instability is somewhat analogous to the electrostatic Buneman or ion-acoustic instability driven by the net drift between the protons and bulk electrons, except that the heat flux instability operates in magnetized plasmas and possesses transverse electromagnetic polarization. The heat flux instability is also distinct from the electrostatic counterpart in that it requires two electron species with relative drifts with each other. In the literature, the heat flux instability is often called the 'whistler' heat flux instability, but it is actually polarized in the opposite sense to the whistler wave. This paper elucidates all of these fundamental plasma physical properties associated with the heat flux instability starting from a simple model, and gradually building up more complexity towards a solar wind-like distribution functions. It is found that the essential properties of the instability are already present in the cold counter-streaming electron model, and that the instability is absent if the protons are ignored. These instability characteristics are highly reminiscent of the electron firehose instability driven by excessive parallel temperature anisotropy, propagating in parallel direction with respect to the ambient magnetic field, except that the free energy source for the heat flux instability resides in the effective parallel pressure provided by the counter-streaming electrons.

  1. FABRICATION AND CHARACTERATION OF NANOPOROUS SILICA FILM

    Institute of Scientific and Technical Information of China (English)

    殷明志; 张良莹; 姚熹

    2003-01-01

    Colloidal silica sol is formed by a novel hydrolyzing procedure of tetraethyl-orthosilicate(TEOS) catalyzing with NH3*H2O in aqueous mediums. Glycerol, combining with the hydrolyzed intermediates of TEOS, controls growing of the silica particles; poly(vinyl-vinyl alcohol makes the colloidal silica sol with polymeric structure and spinning, thermal strain makes the gel silica film changed into a nanoporous structure with diameter ranging 50-150 nm. Morphologies of the nanoporous silica film have been characterized; the porosities (%) is 32-64; the average dielectric constant at 1MHz region is 2.0 and 2.1; the thermal conductivity is less than 0.8. Chemical mechanism of the sol-gel process is discussed.

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

    Science.gov (United States)

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

    2009-12-01

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

  3. Environmental Drivers of Benthic Flux Variation and Ecosystem Functioning in Salish Sea and Northeast Pacific Sediments.

    Directory of Open Access Journals (Sweden)

    Rénald Belley

    Full Text Available The upwelling of deep waters from the oxygen minimum zone in the Northeast Pacific from the continental slope to the shelf and into the Salish Sea during spring and summer offers a unique opportunity to study ecosystem functioning in the form of benthic fluxes along natural gradients. Using the ROV ROPOS we collected sediment cores from 10 sites in May and July 2011, and September 2013 to perform shipboard incubations and flux measurements. Specifically, we measured benthic fluxes of oxygen and nutrients to evaluate potential environmental drivers of benthic flux variation and ecosystem functioning along natural gradients of temperature and bottom water dissolved oxygen concentrations. The range of temperature and dissolved oxygen encountered across our study sites allowed us to apply a suite of multivariate analyses rarely used in flux studies to identify bottom water temperature as the primary environmental driver of benthic flux variation and organic matter remineralization. Redundancy analysis revealed that bottom water characteristics (temperature and dissolved oxygen, quality of organic matter (chl a:phaeo and C:N ratios and sediment characteristics (mean grain size and porosity explained 51.5% of benthic flux variation. Multivariate analyses identified significant spatial and temporal variation in benthic fluxes, demonstrating key differences between the Northeast Pacific and Salish Sea. Moreover, Northeast Pacific slope fluxes were generally lower than shelf fluxes. Spatial and temporal variation in benthic fluxes in the Salish Sea were driven primarily by differences in temperature and quality of organic matter on the seafloor following phytoplankton blooms. These results demonstrate the utility of multivariate approaches in differentiating among potential drivers of seafloor ecosystem functioning, and indicate that current and future predictive models of organic matter remineralization and ecosystem functioning of soft-muddy shelf and

  4. Export of Dissolved Organic Matter, Nutrients and Carbon from Himalayan River System in Central Nepal

    Science.gov (United States)

    Bhatt, M. P.

    2014-12-01

    Chemical weathering is a vital ecosystem process and plays a central role in regulation of global carbon cycles. Weathering from Himalayan landscape supply high amount of major ions, nutrients and suspended sediments to the oceans. Surface water samples were collected from sixteen stations at different altitude along the Langtnag-Narayani Himalayan river system in central Nepal on a monthly basis for one year. This study aims to investigate spatiotemporal variations of dissolved organic matter, nutrients and carbonic species and to evaluate their controlling factors within the basin. The fluxes of these species appeared several fold higher at low elevation than at mid mountains and high elevation Himalaya sites. Seasonality appeared to exert major control on concentrations and fluxes of major solutes along the drainage network. The highest export rate of chemical species corresponded to the monsoon season, followed by the ones corresponding to post-monsoon and pre-monsoon seasons. Carbonate has major control on the flux of major solutes within the basin. The export rate of dissolved organic carbon and total dissolved nitrogen were about three and seventeen times higher respectively at the Narayani basin than its headwater at Langtang basin within the high Himalaya. Nitrate and phosphate export rates in the Narayani basin were 5.07 and 0.34 tons km-2 yr-1 respectively which is several fold higher than the rates in the high Himalaya probably due to input from agricultural activities. The export of dissolved inorganic carbon from the Narayani basin was 101.87 tons km-2 yr-1 of which bicarbonate appeared to be the dominant fraction (94.9%) followed by carbonic acid (4.7%) and carbonate (0.4%). Partial pressure of carbon dioxide (pCO2) resulted under-saturated in the high elevation Himalayan basin and supersaturated at the low elevation Narayani basin. The concentration of pCO2 is considered to be an important factor for regulating weathering rates of any landscape.

  5. MOUTH DISSOLVING TABLETS: A FUTURE COMPACTION

    Directory of Open Access Journals (Sweden)

    Srivastava Saurabh

    2012-08-01

    Full Text Available An orally disintegrating tablet or mouth dissolving tablet (MDT is a drug dosage form available for a limited amount of over-the-counter (OTC and prescription medications. MDTs differ from traditional tablets in that they are designed to be dissolved on the tongue rather than swallowed whole. A variety of pharmaceutical research has been conducted to develop new dosage forms. Among the dosage forms developed to facilitate ease of medication, the mouth dissolving tablet (MDT is one of the most widely employed commercial products. As our society is becoming increasingly aged, the development of mouth dissolving tablets have been formulated for pediatric, geriatric, and bedridden patients and for active patients who are busy and travelling and may not have access to water. Such formulations provide an opportunity for product line extension in the many elderly persons will have difficulties in taking conventional oral dosage forms (viz., solutions, suspensions, tablets, and capsules because of hand tremors and dysphagia. Oral delivery is currently the gold standard in the pharmaceutical industry where it is regarded as the safest, most convenient and most economical method of drug delivery having the highest patient compliance. Recent development in fast disintegrating technology mainly works to improve the disintegration quality of these delicate dosage forms without affecting their integrity. This article focuses on the patented technologies available and the advances made so far in the field of fabrication of mouth dissolving tablets. Apart from the conventional methods of fabrication, this review also provides the detailed concept of some unique technologies like freeze drying, direct compression, spray drying, tablet molding, sublimation, fast dissolving films cotton candy process, along with their advantages and limitations.

  6. Peer reviewed: Characterizing aquatic dissolved organic matter

    Science.gov (United States)

    Leenheer, Jerry A.; Croué, Jean-Philippe

    2003-01-01

    Whether it causes aesthetic concerns such as color, taste, and odor; leads to the binding and transport of organic and inorganic contaminants; produces undesirable disinfection byproducts; provides sources and sinks for carbon; or mediates photochemical processes, the nature and properties of dissolved organic matter (DOM) in water are topics of significant environmental interest. DOM is also a major reactant in and product of biogeochemical processes in which the material serves as a carbon and energy source for biota and controls levels of dissolved oxygen, nitrogen, phosphorus, sulfur, numerous trace metals, and acidity.

  7. Kaolinite and Silica Dispersions in Low-Salinity Environments: Impact on a Water-in-Crude Oil Emulsion Stability

    Directory of Open Access Journals (Sweden)

    Vladimir Alvarado

    2011-10-01

    Full Text Available This research aims at providing evidence of particle suspension contributions to emulsion stability, which has been cited as a contributing factor in crude oil recovery by low-salinity waterflooding. Kaolinite and silica particle dispersions were characterized as functions of brine salinity. A reference aqueous phase, representing reservoir brine, was used and then diluted with distilled water to obtain brines at 10 and 100 times lower Total Dissolved Solid (TDS. Scanning Electron Microscope (SEM and X-ray Diffraction (XRD were used to examine at the morphology and composition of clays. The zeta potential and particle size distribution were also measured. Emulsions were prepared by mixing a crude oil with brine, with and without dispersed particles to investigate emulsion stability. The clay zeta potential as a function of pH was used to investigate the effect of particle charge on emulsion stability. The stability was determined through bottle tests and optical microscopy. Results show that both kaolinite and silica promote emulsion stability. Also, kaolinite, roughly 1 mm in size, stabilizes emulsions better than larger clay particles. Silica particles of larger size (5 µm yielded more stable emulsions than smaller silica particles do. Test results show that clay particles with zero point of charge (ZPC at low pH become less effective at stabilizing emulsions, while silica stabilizes emulsions better at ZPC. These result shed light on emulsion stabilization in low-salinity waterflooding.

  8. SYNTHESIS AND CHARACTERIZATION OF HIERARCHICALLY POROUS SILICA WITH POPLAR TISSUE AS TEMPLATE WITH ASSISTANCE OF SUPERCRITICAL CO2

    Directory of Open Access Journals (Sweden)

    Wei Ni

    2008-05-01

    Full Text Available Hierarchically porous silica samples, ranging from mesopores to macropores, were prepared by “nanoscale casting using supercritical (SC fluids” (NC-SCF technology and bionics, achieving a biomineralization process in an environmentally friendly and efficient way. These wood-templated SiO2 samples, having special hierarchical pore sizes from 3.3 nm up to 50 μm, were obtained with SC-CO2 precursor solution by a wood-silication method. For this method, the precursor, tetraethyl orthosilicate (TEOS, was dissolved in SC-CO2 and impregnated into poplar tissue cells using SC-CO2 as a mass carrier. After removal of the wood template by calcination in air at suitable temperatures, the porous silica was obtained. The effects of CO2 pressure and precursor concentration on the impregnating ratio were studied, and the products were characterized. SEM experimental results showed that the obtained silica had the same external and internal structures of the original wood. XRD and N2 absorption-desorption results indicated that the silica was amorphous but crystallized with the calcination temperature up to 1000℃, and had a preferable BET surface area being up to 469 m2/g (600℃. So this work provides a simple and timesaving route to obtain and control the special microstructure of silica with the aid of a wood template in supercritical CO2.

  9. Significance of silica in identifying the processes affecting groundwater chemistry in parts of Kali watershed, Central Ganga Plain, India

    Science.gov (United States)

    Khan, Arina; Umar, Rashid; Khan, Haris Hasan

    2015-03-01

    Chemical geothermometry using silica was employed in the present study to estimate the sub-surface groundwater temperature and the corresponding depth of the groundwater in parts of Kali watershed in Bulandshahr and Aligarh district. 42 groundwater samples each were collected from borewells during pre-monsoon and post-monsoon season 2012 and analysed for all major ions and silica. Silica values in the area range from 18.72 to 50.64 mg/l in May 2012 and from 18.89 to 52.23 mg/l in November 2012. Chalcedony temperature >60 °C was deduced for five different locations in each season, which corresponds to a depth of more than 1,000 metres. Spatial variation of silica shows high values along a considerable stretch of River Kali, during pre-monsoon season. Relationship of silica with Total Dissolved Solids and Chloride was established to infer the role of geogenic and anthropogenic processes in solute acquisition. It was found that both water-rock interaction and anthropogenic influences are responsible for the observed water chemistry.

  10. Sorption Characteristics of Rare Earth Element Eu3+ onto Silica-Water Interfaces Studied by Fluorescence Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    Yin Xiulan; Hu Ping; Li Dien

    2004-01-01

    The sorption of Eu species onto nano-size silica-water interfaces was investigated using fluorescence spectroscopy for Ph ranges of 1-8.5 and an initial Eu concentration (Ceu) of 2×10-4 M. The sorption rate of Eu was initially low, but significantly increased at Ph>4. The sorption density of Eu species on a silica surface was ~1.58×10-7 mol/m2 when the dissolved Eu species were completely sorbed onto silica-water interfaces at Ph=~5.8. The sorbed Eu species at Ph<6 is aquo Eu3+, which is sorbed onto silica-water interfaces as an outer-sphere complex at Ph<5, but may be sorbed as an inner-sphere bidentate complex at 5silica-water interfaces as inner-sphere bidentate complexes.

  11. Surface complexation model for strontium sorption to amorphous silica and goethite

    Directory of Open Access Journals (Sweden)

    Criscenti Louise J

    2008-01-01

    Full Text Available Abstract Strontium sorption to amorphous silica and goethite was measured as a function of pH and dissolved strontium and carbonate concentrations at 25°C. Strontium sorption gradually increases from 0 to 100% from pH 6 to 10 for both phases and requires multiple outer-sphere surface complexes to fit the data. All data are modeled using the triple layer model and the site-occupancy standard state; unless stated otherwise all strontium complexes are mononuclear. Strontium sorption to amorphous silica in the presence and absence of dissolved carbonate can be fit with tetradentate Sr2+ and SrOH+ complexes on the β-plane and a monodentate Sr2+complex on the diffuse plane to account for strontium sorption at low ionic strength. Strontium sorption to goethite in the absence of dissolved carbonate can be fit with monodentate and tetradentate SrOH+ complexes and a tetradentate binuclear Sr2+ species on the β-plane. The binuclear complex is needed to account for enhanced sorption at hgh strontium surface loadings. In the presence of dissolved carbonate additional monodentate Sr2+ and SrOH+ carbonate surface complexes on the β-plane are needed to fit strontium sorption to goethite. Modeling strontium sorption as outer-sphere complexes is consistent with quantitative analysis of extended X-ray absorption fine structure (EXAFS on selected sorption samples that show a single first shell of oxygen atoms around strontium indicating hydrated surface complexes at the amorphous silica and goethite surfaces. Strontium surface complexation equilibrium constants determined in this study combined with other alkaline earth surface complexation constants are used to recalibrate a predictive model based on Born solvation and crystal-chemistry theory. The model is accurate to about 0.7 log K units. More studies are needed to determine the dependence of alkaline earth sorption on ionic strength and dissolved carbonate and sulfate concentrations for the development of

  12. Particulate Matter Fluxes in Cuenca Alfonso During 2002-2005

    Science.gov (United States)

    Silverberg, N.; Aguirre-Bahena, F.

    2007-05-01

    Time-series sediment trap data were collected between 2002 and 2005 from Cuenca Alfonso, a 400m-deep basin in Bahía de La Paz, a large embayment on the southwestern coast of the Gulf of California. Despite the lack of significant land drainage in this semi-dessert environment, terrigenous material, probably wind-born, dominates the sinking particulate matter. Peak lithogenic fluxes appear to be associated with higher frequencies of wind gusts stronger than 5 ms-1. Total mass flux fluctuated from week to week, and between years, averaging 277 gm-2y-1, essentially the same as radiometrically-determined accumulation rates of about 0.4 mmy-1 in cores of the underlying sediment. In 2003, the passage of 2 hurricanes induced high winds and flash flooding and the total mass flux offshore remained very high for two weeks following each event. This unusual sedimentation was equivalent to that of a full year without hurricanes and such events may account for some of the laminations found in cores. During most of 2005, on the other hand, sedimentation rates were lower than average. Although fluxes of all components tended to be highest during late fall and early winter, biogenic fluxes displayed peaks during all seasons of the year in Cuenca Alfonso. This is in contrast to the strong seasonal alternation between terrigenous sedimentation and diatom blooms observed in Guaymas Basin in the central Gulf. Furthermore, calcium carbonate dominated over biogenic silica within the marine component. Average annual fluxes of CaCO3, biogenic silica and POC were 52.5, 32.5 and 13.9 gm-2y-1, respectively.

  13. Effects of long-term land use change on dissolved carbon characteristics in the permafrost streams of northeast China.

    Science.gov (United States)

    Guo, Yuedong; Song, Changchun; Wan, Zhongmei; Tan, Wenwen; Lu, Yongzheng; Qiao, Tianhua

    2014-11-01

    Permafrost soils act as large sinks of organic carbon but are highly sensitive to interference such as changes in land use, which can greatly influence dissolved carbon loads in streams. This study examines the effects of long-term land reclamation on seasonal concentrations of dissolved carbons in the upper reaches of the Nenjiang River, northeast China. A comparison of streams in natural and agricultural systems shows that the dissolved organic carbon (DOC) concentration is much lower in the agricultural stream (AG) than in the two natural streams (WAF, wetland dominated; FR, forest dominated), suggesting that land use change is associated with reduced DOC exporting capacity. Moreover, the fluorescence indexes and the ratio of dissolved carbon to nitrogen also differ greatly between the natural and agricultural streams, indicating that the chemical characteristics and the origin of the DOC released from the whole reaches are also altered to some extent. Importantly, the exporting concentration of dissolved inorganic carbon (DIC) and its proportion of total dissolved carbon (TDC) substantially increase following land reclamation, which would largely alter the carbon cycling processes in the downstream fluvial system. Although the strong association between the stream discharge and the DOC concentration was unchanged, the reduction in total soil organic carbon following land reclamation led to remarkable decline of the total flux and exporting coefficient of the dissolved carbons. The results suggest that dissolved carbons in permafrost streams have been greatly affected by changes in land use since the 1970s, and the changes in the concentration and chemical characteristics of dissolved carbons will last until the alteration in both the traditional agriculture pattern and the persistent reclamation activities.

  14. Capture of Co(II) from its aqueous EDTA-chelate by DTPA-modified silica gel and chitosan.

    Science.gov (United States)

    Repo, Eveliina; Malinen, Leena; Koivula, Risto; Harjula, Risto; Sillanpää, Mika

    2011-03-15

    The adsorption of Co(II) by diethylenetriaminepentaacetic acid (DTPA)-modified silica gel and chitosan in the presence of EDTA and other interfering species was studied. Co(II) removal ranged from 93% to 96% from the solutions where Co(II) was totally chelated by EDTA. The amount of oxalate or Fe(II) did not affect the adsorption of Co(II) in the case of DTPA-chitosan. However, increasing the amount of oxalate enhanced the adsorption performance of DTPA-silica gel, probably due to the formation of new active sites on the silica gel surface. DTPA-chitosan was also effective in simulated decontamination solutions. For DTPA-silica gel, the rate of adsorption of free Co(II) was controlled by pore diffusion, but the rate of adsorption of Co(II)EDTA was controlled by the surface chelation reaction, which was attributed to the inhibited diffusion of Co(II)EDTA inside the silica gel mesopores. However, the macroporous structure of DTPA-chitosan enabled pore diffusion of both Co(II) and Co(II)EDTA. The equilibrium isotherms of DTPA-silica gel were best described by a BiLangmuir model, in which there are two different adsorption sites on the silica gel surface assigned to different speciations of DTPA. For DTPA-chitosan, the data fit best with a Sips model, which indicates system heterogeneity. Finally, measurements with capillary electrophoresis showed an increase in dissolved EDTA during adsorption, demonstrating the ability of DTPA-modified adsorbents to release Co(II) from its EDTA chelate. This promising result can provide a basis for applying the studied materials to the treatment of water effluents containing Co(II) chelated by EDTA by a simple one-step adsorption process. Copyright © 2011 Elsevier B.V. All rights reserved.

  15. Hydrologically transported dissolved organic carbon influences soil respiration in a tropical rainforest

    Science.gov (United States)

    Zhou, Wen-Jun; Lu, Hua-Zheng; Zhang, Yi-Ping; Sha, Li-Qing; Schaefer, Douglas Allen; Song, Qing-Hai; Deng, Yun; Deng, Xiao-Bao

    2016-10-01

    To better understand the effect of dissolved organic carbon (DOC) transported by hydrological processes (rainfall, throughfall, litter leachate, and surface soil water; 0-20 cm) on soil respiration in tropical rainforests, we detected the DOC flux in rainfall, throughfall, litter leachate, and surface soil water (0-20 cm), compared the seasonality of δ13CDOC in each hydrological process, and δ13C in leaves, litter, and surface soil, and analysed the throughfall, litter leachate, and surface soil water (0-20 cm) effect on soil respiration in a tropical rainforest in Xishuangbanna, south-west China. Results showed that the surface soil intercepted 94.4 ± 1.2 % of the annual litter leachate DOC flux and is a sink for DOC. The throughfall and litter leachate DOC fluxes amounted to 6.81 and 7.23 % of the net ecosystem exchange respectively, indicating that the DOC flux through hydrological processes is an important component of the carbon budget, and may be an important link between hydrological processes and soil respiration in a tropical rainforest. Even the variability in soil respiration is more dependent on the hydrologically transported water than DOC flux insignificantly, soil temperature, and soil-water content (at 0-20 cm). The difference in δ13C between the soil, soil water (at 0-20 cm), throughfall, and litter leachate indicated that DOC is transformed in the surface soil and decreased the sensitivity indices of soil respiration of DOC flux to water flux, which suggests that soil respiration is more sensitive to the DOC flux in hydrological processes, especially the soil-water DOC flux, than to soil temperature or soil moisture.

  16. Metal-silica sol-gel materials

    Science.gov (United States)

    Stiegman, Albert E. (Inventor)

    2002-01-01

    The present invention relates to a single phase metal-silica sol-gel glass formed by the co-condensation of a transition metal with silicon atoms where the metal atoms are uniformly distributed within the sol-gel glass as individual metal centers. Any transition metal may be used in the sol-gel glasses. The present invention also relates to sensor materials where the sensor material is formed using the single phase metal-silica sol-gel glasses. The sensor materials may be in the form of a thin film or may be attached to an optical fiber. The present invention also relates to a method of sensing chemicals using the chemical sensors by monitoring the chromatic change of the metal-silica sol-gel glass when the chemical binds to the sensor. The present invention also relates to oxidation catalysts where a metal-silica sol-gel glass catalyzes the reaction. The present invention also relates to a method of performing oxidation reactions using the metal-silica sol-gel glasses. The present invention also relates to organopolymer metal-silica sol-gel composites where the pores of the metal-silica sol-gel glasses are filled with an organic polymer polymerized by the sol-gel glass.

  17. Light-Induced Surface Patterning of Silica.

    Science.gov (United States)

    Kang, Hong Suk; Lee, Seungwoo; Choi, Jaeho; Lee, Hongkyung; Park, Jung-Ki; Kim, Hee-Tak

    2015-10-27

    Manipulating the size and shape of silica precursor patterns using simple far-field light irradiation and transforming such reconfigured structures into inorganic silica patterns by pyrolytic conversion are demonstrated. The key concept of our work is the use of an azobenzene incorporated silica precursor (herein, we refer to this material as azo-silane composite) as ink in a micromolding process. The moving direction of azo-silane composite is parallel to light polarization direction; in addition, the amount of azo-silane composite movement can be precisely determined by controlling light irradiation time. By exploiting this peculiar phenomenon, azo-silane composite patterns produced using the micromolding technique are arbitrarily manipulated to obtain various structural features including high-resolution size or sophisticated shape. The photoreconfigured patterns formed with azo-silane composites are then converted into pure silica patterns through pyrolytic conversion. The pyrolytic converted silica patterns are uniformly formed over a large area, ensuring crack-free formation and providing high structural fidelity. Therefore, this optical manipulation technique, in conjunction with the pyrolytic conversion process, opens a promising route to the design of silica patterns with finely tuned structural features in terms of size and shape. This platform for designing silica structures has significant value in various nanotechnology fields including micro/nanofluidic channel for lab-on-a-chip devices, transparent superhydrophobic surfaces, and optoelectronic devices.

  18. Impact of sediment-seawater cation exchange on Himalayan chemical weathering fluxes

    Science.gov (United States)

    Lupker, Maarten; France-Lanord, Christian; Lartiges, Bruno

    2016-08-01

    Continental-scale chemical weathering budgets are commonly assessed based on the flux of dissolved elements carried by large rivers to the oceans. However, the interaction between sediments and seawater in estuaries can lead to additional cation exchange fluxes that have been very poorly constrained so far. We constrained the magnitude of cation exchange fluxes from the Ganga-Brahmaputra river system based on cation exchange capacity (CEC) measurements of riverine sediments. CEC values of sediments are variable throughout the river water column as a result of hydrological sorting of minerals with depth that control grain sizes and surface area. The average CEC of the integrated sediment load of the Ganga-Brahmaputra is estimated ca. 6.5 meq 100 g-1. The cationic charge of sediments in the river is dominated by bivalent ions Ca2+ (76 %) and Mg2+ (16 %) followed by monovalent K+ (6 %) and Na+ (2 %), and the relative proportion of these ions is constant among all samples and both rivers. Assuming a total exchange of exchangeable Ca2+ for marine Na+ yields a maximal additional Ca2+ flux of 28 × 109 mol yr-1 of calcium to the ocean, which represents an increase of ca. 6 % of the actual river dissolved Ca2+ flux. In the more likely event that only a fraction of the adsorbed riverine Ca2+ is exchanged, not only for marine Na+ but also Mg2+ and K+, estuarine cation exchange for the Ganga-Brahmaputra is responsible for an additional Ca2+ flux of 23 × 109 mol yr-1, while ca. 27 × 109 mol yr-1 of Na+, 8 × 109 mol yr-1 of Mg2+ and 4 × 109 mol yr-1 of K+ are re-absorbed in the estuaries. This represents an additional riverine Ca2+ flux to the ocean of 5 % compared to the measured dissolved flux. About 15 % of the dissolved Na+ flux, 8 % of the dissolved K+ flux and 4 % of the Mg2+ are reabsorbed by the sediments in the estuaries. The impact of estuarine sediment-seawater cation exchange appears to be limited when evaluated in the context of the long-term carbon cycle and

  19. FLUORESCENCE IN DISSOLVED FRACTIONS OF HUMAN ENAMEL

    NARCIS (Netherlands)

    HAFSTROMBJORKMAN, U; SUNDSTROM, F; TENBOSCH, JJ

    Fluorescence induced by laser light is useful in early detection of enamel caries. The present work studied the fluorescence emission pattern in dissolved human enamel and in different molecular weight fractions obtained after gel chromatography or dialysis followed by ultrafiltration. For

  20. Modeling Fish Growth in Low Dissolved Oxygen

    Science.gov (United States)

    Neilan, Rachael Miller

    2013-01-01

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

  1. Reconstruction of Spent Fuel Dissolver Critical Assembly

    Institute of Scientific and Technical Information of China (English)

    LIANG; Shu-hong; ZHU; Qing-fu; ZHOU; Qi; QUAN; Yan-hui; YANG; Li-jun; LUO; Huang-da; LIU; Yang; ZHANG; Wei; ZHOU; Xiao-ping; LIU; Dong-hai

    2015-01-01

    During the twelfth Five-Year period,Reactor Physics Laboratory has taken on the research item about spent fuel dissolver critical experiment in nuclear power development project,which should be accomplished by using the uranium solution nuclear critical safety experiment device.Due to the differences of experimental content

  2. Photoluminescent Detection of Dissolved Underwater Trace Explosives

    OpenAIRE

    2010-01-01

    A portable, rapid, and economical method for in situ trace explosive detection in aqueous solutions was demonstrated using photoluminescence. Using europium/thenoyltrifluoroacetone as the reagent, dissolved nitroglycerin was fluorescently tagged and detected in seawater solutions without sample preparation, drying, or preconcentration. The chemical method was developed in a laboratory setting and demonstrated in a flow-through configuration using lightweight, inexpensive, commercial component...

