Articles de revues sur le sujet « Calcium carbonate (CaCO3) cycle »
Pour voir les autres types de publications sur ce sujet consultez le lien suivant : Calcium carbonate (CaCO3) cycle.
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Consultez les 50 meilleurs articles de revues pour votre recherche sur le sujet « Calcium carbonate (CaCO3) cycle ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Parcourez les articles de revues sur diverses disciplines et organisez correctement votre bibliographie.
1
Zou, Zhaoyong, Wouter J. E. M. Habraken, Galina Matveeva, Anders C. S. Jensen, Luca Bertinetti, Matthew A. Hood, Chang-yu Sun et al. « A hydrated crystalline calcium carbonate phase : Calcium carbonate hemihydrate ». Science 363, no 6425 (24 janvier 2019) : 396–400. http://dx.doi.org/10.1126/science.aav0210.
Texte intégralRésumé :
As one of the most abundant materials in the world, calcium carbonate, CaCO3, is the main constituent of the skeletons and shells of various marine organisms. It is used in the cement industry and plays a crucial role in the global carbon cycle and formation of sedimentary rocks. For more than a century, only three polymorphs of pure CaCO3—calcite, aragonite, and vaterite—were known to exist at ambient conditions, as well as two hydrated crystal phases, monohydrocalcite (CaCO3·1H2O) and ikaite (CaCO3·6H2O). While investigating the role of magnesium ions in crystallization pathways of amorphous calcium carbonate, we unexpectedly discovered an unknown crystalline phase, hemihydrate CaCO3·½H2O, with monoclinic structure. This discovery may have important implications in biomineralization, geology, and industrial processes based on hydration of CaCO3.
2
Battaglia, Gianna, Marco Steinacher et Fortunat Joos. « A probabilistic assessment of calcium carbonate export and dissolution in the modern ocean ». Biogeosciences 13, no 9 (13 mai 2016) : 2823–48. http://dx.doi.org/10.5194/bg-13-2823-2016.
Texte intégralRésumé :
Abstract. The marine cycle of calcium carbonate (CaCO3) is an important element of the carbon cycle and co-governs the distribution of carbon and alkalinity within the ocean. However, CaCO3 export fluxes and mechanisms governing CaCO3 dissolution are highly uncertain. We present an observationally constrained, probabilistic assessment of the global and regional CaCO3 budgets. Parameters governing pelagic CaCO3 export fluxes and dissolution rates are sampled using a Monte Carlo scheme to construct a 1000-member ensemble with the Bern3D ocean model. Ensemble results are constrained by comparing simulated and observation-based fields of excess dissolved calcium carbonate (TA*). The minerals calcite and aragonite are modelled explicitly and ocean–sediment fluxes are considered. For local dissolution rates, either a strong or a weak dependency on CaCO3 saturation is assumed. In addition, there is the option to have saturation-independent dissolution above the saturation horizon. The median (and 68 % confidence interval) of the constrained model ensemble for global biogenic CaCO3 export is 0.90 (0.72–1.05) Gt C yr−1, that is within the lower half of previously published estimates (0.4–1.8 Gt C yr−1). The spatial pattern of CaCO3 export is broadly consistent with earlier assessments. Export is large in the Southern Ocean, the tropical Indo–Pacific, the northern Pacific and relatively small in the Atlantic. The constrained results are robust across a range of diapycnal mixing coefficients and, thus, ocean circulation strengths. Modelled ocean circulation and transport timescales for the different set-ups were further evaluated with CFC11 and radiocarbon observations. Parameters and mechanisms governing dissolution are hardly constrained by either the TA* data or the current compilation of CaCO3 flux measurements such that model realisations with and without saturation-dependent dissolution achieve skill. We suggest applying saturation-independent dissolution rates in Earth system models to minimise computational costs.
3
Fischer, M., D. N. Thomas, A. Krell, G. Nehrke, J. Göttlicher, L. Norman, C. Riaux-Gobin et G. S. Dieckmann. « Quantification of ikaite in Antarctic sea ice ». Cryosphere Discussions 6, no 1 (3 février 2012) : 505–30. http://dx.doi.org/10.5194/tcd-6-505-2012.
Texte intégralRésumé :
Abstract. Calcium carbonate precipitation in sea ice can increase pCO2 during precipitation in winter and decrease pCO2 during dissolution in spring. CaCO3 precipitation in sea ice is thought to potentially drive significant CO2 uptake by the ocean. However, little is known about the quantitative spatial and temporal distribution of CaCO3 within sea ice. This is the first quantitative study of hydrous calcium carbonate, as ikaite, in sea ice and discusses its potential significance for the carbon cycle in polar oceans. Ice cores and brine samples were collected from pack and land fast sea ice between September and December 2007 during an expedition in the East Antarctic and another off Terre Adélie, Antarctica. Samples were analysed for CaCO3, Salinity, DOC, DON, Phosphate, and total alkalinity. A relationship between the measured parameters and CaCO3 precipitation could not be observed. We found calcium carbonate, as ikaite, mostly in the top layer of sea ice with values up to 126 mg ikaite per liter melted sea ice. This potentially represents a contribution between 0.12 and 9 Tg C to the annual carbon flux in polar oceans. The horizontal distribution of ikaite in sea ice was heterogenous. We also found the precipitate in the snow on top of the sea ice.
4
Battaglia, G., M. Steinacher et F. Joos. « A probabilistic assessment of calcium carbonate export and dissolution in the modern ocean ». Biogeosciences Discussions 12, no 24 (21 décembre 2015) : 20223–82. http://dx.doi.org/10.5194/bgd-12-20223-2015.
Texte intégralRésumé :
Abstract. The marine cycle of calcium carbonate (CaCO3) is an important element of the carbon cycle and co-governs the distribution of carbon and alkalinity within the ocean. However, CaCO3 fluxes and mechanisms governing CaCO3 dissolution are highly uncertain. We present an observationally-constrained, probabilistic assessment of the global and regional CaCO3 budgets. Parameters governing pelagic CaCO3 export fluxes and dissolution rates are sampled using a Latin-Hypercube scheme to construct a 1000 member ensemble with the Bern3D ocean model. Ensemble results are constrained by comparing simulated and observation-based fields of excess dissolved calcium carbonate (TA*). The minerals calcite and aragonite are modelled explicitly and ocean–sediment fluxes are considered. For local dissolution rates either a strong, a weak or no dependency on CaCO3 saturation is assumed. Median (68 % confidence interval) global CaCO3 export is 0.82 (0.67–0.98) Gt PIC yr−1, within the lower half of previously published estimates (0.4–1.8 Gt PIC yr−1). The spatial pattern of CaCO3 export is broadly consistent with earlier assessments. Export is large in the Southern Ocean, the tropical Indo–Pacific, the northern Pacific and relatively small in the Atlantic. Dissolution within the 200 to 1500 m depth range (0.33; 0.26–0.40 Gt PIC yr−1) is substantially lower than inferred from the TA*-CFC age method (1 ± 0.5 Gt PIC yr−1). The latter estimate is likely biased high as the TA*-CFC method neglects transport. The constrained results are robust across a range of diapycnal mixing coefficients and, thus, ocean circulation strengths. Modelled ocean circulation and transport time scales for the different setups were further evaluated with CFC11 and radiocarbon observations. Parameters and mechanisms governing dissolution are hardly constrained by either the TA* data or the current compilation of CaCO3 flux measurements such that model realisations with and without saturation-dependent dissolution achieve skill. We suggest to apply saturation-independent dissolution rates in Earth System Models to minimise computational costs.
5
Gong, Dehong, Zhongxiao Zhang et Ting Zhao. « Decay on Cyclic CO2 Capture Performance of Calcium-Based Sorbents Derived from Wasted Precursors in Multicycles ». Energies 15, no 9 (3 mai 2022) : 3335. http://dx.doi.org/10.3390/en15093335.
Texte intégralRésumé :
In order to obtain the cheap waste calcium-based sorbent, three wasted CaCO3 precursors, namely carbide slag, chicken eggshells, and analytical reagent-grade calcium carbonate, were selected and prepared at 700 °C to form calcium-based sorbents for CO2 capture. TGA was used to test the CO2 uptake performance of each calcium-based sorbent in 20 cycles. To identify the decay mechanism of CO2 uptake with an increasing number of cycles, all calcium-based sorbents were characterized by using XRF, XRD, and N2 adsorption. The specific surface area of calcium-based sorbents was used to redefine the formula of cyclic carbonation reactivity decay. The carbonation conversion rate of three calcium-based sorbents exhibited a decreasing trend as the cycle number increased. Chicken eggshells exhibited the most significant decrease rate (over 50% compared with Cycle 1), while carbide slag and analytical reagent-grade calcium carbonate showed a flat linear decline trend. The specific surface area of the samples was used to calculate carbonation conversion for an infinite number of cycles. The carbonation conversion rates of three calcium-based sorbents were estimated to decrease to 0.2898, 0.1455, and 0.3438 mol/mol, respectively, after 100 cycles.
6
Chafidz, Achmad. « Polypropylene/CaCO<sub>3</sub> ; Nanocomposites Fabricated Using Masterbatch : Effect of Nano-CaCO<sub>3</sub> ; Loadings and Re-Processing on the Melting Properties ». Materials Science Forum 1067 (10 août 2022) : 73–78. http://dx.doi.org/10.4028/p-2u9f04.
Texte intégralRésumé :
Polypropylene filled calcium carbonate (CaCO3) nanocomposites were fabricated by employing melt blending/compounding method using masterbatch. To investigate the efffect of reprocessing on the melting properties of PP/CaCO3 nanocomposites, the melt compounding process was conducted twice (two cycles). The effect of nano-CaCO3 loadings (i.e. 5, 10 and 15 wt%) on the melting properties of PP/CaCO3 nanocomposites were also studied. The meling properties of the nanocomposites were analyzed by using a DSC (Differential Scanning Calorimetry). Additionally, the nanocomposites samples were also analyzed by an SEM (Scanning Electron Microscopy). The SEM analysis results revealed that at higher nano-CaCO3 loading (i.e. 15 wt%), the nano-CaCO3 particles in the 2nd cycle were more well distributed/dispersed in the polypropylene matrix as compared to the 1st cycle. Whereas, the DSC test results showed that the crystallinity of the nanocomposites samples were similar to that of neat PP for the 1st cycle of melt blending process, which was about 41%. In the other hand, for the 2nd cycle, the crystallinity of the samples slightly increased wtih increasing nano-CaCO3 loadings, which were about 39.6; 43; 44% for nano-CaCO3 loadings of 0, 5, 10 wt%, respectively. Nevertheless, at the highest nano-CaCO3 loadings (i.e. 15 wt%), the crystallinity of the nanocomposites (i.e. NCC-15-II) decreased again and lower than that of neat PP, which was about 37.7%.
7
Dieckmann, G. S., G. Nehrke, C. Uhlig, J. Göttlicher, S. Gerland, M. A. Granskog et D. N. Thomas. « Brief communication : ikaite (CaCO<sub>3</sub>*6H<sub>2</sub>O) discovered in Arctic sea ice ». Cryosphere Discussions 4, no 1 (9 février 2010) : 153–61. http://dx.doi.org/10.5194/tcd-4-153-2010.
