Search results for " carbon dioxide"

showing 10 items of 200 documents

Seagrass ecosystem response to long-term high CO2 in a Mediterranean volcanic vent

2014

We examined the long-term effect of naturally acidified water on a Cymodocea nodosa meadow growing at a shallow volcanic CO2 vent in Vulcano Island (Italy). Seagrass and adjacent unvegetated habitats growing at a low pH station (pH = 7.65 ± 0.02) were compared with corresponding habitats at a control station (pH = 8.01 ± 0.01). Density and biomass showed a clear decreasing trend at the low pH station and the below- to above-ground biomass ratio was more than 10 times lower compared to the control. C content and delta 13C of leaves and epiphytes were significantly lower at the low pH station. Photosynthetic activity of C. nodosa was stimulated by low pH as seen by the significant increase in…

Ocean Acidification International Coordination Centre (OA-ICC)TemperateSalinityChlorophyll ainorganicAlkalinityLight saturation point standard errorPhotosynthetic quantum efficiencyMediterranean Sea Acidification in a Changing Climate MedSeATemperature waterCarbon inorganic dissolvedCalculated using seacarb after Nisumaa et al 2010IrradianceRespiration rate carbonAragonite saturation stateBiomassAlkalinity totalIrradiance standard errortotalCO2 ventCymodocea nodosapHRespirationEpiphytes loadMaximum photochemical quantum yield of photosystem II standard errorNet community production of carbonTemperaturePartial pressure of carbon dioxide (water) at sea surface temperature (wet air) standard errordissolvedRespiration rate carbon standard errorCarbonate ionMaximum photochemical quantum yield of photosystem IIPartial pressure of carbon dioxide (water) at sea surface temperature (wet air)Net community production of carbon standard errorIlluminance standard errorSoft bottom communitystandard errorCarbon inorganic dissolved standard errorRespiration rateElectron transport rate standard errorEarth System Researchδ13CPhotosynthetic quantum efficiency standard errorField observationChlorophyll a standard errorGross primary production of carbonBiomass standard errorCalcium carbonatePotentiometric titrationCalcite saturation stateShoot densityPotentiometricwaterIlluminanceOxygen standard errorBenthosAlkalinity total standard errorMediterranean Sea Acidification in a Changing Climate (MedSeA)Electron transport rateLight saturation pointOcean Acidification International Coordination Centre OA ICCMediterranean SeaGross primary production of carbon standard errorBicarbonate ionSoft-bottom communityδ13C standard errorTemperature water standard errorCalculated using seacarb after Nisumaa et al. (2010)Primary production PhotosynthesisSpeciespH standard errorCarbonate system computation flagloadPrimary production/PhotosynthesisFugacity of carbon dioxide (water) at sea surface temperature (wet air)CarbonBiomass/Abundance/Elemental compositionTreatmentEpiphytes load standard errorOxygenPartial pressure of carbon dioxide water at sea surface temperature wet airEpiphytes loadCarbon dioxideCarbon standard errorEntire communityFugacity of carbon dioxide water at sea surface temperature wet airGroupBiomass Abundance Elemental compositionCoast and continental shelfEpiphytesShoot density standard errorCalcium carbonate standard error
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Seawater carbonate chemistry and coralline algal diversity

2021

Calcified coralline algae are ecologically important in rocky habitats in the marine photic zone worldwide and there is growing concern that ocean acidification will severely impact them. Laboratory studies of these algae in simulated ocean acidification conditions have revealed wide variability in growth, photosynthesis and calcification responses, making it difficult to assess their future biodiversity, abundance and contribution to ecosystem function. Here, we apply molecular systematic tools to assess the impact of natural gradients in seawater carbonate chemistry on the biodiversity of coralline algae in the Mediterranean and the NW Pacific, link this to their evolutionary history and …

