Articles de revues : « Biogenic calcium carbonate »

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Berg, B. L., J. Ronholm, D. M. Applin, P. Mann, M. Izawa, E. A. Cloutis et L. G. Whyte. « Spectral features of biogenic calcium carbonates and implications for astrobiology ». International Journal of Astrobiology 13, n^o 4 (10 septembre 2014) : 353–65. http://dx.doi.org/10.1017/s1473550414000366.

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AbstractThe ability to discriminate biogenic from abiogenic calcium carbonate (CaCO3) would be useful in the search for extant or extinct life, since CaCO3can be produced by both biotic and abiotic processes on Earth. Bioprecipitated CaCO3material was produced during the growth of heterotrophic microbial isolates on medium enriched with calcium acetate or calcium citrate. These biologically produced CaCO3, along with natural and synthetic non-biologically produced CaCO3samples, were analysed by reflectance spectroscopy (0.35–2.5 μm), Raman spectroscopy (532 and 785 nm), and laser-induced fluorescence spectroscopy (365 and 405 nm excitation). Optimal instruments for the discrimination of biogenic from abiogenic CaCO3were determined to be reflectance spectroscopy, and laser-induced fluorescence spectroscopy. Multiple absorption features in the visible light region occurred in reflectance spectra for most biogenic CaCO3samples, which are likely due to organic pigments. Multiple fluorescence peaks occurred in emission spectra (405 nm excitation) of biogenic CaCO3samples, which also are best attributed to the presence of organic compounds; however, further analyses must be performed in order to better determine the cause of these features to establish criteria for confirming the origin of a given CaCO3sample. Raman spectroscopy was not useful for discrimination since any potential Raman peaks in spectra of biogenic carbonates collected by both the 532 and 785 nm lasers were overwhelmed by fluorescence. However, this also suggests that biogenic carbonates may be identified by the presence of this organic-associated fluorescence. No reliable spectroscopic differences in terms of parameters such as positions or widths of carbonate-associated absorption bands were found between the biogenic and abiogenic carbonate samples. These results indicate that the presence or absence of organic matter intimately associated with carbonate minerals is the only potentially useful spectral discriminator for the techniques that were examined, and that multiple spectroscopic techniques are capable of detecting the presence of associated organic materials. However, the presence or absence of intimately associated organic matter is not, in itself, an indicator of biogenicity.

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Rocha, Katari P., Santiago Botasini et Eduardo Méndez. « Physicochemical characterization of biogenic calcium carbonate ». MRS Advances 3, n^o 61 (2018) : 3569–74. http://dx.doi.org/10.1557/adv.2018.528.

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ABSTRACTBiogenic minerals are widely studied materials for their particular properties derived from their hierarchical structure, using building blocks with sizes spanning several orders of magnitude. These special features can be assessed with different analytical tools, and it is important to know their capabilities and limitations. In order to determine the hierarchical structure of the shells, the nacre and prismatic layers of two marine animals were characterized by infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. Based on these assessments, we found that the combination of these three techniques is useful to describe each structure level, and to explain some of the unique properties observed in these natural materials.

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Gong, Y. U. T., C. E. Killian, I. C. Olson, N. P. Appathurai, A. L. Amasino, M. C. Martin, L. J. Holt, F. H. Wilt et P. U. P. A. Gilbert. « Phase transitions in biogenic amorphous calcium carbonate ». Proceedings of the National Academy of Sciences 109, n^o 16 (4 avril 2012) : 6088–93. http://dx.doi.org/10.1073/pnas.1118085109.

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Kroisová, Dora, et Štěpánka Dvořáčková. « Biogenic Nanoparticles of Calcium Carbonate - Preparation and Behaviour ». Materials Science Forum 994 (mai 2020) : 197–204. http://dx.doi.org/10.4028/www.scientific.net/msf.994.197.

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Calcium carbonate is one of the most widespread natural material. Biogenic calcium carbonate nanoparticles are biocompatible. Currently, they are of great interest for their possible applications, especially in medicine. The aim of this introductory experimental study is to present a simple preparation of biogenic nanoparticles of calcium carbonate from natural resources with a subsequent specific behaviour of nanoparticles in aquatic environment. Different type of shells were used for the preparation of nanoparticles. All structures were burned at 850°C and then grounded to powder. The obtained powders were left in normal laboratory environment for 2 weeks and then placed in beakers with distilled water. Subsequently, two homogenization routes were used - stirring at 1000 rpm for 5 minutes and ultrasonic stirring for 5 minutes. One part of the particles was separated at the bottom of the beaker, but small formations started to create a fractal structure on the surface of water. These formations gradually increased. Crystalline interconnected structures built up with nanoparticles were confirmed by a subsequent analysis by a scanning electron microscope. EDX analysis confirmed the presence of calcium carbonate.

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Škundrić, Tamara, Dejan Zagorac, Aleksandra Zarubica et Branko Matović. « Theoretical investigation of mollusk shells : Energy landscape exploration of CaCo3 polymorphs and element substitution : A short review ». Advanced Technologies 10, n^o 1 (2021) : 73–80. http://dx.doi.org/10.5937/savteh2101073s.

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Due to the remarkable properties achieved under ambient conditions and with quite limited components, mollusk shells are very appealing natural bio-composites used as inspiration for new advanced materials. Calcium carbonate which is among the most widespread biominerals is used by mollusks as a building material that constitutes 95-99% of their shells. Within the investigation of calcium carbonate polymorphs present in the shells, diverse theoretical and experimental studies were performed, however, further research of these crystalline forms is required. There are very little researches on the energy landscapes of biogenic calcium carbonate which can provide us information about the free energies of already known as well as newly discovered plausible structures. To investigate the structural, mechanical, elastic, or vibrational properties and to predict new possible structures of biogenic calcium carbonate, different calculation methods could be employed. Some of these studies are presented and discussed in this paper.