  3. Why do Worker-Firm Matches Dissolve?

    NARCIS (Netherlands)

    Gielen, A. C.; van Ours, J.C.

    2006-01-01

    In a dynamic labor market worker-firm matches dissolve frequently causing workers to separate and firms to look for replacements.A separation may be initiated by the worker (a quit) or the firm (a layoff), or may result from a joint decision.A dissolution of a worker-firm match may be ineffcient if

  4. Dissolved aluminium in the Southern Ocean

    NARCIS (Netherlands)

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

    2011-01-01

    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 th

  5. Dissolved petroleum hydrocarbons in the Andaman Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Topgi, R.S.; Noronha, R.J.; Fondekar, S.P.

    Mean dissolved petroleum hydrocarbons, measured using UV-spectrophotometry, at 0 and 10m were 51 plus or minus 1 and 55 plus or minus 1.2 mu g/litre respectively; range of variation being between 28 and 83 mu g/litre. Very little difference...

  6. Total dissolved carbohydrate in Mahi river estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Bhosle, N.B.; Rokade, M.A.; Zingde, M.D.

    Total dissolved carbohydrate varied from 4.37-15 mg l-1 and 3.71-15.95 mg l-1 in the surface and bottom samples respectively. Highest concentration of carbohydrate was observed at station 1 which decreased downward upto Station 6 which showed...

  7. TRIMETHYLSILYLATED SILICA AS RHEOLOGY MODIFIER FOR SILICONE RESINS

    Institute of Scientific and Technical Information of China (English)

    Wei Huang; Ying Huang; Yunzhao Yu

    2000-01-01

    Trimethylsilylated silica was synthesized through hydrolytic condensation of tetraethoxysilane followed by trimethylsilylation. Rheological properties of the silicone resin with trimethylsilylated silica as modifier were studied. It turned out that the particle size of silica was important to the rheological behavior of the modified resin. Trimethylsilylated silica of medium particle size shows the strongest tendency of forming physical network in the resin.

  8. Controlled silica synthesis inspired by diatom silicon biomineralization

    NARCIS (Netherlands)

    Vrieling, EG; Sun, QY; Beelen, TPM; Hazelaar, S; Gieskes, WWC; van Santen, RA; Sommerdijk, NAJM

    2005-01-01

    Silica becomes increasingly used in chemical, pharmaceutical, and (nano)technological processes', resulting in an increased demand for well-defined silicas and silica-based materials. The production of highly structured silica from cheap starting materials and under ambient conditions, which is a ta

  9. Controlled silica synthesis inspired by diatom silicon biomineralization

    NARCIS (Netherlands)

    Vrieling, EG; Sun, QY; Beelen, TPM; Hazelaar, S; Gieskes, WWC; van Santen, RA; Sommerdijk, NAJM

    Silica becomes increasingly used in chemical, pharmaceutical, and (nano)technological processes', resulting in an increased demand for well-defined silicas and silica-based materials. The production of highly structured silica from cheap starting materials and under ambient conditions, which is a

  10. Net Ecosystem Carbon Flux

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Net Ecosystem Carbon Flux is defined as the year-over-year change in Total Ecosystem Carbon Stock, or the net rate of carbon exchange between an ecosystem and the...

  11. Aeronet Solar Flux

    Data.gov (United States)

    National Aeronautics and Space Administration — SolRad-Net (Solar Radiation Network) is an established network of ground-based sensors providing high-frequency solar flux measurements in quasi-realtime to the...

  12. Flux in Tallinn

    Index Scriptorium Estoniae

    2004-01-01

    Rahvusvahelise elektroonilise kunsti sümpoosioni ISEA2004 klubiõhtu "Flux in Tallinn" klubis Bon Bon. Eestit esindasid Ropotator, Ars Intel Inc., Urmas Puhkan, Joel Tammik, Taavi Tulev (pseud. Wochtzchee). Klubiõhtu koordinaator Andres Lõo

  13. Flux in Tallinn

    Index Scriptorium Estoniae

    2004-01-01

    Rahvusvahelise elektroonilise kunsti sümpoosioni ISEA2004 klubiõhtu "Flux in Tallinn" klubis Bon Bon. Eestit esindasid Ropotator, Ars Intel Inc., Urmas Puhkan, Joel Tammik, Taavi Tulev (pseud. Wochtzchee). Klubiõhtu koordinaator Andres Lõo

  14. Nitrous Oxide Flux

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Nitrous Oxide (N20) flux is the net rate of nitrous oxide exchange between an ecosystem and the atmosphere. Data of this variable were generated by the USGS...

  15. Dissolved nitrogen in rivers: comparing pristine and impacted regions of Brazil

    Directory of Open Access Journals (Sweden)

    LA Martinelli

    Full Text Available Riverine nitrogen distribution is increasingly controlled by anthropogenic activities in their watersheds, regardless of spatial scale, climate, and geographical zone. Consequently, modelling efforts to predict the export of nitrogen from rivers worldwide have used attributes such as population density, land use, urbanization and sanitation. These models have greatly enhanced our understanding of the sources and fate of nitrogen added to terrestrial systems and transported to rivers and streams, especially for developed countries of the North temperate zone. However, much of the world's population lives in developing countries of the tropics, where the effects of human activities on riverine N exports are still poorly understood. In an effort to close this gap, we compare riverine nitrogen data from 32 Brazilian rivers draining two contrasting regions in this tropical country in terms of economic development - the State of São Paulo and the Amazon. Our data include nitrogen in different dissolved forms, such as Dissolved Inorganic Nitrogen (DIN and Dissolved Organic Nitrogen (DON. The results show that nitrogen concentrations decreased as river runoff increased in both study areas, and that concentrations were significantly higher in rivers draining the most economically developed region. The relationships between nitrogen concentrations and fluxes with demographic parameters such as population density were also determined and compared to those in temperate systems. In contrast to temperate watersheds, we found that nitrogen fluxes increased only after population densities were higher than 10 individuals per km².

  16. Carbon Dioxide Flux Measurement Systems

    Data.gov (United States)

    Oak Ridge National Laboratory — The Southern Great Plains (SGP) carbon dioxide flux (CO2 flux) measurement systems provide half-hour average fluxes of CO2, H2O (latent heat), and sensible heat. The...

  17. Flux Emergence (Theory)

    Science.gov (United States)

    Cheung, Mark C. M.; Isobe, Hiroaki

    2014-12-01

    Magnetic flux emergence from the solar convection zone into the overlying atmosphere is the driver of a diverse range of phenomena associated with solar activity. In this article, we introduce theoretical concepts central to the study of flux emergence and discuss how the inclusion of different physical effects (e.g., magnetic buoyancy, magnetoconvection, reconnection, magnetic twist, interaction with ambient field) in models impact the evolution of the emerging field and plasma.

  18. Theoretical magnetic flux emergence

    OpenAIRE

    MacTaggart, David

    2011-01-01

    Magnetic flux emergence is the subject of how magnetic fields from the solar interior can rise and expand into the atmosphere to produce active regions. It is the link that joins dynamics in the convection zone with dynamics in the atmosphere. In this thesis, we study many aspects of magnetic flux emergence through mathematical modelling and computer simulations. Our primary aim is to understand the key physical processes that lie behind emergence. The first chapter intro...

  19. Flux Emergence (Theory

    Directory of Open Access Journals (Sweden)

    Mark C. M. Cheung

    2014-07-01

    Full Text Available Magnetic flux emergence from the solar convection zone into the overlying atmosphere is the driver of a diverse range of phenomena associated with solar activity. In this article, we introduce theoretical concepts central to the study of flux emergence and discuss how the inclusion of different physical effects (e.g., magnetic buoyancy, magnetoconvection, reconnection, magnetic twist, interaction with ambient field in models impact the evolution of the emerging field and plasma.

  20. Methane and Carbon Dioxide Concentrations and Fluxes in Amazon Floodplains

    Science.gov (United States)

    Melack, J. M.; MacIntyre, S.; Forsberg, B.; Barbosa, P.; Amaral, J. H.

    2016-12-01

    Field studies on the central Amazon floodplain in representative aquatic habitats (open water, flooded forests, floating macrophytes) combine measurements of methane and carbon dioxide concentrations and fluxes to the atmosphere over diel and seasonal times with deployment of meteorological sensors and high-resolution thermistors and dissolved oxygen sondes. A cavity ringdown spectrometer is used to determine gas concentrations, and floating chambers and bubble collectors are used to measure fluxes. To further understand fluxes, we measured turbulence as rate of dissipation of turbulent kinetic energy based on microstructure profiling. These results allow calculations of vertical mixing within the water column and of air-water exchanges using surface renewal models. Methane and carbon dioxide fluxes varied as a function of season, habitat and water depth. High CO2 fluxes at high water are related to high pCO2; low pCO2 levels at low water result from increased phytoplankton uptake. CO2 fluxes are highest at turbulent open water sites, and pCO2 is highest in macrophyte beds. Fluxes and pCH4 are high in macrophyte beds.

  1. O on the Crystallization Behavior of Lime-Alumina-Based Mold Flux for Casting High-Al Steels

    Science.gov (United States)

    Lu, Boxun; Chen, Kun; Wang, Wanlin; Jiang, Binbin

    2014-08-01

    With the development of advanced high strength steel (AHSS), a large amount of aluminum was added into steels. The reaction between aluminum in the molten steel and silica based mold flux in the continuous-casting process would tend to cause a series of problems and influence the quality of slabs. To solve the above problems caused by the slag-steel reaction, nonreactive lime-alumina-based mold flux system has been proposed. In this article, the effect of Li2O and Na2O on the crystallization behavior of the lime-alumina-silica-based mold flux has been studied by using the single hot thermocouple technology (SHTT) and double hot thermocouple technology (DHTT). The results indicated that Li2O and Na2O in the above mold flux system play different roles as they behaved in traditional lime-silica based mold flux, which would tend to inhibit general mold flux crystallization by lowering the initial crystallization temperature and increasing incubation time, especially in the high-temperature region. However, when their content exceeds a critical value, the crystallization process of mold fluxes in low temperature zone would be greatly accelerated by the new phase formation of LiAlO2 and Na x Al y Si z O4 crystals, respectively. The crystalline phases precipitated in all samples during the experiments are discussed in the article.

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

    DEFF Research Database (Denmark)

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

    1997-01-01

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

  3. Interfacial interaction between the epoxidized natural rubber and silica in natural rubber/silica composites

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tiwen [College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Jia, Zhixin, E-mail: zxjia@scut.edu.cn [College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Luo, Yuanfang; Jia, Demin [College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Peng, Zheng [Agricultural Product Processing Research Institute, Chinese Academy of Tropical Agriculture Sciences, Zhanjiang 524001 (China)

    2015-02-15

    Highlights: • Substantiate the ring open reaction between Si-OH of silica and epoxy groups of ENR. • ENR can act as a bridge between NR and silica to enhance the interfacial interaction. • As a modifier, ENR gets the potential to be used in the tread of green tire for improving the wet skid resistance apparently. - Abstract: The epoxidized natural rubber (ENR) as an interfacial modifier was used to improve the mechanical and dynamical mechanical properties of NR/silica composites. In order to reveal the interaction mechanism between ENR and silica, the ENR/Silica model compound was prepared by using an open mill and the interfacial interaction of ENR with silica was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and stress–strain testing. The results indicated that the ring-opening reaction occurs between the epoxy groups of ENR chains and Si-OH groups on the silica surfaces and the covalent bonds are formed between two phases, which can improve the dispersion of silica in the rubber matrix and enhance the interfacial combination between rubber and silica. The ring-opening reaction occurs not only in vulcanization process but also in mixing process, meanwhile, the latter seems to be more important due to the simultaneous effects of mechanical force and temperature.

  4. Fungus-mediated biotransformation of amorphous silica in rice husk to nanocrystalline silica.

    Science.gov (United States)

    Bansal, Vipul; Ahmad, Absar; Sastry, Murali

    2006-11-01

    Rice husk is a cheap agro-based waste material, which harbors a substantial amount of silica in the form of amorphous hydrated silica grains. However, there have been no attempts at harnessing the enormous amount of amorphous silica present in rice husk and its room-temperature biotransformation into crystalline silica nanoparticles. In this study, we address this issue and describe how naturally deposited amorphous biosilica in rice husk can be bioleached and simultaneously biotransformed into high value crystalline silica nanoparticles. We show here that the fungus Fusarium oxysporum rapidly biotransforms the naturally occurring amorphous plant biosilica into crystalline silica and leach out silica extracellularly at room temperature in the form of 2-6 nm quasi-spherical, highly crystalline silica nanoparticles capped by stabilizing proteins; that the nanoparticles are released into solution is an advantage of this process with significant application and commercial potential. Calcination of the silica nanoparticles leads to loss of occluded protein and to an apparently porous structure often of cubic morphology. The room-temperature synthesis of oxide nanomaterials using microorganisms starting from potential cheap agro-industrial waste materials is an exciting possibility and could lead to an energy-conserving and economically viable green approach toward the large-scale synthesis of oxide nanomaterials.

  5. Influence of dissolved organic matter on the complexation of mercury under sulfidic conditions.

    Science.gov (United States)

    Miller, Carrie L; Mason, Robert P; Gilmour, Cynthia C; Heyes, Andrew

    2007-04-01

    The complexation of Hg under sulfidic conditions influences its bioavailability for microbial methylation. Neutral dissolved Hg-sulfide complexes are readily available to Hg-methylating bacteria in culture, and thermodynamic models predict that inorganic Hg-sulfide complexes dominate dissolved Hg speciation under natural sulfidic conditions. However, these models have not been validated in the field. To examine the complexation of Hg in natural sulfidic waters, octanol/water partitioning methods were modified for use under environmentally relevant conditions, and a centrifuge ultrafiltration technique was developed. These techniques demonstrated much lower concentrations of dissolved Hg-sulfide complexes than predicted. Furthermore, the study revealed an interaction between Hg, dissolved organic matter (DOM), and sulfide that is not captured by current thermodynamic models. Whereas Hg forms strong complexes with DOM under oxic conditions, these complexes had not been expected to form in the presence of sulfide because of the stronger affinity of Hg for sulfide relative to its affinity for DOM. The observed interaction between Hg and DOM in the presence of sulfide likely involves the formation of a DOM-Hg-sulfide complex or results from the hydrophobic partitioning of neutral Hg-sulfide complexes into the higher-molecular-weight DOM. An understanding of the mechanism of this interaction and determination of complexation coefficients for the Hg-sulfide-DOM complex are needed to adequately assess how our new finding affects Hg bioavailability, sorption, and flux.

  6. Marine methane paradox explained by bacterial degradation of dissolved organic matter

    Science.gov (United States)

    Repeta, Daniel J.; Ferrón, Sara; Sosa, Oscar A.; Johnson, Carl G.; Repeta, Lucas D.; Acker, Marianne; Delong, Edward F.; Karl, David M.

    2016-12-01

    Biogenic methane is widely thought to be a product of archaeal methanogenesis, an anaerobic process that is inhibited or outcompeted by the presence of oxygen and sulfate. Yet a large fraction of marine methane delivered to the atmosphere is produced in high-sulfate, fully oxygenated surface waters that have methane concentrations above atmospheric equilibrium values, an unexplained phenomenon referred to as the marine methane paradox. Here we use nuclear magnetic resonance spectroscopy to show that polysaccharide esters of three phosphonic acids are important constituents of dissolved organic matter in seawater from the North Pacific. In seawater and pure culture incubations, bacterial degradation of these dissolved organic matter phosphonates in the presence of oxygen releases methane, ethylene and propylene gas. Moreover, we found that in mutants of a methane-producing marine bacterium, Pseudomonas stutzeri, disrupted in the C-P lyase phosphonate degradation pathway, methanogenesis was also disabled, indicating that the C-P lyase pathway can catalyse methane production from marine dissolved organic matter. Finally, the carbon stable isotope ratio of methane emitted during our incubations agrees well with anomalous isotopic characteristics of seawater methane. We estimate that daily cycling of only about 0.25% of the organic matter phosphonate inventory would support the entire atmospheric methane flux at our study site. We conclude that aerobic bacterial degradation of phosphonate esters in dissolved organic matter may explain the marine methane paradox.

  7. Control of Crystal Morphology for Mold Flux During High-Aluminum AHSS Continuous Casting Process

    Science.gov (United States)

    GUO, Jing; SEO, Myung-Duk; SHI, Cheng-Bin; CHO, Jung-Wook; KIM, Seon-Hyo

    2016-08-01

    In the present manuscript, the efforts to control the crystal morphology are carried out aiming at improving the lubrication of lime-alumina-based mold flux for casting advanced high-strength steel with high aluminum. Jackson α factors for crystals of melt crystallization in multi-component mold fluxes are established and reasonably evaluated by applying thermodynamic databases to understand the crystal morphology control both in lime-alumina-based and lime-silica-based mold fluxes. The results show that Jackson α factor and supercooling are the most critical factors to determine the crystal morphology in a mold flux. Crystals precipitating in mold fluxes appear with different morphologies due to their different Jackson α factors and are likely to be more faceted with higher Jackson α factor. In addition, there is a critical supercooling degree for crystal morphology dendritic transition. When the supercooling over the critical value, the crystals transform from faceted shape to dendritic ones in morphology as the kinetic roughening occurs. Typically, the critical supercooling degrees for cuspidine dendritic transition in the lime-silica-based mold fluxes are evaluated to be between 0.05 and 0.06. Finally, addition of a small amount of Li2O in the mold flux can increase the Jackson α factor and decrease the supercooling for cuspidine precipitation; thus, it is favorable to enhance a faceted cuspidine crystal.

  8. Anisotropic silica mesostructures for DNA encapsulation

    Indian Academy of Sciences (India)

    Aparna Ganguly; Ashok K Ganguli

    2013-04-01

    The encapsulation of biomolecules in inert meso or nanostructures is an important step towards controlling drug delivery agents. Mesoporous silica nanoparticles (MSN) are of immense importance owing to their high surface area, large pore size, uniform particle size and chemical inertness. Reverse micellar method with CTAB as the surfactant has been used to synthesize anisotropic mesoporous silica materials. We have used the anisotropic silica nanostructures for DNA encapsulation studies and observed a loading capacity of ∼8 g mg-1 of the sample. On functionalizing the pores of silica with amine group, the amount of DNA loaded on the rods decreases which is due to a reduction in the pore size upon grafting of amine groups.

  9. Silica Brick for Hot Blast Stove

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ 1 Scope This standard specifies the glossary and definition, marking, shape and dimension, technical requirements, test method, quality appraisal procedure, packing, label, transportation, storage and quality certification of silica brick for hot blast stove.

  10. Accelerated purification of colloidal silica sols

    Science.gov (United States)

    Bahnsen, E. B.; Garofalini, S.; Pechman, A.

    1979-01-01

    Accelerated purification process for colloidal sols using heat/deionization scheme, sharply reduces waiting time between deionization cycles from several months to a few days. Process produces same high purity silica sols as conventional methods.

  11. Amorphous silica scale in cooling waters

    Energy Technology Data Exchange (ETDEWEB)

    Midkiff, W.S.; Foyt, H.P.

    1976-01-01

    In 1968, most of the evaporation cooled recirculating water systems at Los Alamos Scientific Laboratory were nearly inoperable due to scale. These systems, consisting of cooling towers, evaporative water coolers, evaporative condensers, and air washers had been operated on continuous blowdown without chemical treatment. The feedwater contained 80 mg/l silica. A successful program of routine chemical addition in the make-up water was begun. Blends of chelants, dispersants and corrosion inhibitors were found to gradually remove old scale, prevent new scale, and keep corrosion to less than an indicated rate of one mil per year. An explanation has been proposed that amorphous silica by itself does not form a troublesome scale. When combined with a crystal matrix such as calcite, the resultant silica containing scale can be quite troublesome. Rapid buildup of silica containing scale can be controlled and prevented by preventing formation of crystals from other constituents in the water such as hardness or iron. (auth)

  12. Insects, infestations and nutrient fluxes

    Science.gov (United States)

    Michalzik, B.

    2012-04-01

    endemic situations (Larrson and Tenow 1980). However, at times of insect mass outbreaks with leaf area losses up to 100%, nutrient fluxes are strongly affected at the ecosystem level and consequently attract greater attention (Grace 1986). In this context, mass outbreaks of herbivore insects constitute a class of ecosystem disturbance (Pickett and White 1985). More specific, insect pests meet the criteria of biogeochemical "hot spots" and "hot moments" (McClain et al. 2003) as they induce temporal-spatial process heterogeneity or changes in biogeochemical reaction rates, but not necessarily changes in the structure of ecosystems or landscapes. This contribution presents a compilation of literature and own research data on insect herbivory effects on nutrient cycling and ecosystem functioning from the plot to the catchment scale. It focuses on temperate forest ecosystems and on short-term impacts as exerted by two focal functional groups of herbivore canopy insects (leaf and sap feeders). In detail, research results on effects operating on short temporal scales are presented including a) alterations in throughfall fluxes encompassing dissolved and particulate organic matter fractions, b) alterations in the amount, timing and quality of frass and honeydew deposition and c) soil microbial activity and decomposition processes.

  13. MACROALGAE MEDIATION OF DISSOLVED ORGANIC NITROGEN FLUXES IN A TEMPERATE COASTAL LAGOON. (U915532)

    Science.gov (United States)

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  14. Technical Note: Mesocosm approach to quantify dissolved inorganic carbon percolation fluxes

    DEFF Research Database (Denmark)

    Thaysen, Eike Marie; Jessen, S.; Ambus, Per;

    2014-01-01

    unplanted soil. Carbon dioxide partial pressure (pCO(2)), alkalinity, soil moisture and temperature were measured with depth and time, and DIC in the percolate was quantified using a sodium hydroxide trap. Results showed good reproducibility between two replicate mesocosms. The pCO(2) varied between 0...

  15. Impacts of Agricultural Practices on Concentrations and Fluxes of Dissolved Organic Carbon

    Science.gov (United States)

    Oh, N.; Pellerin, B. A.; Bachand, P. A.; Bergamaschi, B. A.; Horwath, W. R.

    2008-12-01

    Organic matter from the breakdown of plant and animal material is a significant concern for drinking water quality in California due to the potential formation of carcinogenic disinfection byproducts (DBPs) during water treatment with chlorine. Reducing DOC concentration at the source water is a possible management strategy being explored for the reduction of DBP precursors. We examined a variety of land use/land cover, i.e. natural grasslands and intensive agriculture in the Willow Slough Watershed (415 km2) in Yolo County, California to determine the temporal and spatial DOC dynamics. Surface water DOC concentrations ranged from 1.62 to 11.44 mg L-1 at the mouth of the watershed during the first two years, with about two times higher DOC concentrations measured downstream in an intensive agricultural subwatershed dominated by summer flood irrigation. The mean DOC yield was also the highest from the agricultural subwatershed at 0.74 g m-2 over the six months of active irrigation. Results suggest that there is a positive correlation between cropland area and DOC yield. Among many crop species examined, alfalfa showed the strongest positive linear relationship with R2 = 0.91 between the irrigation season DOC yield and percentage crop area of each subwatershed, indicating that agricultural practices such as flood irrigation have a greater impact on DOC loads than other irrigation systems. The results indicate that agricultural practices may deserve further attention for watershed management of DOC and DBP precursors and that flood irrigation practices should be targeted to reduce DOC loading within the main watershed.

  16. Incorporation of H_2 in vitreous silica, qualitative and quantitative determination from Raman and infrared spectroscopy

    CERN Document Server

    Schmidt, B C; Schmidt, Burkhard C.; B\\'{e}ny, Jean-Michel

    1998-01-01

    Incorporation mechanisms of H_2 in silica glass were studied with Raman and infrared (IR) microspectroscopy. Hydrogenated samples were prepared at temperatures between 800 deg C and 955 deg C at 2 kbar total pressure. Hydrogen fugacities (f_{H_2}) were controlled using the double capsule technique with the iron-w\\"ustite (IW) buffer assemblage generating f_{H_2} of 1290-1370 bars corresponding to H_2 partial pressures (P_{H_2}) of 960-975 bars. We found that silica glass hydrogenated under such conditions contains molecular hydrogen (H_2) in addition to SiH and SiOH groups. H_2 molecules dissolved in the quenched glasses introduce a band at 4136 cm^{-1} in the Raman spectra which in comparison to that of gaseous H_2 is wider and is shifted to lower frequency. IR spectra of hydrogenated samples contain a band at 4138 cm^{-1} which we assign to the stretching vibration of H_2 molecules located in non-centrosymmetric sites. The Raman and IR spectra indicate that the dissolved H_2 molecules interact with the sili...

  17. The hydrogen-storing microporous silica 'Microcluster' reduces acetaldehyde contained in a distilled spirit.

    Science.gov (United States)

    Kato, Shinya; Miwa, Nobuhiko

    2016-12-01

    Acetaldehyde is a detrimental substance produced in alcoholic liquor aging. We assessed an ability of hydrogen-storing microporous silica 'Microcluster' (MC+) to reduce acetaldehyde, as compared with autoclave-dehydrogenated MC+ (MC-). Acetaldehyde was quantified spectrophotometrically by an enzymatic method. Authentic acetaldehyde was treated by MC+ for 20min, and decreased from 43.4ppm to 10.9ppm, but maintained at 49.3ppm by MC-. On the other hand, acetaldehyde contained in a distilled spirit was decreased from 29.5ppm to 3.1ppm at 20min by MC+, but not decreased by MC-. Addition of MC+ or MC- to distilled water without acetaldehyde showed no seeming effect on the quantification used. Accordingly acetaldehyde in a distilled spirit is reduced to ethanol by hydrogen contained in MC+, but not by the silica moiety of MC+. Hydrogen gas of 1.2mL was released for 20min from MC+ of 0.59g in water, resulting in dissolved hydrogen of 1.09ppm and an oxidation- reduction potential of -687.0mV indicative of a marked reducing ability. Thus, MC+ has an ability to reduce acetaldehyde in a distilled spirit due to dissolved hydrogen released from MC+. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Fixed Bed Adsorption of Drugs on Silica Aerogel from Supercritical Carbon Dioxide Solutions

    Directory of Open Access Journals (Sweden)

    Giuseppe Caputo

    2013-01-01

    Full Text Available Supercritical adsorption coupled with the high adsorption capacity of silica aerogel allows the preparation of a new kind of delivery systems of poor water soluble drugs. In order to overcome drawbacks of conventional techniques where the use of liquid solvents can cause the fracture of aerogel porous structure, in this work a new adsorption process of drugs from a supercritical mixture is proposed. Adsorption takes place from a fluid solution of the drug in supercritical CO2 and ethanol as cosolvent. A fixed bed adsorption plant has been developed to allow fast mixing of fluid phase and effective contact in the adsorption column. The use of ethanol as cosolvent allows to overcome the limitation of supercritical adsorption due to low solubility of many drugs in supercritical CO2. Adsorption isotherms were measured for one-model substance, nimesulide, at 40°C, and breakthrough curve was experimentally obtained. The drug loading of the drug into silica aerogel was up to 9 wt%. The drug composite was characterized using scanning electron microscopy, and release kinetics of the adsorbed drug were also evaluated by in vitro dissolution tests. The dissolution of nimesulide from loaded aerogel is much faster than dissolution of crystalline nimesulide. Around 80% of nimesulide dissolves from the aerogel within 6 minutes, whereas dissolving 80% of the crystalline drug takes about 90 min.