Ocean Acidification International Coordination Centre (OA-ICC)TemperateSalinityCommunity composition and diversityBicarbonate ion standard deviationinorganicAlkalinity total standard deviationAlkalinityExperimentTemperature waterCarbon inorganic dissolvedCalculated using seacarb after Nisumaa et al 2010Aragonite saturation stateNorth PacificMarine habitatAlkalinity totaltotalCO2 ventpHTemperaturedissolvedCarbonate ionPartial pressure of carbon dioxide (water) at sea surface temperature (wet air)Calcium carbonate standard deviationstandard errorEarth System Researchstandard deviationField observationCalcium carbonateCoverageCalcite saturation stateLocationwaterPartial pressure of carbon dioxideSiteRocky-shore communityCalcium carbonate massAragonite saturation state standard deviationBenthosSalinity standard deviationOcean Acidification International Coordination Centre OA ICCMediterranean SeaCarbon inorganic dissolved standard deviationCalcite saturation state standard deviationTypeBicarbonate ionCalculated using seacarb after Nisumaa et al. (2010)Coverage standard errorfungiEvent labelPartial pressure of carbon dioxide standard deviationCarbonate system computation flagpH standard deviationCarbonate ion standard deviationFugacity of carbon dioxide (water) at sea surface temperature (wet air)CarbonPartial pressure of carbon dioxide water at sea surface temperature wet airCarbon dioxideRocky shore communityEntire communityFugacity of carbon dioxide water at sea surface temperature wet airCoast and continental shelfSpecies richness
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Decline in Coccolithophore Diversity and Impact on Coccolith Morphogenesis Along a Natural CO2 Gradient

2014

A natural pH gradient caused by marine CO2 seeps off Vulcano Island (Italy) was used to assess the effects of ocean acidification on coccolithophores, which are abundant planktonic unicellular calcifiers. Such seeps are used as natural laboratories to study the effects of ocean acidification on marine ecosystems, since they cause long-term changes in seawater carbonate chemistry and pH, exposing the organisms to elevated CO2 concentrations and therefore mimicking future scenarios. Previous work at CO2 seeps has focused exclusively on benthic organisms. Here we show progressive depletion of 27 coccolithophore species, in terms of cell concentrations and diversity, along a calcite saturation …

Ocean Acidification International Coordination Centre (OA-ICC)TemperateSalinityCommunity composition and diversityinorganicAlkalinityCoccospheres malformedMediterranean Sea Acidification in a Changing Climate MedSeATemperature waterCarbon inorganic dissolvedCalculated using seacarb after Nisumaa et al 2010Aragonite saturation stateAlkalinity totaltotalCO2 ventpHPelagosTemperaturedissolvedCarbonate ionPartial pressure of carbon dioxide (water) at sea surface temperature (wet air)Earth System ResearchmalformedField observationPotentiometric titrationCalcite saturation stateCoccospheresPotentiometricwaterGrowth MorphologyMediterranean Sea Acidification in a Changing Climate (MedSeA)Ocean Acidification International Coordination Centre OA ICCMediterranean SeaBicarbonate ionCalculated using seacarb after Nisumaa et al. (2010)Calculated using CO2SYSfungiCarbonate system computation flagCoccospheres corrodedFugacity of carbon dioxide (water) at sea surface temperature (wet air)CarbonBiomass/Abundance/Elemental compositionPartial pressure of carbon dioxide water at sea surface temperature wet airSample IDCarbon dioxidecorrodedEntire communityGrowth/MorphologyPhytoplanktonFugacity of carbon dioxide water at sea surface temperature wet airBiomass Abundance Elemental compositionCoast and continental shelfNumber of species
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Shallow water marine sediment bacterial community shifts along a natural CO2 gradient in the Mediterranean Sea Off vulcano, Italy

2014

The effects of increasing atmospheric CO(2) on ocean ecosystems are a major environmental concern, as rapid shoaling of the carbonate saturation horizon is exposing vast areas of marine sediments to corrosive waters worldwide. Natural CO(2) gradients off Vulcano, Italy, have revealed profound ecosystem changes along rocky shore habitats as carbonate saturation levels decrease, but no investigations have yet been made of the sedimentary habitat. Here, we sampled the upper 2 cm of volcanic sand in three zones, ambient (median pCO(2) 419 µatm, minimum Omega (arag) 3.77), moderately CO(2)-enriched (median pCO(2) 592 µatm, minimum Omega (arag) 2.96), and highly CO(2)-enriched (median pCO(2) 1611…