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Sadekov, Aleksey, Nicholas S. Lloyd, Sambuddha Misra, Julie Trotter, Juan D'Olivo et Malcolm McCulloch. « Accurate and precise microscale measurements of boron isotope ratios in calcium carbonates using laser ablation multicollector-ICPMS ». Journal of Analytical Atomic Spectrometry 34, n^o 3 (2019) : 550–60. http://dx.doi.org/10.1039/c8ja00444g.

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The boron isotope compositions (δ¹¹B) of biogenic carbonates have proven to be an invaluable tool for investigating changes in ocean carbonate chemistry, especially the impacts of declining seawater pH due to rising levels of atmospheric CO₂.

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Ichikawa, Kazuhiko. « Buffering Dissociation/Formation Reaction of Biogenic Calcium Carbonate ». Chemistry - A European Journal 13, n^o 36 (17 décembre 2007) : 10176–81. http://dx.doi.org/10.1002/chem.200700166.

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Sutton, Jill N., Yi-Wei Liu, Justin B. Ries, Maxence Guillermic, Emmanuel Ponzevera et Robert A. Eagle. « δ11B as monitor of calcification site pH in divergent marine calcifying organisms ». Biogeosciences 15, n^o 5 (8 mars 2018) : 1447–67. http://dx.doi.org/10.5194/bg-15-1447-2018.

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Abstract. The boron isotope composition (δ11B) of marine biogenic carbonates has been predominantly studied as a proxy for monitoring past changes in seawater pH and carbonate chemistry. However, a number of assumptions regarding chemical kinetics and thermodynamic isotope exchange reactions are required to derive seawater pH from δ11B biogenic carbonates. It is also probable that δ11B of biogenic carbonate reflects seawater pH at the organism's site of calcification, which may or may not reflect seawater pH. Here, we report the development of methodology for measuring the δ11B of biogenic carbonate samples at the multi-collector inductively coupled mass spectrometry facility at Ifremer (Plouzané, France) and the evaluation of δ11BCaCO3 in a diverse range of marine calcifying organisms reared for 60 days in isothermal seawater (25 °C) equilibrated with an atmospheric pCO2 of ca. 409 µatm. Average δ11BCaCO3 composition for all species evaluated in this study range from 16.27 to 35.09 ‰, including, in decreasing order, coralline red alga Neogoniolithion sp. (35.89 ± 3.71 ‰), temperate coral Oculina arbuscula (24.12 ± 0.19 ‰), serpulid worm Hydroides crucigera (19.26 ± 0.16 ‰), tropical urchin Eucidaris tribuloides (18.71 ± 0.26 ‰), temperate urchin Arbacia punctulata (16.28 ± 0.86 ‰), and temperate oyster Crassostrea virginica (16.03 ‰). These results are discussed in the context of each species' proposed mechanism of biocalcification and other factors that could influence skeletal and shell δ11B, including calcifying site pH, the proposed direct incorporation of isotopically enriched boric acid (instead of borate) into biogenic calcium carbonate, and differences in shell/skeleton polymorph mineralogy. We conclude that the large inter-species variability in δ11BCaCO3 (ca. 20 ‰) and significant discrepancies between measured δ11BCaCO3 and δ11BCaCO3 expected from established relationships between abiogenic δ11BCaCO3 and seawater pH arise primarily from fundamental differences in calcifying site pH amongst the different species. These results highlight the potential utility of δ11B as a proxy of calcifying site pH for a wide range of calcifying taxa and underscore the importance of using species-specific seawater-pH–δ11BCaCO3 calibrations when reconstructing seawater pH from δ11B of biogenic carbonates.

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Marin, Frédéric, Nathalie Le Roy, Benjamin Marie, Paula Ramos-Silva, Irina Bundeleva, Nathalie Guichard et Françoise Immel. « Metazoan calcium carbonate biomineralizations : macroevolutionary trends – challenges for the coming decade ». Bulletin de la Société Géologique de France 185, n^o 4 (1 avril 2014) : 217–32. http://dx.doi.org/10.2113/gssgfbull.185.4.217.

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Abstract Calcium carbonate-based biominerals, also referred as biocalcifications, are the most abundant biogenic mineralized products at the surface of the Earth. In this paper, we summarize general concepts on biocalcifications and we sketch macro-evolutionary trends throughout the history of the Earth, from Archean to Phanerozoic times. Then, we expose five fundamental issues that represent key-challenges in biocalcification researches for the coming decade: the first one concerns the comprehension of the micro- and nano-structure of calcium carbonate biominerals from a mineral viewpoint, while the second one deals with the understanding of the dynamic process of their fabrication. The third one treats the subtle interplay between organics and the mineral phase. The fourth issue focuses on an environmental challenge related to ocean acidification (OA); at last, the diagenetic processes that affect biogenic calcium carbonate mineral constitute the fifth issue.

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Ellison, Joanna C., Paul Han et Trevor W. Lewis. « Carbonate Beach Sand of Abaiang Atoll, Kiribati : Geochemistry, Biogenic Sources, and Properties ». Atoll Research Bulletin, n^o 621 (20 mars 2019) : 1–21. http://dx.doi.org/10.5479/si.0077-5630.621.