  19. Anomalous enthalpy relaxation in vitreous silica

    DEFF Research Database (Denmark)

    Yue, Yuanzheng

    2015-01-01

    scans. It is known that the liquid fragility (i.e., the speed of the viscous slow-down of a supercooled liquid at its Tg during cooling) has impact on enthalpy relaxation in glass. Here, we find that vitreous silica (as a strong system) exhibits striking anomalies in both glass transition and enthalpy...... the fragile ones do in a structurally independent fashion. We discuss the origin of the anomalous enthalpy relaxation in the HQ vitreous silica....

  20. UK silica sand resources for fracking

    OpenAIRE

    Mitchell, Clive

    2013-01-01

    UK silica sand resources for fracking Clive Mitchell, Industrial Minerals Specialist, British Geological Survey, Keyworth, Nottingham, NG12 5GG Email: Silica sand is high purity quartz sand that is mainly used for glass production, as foundry sand, in horticulture, leisure and other industrial uses. One specialist use is as a ‘proppant’ to enhance oil and gas recovery. This presentation will focus on this application, particularly for shale gas recovery where it is mo...

  1. Vibrating reed experiments on compacted vitreous silica

    Science.gov (United States)

    Weiss, G.; Daum, A.; Sohn, M.; Arndt, J.

    1996-02-01

    We have studied the acoustic properties of irreversibly compacted vitreous silica (Suprasil I) at frequencies around 12 kHz between 10 mK and room temperature. At low temperatures up to a few K the compacted glass exhibits acoustic properties similar to those of normal vitreous silica, however, with considerably smaller values of the damping and of the temperature coefficient of the sound velocity. Around 30 K the internal friction is reduced by factor of 6.

  2. X-ray absorption spectroscopy of strontium(II) coordination. II. Sorption and precipitation at kaolinite, amorphous silica, and goethite surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Sahai, N.; Carroll, S.A.; Roberts, S.; O' Day, P.A.

    2000-02-15

    Sorption of dissolved strontium on kaolinite, amorphous silica, and goethite was studied as a function of pH, aqueous strontium concentration, the presence or absence of atmospheric CO{sub 2} or dissolved phosphate, and aging over a 57-day period. Selected sorption samples ([Sr(a1)]{sub i} {approximately} 0.5--1 x 10{sup {minus}3}m) were examined with synchrotron X-ray absorption spectroscopy (XAS) at low (13--23 K) and room temperatures to determine the local molecular coordination around strontium.

  3. Behavior of dissolved aluminum in the Huanghe (Yellow River) and its estuary: Impact of human activities and sorption processes

    Science.gov (United States)

    Wang, Zhao-Wei; Ren, Jing-Ling; Zhang, Gui-Ling; Liu, Su-Mei; Zhang, Xiang-Zhao; Liu, Zhe; Zhang, Jing

    2015-02-01

    Dissolved aluminum (Al) is a sensitive tracer for biogeochemical cycles in the ocean. There has been a dramatic decline in water and sediment fluxes into the sea from the Huanghe because of climate change and human activities. Water-Sediment Regulation Schemes (WSRSs) have been implemented annually to flush trapped sediments from the upstream watercourse and reservoirs of the river. Monthly observations to investigate the behavior of dissolved Al in the lower reach of the Huanghe were carried out from November 2008 to December 2010. During 2009, daily observations were made to assess the impact of the ninth WSRS on the lower reach of the Huanghe and three cruises were carried out in the Huanghe Estuary in 2009 (prior to, during and following the WSRS). The monthly concentrations of dissolved Al ranged from 25 nM to 362 nM (average 90 nM) in the lower reach of the Huanghe. Assessment of the seasonal variation of dissolved Al showed that the highest concentrations occurred in summer and the lowest in winter: these corresponded to the variations in water discharge and sediment loads, which were controlled by WSRS events. During the ninth WSRS events in 2009 the daily runoff and sediment load increased from 200 m3/s to 3600 m3/s and from 0.1 g/L to 5 g/L, respectively. The concentration of dissolved Al increased from 180 nM to 600 nM (average 380 nM) in less than 20 days, which were equivalent to 43% of the annual Al flux into the Bohai. Exchange between dissolved and particulate Al, investigated using a simple sorption model based on the distribution coefficient (Kd), was approximately 106 mL/g in the Huanghe. The average concentrations of dissolved Al in the Huanghe Estuary prior to, during and following the WSRS were 243 nM, 238 nM and 186 nM, respectively. The comparable concentrations of dissolved Al in the Huanghe Estuary prior to and during the WSRS indicate that removal processes occurred in the initial stages of mixing in the estuary. The Al

  4. Thermal recycling of polystyrene and polystyrene-butadiene dissolved in a light cycle oil

    Energy Technology Data Exchange (ETDEWEB)

    Arandes, Jose M.; Erena, Javier; Olazar, Martin; Bilbao, Javier [Departamento de Ingenieria Quimica, Universidad del Pais Vasco, Apartado 644, 48080 Bilbao (Spain); Azkoiti, Miren J. [Departamento de Ingenieria Quimica y del Medio Ambiente, Universidad del Pais Vasco, Plaza de la Casilla 3, 48012 Bilbao (Spain)

    2003-12-01

    A study has been made of the cracking on a mesoporous silica of polystyrene (PS) and polystyrene-butadiene (PS-BD) dissolved in a light cycle oil (LCO) from a product stream of a commercial fluid catalytic cracking (FCC) unit. This study has been carried out in a reactor of short contact time (3 s) in the 723-823 K range. This strategy for simultaneous valorization of plastics and solvent avoids the technological problems inherent to the treatment of solid postconsumer-plastics and the limitation to heat transfer in the process of pyrolysis. The cracking of plastics has a synergistic effect on the conversion of LCO, as it contributes to increasing the yield of gasoline (C{sub 5}-C{sub 12}). The cracking of the PS/LCO blend produces high yields of styrene, whereas the cracking of the PS-BD/LCO blend produces a stream of products with petrochemical interest.

  5. Anomalous Enthalpy Relaxation in Vitreous Silica

    Directory of Open Access Journals (Sweden)

    Yuanzheng eYue

    2015-08-01

    Full Text Available It is a challenge to calorimetrically determine the glass transition temperature (Tg of vitreous silica. Here we demonstrate that this challenge mainly arises from the extreme sensitivity of the Tg to the hydroxyl content in vitreous silica, but also from the irreversibility of its glass transition when repeating the calorimetric scans. It is known that the liquid fragility (i.e., the speed of the viscous slow-down of a supercooled liquid at its Tg during cooling has impact on enthalpy relaxation in glass. Here we find that vitreous silica (as a strong system exhibits striking anomalies in both glass transition and enthalpy relaxation compared to fragile oxide systems. The anomalous enthalpy relaxation of vitreous silica is discovered by performing the hperquenching-annealing-calorimetry experiments. We argue that the strong systems like vitreous silica and vitreous Germania relax in a structurally cooperative manner, whereas the fragile ones do in a structurally independent fashion. We discuss the origin of the anomalous enthalpy relaxation in the HQ vitreous silica.

  6. Agmatine attenuates silica-induced pulmonary fibrosis.

    Science.gov (United States)

    El-Agamy, D S; Sharawy, M H; Ammar, E M

    2014-06-01

    There is a large body of evidence that nitric oxide (NO) formation is implicated in mediating silica-induced pulmonary fibrosis. As a reactive free radical, NO may not only contribute to lung parenchymal tissue injury but also has the ability to combine with superoxide and form a highly reactive toxic species peroxynitrite that can induce extensive cellular toxicity in the lung tissues. This study aimed to explore the effect of agmatine, a known NO synthase inhibitor, on silica-induced pulmonary fibrosis in rats. Male Sprague Dawley rats were treated with agmatine for 60 days following a single intranasal instillation of silica suspension (50 mg in 0.1 ml saline/rat). The results revealed that agmatine attenuated silica-induced lung inflammation as it decreased the lung wet/dry weight ratio, protein concentration, and the accumulation of the inflammatory cells in the bronchoalveolar lavage fluid. Agmatine showed antifibrotic activity as it decreased total hydroxyproline content of the lung and reduced silica-mediated lung inflammation and fibrosis in lung histopathological specimen. In addition, agmatine significantly increased superoxide dismutase (p pulmonary nitrite/nitrate as well as tumor necrosis factor α. Collectively, these results demonstrate the protective effects of agmatine against the silica-induced lung fibrosis that may be attributed to its ability to counteract the NO production, lipid peroxidation, and regulate cytokine effects.

  7. Influence of Silica Fume on Normal Concrete

    Directory of Open Access Journals (Sweden)

    Debabrata Pradhan

    2013-09-01

    Full Text Available The incorporation of silica fume into the normal concrete is a routine one in the present days to produce the tailor made high strength and high performance concrete. The design parameters are increasing with the incorporation of silica fume in conventional concrete and the mix proportioning is becoming complex. The main objective of this paper has been made to investigate the different mechanical properties like compressive strength, compacting factor, slump of concrete incorporating silica fume. In this present paper 5 (five mix of concrete incorporating silica fume are cast to perform experiments. These experiments were carried out by replacing cement with different percentages of silica fume at a single constant water-cementitious materials ratio keeping other mix design variables constant. The silica fume was replaced by 0%, 5%, 10%, 15% and 20% for water-cementitious materials (w/cm ratio for 0.40. For all mixes compressive strengths were determined at 24 hours, 7 and 28 days for 100 mm and 150 mm cubes. Other properties like compacting factor and slump were also determined for five mixes of concrete.

  8. Grassy Silica Nanoribbons and Strong Blue Luminescence

    Science.gov (United States)

    Wang, Shengping; Xie, Shuang; Huang, Guowei; Guo, Hongxuan; Cho, Yujin; Chen, Jun; Fujita, Daisuke; Xu, Mingsheng

    2016-09-01

    Silicon dioxide (SiO2) is one of the key materials in many modern technological applications such as in metal oxide semiconductor transistors, photovoltaic solar cells, pollution removal, and biomedicine. We report the accidental discovery of free-standing grassy silica nanoribbons directly grown on SiO2/Si platform which is commonly used for field-effect transistors fabrication without other precursor. We investigate the formation mechanism of this novel silica nanostructure that has not been previously documented. The silica nanoribbons are flexible and can be manipulated by electron-beam. The silica nanoribbons exhibit strong blue emission at about 467 nm, together with UV and red emissions as investigated by cathodoluminescence technique. The origins of the luminescence are attributed to various defects in the silica nanoribbons; and the intensity change of the blue emission and green emission at about 550 nm is discussed in the frame of the defect density. Our study may lead to rational design of the new silica-based materials for a wide range of applications.

  9. Mesoporous Silica from Rice Husk Ash

    Directory of Open Access Journals (Sweden)

    V.R. Shelke

    2011-01-01

    Full Text Available Mesoporous silica is used as a raw material in several areas: in preparation of catalysts, in inks, as a concrete hardening accelerator, as a component of detergents and soaps, as a refractory constituent etc. Sodium silicate is produced by reacting rice hull ash (RHA with aqueous NaOH and silica is precipitated from the sodium silicate by acidification. In the present work, conversion of about 90% of silica contained in RHA into sodium silicate was achieved in an open system at temperatures of about 100 °C. The results showed that silica obtained from RHA is mesoporous, has a large surface area and small particle size. Rice Husk is usually mixed with coal and this mixture is used for firing boilers. The RHA therefore, usually contains carbon particles. Activated carbon embedded on silica has been prepared using the carbon already present in RHA. This carbon shows good adsorption capacity. ©2010 BCREC UNDIP. All rights reserved(Received: 25th April 2010, Revised: 17th June 2010, Accepted: 24th June 2010[How to Cite: V.R. Shelke, S.S. Bhagade, S.A. Mandavgane. (2010. Mesoporous Silica from Rice Husk Ash. Bulletin of Chemical Reaction Engineering and Catalysis, 5 (2: 63-67. doi:10.9767/bcrec.5.2.793.63-67][DOI: http://dx.doi.org/10.9767/bcrec.5.2.793.63-67

  10. Silica Derived from Burned Rice Hulls

    Directory of Open Access Journals (Sweden)

    M.F. de Souza

    2002-10-01

    Full Text Available Three new processes to obtain silica having high specific surface area from burned pre-treated rice hulls are presented and discussed. These procedures allow for the simultaneous recovery of biomass energy and the production of high quality silica at thermoelectric plants, without the risk of using corrosive substances in the burning process. The first method involves treatment of the hull with hot organic acid solutions before burning, the second with boiling water, both using an autoclave at temperatures close to150 °C, while the third method renders the hull fragile by treating it at 250 °C and reducing it to a fine powder before burning. The first two methods result in white amorphous silica that can show 500 m²/g of specific surface area. The third method, which does not remove the alkaline elements from the hull, produces an amorphous gray carbon-free powder whose specific surface area can be as high as 250 m²/g. An investigation of the specific surface area of the prepared silica indicates the alkaline elements are not mixed with silica in the hulls or combined as insoluble compounds. A comparison is made of these processes and the dissolution of silica by sodium hydroxide solutions is discussed.

  11. Grassy Silica Nanoribbons and Strong Blue Luminescence

    Science.gov (United States)

    Wang, Shengping; Xie, Shuang; Huang, Guowei; Guo, Hongxuan; Cho, Yujin; Chen, Jun; Fujita, Daisuke; Xu, Mingsheng

    2016-01-01

    Silicon dioxide (SiO2) is one of the key materials in many modern technological applications such as in metal oxide semiconductor transistors, photovoltaic solar cells, pollution removal, and biomedicine. We report the accidental discovery of free-standing grassy silica nanoribbons directly grown on SiO2/Si platform which is commonly used for field-effect transistors fabrication without other precursor. We investigate the formation mechanism of this novel silica nanostructure that has not been previously documented. The silica nanoribbons are flexible and can be manipulated by electron-beam. The silica nanoribbons exhibit strong blue emission at about 467 nm, together with UV and red emissions as investigated by cathodoluminescence technique. The origins of the luminescence are attributed to various defects in the silica nanoribbons; and the intensity change of the blue emission and green emission at about 550 nm is discussed in the frame of the defect density. Our study may lead to rational design of the new silica-based materials for a wide range of applications. PMID:27666663

  12. Hollow silica spheres: synthesis and mechanical properties.

    Science.gov (United States)

    Zhang, Lijuan; D'Acunzi, Maria; Kappl, Michael; Auernhammer, Günter K; Vollmer, Doris; van Kats, Carlos M; van Blaaderen, Alfons

    2009-03-03

    Core-shell polystyrene-silica spheres with diameters of 800 nm and 1.9 microm were synthesized by soap-free emulsion and dispersion polymerization of the polystyrene core, respectively. The polystyrene spheres were used as templates for the synthesis of silica shells of tunable thickness employing the Stöber method [Graf et al. Langmuir 2003, 19, 6693]. The polystyrene template was removed by thermal decomposition at 500 degrees C, resulting in smooth silica shells of well-defined thickness (15-70 nm). The elastic response of these hollow spheres was probed by atomic force microscopy (AFM). A point load was applied to the particle surface through a sharp AFM tip, and successively increased until the shell broke. In agreement with the predictions of shell theory, for small deformations the deformation increased linearly with applied force. The Young's modulus (18 +/- 6 GPa) was about 4 times smaller than that of fused silica [Adachi and Sakka J. Mater. Sci. 1990, 25, 4732] but identical to that of bulk silica spheres (800 nm) synthesized by the Stöber method, indicating that it yields silica of lower density. The minimum force needed to irreversibly deform (buckle) the shell increased quadratically with shell thickness.

  13. Core-Shell-Corona Silica Hybrid Nanoparticles Templated by Spherical Polyelectrolyte Brushes: A Study by Small Angle X-ray Scattering.

    Science.gov (United States)

    Han, Haoya; Li, Li; Wang, Weihua; Tian, Yuchuan; Wang, Yunwei; Wang, Junyou; von Klitzing, Regine; Guo, Xuhong

    2017-09-06

    Core-shell-corona silica/polymer hybrid nanoparticles with narrow size distribution were prepared in the template of spherical polyelectrolyte brushes (SPB) which consist of a solid polystyrene (PS) core densely grafted with linear poly(acrylic acid) (PAA) chains. The microstructure of obtained hybrid nanoparticles was studied by small-angle X-ray scattering (SAXS) and in combination with dynamic light scattering (DLS) and transmission electron microscopy (TEM). The generation of silica shell within the brush is confirmed by the significant increase of the electron density in the shell, and the silica shell showed a unique inner-loose-outer-dense structure, whose thickness is pH sensitive but is insensitive to ionic strength as revealed by fitting SAXS data. After dissolving the PS core, hollow silica nanoparticles were obtained and determined by SAXS, which should be ideal carriers for pH-triggered drug delivery. SAXS is confirmed to be a powerful method to characterize the core-shell-corona silica/polymer hybrid and hollow silica nanoparticles.

  14. Controlling the locus of bubble nucleation by dissolved gases in heterogeneous liquid-liquid systems.

    Science.gov (United States)

    Priyananda, Pramith; Hawkett, Brian S; Warr, Gregory G

    2010-01-19

    We have examined the nucleation of chemically generated nitrogen gas bubbles in microheterogeneous systems, using optical microscopy on a model system consisting of a single liquid-liquid interface. Results clearly show that bubble nucleation occurs in both the aqueous and oil phases, despite the nitrogen production reaction being a purely aqueous phase process. A theoretical model is developed which describes the time evolution of the nitrogen concentration profile, and this reveals that bubbles in the oil are a result of homogeneous nucleation of dissolved N(2) transported across the interface into a (supersaturated) diffusion layer. We further show that bubble nucleation in the oil can be inhibited or eliminated by adding water-soluble surfactants, which facilitates aqueous phase bubble nucleation and then acts as highly effective nitrogen sinks, severely reducing the flux of dissolved gas across the water-oil interface.

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

    Science.gov (United States)

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

    2016-12-01

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

  16. The Flux-Flux Correlation Function for Anharmonic Barriers

    CERN Document Server

    Goussev, Arseni; Waalkens, Holger; Wiggins, Stephen

    2010-01-01

    The flux-flux correlation function formalism is a standard and widely used approach for the computation of reaction rates. In this paper we introduce a method to compute the classical and quantum flux-flux correlation functions for anharmonic barriers essentially analytically through the use of the classical and quantum normal forms. In the quantum case we show that the quantum normal form reduces the computation of the flux-flux correlation function to that of an effective one dimensional anharmonic barrier. The example of the computation of the quantum flux-flux correlation function for a fourth order anharmonic barrier is worked out in detail, and we present an analytical expression for the quantum mechanical microcanonical flux-flux correlation function. We then give a discussion of the short-time and harmonic limits.

  17. Flux pinning in superconductors

    CERN Document Server

    Matsushita, Teruo

    2014-01-01

    The book covers the flux pinning mechanisms and properties and the electromagnetic phenomena caused by the flux pinning common for metallic, high-Tc and MgB2 superconductors. The condensation energy interaction known for normal precipitates or grain boundaries and the kinetic energy interaction proposed for artificial Nb pins in Nb-Ti, etc., are introduced for the pinning mechanism. Summation theories to derive the critical current density are discussed in detail. Irreversible magnetization and AC loss caused by the flux pinning are also discussed. The loss originally stems from the ohmic dissipation of normal electrons in the normal core driven by the electric field induced by the flux motion. The readers will learn why the resultant loss is of hysteresis type in spite of such mechanism. The influence of the flux pinning on the vortex phase diagram in high Tc superconductors is discussed, and the dependencies of the irreversibility field are also described on other quantities such as anisotropy of supercondu...

  18. Flux Pinning in Superconductors

    CERN Document Server

    Matsushita, Teruo

    2007-01-01

    The book covers the flux pinning mechanisms and properties and the electromagnetic phenomena caused by the flux pinning common for metallic, high-Tc and MgB2 superconductors. The condensation energy interaction known for normal precipitates or grain boundaries and the kinetic energy interaction proposed for artificial Nb pins in Nb-Ti, etc., are introduced for the pinning mechanism. Summation theories to derive the critical current density are discussed in detail. Irreversible magnetization and AC loss caused by the flux pinning are also discussed. The loss originally stems from the ohmic dissipation of normal electrons in the normal core driven by the electric field induced by the flux motion. The readers will learn why the resultant loss is of hysteresis type in spite of such mechanism. The influence of the flux pinning on the vortex phase diagram in high Tc superconductors is discussed, and the dependencies of the irreversibility field are also described on other quantities such as anisotropy of supercondu...

  19. Effect of Greenhouse Gases Dissolved in Seawater.

    Science.gov (United States)

    Matsunaga, Shigeki

    2015-12-30

    A molecular dynamics simulation has been performed on the greenhouse gases carbon dioxide and methane dissolved in a sodium chloride aqueous solution, as a simple model of seawater. A carbon dioxide molecule is also treated as a hydrogen carbonate ion. The structure, coordination number, diffusion coefficient, shear viscosity, specific heat, and thermal conductivity of the solutions have been discussed. The anomalous behaviors of these properties, especially the negative pressure dependence of thermal conductivity, have been observed in the higher-pressure region.

  20. Preservation of samples for dissolved mercury

    Science.gov (United States)

    Hamlin, S.N.

    1989-01-01

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

  1. Effect of Greenhouse Gases Dissolved in Seawater

    OpenAIRE

    Shigeki Matsunaga

    2015-01-01

    A molecular dynamics simulation has been performed on the greenhouse gases carbon dioxide and methane dissolved in a sodium chloride aqueous solution, as a simple model of seawater. A carbon dioxide molecule is also treated as a hydrogen carbonate ion. The structure, coordination number, diffusion coefficient, shear viscosity, specific heat, and thermal conductivity of the solutions have been discussed. The anomalous behaviors of these properties, especially the negative pressure dependence o...

  2. Silica ecosystem for synergistic biotransformation

    Science.gov (United States)

    Mutlu, Baris R.; Sakkos, Jonathan K.; Yeom, Sujin; Wackett, Lawrence P.; Aksan, Alptekin

    2016-06-01

    Synergistical bacterial species can perform more varied and complex transformations of chemical substances than either species alone, but this is rarely used commercially because of technical difficulties in maintaining mixed cultures. Typical problems with mixed cultures on scale are unrestrained growth of one bacterium, which leads to suboptimal population ratios, and lack of control over bacterial spatial distribution, which leads to inefficient substrate transport. To address these issues, we designed and produced a synthetic ecosystem by co-encapsulation in a silica gel matrix, which enabled precise control of the microbial populations and their microenvironment. As a case study, two greatly different microorganisms: Pseudomonas sp. NCIB 9816 and Synechococcus elongatus PCC 7942 were encapsulated. NCIB 9816 can aerobically biotransform over 100 aromatic hydrocarbons, a feat useful for synthesis of higher value commodity chemicals or environmental remediation. In our system, NCIB 9816 was used for biotransformation of naphthalene (a model substrate) into CO2 and the cyanobacterium PCC 7942 was used to provide the necessary oxygen for the biotransformation reactions via photosynthesis. A mathematical model was constructed to determine the critical cell density parameter to maximize oxygen production, and was then used to maximize the biotransformation rate of the system.

  3. Dissolvable microneedle fabrication using piezoelectric dispensing technology.

    Science.gov (United States)

    Allen, Evin A; O'Mahony, Conor; Cronin, Michael; O'Mahony, Thomas; Moore, Anne C; Crean, Abina M

    2016-03-16

    Dissolvable microneedle (DMN) patches are novel dosage forms for the percutaneous delivery of vaccines. DMN are routinely fabricated by dispensing liquid formulations into microneedle-shaped moulds. The liquid formulation within the mould is then dried to create dissolvable vaccine-loaded microneedles. The precision of the dispensing process is critical to the control of formulation volume loaded into each dissolvable microneedle structure. The dispensing process employed must maintain vaccine integrity. Wetting of mould surfaces by the dispensed formulation is also an important consideration for the fabrication of sharp-tipped DMN. Sharp-tipped DMN are essential for ease of percutaneous administration. In this paper, we demonstrate the ability of a piezoelectric dispensing system to dispense picolitre formulation volumes into PDMS moulds enabling the fabrication of bilayer DMN. The influence of formulation components (trehalose and polyvinyl alcohol (PVA) content) and piezoelectric actuation parameters (voltage, frequency and back pressure) on drop formation is described. The biological integrity of a seasonal influenza vaccine following dispensing was investigated and maintained voltage settings of 30 V but undermined at higher settings, 50 and 80 V. The results demonstrate the capability of piezoelectric dispensing technology to precisely fabricate bilayer DMN. They also highlight the importance of identifying formulation and actuation parameters to ensure controlled droplet formulation and vaccine stabilisation.

  4. Dissolved organic nitrogen measurement using dialysis pretreatment.

    Science.gov (United States)

    Lee, Wontae; Westerhoff, Paul

    2005-02-01

    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.

  5. Protected Flux Pairing Qubit

    Science.gov (United States)

    Bell, Matthew; Zhang, Wenyuan; Ioffe, Lev; Gershenson, Michael

    2014-03-01

    We have studied the coherent flux tunneling in a qubit containing two submicron Josephson junctions shunted by a superinductor (a dissipationless inductor with an impedance much greater than the resistance quantum). The two low energy quantum states of this device, " open="|"> 0 and " open="|"> 1, are represented by even and odd number of fluxes in the loop, respectively. This device is dual to the charge pairing Josephson rhombi qubit. The spectrum of the device, studied by microwave spectroscopy, reflects the interference between coherent quantum phase slips in the two junctions (the Aharonov-Casher effect). The time domain measurements demonstrate the suppression of the qubit's energy relaxation in the protected regime, which illustrates the potential of this flux pairing device as a protected quantum circuit. Templeton Foundation, NSF, and ARO.

  6. Effect of silica fouling on the removal of pharmaceuticals and personal care products by nanofiltration and reverse osmosis membranes.