Ocean Acidification International Coordination Centre (OA-ICC)TemperateSalinityPotentiometric titrationCalcite saturation stateCommunity composition and diversityPotentiometricinorganicwaterAlkalinitySiteFigureBenthosTemperature waterCarbon inorganic dissolvedAbundanceCalculated using seacarb after Nisumaa et al 2010Ocean Acidification International Coordination Centre OA ICCMediterranean SeaBicarbonate ionAragonite saturation stateSoft-bottom communityAlkalinity totalLONGITUDEtotalCalculated using seacarb after Nisumaa et al. (2010)CO2 ventSpeciesShannon Diversity IndexpHCalculated using CO2SYSTemperatureCarbonate system computation flagdissolvedFugacity of carbon dioxide (water) at sea surface temperature (wet air)Carbonate ionCarbonPartial pressure of carbon dioxide (water) at sea surface temperature (wet air)Partial pressure of carbon dioxide water at sea surface temperature wet airCarbon dioxideSoft bottom communityEntire communityEarth System ResearchLATITUDEFugacity of carbon dioxide water at sea surface temperature wet airGroupCoast and continental shelfField observationClass
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Homogeneous Metal-Based Catalysis in Supercritical Carbon Dioxide as Reaction Medium

2016

Above 31.1 degrees C and 73.8 bar, carbon dioxide reaches the supercritical state, being transformed into a fluid (scCO(2)) that has attracted interest in the last few decades as reaction medium for several transition-metal-catalyzed organic transformations. The main feature of this fluid rests on its capability to dissolve large amounts of other gases such as hydrogen, carbon monoxide, ethylene, or even methane and light alkanes. In this manner, very high concentrations of these reactants are available for catalysis. In this contribution a review of the main achievements of the use of transition-metal complexes as catalysts in scCO(2) is presented.

Olefin metathesisInorganic chemistryHomogeneous catalysis010402 general chemistry01 natural sciencesC-C bond formationCatalysisMethaneCatalysischemistry.chemical_compoundSupercritical carbon dioxideOxidationC-H activationCycloadditionElectrochemical reduction of carbon dioxideSupercritical carbon dioxide010405 organic chemistryChemistryGeneral ChemistryHomogeneous catalysisSupercritical fluid0104 chemical sciencesCarbon dioxideHydroformylationHydrogenationCarbon monoxide
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Preparation of pH sensitive poly(vinilydenefluoride) porous membranes by grafting of acrylic acid assisted by supercritical carbon dioxide

2012

Free radical grafting of acrylic acid (AA) on poly(vinilydenefluoride) (PVDF) porous membranes was studied at 65°C using supercritical carbon dioxide (scCO 2) as a solvent and delivery agent. The process was initiated by the thermal decomposition of benzoylperoxide (BPO). Spectroscopic analyses confirmed the presence of poly(AA) chains linked to treated membranes. The mass fraction of grafted AA increased with grafting time and BPO concentration while it decreased when the density of the fluid phase was enhanced. A not-monotonic trend was obtained when the effect of the initial AA concentration was studied. The grafting process was accompanied by a reduction of the crystallinity of the PVDF…

PH-dependentGrafting proceGeneral Chemical EngineeringRadical polymerizationpH-sensitive polymersMass fractionPoly(vinylidene fluoride)Free radical graftingGrafting degreeCarboxylic acidRelease experimentAcrylic acidSupercritical fluid extraction Grafting (chemical)chemistry.chemical_compoundCrystallinityPVDF membraneFree radicalPolymer chemistrypH sensorPhysical and Theoretical ChemistryFluid-phasepH sensitiveAcrylic acidCrystallinitieDecompositionSupercritical carbon dioxideFree radical polymerizationChemistrySupercritical carbon dioxides Carbon dioxideSettore ING-IND/27 - Chimica Industriale E TecnologicaCondensed Matter PhysicsGraftingSolventMembraneSpectroscopic analysiPorous membraneNuclear chemistryThe Journal of Supercritical Fluids
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Order-Order Phase Transitions Induced by Supercritical Carbon Dioxide in Triblock Copolymer Thin Films