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Sandy beaches are critical resources for low-lying Pacific atoll communities, providing protection during storms, and land area for many coastal villages. Information on the nature of atoll beach sediment, its geochemistry and composition, can help to establish priorities to effectively protect the sources of Pacific island beach sediment. To understand sand sources, this study evaluated its physical characteristics including grain-size, geochemistry and composition, from windward and leeward beach profiles around Abaiang Atoll, Kiribati. Beach sand was >99% carbonate, averaging 37% coral fragments, 30% mollusc shells, 12% foraminifera, and 20% calcareous algae. Significant differences were found between reef and lagoonal sites in proportions of coral and mollusc fragments and foraminifera tests, with lagoon beaches having higher mollusc and coral proportions and lower foraminifera relative to reef beaches. This is attributed to high foraminiferal productivity offshore of reef beaches, and taphonomic durability of coral fragments in longshore drift into the lagoon. Mean sediment diameter increased from the upper to lower beaches at all sites, but fine sediment was lacking, attributed to its dissolution by rainfall and groundwater outflow. Geochemical analysis showed a mean of 84% Ca-Mg carbonates, of which 80% was calcium carbonate. There was no significant difference in the mean calcium percentage or calcium carbonate composition of the sediment between lagoon and reef beach sediment sources. Magnesium and magnesium carbonate content were significantly higher at reef sites relative to lagoon sites, attributed to higher proportions of foraminifera. Sediment-producing near shore habitats are critical to village protection through provision of beach sand, and this study shows the need to better conserve and manage coral reefs and habitats such as lagoon seagrass beds, to ensure continued atoll beach sand supply.

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Fernández-Arias, Mónica, Iago Álvarez-Olcina, Pablo Malvido-Fresnillo, José Antonio Vázquez, Mohamed Boutinguiza, Rafael Comesaña et Juan Pou. « Biogenic Calcium Phosphate from Fish Discards and By-Products ». Applied Sciences 11, n^o 8 (9 avril 2021) : 3387. http://dx.doi.org/10.3390/app11083387.

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Every year, millions of tons of fish waste are generated from fishing activities, and a similar amount is discarded and returned to the sea as unwanted catches. This material can be used as a biological source for many potential new added-value products, such asobtaining hyaluronic acid from fish eyeballs or extracting collagen from fish skin, but there are not many utilities for fish bones yet. This work tackles the transformation of fish discards into calcium phosphates. Discards from scorpionfish (Scorpaena scrofa) and Atlantic horse mackerel (Trachurus trachurus), as well as by-products generated from aquaculture activities (heads and trimmings frames) of salmon (Salmon salar), were used to obtain calcium phosphate. Biphasic carbonated hydroxyapatite (HA) /beta-tricalcium phosphate (TCP) material was obtained. The biphasic HA-TCP material has a promising range of applications in the biomedical field based on its similarity to calcium phosphates found in human bones in terms of crystallite size and carbonate content. The presence of Na, Mg, Sr, and K ions in the HA-TCP material is very beneficial, since they contribute to bone metabolism and cell adhesion.

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Cestari, Francesca, Francesca Agostinacchio, Anna Galotta, Giovanni Chemello, Antonella Motta et Vincenzo M. Sglavo. « Nano-Hydroxyapatite Derived from Biogenic and Bioinspired Calcium Carbonates : Synthesis and In Vitro Bioactivity ». Nanomaterials 11, n^o 2 (20 janvier 2021) : 264. http://dx.doi.org/10.3390/nano11020264.

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Biogenic calcium carbonates naturally contain ions that can be beneficial for bone regeneration and therefore are attractive resources for the production of bioactive calcium phosphates. In the present work, cuttlefish bones, mussel shells, chicken eggshells and bioinspired amorphous calcium carbonate were used to synthesize hydroxyapatite nano-powders which were consolidated into cylindrical pellets by uniaxial pressing and sintering 800–1100 °C. Mineralogical, structural and chemical composition were studied by SEM, XRD, inductively coupled plasma/optical emission spectroscopy (ICP/OES). The results show that the phase composition of the sintered materials depends on the Ca/P molar ratio and on the specific CaCO3 source, very likely associated with the presence of some doping elements like Mg2+ in eggshell and Sr2+ in cuttlebone. Different CaCO3 sources also resulted in variable densification and sintering temperature. Preliminary in vitro tests were carried out (by the LDH assay) and they did not reveal any cytotoxic effects, while good cell adhesion and proliferation was observed at day 1, 3 and 5 after seeding through confocal microscopy. Among the different tested materials, those derived from eggshells and sintered at 900 °C promoted the best cell adhesion pattern, while those from cuttlebone and amorphous calcium carbonate showed round-shaped cells and poorer cell-to-cell interconnection.

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Dutta, Abhishek, Simona Fermani, Srinivasan Arjun Tekalur, Abigail Vanderberg et Giuseppe Falini. « Calcium phosphate scaffold from biogenic calcium carbonate by fast ambient condition reactions ». Journal of Crystal Growth 336, n^o 1 (décembre 2011) : 50–55. http://dx.doi.org/10.1016/j.jcrysgro.2011.09.013.

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Liu, Renlu, Shanshan Huang, Xiaowen Zhang, Yongsheng Song, Genhe He, Zaifeng Wang et Bin Lian. « Bio-mineralisation, characterization, and stability of calcium carbonate containing organic matter ». RSC Advances 11, n^o 24 (2021) : 14415–25. http://dx.doi.org/10.1039/d1ra00615k.

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The amorphous calcium carbonate (ACC) or polycrystalline vaterite, which has long-term water stability and thermal stability, can be induced by bacteria. These biogenic CaCO₃ are organo-mineral complexes.