Texte intégralRésumé :
Abstract. We report for the first time on the discovery of calcium carbonate crystals as ikaite (CaCO3*6H2O) in sea ice from the Arctic (Kongsfjorden, Svalbard). This finding demonstrates that the precipitation of calcium carbonate during the freezing of sea ice is not restricted to the Antarctic, where it was observed for the first time in 2008. This finding is an important step in the quest to quantify its impact on the sea ice driven carbon cycle and should in the future enable improvement parametrization sea ice carbon models.
8
Dieckmann, G. S., G. Nehrke, C. Uhlig, J. Göttlicher, S. Gerland, M. A. Granskog et D. N. Thomas. « Brief Communication : Ikaite (CaCO<sub>3</sub>·6H<sub>2</sub>O) discovered in Arctic sea ice ». Cryosphere 4, no 2 (28 mai 2010) : 227–30. http://dx.doi.org/10.5194/tc-4-227-2010.
Texte intégralRésumé :
Abstract. We report for the first time on the discovery of calcium carbonate crystals as ikaite (CaCO3·6H2O) in sea ice from the Arctic (Kongsfjorden, Svalbard) as confirmed by morphology and indirectly by X-ray diffraction as well as XANES spectroscopy of its amorophous decomposition product. This finding demonstrates that the precipitation of calcium carbonate during the freezing of sea ice is not restricted to the Antarctic, where it was observed for the first time in 2008. This observation is an important step in the quest to quantify its impact on the sea ice driven carbon cycle.
9
Rigual Hernández, Andrés S., Thomas W. Trull, Scott D. Nodder, José A. Flores, Helen Bostock, Fátima Abrantes, Ruth S. Eriksen et al. « Coccolithophore biodiversity controls carbonate export in the Southern Ocean ». Biogeosciences 17, no 1 (17 janvier 2020) : 245–63. http://dx.doi.org/10.5194/bg-17-245-2020.
Texte intégralRésumé :
Abstract. Southern Ocean waters are projected to undergo profound changes in their physical and chemical properties in the coming decades. Coccolithophore blooms in the Southern Ocean are thought to account for a major fraction of the global marine calcium carbonate (CaCO3) production and export to the deep sea. Therefore, changes in the composition and abundance of Southern Ocean coccolithophore populations are likely to alter the marine carbon cycle, with feedbacks to the rate of global climate change. However, the contribution of coccolithophores to CaCO3 export in the Southern Ocean is uncertain, particularly in the circumpolar subantarctic zone that represents about half of the areal extent of the Southern Ocean and where coccolithophores are most abundant. Here, we present measurements of annual CaCO3 flux and quantitatively partition them amongst coccolithophore species and heterotrophic calcifiers at two sites representative of a large portion of the subantarctic zone. We find that coccolithophores account for a major fraction of the annual CaCO3 export, with the highest contributions in waters with low algal biomass accumulations. Notably, our analysis reveals that although Emiliania huxleyi is an important vector for CaCO3 export to the deep sea, less abundant but larger species account for most of the annual coccolithophore CaCO3 flux. This observation contrasts with the generally accepted notion that high particulate inorganic carbon accumulations during the austral summer in the subantarctic Southern Ocean are mainly caused by E. huxleyi blooms. It appears likely that the climate-induced migration of oceanic fronts will initially result in the poleward expansion of large coccolithophore species increasing CaCO3 production. However, subantarctic coccolithophore populations will eventually diminish as acidification overwhelms those changes. Overall, our analysis emphasizes the need for species-centred studies to improve our ability to project future changes in phytoplankton communities and their influence on marine biogeochemical cycles.
10
Anggoro, B. M., et A. Sugandi. « Effect of Calcium Carbonate Application on Initial Vegetative Growth of Oil Palm Planted on Deep Peat ». IOP Conference Series : Earth and Environmental Science 1308, no 1 (1 février 2024) : 012027. http://dx.doi.org/10.1088/1755-1315/1308/1/012027.
Texte intégralRésumé :
Abstract The main challenge of planting oil palm on deep peat is naturally acidic soil pH which affects rooting development and activity and uptake of nutrients. Considering one life cycle of oil palm can be up to ≥20 years, ensuring optimum growth of palms since its initial planting is essential. Calcium carbonate (CaCO3) application is a standard practice to increase soil pH, including on peat soils. However, the effective rate and effects of its application to palm growth are still lacking. This trial is aimed to see the effect of CaCO3 application on the vegetative growth of oil palms planted on deep peat in the initial years of planting. The trial was conducted in an oil palm plantation in Pangkalan Kerinci-Riau with a split-plot randomized complete block design. Basal application of CaCO3 for the first three consecutive years of planting with three different rates and additional rates of CaCO3 and liquid lime per palm basis were the main and sub-treatments of this trial. Significant differences were found in frond length, leaf area, leaf area index, and frond dry weight at the immature stage in which palms treated with basal CaCO3 showed better growth. At the young mature stage, significant differences were found only in leaf area, leaf area index, and the number of green fronds. A significant difference for sub-treatment was found only in the leaf area index. The result indicated that application of CaCO3 as basal application during immature stage could improve palm’s growth whereas additional CaCO3 per palm basis may not necessarily result in better growth.
11
Castro-Sanguino, C., YM Bozec et PJ Mumby. « Dynamics of carbonate sediment production by Halimeda : implications for reef carbonate budgets ». Marine Ecology Progress Series 639 (2 avril 2020) : 91–106. http://dx.doi.org/10.3354/meps13265.
Texte intégralRésumé :
Reef carbonate production and sediment generation are key processes for coral reef development and shoreline protection. The calcified green alga Halimeda is a major contributor of calcareous sediments, but rates of production and herbivory upon Halimeda are driven by biotic and environmental factors. Consequently, estimating rates of calcium carbonate (CaCO3) production and transformation into sediment requires the integration of Halimeda gains and losses across habitats and seasons, which is rarely considered in carbonate budgets. Using seasonal rates of recruitment, growth, senescence and herbivory derived from observations and manipulative experiments, we developed an individual-based model to quantify the annual cycle of Halimeda carbonate and sediment production at Heron Island, Great Barrier Reef. Halimeda population dynamics were simulated both within and outside branching Acropora canopies, which provide refuge from herbivory. Shelter from herbivory allowed larger Halimeda thalli to grow, leading to higher rates of carbonate accumulation (3.9 and 0.9 kg CaCO3 m-2 yr-1 within and outside Acropora canopies, respectively) and sediment production (2.5 versus 1.0 kg CaCO3 m-2 yr-1, respectively). Overall, 37% of the annual carbonate production was transformed into sediments through senescence (84%) and fish herbivory (16%), with important variations among seasons and habitats. Our model underlines that algal rates of carbonate production are likely to be underestimated if herbivory is not integrated into the carbonate budget, and reveals an important indirect pathway by which structurally complex coral habitats contribute to reef carbonate budgets, suggesting that coral losses due to climate change may lead to further declines in reef sediment production.
12
Noor Zuhaira, Abd Aziz, et Mohamed Rahmah. « Effect of Calcium Carbonate on Thermal Properties of CaCO3/Kenaf/HDPE and CaCO3/Rice Husk/HDPE Composites ». Advanced Materials Research 812 (septembre 2013) : 175–80. http://dx.doi.org/10.4028/www.scientific.net/amr.812.175.
Texte intégralRésumé :
In this research, the thermal properties of 30% filler loading of natural fibers with varying filler loadings of calcium carbonate (CaCO3) were studied. CaCO3 was compounded using twin-screw extruder with rice husk/high density polyethylene (HDPE) and kenaf/HDPE composites to produce composites. Compounded composites were prepared and tested for thermal properties. The thermal stability of the components was examined by thermogravimetric analysis (TGA) and differential scanning calorimetric (DSC) to identify the influence of CaCO3 filler loading on thermal properties of the composites. The cycle heating for TGA was 30-800°C while for differential scanning calorimetric (DSC) was 30-300°C. Melting temperature (Tm) of kenaf/HDPE hybrid composites increased slightly with addition of 10% CaCO3. However, decreasing Tm was found for all CaCO3 filler loading in rice husk/HDPE composites. The DSC analysis showed that the degree of crystallinity (Xc) of hybrid composite decrease with the addition of CaCO3 filler loading. From TGA result, CaCO3/kenaf/HDPE hybrid composite showed better thermal stability compared to CaCO3/rice husk/HDPE hybrid composite.
13
Pinsonneault, A. J., H. D. Matthews, E. D. Galbraith et A. Schmittner. « Calcium carbonate production response to future ocean warming and acidification ». Biogeosciences Discussions 8, no 6 (13 décembre 2011) : 11863–97. http://dx.doi.org/10.5194/bgd-8-11863-2011.
Texte intégralRésumé :
Abstract. Anthropogenic carbon dioxide (CO2) emissions are acidifying the ocean, affecting calcification rates in pelagic organisms and thereby modifying the oceanic alkalinity cycle. However, the responses of pelagic calcifying organisms to acidification vary widely between species, contributing uncertainty to predictions of atmospheric CO2 and the resulting climate change. Meanwhile, ocean warming caused by rising CO2 is expected to drive increased growth rates of all pelagic organisms, including calcifiers. It thus remains unclear whether anthropogenic CO2 will ultimately increase or decrease the globally-integrated pelagic calcification rate. Here, we assess the importance of this uncertainty by introducing a variable dependence of calcium carbonate (CaCO3) production on calcite saturation state (ΩCaCO3) in the University of Victoria Earth System Climate Model, an intermediate complexity coupled carbon-climate model. In a series of model simulations, we examine the impact of this parameterization on global ocean carbon cycling under two CO2 emissions scenarios, both integrated to the year 3500. The simulations show a significant sensitivity of the vertical and surface horizontal alkalinity gradients to the parameterization, as well as the removal of alkalinity from the ocean through CaCO3 burial. These sensitivities result in an additional oceanic uptake of carbon when calcification depends on ΩCaCO3 (of up to 13 % of total carbon emissions), compared to the case where calcification is insensitive to acidification. In turn, this response causes a reduction of global surface air temperature of up to 0.4 °C in year 3500, a 13 % reduction in the amplitude of warming. Narrowing these uncertainties will require better understanding of both temperature and acidification effects on pelagic calcifiers. Preliminary examination suggests that alkalinity observations can be used to constrain the range of uncertainties and may exclude large sensitivities of CaCO3 production on ΩCaCO3.
14
Vincent, Julia, Béatrice Colin, Isabelle Lanneluc, Philippe Refait, René Sabot, Marc Jeannin et Sophie Sablé. « La biocalcification bactérienne en milieu marin et ses applications ». Matériaux & ; Techniques 110, no 6 (2022) : 606. http://dx.doi.org/10.1051/mattech/2023004.