    Science.gov (United States)

    Lin, Yi-Li; Chiou, Jheng-Hong; Lee, Chung-Hsiang

    2014-07-30

    In this study, one reverse osmosis (XLE) and two nanofiltration (NF90 and NF270) membranes were fouled by silica to evaluate its effect on the flux decline as well as the removal of six pharmaceuticals and personal care products (PPCPs) including carbamazapine (CBZ), triclosan (TRI), ibuprofen (IBU), sulfadiazine (DIA), sulfamethoxazole (SMX) and sulfamethazine (SMZ) from pH 3 to 10. The membranes were characterized by physicochemical properties including hydrophobicity, surface morphology and PPCPs adsorption with or without the presence of silica fouling to validate the rejection mechanisms of PPCPs. The fouling mechanisms were investigated using the modified Hermia model. It was found that all membranes with silica fouling showed more severe permeate flux decline at low pHs (3 and 5) than at high pHs (8 and 10) by the decomposition of nonionized silica particles to form a dense gel layer on membrane surfaces, which was hard to be removed by backwash. Silica fouling rendered the membrane surface considerably more hydrophilic, and only IBU, TRI and SMZ were adsorbed on membranes. Silica fouling on tight membranes (NF90 and XLE) can promote rejection of most PPCPs because the dense fouling layer could supply membrane with synergistic steric hindrance to reduce the transportation of PPCPs across membrane surface, implying that size exclusion is the dominating mechanism. While for loose NF270, electrostatic repulsion dominates by enhanced rejection of PPCPs as pH increased. Although fouling layer could provide extra steric hindrance for NF270, its effect was overwhelmed by the accompanied cake-enhanced concentration polarization phenomenon (CEOP). CEOP impeded back diffusion of PPCPs into the feed solution, trapped and accumulated PPCPs on membrane surface so as to increase their diffusion across membrane. At all pH levels, intermediate blocking and gel layer formation was the major fouling mechanism for tight and loose membrane, respectively.

  7. Solar Magnetic Flux Ropes

    Indian Academy of Sciences (India)

    Boris Filippov; Olesya Martsenyuk; Abhishek K. Srivastava; Wahab Uddin

    2015-03-01

    In the early 1990s, it was found that the strongest disturbances of the space–weather were associated with huge ejections of plasma from the solar corona, which took the form of magnetic clouds when moved from the Sun. It is the collisions of the magnetic clouds with the Earth's magnetosphere that lead to strong, sometimes catastrophic changes in space–weather. The onset of a coronal mass ejection (CME) is sudden and no reliable forerunners of CMEs have been found till date. The CME prediction methodologies are less developed compared to the methods developed for the prediction of solar flares. The most probable initial magnetic configuration of a CME is a flux rope consisting of twisted field lines which fill the whole volume of a dark coronal cavity. The flux ropes can be in stable equilibrium in the coronal magnetic field for weeks and even months, but suddenly they lose their stability and erupt with high speed. Their transition to the unstable phase depends on the parameters of the flux rope (i.e., total electric current, twist, mass loading, etc.), as well as on the properties of the ambient coronal magnetic field. One of the major governing factors is the vertical gradient of the coronal magnetic field, which is estimated as decay index (). Cold dense prominence material can be collected in the lower parts of the helical flux tubes. Filaments are, therefore, good tracers of the flux ropes in the corona, which become visible long before the beginning of the eruption. The perspectives of the filament eruptions and following CMEs can be estimated by a comparison of observed filament heights with calculated decay index distributions. The present paper reviews the formation of magnetic flux ropes, their stable and unstable phases, eruption conditions, and also discusses their physical implications in the solar corona.

  8. The Management of Silica in Los Alamos National Laboratory Tap Water - A Study of Silica Solubility

    Energy Technology Data Exchange (ETDEWEB)

    Wohlberg, C.; Worland, V.P.; Kozubal, M.A.; Erickson, G.F.; Jacobson, H.M.; McCarthy, K.T.

    1999-07-01

    Well water at Los Alamos National Laboratory (LANL) has a silica (SiO{sub 2}) content of 60 to 100 mg/L, with 4 mg/L of magnesium, 13 mg/L calcium and lesser concentrations of other ions. On evaporation in cooling towers, when the silica concentration reaches 150 to 220 mg/L, silica deposits on heat transfer surfaces. When the high silica well water is used in the reprocessing of plutonium, silica remains in solution at the end of the process and creates a problem of removal from the effluent prior to discharge or evaporation. The work described in this Report is divided into two major parts. The first part describes the behavior of silica when the water is evaporated at various conditions of pH and in the presence of different classes of anions: inorganic and organic. In the second part of this work it was found that precipitation (floccing) of silica was a function of solution pH and mole ratio of metal to silica.

  9. Effect of Mineral Admixtures on Alkali-Silica Reaction

    Institute of Scientific and Technical Information of China (English)

    ZHANG Chengzhi; WANG Aiqin

    2008-01-01

    The influence of silica fume,slag and fly ash on alkali-silica reaction under the condition of 70℃ is studied.The results show that silica,slag and fly ash may inhibit alkali-silica reaction only under suitable content.When the content is less than 10%,silica fume does not markedly influence the expansion of alkali-silica reaction.When the content is 15%-20%,silica fume only may delay the expansion of alkali-silica reaction.When the content is 30%-70%,slag may only delay the expansion of alkali-silica reaction,but cannot inhibit the expansion of alkali-silica reaction.When the content is 10%,fly ash does not markedly influence the expansion of alkali-silica reaction.When the content is 20%-30%,fly ash may only delay the expansion of alkali-silica reaction,but cannot inhibit the expansion of alkali-silica reaction.When the content is over 50%,it is possible that fly ash can inhibit effectively alkali-silica reaction.

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

    Science.gov (United States)

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

    2017-09-13

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

  11. Dynamics of dissolved organic carbon in hillslope discharge: Modeling and challenges

    Science.gov (United States)

    Dusek, Jaromir; Vogel, Tomas; Dohnal, Michal; Barth, Johannes A. C.; Sanda, Martin; Marx, Anne; Jankovec, Jakub

    2017-03-01

    Reliable quantitative prediction of water movement and fluxes of dissolved substances - specifically organic carbon - at both the hillslope and the catchment scales remains a challenge due to complex boundary conditions and soil spatial heterogeneity. In addition, microbially mediated transformations of dissolved organic carbon (DOC) are recognized to determine the balance of DOC in soils. So far, only few studies utilized stable water isotope information in modeling and even fewer linked dissolved carbon fluxes to mixing and/or transport models. In this study, stormflow dynamics of 18O/16O ratios in the water molecules (expressed as δ18O) and DOC were analyzed using a physically-based modeling approach. A one-dimensional dual-continuum vertical flow and transport model was used to simulate the subsurface transport processes in a forest hillslope soil over a period of 2.5 years. The model was applied to describe the transformation of input signals of δ18O and DOC into output signals observed in the hillslope stormflow. To quantify uncertainty associated with the model parameterization, Monte Carlo analysis in conjunction with Latin hypercube sampling was applied. δ18O variations in hillslope discharge and in soil pore water were predicted reasonably well. Despite the complex nature of microbial transformations that caused uncertainty in model parameters and subsequent prediction of DOC transport, the simulated temporal patterns of DOC concentration in stormflow showed similar behavior to that reflected in the observed DOC fluxes. Due to preferential flow, the contribution of the hillslope DOC export was higher than the amounts that are usually found in the available literature.

  12. Silica Fume and Fly Ash Admixed Can Help to Improve the PRC Durability Combine Microscopic Analysis

    Directory of Open Access Journals (Sweden)

    Xiao Li-guang

    2016-01-01

    Full Text Available Silica fume/Fly ash RPC can greatly improve durability. When Silica fume to replace the same amount of 8% of the proportion of cement, re-mixed 15min of mechanically activated Fly ash content of 10%, by chloride ion flux detector measuring, complex doped than the reference RPC impermeability improved significantly; In addition, by using static nitrogen adsorption method showed, RPC internal pore structure determination, the hole integral volume was lower than the reference admixed RPC integral pore volume significantly; And combined SEM microscopic experimental methods, mixed of RPC internal structure and the formation mechanism analysis showed that, SF/FA complex fully embodies the synergy doped composites “Synergistic” principle.

  13. Nano silica removal from IC wastewater by pre-coagulation and microfiltration.

    Science.gov (United States)

    Huang, C; Jiang, W; Chen, C

    2004-01-01

    Microfiltration (MF) coupled with pretreatment by coagulation was adopted in the treatment of chemical mechanical polishing (CMP) wastewater from IC manufacturing plants, containing high concentrations of silica. Poly-aluminium chloride (PACl) was the coagulant, while the cationic polyacrylamide (PAA) was the flocculant aid. Preliminary tests were performed with the raw CMP wastewater in order to determine the optimal coagulation condition for subsequent microfiltration. Analysis of the particle size distribution shows that nearly all silica particles were enlarged from nano scale to at least 4 microm in diameter after the pre-treatment. The pre-treated wastewater was then filtered through a polytetrafluoroethylene (PTFE) membrane with a pore size 0.5 microm at a constant vacuum pressure. Trace amounts of PAA in addition to the PACl coagulation can effectively increases the permeate flux.

  14. Construction of silica-enhanced S-layer protein cages.

    Science.gov (United States)

    Schuster, D; Küpcü, S; Belton, D J; Perry, C C; Stöger-Pollach, M; Sleytr, U B; Pum, D

    2013-03-01

    The work presented here shows for the first time that it is possible to silicify S-layer coated liposomes and to obtain stable functionalized hollow nano-containers. For this purpose, the S-layer protein of Geobacillus stearothermophilus PV72/p2 was recombinantly expressed and used for coating positively charged liposomes composed of dipalmitoylphosphatidylcholine, cholesterol and hexadecylamine in a molar ratio of 10:5:4. Subsequently, plain (uncoated) liposomes and S-layer coated liposomes were silicified. Determination of the charge of the constructs during silicification allowed the deposition process to be followed. After the particles had been silicified, lipids were dissolved by treatment with Triton X-100 with the release of previously entrapped fluorescent dyes being determined by fluorimetry. Both, ζ-potential and release experiments showed differences between silicified plain liposomes and silicified S-layer coated liposomes. The results of the individual preparation steps were examined by embedding the respective assemblies in resin, ultrathin sectioning and inspection by bright-field transmission electron microscopy (TEM). Energy filtered TEM confirmed the successful construction of S-layer based silica cages. It is anticipated that this approach will provide a key to enabling technology for the fabrication of nanoporous protein cages for applications ranging from nano medicine to materials science.

  15. Iron(III)-doped, silica nanoshells: a biodegradable form of silica.

    Science.gov (United States)

    Pohaku Mitchell, Kristina K; Liberman, Alexander; Kummel, Andrew C; Trogler, William C

    2012-08-29

    Silica nanoparticles are being investigated for a number of medical applications; however, their use in vivo has been questioned because of the potential for bioaccumulation. To obviate this problem, silica nanoshells were tested for enhanced biodegradability by doping iron(III) into the nanoshells. Exposure of the doped silica to small molecule chelators and mammalian serum was explored to test whether the removal of iron(III) from the silica nanoshell structure would facilitate its degradation. Iron chelators, such as EDTA, desferrioxamine, and deferiprone, were found to cause the nanoshells to degrade on the removal of iron(III) within several days at 80 °C. When the iron(III)-doped, silica nanoshells were submerged in fetal bovine and human serums at physiological temperature, they also degrade via removal of the iron by serum proteins, such as transferrin, over a period of several weeks.

  16. Comparative Investigation on Thermal Insulation of Polyurethane Composites Filled with Silica Aerogel and Hollow Silica Microsphere.

    Science.gov (United States)

    Liu, Chunyuan; Kim, Jin Seuk; Kwon, Younghwan

    2016-02-01

    This paper presents a comparative study on thermal conductivity of PU composites containing open-cell nano-porous silica aerogel and closed-cell hollow silica microsphere, respectively. The thermal conductivity of PU composites is measured at 30 degrees C with transient hot bridge method. The insertion of polymer in pores of silica aerogel creates mixed interfaces, increasing the thermal conductivity of resulting composites. The measured thermal conductivity of PU composites filled with hollow silica microspheres is estimated using theoretical models, and is in good agreement with Felske model. It appears that the thermal conductivity of composites decreases with increasing the volume fraction (phi) when hollow silica microsphere (eta = 0.916) is used.

  17. Synthesis and Characterization of Bionanoparticle-Silica Composites and Mesoporous Silica with Large Pores

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Z.; Yang, L.; Kabisatpathy, S.; He, J.; Lee, A.; Ron, J.; Sikha, G.; Popov, B.N.; Emrick, T.; Russell, T. P.; Wang. Q.

    2009-03-24

    A sol-gel process has been developed to incorporate bionanoparticles, such as turnip yellow mosaic virus, cowpea mosaic virus, tobacco mosaic virus, and ferritin into silica, while maintaining the integrity and morphology of the particles. The structures of the resulting materials were characterized by transmission electron microscopy, small angle X-ray scattering, and N{sub 2} adsorption-desorption analysis. The results show that the shape and surface morphology of the bionanoparticles are largely preserved after being embedded into silica. After removal of the bionanoparticles by calcination, mesoporous silica with monodisperse pores, having the shape and surface morphology of the bionanoparticles replicated inside the silica, was produced,. This study is expected to lead to both functional composite materials and mesoporous silica with structurally well-defined large pores.

  18. Hard magnetism in structurally engineered silica nanocomposite.

    Science.gov (United States)

    Song, Hyon-Min; Zink, Jeffrey I

    2016-09-21

    Creation of structural complexity by simple experimental control will be an attractive approach for the preparation of nanomaterials, as a classical bottom-up method is supplemented by a more efficient and more direct artificial engineering method. In this study, structural manipulation of MCM-41 type mesoporous silica is investigated by generating and imbedding hard magnetic CoFe2O4 nanoparticles into mesoporous silica. Depending on the heating rate and target temperature, mesoporous silica undergoes a transformation in shape to form hollow silica, framed silica with interior voids, or melted silica with intact mesostructures. Magnetism is governed by the major CoFe2O4 phase, and it is affected by antiferromagnetic hematite (α-Fe2O3) and olivine-type cobalt silicate (Co2SiO4), as seen in its paramagnetic behavior at the annealing temperature of 430 °C. The early formation of Co2SiO4 than what is usually observed implies the effect of the partial substitution of Fe in the sites of Co. Under slow heating (2.5 °C min(-1)) mesostructures are preserved, but with significantly smaller mesopores (d100 = 1.5 nm). In addition, nonstoichiometric CoxFe1-xO with metal vacancies at 600 °C, and spinel Co3O4 at 700 °C accompany major CoFe2O4. The amorphous nature of silica matrix is thought to contribute significantly to these structurally diverse and rich phases, enabled by off-stoichiometry between Si and O, and accelerated by the diffusion of metal cations into SiO4 polyhedra at an elevated temperature.

  19. CO sub(2) and N sub(2) O fluxes from the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Narvekar, P.V.; Naqvi, S.W.A.; DileepKumar, M.

    The CO sub(2) and N sub(2)O in the north Indian Ocean were measured and their fluxes were evaluated. Samples were collected from the Arabian Sea and the Bay of Bengal. The water samples were analysed for dissolved oxygen, pH, TCO sub(2) and N sub(2...

  20. Assessing Organic Contaminant Fluxes from Contaminated Sediments Following Dam Removal in an Urbanized River

    Science.gov (United States)

    In this study, methods and approaches were developed and tested to assess changes in contaminant fluxes resulting from dam removal in a riverine system. Sediment traps and passive samplers were deployed to measure particulate and dissolved PAHs and PCBs in the water column prior...

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

    Science.gov (United States)

    Okada, Hiroshi; Tanaka, Kazuo; Chujo, Yoshiki

    2014-06-15

    Platinum(II) octaethylporphyrin (PtOEP)-loaded organic-inorganic hybrids were obtained via the microwave-assisted sol-gel condensation with methyltrimethoxysilane and poly(vinylpyrrolidone). From transparent and homogeneous hybrid films, the strong phosphorescence from PtOEP was observed. Next, the resulting hybrids were immersed in the aqueous buffer, and the emission intensity was monitored by changing the dissolved oxygen level in the buffer. When the hybrid with relatively-higher amount of the silica element, the strong phosphorescence was observed even under the aerobic conditions. In contrast, the emission from the hybrids with lower amounts of the silica element was quenched under the hypoxic conditions. This is, to the best of our knowledge, the first example to demonstrate that the responsiveness of the phosphorescence intensity of PtOEP in hybrid films to the dissolved oxygen concentration in water can be modulated by changing the percentage of the contents in the material. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Barium and carbon fluxes in the Canadian Arctic Archipelago

    Science.gov (United States)

    Thomas, Helmuth; Shadwick, Elizabeth; Dehairs, Frank; Lansard, Bruno; Mucci, Alfonso; Navez, Jacques; Gratton, Yves; Prowe, Friederike; Chierici, Melissa; Fransson, Agneta; Papakyriakou, Tim N.; Sternberg, Erika; Miller, Lisa A.; Tremblay, Jean-ÉRic; Monnin, Christophe

    2011-09-01

    The seasonal and spatial variability of dissolved Barium (Ba) in the Amundsen Gulf, southeastern Beaufort Sea, was monitored over a full year from September 2007 to September 2008. Dissolved Ba displays a nutrient-type behavior: the maximum water column concentration is located below the surface layer. The highest Ba concentrations are typically observed at river mouths, the lowest concentrations are found in water masses of Atlantic origin. Barium concentrations decrease eastward through the Canadian Arctic Archipelago. Barite (BaSO4) saturation is reached at the maximum dissolved Ba concentrations in the subsurface layer, whereas the rest of the water column is undersaturated. A three end-member mixing model comprising freshwater from sea-ice melt and rivers, as well as upper halocline water, is used to establish their relative contributions to the Ba concentrations in the upper water column of the Amundsen Gulf. Based on water column and riverine Ba contributions, we assess the depletion of dissolved Ba by formation and sinking of biologically bound Ba (bio-Ba), from which we derive an estimate of the carbon export production. In the upper 50 m of the water column of the Amundsen Gulf, riverine Ba accounts for up to 15% of the available dissolved Ba inventory, of which up to 20% is depleted by bio-Ba formation and export. Since riverine inputs and Ba export occur concurrently, the seasonal variability of dissolved Ba in the upper water column is moderate. Assuming a fixed organic carbon to bio-Ba flux ratio, carbon export out of the surface layer is estimated at 1.8 ± 0.45 mol C m-2 yr-1. Finally, we propose a climatological carbon budget for the Amundsen Gulf based on recent literature data and our findings, the latter bridging the surface and subsurface water carbon cycles.

  3. Muon and neutrino fluxes

    Science.gov (United States)

    Edwards, P. G.; Protheroe, R. J.

    1985-01-01

    The result of a new calculation of the atmospheric muon and neutrino fluxes and the energy spectrum of muon-neutrinos produced in individual extensive air showers (EAS) initiated by proton and gamma-ray primaries is reported. Also explained is the possibility of detecting atmospheric nu sub mu's due to gamma-rays from these sources.

  4. Coupled superconducting flux qubits

    NARCIS (Netherlands)

    Plantenberg, J.H.

    2007-01-01

    This thesis presents results of theoretical and experimental work on superconducting persistent-current quantum bits. These qubits offer an attractive route towards scalable solid-state quantum computing. The focus of this work is on the gradiometer flux qubit which has a special geometric design, t

  5. Generic flux coupling analysis

    NARCIS (Netherlands)

    Reimers, A.C.; Goldstein, Y.; Bockmayr, A.

    2015-01-01

    Flux coupling analysis (FCA) has become a useful tool for aiding metabolic reconstructions and guiding genetic manipulations. Originally, it was introduced for constraint-based models of metabolic networks that are based on the steady-state assumption. Recently, we have shown that the steady-state a

  6. Lobotomy of flux compactifications

    NARCIS (Netherlands)

    Dibitetto, Giuseppe; Guarino, Adolfo; Roest, Diederik

    2014-01-01

    We provide the dictionary between four-dimensional gauged supergravity and type II compactifications on (6) with metric and gauge fluxes in the absence of supersymmetry breaking sources, such as branes and orientifold planes. Secondly, we prove that there is a unique isotropic compactification

  7. Disconnecting Solar Magnetic Flux

    CERN Document Server

    DeForest, C E; McComas, D J

    2011-01-01

    Disconnection of open magnetic flux by reconnection is required to balance the injection of open flux by CMEs and other eruptive events. Making use of recent advances in heliospheric background subtraction, we have imaged many abrupt disconnection events. These events produce dense plasma clouds whose distinctie shape can now be traced from the corona across the inner solar system via heliospheric imaging. The morphology of each initial event is characteristic of magnetic reconnection across a current sheet, and the newly-disconnected flux takes the form of a "U"-shaped loop that moves outward, accreting coronal and solar wind material. We analyzed one such event on 2008 December 18 as it formed and accelerated at 20 m/s^2 to 320 km/s, expanding self-similarly until it exited our field of view 1.2 AU from the Sun. From acceleration and photometric mass estimates we derive the coronal magnetic field strength to be 8uT, 6 Rs above the photosphere, and the entrained flux to be 1.6x10^11 Wb (1.6x10^19 Mx). We mod...

  8. Coupled superconducting flux qubits

    NARCIS (Netherlands)

    Plantenberg, J.H.

    2007-01-01

    This thesis presents results of theoretical and experimental work on superconducting persistent-current quantum bits. These qubits offer an attractive route towards scalable solid-state quantum computing. The focus of this work is on the gradiometer flux qubit which has a special geometric design, t

  9. Dissolved organic carbon dynamics in a UK podzolic moorland catchment: linking storm hydrochemistry, flow path analysis and sorption experiments

    OpenAIRE

    Stutter, M. I.; S. M. Dunn; D. G. Lumsdon

    2012-01-01

    Better knowledge of spatial and temporal delivery of dissolved organic Carbon (DOC) in small catchments is required to understand the mechanisms behind reported long-term changes in C fluxes from some peatlands. We monitored two storms with contrasting seasons and antecedent conditions in a small upland UK moorland catchment. We examined DOC concentrations and specific UV absorbance (SUVA at 285 nm), together with solute concentrations required to undertake end member mixing analyses to defin...

  10. Dissolved organic carbon dynamics in a UK podzolic moorland catchment: linking storm hydrochemistry, flow path analysis and sorption experiments

    OpenAIRE

    Stutter, M. I.; S. M. Dunn; D. G. Lumsdon

    2012-01-01

    Better knowledge of spatial and temporal delivery of dissolved organic carbon (DOC) in small catchments is required to understand the mechanisms behind reported long-term changes in C fluxes from some peatlands. We monitored two storms with contrasting seasons and antecedent conditions in a small upland UK moorland catchment. We examined DOC concentrations and specific UV absorbance (SUVA at 285 nm), together with solute concentrations required to undertake end-member mixing analyses to defin...

  11. Volatile selenium flux from the great Salt Lake, Utah

    Science.gov (United States)

    Diaz, X.; Johnson, W.P.; Oliver, W.A.; Naftz, D.L.

    2009-01-01

    The removal mechanisms that govern Se concentrations in the Great Salt Lake are unknown despite this terminal lake being an avian habitat of hemispheric importance. However, the volatilization flux of Se from the Great Salt Lake has not been previously measured due to challenges of analysis in this hypersaline environment This paper presents results from recent field studies examining the spatial distribution of dissolved volatile Se (areally and with depth) in the south arm (main body) of the Great Salt Lake. The analyses involved collection of dissolved volatile Se in a cryofocusing trap system via sparging with helium. The cryotrapped volatile Se was digested with nitric acid and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Results show concentrations of dissolved volatile Se that increase with depth in the shallow brine, suggesting that phytoplankton in the open waters and bioherms in shallow sites (transport models corrected to simulate the highly saline environment of the south arm of the Great Salt Lake. The estimated annual flux of volatile Se was 1455 kg/year within a range from 560 to 3780 kg Se/year for the 95% confidence interval and from 970 to 2180 kg Se/year within the 68% confidence interval. ?? 2009 American Chemical Society.

  12. Silica Synthesis by Sponges: Unanticipated Molecular Mechanism

    Science.gov (United States)

    Morse, D. E.; Weaver, J. C.

    2001-12-01

    Oceanic diatoms, sponges and other organisms synthesize gigatons per year of silica from silicic acid, ultimately obtained from the weathering of rock. This biogenic silica exhibits a remarkable diversity of structures, many of which reveal a precision of nanoarchitectural control that exceeds the capabilities of human engineering. In contrast to the conditions of anthropogenic and industrial manufacture, the biological synthesis of silica occurs under mild physiological conditions of low temperatures and pressures and near-neutral pH. In addition to the differentiation between biological and abiotic processes governing silica formation, the biomolecular mechanisms controlling synthesis of these materials may offer insights for the development of new, environmentally benign routes for synthesis of nanostructurally controlled silicas and high-performance polysiloxane composites. We found that the needle-like silica spicules made by the marine sponge, Tethya aurantia, each contain an occluded axial filament of protein composed predominantly of repeating assemblies of three similar subunits we named "silicateins." To our surprise, analysis of the purified protein subunits and the cloned silicatein DNAs revealed that the silicateins are highly homologous to a family of hydrolytic enzymes. As predicted from this finding, we discovered that the silicatein filaments are more than simple, passive templates; they actively catalyze and spatially direct polycondensation to form silica, (as well as the phenyl- and methyl-silsesquioxane) from the corresponding silicon alkoxides at neutral pH and low temperature. Catalytic activity also is exhibited by the silicatein subunits obtained by disaggregation of the protein filaments and those produced from recombinant DNA templates cloned in bacteria. This catalytic activity accelerates the rate-limiting hydrolysis of the silicon alkoxide precursors. Genetic engineering, used to produce variants of the silicatein molecule with

  13. Treatment of dissolved perchlorate, nitrate, and sulfate using zero-valent iron and organic carbon.

    Science.gov (United States)

    Liu, YingYing; Ptacek, Carol J; Blowes, David W

    2014-05-01

    Waters containing ClO and dissolved NO, derived from detonated explosives and solid propellants, often also contain elevated concentrations of other dissolved constituents, including SO. Four column experiments, containing mixtures of silica sand, zero-valent Fe (ZVI) and organic C (OC) were conducted to evaluate the potential for simultaneous removal of NO, SO and ClO. Initially, the flow rate was maintained at 0.5 pore volumes (PV) d and then decreased to 0.1 PV d after 100 PV of flow. Nitrate concentrations decreased from 10.8 mg L (NO-N) to trace levels through NO reduction to NH using ZVI alone and through denitrification using OC. Observations from the mixture of ZVI and OC suggest a combination of NO reduction and denitrification. Up to 71% of input SO (24.5 ± 3.5 mg L) was removed in the column containing OC, and >99.7% of the input ClO (857 ± 63 μg L) was removed by the OC- and (ZVI + OC)-containing columns as the flow rate was maintained at 0.1 PV d. Nitrate and ClO removal followed first-order and zero-order rates, respectively. Nitrate >2 mg L (NO-N) inhibited ClO removal in the OC-containing column but not in the (ZVI + OC)-containing column. Sulfate did not inhibit ClO degradation within any of the columns.