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Hargis, Craig W., Irvin A. Chen, Martin Devenney, Miguel J. Fernandez, Ryan J. Gilliam et Ryan P. Thatcher. « Calcium Carbonate Cement : A Carbon Capture, Utilization, and Storage (CCUS) Technique ». Materials 14, n^o 11 (21 mai 2021) : 2709. http://dx.doi.org/10.3390/ma14112709.

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A novel calcium carbonate cement system that mimics the naturally occurring mineralization process of carbon dioxide to biogenic or geologic calcium carbonate deposits was developed utilizing carbon dioxide-containing flue gas and high-calcium industrial solid waste as raw materials. The calcium carbonate cement reaction is based on the polymorphic transformation from metastable vaterite to aragonite and can achieve >40 MPa compressive strength. Due to its unique properties, the calcium carbonate cement is well suited for building materials applications with controlled factory manufacturing processes that can take advantage of its rapid curing at elevated temperatures and lower density for competitive advantages. Examples of suitable applications are lightweight fiber cement board and aerated concrete. The new cement system described is an environmentally sustainable alternative cement that can be carbon negative, meaning more carbon dioxide is captured during its manufacture than is emitted.

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Liu, Renlu, et Bin Lian. « Immobilisation of Cd(II) on biogenic and abiotic calcium carbonate ». Journal of Hazardous Materials 378 (octobre 2019) : 120707. http://dx.doi.org/10.1016/j.jhazmat.2019.05.100.

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Hamilton, Stephen K., Denise A. Bruesewitz, Geoffrey P. Horst, David B. Weed et Orlando Sarnelle. « Biogenic calcite–phosphorus precipitation as a negative feedback to lake eutrophication ». Canadian Journal of Fisheries and Aquatic Sciences 66, n^o 2 (février 2009) : 343–50. http://dx.doi.org/10.1139/f09-003.

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Lakes in carbonate-rich watersheds commonly precipitate calcium carbonate as calcite, and this is accelerated by photosynthetic uptake of carbon dioxide. Co-precipitation of phosphate with calcite is one reason that algal growth in such lakes tends to be strongly phosphorus (P) limited. The extent to which calcite precipitation can be a sink for added P, and thus act as a potential negative feedback to eutrophication, was demonstrated using large enclosures within a Michigan lake. Nitrogen and P were added over 45 days in the summer to produce mesotrophic and eutrophic conditions. Algal biomass and production increased markedly with the nutrient additions, elevating the pH (9–10) and greatly increasing calcite precipitation, reducing concentrations of calcium and alkalinity by up to 60%. Sediment traps indicated that calcite sedimentation was a major sink for added P. By the end of the experiment, only about half of the added P remained in the water column. Major ion concentrations in a larger set of Michigan lakes showed calcite precipitation to be widespread, reflecting the abundant carbonate minerals in this glacial region.

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Ganendra, Giovanni, Willem De Muynck, Adrian Ho, Eleni Charalampous Arvaniti, Baharak Hosseinkhani, Jose Angel Ramos, Hubert Rahier et Nico Boon. « Formate Oxidation-Driven Calcium Carbonate Precipitation by Methylocystis parvus OBBP ». Applied and Environmental Microbiology 80, n^o 15 (16 mai 2014) : 4659–67. http://dx.doi.org/10.1128/aem.01349-14.

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ABSTRACTMicrobially induced carbonate precipitation (MICP) applied in the construction industry poses several disadvantages such as ammonia release to the air and nitric acid production. An alternative MICP from calcium formate byMethylocystis parvusOBBP is presented here to overcome these disadvantages. To induce calcium carbonate precipitation,M. parvuswas incubated at different calcium formate concentrations and starting culture densities. Up to 91.4% ± 1.6% of the initial calcium was precipitated in the methane-amended cultures compared to 35.1% ± 11.9% when methane was not added. Because the bacteria could only utilize methane for growth, higher culture densities and subsequently calcium removals were exhibited in the cultures when methane was added. A higher calcium carbonate precipitate yield was obtained when higher culture densities were used but not necessarily when more calcium formate was added. This was mainly due to salt inhibition of the bacterial activity at a high calcium formate concentration. A maximum 0.67 ± 0.03 g of CaCO3g of Ca(CHOOH)2−1calcium carbonate precipitate yield was obtained when a culture of 109cells ml−1and 5 g of calcium formate liter−1were used. Compared to the current strategy employing biogenic urea degradation as the basis for MICP, our approach presents significant improvements in the environmental sustainability of the application in the construction industry.

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Radha, A. V., T. Z. Forbes, C. E. Killian, P. U. P. A. Gilbert et A. Navrotsky. « Transformation and crystallization energetics of synthetic and biogenic amorphous calcium carbonate ». Proceedings of the National Academy of Sciences 107, n^o 38 (1 septembre 2010) : 16438–43. http://dx.doi.org/10.1073/pnas.1009959107.

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Wrede, Christoph, Sebastian Kokoschka, Anne Dreier, Christina Heller, Joachim Reitner et Michael Hoppert. « Deposition of Biogenic Iron Minerals in a Methane Oxidizing Microbial Mat ». Archaea 2013 (2013) : 1–8. http://dx.doi.org/10.1155/2013/102972.

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The syntrophic community between anaerobic methanotrophic archaea and sulfate reducing bacteria forms thick, black layers within multi-layered microbial mats in chimney-like carbonate concretions of methane seeps located in the Black Sea Crimean shelf. The microbial consortium conducts anaerobic oxidation of methane, which leads to the formation of mainly two biomineral by-products, calcium carbonates and iron sulfides, building up these chimneys. Iron sulfides are generated by the microbial reduction of oxidized sulfur compounds in the microbial mats. Here we show that sulfate reducing bacteria deposit biogenic iron sulfides extra- and intracellularly, the latter in magnetosome-like chains. These chains appear to be stable after cell lysis and tend to attach to cell debris within the microbial mat. The particles may be important nuclei for larger iron sulfide mineral aggregates.