2019

We study the influence of supercritical carbon dioxide (scCO2) on the phase behavior of a cylinder-forming polystyrene-block-polybutadiene-b-polystyrenetriblock copolymer thin film. Solvent annealing with scCO2 can produce patterns with long-range order but these structures become unstable for thin films with small thicknesses. These results are in good agreement with self-consistent mean field calculations, which indicate that a drying transition occurs for thicknesses below the radius of gyration of the molecule.After decompression and solvent extraction, the initially swollen polymer nanostructure suffers a strong reduction in the average domain spacing, which has a deleterious effect on…

Phase transitionMaterials scienceSupercritical carbon dioxidePolymers and PlasticsOrganic ChemistryAnalytical chemistry02 engineering and technologyINGENIERÍAS Y TECNOLOGÍAS010402 general chemistry021001 nanoscience & nanotechnologyORDER-ORDER PHASE TRANSITIONS01 natural sciences0104 chemical sciencesInorganic ChemistrySUPERCRITICAL CARBON DIOXIDEIngeniería de los MaterialesTHIN FILMSMaterials ChemistryCopolymerThin film0210 nano-technologySBS
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ScCO2 as polymerization medium for high value polymers: two recent cases

2007

In recent years the use of supercritical carbon dioxide (scCO2) in polymer processing and polymerization reactions has merged as a “green” alternative to replace both organic solvents, environmentally hazardous (VOCs), and water, which use involves the production of large amount of waste streams. ScCO2 is non-toxic, inexpensive, and often exhibits high solubility in polymer matrixes. Moreover, it causes polymer plasticization, thus favoring the diffusion of low MW species (monomers, initiators or additives) in the polymer phase. In this work, the use of scCO2 as polymerization medium for two different special polymers is discussed. Fluorinated copolymers mainly find application in environme…

Polymerization Carbon dioxide Heterogeneous
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Gamma radiation induced polymerization of vinyl monomers in dense CO2

2002

Abstract The dispersion polymerization of methyl methacrylate in dense carbon dioxide, initiated by γ-rays, utilizing different polysiloxanes as polymeric stabilizers, was investigated. The progress of the reaction, as a function of the irradiation dose, was also studied and the occurrence of a gel effect has been detected. For comparison, the dispersion polymerization has been carried out in supercritical conditions ( T =65°C and 38 MPa) in the presence of 2,2′-azobis(isobutyronitrile) (AIBN) as initiator. High molecular weight polymer (M w > 1000 kg/mol) with narrow molecular weight distribution has been obtained both with γ-rays and AIBN. The electron scanning micrographs show that regul…

Radiation polymerizationDispersion polymerizationDense carbon dioxideRadiationMaterials scienceBulk polymerizationSettore ING-IND/27 - Chimica Industriale E TecnologicaChemical reactionVinyl monomerSupercritical fluidchemistry.chemical_compoundMonomerchemistryPolymerizationChemical engineeringPolymer chemistryMolar mass distributionMethyl methacrylateRadiation Physics and Chemistry
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Direct synthesis of dimethyl carbonate with supercritical carbon dioxide: characterization of a key organotin oxide intermediate

2006

The direct synthesis of dimethyl carbonate (DMC) using carbon dioxide as solvent and reagent for its fixation to methanol was explored with din-butyldimethoxystannane in order to get insight into the reaction mechanism for activity improvement. Catalytic runs including recycling experiments allowed isolation and characterization by NMR, IR, and single-crystal X-ray diffraction of a new tin complex containing 10 tin atoms. This compound could be prepared independently and is considered as a resting species. The yield of DMC is highest under 20 MPa pressure that fits with a monophasic supercritical medium in agreement with fluid phase equilibria calculations. In line, preliminary kinetics and…

Reaction mechanismdibutyldimethoxystannaneSupercritical carbon dioxide010405 organic chemistryInorganic chemistryorganotin oxide[ CHIM.INOR ] Chemical Sciences/Inorganic chemistryGeneral Chemistry[CHIM.INOR]Chemical Sciences/Inorganic chemistry010402 general chemistry01 natural sciencesStannaneCatalysisSupercritical fluid0104 chemical sciencesCatalysischemistry.chemical_compoundcarbon dioxide–methanol phase diagramschemistrysupercritical carbon dioxideReagentdimethyl carbonateMethanolDimethyl carbonateComputingMilieux_MISCELLANEOUS
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