  14. Molecular imprinting of bulk, microporous silica

    Science.gov (United States)

    Katz, Alexander; Davis, Mark E.

    2000-01-01

    Molecular imprinting aims to create solid materials containing chemical functionalities that are spatially organized by covalent or non-covalent interactions with imprint (or template) molecules during the synthesis process. Subsequent removal of the imprint molecules leaves behind designed sites for the recognition of small molecules, making the material ideally suited for applications such as separations, chemical sensing and catalysis. Until now, the molecular imprinting of bulk polymers and polymer and silica surfaces has been reported, but the extension of these methods to a wider range of materials remains problematic. For example, the formation of substrate-specific cavities within bulk silica, while conceptually straightforward, has been difficult to accomplish experimentally. Here we describe the imprinting of bulk amorphous silicas with single aromatic rings carrying up to three 3-aminopropyltriethoxysilane side groups; this generates and occupies microporosity and attaches functional organic groups to the pore walls in a controlled fashion. The triethoxysilane part of the molecules' side groups is incorporated into the silica framework during sol-gel synthesis, and subsequent removal of the aromatic core creates a cavity with spatially organized aminopropyl groups covalently anchored to the pore walls. We find that the imprinted silicas act as shape-selective base catalysts. Our strategy can be extended to imprint other functional groups, which should give access to a wide range of functionalized materials.

  15. Surface-modified silica colloidal crystals: nanoporous films and membranes with controlled ionic and molecular transport.

    Science.gov (United States)

    Zharov, Ilya; Khabibullin, Amir

    2014-02-18

    Nanoporous membranes are important for the study of the transport of small molecules and macromolecules through confined spaces and in applications ranging from separation of biomacromolecules and pharmaceuticals to sensing and controlled release of drugs. For many of these applications, chemists need to gate the ionic and molecular flux through the nanopores, which in turn depends on the ability to control the nanopore geometry and surface chemistry. Most commonly used nanoporous membrane materials are based on polymers. However, the nanostructure of polymeric membranes is not well-defined, and their surface is hard to modify. Inorganic nanoporous materials are attractive alternatives for polymers in the preparation of nanoporous membranes. In this Account, we describe the preparation and surface modification of inorganic nanoporous films and membranes self-assembled from silica colloidal spheres. These spheres form colloidal crystals with close-packed face centered cubic lattices upon vertical deposition from colloidal solutions. Silica colloidal crystals contain ordered arrays of interconnected three dimensional voids, which function as nanopores. We can prepare silica colloidal crystals as supported thin films on various flat solid surfaces or obtain free-standing silica colloidal membranes by sintering the colloidal crystals above 1000 °C. Unmodified silica colloidal membranes are capable of size-selective separation of macromolecules, and we can surface-modify them in a well-defined and controlled manner with small molecules and polymers. For the surface modification with small molecules, we use silanol chemistry. We grow polymer brushes with narrow molecular weight distribution and controlled length on the colloidal nanopore surface using atom transfer radical polymerization or ring-opening polymerization. We can control the flux in the resulting surface-modified nanoporous films and membranes by pH and ionic strength, temperature, light, and small molecule

  16. Sorption of Eu3+ onto nano-size silica-water interfaces

    Institute of Scientific and Technical Information of China (English)

    HU; Ping; YIN; Xiulan; ZHAO; Linghu; LI; Dien

    2005-01-01

    The sorption of Eu species onto nano-size silica-water interfaces is investigated at pH range of 1―8.5 and the initial Eu concentrations (CEu) of 2 × 10-5, 2 × 10-4 and 2 × 10-3 M using fluorescence spectroscopy. The sorption rate of Eu is initially low, but significantly increases at pH > 4. For the initial CEu of 2 × 10-5, 2 × 10-4 and 2 × 10-3 M, the dissolved Eu species are completely sorbed onto silica-water interfaces at pH = 4.75, ~5.8 and 6.6, respectively, with the respective sorption densities of ~1.58 × 10-8, 1.58 × 10-7 and 1.58 × 10-6 mol/m2. The sorbed Eu species at pH < 6 is aquo Eu3+, which is sorbed onto silica-water interfaces as an outer-sphere complex at pH < 5, but may be sorbed as an inner-sphere bidentate complex at 5 < pH < 6, due to the decrease of the NH2O to ~6 at pH = 6. At pH = 6 - 8, Eu(OH)2+, Eu(CO3)+ and Eu(CO3)2- form in the solutions, and Eu(CO3)+ is dominant at pH = ~7.5. These ions may be sorbed onto silica-water interfaces as inner-sphere bidentate complexes or multi-nuclear precipitates.

  17. New method for the direct determination of dissolved Fe(III) concentration in acid mine waters

    Science.gov (United States)

    To, T.B.; Nordstrom, D.K.; Cunningham, K.M.; Ball, J.W.; McCleskey, R.B.

    1999-01-01

    A new method for direct determination of dissolved Fe(III) in acid mine water has been developed. In most present methods, Fe(III) is determined by computing the difference between total dissolved Fe and dissolved Fe(II). For acid mine waters, frequently Fe(II) >> Fe(III); thus, accuracy and precision are considerably improved by determining Fe(III) concentration directly. The new method utilizes two selective ligands to stabilize Fe(III) and Fe(II), thereby preventing changes in Fe reduction-oxidation distribution. Complexed Fe(II) is cleanly removed using a silica-based, reversed-phase adsorbent, yielding excellent isolation of the Fe(III) complex. Iron(III) concentration is measured colorimetrically or by graphite furnace atomic absorption spectrometry (GFAAS). The method requires inexpensive commercial reagents and simple procedures that can be used in the field. Calcium(II), Ni(II), Pb(II), AI(III), Zn(II), and Cd(II) cause insignificant colorimetric interferences for most acid mine waters. Waters containing >20 mg of Cu/L could cause a colorimetric interference and should be measured by GFAAS. Cobalt(II) and Cr(III) interfere if their molar ratios to Fe(III) exceed 24 and 5, respectively. Iron(II) interferes when its concentration exceeds the capacity of the complexing ligand (14 mg/L). Because of the GFAAS elemental specificity, only Fe(II) is a potential interferent in the GFAAS technique. The method detection limit is 2 ??g/L (40 nM) using GFAAS and 20 ??g/L (0.4 ??M) by colorimetry.A new method for direct determination of dissolved Fe(III) in acid mine water has been developed. In most present methods, Fe(III) is determined by computing the difference between total dissolved Fe and dissolved Fe(II). For acid mine waters, frequently Fe(II)???Fe(III); thus, accuracy and precision are considerably improved by determining Fe(III) concentration directly. The new method utilizes two selective ligands to stabilize Fe(III) and Fe(II), thereby preventing changes

  18. AB initio free energy calculations of the solubility of silica in metallic hydrogen and application to giant planet cores

    Energy Technology Data Exchange (ETDEWEB)

    González-Cataldo, F. [Grupo de NanoMateriales, Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile); Wilson, Hugh F.; Militzer, B., E-mail: fgonzalez@lpmd.cl [Department of Earth and Planetary Science, University of California Berkeley, Berkeley, CA 94720 (United States)

    2014-05-20

    By combining density functional molecular dynamics simulations with a thermodynamic integration technique, we determine the free energy of metallic hydrogen and silica, SiO{sub 2}, at megabar pressures and thousands of degrees Kelvin. Our ab initio solubility calculations show that silica dissolves into fluid hydrogen above 5000 K for pressures from 10 and 40 Mbars, which has implications for the evolution of rocky cores in giant gas planets like Jupiter, Saturn, and a substantial fraction of known extrasolar planets. Our findings underline the necessity of considering the erosion and redistribution of core materials in giant planet evolution models, but they also demonstrate that hot metallic hydrogen is a good solvent at megabar pressures, which has implications for high-pressure experiments.

  19. MOUTH DISSOLVING FILM AND THEIR PATENT: AN OVERVIEW

    Directory of Open Access Journals (Sweden)

    Udhan Ravindra Radhakisan

    2012-09-01

    Full Text Available Now days the researchers are focusing on the fast dissolving dosage form (FDDF’s.The fast dissolving dosage forms includes the mouth dissolving tablets, mouth dissolving thin films .The alternative words used for these dosage forms are fast disintegrating, orodispersible, fast dissolving. The oral thin film technology (OTF’s is a dissolvable film technology have evolved from a purely confectionery novelty from a drug delivery platform. The OTH dosage form dissolves in the moth without need of water and within 10-15 seconds is the novelty of this dosage form. On the basis of this novelty many patents are available in the US country. Intraoral delivery is particularly beneficial to patients with special needs that are unable to tolerate traditional oral (entral/through GI track administration due to nausea, vomiting or dysphasia. Many pharmaceutical companies focusing on this Oral thin film technology. Today, this film technology is approved by is approved by FDA.

  20. Total dissolvable and dissolved iron isotopes in the water column of the Peru upwelling regime

    Science.gov (United States)

    Chever, Fanny; Rouxel, Olivier J.; Croot, Peter L.; Ponzevera, Emmanuel; Wuttig, Kathrin; Auro, Maureen

    2015-08-01

    Vertical distributions of iron (Fe) concentrations and isotopes were determined in the total dissolvable and dissolved pools in the water column at three coastal stations located along the Peruvian margin, in the core of the Oxygen Minimum Zone (OMZ). The shallowest station 121 (161 m total water depth) was characterized by lithogenic input from the continental plateau, yielding concentrations as high as 456 nM in the total dissolvable pool. At the 2 other stations (stations 122 and 123), Fe concentrations of dissolved and total dissolvable pools exhibited maxima in both surface and deep layers. Fe isotopic composition (δ56Fe) showed a fractionation toward lighter values for both physical pools throughout the water column for all stations with minimum values observed for the surface layer (between -0.64 and -0.97‰ at 10-20 m depth) and deep layer (between -0.03 and -1.25‰ at 160-300 m depth). An Fe isotope budget was established to determine the isotopic composition of the particulate pool. We observed a range of δ56Fe values for particulate Fe from +0.02 to -0.87‰, with lightest values obtained at water depth above 50 m. Such light values in the both particulate and dissolved pools suggest sources other than atmospheric dust deposition in the surface ocean, including lateral transport of isotopically light Fe. Samples collected at station 122 closest to the sediment show the lightest isotope composition in the dissolved and the particulate pools (-1.25 and -0.53‰ respectively) and high Fe(II) concentrations (14.2 ± 2.1 nM) consistent with a major reductive benthic Fe sources that is transferred to the ocean water column. A simple isotopic model is proposed to link the extent of Fe(II) oxidation and the Fe isotope composition of both particulate and dissolved Fe pools. This study demonstrates that Fe isotopic composition in OMZ regions is not only affected by the relative contribution of reductive and non-reductive shelf sediment input but also by

  1. Effect of Greenhouse Gases Dissolved in Seawater

    Directory of Open Access Journals (Sweden)

    Shigeki Matsunaga

    2015-12-01

    Full Text Available A molecular dynamics simulation has been performed on the greenhouse gases carbon dioxide and methane dissolved in a sodium chloride aqueous solution, as a simple model of seawater. A carbon dioxide molecule is also treated as a hydrogen carbonate ion. The structure, coordination number, diffusion coefficient, shear viscosity, specific heat, and thermal conductivity of the solutions have been discussed. The anomalous behaviors of these properties, especially the negative pressure dependence of thermal conductivity, have been observed in the higher-pressure region.

  2. Dissolve energy obesity by energy diet

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jung Heum [Sunmoon University, Asan (Korea)

    2000-07-01

    Every organism takes needed materials or energy from outside and excretes unessential things to outside. This is called a metabolism or energy metabolism. Calculating the amount of energy consumed by human in the world by converting to the amount of metabolism of an animal to survive, the weight of a human being is corresponding to an animal with a weigh of 40 ton. Human beings can find a solution to dissolve energy obesity or can maintain a massive status by finding a new energy source in the universe.

  3. Atomic Layer Deposition from Dissolved Precursors.

    Science.gov (United States)

    Wu, Yanlin; Döhler, Dirk; Barr, Maïssa; Oks, Elina; Wolf, Marc; Santinacci, Lionel; Bachmann, Julien

    2015-10-14

    We establish a novel thin film deposition technique by transferring the principles of atomic layer deposition (ALD) known with gaseous precursors toward precursors dissolved in a liquid. An established ALD reaction behaves similarly when performed from solutions. "Solution ALD" (sALD) can coat deep pores in a conformal manner. sALD offers novel opportunities by overcoming the need for volatile and thermally robust precursors. We establish a MgO sALD procedure based on the hydrolysis of a Grignard reagent.

  4. SYNTHESIS AND COATING OF ORDERED MESOPOROUS SILICA

    Institute of Scientific and Technical Information of China (English)

    Wei Guo; Guangsheng Luo; Yujun Wang

    2003-01-01

    1,3,5-trimethyl benzene (TMB) was used as organic swelling agent in O/W emulsions to template ultra-large mesoporous materials using the hydrothermal method. The silicas with well-defined mesopores and hydrothermally robust framework were characterized by X-ray diffraction, transmission electron microscopy and BET surface area analysis. The influence of the quantity of TMB during preparation was studied. It has been found that the TMB/CTAB ratio must be controlled for producing high pore volume materials. Polysulfone (PSU), as the usual extraction agent, was coated on the silicas with the solvent evaporation method to produce a solid separation medium. The adsorptivity and the surface area of the coated MCM were determined: 10% PSU coated MCM adsorbed twice as much phenol as the uncoated material, reaching 0.5 mg/g silica. It was found that the surface area of the coated material decreased rapidly with an increase of the PSU loading.

  5. Thermal resistance between amorphous silica nanoparticles

    Science.gov (United States)

    Meng, Fanhe; Elsahati, Muftah; Liu, Jin; Richards, Robert F.

    2017-05-01

    Nanoparticle-based materials have been used as thermal insulation in a variety of macroscale and microscale applications. In this work, we investigate the heat transfer between nanoparticles using non-equilibrium molecular dynamics simulations. We calculate the total thermal resistance and thermal boundary resistance between adjacent amorphous silica nanoparticles. Numerical results are compared to interparticle resistances determined from experimental measurements of heat transfer across packed silica nanoparticle beds. The thermal resistance between nanoparticles is shown to increase rapidly as the particle contact radius decreases. More significantly, the interparticle resistance depends strongly on the forces between particles, in particular, the presence or absence of chemical bonds between nanoparticles. In addition, the effect of interfacial force strength on thermal resistance increases as the nanoparticle diameter decreases. The simulations results are shown to be in good agreement with experimental results for 20 nm silica nanoparticles.

  6. Fused silica windows for solar receiver applications

    Science.gov (United States)

    Hertel, Johannes; Uhlig, Ralf; Söhn, Matthias; Schenk, Christian; Helsch, Gundula; Bornhöft, Hansjörg

    2016-05-01

    A comprehensive study of optical and mechanical properties of quartz glass (fused silica) with regard to application in high temperature solar receivers is presented. The dependence of rupture strength on different surface conditions as well as high temperature is analyzed, focussing particularly on damage by devitrification and sandblasting. The influence of typical types of contamination in combination with thermal cycling on the optical properties of fused silica is determined. Cleaning methods are compared regarding effectiveness on contamination-induced degradation for samples with and without antireflective coating. The FEM-aided design of different types of receiver windows and their support structure is presented. A large-scale production process has been developed for producing fused silica dome shaped windows (pressurized window) up to a diameter of 816 mm. Prototypes were successfully pressure-tested in a test bench and certified according to the European Pressure Vessel Directive.

  7. Functional Films from Silica/Polymer Nanoparticles

    Directory of Open Access Journals (Sweden)

    Tânia Ribeiro

    2014-05-01

    Full Text Available High performance functional coatings, based on hybrid organic/inorganic materials, are being developed to combine the polymer flexibility and ease of processing with the mechanical properties and versatility of inorganic materials. By incorporating silica nanoparticles (SiNPs in the polymeric matrices, it is possible to obtain hybrid polymer films with increased tensile strength and impact resistance, without decreasing the flexural properties of the polymer matrix. The SiNPs can further be used as carriers to impart other functionalities (optical, etc. to the hybrid films. By using polymer-coated SiNPs, it is possible to reduce particle aggregation in the films and, thus, achieve more homogeneous distributions of the inorganic components and, therefore, better properties. On the other hand, by coating polymer particles with silica, one can create hierarchically structured materials, for example to obtain superhydrophobic coatings. In this review, we will cover the latest developments in films prepared from hybrid polymer/silica functional systems.

  8. Vacuum arc on the polycrystalline silica cathode

    Directory of Open Access Journals (Sweden)

    D. V. Duhopel'nikov

    2014-01-01

    Full Text Available Thin films of silica and its compounds are used in modern technology to produce Li-ion batteries, wear-resistant and protective coatings, thin-films insulators, etc. This coating is produced with CVD methods, with magnetron sputtering systems or with electron-beam evaporation. The vacuum arc evaporation method, presently, is not used.The paper demonstrates a possibility for a long-term operation of vacuum arc evaporator with polycrystalline silica-aluminum alloy (90% of silica cathode and with magnetic system to create a variable form of arch-like magnetic field on the cathode surface. It was shown that archlike configuration of magnetic field provides a stable discharge and uniform cathode spots moving with the velocities up to 5 m/s with magnetic fields induction about 10 mT. Thus, there is no local melting of the cathode, and this provides its long-term work without chips, cracks and destruction. Cathodes spots move over the cathode surface leaving t big craters with melted edges on its surface. The craters size was 150-450μm. The cathode spot movement character and the craters on the cathode surface were like the spots movement, when working on the copper or aluminum cathodes. With the magnetic field induction less than 1 mT, the cathode spots movement was the same as that of on the silica mono-crystal without magnetic field. Thus, the discharge volt-ampere characteristics for different values of magnetic fields were obtained. Voltampere characteristics were increasing and were shifted to the higher voltage with increasing magnetic field. The voltage was 18.7-26.5 V for the arc current 30-140 A.So, it was confirmed that vacuum arc evaporation method could be used for effective evaporation of silica and silica-based alloys and for thin films deposition of this materials.

  9. Adsorption of mercury ions by mercapto-functionalized amorphous silica

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Quintanilla, Damian; Hierro, Isabel del; Fajardo, Mariano; Sierra, Isabel [Universidad Rey Juan Carlos, Departamento de Tecnologia Quimica y Ambiental, E.S.C.E.T, Mostoles, Madrid (Spain); Carrillo-Hermosilla, Fernando [Universidad de Castilla-La Mancha, Departamento de Quimica Inorganica, Organica y Bioquimica, Facultad de Quimicas, Ciudad Real (Spain)

    2006-02-01

    Amorphous silicas have been functionalized by two different methods. In the heterogeneous route the silylating agent, 3-chloropropyltriethoxysilane, was initially immobilized onto the silica surface to give the chlorinated silica Cl-Sil. In a second reaction, multifunctionalized N,S donor compounds were incorporated to obtain the functionalized silicas, which are denoted as L-Sil-Het (where L=mercaptothiazoline, mercaptopyridine or mercaptobenzothiazole). In the homogeneous route, the functionalization was achieved through a one-step reaction between the silica and an organic ligand containing the chelating functions; this gave the modified silicas denoted as L-Sil-Hom. The functionalized silicas were characterized by elemental analysis, IR spectroscopy and thermogravimetry. These materials were employed as adsorbents for mercury cations from aqueous and acetone solutions at room temperature. The results indicate that, in all cases, mercury adsorption was higher in the modified silicas prepared by the homogeneous method. (orig.)

  10. Stimuli-responsive polyaniline coated silica microspheres and their electrorheology

    Science.gov (United States)

    Park, Dae Eun; Choi, Hyoung Jin; Vu, Cuong Manh

    2016-05-01

    Silica/polyaniline (PANI) core-shell structured microspheres were synthesized by coating the surface of silica micro-beads with PANI and applied as a candidate inorganic/polymer composite electrorheological (ER) material. The silica micro-beads were initially modified using N-[(3-trimethoxysilyl)-propyl] aniline to activate an aniline functional group on the silica surface for a better PANI coating. The morphology of the PANI coating on the silica surface was examined by scanning electron microscopy and the silica/PANI core-shell structure was confirmed by transmission electron microscopy. The chemical structure of the particles was confirmed by Fourier transform infrared spectroscopy. Rotational rheometry was performed to confirm the difference in the ER properties between pure silica and silica/PANI microsphere-based ER fluids when dispersed in silicone oil.

  11. Dissolved Gases in Seawater and Sediments (Paper 7R0315)

    Science.gov (United States)

    Key, R. M.

    1987-07-01

    Certainly the most controversial results derived from the study of any dissolved gas concerned oxygen utilization rates in the North Atlantic. Jenkins (1982) estimated a net oxy-gen utilization rate (OUR) for the Beta triangle region of the North Atlantic (apices 26.5°N x 38.5°W, 32.5°N x 30.0°W, and 22.5°N x 28.5°W) of 5.7 moles of oxygen consumed m-2 yr-1 for the zone below 100m. He assumed that the oxygen distribution below the euphotic zone was stationary and steady state and therfore that the in situ oxygen consumption must be balanced by physical transport of oxygen into the area. His estimates were based on measured distributions of dissolved oxygen and the tracers 3He and 3H and a simple model which assumed lateral advection was small. The derived value or OUR was several times higher that previous estimates based on 14C and 15N incubation techniques. The OUR requires a downward flux of carbon from the photic zone of approximately 50 gCm-2yr-1 , which is again much higher that previous results. Jenkins and Goldman (1985) amplified the arguments in a study of seasonal oxygen cycling and primary production based on a ten year time series of measurements from the Panulirus station near Bermuda. Considering insolation, heat budgets and 3He/3H data they estimated a vertically integrated oxygen production rate of 5 Mm-2yr-1 and a subsequent new production of 50 gCm-2yr-1. The results were supported by calculations based on a second order turbulence closure model (Klein and Coste, 1984). These results have been challenged primarily on the basis of the spatial variability of the phenomenon!. Whatever the final outcome Jenkins has clearly demonstrated that the time has come to take a fresh look at oxygen utilization rates and primary productivity given the tools and modelling capabilities now at hand. The TTO data set will go a long way toward providing the necessary data set for the North Atlantic when the analyses are complete. Other studies have dealt with

  12. Triples, Fluxes, and Strings

    CERN Document Server

    De Boer, J; Hori, K; Keurentjes, A; Morgan, J; Morrison, Douglas Robert Ogston; Sethi, S K; Boer, Jan de; Dijkgraaf, Robbert; Hori, Kentaro; Keurentjes, Arjan; Morgan, John; Morrison, David R.; Sethi, Savdeep

    2002-01-01

    We study string compactifications with sixteen supersymmetries. The moduli space for these compactifications becomes quite intricate in lower dimensions, partly because there are many different irreducible components. We focus primarily, but not exclusively, on compactifications to seven or more dimensions. These vacua can be realized in a number ways: the perturbative constructions we study include toroidal compactifications of the heterotic/type I strings, asymmetric orbifolds, and orientifolds. In addition, we describe less conventional M and F theory compactifications on smooth spaces. The last class of vacua considered are compactifications on singular spaces with non-trivial discrete fluxes. We find a number of new components in the string moduli space. Contained in some of these components are M theory compactifications with novel kinds of ``frozen'' singularities. We are naturally led to conjecture the existence of new dualities relating spaces with different singular geometries and fluxes. As our stu...

  13. Atmospheric lepton fluxes

    Directory of Open Access Journals (Sweden)

    Gaisser Thomas K.

    2015-01-01

    Full Text Available This review of atmospheric muons and neutrinos emphasizes the high energy range relevant for backgrounds to high-energy neutrinos of astrophysical origin. After a brief historical introduction, the main distinguishing features of atmospheric νμ and νe are discussed, along with the implications of the muon charge ratio for the νµ / ν̅µ ratio. Methods to account for effects of the knee in the primary cosmic-ray spectrum and the energy-dependence of hadronic interactions on the neutrino fluxes are discussed and illustrated in the context of recent results from IceCube. A simple numerical/analytic method is proposed for systematic investigation of uncertainties in neutrino fluxes arising from uncertainties in the primary cosmic-ray spectrum/composition and hadronic interactions.

  14. Lobotomy of flux compactifications

    Science.gov (United States)

    Dibitetto, Giuseppe; Guarino, Adolfo; Roest, Diederik

    2014-05-01

    We provide the dictionary between four-dimensional gauged supergravity and type II compactifications on 6 with metric and gauge fluxes in the absence of supersymmetry breaking sources, such as branes and orientifold planes. Secondly, we prove that there is a unique isotropic compactification allowing for critical points. It corresponds to a type IIA background given by a product of two 3-tori with SO(3) twists and results in a unique theory (gauging) with a non-semisimple gauge algebra. Besides the known four AdS solutions surviving the orientifold projection to = 4 induced by O6-planes, this theory contains a novel AdS solution that requires non-trivial orientifold-odd fluxes, hence being a genuine critical point of the = 8 theory.

  15. Lobotomy of flux compactifications

    Energy Technology Data Exchange (ETDEWEB)

    Dibitetto, Giuseppe [Institutionen för fysik och astronomi, University of Uppsala,Box 803, SE-751 08 Uppsala (Sweden); Guarino, Adolfo [Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics,Bern University, Sidlerstrasse 5, CH-3012 Bern (Switzerland); Roest, Diederik [Centre for Theoretical Physics, University of Groningen,Nijenborgh 4 9747 AG Groningen (Netherlands)

    2014-05-15

    We provide the dictionary between four-dimensional gauged supergravity and type II compactifications on T{sup 6} with metric and gauge fluxes in the absence of supersymmetry breaking sources, such as branes and orientifold planes. Secondly, we prove that there is a unique isotropic compactification allowing for critical points. It corresponds to a type IIA background given by a product of two 3-tori with SO(3) twists and results in a unique theory (gauging) with a non-semisimple gauge algebra. Besides the known four AdS solutions surviving the orientifold projection to N=4 induced by O6-planes, this theory contains a novel AdS solution that requires non-trivial orientifold-odd fluxes, hence being a genuine critical point of the N=8 theory.

  16. Chitosan-Silica Hybrid Porous Membranes

    OpenAIRE

    Pandis, C.; S. Madeira; Matos, J.,; Kyritsis, A.; Mano, J. F.; Ribelles, J.L. Gómez

    2014-01-01

    Chitosan–silica porous hybrids were prepared by a novel strategy in order to improve the mechanical properties of chitosan (CHT) in the hydrogel state. The inorganic silica phase was introduced by sol–gel reactions in acidic medium inside the pores of already prepared porous scaffolds. In order to make the scaffolds insoluble in acidic media chitosan was cross-linked by genipin (GEN) with an optimum GEN concentration of 3.2 wt.%. Sol–gel reactions took place with Tetraethylorthosilicate (TEOS...