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Sharma, Shiv K., S. Michael Angel, Manash Ghosh, Hugh W. Hubble et Paul G. Lucey. « Remote Pulsed Laser Raman Spectroscopy System for Mineral Analysis on Planetary Surfaces to 66 Meters ». Applied Spectroscopy 56, n^o 6 (juin 2002) : 699–705. http://dx.doi.org/10.1366/000370202760077630.

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There is a need for an instrument that can be used for remote in situ identification of biogenic and a-biogenic minerals, various types of ices, and organic and inorganic materials on planetary surfaces. In this paper, we explore the use of remote pulsed laser Raman spectroscopy for mineral analysis at distances from 10 to 66 m on planetary surfaces. We have constructed a remote Raman system utilizing a small pulsed Nd:YAG laser and a 5-in. telescope coupled to a spectrograph with an optical fiber. The performance of our system is demonstrated by presenting spectra of benzene and marble (calcium carbonate) while varying the integration time (i.e., number of laser shots), as well as single laser shot spectra of marble while decreasing laser power. Finally, Raman spectra of representatives of several different mineral groups are presented, including hydrated substances, carbonates, silicates (e.g., olivine, pyroxene, feldspars, etc.), water, and ice.

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Petropoulos, A., A. Androni, T. Ntamkarelou et Ch Anagnostou. « Carbonate and organic carbon content in the recent sediments of Elefsis bay as indicators for the paleoenviromental evolution of the system. » Bulletin of the Geological Society of Greece 47, n^o 3 (21 décembre 2016) : 1562. http://dx.doi.org/10.12681/bgsg.10995.

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During the Holocene period Elefsis bay acted as a semi-enclosed system obstructing water circulation. In some areas, sampling has revealed the problems of anoxia that prevails in the bay, which has been worse during the summer months. Analyses undertaken in a core from the bay of Elefsis showed notable changes in carbonate and organic material, which prove the paleo-environmental evolution of the bay. Such changes of carbonate are due to the different deposition of calcium carbonate from biogenic source (probably and from inorganic source). The variation of organic carbon is still a factor of limited water circulation in the bay.

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Shafiu Kamba, Abdullahi, Maznah Ismail, Tengku Azmi Tengku Ibrahim et Zuki Abu Bakar Zakaria. « Synthesis and Characterisation of Calcium Carbonate Aragonite Nanocrystals from Cockle Shell Powder (Anadara granosa) ». Journal of Nanomaterials 2013 (2013) : 1–9. http://dx.doi.org/10.1155/2013/398357.

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The synthesis of pure calcium carbonate nanocrystals using a high pressure homogeniser (HPH) via a microemulsion system produced uniform nanosized particles, which were characterised using transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The identified particles were aragonite polymorphs with a rod shape and were approximately 50 nm in size. The aragonite polymorph of calcium carbonate was prepared from biogenic materials, cockle shells, and exhibited unique characteristics (i.e., a higher density than that of calcite), which makes it biocompatible and potentially suitable for applications in the medical, pharmaceutical, cosmetic, and paint industries. The methods adopted and the nonionic surfactant used in the synthesis of calcium carbonate nanocrystalline aragonite polymorphs were environmentally friendly and can be scaled up for industrial production. The sources are naturally available materials that are by-products of the seafood industry, which offers an opportunity for exploitation in numerous industrial applications.

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Gal, Assaf, Steve Weiner et Lia Addadi. « The Stabilizing Effect of Silicate on Biogenic and Synthetic Amorphous Calcium Carbonate ». Journal of the American Chemical Society 132, n^o 38 (29 septembre 2010) : 13208–11. http://dx.doi.org/10.1021/ja106883c.

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Freeh, Daniel M., et Mehmet Sarikaya. « Polymorphic Transition in Biogenic Calcium Carbonate : Nacre/Prismatic Interface in Abalone Shell ». Microscopy and Microanalysis 3, S2 (août 1997) : 753–54. http://dx.doi.org/10.1017/s1431927600010655.

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The research in biological hard tissues offers lessons for biomimetic (structure and processing) strategies, such as for the synthesis of hierarchical architectures tailored for specific engineering applications. These biocomposites, i.e., biogenic materials in which the major phase is an inorganic component associated with macromolecules (proteins and polysaccharides), include bones, dentin, sea-urchin skeletal units, bacterial and algal particles and molluscan shells. Here, a summary is given from a recent TEM study of the interfacial region of nacreous and prismatic sections of red abalone shell to understand the morphological and crystallographic correlations across this transition region.Many mollusk species have shells made of CaCO3 in various architectures that have evolved under different ecological conditions to produce structures that best protect the organism. The shells of many species contain both aragonite (orthorhombic, Pmnc) and calcite (Rhombohedral, R3m). In red abalone (Haliotis rufescens), the outer section, prismatic (P), is composed of columnar crystallites of calcite (1-5 μm base, 5-10 μm height), and the inner section, nacre (N), is composed of pseudo-hexagonal platelets of aragonite (side 2-5 μm), stacked as 0.25 μm layers, separated by a few nm-thick organic layer (Fig. 1).

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Zhong, Yu, Qi Li, Ren Wang et Ting Yao. « Changes of Physical and Mechanical Properties of Coral Reef Limestone under CO2–Seawater–Rock Interaction ». Applied Sciences 12, n^o 9 (19 avril 2022) : 4105. http://dx.doi.org/10.3390/app12094105.