Texte intégralRésumé :
La précipitation du carbonate de calcium (CaCO3) biologiquement induite en milieu marin joue un rôle important dans le cycle biogéochimique du carbone. Cette biocalcification est gouvernée par quatre facteurs clés : le taux de carbone inorganique dissous dont dépend le taux de carbonates (CO32−) dans le système, le taux d’ions calciques (Ca2+), le pH et la disponibilité des sites de nucléation c’est-à-dire des zones de cristallisation primaire de la phase solide du minéral. Les bactéries impliquées dans la biocalcification marine vont alors agir sur un ou plusieurs de ces facteurs. Ce processus naturel, qui se produit dans divers contextes géologiques, peut être imité afin de développer un certain nombre de technologies permettant la séquestration des métaux lourds, la protection des métaux contre la corrosion, la restauration et le renforcement de matériaux préexistants et la consolidation de matériaux granulaires. Cette étude passe en revue les différentes activités métaboliques microbiennes menant à la précipitation du CaCO3 ainsi que leurs applications potentielles en milieu marin.
15
Planchat, Alban, Lester Kwiatkowski, Laurent Bopp, Olivier Torres, James R. Christian, Momme Butenschön, Tomas Lovato et al. « The representation of alkalinity and the carbonate pump from CMIP5 to CMIP6 Earth system models and implications for the carbon cycle ». Biogeosciences 20, no 7 (3 avril 2023) : 1195–257. http://dx.doi.org/10.5194/bg-20-1195-2023.
Texte intégralRésumé :
Abstract. Ocean alkalinity is critical to the uptake of atmospheric carbon in surface waters and provides buffering capacity towards the associated acidification. However, unlike dissolved inorganic carbon (DIC), alkalinity is not directly impacted by anthropogenic carbon emissions. Within the context of projections of future ocean carbon uptake and potential ecosystem impacts, especially through Coupled Model Intercomparison Projects (CMIPs), the representation of alkalinity and the main driver of its distribution in the ocean interior, the calcium carbonate cycle, have often been overlooked. Here we track the changes from CMIP5 to CMIP6 with respect to the Earth system model (ESM) representation of alkalinity and the carbonate pump which depletes the surface ocean in alkalinity through biological production of calcium carbonate and releases it at depth through export and dissolution. We report an improvement in the representation of alkalinity in CMIP6 ESMs relative to those in CMIP5, with CMIP6 ESMs simulating lower surface alkalinity concentrations, an increased meridional surface gradient and an enhanced global vertical gradient. This improvement can be explained in part by an increase in calcium carbonate (CaCO3) production for some ESMs, which redistributes alkalinity at the surface and strengthens its vertical gradient in the water column. We were able to constrain a particulate inorganic carbon (PIC) export estimate of 44–55 Tmol yr−1 at 100 m for the ESMs to match the observed vertical gradient of alkalinity. Reviewing the representation of the CaCO3 cycle across CMIP5/6, we find a substantial range of parameterizations. While all biogeochemical models currently represent pelagic calcification, they do so implicitly, and they do not represent benthic calcification. In addition, most models simulate marine calcite but not aragonite. In CMIP6, certain model groups have increased the complexity of simulated CaCO3 production, sinking, dissolution and sedimentation. However, this is insufficient to explain the overall improvement in the alkalinity representation, which is therefore likely a result of marine biogeochemistry model tuning or ad hoc parameterizations. Although modellers aim to balance the global alkalinity budget in ESMs in order to limit drift in ocean carbon uptake under pre-industrial conditions, varying assumptions related to the closure of the budget and/or the alkalinity initialization procedure have the potential to influence projections of future carbon uptake. For instance, in many models, carbonate production, dissolution and burial are independent of the seawater saturation state, and when considered, the range of sensitivities is substantial. As such, the future impact of ocean acidification on the carbonate pump, and in turn ocean carbon uptake, is potentially underestimated in current ESMs and is insufficiently constrained.
16
Ridgwell, A., J. C. Hargreaves, N. R. Edwards, J. D. Annan, T. M. Lenton, R. Marsh, A. Yool et A. Watson. « Marine geochemical data assimilation in an efficient Earth System Model of global biogeochemical cycling ». Biogeosciences 4, no 1 (25 janvier 2007) : 87–104. http://dx.doi.org/10.5194/bg-4-87-2007.
Texte intégralRésumé :
Abstract. We have extended the 3-D ocean based "Grid ENabled Integrated Earth system model" (GENIE-1) to help understand the role of ocean biogeochemistry and marine sediments in the long-term (~100 to 100 000 year) regulation of atmospheric CO2, and the importance of feedbacks between CO2 and climate. Here we describe the ocean carbon cycle, which in its first incarnation is based around a simple single nutrient (phosphate) control on biological productivity. The addition of calcium carbonate preservation in deep-sea sediments and its role in regulating atmospheric CO2 is presented elsewhere (Ridgwell and Hargreaves, 2007). We have calibrated the model parameters controlling ocean carbon cycling in GENIE-1 by assimilating 3-D observational datasets of phosphate and alkalinity using an ensemble Kalman filter method. The calibrated (mean) model predicts a global export production of particulate organic carbon (POC) of 8.9 PgC yr−1, and reproduces the main features of dissolved oxygen distributions in the ocean. For estimating biogenic calcium carbonate (CaCO3) production, we have devised a parameterization in which the CaCO3:POC export ratio is related directly to ambient saturation state. Calibrated global CaCO3 export production (1.2 PgC yr-1) is close to recent marine carbonate budget estimates. The GENIE-1 Earth system model is capable of simulating a wide variety of dissolved and isotopic species of relevance to the study of modern global biogeochemical cycles as well as past global environmental changes recorded in paleoceanographic proxies. Importantly, even with 12 active biogeochemical tracers in the ocean and including the calculation of feedbacks between atmospheric CO2 and climate, we achieve better than 1000 years per (2.4 GHz) CPU hour on a desktop PC. The GENIE-1 model thus provides a viable alternative to box and zonally-averaged models for studying global biogeochemical cycling over all but the very longest (>1 000 000 year) time-scales.
17
Bach, L. T. « Reconsidering the role of carbonate ion concentration in calcification by marine organisms ». Biogeosciences 12, no 16 (19 août 2015) : 4939–51. http://dx.doi.org/10.5194/bg-12-4939-2015.
Texte intégralRésumé :
Abstract. Marine organisms precipitate 0.5–2.0 Gt of carbon as calcium carbonate (CaCO3) every year with a profound impact on global biogeochemical element cycles. Biotic calcification relies on calcium ions (Ca2+) and usually on bicarbonate ions (HCO3−) as CaCO3 substrates and can be inhibited by high proton (H+) concentrations. The seawater concentration of carbonate ions (CO32−) and the CO32−-dependent CaCO3 saturation state (ΩCaCO3) seem to be irrelevant in this production process. Nevertheless, calcification rates and the success of calcifying organisms in the oceans often correlate surprisingly well with these two carbonate system parameters. This study addresses this dilemma through the rearrangement of carbonate system equations which revealed an important proportionality between [CO32−] or ΩCaCO3and the ratio of [HCO3−] to [H+]. Due to this proportionality, calcification rates will always correlate as well with [HCO3−] / [H+] as they do with [CO32−] or ΩCaCO3 when temperature, salinity, and pressure are constant. Hence, [CO32−] and ΩCaCO3 may simply be very good proxies for the control by [HCO3−] / [H+], where [HCO3−] serves as the inorganic carbon substrate and [H+] functions as a calcification inhibitor. If the "substrate–inhibitor ratio" (i.e., [HCO3−] / [H+]) rather than [CO32−] or ΩCaCO3 controls biotic CaCO3 formation, then some of the most common paradigms in ocean acidification research need to be reviewed. For example, the absence of a latitudinal gradient in [HCO3−] / [H+] in contrast to [CO32−] and ΩCaCO3 could modify the common assumption that high latitudes are affected most severely by ocean acidification.
18
Bach, L. T. « Reconsidering the role of carbonate ion concentration in calcification by marine organisms ». Biogeosciences Discussions 12, no 9 (5 mai 2015) : 6689–722. http://dx.doi.org/10.5194/bgd-12-6689-2015.
Texte intégralRésumé :
Abstract. Marine organisms precipitate 0.5–2.0 Gt of carbon as calcium carbonate (CaCO3) every year with a profound impact on global biogeochemical element cycles. Biotic calcification relies on calcium ions (Ca2+) and generally on bicarbonate ions (HCO3−) as CaCO3 substrates and can be inhibited by high proton (H+) concentrations. The seawater concentration of carbonate ions (CO32−) and the CO32−-dependent CaCO3 saturation state (ΩCaCO3) seem to be irrelevant in this production process. Nevertheless, calcification rates and the success of calcifying organisms in the oceans often correlate surprisingly well with these two carbonate system parameters. This study addresses this dilemma through rearrangement of carbonate system equations which revealed an important proportionality between [CO32−] or ΩCaCO3 and the ratio of [HCO3−] to [H+]. Due to this proportionality, calcification rates will always correlate equally well with [HCO3−]/[H+] as with [CO32−] or ΩCaCO3 when temperature, salinity, and pressure are constant. Hence, [CO32−] and ΩCaCO3 may simply be very good proxies for the control by [HCO3−]/[H+] where [HCO3−] would be the inorganic carbon substrate and [H+] would function as calcification inhibitor. If the "substrate-inhibitor ratio" (i.e. [HCO3−]/[H+]) rather than [CO32−] or ΩCaCO3 controls CaCO3 formation then some of the most common paradigms in ocean acidification research need to be reviewed. For example, the absence of a latitudinal gradient in [HCO3−]/[H+] in contrast to [CO32−] and ΩCaCO3 could modify the common assumption that high latitudes are affected most severely by ocean acidification.
19
Batukaev, Abdul-Malik A., Anatoly P. Endovitsky, Andrey G. Andreev, Valery P. Kalinichenko, Tatiana M. Minkina, Zaurbek S. Dikaev, Saglara S. Mandzhieva et Svetlana N. Sushkova. « Ion association in water solution of soil and vadose zone of chestnut saline solonetz as a driver of terrestrial carbon sink ». Solid Earth 7, no 2 (15 mars 2016) : 415–23. http://dx.doi.org/10.5194/se-7-415-2016.
Texte intégralRésumé :
Abstract. The assessment of soil and vadose zone as the drains for carbon sink and proper modeling of the effects and extremes of biogeochemical cycles in the terrestrial biosphere are the key components to understanding the carbon cycle, global climate system, and aquatic and terrestrial system uncertainties. Calcium carbonate equilibrium causes saturation of solution with CaCO3, and it determines its material composition, migration and accumulation of salts. In a solution electrically neutral ion pairs are formed: CaCO30, CaSO40, MgCO30, and MgSO40, as well as charged ion pairs CaHCO3+, MgHCO3+, NaCO3−, NaSO4−, CaOH+, and MgOH+. The calcium carbonate equilibrium algorithm, mathematical model and original software to calculate the real equilibrium forms of ions and to determine the nature of calcium carbonate balance in a solution were developed. This approach conducts the quantitative assessment of real ion forms of solution in solonetz soil and vadose zone of dry steppe taking into account the ion association at high ionic strength of saline soil solution. The concentrations of free and associated ion form were calculated according to analytical ion concentration in real solution. In the iteration procedure, the equations were used to find the following: ion material balance, a linear interpolation of equilibrium constants, a method of ionic pairs, the laws of initial concentration preservation, operating masses of equilibrium system, and the concentration constants of ion pair dissociation. The coefficient of ion association γe was determined as the ratio of ions free form to analytical content of ion γe = Cass∕Can. Depending on soil and vadose zone layer, concentration and composition of solution in the ionic pair's form are 11–52 % Ca2+; 22.2–54.6 % Mg2+; 1.1–10.5 % Na+; 3.7–23.8 HCO3−, 23.3–61.6 % SO42−, and up to 85.7 % CO32−. The carbonate system of soil and vadose zone water solution helps to explain the evolution of salted soils, vadose and saturation zones, and landscape. It also helps to improve the soil maintenance, plant nutrition and irrigation. The association of ions in soil solutions is one of the drivers promoting transformation of solution, excessive fluxes of carbon in the soil, and loss of carbon from soil through vadose zone.