  17. Modified Silica Nanofibers with Antibacterial Activity

    Directory of Open Access Journals (Sweden)

    Ivana Veverková

    2016-01-01

    Full Text Available This study is focused on development of functionalized inorganic-organic nanofibrous material with antibacterial activity for wound dressing applications. The nanofibers combining poly(vinyl alcohol and silica were produced by electrospinning from the sol and thermally stabilized. The PVA/silica nanofibers surface was functionalized by silver and copper nanoparticles to ensure antibacterial activity. It was proven that quantity of adsorbed silver and copper nanoparticles depends on process time of adsorption. According to antibacterial tests results, this novel nanofibrous material shows a big potential for wound dressing applications due to its significant antibacterial efficiency.

  18. Measurement of muonium emission from silica aerogel

    CERN Document Server

    Bakule, P; Contreras, D; Esashi, M; Fujiwara, Y; Fukao, Y; Hirota, S; Iinuma, H; Ishida, K; Iwasaki, M; Kakurai, T; Kanda, S; Kawai, H; Kawamura, N; Marshall, G M; Masuda, H; Matsuda, Y; Mibe, T; Miyake, Y; Okada, S; Olchanski, K; Olin, A; Onishi, H; Saito, N; Shimomura, K; Strasser, P; Tabata, M; Tomono, D; Ueno, K; Yokoyama, K; Yoshida, S

    2013-01-01

    Emission of muonium ($\\mu^{+}e^{-}$) atoms from silica aerogel into vacuum was observed. Characteristics of muonium emission were established from silica aerogel samples with densities in the range from 29 mg cm$^{-3}$ to 178 mg cm$^{-3}$. Spectra of muonium decay times correlated with distances from the aerogel surfaces, which are sensitive to the speed distributions, follow general features expected from a diffusion process, while small deviations from a simple room-temperature thermal diffusion model are identified. The parameters of the diffusion process are deduced from the observed yields.

  19. Study on pure silica core optical fibers

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    An optimal refractive index profile of pure silica core optical fiber (PSCF) was designed, in combination with the characters of the modified chemical vapor deposition (MCVD) process. Techniques of preform fabrication by a new furnace round heating MCVD process and fiber drawing process were reviewed. Difficulties in doping fluorine in silica, widening the depressed-index cladding and maintaining the index of fiber core were discussed. Methods used to overcome these difficulties were given at the same time. Additionally, the optimal refractive index profiles of PSCF were presented.

  20. Olefin metathesis over UV-irradiated silica

    Science.gov (United States)

    Tanaka, Tsunehiro; Matsuo, Shigehiro; Maeda, Takashi; Yoshida, Hisao; Funabiki, Takuzo; Yoshida, Satohiro

    1997-11-01

    Photoirradiated silica evacuated at temperatures higher than 800 K was found to be active for olefin metathesis reactions. The analysis of products shows that the metalacyclobutane intermediate is likely. The instantaneous response of the reaction to the irradiation and the activity change with various UV filter showed that the reaction is induced by UV-excitation of silica. The correlation between the evacuation temperature and the activity showed that the surface free from water molecules plays a role in the reaction and the removal of isolated OH groups strongly relates to the generation of active sites.

  1. Ecodesign of ordered mesoporous silica materials.

    Science.gov (United States)

    Gérardin, Corine; Reboul, Julien; Bonne, Magali; Lebeau, Bénédicte

    2013-05-07

    Characterized by a regular porosity in terms of pore size and pore network arrangement, ordered mesoporous solids have attracted increasing interest in the last two decades. These materials have been identified as potential candidates for several applications. However, more environmentally friendly and economical synthesis routes of mesoporous silica materials were found to be necessary in order to develop these applications on an industrial scale. Consequently, ecodesign of ordered mesoporous silica has been considerably developed with the objective of optimizing the chemistry and the processing aspects of the material synthesis. In this review, the main strategies developed with this aim are presented and discussed.

  2. Ordered mesoporous silica materials with complicated structures

    KAUST Repository

    Han, Yu

    2012-05-01

    Periodically ordered mesoporous silicas constitute one of the most important branches of porous materials that are extensively employed in various chemical engineering applications including adsorption, separation and catalysis. This short review gives an introduction to recently developed mesoporous silicas with emphasis on their complicated structures and synthesis mechanisms. In addition, two powerful techniques for solving complex mesoporous structures, electron crystallography and electron tomography, are compared to elucidate their respective strength and limitations. Some critical issues and challenges regarding the development of novel mesoporous structures as well as their applications are also discussed. © 2011 Elsevier Ltd.

  3. Silica, silicosis and cancer in Finland.

    Science.gov (United States)

    Partanen, T; Jaakkola, J; Tossavainen, A

    1995-01-01

    Approximately 100 000 Finnish workers are currently employed in jobs and tasks that may involve exposure to airborne silica dust. The major industries involved are mining and quarrying; production of glass, ceramics, bricks and other building materials; metal industry, particularly iron and steel founding; and construction. Over 1500 cases of silicosis have occurred in Finland since 1935. Tuberculosis has been a frequent complication of silicosis. Results of studies from several countries strongly suggest that silica dust also causes lung cancer. The results of the relevant Finnish epidemiologic and industrial hygiene studies addressing cancer risk and exposure to quartz dust are summarized.

  4. Are benthic fluxes important for the availability of Si in the Gulf of Finland?

    Science.gov (United States)

    Tallberg, Petra; Heiskanen, Anna-Stiina; Niemistö, Juha; Hall, Per O. J.; Lehtoranta, Jouni

    2017-07-01

    We estimated the efflux of dissolved silicon (DSi) from sediments in the Gulf of Finland and compared it to sedimentation fluxes, burial of Si and existing data on Si loading and stocks, reassessing the reliability of existing Si budgets. Benthic fluxes of DSi measured in situ and in vitro were several times higher than estimates from diffusion calculations. The spatial variability in the open Gulf of Finland was relatively small, while both very high and low fluxes were measured from coastal areas. Fluxes were highest in late summer and lowest in early spring. In our re-assessed budget we present a new lower estimate for Si burial in the sediments, ca. 6 Gmol a- 1 and show that more than half of the sedimentation flux of Si is released back into the water column. Changes in the efficiency of internal DSi recycling may thus affect the prevalence of siliceous phytoplankton within the ecosystem, and the diatom spring bloom may be regulated by the functioning of this internal recycling pump. We also show that the seasonal variation in benthic DSi fluxes and dissolved phosphate fluxes is similar, and that a tentative connection between hypoxia and high DSi efflux exists.

  5. High Flux Calorimetry.

    Science.gov (United States)

    1984-05-05

    These approaches are based on proven principles which have served the thermal test community well for years. Other concepts hold promise of being able to...8217. --......- - ... .... - - The thermal test community has developed instrumentation which is quite suitable for the moderate, and relatively constant, flux...on the maximum phase II system fluence of 400 cal/cm2 . Second, the present thermal test community will have confidence in the performance of an

  6. Lobotomy of Flux Compactifications

    OpenAIRE

    Giuseppe Dibitetto; Adolfo Guarino(Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, Bern University, Sidlerstrasse 5, CH-3012 Bern, Switzerland); Diederik Roest

    2014-01-01

    We provide the dictionary between four-dimensional gauged supergravity and type II compactifications on $ \\mathbb{T} $ 6 with metric and gauge fluxes in the absence of supersymmetry breaking sources, such as branes and orientifold planes. Secondly, we prove that there is a unique isotropic compactification allowing for critical points. It corresponds to a type IIA background given by a product of two 3-tori with SO(3) twists and results in a unique theory (gauging) with a non-semisimple gauge...

  7. Photoluminescent Detection of Dissolved Underwater Trace Explosives

    Directory of Open Access Journals (Sweden)

    Tye Langston

    2010-01-01

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

  8. DISSOLVED CONCENTRATION LIMITS OF RADIOACTIVE ELEMENTS

    Energy Technology Data Exchange (ETDEWEB)

    NA

    2004-11-22

    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.

  9. Dissolved Organic Nitrogen in Mediterranean Ecosystems

    Institute of Scientific and Technical Information of China (English)

    M.DELGADO-BAQUERIZO; F.COVELO; A.GALLARDO

    2011-01-01

    Dissolved organic nitrogen (DON) in soils has recently gained increasing interest because it may be both a direct N source for plants and the dominant available N form in nutrient-poor soils, however, its prevalence in Mediterranean ecosystems remains unclear. The aims of this study were to i) estimate soil DON in a wide set of Mediterranean ecosystems and compare this levels with those for other ecosystems; ii) describe temporal changes in DON and dissolved inorganic nitrogen (DIN) forms (NH4+ and NO3-), and characterize spatial heterogeneity within plant communities; and iii) study the relative proportion of soil DON and DIN forms as a test of Schimel and Bennett's hypothesis that the prevalence of different N forms follows a gradient of nutrient availability. The study was carried out in eleven plant communities chosen to represent a wide spectrum of Mediterranean vegetation types, ranging from early to late successional status. DON concentrations in the studied Mediterranean plant communities (0-18.2 mg N kg-1) were consistently lower than those found in the literature for other ecosystems. We found high temporal and spatial variability in soil DON for all plant communities. As predicted by the Schimel and Bennett model for nutrient-poor ecosystems, DON dominance over ammonium and nitrate was observed for most plant communities in winter and spring soil samples. However, mineral-N dominated over DON in summer and autumn. Thus, soil water content may have an important effect on DON versus mineral N dominance in Mediterranean ecosystems.

  10. Early diagenetic production and sediment-water exchange of fluorescent dissolved organic matter in the coastal environment

    Science.gov (United States)

    Skoog, Annelie; Hall, Per O. J.; Hulth, Stefan; Paxéus, Nicklas; Van Der Loeff, Michiel Rutgers; Westerlund, Stig

    1996-10-01

    Fluorescence at wavelengths characteristic of humic substances (excitation 350 nm, emission 450 nm) have been used in this study to approximate concentrations of fluorescent dissolved organic material (FDOM). In situ regulated and unregulated benthic chambers, sediment cores, and laboratory tank incubations were used to study early diagenesis of FDOM in coastal marine sediments of the Gullmar Fjord, western Sweden. In the regulated in situ chambers, pH and oxygen were kept at relatively stable levels, while in the unregulated in situ chambers, pH and oxygen were left to decrease as a result of biological activity. FDOM porewater distributions and correlation between FDOM and parameters indicating mineralization showed that FDOM was formed in the sediment and should flux across the sediment-water interface. A substantial flux of FDOM was also observed during winter and spring conditions and during anoxic conditions fall. However, no flux was observed during oxic conditions fall. Modeling indicated that oxygen penetration depth was deeper during winter than during fall, i.e., the oxygen penetration depth increased during fall towards winter values. We suggest that as FeOOH was formed when oxygen penetration depths increased, FROM was sorbed to newly formed FeOOH, inhibiting FDOM flux over the sediment-water interface. In addition, at onset of anoxic conditions in the sediment surface layer in fall incubations, FDOM flux from sediment to overlying water increased substantially. Increases in anoxic FDOM fluxes were accompanied by increases in Fe and phosphate fluxes. We suggest that reductively dissolved FeOOH released sorbed FDOM. FDOM released from FeOOH by anoxic conditions was not resorbed when oxic conditions were resumed. This could be an effect of higher pH in overlying water as compared with porewater, inhibiting FeOOH sorption of FDOM.

  11. Physicochemical properties of the surfaces of silica species

    Science.gov (United States)

    Roshchina, T. M.; Shoniya, N. K.; Tegina, O. Ya.; Tkachenko, O. P.; Kustov, L. M.

    2017-02-01

    The results from studying the physicochemical characteristics of the adsorption of n-alkanes, arenes, and acetonitrile on silicas of different origins, silica gels, and silochromes are presented. It is shown that increasing the concentration of silanol groups reduces the role of dispersion interactions accompanied by the intensification of specific interactions on silica gels, compared to silochromes. According to diffuse reflectance FTIR spectroscopy data, the acidity of silanol groups on silica gel is in this case less pronounced.

  12. Modified monolithic silica capillary for preconcentration of catecholamines

    Institute of Scientific and Technical Information of China (English)

    Wei Chang; Tusyo-shi Komazu

    2009-01-01

    Preconcentration of catecholamines by the modified monolithic silica in the capillary was investigated in this study. In order to achieve a microchip-based method for determining catecholamines in the saliva, the monolithic silica was fabricated in the capillary and the monolithic silica was chemically modified by on-column reaction with phenylboronate. Different modified methods were compared. The concentration conditions were optimized. This study indicates the applicability of the modified monolithic silica capillary when it was used to concentrate catecholamines.

  13. Preparation of Al-Si-Ti Master Alloys by Electrolysis of Silica and Titania in Cryolite-Alumina Melts

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Aluminum-silicon-titanium master alloys were prepared in the laboratory by electrolysis of silica and titania dissolved in cryolite-alumina melts. Alloys containing up to 12 mass% Si and 2.6 mass% Ti were formed after about 90 min of electrolysis at 950℃. The current efficiency for the preparation of the Al-Si-Ti alloys varied with time, temperature and cathodic current density. It is concluded that this electrolytic method may be an interesting alternative to the direct metal mixing process for formation of Al-Si-Ti master alloys.

  14. Eddy Correlation Flux Measurement System

    Data.gov (United States)

    Oak Ridge National Laboratory — The eddy correlation (ECOR) flux measurement system provides in situ, half-hour measurements of the surface turbulent fluxes of momentum, sensible heat, latent heat,...

  15. Silica gel stimulates the hydrolysis of lecithin by phospholipase A

    NARCIS (Netherlands)

    Goerke, J.; Gier, J. de; Bonsen, P.P.M.

    1971-01-01

    1. 1. Silica gel stimulates the hydrolysis of aqueous lecithin suspensions by phospholipase A. The activation is slightly greater than that caused by ether and takes place equally well in bulk suspensions of silica gel or on thin-layer Chromatographic plates prepared with silica. 2. 2. The hydrolys

  16. 40 CFR 721.10119 - Siloxane modified silica nanoparticles (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Siloxane modified silica nanoparticles... Specific Chemical Substances § 721.10119 Siloxane modified silica nanoparticles (generic). (a) Chemical... as siloxane modified silica nanoparticles (PMN P-05-673) is subject to reporting under this...

  17. Human-driven changes in dissolved phosphorus deposition to the ocean

    Science.gov (United States)

    Myriokefalitakis, Stelios; Nenes, Athanasios; Kanakidou, Maria

    2016-04-01

    The atmospheric cycle of phosphorus (P) is parameterized in a global 3-D chemistry-transport model by taking into account the primary emissions of total (TP) and dissolved P (PO4) associated with dust, sea-salt, bioaerosols and combustion particles of anthropogenic and natural sources. Mineral sources are calculated to contribute by roughly 80% to the TP emissions. The calculated annual deposition flux of PO4 presents strong spatial and temporal variability with about 30% occurring over the ocean. Sensitivity simulations using preindustrial (year 1850), present (year 2008) and future (year 2100) anthropogenic and biomass burning emission scenarios, indicate that an increase in dust-P dissolution flux may have occurred in the last 150 years due to increasing atmospheric acidity due to anthropogenic emissions. On the opposite, a decrease of dust-P containing dissolution flux is projected for near future, since air-quality regulations are expected to reduce atmospheric acidity compared to present-day. Present day simulations of atmospheric P aerosol concentrations and deposition fluxes compare satisfactorily with available observations, thus, providing confidence to the model results. This work has been co-financed by the European Union (European Social Fund - ESF) and Greek national funds through the Operational Program "Education and Lifelong Learning" of the National Strategic Reference Framework (NSRF) - Research Funding Program: ARISTEIA - PANOPLY (Pollution Alters Natural Aerosol Composition: implications for Ocean Productivity, cLimate and air qualitY) grant.

  18. Dissolved carbon leaching from soil is a crucial component of the net ecosystem carbon balance

    DEFF Research Database (Denmark)

    Kindler, Reimo; Siemens, Jan; Kaiser, Klaus;

    2011-01-01

    Estimates of carbon leaching losses from different land use systems are few and their contribution to the net ecosystem carbon balance is uncertain. We investigated leaching of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and dissolved methane (CH4), at forests, grasslands......, and croplands across Europe. Biogenic contributions to DIC were estimated by means of its d13C signature. Leaching of biogenic DIC was 8.34.9 gm2 yr1 for forests, 24.17.2 gm2 yr1 for grasslands, and 14.64.8 gm2 yr1 for croplands. DOC leaching equalled 3.51.3 gm2 yr1 for forests, 5.32.0 gm2 yr1 for grasslands...... (hydr)oxides. Partial pressures of CO2 in soil air and soil pH determined DIC concentrations and fluxes, but soil solutions were often supersaturated with DIC relative to soil air CO2. Leaching losses of biogenic carbon (DOC plus biogenic DIC) from grasslands equalled 5–98% (median: 22%) of net...

  19. Cellulase activity and dissolved organic carbon release from lignocellulose macrophyte-derived in four trophic conditions.

    Science.gov (United States)

    Bottino, Flávia; Cunha-Santino, Marcela Bianchessi; Bianchini, Irineu

    2016-01-01

    Considering the importance of lignocellulose macrophyte-derived for the energy flux in aquatic ecosystems and the nutrient concentrations as a function of force which influences the decomposition process, this study aims to relate the enzymatic activity and lignocellulose hydrolysis in different trophic statuses. Water samples and two macrophyte species were collected from the littoral zone of a subtropical Brazilian Reservoir. A lignocellulosic matrix was obtained using aqueous extraction of dried plant material (≈40°C). Incubations for decomposition of the lignocellulosic matrix were prepared using lignocelluloses, inoculums and filtered water simulating different trophic statuses with the same N:P ratio. The particulate organic carbon and dissolved organic carbon (POC and DOC, respectively) were quantified, the cellulase enzymatic activity was measured by releasing reducing sugars and immobilized carbon was analyzed by filtration. During the cellulose degradation indicated by the cellulase activity, the dissolved organic carbon daily rate and enzyme activity increased. It was related to a fast hydrolysable fraction of cellulose that contributed to short-term carbon immobilization (ca. 10 days). After approximately 20 days, the dissolved organic carbon and enzyme activity were inversely correlated suggesting that the respiration of microorganisms was responsible for carbon mineralization. Cellulose was an important resource in low nutrient conditions (oligotrophic). However, the detritus quality played a major role in the lignocelluloses degradation (i.e., enzyme activity) and carbon release.

  20. Cellulase activity and dissolved organic carbon release from lignocellulose macrophyte-derived in four trophic conditions

    Directory of Open Access Journals (Sweden)

    Flávia Bottino

    2016-06-01

    Full Text Available Abstract Considering the importance of lignocellulose macrophyte-derived for the energy flux in aquatic ecosystems and the nutrient concentrations as a function of force which influences the decomposition process, this study aims to relate the enzymatic activity and lignocellulose hydrolysis in different trophic statuses. Water samples and two macrophyte species were collected from the littoral zone of a subtropical Brazilian Reservoir. A lignocellulosic matrix was obtained using aqueous extraction of dried plant material (≈40 °C. Incubations for decomposition of the lignocellulosic matrix were prepared using lignocelluloses, inoculums and filtered water simulating different trophic statuses with the same N:P ratio. The particulate organic carbon and dissolved organic carbon (POC and DOC, respectively were quantified, the cellulase enzymatic activity was measured by releasing reducing sugars and immobilized carbon was analyzed by filtration. During the cellulose degradation indicated by the cellulase activity, the dissolved organic carbon daily rate and enzyme activity increased. It was related to a fast hydrolysable fraction of cellulose that contributed to short-term carbon immobilization (ca. 10 days. After approximately 20 days, the dissolved organic carbon and enzyme activity were inversely correlated suggesting that the respiration of microorganisms was responsible for carbon mineralization. Cellulose was an important resource in low nutrient conditions (oligotrophic. However, the detritus quality played a major role in the lignocelluloses degradation (i.e., enzyme activity and carbon release.

  1. Gases dissolved in groundwaters: analytical methods and examples of applications in central Italy

    Energy Technology Data Exchange (ETDEWEB)

    Chiodini, G. [Osservatorio Vesuviano, Napoli (Italy)

    1998-12-31

    A quick method to analyse dissolved gases in natural waters is described. First partial results show that useful information on the geochemical processes affecting a variety of hydrogeological systems can be obtained from the study of dissolved gases. The study of the CO{sub 2} dissolved in the groundwaters of Central Italy indicates that one of the main factor controlling the P{sub CO2} values in these groundwaters is the input of a deeply originated gas phase. These leakage processes generally occur in correspondence with buried structural highs of the carbonate basement acting as both traps for the gas produced at depth and sources of high CO{sub 2} fluxes toward the surface. This CO{sub 2} causes significant increases in the P{sub {sub O}2} values of shallow groundwaters. The total carbon balance of two regional aquifers has been used to estimate the production rate of deep CO{sub 2} in Tyrrhenian Central Italy. These average production rates, with 5 X 10{sup 6}mol km{sup -2} y{sup -1} both at Stifone and at Colli Albani, are five times higher than the value assumed as baseline for areas of high heat flow, i.e., 10{sup 6} km{sup -2} y{sup -1}.

  2. Distal transport of dissolved hydrothermal iron in the deep South Pacific Ocean.

    Science.gov (United States)

    Fitzsimmons, Jessica N; Boyle, Edward A; Jenkins, William J

    2014-11-25

    Until recently, hydrothermal vents were not considered to be an important source to the marine dissolved Fe (dFe) inventory because hydrothermal Fe was believed to precipitate quantitatively near the vent site. Based on recent abyssal dFe enrichments near hydrothermal vents, however, the leaky vent hypothesis [Toner BM, et al. (2012) Oceanography 25(1):209-212] argues that some hydrothermal Fe persists in the dissolved phase and contributes a significant flux of dFe to the global ocean. We show here the first, to our knowledge, dFe (hydrothermally derived based on its correlation with primordial (3)He and dissolved Mn (dFe:(3)He of 0.9-2.7 × 10(6)). Given the known sites of hydrothermal venting in these regions, this dFe must have been transported thousands of kilometers away from its vent site to reach our sampling stations. Additionally, changes in the size partitioning of the hydrothermal dFe between soluble (vents indicate that dFe transformations continue to occur far from the vent source. This study confirms that although the southern East Pacific Rise only leaks 0.02-1% of total Fe vented into the abyssal Pacific, this dFe persists thousands of kilometers away from the vent source with sufficient magnitude that hydrothermal vents can have far-field effects on global dFe distributions and inventories (≥3% of global aerosol dFe input).

  3. Lithogenic fluxes in the Bay of Bengal measured by sediment traps

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.; VijayKumar, B.; Parthiban, G.; Ittekkot, V.; Nair, R.R.

    % for opal, Si concentrations were multiplied by 2.4 to calculate biogenic opal content. Lithogenic fluxes were estimated by weighing the material remaining after removal of carbonate (30% v/v dilute acetic acid), organic matter (with 30% hydrogen peroxide... solution) and biogenic silica (with 1 M sodium carbonate). Dilute acetic acid and hydrogen peroxide does not attack clay minerals significantly. Leaching of the lithogenic fraction by 1 M sodium carbonate is generally less than 1% of the total lithogenic...

  4. Hydrologic Controls on Dissolved Organic Matter Mobilization and Transport within Undisturbed Soils

    Science.gov (United States)

    Xu, N.; Saiers, J.

    2007-12-01

    Dissolved organic matter (DOM) in soils plays an important role in the transport of nutrients and contaminants through the terrestrial environment. Subsurface pathways deliver a significant portion of carbon to streams that drain forested and agricultural watersheds. Although the importance of rainfall events to the DOM soil-water flux is well known, the hydrologic factors that govern this flux have not been fully examined. The primary purpose of this study is to investigate the soil and rainfall characteristics controlling the mobilization and transport of DOM in undisturbed soils. Intact soil columns including topsoil and subsoil layers were taken from the Harvard forest in Petersham, MA. Unsaturated flow conditions were maintained by applying suction to the bottom of the soil columns. The columns were irrigated by series of interrupted rainfall events using the same total volume of artificial rain water. Preliminary experiments showed continuous leaching of DOM (measured by dissolved organic carbon) with an initial peak in concentration that coincided with the passage of the wetting front. The leached DOM was also characterized by UV absorbance, fluorescence spectroscopy in the emission mode, and additional spectroscopic derived indexes such as the humification index. Ongoing column experiments are focusing on the effects of rainfall intensity, frequency, and rainfall history on DOM mobilization and transport through natural, structured soils. These investigations can elucidate the influence of factors that are associated with climate change on DOC dynamics. Results of our analyses should also provide insight into the mechanisms that govern DOM mobilization in soils.

  5. Dissolved platinum in major rivers of East Asia: Implications for the oceanic budget

    Science.gov (United States)

    Soyol-Erdene, Tseren-Ochir; Huh, Youngsook

    2012-06-01

    Dissolved platinum concentrations of eleven large pristine river systems in East Asia (˜200 samples) were determined to better constrain the oceanic platinum budget. Most samples had concentrations less than 1.4 pM; relatively high concentrations up to 5.8 pM were measured in only approximately 6% of the samples. The median Pt concentrations of the individual river systems had only a small range, from 0.18 pM (Duman) to 0.63 pM (Huang He), and the difference in Pt yield mainly resulted from the difference in runoff. The rivers draining the eastern Tibetan Plateau - the Salween, Mekong, Chang Jiang (Yangtze), Hong (Red), and Huang He (Yellow) - had higher Pt yield than the rivers of the Russian Far East - the Amur, Lena, Yana, Indigirka, and Kolyma. If the discharge-weighted mean Pt concentration of our samples (0.36 pM) is extrapolated globally, the estimated riverine flux of dissolved Pt to the ocean is 13 × 103 mol y-1. Based on this riverine flux, the estimated oceanic residence time of Pt is 24 ± 10 kyrs. A 50% release and 50% uptake of Pt in estuaries would modify this to 16 kyrs and 45 kyrs, respectively.

  6. [Determination of partition coefficient of dissolved gases in transformer oil using phase ratio variation method and static headspace gas chromatography].

    Science.gov (United States)

    Zhao, Jinghong; Wang, Hailong; Liu, Wenmin; Zhou, Yansheng; Guan, Yafeng

    2004-05-01

    The partition coefficients of dissolved gases in transformer oil were determined using a phase ratio variation method and static headspace gas chromatography (GC). A pressure balancing and gas volume-metering device was connected to the vent of a sample loop on a six-port injection valve of the GC. The gas phase sample from the headspace vial of 25 mL was transferred to an 80 microL sample-loop through a fused silica capillary of 0.53 mm i.d., and then separated and determined quantitatively by GC. A 2 m x 1 mm i.d. GDX502 micro-packed column was used for the separation. Five different gas-liquid volume ratios in the headspace vials were measured at different equilibrium concentrations. The partition coefficients of hydrocarbon gases including methane, acetylene, ethylene, ethane and propane dissolved in transformer oil were determined by using linear regression analysis at 20 degrees C and 50 degrees C separately. The errors between the real values and regression values from experimental data were less than 4.14% except methane. Fundamental data for on-line measurement of dissolved gases in transformer oil are provided by GC.