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Large amounts of anthropogenic CO2 in the atmosphere are taken up when the ocean alters the seawater carbonate system, which could have a significant impact on carbonate-rich sediments. Coral reef limestone is a special biogenic carbonate, which is mainly composed of calcium carbonate. When carbonate-rich rocks are brought into contact with a CO2 weak acid solution, they will be dissolved, which may affect the physical and mechanical properties of the rock. In this paper, the physical and chemical interactions between CO2, seawater and the framework structure reef limestone were studied based on an experiment conducted in a hydrothermal reactor. The solution was analyzed for dissolved Ca2+ concentration during the reaction, and the rock mass, effective volume (except for the volume of open pores), permeability, images from electron microscopy and X-ray microtomography were contrasted before and after immersion. The uniaxial compressive and tensile strength tests were conducted, respectively, to clarify the mechanical response of the rock after the reaction. The results indicate that dissolution occurred during the reaction, and the calcium ions of the solution were increased. The physical properties of the rock were changed, and the permeability significantly increased. Because the rocks were soaked for only 15 days, the total cumulative amount of calcium carbonate dissolved was less, and the mechanical properties were not affected.

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Irfa’i, M. A., A. Prihanto, S. Muryanto, J. Jamari, R. Ismail et A. P. Bayuseno. « Precipitated Calcium Carbonate Derived from Green Mussel Shells Extracted from Magnesium Chloride Containing Solution ». IOP Conference Series : Earth and Environmental Science 1098, n^o 1 (1 octobre 2022) : 012021. http://dx.doi.org/10.1088/1755-1315/1098/1/012021.

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Abstract Green mussel shells are one of the calcium carbonate-rich biogenic sources. They contain 95.7 to 98.2 wt. % calcium. The high calcium content of green mussel shells was extracted and converted into calcium oxide material in the study by calcination at 900°C for 5 h. Later, at stirring times of 30, 60, 90, and 120 minutes, a solution medium containing magnesium chloride was used to dissolve the resulting calcination powder and subsequent carbonation for producing PCC (precipitated calcium carbonate). According to XRD, Rietveld, and FTIR analyses, the resulting PCC product with calcite-containing Mg was obtained primarily for a short stirring time of 30 minutes during the carbonation process, whereas calcite and aragonite were generated at longer stirring times (from 60 to 90 minutes). Instead, brucite was obtained after 120 minutes of stirring. The PCC product has a non-uniform polyhedrallic morphology of various small and large sizes as observed by SEM. This powder processing method allowed for faster PCC synthesis at a lower cost while requiring no chemical addition to increase basicity.

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Bundur, Zeynep Başaran, Ali Amiri, Yusuf Cagatay Ersan, Nico Boon et Nele De Belie. « Impact of air entraining admixtures on biogenic calcium carbonate precipitation and bacterial viability ». Cement and Concrete Research 98 (août 2017) : 44–49. http://dx.doi.org/10.1016/j.cemconres.2017.04.005.

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Levi-Kalisman, Y., S. Raz, S. Weiner, L. Addadi et I. Sagi. « Structural Differences Between Biogenic Amorphous Calcium Carbonate Phases Using X-ray Absorption Spectroscopy ». Advanced Functional Materials 12, n^o 1 (1 janvier 2002) : 43. http://dx.doi.org/10.1002/1616-3028(20020101)12:1<43 ::aid-adfm43>3.0.co;2-c.

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Sillen, Andrew. « Biogenic and diagenetic Sr/Ca in Plio-Pleistocene fossils of the Omo Shungura Formation ». Paleobiology 12, n^o 3 (1986) : 311–23. http://dx.doi.org/10.1017/s0094837300013816.

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Under conditions of normal calcium metabolism, strontium/calcium ratios (Sr/Ca) have been shown to reflect the trophic level of contemporary and recent terrestrial fauna. These ratios therefore offer a potential means of studying fossil ecosystems and the diet of prehistoric humans. In cases in which suitable controls have demonstrated the preservation of biogenic Sr/Ca, it has been possible to investigate the proportionate importance of meat vs. vegetable foods in the diets of prehistoric humans. However, diagenetic change after interment has made it impossible to discern biogenic Sr/Ca in faunal and human skeletons over 15,000 y b.p. A procedure is investigated for the analysis of biogenic and diagenetic apatite in vertebrate fossils, on the basis of solubility differences among carbonate, hydroxy-, and fluorapatites. When applied to the 2 ma b.p. fauna of the Omo Basin (Ethiopia), distinct characterization of the herbivore, omnivore, and carnivore fauna in conformity with trophism was discerned, in spite of anomalous Sr/Ca of one highly specialized carnivore,Homotherium.Possible metabolic and/or taphonomic explanations of this anomaly are discussed, and future basic research into the solubility profile procedure is outlined.

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Seredin, Pavel, Dmitry Goloshchapov, Nikita Buylov, Vladimir Kashkarov, Anna Emelyanova, Konstantin Eremeev et Yuri Ippolitov. « Compositional Analysis of the Dental Biomimetic Hybrid Nanomaterials Based on Bioinspired Nonstoichiometric Hydroxyapatite with Small Deviations in the Carbonate Incorporation ». Nanomaterials 12, n^o 24 (15 décembre 2022) : 4453. http://dx.doi.org/10.3390/nano12244453.