20
van Lier, J. B., et M. A. Boncz. « Controlling calcium precipitation in an integrated anaerobic–aerobic treatment system of a “zero-discharge” paper mill ». Water Science and Technology 45, no 10 (1 mai 2002) : 341–47. http://dx.doi.org/10.2166/wst.2002.0367.
Texte intégralRésumé :
The pulp and paper industry uses significant amounts of water and energy for the paper production process. Closing the water cycles in this industry, therefore, promises large benefits for the environment and has the potential of huge cost savings for the industry. Closing the water cycle on the other hand also introduces problems with process water quality, quality of the end-product and scaling, owing to increased water contamination. An inline treatment system is discussed in which anaerobic-aerobic bio-reactors perform a central role for removing both organic and inorganic pollutants from the process water cycle. In the proposed set-up, the organic compounds are converted to methane gas and reused for energy supply, while sulphur compounds are stripped from the process cycle and calcium carbonate is removed by precipitation. Improved control of the treatment system will direct the inorganic precipitates to a location where it does not adversely affect paper production and process water treatment. A simulation program for triggering and controlling CaCO3 precipitation was developed that takes both biological conversions and all relevant chemical equilibria in the system into account. Simulation results are in good agreement with data gathered in a full-scale “zero-emission” paper plant and indicate that control of CaCO3 precipitation can be improved, e.g. in the aerobic post-treatment. Alternatively, a separate precipitation unit could be considered.
21
Xu, Hengchao, Xiaotong Peng, Shijie Bai, Kaiwen Ta, Shouye Yang, Shuangquan Liu, Ho Bin Jang et Zixiao Guo. « Precipitation of calcium carbonate mineral induced by viral lysis of cyanobacteria : evidence from laboratory experiments ». Biogeosciences 16, no 4 (28 février 2019) : 949–60. http://dx.doi.org/10.5194/bg-16-949-2019.
Texte intégralRésumé :
Abstract. Viruses have been acknowledged as being important components of the marine system for the past 2 decades, but their role in the functioning of the geochemical cycle has not been thoroughly elucidated to date. Virus-induced rupturing of cyanobacteria is theoretically capable of releasing intracellular bicarbonate and inducing the homogeneous nucleation of calcium carbonate; however, experiment-based support for virus-induced calcification is lacking. In this laboratory study, both water carbonate chemistry and precipitates were monitored during the viral infection and lysis of host cells. Our results show that viral lysis of cyanobacteria can influence the carbonate equilibrium system remarkably and promotes the formation and precipitation of carbonate minerals. Amorphous calcium carbonate (ACC) and aragonite were evident in the lysate, compared with the Mg(OH)2 (brucite in this paper) precipitate in noninfected cultures, implying that a different precipitation process had occurred. Based on the carbonate chemistry change and microstructure of the precipitation, we propose that viral lysis of cyanobacteria can construct a calcification environment where carbonate is the dominant inorganic carbon species. Numerous virus particles available in lysate may coprecipitate with the calcium carbonate. The experimental results presented in this study demonstrate both the pathway and the outcome with respect to how viruses influence the mineralization of carbonate minerals. It is suggested that viral calcification offers new perspectives on mechanisms of CaCO3 biomineralization and may play a crucial role within the Earth system.
22
Pinsonneault, A. J., H. D. Matthews, E. D. Galbraith et A. Schmittner. « Calcium carbonate production response to future ocean warming and acidification ». Biogeosciences 9, no 6 (29 juin 2012) : 2351–64. http://dx.doi.org/10.5194/bg-9-2351-2012.
Texte intégralRésumé :
Abstract. Anthropogenic carbon dioxide (CO2) emissions are acidifying the ocean, affecting calcification rates in pelagic organisms, and thereby modifying the oceanic carbon and alkalinity cycles. However, the responses of pelagic calcifying organisms to acidification vary widely between species, contributing uncertainty to predictions of atmospheric CO2 and the resulting climate change. At the same time, ocean warming caused by rising CO2 is expected to drive increased growth rates of all pelagic organisms, including calcifiers. It thus remains unclear whether anthropogenic CO2 emissions will ultimately increase or decrease pelagic calcification rates. Here, we assess the importance of this uncertainty by introducing a dependence of calcium carbonate (CaCO3) production on calcite saturation state (ΩCaCO3) in an intermediate complexity coupled carbon-climate model. In a series of model simulations, we examine the impact of several variants of this dependence on global ocean carbon cycling between 1800 and 3500 under two different CO2 emissions scenarios. Introducing a calcification-saturation state dependence has a significant effect on the vertical and surface horizontal alkalinity gradients, as well as on the removal of alkalinity from the ocean through CaCO3 burial. These changes result in an additional oceanic uptake of carbon when calcification depends on ΩCaCO3 (of up to 270 Pg C), compared to the case where calcification does not depend on acidification. In turn, this response causes a reduction of global surface air temperature of up to 0.4 °C in year 3500. Different versions of the model produced varying results, and narrowing this range of uncertainty will require better understanding of both temperature and acidification effects on pelagic calcifiers. Nevertheless, our results suggest that alkalinity observations can be used to constrain model results, and may not be consistent with the model versions that simulated stronger responses of CaCO3 production to changing saturation state.
23
Wu, Baizhi, Haibin Wang, Chunlei Li, Yuan Gong et Yi Wang. « Progress in the Preparation of Calcium Carbonate by Indirect Mineralization of Industrial By-Product Gypsum ». Sustainability 15, no 12 (15 juin 2023) : 9629. http://dx.doi.org/10.3390/su15129629.
Texte intégralRésumé :
To avoid the long-term pollution of land and water by industrial gypsum by-products, the exploitation of this resource has become a priority. The indirect synthesis of calcium carbonate from the industrial by-product gypsum has received substantial attention as a viable method for resource utilization. Currently, the primary problems in the indirect manufacture of calcium carbonate from the industrial by-product gypsum are additive recycling and process simplification. This paper describes the present state of development and compares various indirect mineralization systems. The factors affecting leaching and mineralization in the indirect mineralization of CO2 from by-product gypsum and the management of CaCO3 crystallinity are discussed, and the current additive regeneration cycle is summarized. The applications of other technologies in the indirect mineralization of by-product gypsum are also summarized, as are the obstacles, and required future work. This review provides guidelines for the laboratory indirect mineralization of by-product gypsum as well as practical applications.
24
Bates, N. R., M. I. Orchowska, R. Garley et J. T. Mathis. « Summertime calcium carbonate undersaturation in shelf waters of the western Arctic Ocean – how biological processes exacerbate the impact of ocean acidification ». Biogeosciences 10, no 8 (6 août 2013) : 5281–309. http://dx.doi.org/10.5194/bg-10-5281-2013.
Texte intégralRésumé :
Abstract. The Arctic Ocean accounts for only 4% of the global ocean area, but it contributes significantly to the global carbon cycle. Recent observations of seawater CO2-carbonate chemistry in shelf waters of the western Arctic Ocean, primarily in the Chukchi Sea, from 2009 to 2011 indicate that bottom waters are seasonally undersaturated with respect to calcium carbonate (CaCO3) minerals, particularly aragonite. Nearly 40% of sampled bottom waters on the shelf have saturation states less than one for aragonite (i.e., Ωaragonite < 1.0), thereby exposing the benthos to potentially corrosive water for CaCO3-secreting organisms, while 80% of bottom waters present had Ωaragonite values less than 1.5. Our observations indicate seasonal reduction of saturation states (Ω) for calcite (Ωcalcite) and aragonite (Ωaragonite) in the subsurface in the western Arctic by as much as 0.8 and 0.5, respectively. Such data indicate that bottom waters of the western Arctic shelves were already potentially corrosive for biogenic and sedimentary CaCO3 for several months each year. Seasonal changes in Ω are imparted by a variety of factors such as phytoplankton photosynthesis, respiration/remineralization of organic matter and air–sea gas exchange of CO2. Combined, these processes either increase or enhance in surface and subsurface waters, respectively. These seasonal physical and biological processes also act to mitigate or enhance the impact of Anthropocene ocean acidification (OA) on Ω in surface and subsurface waters, respectively. Future monitoring of the western Arctic shelves is warranted to assess the present and future impact of ocean acidification and seasonal physico-biogeochemical processes on Ω values and Arctic marine ecosystems.
25
Kanzaki, Yoshiki, Dominik Hülse, Sandra Kirtland Turner et Andy Ridgwell. « A model for marine sedimentary carbonate diagenesis and paleoclimate proxy signal tracking : IMP v1.0 ». Geoscientific Model Development 14, no 10 (7 octobre 2021) : 5999–6023. http://dx.doi.org/10.5194/gmd-14-5999-2021.
Texte intégralRésumé :
Abstract. The preservation of calcium carbonate in marine sediments is central to controlling the alkalinity balance of the ocean and, hence, the ocean–atmosphere partitioning of CO2. To successfully address carbon cycle–climate dynamics on geologic (≫1 kyr) timescales, Earth system models then require an appropriate representation of the primary controls on CaCO3 preservation. At the same time, marine sedimentary carbonates represent a major archive of Earth history, as they have the potential to preserve how seawater chemistry, isotopic composition, and even properties of planktic and benthic ecosystems, change with time. However, changes in preservation and even chemical erosion of previously deposited CaCO3, along with the biogenic reworking of upper portions of sediments, whereby sediment particles are translocated both locally and nonlocally between different depths in the sediments, all act to distort the recorded signal. Numerical models can aid in recovering what the “true” environmental changes might have been, but only if they appropriately account for these processes. Building on a classical 1-D reaction-transport framework, we present a new diagenetic model – IMP (Implicit model of Multiple Particles (and diagenesis)) – that simulates biogeochemical transformations in carbonate-hosted proxy signals by allowing for populations of solid carbonate particles to possess different physicochemical characteristics such as isotopic value, solubility and particle size. The model also utilizes a variable transition matrix to implement different styles of bioturbation. We illustrate the utility of the model for deciphering past environmental changes using several hypothesized transitions of seawater proxies obscured by sediment mixing and chemical erosion. To facilitate the use of IMP, we provide the model in Fortran, MATLAB and Python versions. We described IMP with integration into Earth system models in mind, and we present the description of this coupling of IMP with the “cGENIE.muffin” model in a subsequent paper.
26
Lerman, A., et F. T. Mackenzie. « CO<sub>2</sub> ; air-sea exchange due to calcium carbonate and organic matter storage : pre-industrial and Last Glacial Maximum estimates ». Biogeosciences Discussions 1, no 1 (26 août 2004) : 429–95. http://dx.doi.org/10.5194/bgd-1-429-2004.