  7. Geochemistry of dispersed sedimentary matter and its fluxes in the water column of the Caspian Sea

    Science.gov (United States)

    Lukashin, V. N.; Lisitzin, A. P.

    2016-09-01

    The first data on the chemical composition of dispersed matter from sedimentary traps are reported. The suspended components of sedimentary matter (amorphous silica, organic matter, carbonates, and lithogenic material, as well as Fe, Mn, and minor elements) are considered. As a result, it is shown that the intraannual variability in vertical fluxes of sedimentary matter is characterized by a seasonal increase in spring and autumn. The high fluxes of the components of sedimentary matter on the northern and southern slopes of the Derbent Basin in winter are explained by precipitation of material from the nepheloid layer that forms over the contour current.

  8. Nanostructured Mesoporous Silicas for Bone Tissue Regeneration

    Directory of Open Access Journals (Sweden)

    Isabel Izquierdo-Barba

    2008-01-01

    Full Text Available The research on the development of new biomaterials that promote bone tissue regeneration is receiving great interest by the biomedical scientific community. Recent advances in nanotechnology have allowed the design of materials with nanostructure similar to that of natural bone. These materials can promote new bone formation by inducing the formation of nanocrystalline apatites analogous to the mineral phase of natural bone onto their surfaces, i.e. they are bioactive. They also stimulate osteoblast proliferation and differentiation and, therefore, accelerate the healing processes. Silica-based ordered mesoporous materials are excellent candidates to be used as third generation bioceramics that enable the adsorption and local control release of biological active agents that promote bone regeneration. This local delivery capability together with the bioactive behavior of mesoporous silicas opens up promising expectations in the bioclinical field. In this review, the last advances in nanochemistry aimed at designing and tailoring the chemical and textural properties of mesoporous silicas for biomedical applications are described. The recent developed strategies to synthesize bioactive glasses with ordered mesopore arrangements are also summarized. Finally, a deep discussion about the influence of the textural parameters and organic modification of mesoporous silicas on molecules adsorption and controlled release is performed.

  9. Influence of Nano Silica on Alkyd Films

    DEFF Research Database (Denmark)

    Nikolic, Miroslav

    of alkyd curing affecting the tested mechanical properties. Hydrophilic, colloidal nano silica was seen to have limited effect in improving the mechanical properties due to problems in properly dispersing and attaining good surface interactions with the hydrophobic alkyd polymer. Efforts in increasing...

  10. Mesoporous silica nanoparticles for active corrosion protection.

    Science.gov (United States)

    Borisova, Dimitriya; Möhwald, Helmuth; Shchukin, Dmitry G

    2011-03-22

    This work presents the synthesis of monodisperse, mesoporous silica nanoparticles and their application as nanocontainers loaded with corrosion inhibitor (1H-benzotriazole (BTA)) and embedded in hybrid SiOx/ZrOx sol-gel coating for the corrosion protection of aluminum alloy. The developed porous system of mechanically stable silica nanoparticles exhibits high surface area (∼1000 m2·g(-1)), narrow pore size distribution (d∼3 nm), and large pore volume (∼1 mL·g(-1)). As a result, a sufficiently high uptake and storage of the corrosion inhibitor in the mesoporous nanocontainers was achieved. The successful embedding and homogeneous distribution of the BTA-loaded monodisperse silica nanocontainers in the passive anticorrosive SiOx/ZrOx film improve the wet corrosion resistance of the aluminum alloy AA2024 in 0.1 M sodium chloride solution. The enhanced corrosion protection of this newly developed active system in comparison to the passive sol-gel coating was observed during a simulated corrosion process by the scanning vibrating electrode technique (SVET). These results, as well as the controlled pH-dependent release of BTA from the mesoporous silica nanocontainers without additional polyelectrolyte shell, suggest an inhibitor release triggered by the corrosion process leading to a self-healing effect.

  11. Metal doped hybrid silica membranes for separation

    NARCIS (Netherlands)

    Ru, Yanfei

    2014-01-01

    The present study describes the e ect of di erent factors such as the type of dopants and the percentage of dopants on the stability and permeance of membranes. Di erent dopants such as zirconia, yttrium were used to produce organic-inorganic hybrid silica membranes. During the programme, zirconia d

  12. Silica sand resources in the Netherlands

    NARCIS (Netherlands)

    Meulen, M.J. van der; Westerhoff, W.E.; Menkovic, A.; Gruijters, S.H.L.L.; Dubelaar, C.W.; Maljers, D.

    2009-01-01

    Silica sand, (almost) pure quartz sand, is a valuable and scarce mineral resource within the shallow Dutch subsurface. High-grade deposits are exploited in the southeastemmost part of the country, as raw material for the glass, ceramic, chemical and other process industries. Dutch land-use policy re

  13. Phase behavior of colloidal silica rods

    NARCIS (Netherlands)

    Kuijk, A.; Byelov, D.; Petukhov, A.V.; van Blaaderen, A.; Imhof, A.

    2012-01-01

    Recently, a novel colloidal hard-rod-like model system was developed which consists of silica rods [Kuijk et al., JACS, 2011, 133, 2346]. Here, we present a study of the phase behavior of these rods, for aspect ratios ranging from 3.7 to 8.0. By combining real-space confocal laser scanning microscop

  14. Kinetics of silica-phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Duffy, C.J.

    1993-07-01

    In addition to the stable silica polymorph quartz, several metastable silica phases are present in Yucca Mountain. The conversion of these phases to quartz is accompanied by volume reduction and a decrease in the aqueous silica activity, which may destabilize clinoptilolite and mordenite. The primary reaction sequence for the silica phases is from opal or glass to disordered opal-CT, followed by ordering of the opal-CT and finally by the crystallization of quartz. The ordering of opal-CT takes place in the solid state, whereas the conversion of opal-CT takes place through dissolution-reprecipitation involving the aqueous phase. It is proposed that the rate of conversion of opal-CT to quartz is controlled by diffusion of defects out of a disordered surface layer formed on the crystallizing quartz. The reaction rates are observed to be dependent on temperature, pressure, degree of supersaturation, and pH. Rate equations selected from the literature appear to be consistent with observations at Yucca Mountain.

  15. Supra-amphiphilic transparent mesoporous silica coating

    Institute of Scientific and Technical Information of China (English)

    MA Jin; YANG Zhenglong; QU Xiaozhong; YANG Zhenzhong

    2006-01-01

    Transparent mesoporous silica coatings were achieved by conventional sol-gel process. The obtained coatings display permanent supraamphiphilicity, transparent appearance and good wetting property with very fast spread rate. Incorporation of functional materials such as crystalline titania nanoparticles into the coatings was also carried out without affecting the transparency and supraamphiphilicity.

  16. Kinetics of silica-phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Duffy, C.J.

    1993-07-01

    In addition to the stable silica polymorph quartz, several metastable silica phases are present in Yucca Mountain. The conversion of these phases to quartz is accompanied by volume reduction and a decrease in the aqueous silica activity, which may destabilize clinoptilolite and mordenite. The primary reaction sequence for the silica phases is from opal or glass to disordered opal-CT, followed by ordering of the opal-CT and finally by the crystallization of quartz. The ordering of opal-CT takes place in the solid state, whereas the conversion of opal-CT takes place through dissolution-reprecipitation involving the aqueous phase. It is proposed that the rate of conversion of opal-CT to quartz is controlled by diffusion of defects out of a disordered surface layer formed on the crystallizing quartz. The reaction rates are observed to be dependent on temperature, pressure, degree of supersaturation, and pH. Rate equations selected from the literature appear to be consistent with observations at Yucca Mountain.

  17. THERMAL MUONIUM IN VACUO FROM SILICA AEROGELS

    NARCIS (Netherlands)

    Schwarz, Willi; Ebert, Volker; Geerds, Hans; Jungmann, Klaus-Peter; Kirches, Stefan; Koppe, Stefan; Maas, Frank Ewald; Mundinger, Hans Juergen; zu Putlitz, Gisbert; Rosenkranz, Juergen; Schaefer, Willi; Schiff, Guenther; Zhang, Zhizhang; Boshier, MG; Hughes, V.W.

    1992-01-01

    Muonium atoms have been observed emerging into vacuum from silica aerogel surfaces with a thermal velocity distribution corresponding to a temperature of 298(10) K after stopping positive muons from a subsurface muon beam. Yields up to 2.3(3)% could be achieved for aerogel samples of 160 mg/cm3 dens

  18. Saccharide modified silica particles by enzymatic grafting

    NARCIS (Netherlands)

    Loos, Katja; Braunmühl, Volker von; Stadler, Reimund; Landfester, K; Spiess, HW

    1997-01-01

    The surface of silica particles has been chemically modified with oligo- or poly-(α,1→4)-D-glucopyranose (amylose) chains of various length by covalently attaching maltoheptaose derivatives to the solid support and enzymatic polymerization of glucose-1-phosphate with a potato phosphorylase as cataly

  19. Immunological Effects of Silica and Asbestos

    Institute of Scientific and Technical Information of China (English)

    Takemi Otsuki; Fuminori Hyodoh; Ayako Ueki; Yasumitsu Nishimura; Megumi Maeda; Shuko Murakami; Hiroaki Hayashi; Yoshie Miura; Masayasu Kusaka; Takashi Nakano; Kazuya Fukuoka; Takumi Kishimoto

    2007-01-01

    Silicosis patients (SILs) and patients who have been exposed to asbestos develop not only respiratory diseases but also certain immunological disorders. In particular, SIL sometimes complicates autoimmune diseases such as systemic scleroderma, rheumatoid arthritis (known as Caplan syndrome), and systemic lupus erythematoses. In addition, malignant complications such as lung cancer and malignant mesothelioma often occurr in patients exposed to asbestos, and may be involved in the reduction of tumor immunity. Although silica-induced disorders of autoimmunity have been explained as adjuvant-type effects of silica, more precise analyses are needed and should reflect the recent progress in immunomolecular findings. A brief summary of our investigations related to the immunological effects of silica/asbestos is presented. Recent advances in immunomolecular studies led to detailed analyses of the immunological effects of asbestos and silica. Both affect immuno-competent cells and these effects may be associated with the pathophysiological development of complications in silicosis and asbestos-exposed patients such as the occurrence of autoimmune disorders and malignant tumors, respectively. In addition,immunological analyses may lead to the development of new clinical tools for the modification of the pathophysiological aspects of diseases such as the regulation of autoimmunity or tumor immunity using cellmediated therapies, various cytokines, and molecule-targeting therapies. In particular, as the incidence of asbestosrelated malignancies is increasing and such malignancies have been a medical and social problem since the summer of 2005 in Japan, efforts should be focused on developing a cure for these diseases to eliminate nationwide anxiety.

  20. Mathematical Modelling of Silica Scaling Deposition in Geothermal Wells

    Science.gov (United States)

    Nizami, M.; Sutopo

    2016-09-01

    Silica scaling is widely encountered in geothermal wells in which produce two-phase geothermal fluid. Silica scaling could be formed due to chemical reacting by mixing a geothermal fluid with other geothermal fluid in different compositions, or also can be caused by changes in fluid properties due to changes pressure and temperature. One of method to overcome silica scaling which is occurred around geothermal well is by workover operation. Modelling of silica deposition in porous medium has been modeled in previously. However, the growth of silica scaling deposition in geothermal wells has never been modeled. Modelling of silica deposition through geothermal is important aspects to determine depth of silica scaling growth and best placing for workover device to clean silica scaling. This study is attempted to develop mathematical models for predicting silica scaling through geothermal wells. The mathematical model is developed by integrating the solubility-temperature correlation and two-phase pressure drop coupled wellbore fluid temperature correlation in a production well. The coupled model of two-phase pressure drop and wellbore fluid temperature correlation which is used in this paper is Hasan-Kabir correlation. This modelling is divided into two categories: single and two phase fluid model. Modelling of silica deposition is constrained in temperature distribution effect through geothermal wells by solubility correlation for silica. The results of this study are visualizing the growth of silica scaling thickness through geothermal wells in each segment of depth. Sensitivity analysis is applied in several parameters, such as: bottom-hole pressure, temperature, and silica concentrations. Temperature is most impact factor for silica scaling through geothermal wellbore and depth of flash point. In flash point, silica scaling thickness has reached maximum because reducing of mole in liquid portion.

  1. Health hazards due to the inhalation of amorphous silica.

    Science.gov (United States)

    Merget, R; Bauer, T; Küpper, H U; Philippou, S; Bauer, H D; Breitstadt, R; Bruening, T

    2002-01-01

    Occupational exposure to crystalline silica dust is associated with an increased risk for pulmonary diseases such as silicosis, tuberculosis, chronic bronchitis, chronic obstructive pulmonary disease (COPD) and lung cancer. This review summarizes the current knowledge about the health effects of amorphous (non-crystalline) forms of silica. The major problem in the assessment of health effects of amorphous silica is its contamination with crystalline silica. This applies particularly to well-documented pneumoconiosis among diatomaceous earth workers. Intentionally manufactured synthetic amorphous silicas are without contamination of crystalline silica. These synthetic forms may be classified as (1) wet process silica, (2) pyrogenic ("thermal" or "fumed") silica, and (3) chemically or physically modified silica. According to the different physicochemical properties, the major classes of synthetic amorphous silica are used in a variety of products, e.g. as fillers in the rubber industry, in tyre compounds, as free-flow and anti-caking agents in powder materials, and as liquid carriers, particularly in the manufacture of animal feed and agrochemicals; other uses are found in toothpaste additives, paints, silicon rubber, insulation material, liquid systems in coatings, adhesives, printing inks, plastisol car undercoats, and cosmetics. Animal inhalation studies with intentionally manufactured synthetic amorphous silica showed at least partially reversible inflammation, granuloma formation and emphysema, but no progressive fibrosis of the lungs. Epidemiological studies do not support the hypothesis that amorphous silicas have any relevant potential to induce fibrosis in workers with high occupational exposure to these substances, although one study disclosed four cases with silicosis among subjects exposed to apparently non-contaminated amorphous silica. Since the data have been limited, a risk of chronic bronchitis, COPD or emphysema cannot be excluded. There is no study

  2. Silica-titania composite aerogel photocatalysts by chemical liquid deposition of titania onto nanoporous silica scaffolds.

    Science.gov (United States)

    Zu, Guoqing; Shen, Jun; Wang, Wenqin; Zou, Liping; Lian, Ya; Zhang, Zhihua

    2015-03-11

    Silica-titania composite aerogels were synthesized by chemical liquid deposition of titania onto nanoporous silica scaffolds. This novel deposition process was based on chemisorption of partially hydrolyzed titanium alkoxides from solution onto silica nanoparticle surfaces and subsequent hydrolysis and condensation to afford titania nanoparticles on the silica surface. The titania is homogeneously distributed in the silica-titania composite aerogels, and the titania content can be effectively controlled by regulating the deposition cycles. The resultant composite aerogel with 15 deposition cycles possessed a high specific surface area (SSA) of 425 m(2)/g, a small particle size of 5-14 nm, and a large pore volume and pore size of 2.41 cm(3)/g and 18.1 nm, respectively, after heat treatment at 600 °C and showed high photocatalytic activity in the photodegradation of methylene blue under UV-light irradiation. Its photocatalytic activity highly depends on the deposition cycles and heat treatment. The combination of small particle size, high SSA, and enhanced crystallinity after heat treatment at 600 °C contributes to the excellent photocatalytic property of the silica-titania composite aerogel. The higher SSAs compared to those of the reported titania aerogels (aerogels promising candidates as photocatalysts.

  3. Ocean warming-acidification synergism undermines dissolved organic matter assembly.

    Science.gov (United States)

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

    2015-01-01

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

  4. Ocean warming-acidification synergism undermines dissolved organic matter assembly.

    Directory of Open Access Journals (Sweden)

    Chi-Shuo Chen

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

  5. Investigation on Production and Markets of Silica Bricks in China

    Institute of Scientific and Technical Information of China (English)

    ZHANGZhongqi; CHUGuosheng; WANGTiezheng; PANShangxin

    2003-01-01

    The annual output of China's silica brick amounts up to over 300 thousand tons, which accounts for more than 70% of the total oupout of silica bricks in the world. Besides satisfying domestic markets, China's silica bricks have been exported to many countries and retions such as Japan, USA etc. In this paper, the situation of silica bricks production, technology, sales and exporting have been described. Also suggestions on improvement of silica bricks quality and exporting, corporation with foreign partners have been put forward in order to win larger market share both aat home and abroad.

  6. Investigation on Production and Markets of Silica Bricks in China

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhongqi; CHU Guosheng; WANG Tiezheng; PAN Shangxin

    2003-01-01

    The annual output of China' s silica brick amounts up to over 300 thousand tons, which accounts for more than 70% of the total output of silica bricks in the world.Besides satisfying domestic markets, China's silica bricks have been exported to many countries and regions such as Japan, USA etc. In this paper, the situation of silica bricks production, technology, sales and exporting have been described. Also suggestions on improvement of silica bricks quality and exporting, corporation with foreign partners have been put forward in order to win larger market share both at home and abroad.

  7. Extraction of Silica and other related products from Rice Husk

    Directory of Open Access Journals (Sweden)

    Abhishek Mehta,

    2015-08-01

    Full Text Available The main objective of the present work is the synthesis of silica from rice husk and to study its characterization studies. The alkaline method succeeded by acid precipitation is done for the extraction of silica. The optimization of the concentration of sodium hydroxide and the amount of rice husk ash that goes with it for attaining the maximum yield of silica is done. X-ray Diffraction and Fourier Transform Infrared Spectrometry studies are executed for acquiring its characteristic. Activated carbon and silica gel are the intermediate products formed during the synthesis process of silica.

  8. FORMULATION AND EVALUATION OF FAST DISSOLVING FILMS OF ZOLMITRIPTAN

    OpenAIRE

    2012-01-01

    The present study was aimed to formulate and evaluate fast dissolving films of Zolmitriptan using hydroxyl propyl methyl cellulose. 5-HT1B and 5-HT1D antagonist which is an antimigraine. Hydroxyl propyl methyl cellulose is used as film forming agent. Fast dissolving films are meant to be dissolved in saliva and remain in oral cavity until swallowed. Hence taste masking becomes critically important. The films are prepared by solvent evaporation method and characterized by UV, FTIR studies. The...

  9. Method to Estimate the Dissolved Air Content in Hydraulic Fluid

    Science.gov (United States)

    Hauser, Daniel M.

    2011-01-01

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

  10. Study of Dissolved Chlorofluorocarbons in Lake Washington

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

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

  11. DISSOLVED CONCENTRATION LIMITS OF RADIOACTIVE ELEMENTS

    Energy Technology Data Exchange (ETDEWEB)

    P. Bernot

    2005-07-13

    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

  12. [The flux of historiography].

    Science.gov (United States)

    Mazzolini, R G

    2001-01-01

    The author places Grmek's editorial within the flux of the historiographical debate which, since the middle of the 1970s, has concentrated on two major crises due to the end of social science-oriented 'scientific history' and to the 'linguistic turn'. He also argues that Grmek's historiographical work of the 1980s and 1990s was to some extent an alternative to certain observed changes in historical fashion and has achieved greater intelligibility because of its commitment to a rational vision of science and historiography.

  13. The effect of drain blocking on dissolved organic carbon under the peak flow conditions

    Science.gov (United States)

    zhang, zhuoli

    2014-05-01

    There are numerous studies that have shown increasing dissolved organic carbon (DOC) concentration down stream of upland peat catchments (eg. Worrall et al., 2007; Clark et al., 2007; Gibson et al., 200). In the UK, upland peat soils are both an important water source and an important carbon store, therefore, the transportation of DOC from soil to the aquatic system remains a critical part of the impact that upland peat environments have on wider society. The majority of the DOC is delivered from the peat soil during the peak flow events (Clark et al., 2008), however, most of the storm events analysis has been developed for organo-mineral soil rather than for peat soil catchments. Worrall et al., (2007) suggested that drain blocking as a potential method for controlling DOC release from peat soil. An events analysis was conducted on the drain blocking data collected from 2008 to 2010 from Cronkley Fell (UK National grid reference NY 83800 26996). A total of 756 peak flow events were chosen to access the impact of drain blocking on DOC concentration and flux during the events. The data was analysed by the combination of principal components analysis (PCA) and end member mixing analysis (EMMA). The results showed that during the peak flow events, the effects of drain blocking was minimised by the rapid flushing of the event water: the DOC concentration on storm events increased after blocking rather than decreased; DOC flux did decrease after blocking but rather as a result of the increased volume of the event water. Worrall, F., Armstrong, A., Holden, J., 2007. Short term impact of peat drain blocking on water color, dissolved organic carbon concentration and water table depth. Journal of Hydrology 337,315-325 Clark, J.M., Lane, S.N., Chapman, P.J., Adamson, J.K., 2007. Export of dissolved organic carbon from an upland peat during storm events: Implication for flux estimates. Journal of Hydrology 347, 438-447. Aitkenhead, J.A., McDowell, W. H., 2000. Soil C: N ratio

  14. Plasma-deposited hybrid silica membranes with a controlled retention of organic bridges

    Energy Technology Data Exchange (ETDEWEB)

    Ngamou, P.H.T.; Creatore, M. [Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands); Overbeek, J.P.; Kreiter, R.; Van Veen, H.M.; Vente, J.F. [ECN, Energy research Centre of the Netherlands, Petten (Netherlands); Wienk, I.M.; Cuperus, P.F. [SolSep BV, Apeldoorn (Netherlands)

    2013-03-05

    Hybrid organically bridged silica membranes are suitable for energy-efficient molecular separations under harsh industrial conditions. Such membranes can be useful in organic solvent nanofiltration if they can be deposited on flexible, porous and large area supports. Here, we report the proof of concept for applying an expanding thermal plasma to the synthesis of perm-selective hybrid silica films from an organically bridged monomer, 1,2-bis(triethoxysilyl)ethane. This membrane is the first in its class to be produced by plasma enhanced chemical vapor deposition. By tuning the plasma and process parameters, the organic bridging groups could be retained in the separating layer. This way, a defect free film could be made with pervaporation performances of an n-butanol-water mixture comparable with those of conventional ceramic supported membranes made by sol-gel technology (i.e. a water flux of [similar]1.8 kg m'-{sup 2} h{sup -1}, a water concentration in the permeate higher than 98% and a separation factor of >1100). The obtained results show the suitability of expanding thermal plasma as a technology for the deposition of hybrid silica membranes for molecular separations.

  15. Isotopic equilibration between dissolved and suspended particulate lead in the Atlantic Ocean - Evidence from Pb-210 and stable Pb isotopes

    Science.gov (United States)

    Sherrell, Robert M.; Boyle, Edward A.; Hamelin, Bruno

    1992-01-01

    Vertical profiles of, on one hand, the stable Pb isotopic composition, and on the other, the ratio of total Pb to Pb-210 in suspended particles, are noted to closely track contemporaneous depth variations in these ratios for dissolved Pb throughout the upper 2 km of the Sargasso Sea near Bermuda. A simple flux model suggests that the effect of deep ocean scavenging processes on the flux and isotopic composition of Pb sinking on large particles was minor throughout the preanthropogenic, and most of the anthropogenic era: but it has become more important as surface inputs decrease to preleaded gasoline levels, perhaps exceeding the contribution of surface-derived Pb flux in the next decade.

  16. Incorporation of anti-inflammatory agent into mesoporous silica

    Science.gov (United States)

    Rodrigues Braz, Wilson; Lamec Rocha, Natállia; de Faria, Emerson H.; Silva, Márcio L. A. e.; Ciuffi, Katia J.; Tavares, Denise C.; Furtado, Ricardo Andrade; Rocha, Lucas A.; Nassar, Eduardo J.

    2016-09-01

    The unique properties of macroporous, mesoporous, and microporous systems, including their ability to accommodate molecules of different sizes inside their pores and to act as drug delivery systems, have been the object of extensive studies. In this work, mesoporous silica with hexagonal structure was obtained by template synthesis via the sol-gel process. The resulting material was used as support to accommodate the anti-inflammatory agent indomethacin. The alkaline route was used to prepare the mesoporous silica; cetyltrimethylammonium bromide was employed as porogenic agent. The silica particles were functionalized with 3-aminopropyltriethoxysilane alkoxide (APTES) by the sol-gel post-synthesis method. Indomethacin was incorporated into the silica functionalized with APTES and into non-functionalized silica. The resulting systems were characterized by x-ray diffraction (XRD), specific area, infrared spectroscopy, and thermal analyses (TGA). XRD attested to formation of mesoporous silica with hexagonal structure. This structure remained after silica functionalization with APTES and incorporation of indomethacin. Typical infrared spectroscopy vibrations and organic material decomposition during TGA confirmed silica functionalization and drug incorporation. The specific surface area and pore volume of the functionalized material incorporated with indomethacin decreased as compared with the specific surface area and pore volume of the non-functionalized silica containing no drug, suggesting both the functionalizing agent and the drug were present in the silica. Cytotoxicity tests conducted on normal fibroblasts (GM0479A) cells attested that the silica matrix containing indomethacin was less toxic than the free drug.

  17. Comparison of CO2 fluxes estimated using atmospheric and oceanic inversions, and role of fluxes and their interannual variability in simulating atmospheric CO2 concentrations

    Science.gov (United States)

    Patra, P. K.; Mikaloff Fletcher, S. E.; Ishijima, K.; Maksyutov, S.; Nakazawa, T.

    2006-07-01

    We use a time-dependent inverse (TDI) model to estimate regional sources and sinks of atmospheric CO2 from 64 and then 22 regions based on atmospheric CO2 observations at 87 stations. The air-sea fluxes from the 64-region atmospheric-CO2 inversion are compared with fluxes from an analogous ocean inversion that uses ocean interior observations of dissolved inorganic carbon (DIC) and other tracers and an ocean general circulation model (OGCM). We find that, unlike previous atmospheric inversions, our flux estimates in the southern hemisphere are generally in good agreement with the results from the ocean inversion, which gives us added confidence in our flux estimates. In addition, a forward tracer transport model (TTM) is used to simulate the observed CO2 concentrations using (1) estimates of fossil fuel emissions and a priori estimates of the terrestrial and oceanic fluxes of CO2, and (2) two sets of TDI model corrected fluxes. The TTM simulations of TDI model corrected fluxes show improvements in fitting the observed interannual variability in growth rates and seasonal cycles in atmospheric CO2. Our analysis suggests that the use of interannually varying (IAV) meteorology and a larger observational network have helped to capture the regional representation and interannual variabilities in CO2 fluxes realistically.

  18. Review: Agricultural Wastes as a Source of Silica Material

    Directory of Open Access Journals (Sweden)

    Novie Permatasari

    2016-05-01

    Full Text Available Silica is the most abundant components in the earth's crust and is made by way of synthesis for use in the application of technology. Silica are generally found commercially as alkoxysilane compounds (i.e such as tetraethylorthosilicate (TEOS, sodium silicate, and tetramethylorthosilicat. However, these compounds can have a negative impact on health. Thus, further approaches to find the source of silica that is safer, cheaper, and more environmentally friendly is inevitable. However, not all summary journals are thoroughly discussed the silica sources. Further, method of isolation and application of the silica from agricultural waste is limited. This paper reported studied several sources of silica derived from agricultural waste, such as rice husk, rice straw, corn cobs, and bagasse. In addition, this paper discussed also about the method of isolation of silica from agricultural waste, and its application as a catalyst.