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In our paper, we discuss the results of a comprehensive structural-spectroscopic and microscopic analysis of non-stoichiometric nanocrystalline hydroxyapatite (CHAp) with low carbonate anion content and biomimetic hybrid nanomaterials produced on its basis. It was shown that hydroxyapatite nanocrystals synthesized by chemical precipitation and biogenic calcium source mimic the properties of biogenic apatite and also have a morphological organization of “core–shell” type. The “core” of the CHAp nanocrystal is characterized by an overabundance of calcium Ca/P~1.9. Thus “a shell” with thickness of ~3–5 nm is formed from intermediate apatite-like phases where the most probable are octocalcium phosphate, dicalcium phosphate dihydrate and tricalcium phosphate. The multimode model of the Raman profile of samples CHAp and biomimetic composites for spectral region 900–1100 cm−1 proposed in our work has allowed to allocate precise contribution of B-type carbonate substitution, taking into account the presence on a surface of “core” HAp nanocrystal of various third-party intermediate apatite-like phases. The calibration function constructed on the basis of the described model makes it possible to reliably determine small concentrations of carbonate in the structure of hydroxyapatite with the application of Raman express method of diagnostics. The results of our work can inspire researchers to study the processes of induced biomineralization in mineralized tissues of the human body, using non-destructive methods of control with simultaneous analysis of chemical bonding, as well as determining the role of impurity atoms in the functions exhibited by biotissue.

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Ghorbanzadeh, N., R. Shokati, M. B. Farhangi, M. Shabanpour et A. Unc. « Effect of the biogenic precipitation of calcium carbonate on bacterial transport in sand columns ». Ecohydrology & ; Hydrobiology 21, n^o 2 (avril 2021) : 280–91. http://dx.doi.org/10.1016/j.ecohyd.2021.01.001.

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Schoeppler, Vanessa, Deborah Stier, Benjamin H. Savitzky, Colin Ophus, Matthew A. Marcus, Karen C. Bustillo et Igor Zlotnikov. « Crystallization by Amorphous Particle Attachment and the Evolution of Texture in Biogenic Calcium Carbonate ». Microscopy and Microanalysis 28, S1 (22 juillet 2022) : 398–99. http://dx.doi.org/10.1017/s1431927622002318.

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Hathorne, Ed C., Rachael H. James, Paul Savage et Olivier Alard. « Physical and chemical characteristics of particles produced by laser ablation of biogenic calcium carbonate ». J. Anal. At. Spectrom. 23, n^o 2 (2008) : 240–43. http://dx.doi.org/10.1039/b706727e.

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Amiri, Ali, Mahzad Azima et Zeynep Başaran Bundur. « Crack remediation in mortar via biomineralization : Effects of chemical admixtures on biogenic calcium carbonate ». Construction and Building Materials 190 (novembre 2018) : 317–25. http://dx.doi.org/10.1016/j.conbuildmat.2018.09.083.

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Katti, Kalpana S., Daniel Frech, Maoxu Qian et Mehmet Sarikaya. « Local Dielectric Function Of Biogenic and Geological Polymorphs of CaCO3 Via Transmission Eels ». Microscopy and Microanalysis 4, S2 (juillet 1998) : 782–83. http://dx.doi.org/10.1017/s143192760002403x.

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This paper focuses on the differences of physical properties, specifically local dielectric function, of biogenic and geological mineral CaCO3. The goal is to assess the role of organism in forming biogenic inorganic materials. Local dielectric functions of biogenic and geological minerals were determined by transmission electron energy loss spectroscopy using a previously developed strategy.Previous work on microstructural characterization of biological hard tissues, e.g., abalone shells, has shown variations in terms of defects, morphology, crystallography, and organization of nano- and microstructures in two biological polymorphs of calcium carbonate, calcite and aragonite, in the prismatic and nacreous regions, respectively. In the abalone, the outer (1-5 mm thick) region of the shell is composed of calcite crystallites (1-5 μm diameter) with columnar organization perpendicular to shell plane. On the inner region, 1-10 mm thick nacre is composed of aragonite crystallites (0.5 μm thick and 5 -10 μm edge-length) forming flat platelets, parallel to the shell plane.

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Katti, Kalpana S., Maoxu Qian, Daniel W. Frech et Mehmet Sarikaya. « Low-loss Electron Energy-loss Spectroscopy and Dielectric Function of Biological and Geological Polymorphs of CaCO3 ». Microscopy and Microanalysis 5, n^o 5 (septembre 1999) : 358–64. http://dx.doi.org/10.1017/s1431927699000197.

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Previous work on microstructural characterization has shown variations in terms of defects and organization of nanostructures in the two polymorphs of calcium carbonate, calcite, and aragonite in mollusc shells. Large variations in mechanical properties are observed between these sections which have been attributed to variations in composite microstructure as well as intrinsic properties of the inorganic phases. Here we present local low-loss electron energy-loss spectroscopic (EELS) study of calcitic and aragonitic regions of abalone shell that were compared to geological (single-crystal) counterpart polymorphs to reveal intrinsic differences that could be related to organismal effects in biomineralization. In both sets of samples, local dielectric function is computed using Kramer-Kronig analysis. The electronic structures of biogenic and geological calcitic materials are not significantly different. On the other hand, electronic structure of biogenic aragonite is remarkably different from that of geological aragonite. This difference is attributed to the increased contribution from single electron excitations in biogenic aragonite as compared to that of geological aragonite. Implications of these changes are discussed in the context of macromolecular involvement in the making of the microstructures and properties in biogenic phases.

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Levi-Kalisman, Yael, Sefi Raz, Steve Weiner, Lia Addadi et Irit Sagi. « X-Ray absorption spectroscopy studies on the structure of a biogenic “amorphous” calcium carbonate phase † ». Journal of the Chemical Society, Dalton Transactions, n^o 21 (2000) : 3977–82. http://dx.doi.org/10.1039/b003242p.