Texte intégralRésumé :
Abstract. Release of CO2 from surface ocean water owing to precipitation of CaCO3 and the imbalance between biological production of organic matter and its respiration, and their net removal from surface water to sedimentary storage was studied by means of a model that gives the quotient θ=(CO2 released to the atmosphere)/(CaCO3 precipitated). The surface ocean layer is approximated by a euphotic zone, 50 m thick, that includes the shallower coastal area and open ocean. θ depends on water temperature, CaCO3 and organic carbon mass formed, and atmospheric CO2 concentration. At temperatures between 5 and 25°C, and three atmospheric CO2 pressures – 195 ppmv corresponding to the Last Glacial Maximum, 280 ppmv for the end of pre-industrial time, and 375 ppmv for the present – θ varies from a fraction of 0.38 to 0.79, increasing with decreasing temperature, increasing atmospheric CO2 content, and increasing CaCO3 precipitated mass (up to 45% of the DIC concentration in surface water). For a surface ocean layer that receives input of inorganic and organic carbon from land, the calculated CO2 flux to the atmosphere at the Last Glacial Maximum is 20 to 22×1012 mol/yr and in pre-industrial time it is 45 to 49×1012 mol/yr. In addition to the environmental factors mentioned above, flux to the atmosphere and increase of atmospheric CO2 depend on the thickness of the surface ocean layer. The significance of these fluxes and comparisons with the estimates of other investigators are discussed. Within the imbalanced global carbon cycle, our estimates are in agreement with the conclusions of others that the global ocean prior to anthropogenic emissions of CO2 to the atmosphere was losing carbon, calcium, and total alkalinity owing to precipitation of CaCO3 and consequent emission of CO2. Other pathways of CO2 exchange between the atmosphere and land organic reservoir and rock weathering may reduce the imbalances in the carbon cycle on millenial time scales.
27
Ávila, I., A. Mortari, A. M. Santos et P. M. Crnkovic. « THE CALCIUM LOOPING CYCLE STUDY FOR CAPTURING CARBON DIOXIDE APPLIED TO THE ENERGY GENERATION ». Revista de Engenharia Térmica 12, no 2 (31 décembre 2013) : 28. http://dx.doi.org/10.5380/reterm.v12i2.62041.
Texte intégralRésumé :
The calcium looping process (Ca-L) is a promising technology to reduce of the carbon dioxide (CO2) emissions when applied in energy generation systems. Ca-based materials (usually limestone) are used in this process as CO2 sorbents. Thus, the CO2 capture occurs by the reversible reaction between calcium oxide (CaO) and CO2, resulting in the calcium carbonate form (CaCO3). Compared to other technologies applied to carbon sequestration process, the Ca-L offers additional advantages such: the use of fluidized bed technology that is already well established; this process occurs at high temperature, and the excess of heat generated can be recovered; the cost of limestone sorbents is low because of its wide availability. However, in the applying the Ca-L process is essential to understand the mechanism and the effect of partial pressure of CO2 in both, calcination and carbonation processes; to investigate the effect of sintering and to evaluate the sorbent activity decay. In this paper, empirical technique such as thermogravimetry is applied to investigate the reactivity of dolomite as CO2 sorbent. The effect of CO2 high concentrations in both calcination/carbonation processes is also investigated.
28
Ibiyeye, Kehinde Muibat, et Abu Bakar Zakaria Zuki. « Cockle Shell-Derived Aragonite CaCO3 Nanoparticles for Co-Delivery of Doxorubicin and Thymoquinone Eliminates Cancer Stem Cells ». International Journal of Molecular Sciences 21, no 5 (10 mars 2020) : 1900. http://dx.doi.org/10.3390/ijms21051900.
Texte intégralRésumé :
Cancer stem cells CSCs (tumour-initiating cells) are responsible for cancer metastasis and recurrence associated with resistance to conventional chemotherapy. This study generated MBA MD231 3D cancer stem cells enriched spheroids in serum-free conditions and evaluated the influence of combined doxorubicin/thymoquinone-loaded cockle-shell-derived aragonite calcium carbonate nanoparticles. Single loaded drugs and free drugs were also evaluated. WST assay, sphere forming assay, ALDH activity analysis, Surface marker of CD44 and CD24 expression, apoptosis with Annexin V-PI kit, cell cycle analysis, morphological changes using a phase contrast light microscope, scanning electron microscopy, invasion assay and migration assay were carried out; The combination therapy showed enhanced apoptosis, reduction in ALDH activity and expression of CD44 and CD24 surface maker, reduction in cellular migration and invasion, inhibition of 3D sphere formation when compared to the free drugs and the single drug-loaded nanoparticle. Scanning electron microscopy showed poor spheroid formation, cell membrane blebbing, presence of cell shrinkage, distortion in the spheroid architecture; and the results from this study showed that combined drug-loaded cockle-shell-derived aragonite calcium carbonate nanoparticles can efficiently destroy the breast CSCs compared to single drug-loaded nanoparticle and a simple mixture of doxorubicin and thymoquinone.
29
Bates, N. R., M. I. Orchowska, R. Garley et J. T. Mathis. « Seasonal calcium carbonate undersaturation in shelf waters of the Western Arctic Ocean ; how biological processes exacerbate the impact of ocean acidification ». Biogeosciences Discussions 9, no 10 (16 octobre 2012) : 14255–90. http://dx.doi.org/10.5194/bgd-9-14255-2012.
Texte intégralRésumé :
Abstract. The Arctic Ocean accounts for only 4% of the global ocean area but it contributes significantly to the global carbon cycle. Recent observations of seawater carbonate chemistry in shelf waters of the Western Arctic from 2009 to 2011 indicate that extensive areas of the benthos are exposed to bottom waters that are seasonally undersaturated with respect to calcium carbonate (CaCO3) minerals, particularly aragonite. Our observations indicate seasonal reduction of saturation states (Ω) for calcite (Ωcalcite) and aragonite (Ωaragonite) in the subsurface in the Western Arctic by as much as 0.9 and 0.6, respectively. Such data indicates that bottom waters of the Western Arctic shelves are already potentially corrosive for biogenic and sedimentary CaCO3 for several months each year. Seasonal changes in Ω are imparted by a variety of factors such as phytoplankton photosynthesis, respiration/remineralization of organic matter and air-sea gas exchange of CO2 – combined these processes either increase or enhance Ω in surface and subsurface waters, respectively. These seasonal physical and biological processes also act to mitigate or enhance the impact of Anthropocene ocean acidification (OA) on Ω in surface and subsurface waters, respectively. Future monitoring of the Western Arctic shelves is warranted to assess the present and future impact on Ω values from ocean acidification and seasonal biological/physical processes on Arctic marine ecosystems.
30
Ridgwell, A., J. C. Hargreaves, N. R. Edwards, J. D. Annan, T. M. Lenton, R. Marsh, A. Yool et A. Watson. « Marine geochemical data assimilation in an efficient Earth System Model of global biogeochemical cycling ». Biogeosciences Discussions 3, no 4 (10 août 2006) : 1313–54. http://dx.doi.org/10.5194/bgd-3-1313-2006.
Texte intégralRésumé :
Abstract. We have extended the 3-D ocean based "Grid ENabled Integrated Earth system model'' (GENIE-1) to help understand the role of ocean biogeochemistry and marine sediments in the "long-term'' (~100 to 100 000 year) regulation of atmospheric CO2, and the importance of feedbacks between CO2 and climate. Here we describe the ocean carbon cycle, which is based around a simple single nutrient (phosphate) control on biological productivity. The addition of ocean-sediment interactions is presented elsewhere (Ridgwell and Hargreaves, 2006). We have calibrated the model parameters controlling ocean carbon cycling in GENIE-1 by assimilating 3-D observational datasets of phosphate and alkalinity using an ensemble Kalman filter method. The calibrated (mean) model predicts a global export production of particulate organic carbon (POC) of 8.9 PgC yr−1, and reproduces the main features of dissolved oxygen distributions in the ocean. For estimating biogenic calcium carbonate (CaCO3 production, we have devised a parameterization in which the CaCO3:POC export ratio is related directly to ambient saturation state. Calibrated global CaCO3 export production (1.2 PgC yr−1 is close to recent marine carbonate budget estimates. The GENIE-1 Earth system model is capable of simulating a wide variety of dissolved and isotopic species of relevance to the study of modern global biogeochemical cycles as well as past global environmental changes recorded in paleoceanographic proxies. Importantly, even with 12 active biogeochemical tracers in the ocean and including the calculation of feedbacks between atmospheric CO2 and climate, we achieve better than 1000 years per (2.4 GHz) CPU hour on a desktop PC. The GENIE-1 model thus provides a viable alternative to box and zonally-averaged models for studying global biogeochemical cycling over all but the very longest (>1 000 000 years) time-scales.
31
Sugiura, Yuki, Kunio Ishikawa, Kazuo Onuma et Yoji Makita. « PO4 adsorption on the calcite surface modulates calcite formation and crystal size ». American Mineralogist 104, no 10 (1 octobre 2019) : 1381–88. http://dx.doi.org/10.2138/am-2019-7015.
Texte intégralRésumé :
Abstract Calcium carbonate (CaCO3) and particularly its stable phase, calcite, is of great geological significance in the deep carbon cycle since CaCO3 from biomineralized shells and corals form sedimentary rocks. Calcite also attracts attention in medical science and pharmacy as a primary or intermediate component in biomaterials because it possesses excellent biocompatibility along with suitable physicochemical properties. Calcite blocks have already been used during surgical procedures as a bone substitute for reconstructing bone defects formed by diseases and injury. When producing CaCO3 biomaterials and bioceramics, in particular, in vivo control of the size and polymorphic nature of CaCO3 is required. In this study, we investigated the effects of PO4 on calcite formation during the phase conversion of calcium sulfate anhydrate (CaSO4, CSA), which is sometimes used as a starting material for bone substitutes because of its suitable setting ability. CSA powder was immersed in 2 mol/L Na2CO3 solution containing a range of PO4 concentrations (0–60 mmol/L) at 40 °C for 3 days. The treated samples were investigated by X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray fluorescence spectroscopy, and thermal analysis. In addition, the fine structures of the treated samples were observed by field-emission scanning electron microscopy, and the specific surface area was measured. We found that PO4, which is universally present in vivo, can modulate the calcite crystal size during calcite formation. A fluorescence study and calcite crystal growth experiments indicated that PO4 adsorbs tightly onto the surface of calcite, inhibiting crystal growth. In the presence of high PO4 concentrations, vaterite is formed along with calcite, and the appearance and stability of the CaCO3 polymorphs can be controlled by adjusting the PO4 concentration. These findings have implications for medical science and pharmacology, along with mineralogy and geochemistry.
32
Wang, Jie, Sijia Sun, Lei Pan, Zhuoqun Xu, Hao Ding et Wei Li. « Preparation and Properties of CaCO3-Supported Nano-TiO2 Composite with Improved Photocatalytic Performance ». Materials 12, no 20 (15 octobre 2019) : 3369. http://dx.doi.org/10.3390/ma12203369.