  19. Critical heat flux thermodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Collado, F.J. E-mail: fjk@posta.unizar.es

    2002-11-01

    Convective boiling in subcooled water flowing through a heated channel is essential in many engineering applications where high heat flux need to be accommodated, such as in the divertor plates of fusion reactors. There are many available correlations for predicting heat transfer in the individual regimes of the empirical Nukiyama boiling curve, although unfortunately there is no physical fundamentals of such curve. Recently, the author has shown that the classical entropy balance could contain key information about boiling heat transfer. So, it was found that the average thermal gap in the heated channel (the wall temperature minus the average temperature of the coolant fluid) was strongly correlated with the efficiency of a theoretical reversible engine placed in this thermal gap. In this work and from the new proposed correlation, a new expression of the wall temperature in function of the average fluid temperature is derived and successfully checked against experimental data from General Electric. This expression suggests a new and simple definition of the critical heat flux (CHF), a key parameter of the thermal-hydraulic design of fusion reactors. Finally, based on the new definition, the CHF trends are commented.

  20. Coupling river hydrochemical information with catchment properties for multi-scale-analysis of lateral matter fluxes in the Earth system

    Science.gov (United States)

    Hartmann, Jens; Lauerwald, Ronny; Moosdorf, Nils

    2016-04-01

    Over the last decade the number of regional to global scale studies of river chemical fluxes and their steering factors increased rapidly, entailing a growing demand for appropriate databases to calculate mass budgets, to calibrate models, or to test hypotheses [1, 2]. Research applying compilations of hydrochemical data are related to questions targeting different time and spatial scales, as for example the annual to centennial scale. In focus are often the alteration of land-ocean matter fluxes due anthropogenic disturbance, the climate sensitivity of chemical weathering fluxes [3], or nutrient fluxes and their evolution [2, 4]. We present an overview of the GLObal RIver CHemistry database GLORICH, which combines an assemblage of hydrochemical data from varying sources with catchment characteristics of the sampling locations [1]. The information provided include e.g. catchment size, lithology, soil, climate, land cover, net primary production, population density and average slope gradient. The data base comprises 1.27 million samples distributed over 17,000 sampling locations [1]. It will be shown how large assemblages of data are useful to target some major questions about the alteration of land ocean element fluxes due to climate or land use change while coupling hydrochemical data with catchment properties in a homogenized database. An extension by isotopic data will be in the focus of future work [c.f. 5]. Further, applications in climate change studies for understanding feedbacks in the Earth system will be discussed [6]. References: [1] Hartmann, J., Lauerwald, R., & Moosdorf, N. (2014). A brief overview of the GLObal RIver CHemistry Database, GLORICH. Procedia Earth and Planetary Science, 10, 23-27. [2] Hartmann, J., Levy, J., & Kempe, S. (2011). Increasing dissolved silica trends in the Rhine River: an effect of recovery from high P loads?. Limnology, 12(1), 63-73. [3] Hartmann, J., Moosdorf, N., Lauerwald, R., Hinderer, M., & West, A. J. (2014). Global

  1. Numerical modeling of cold magmatic CO2 flux measurements for the exploration of hidden geothermal systems

    Science.gov (United States)

    Peiffer, Loïc.; Wanner, Christoph; Pan, Lehua

    2015-10-01

    The most accepted conceptual model to explain surface degassing of cold magmatic CO2 in volcanic-geothermal systems involves the presence of a gas reservoir. In this study, numerical simulations using the TOUGH2-ECO2N V2.0 package are performed to get quantitative insights into how cold CO2 soil flux measurements are related to reservoir and fluid properties. Although the modeling is based on flux data measured at a specific geothermal site, the Acoculco caldera (Mexico), some general insights have been gained. Both the CO2 fluxes at the surface and the depth at which CO2 exsolves are highly sensitive to the dissolved CO2 content of the deep fluid. If CO2 mainly exsolves above the reservoir within a fracture zone, the surface CO2 fluxes are not sensitive to the reservoir size but depend on the CO2 dissolved content and the rock permeability. For gas exsolution below the top of the reservoir, surface CO2 fluxes also depend on the gas saturation of the deep fluid as well as the reservoir size. The absence of thermal anomalies at the surface is mainly a consequence of the low enthalpy of CO2. The heat carried by CO2 is efficiently cooled down by heat conduction and to a certain extent by isoenthalpic volume expansion depending on the temperature gradient. Thermal anomalies occur at higher CO2 fluxes (>37,000 g m-2 d-1) when the heat flux of the rising CO2 is not balanced anymore. Finally, specific results are obtained for the Acoculco area (reservoir depth, CO2 dissolved content, and gas saturation state).

  2. The impacts of '05.6' extreme flood event on riverine carbon fluxes in Xijiang River

    Institute of Scientific and Technical Information of China (English)

    SUN HuiGuo; HAN JingTai; ZHANG ShuRong; LU XiXi

    2007-01-01

    An extreme flood event with a frequency of nearly 200 year occurred in June of 2005 in the Xijiang River,the main trunk stream of the Zhujiang River. Samples were systematically collected during the flood event, and water quality parameters, including total suspended sediment (TSS), dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), and particulate organic carbon (POC) were analyzed,and riverine carbon concentrations associated with its changing pattern through the flood process were discussed. These parameters reflect the changes in basin surface flow and subsurface flow during the flood. This flood event influenced annual flux estimations of POC, DOC, and DIC to great extents.Based on carbon flux estimations for the year 2005 and the flood event (June 21-28) in the Xijiang River, it was found that DIC, DOC, and POC fluxes during '05.6' flood event are 1.52x106 g.km-2.a-1,0.24x106 g.km-2.a-1, and 0.54x106 g.km-2.a-1, and account for 14.87%, 24.75% and 44.89% of the annual fluxes in 2005, respectively. The results suggested that carbon exports during extreme flood events had great contributions to the total carbon fluxes and composition of various carbon components, being important for accurate estimates of annual carbon fluxes in rivers with frequent floods.

  3. Adsorption behavior of Am with gamma irradiated Thiacalix[4]arene impregnated silica adsorbent

    Energy Technology Data Exchange (ETDEWEB)

    Kikuchi, Takahiro [Institute of Research and Innovation (IRI), 1201 Takada, Kashiwa, Chiba 277-0861 (Japan)]. E-mail: tkikuchi@iri.or.jp; Suzuki, Kazunori [Institute of Research and Innovation (IRI), 1201 Takada, Kashiwa, Chiba 277-0861 (Japan)

    2006-02-09

    Thiacalix[4]arene impregnated silica adsorbent which is called CAPS-SO{sub 2}-adsorbent in this paper shows the excellent separative performance of trivalent actinoids, such as Am from the high-level radioactive liquid waste (HLLW) in weak-acid solution. The chemical stability of the adsorbent was investigated under strong irradiation conditions. The amount of dissolved CAPS-SO{sub 2} was only 1% by gamma-ray irradiation at a total dose of 1 MGy. The value of distribution coefficient of Am (Kd{sub Am}) at pH 4 by the adsorbent was constant even the high irradiation dose. Moreover, the separation factor of Am to lanthanoids is kept a high value. It was also found that the value of Kd{sub Am} by the irradiated CAPS-SO{sub 2}-adsorbent increases at pH 2.

  4. Soil Incorporation of Silica-Rich Rice Husk Decreases Inorganic Arsenic in Rice Grain.

    Science.gov (United States)

    Seyfferth, Angelia L; Morris, Andrew H; Gill, Rattandeep; Kearns, Kelli A; Mann, Jessica N; Paukett, Michelle; Leskanic, Corey

    2016-05-18

    Arsenic decreases rice yield, and inorganic grain As threatens human health; thus, strategies to decrease rice As are critically needed. Increased plant-available silica (Si) can decrease rice As, yet the source of Si matters. Rice husk, an underutilized and Si-rich byproduct of rice production that contains less labile C and an order of magnitude less As than rice straw, may be an economically viable Si resource to decrease rice As, yet the impact of rice husk incorporation on As in the rice-soil nexus has not been reported. This proof-of-concept study shows that rice husk incorporation to soil (1% w/w) decreases inorganic grain As by 25-50% without negatively affecting grain Cd, yield, or dissolved CH4 levels. Rice husk is a critical yet perhaps overlooked resource to improve soil quality through enhanced nutrient availability and attenuate human health risks through consumption of As-laden grain.

  5. Small scale variability of transport and composition of dissolved organic matter in the subsoil

    Science.gov (United States)

    Leinemann, Timo; Kalbitz, Karsten; Mikutta, Robert; Guggenberger, Georg

    2016-04-01

    Dissolved organic matter (DOM) is the most mobile fraction of carbon in the soil and connects the carbon-rich topsoil with the subsoil where translocated OM may get stabilized. The water flux in soil is highly heterogeneous, both temporarily and spatially. We, therefore, hypothesize that at high flow velocities, DOM can bypass possible mineral binding sites and microorganisms, thus leading to less degraded DOM under high flow velocities. To address this question, we investigated water and DOM fluxes in situ using segmented suction plates (4 x 4 segments on 24 x 24 cm) installed into three soil observatories at three depths (10 cm, 50 cm, and 150 cm) in a Podzolic Cambisol under Beech (Fagus sylvatica) near Hannover, Germany. To follow the transport of carbon from the litter layer through the soil, an in situ 13C-labelling experiment has been conducted in January 2015. Concentration of dissolved organic carbon (DOC) and DOM composition was analyzed using high temperature combustion and photometric methods. The amount of transported DOC decreased by ca. 80% from 10 to 50 cm depth and by 40% from 50 to 150 cm depth. Different flow patterns existed at the centimeter scale, which were stable over time for individual suction plate segments. The specific UV280 nm absorbance of DOM decreased with increasing soil depth. This indicates a selective loss of aromatic compounds. The influence of different flow regimes on the DOM quality became apparent in the subsoil samples (>50 cm depth) showing a correlation of increasing UV280 nm absorbance with increasing water flux. Together with juvenile DO14C up to 150 cm depth this can be an indication for the importance of preferential flow on carbon transport to subsoil.

  6. Kinetics of CO(2) fluxes outgassing from champagne glasses in tasting conditions: the role of temperature.

    Science.gov (United States)

    Liger-Belair, Gérard; Villaume, Sandra; Cilindre, Clara; Jeandet, Philippe

    2009-03-11

    Measurements of CO(2) fluxes outgassing from a flute poured with a standard Champagne wine initially holding about 11 g L(-1) of dissolved CO(2) were presented, in tasting conditions, all along the first 10 min following the pouring process. Experiments were performed at three sets of temperature, namely, 4 degrees C, 12 degrees C, and 20 degrees C, respectively. It was demonstrated that the lower the champagne temperature, the lower CO(2) volume fluxes outgassing from the flute. Therefore, the lower the champagne temperature, the lower its progressive loss of dissolved CO(2) concentration with time, which constitutes the first analytical proof that low champagne temperatures prolong the drink's chill and helps retains its effervescence. A correlation was also proposed between CO(2) volume fluxes outgassing from the flute poured with champagne and its continuously decreasing dissolved CO(2) concentration. Finally, the contribution of effervescence to the global kinetics of CO(2) release was discussed and modeled by the use of results developed over recent years. The temperature dependence of the champagne viscosity was found to play a major role in the kinetics of CO(2) outgassing from a flute. On the basis of this bubbling model, the theoretical influence of champagne temperature on CO(2) volume fluxes outgassing from a flute was discussed and found to be in quite good accordance with our experimental results.

  7. Silica nanoparticles containing 159-Gadolinium as potential system for cancer treatment

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Andre Felipe de; Ferreira, Tiago Hilario; Sousa, Edesia Martins Barros de, E-mail: andrefelipe.oliveira88@gmail.com [Centro de Desenvolvimento da Tecnologia Nuclear (SENAN/CDTN/CNEN-MG), Belo Horizonte, MG (Brazil). Servico de Nanotecnologia; Lacerda, Marco Aurelio [Centro de Desenvolvimento da Tecnologia Nuclear (SERAS/CDTN/CNEN-MG), Belo Horizonte, MG (Brazil). Servico das Radiacoes Aplicadas a Saude

    2013-07-01

    Ordered silica nanoparticles are compounds highly organized which have very interesting textural characteristics, such as high thermal stability, well defined pore size, narrow size distribution and high area surface. Among the various types of nano materials ordered, the SBA-16 have a meso structure that can be considered very interesting due to the fact of the arrangement of mesoporous (tri dimensional as a cage) and spherical morphology, which make it in a promising material for a range of bioapplications such as incorporation of drugs and radioisotopes. In this study Gadodiamide® (Omniscan-General Electric Healthcare Company), a frequently non-ionic gadolinium complex contrasting used in MRI's was incorporated in the silica matrix SBA-16 as a carrier. From this gadolinium it is possible to obtain the isotope {sup 159}Gd by neutron irradiation, wherein the isotope {sup 158}Gd captures a neutron and becomes {sup 159}Gd [{sup 15}'8Gd(n,c){sup 1}'5{sup 9}Gd]. The {sup 159}Gd is a beta (endpoint energy of 970.6 keV) and gamma (main energy: 363.54 keV) emitter with a half-life of 18.59 hours. These characteristics are similar to that of other isotopes already used in nuclear medicine such as {sup 90}Y. In this work, the {sup 158}Gd incorporated in the Gd-silica was activated by the neutron flux generated by the cyclotron located in the Centro de Desenvolvimento da Tecnologia Nuclear (CDTN) during the production of the {sup 18}FDG. Atomic emission spectroscopy (ICP-AES) and infrared spectroscopy (FTIR) were used to confirm the presence of the gadolinium complex in the silica matrix. The antitumor activity of the complex after the irradiation was evaluated through cytotoxicity assay with T98 cell lines derived from a human glioblastoma multiform tumor. (author)

  8. Form control in atmospheric pressure plasma processing of ground fused silica

    Science.gov (United States)

    Li, Duo; Wang, Bo; Xin, Qiang; Jin, Huiliang; Wang, Jun; Dong, Wenxia

    2014-08-01

    Atmospheric Pressure Plasma Processing (APPP) using inductively coupled plasma has demonstrated that it can achieve comparable removal rate on the optical surface of fused silica under the atmosphere pressure and has the advantage of inducing no sub-surface damage for its non-contact and chemical etching mechanism. APPP technology is a cost effective way, compared with traditional mechanical polishing, magnetorheological finishing and ion beam figuring. Thus, due to these advantages, this technology is being tested to fabricate large aperture optics of fused silica to help shorten the polishing time in optics fabrication chain. Now our group proposes to use inductively coupled plasma processing technology to fabricate ground surface of fused silica directly after the grinding stage. In this paper, form control method and several processing parameters are investigated to evaluate the removal efficiency and the surface quality, including the robustness of removal function, velocity control mode and tool path strategy. However, because of the high heat flux of inductively coupled plasma, the removal depth with time can be non-linear and the ground surface evolvement will be affected. The heat polishing phenomenon is founded. The value of surface roughness is reduced greatly, which is very helpful to reduce the time of follow-up mechanical polishing. Finally, conformal and deterministic polishing experiments are analyzed and discussed. The form error is less 3%, before and after the APPP, when 10μm depth of uniform removal is achieved on a 60×60mm ground fused silica. Also, a basin feature is fabricated to demonstrate the figuring capability and stability. Thus, APPP is a promising technology in processing the large aperture optics.

  9. Permanent magnet flux-biased magnetic actuator with flux feedback

    Science.gov (United States)

    Groom, Nelson J. (Inventor)

    1991-01-01

    The invention is a permanent magnet flux-biased magnetic actuator with flux feedback for adjustably suspending an element on a single axis. The magnetic actuator includes a pair of opposing electromagnets and provides bi-directional forces along the single axis to the suspended element. Permanent magnets in flux feedback loops from the opposing electromagnets establish a reference permanent magnet flux-bias to linearize the force characteristics of the electromagnets to extend the linear range of the actuator without the need for continuous bias currents in the electromagnets.

  10. Downward export of respiratory carbon and dissolved inorganic nitrogen by diel-migrant mesozooplankton at the JGOFS Bermuda time-series station

    Science.gov (United States)

    Dam, Hans G.; Roman, Michael R.; Youngbluth, Marsh J.

    1995-07-01

    Published calculations suggest that downward fluxes of respiratory carbon (RC) and dissolved inorganic nitrogen (DIN) associated with diel-migrant zooplankton are significant forms of export production. In this study, we examined variability in downward fluxes of RC and DIN due to diel-migrant mesozooplankton (200-2000 μm) on seven occasions between 25 March and 8 April 1990 at the JGOFS (Joint Global Ocean Flux Study) station off Bermuda. Downward fluxes due to migrators crossing 150 m ranged from 6 to 41 mgC m -2 day -1 (RC) and 2 to 5 mgN m -2 day -1 (DIN). In comparison to gravitational fluxes of POC and PON measured with particle traps at 150m during the same period, mesozooplankton RC flux was 18-70% of POCflux and mesozooplankton DIN flux was 17-82% of PON flux. If the RC and DIN fluxes due to migrators are considered in calculations of export production, the percentage of the production exported below 150 m over the study period would increase by an average of 25% for carbon and 21% for nitrogen. These results support the contention that metabolic activities of diel-migrant zooplankton should be included in calculations of export of carbon and nitrogen out of the mixed layer.

  11. Braneworld Flux Inflation

    CERN Document Server

    Kanno, S; Wands, D; Kanno, Sugumi; Soda, Jiro; Wands, David

    2005-01-01

    We propose a geometrical model of brane inflation where inflation is driven by the flux generated by opposing brane charges and terminated by the collision of the branes, with charge annihilation. We assume the collision process is completely inelastic and the kinetic energy is transformed into the thermal energy after collision. Thereafter the two branes coalesce together and behave as a single brane universe with zero effective cosmological constant. In the Einstein frame, the 4-dimensional effective theory changes abruptly at the collision point. Therefore, our inflationary model is necessarily 5-dimensional in nature. As the collision process has no singularity in 5-dimensional gravity, we can follow the evolution of fluctuations during the whole history of the universe. It turns out that the radion field fluctuations have a steeply tilted, red spectrum, while the primordial gravitational waves have a flat spectrum. Instead, primordial density perturbations could be generated by a curvaton mechanism.

  12. Zonal distribution of dissolved aluminium in the Mediterranean Sea

    NARCIS (Netherlands)

    Rolison, J. M.; Middag, R.; Stirling, C. H.; Rijkenberg, M. J. A.; de Baar, H. J. W.

    2015-01-01

    Dissolved aluminium (Al) is an important tracer of atmospheric dust input to the oceans. The GEOTRACES expedition to the highly dust impacted Mediterranean Sea afforded the opportunity to study the distribution of dissolved Al in the Mediterranean Sea in detail. Interestingly, the elevated concentra

  13. The dependence on temperature and salinity of dissolved

    NARCIS (Netherlands)

    Bakker, Dorothee C.E.; Baar, Hein J.W. de; Jong, Edwin de

    1999-01-01

    Recurring latitudinal patterns of the dissolved inorganic carbon (DIC) content and the fugacity of CO2 (fCO2) were observed in East Atlantic surface waters with strong gradients at hydrographic fronts. The dissolved inorganic carbon chemistry clearly displayed the effects of oceanic circulation and

  14. Explorations of soil microbial processes driven by dissolved organic carbon

    NARCIS (Netherlands)

    Straathof, A.L.

    2015-01-01

    Explorations of soil microbial processes driven by dissolved organic carbon Angela L. Straathof June 17, 2015, Wageningen UR ISBN 978-94-6257-327-7 Abstract Dissolved organic carbon (DOC) is a complex, heterogeneous mixture of C compounds which, as

  15. Optimal fluxes and Reynolds stresses

    CERN Document Server

    Jimenez, Javier

    2016-01-01

    It is remarked that fluxes in conservation laws, such as the Reynolds stresses in the momentum equation of turbulent shear flows, or the spectral energy flux in isotropic turbulence, are only defined up to an arbitrary solenoidal field. While this is not usually significant for long-time averages, it becomes important when fluxes are modelled locally in large-eddy simulations, or in the analysis of intermittency and cascades. As an example, a numerical procedure is introduced to compute fluxes in scalar conservation equations in such a way that their total integrated magnitude is minimised. The result is an irrotational vector field that derives from a potential, thus minimising sterile flux `circuits'. The algorithm is generalised to tensor fluxes and applied to the transfer of momentum in a turbulent channel. The resulting instantaneous Reynolds stresses are compared with their traditional expressions, and found to be substantially different.

  16. Hybrid silica-PVA nanofibers via sol-gel electrospinning.

    Science.gov (United States)

    Pirzada, Tahira; Arvidson, Sara A; Saquing, Carl D; Shah, S Sakhawat; Khan, Saad A

    2012-04-03

    We report on the synthesis of poly(vinyl alcohol) (PVA)-silica hybrid nanofibers via sol-gel electrospinning. Silica is synthesized through acid catalysis of a silica precursor (tetraethyl orthosilicate (TEOS) in ethanol-water), and fibers are obtained by electrospinning a mixture of the silica precursor solution and aqueous PVA. A systematic investigation on how the amount of TEOS, the silica-PVA ratio, the aging time of the silica precursor mixture, and the solution rheology influence the fiber morphology is undertaken and reveals a composition window in which defect-free hybrid nanofibers with diameters as small as 150 nm are obtained. When soaked overnight in water, the hybrid fibers remain intact, essentially maintaining their morphology, even though PVA is soluble in water. We believe that mixing of the silica precursor and PVA in solution initiates the participation of the silica precursor in cross-linking of PVA so that its -OH group becomes unavailable for hydrogen bonding with water. FTIR analysis of the hybrids confirms the disappearance of the -OH peak typically shown by PVA, while formation of a bond between PVA and silica is indicated by the Si-O-C peak in the spectra of all the hybrids. The ability to form cross-linked nanofibers of PVA using thermally stable and relatively inert silica could broaden the scope of use of these materials in various technologies.

  17. Carbon nanomaterials in silica aerogel matrices

    Energy Technology Data Exchange (ETDEWEB)

    Hamilton, Christopher E [Los Alamos National Laboratory; Chavez, Manuel E [Los Alamos National Laboratory; Duque, Juan G [Los Alamos National Laboratory; Gupta, Gautam [Los Alamos National Laboratory; Doorn, Stephen K [Los Alamos National Laboratory; Dattelbaum, Andrew M [Los Alamos National Laboratory; Obrey, Kimberly A D [Los Alamos National Laboratory

    2010-01-01

    Silica aerogels are ultra low-density, high surface area materials that are extremely good thermal insulators and have numerous technical applications. However, their mechanical properties are not ideal, as they are brittle and prone to shattering. Conversely, single-walled carbon nanotubes (SWCNTs) and graphene-based materials, such as graphene oxide, have extremely high tensile strength and possess novel electronic properties. By introducing SWCNTs or graphene-based materials into aerogel matrices, it is possible to produce composites with the desirable properties of both constituents. We have successfully dispersed SWCNTs and graphene-based materials into silica gels. Subsequent supercritical drying results in monolithic low-density composites having improved mechanical properties. These nanocomposite aerogels have great potential for use in a wide range of applications.

  18. Multipod-like silica/polystyrene clusters

    Science.gov (United States)

    Désert, Anthony; Morele, Jérémy; Taveau, Jean-Christophe; Lambert, Olivier; Lansalot, Muriel; Bourgeat-Lami, Elodie; Thill, Antoine; Spalla, Olivier; Belloni, Luc; Ravaine, Serge; Duguet, Etienne

    2016-03-01

    Multipod-like clusters composed of a silica core and PS satellites are prepared according to a seeded-growth emulsion polymerization of styrene in the presence of size-monodisperse silica particles previously surface-modified with methacryloxymethyltriethoxysilane. Tuning the diameter and concentration of the silica seeds affords homogeneous batches of tetrapods, hexapods, octopods, nonapods and dodecapods with morphology yields as high as 80%. Three-dimensional reconstructions by cryo-electron tomography are presented on large fields for the first time to show the high symmetry and regularity of the clusters demonstrating the good control of the synthesis process. These synthesis experiments are visited again digitally, in order to successfully refine an original simulation model and better understand the correlation between the history of the cluster growth and the final composition of the cluster mixture. Finally, using the model as a predictive tool and varying the extra experimental conditions, e.g. the composition of the surfactant mixture and the styrene concentration, result in trapping other cluster morphologies, such as tripods.Multipod-like clusters composed of a silica core and PS satellites are prepared according to a seeded-growth emulsion polymerization of styrene in the presence of size-monodisperse silica particles previously surface-modified with methacryloxymethyltriethoxysilane. Tuning the diameter and concentration of the silica seeds affords homogeneous batches of tetrapods, hexapods, octopods, nonapods and dodecapods with morphology yields as high as 80%. Three-dimensional reconstructions by cryo-electron tomography are presented on large fields for the first time to show the high symmetry and regularity of the clusters demonstrating the good control of the synthesis process. These synthesis experiments are visited again digitally, in order to successfully refine an original simulation model and better understand the correlation between the

  19. Silica containing highly porous alumina ceramic

    Science.gov (United States)

    Svinka, R.; Svinka, V.; Zake, I.

    2011-04-01

    Porous alumina ceramic were produced by slip casting of aqueous alumina slurry with added small amount of metallic aluminium powder. Pores form in result of chemical reaction of aluminum with water by hydrogen gas evolution reaction and solidification of suspension. Porosity of such materials sintered at a temperature of 1600 - 1750°C varies from 60 to 90%. Pore size distribution and mechanical strength of these materials depend largely on the grain size of used raw materials. The major part of pores in the materials produced without additive of silica are larger than 10 ±m, but with 5 - 10 wt.% additive of silica in the raw mix pore size decreases considerably. The sintering shrinkage decreases to 2.5%. Coefficient of thermal expansion equally decreases from 8.9-10-6 K-1 to 7.1 10-6 K-1 and classification temperature increases to 1600°C, while deformation at high temperature decreases considerably.

  20. Influence of Nano Silica on Alkyd Films

    DEFF Research Database (Denmark)

    Nikolic, Miroslav

    . The present work centers on the reinforcement of alkyd binders emulsified in water and used in exterior wood coatings with nano silica. Raman spectroscopy was used throughout the study to maintain the reproducibility of results as it was found that colloidal nano silica can increase or decrease the speed...... the interactions with the alkyd polymer while keeping the nano filler stable in the water phase did not show further improvements of mechanical properties. The best results in respect to mechanical properties, as measured under static and dynamic loading, were obtained with the use of hexamethyldisilazane treated...... of premature cracking. In this study we have shown that increased stiffness in the first stage of coating lifetime is just one of the parameters and that behavior during the aging needs to be taken into account before drawing conclusions....