Texte intégralRésumé :
In order to improve the photocatalytic degradation efficiency of nano-TiO2, reduce its usage and realize recycling and reuse, CaCO3–TiO2 composite photocatalyst was prepared with calcium carbonate (CaCO3) and TiO2 in a grinding machine through the integration of grinding depolymerization, dispersion and particle composition. The photocatalytic degradation performance, recycling performance, structure and morphology of CaCO3–TiO2 were studied. The interaction mechanism between CaCO3 and TiO2 and the improvement mechanism for the photocatalytic performance of TiO2 were also discussed. The results show that under the UV light irradiation for 20 and 40 min, the degradation efficiency of methyl orange by the composite photocatalyst with 40% TiO2 (mass fraction) was 90% and 100%, respectively. This was similar to that of pure TiO2, and the performance of the composite photocatalyst was almost unchanged after five cycles. CaCO3–TiO2 is formed by the uniform loading of nano-TiO2 particles on the CaCO3 surface, and the nano-TiO2 particles are well dispersed. Due to the facts that the dispersion of nano-TiO2 is improved in the presence of CaCO3 and the charge transport capability is improved through the interfacial chemical bonds between CaCO3 and TiO2, the formation of this complex is an intrinsic mechanism to improve the photocatalytic efficiency of nano-TiO2 and reduce its usage in application processes.
33
SCHWANTES-CEZARIO, N., M. F. PORTO, G. F. B. SANDOVAL, G. F. N. NOGUEIRA, A. F. COUTO et B. M. TORALLES. « Effects of Bacillus subtilis biocementation on the mechanical properties of mortars ». Revista IBRACON de Estruturas e Materiais 12, no 1 (février 2019) : 31–38. http://dx.doi.org/10.1590/s1983-41952019000100005.
Texte intégralRésumé :
Abstract This study aims to evaluate the influence of B. subtilis AP91 spores addition on the mechanical properties of mortars. B. subtilis strain AP91, isolated from rice leaves of the needle variety, which has an early cycle of production, was used at the concentration of 105 spores/mL in mortars with cement-to-sand ratio of 1:3 (by weight) and water-to-cement ratio (w/c) of 0.63. These spores were added in two different ways: in the mixing water and by immersion in a solution containing bacterial spores. Scanning Electron Microscope (SEM) analysis showed crystals with calcium peaks on the EDS, which possibly indicates the presence of bioprecipitated calcium carbonate. The results obtained in the mechanical analysis showed that the bioprecipitation of CaCO3 by B. subtilis strain AP91 was satisfactory, particularly when the spores were added in the mixing water, increasing the compressive strength up to 31%. Thus, it was concluded that the addition of B. subtilis AP91 spores in the mixing water of cement mortars induced biocementation, which increased the compressive strength. This bioprecipitation of calcium carbonate may very well have other advantageous consequences, such as the closure of pores and cracks in cementitious materials that could improve durability properties, although more research is still needed on this matter.
34
Kim, Yumi, et Yul Roh. « Microbial Precipitation of Calcium Carbonate for Crack Healing and Stabilization of Sandy Soils ». Applied Sciences 14, no 4 (16 février 2024) : 1568. http://dx.doi.org/10.3390/app14041568.
Texte intégralRésumé :
Microbially induced calcium carbonate (CaCO3) precipitation (MICP) can improve the shear strength of soil via biocementation while reducing its porosity and hydraulic conductivity. The purpose of this study was to evaluate the effect of the addition of bacterial metabolites and montmorillonite on the crack healing and biocementation of sandy soil during the MICP process. Cracks were generated by drying wet soil samples in Petri dishes, after which they were sprayed with one of four treatments: deionized water, a cementation solution, bacteria mixed with the cementation solution, and bacterial metabolites mixed with the cementation solution. After five cycles of this spray treatment, the surface crack ratio was observed to decrease by about 71% when living cells were used and by about 80% when microbial metabolites were added. However, the crack reduction ratio was relatively low when treated with water (28%) and the cementation solution alone (48%). To investigate the effect of adding a phyllosilicate to improve the strength of sandy soil, MICP was induced in sand mixed with 0–30% montmorillonite (MMT). As a result, the soil strength increased with higher levels of MMT, indicating that MMT contributed to soil stabilization as a colloid for CaCO3 precipitation and via adhesion between sand grains. Therefore, for the crack healing and stabilization of sandy soil, the addition of bacterial metabolites and montmorillonite may enhance the effectiveness of the MICP process.
35
Ziegler, Andreas. « Immunocytochemical Localization of Na+,K+-ATPase in the Calcium-transporting Sternal Epithelium of the Terrestrial Isopod Porcellio scaber L. (Crustacea) ». Journal of Histochemistry & ; Cytochemistry 45, no 3 (mars 1997) : 437–46. http://dx.doi.org/10.1177/002215549704500311.
Texte intégralRésumé :
Terrestrial isopods store large amounts of calcium carbonate between the epithelium and the old cuticle of the first four anterior sternites before molt. During the formation of these sternal CaCO3 deposits, large amounts of calcium are transported across the anterior sternal epithelium from the base to the apical side of the integument, and in the reverse direction during resorption of the deposit. A monoclonal antibody against the avian α-subunit of Na+,K+-ATPase was used to localize Na+,K+-ATPase in the anterior and the posterior sternal epithelium of Porcellio scaber. Semithin cryosections 0.5 μm thick were used for immunofluorescence microscopy and ultrathin cryosections for immunogold electron microscopy. The Na+,K+-ATPase was localized in the basolateral plasma membrane of the posterior and anterior sternal epithelium. The apical plasma membrane, including cytoplasmic extensions into the newly secreted cuticle, was virtually devoid of the enzyme. This pattern of immunolocalization was not affected by the direction of transepithelial calcium transport associated with the deposition and resorption phases of the molt cycle. (J Histochem Cytochem 45:437–446, 1997)
36
Xiao, Peng, Hanlong Liu, Armin W. Stuedlein, T. Matthew Evans et Yang Xiao. « Effect of relative density and biocementation on cyclic response of calcareous sand ». Canadian Geotechnical Journal 56, no 12 (décembre 2019) : 1849–62. http://dx.doi.org/10.1139/cgj-2018-0573.
Texte intégralRésumé :
Microbial-induced calcium carbonate precipitation (MICP) represents a promising approach to improve the geotechnical engineering properties of soils through the precipitation of calcium carbonate (CaCO3) at soil particle contacts and soil particle surfaces. An extensive experimental study was undertaken to investigate the influence of initial relative density on the efficiency of the biocementation process, the reduction of liquefaction susceptibility, and the cyclic response in biocemented calcareous soils. For this purpose, stress-controlled undrained cyclic triaxial shear (CTS) tests were carried out on untreated and MICP-treated calcareous sand specimens for different initial relative densities and magnitudes of biocementation. Improvement in the cyclic response was quantified and compared in terms of excess pore pressure generation, evolution of axial strains, and the number of cycles to liquefaction. The cyclic experiments show that MICP treatment can change the liquefaction failure mechanism from flow failure to cyclic mobility and can significantly change the excess pore pressure generation response of initially loose specimens. Scanning electron microscope (SEM) images indicate the CaCO3 crystals alter the characteristics of the sand particles and confirm the physical change in soil fabric that impacts the dynamic behavior and liquefaction resistance of MICP-treated specimens. Furthermore, the effect of biocementation was contrasted against the effect of relative density alone, and MICP treatment was shown to exhibit greater efficiency in improving the cyclic resistance than densification.
37
Shutler, J. D., P. E. Land, C. W. Brown, H. S. Findlay, C. J. Donlon, M. Medland, R. Snooke et J. C. Blackford. « Coccolithophore surface distributions in the North Atlantic and their modulation of the air-sea flux of CO<sub>2</sub> ; from 10 years of satellite Earth observation data ». Biogeosciences 10, no 4 (23 avril 2013) : 2699–709. http://dx.doi.org/10.5194/bg-10-2699-2013.
Texte intégralRésumé :
Abstract. Coccolithophores are the primary oceanic phytoplankton responsible for the production of calcium carbonate (CaCO3). These climatically important plankton play a key role in the oceanic carbon cycle as a major contributor of carbon to the open ocean carbonate pump (~50%) and their calcification can affect the atmosphere-to-ocean (air-sea) uptake of carbon dioxide (CO2) through increasing the seawater partial pressure of CO2 (pCO2). Here we document variations in the areal extent of surface blooms of the globally important coccolithophore, Emiliania huxleyi, in the North Atlantic over a 10-year period (1998–2007), using Earth observation data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS). We calculate the annual mean sea surface areal coverage of E. huxleyi in the North Atlantic to be 474 000 ± 104 000 km2, which results in a net CaCO3 carbon (CaCO3-C) production of 0.14–1.71 Tg CaCO3-C per year. However, this surface coverage (and, thus, net production) can fluctuate inter-annually by −54/+8% about the mean value and is strongly correlated with the El Niño/Southern Oscillation (ENSO) climate oscillation index (r=0.75, p<0.02). Our analysis evaluates the spatial extent over which the E. huxleyi blooms in the North Atlantic can increase the pCO2 and, thus, decrease the localised air-sea flux of atmospheric CO2. In regions where the blooms are prevalent, the average reduction in the monthly air-sea CO2 flux can reach 55%. The maximum reduction of the monthly air-sea CO2 flux in the time series is 155%. This work suggests that the high variability, frequency and distribution of these calcifying plankton and their impact on pCO2 should be considered if we are to fully understand the variability of the North Atlantic air-to-sea flux of CO2. We estimate that these blooms can reduce the annual N. Atlantic net sink atmospheric CO2 by between 3–28%.
38
Gonçalves, Alex Augusto, et Marcelo Gonzalez Passos. « Restructured fish product from white croacker (Micropogonias furnieri) mince using microbial transglutaminas ». Brazilian Archives of Biology and Technology 53, no 4 (août 2010) : 987–95. http://dx.doi.org/10.1590/s1516-89132010000400030.
Texte intégralRésumé :
This study aimed at determining the influence of three concentrations of commercial transglutaminase enzyme in restructured fillet of minced fish from white croacker (Micropogonias furnieri), one of the four marine species with notability in Brazil. The restructured fillet developed had advantages when compared to traditional fillet, such as absence of spine and less flavour intensity (washes cycles). Washing process for white croacker mince was compared with five clarification agents: water (control), phosphoric acid (H3PO4), sodium chloride (NaCl), calcium carbonate (CaCO3) and sodium bicarbonate (NaHCO3). The higher quality product (whiteness) was obtained with calcium carbonate washes. Three concentrations (1.5, 1.0 and 0.5%) of microbial transglutaminase MGTase (Active TG-B %v/v and Active TG-BP %w/w) were compared, in order to produce fish restructured product (boneless fillet). The concentration of 1.5% (both enzymes), produced better results. The restructured products were compared by sensory analysis and showed better sensory parameters (appearance, odour, flavour and texture) samples treated with Active TG-B (solution form).
39
Gralik, Guilherme, Alessandra Thomsen, Cristian Moraes, Fabiano Raupp-Pereira et Dachamir Hotza. « Processing and characterization of CaTiO3 perovskite ceramics ». Processing and Application of Ceramics 8, no 2 (2014) : 53–57. http://dx.doi.org/10.2298/pac1402053g.
Texte intégralRésumé :
Calcium titanate (CaTiO3) ceramics with perovskite structure were produced by solid state reaction. Calcium carbonate (CaCO3) and titanium dioxide (TiO2) were mixed (in molar ratios 1/1 and 3/2), and the obtained mixtures were calcined at 1150 ?C in successive thermal cycles. The obtained samples were characterized by differential thermal analysis, thermogravimetry, X-ray diffraction, measurement of particle size distribution and linear thermal shrinkage. XRD results indicated that the samples have perovskite CaTiO3 structure with small amount of secondary CaO and TiO2 phases, and their phase composition depends on the heat treatment conditions. The measured values of electrical resistivity were within the characteristic range of insulating materials and approach values corresponding to semiconducting ceramics.
40
Shutler, J. D., P. E. Land, C. W. Brown, H. S. Findlay, C. J. Donlon, M. Medland, R. Snooke et J. C. Blackford. « Coccolithophore surface distributions in the North Atlantic and their modulation of the air-sea flux of CO<sub>2</sub> ; from 10 years of satellite Earth observation data ». Biogeosciences Discussions 9, no 5 (22 mai 2012) : 5823–48. http://dx.doi.org/10.5194/bgd-9-5823-2012.
Texte intégralRésumé :
Abstract. Coccolithophores are the primary oceanic phytoplankton responsible for the production of calcium carbonate (CaCO3). These climatically important plankton play a key role in the oceanic carbon cycle as a major contributor of carbon to the open ocean carbonate pump (~50%) and their formation can affect the atmosphere-to-ocean (air-sea) uptake of carbon dioxide (CO2) through increasing the seawater partial pressure of CO2 (pCO2). Here we document variations in the areal extent of surface blooms of the globally important coccolithophore, Emiliania huxleyi, in the North Atlantic over a 10-year period (1998–2007), using Earth observation data from the Sea-viewing Wide Field of view Sensor (SeaWiFS). We calculate the annual mean surface areal coverage of E. huxleyi in the North Atlantic to be 474 000 ± 119 000 km2 yr−1, which results in a net CaCO3 production of 0.62 ± 0.15 Tg CaCO3 carbon per year. However, this surface coverage and net production can fluctuate by −54/+81% about these mean values and are strongly correlated with the El Niño/Southern Oscillation (ENSO) climate oscillation index (r = 0.75, p < 0.02). Our analysis evaluates the spatial extent over which the E. huxleyi blooms in the North Atlantic can increase the pCO2 and thus decrease the localised sink of atmospheric CO2. In regions where the blooms are prevalent, the average reduction in the monthly CO2 sink can reach 12%. The maximum reduction of the monthly CO2 sink in the time series is 32%. This work suggests that the high variability, frequency and distribution of these calcifying plankton and their impact on pCO2 should be considered within modelling studies of the North Atlantic if we are to fully understand the variability of its air-to-sea CO2 flux.
41
Li, Xiaomin, Kemeng Luo, Jinqian Ren, Xiangrui Wang, Qian Mu et Wenhong Fan. « Characterisation of extracellular polymeric substances from different cyanobacterial species and their influence on biocalcification processes ». Environmental Chemistry 14, no 4 (2017) : 254. http://dx.doi.org/10.1071/en17068.
Texte intégralRésumé :
Environmental contextExtracellular polymeric substances provide a nucleation site for calcium carbonate and hence are important for bio-calcification processes, with implications for sediment formation and the global carbon cycle. We investigate the calcification potential of polymeric substances produced by five species of cyanobacteria. The results indicate that the protein content and alkaline functional groups of the extracellular polymeric substances may have a significant effect on cyanobacterial calcification. AbstractCyanobacterial calcification plays a crucial role in the formation of freshwater calcium carbonate precipitates, with cyanobacterial extracellular polymeric substances (EPSs) contributing significantly, partly by providing a nucleation site for calcium carbonate. Despite this, cyanobacterial EPS and their effect on calcification processes have not been completely characterised. In the present study, five cyanobacterial species were selected. First, EPS characteristics of these cyanobacterial species were examined, showing that proteins dominated both EPSs released in to solution (REPSs) and cell-surface bound (LEPSs). The major EPS functional groups included acidic groups, such as carboxyl groups, and highly alkaline groups, such as hydroxyl and amino groups. The calcification ability of different cyanobacterial species was found to vary dramatically. Solution pH increased during the calcification process, which was beneficial to the supersaturation of CaCO3, and could affect the calcification potential. Precipitation, however, was positively correlated with EPS protein content and the concentration of basic functional groups, such as amino or hydroxyl groups. These results suggest EPS protein content and alkaline functional groups may have a significant effect on cyanobacterial calcification. The results also provide a potential application in that EPS proteins of cyanobacteria may have beneficial positive applications in the removal of multivalent cations from wastewater.
42
Mo, Yixin, Songlin Yue, Qizhen Zhou et Xiao Liu. « Improvement and Soil Consistency of Sand–Clay Mixtures Treated with Enzymatic-Induced Carbonate Precipitation ». Materials 14, no 18 (7 septembre 2021) : 5140. http://dx.doi.org/10.3390/ma14185140.
Texte intégralRésumé :
Recently, microbially induced carbonate precipitation (MICP) has been studied as an alternative for the improvement of sand–clay mixtures. However, the cementing uniformity of MICP-treated sand–clay mixtures cannot be guaranteed. In this present study, enzymatic-induced carbonate precipitation (EICP) was used to deal with it. The ions used in kaolin clay was predicted to affect the production rate for calcium carbonate (CaCO3), which was studied using the calcification test. The solidification test was conducted using two different methods (the premixing method and the diffusion method). The permeability, unconfined compressive strength and the content of CaCO3 of treated samples were obtained to evaluate the solidification effect of the EICP method. Moreover, in EICP treatment, the particle aggregation decreased the liquid limit, but the addition of solution increased it. Therefore, there were contrary effects to the soil consistency. In this study, the two types of liquid limits of treated samples were measured with deionized water and 2M-NaCl brine, respectively. The results show that the Al2O3, NaCl and MgCl2 in the kaolin clay had a slight impact on the production rate for CaCO3, while FeCl3 significantly inhibited it. The EICP method can improve sand–clay mixtures and decrease their permeability. Different from MICP, the EICP method can guarantee the uniformity of treated samples. Moreover, the liquid limit of the sample treated with the premixing method decreased, while that of the sample treated with the diffusion method increased firstly and then decreased with the increasing treatment cycles. Different from the deionized water, the pore-fluid chemistry had a larger effect on the liquid limit with 2M-NaCl brine.
43
Zeebe, R. E. « LOSCAR : Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir Model ». Geoscientific Model Development Discussions 4, no 2 (29 juin 2011) : 1435–76. http://dx.doi.org/10.5194/gmdd-4-1435-2011.
Texte intégralRésumé :
Abstract. The LOSCAR model is designed to efficiently compute the partitioning of carbon between ocean, atmosphere, and sediments on time scales ranging from centuries to millions of years. While a variety of computationally inexpensive carbon cycle models are already available, many are missing a critical sediment component, which is indispensable for long-term integrations. One of LOSCAR's strengths is the coupling of ocean-atmosphere routines to a computationally efficient sediment module. This allows, for instance, adequate computation of CaCO3 dissolution, calcite compensation, and long-term carbon cycle fluxes, including weathering of carbonate and silicate rocks. The ocean component includes various biogeochemical tracers such as total carbon, alkalinity, phosphate, oxygen, and stable carbon isotopes. We have previously published applications of the model tackling future projections of ocean chemistry and weathering, pCO2 sensitivity to carbon cycle perturbations throughout the Cenozoic, and carbon/calcium cycling during the Paleocene-Eocene Thermal Maximum. The focus of the present contribution is the detailed description of the model including numerical architecture, processes and parameterizations, tuning, and examples of input and output. Typical CPU integration times of LOSCAR are of order seconds for several thousand model years on current standard desktop machines. The LOSCAR source code in C can be obtained from the author by sending a request to loscar.model@gmail.com.
44
Hastuti, Yuni Puji, Chandra Yudistira, Kukuh Nirmala, Wildan Nurusallam et Kurnia Faturochman. « Addition of CaCO3 to culture media at the salinity of 3 g/L for freshwater tambaqui growth ». Jurnal Akuakultur Indonesia 15, no 1 (3 février 2016) : 32–40. http://dx.doi.org/10.19027/jai.15.32-40.
Texte intégralRésumé :
ABSTRACT Increasing of freshwater tambaqui Colossoma macropomum demand makes the farmers increase the production of the consumption fish and seed. Acceleration of the production cycle can increase total production level, and reduce the level of osmotic work can be used to improve fish growth. This study aimed to analyze the effect of the addition of calcium carbonate (CaCO3) in the saline medium of 3 g/L on the growth of freshwater tambaqui juvenile. Tambaqui used has a body length of 1.93 ± 0.1 cm and weight of 0.26 ± 0.03 g. The experiment used 15 units of aquarium at size of 30×15×25 cm3 and filled with 9 L of saline water, then added lime CaCO3 according to treatment. The treatments were control (0 mg/L CaCO3), A (50 mg/L CaCO3), B (100 mg/L CaCO3), C (150 mg/L CaCO3), and D (200 mg/L CaCO3). The study was conducted for 30 days of maintenance. Fishes were fed on bloodworms ad libitum or provided three times a day. The results showed that survival, daily growth rate, and absolute length growth of the CaCO3 treatments significantly higher (P<0.05) that that of control. Furthermore, survival, daily growth rate, and absolute length growth among the CaCO3 treatments were the same. Thus, addition CaCO3 of 50 mg/L saline water of 3 g/L can be applied to increase culture performance of freshwater tambaqui. Keywords: freshwater tambaqui, CaCO3, salinity ABSTRAK Permintaan terhadap ikan bawal air tawar Colossoma macropomum yang semakin meningkat membuat pembudidaya menambah produksi ikan konsumsi dan benih. Percepatan siklus produksi dapat meningkatkan total produksi budidaya, dan energi dari optimasi kerja osmotik dapat dialokasikan untuk pertumbuhan. Penelitian ini bertujuan untuk menganalisis pengaruh penambahan kalsium karbonat (CaCO3) pada media bersalinitas terhadap pertumbuhan benih ikan bawal air tawar. Benih ikan bawal yang digunakan memiliki panjang 1,93±0,1 cm dengan bobot 0,26±0,03 g. Akuarium yang digunakan berukuran 30×15×25 cm3 sebanyak 15 unit dan diisi air bersalinitas 3 g/L sebanyak 9 L, kemudian ditambahkan kapur CaCO3 sesuai perlakuan. Dosis setiap perlakuan terdiri atas kontrol (0 mg/L CaCO3), A (50 mg/L CaCO3), B (100 mg/L CaCO3), C (150 mg/L CaCO3), dan D (200 mg/L CaCO3). Penelitian dilakukan selama 30 hari pemeliharaan dengan pemberian pakan cacing sutra secara ad libitum atau diberikan tiga kali sehari. Hasil penelitian menunjukkan bahwa derajat kelangsungan hidup, laju pertumbuhan harian, dan panjang mutlak pada perlakuan penambahan kapur CaCO3 lebih tinggi (P<0,05) daripada kontrol. Sementara itu, derajat kelangsungan hidup, laju pertumbuhan harian, dan panjang mutlak antarperlakuan penambahan kapur CaCO3 tidak berbeda. Dengan demikian, penambahan CaCO3 sebanyak 50 mg/L air dapat diterapkan untuk perbaikan performa budidaya ikan. Kata kunci: ikan bawal air tawar, CaCO3, salinitas
45
Bates, N. R., et J. T. Mathis. « The Arctic Ocean marine carbon cycle : evaluation of air-sea CO<sub>2</sub> ; exchanges, ocean acidification impacts and potential feedbacks ». Biogeosciences 6, no 11 (5 novembre 2009) : 2433–59. http://dx.doi.org/10.5194/bg-6-2433-2009.
Texte intégralRésumé :
Abstract. At present, although seasonal sea-ice cover mitigates atmosphere-ocean gas exchange, the Arctic Ocean takes up carbon dioxide (CO2) on the order of −66 to −199 Tg C year−1 (1012 g C), contributing 5–14% to the global balance of CO2 sinks and sources. Because of this, the Arctic Ocean has an important influence on the global carbon cycle, with the marine carbon cycle and atmosphere-ocean CO2 exchanges sensitive to Arctic Ocean and global climate change feedbacks. In the near-term, further sea-ice loss and increases in phytoplankton growth rates are expected to increase the uptake of CO2 by Arctic Ocean surface waters, although mitigated somewhat by surface warming in the Arctic. Thus, the capacity of the Arctic Ocean to uptake CO2 is expected to alter in response to environmental changes driven largely by climate. These changes are likely to continue to modify the physics, biogeochemistry, and ecology of the Arctic Ocean in ways that are not yet fully understood. In surface waters, sea-ice melt, river runoff, cooling and uptake of CO2 through air-sea gas exchange combine to decrease the calcium carbonate (CaCO3) mineral saturation states (Ω) of seawater while seasonal phytoplankton primary production (PP) mitigates this effect. Biological amplification of ocean acidification effects in subsurface waters, due to the remineralization of organic matter, is likely to reduce the ability of many species to produce CaCO3 shells or tests with profound implications for Arctic marine ecosystems
46
Lucas, J. M., et L. W. Knapp. « A physiological evaluation of carbon sources for calcification in the octocoral Leptogorgia virgulata (Lamarck). » Journal of Experimental Biology 200, no 20 (1 octobre 1997) : 2653–62. http://dx.doi.org/10.1242/jeb.200.20.2653.
Texte intégralRésumé :
The union of calcium cations with carbonate anions to form calcium carbonate (CaCO3) is a fundamentally important physiological process of many marine invertebrates, in particular the corals. In an effort to understand the sources and processes of carbon uptake and subsequent deposition as calcium carbonate, a series of studies of the incorporation of 14C-labeled compounds into spicules was undertaken using the soft coral Leptogorgia virgulata. It has been surmised for some time that dissolved inorganic carbon in sea water is used in the biomineralization process. Furthermore, it was suspected that metabolically generated CO2 is also available for calcification. As a means of testing these possible sources of carbon in spicule calcification, key enzymes or transport systems in each pathway were inhibited. First, the enzyme carbonic anhydrase was specifically inhibited using acetazolamide. Second, the active transport of bicarbonate was inhibited using DIDS (4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid). Third, CO2 generation resulting from glycolysis and the citric acid cycle was arrested using iodoacetic acid, which interferes specifically with the enzyme glyceraldehyde-3-phosphate dehydrogenase. The results indicate that dissolved CO2 is the largest source of carbon used in the formation of calcitic sclerites, followed by HCO3- from dissolved inorganic carbon. In L. virgulata, the dissolved inorganic carbon is responsible for approximately 67% of the carbon in the sclerites. The other 33% comes from CO2 generated by glycolysis. Two important conclusions can be drawn from this work. First, carbon for spiculogenesis comes not only from dissolved inorganic carbon in the environment but also from metabolically produced carbon dioxide. While the latter has been theorized, it has never before been demonstrated in octocorals. Second, regardless of the carbon source, the enzyme carbonic anhydrase plays a pivotal role in the physiology of spicule formation in Leptogorgia virgulata.
47
Song, Chenpeng, et Derek Elsworth. « Microbially Induced Calcium Carbonate Plugging for Enhanced Oil Recovery ». Geofluids 2020 (2 juillet 2020) : 1–10. http://dx.doi.org/10.1155/2020/5921789.
Texte intégralRésumé :
Plugging high-permeability zones within oil reservoirs is a straightforward approach to enhance oil recovery by diverting waterflooding fluids through the lower-permeability oil-saturated zones and thereby increase hydrocarbon displacement by improvements in sweep efficiency. Sporosarcina pasteurii (ATCC 11859) is a nitrogen-circulating bacterium capable of precipitating calcium carbonate given a calcium ion source and urea. This microbially induced carbonate precipitation (MICP) is able to infill the pore spaces of the porous medium and thus can act as a potential microbial plugging agent for enhancing sweep efficiency. The following explores the microscopic characteristics of MICP-plugging and its effectiveness in permeability reduction. We fabricate artificial rock cores composed of Ottawa sand with three separate grain-size fractions which represent large (40/60 mesh sand), intermediate (60/80 mesh sand), and small (80/120 mesh sand) pore sizes. The results indicate a significant reduction in permeability after only short periods of MICP treatment. Specifically, after eight cycles of microbial treatment (about four days), the permeability for the artificial cores representing large, intermediate, and small pore size maximally drop to 47%, 32%, and 16% of individual initial permeabilities. X-ray diffraction (XRD) indicates that most of the generated calcium carbonate crystals occur as vaterite with only a small amount of calcite. Imaging by SEM indicates that the pore wall is coated by a calcium carbonate film with crystals of vaterite and calcite scattered on the pore wall and acting to effectively plug the pore space. The distribution pattern and morphology of microbially mediated CaCO3 indicate that MICP has a higher efficiency in plugging pores compared with extracellular polymeric substances (EPSs) which are currently the primary microbial plugging agent used to enhance sweep efficiency.
48
Moforis, L., S. Kostopoulou, G. Panagopoulos, I. Pyliotis, M. Triantaphylou, E. Manoutsoglou et A. Zelilidis. « Sedimentation processes and palaeographic evolution of Makrilia Pliocene deposits, SE Crete. » Bulletin of the Geological Society of Greece 47, no 1 (21 décembre 2016) : 216. http://dx.doi.org/10.12681/bgsg.10929.
Texte intégralRésumé :
Detailed sedimentological analysis in Makrylia cross-section deposits showed at least five coarsening-upward cycles that were developed in a shelf environment. The main lithology is sandy silt and the sediments were transported as homogenous suspension in a low energy environment that deposited in a shallow water basin. The content of calcium carbonate (CaCO3) is low and tends to increase to the coarsegrained clasts. Organic carbon (TOC) measurements showed the presence of many samples with high content in TOC suggesting potential hydrocarbon source rocks. There is mostly a negative correlation between CaCO3 and TOC introducing generally anoxic conditions. Biostratigraphic analysis showed that the studied deposits are of Pliocene age that were precipitated in alternating conditions of oxic- anoxic events. According to the above results and taking into account previous results from the surrounding sediments it seems that the studied deposits accumulated in a shallow, low energy, intra-mountain basin at the margins of the main Ierapetra basin.
49
Daniels, Chris J., Alex J. Poulton, William M. Balch, Emilio Marañón, Tim Adey, Bruce C. Bowler, Pedro Cermeño et al. « A global compilation of coccolithophore calcification rates ». Earth System Science Data 10, no 4 (16 octobre 2018) : 1859–76. http://dx.doi.org/10.5194/essd-10-1859-2018.
Texte intégralRésumé :
Abstract. The biological production of calcium carbonate (CaCO3), a process termed calcification, is a key term in the marine carbon cycle. A major planktonic group responsible for such pelagic CaCO3 production (CP) is the coccolithophores, single-celled haptophytes that inhabit the euphotic zone of the ocean. Satellite-based estimates of areal CP are limited to surface waters and open-ocean areas, with current algorithms utilising the unique optical properties of the cosmopolitan bloom-forming species Emiliania huxleyi, whereas little understanding of deep-water ecology, optical properties or environmental responses by species other than E. huxleyi is currently available to parameterise algorithms or models. To aid future areal estimations and validate future modelling efforts we have constructed a database of 2765 CP measurements, the majority of which were measured using 12 to 24 h incorporation of radioactive carbon (14C) into acid-labile inorganic carbon (CaCO3). We present data collated from over 30 studies covering the period from 1991 to 2015, sampling the Atlantic, Pacific, Indian, Arctic and Southern oceans. Globally, CP in surface waters ( < 20 m) ranged from 0.01 to 8398 µmol C m−3 d−1 (with a geometric mean of 16.1 µmol C m−3 d−1). An integral value for the upper euphotic zone (herein surface to the depth of 1 % surface irradiance) ranged from < 0.1 to 6 mmol C m−2 d−1 (geometric mean 1.19 mmol C m−2 d−1). The full database is available for download from PANGAEA at https://doi.org/10.1594/PANGAEA.888182.
50
Nikolaeva, Larisa, Eleonora Zainullina et Gulshat Safina. « CLOSED-CYCLE TECHNOLOGY FOR OBTAINING CONSTRUCTION GYPSUM FROM WASTE ENERGY AND FLUE GASES OF THERMAL POWER PLANTS ». Problems of risk management in the technosphere 2024, no 1 (26 avril 2024) : 125–33. http://dx.doi.org/10.61260/1998-8990-2024-1-125-133.
Texte intégralRésumé :
A closed-cycle technology for building gypsum producing using energy waste and flue gases of thermal power plants has been developed. The technology is based on an absorption method for purifying gas emissions from industrial enterprises from sulfur dioxide SO2 using a suspension of carbonate sludge and obtaining a finished product – gypsum dihydrate. The commercial gypsum is obtained by using a suspension of carbonate sludge as a reagent. The suspension is formed at the stage of preliminary purification of natural water during coagulation and liming. Coagulation is carried out with ferrous sulfate heptate FeSO4×7H2O, liming – with a saturated solution of lime milk Ca(OH)2. As a result of combining the two processes, a suspension of a certain chemical composition is formed. The chemical composition of the sludge and its technological characteristics are presented. The main substance in the chemical composition is calcium carbonate CaCO3, which allows using a sludge suspension in the chemical reaction of the interaction of flue gases from thermal power plants with the formation of building gypsum. An absorber with a fluidized nozzle has been selected and designed to purify gas emissions from wet suspensions and produce commercial dihydrate gypsum. Hollow or solid hydrophobic polyethylene balls were selected as nozzles to reduce the adhesion of sludge suspension particles to their surface. A technological scheme is presented for purifying flue gases from sulfur dioxide to obtain the finished product – building gypsum. The scheme includes the proposed adsorber, sludge suspension tank, hydrocyclone and filter press. The cost of the resulting commercial building gypsum was calculated, which amounted to 15 rub./year, the payback period was 3,5 years. The prevented environmental harm from soil and land degradation from the introduction of this technology at thermal power plants was calculated by reducing the emission of sulfur dioxide into the air, which amounted to about 1 mil. rub./year.