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Tsao, Chieh, Pao-Tao Yu, Chin-Hsuan Lo, Chung-Kai Chang, Chia-Hsin Wang, Yaw-Wen Yang et Jerry Chun Chung Chan. « Anhydrous amorphous calcium carbonate (ACC) is structurally different from the transient phase of biogenic ACC ». Chemical Communications 55, n^o 48 (2019) : 6946–49. http://dx.doi.org/10.1039/c9cc00518h.

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Dhami, Navdeep Kaur, M. Sudhakara Reddy et Abhijit Mukherjee. « Bacillus megaterium mediated mineralization of calcium carbonate as biogenic surface treatment of green building materials ». World Journal of Microbiology and Biotechnology 29, n^o 12 (23 juin 2013) : 2397–406. http://dx.doi.org/10.1007/s11274-013-1408-z.

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Ellis, J. P., et J. D. Milliman. « Calcium carbonate suspended in Arabian Gulf and Red Sea waters ; biogenic and detrital, not "chemogenic" ». Journal of Sedimentary Research 55, n^o 6 (1 novembre 1985) : 805–8. http://dx.doi.org/10.1306/212f8805-2b24-11d7-8648000102c1865d.

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Balu, Satheeshkumar, Manisha Vidyavathy Sundaradoss, Swetha Andra et Jaison Jeevanandam. « Facile biogenic fabrication of hydroxyapatite nanorods using cuttlefish bone and their bactericidal and biocompatibility study ». Beilstein Journal of Nanotechnology 11 (4 février 2020) : 285–95. http://dx.doi.org/10.3762/bjnano.11.21.

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Cuttlefish bones are an inexpensive source of calcium carbonate, which are produced in large amounts by the marine food industry, leading to environmental contamination and waste. The nontoxicity, worldwide availability and low production cost of cuttlefish bone products makes them an excellent calcium carbonate precursor for the fabrication of hydroxyapatite. In the present study, a novel oil-bath-mediated precipitation method was introduced for the synthesis of hydroxyapatite (Hap) nanorods using cuttlefish bone powder as a precursor (CB-Hap NRs). The obtained CB-Hap NRs were investigated using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) techniques to evaluate their physicochemical properties. The crystallite size (20.86 nm) obtained from XRD data and the elemental analysis (Ca/P molar ratio was estimated to be 1.6) showed that the Hap NRs are similar to that of natural human bone (≈1.67). Moreover, the FTIR data confirmed the presence of phosphate as a functional group and the TGA data revealed the thermal stability of Hap NRs. In addition, the antibacterial study showed a significant inhibitory effect of CB-Hap NRs against S. aureus (zone of inhibition – 14.5 ± 0.5 mm) and E. coli (13 ± 0.5 mm), whereas the blood compatibility test showed that the CB-Hap NRs exhibited a concentration-mediated hemolytic effect. These biogenic CB-Hap NRs with improved physicochemical properties, blood compatibility and antibacterial efficacy could be highly beneficial for orthopedic applications in the future.

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Leelatawonchai, Panu, et Teerawat Laonapakul. « Preparation and Characterization of Calcium Sources from Golden Apple Snail Shell for Naturally Based Biomaterials ». Advanced Materials Research 931-932 (mai 2014) : 370–74. http://dx.doi.org/10.4028/www.scientific.net/amr.931-932.370.

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The use of biogenic materials to produce naturally based biomaterials has been widely studied. In this study, heavy metal content, phase transformation and physical characterization of Golden Apple Snail shell were investigated for use as a calcium source in the production of naturally based biomaterials. In order to investigate phase transformation, Golden Apple Snail shell was calcined at 600 °C, 700 °C, 800 °C and 900 °C. Small amounts of As and Pb were found in raw Golden Apple Snail shell. Calcium carbonate (CaCO3, calcite) and calcium oxide (CaO) phases were observed in Golden Apple Snail shells after calcination at 600 °C and 800 °C. Fine white CaCO3 (calcite) and CaO powders were prepared after calcination of Golden Apple Snail shells. The CaCO3 (calcite phase) was completely transformed into a CaO phase at 800 °C. Phase transformation depended on calcination temperature and time.

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Mehmood, Tariq, Syed Waseem Haider et Saima Siddiqui. « Major, Minor and Trace Elements Existence in Surface Sediments from Gwadar to Jiwani Coastal Areas of Pakistan ». International Journal of Economic and Environmental Geology 11, n^o 2 (25 septembre 2020) : 37–45. http://dx.doi.org/10.46660/ijeeg.vol11.iss2.2020.444.

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This study was carried out along the western coastal parts of Balochistan from Gwadar east Bay to Jiwani. The local anomaly of major, minor and trace elements were studied in this area. Zone-I (Gwadar east and west Bay) indicates that calcium oxide, potassium oxide and titanium dioxide have higher or average concentrations, while ZoneII indicates higher or average concentrations of calcium oxide, titanium dioxide and ferric oxide. Trace elements zirconium, chromium, europium, strontium, and copper are in higher or average concentrations in both zones. Gwadar west Bay and Jiwani are intermediate in carbonate, which show a high degree of maturity, suggesting the high rate of weathering in the source area. Sediment samples from Ganz, Jiwani, and Gwadar east Bay represent the quartz-rich fields in this region. Gwadar east Bay has a positive correlation between aluminium oxide and potassium oxide which suggests that abundance of potassium oxide is controlled by variation in K-feldspar contents. A positive correlation between strontium and calcium oxide suggests that strontium is associated with calcium oxide in biogenic carbonate material in Gwadar west Bay. The positive correlation between aluminium oxide, copper, and zinc in Pishukan indicates that the abundance of these elements is due to limited silt and clay fractions present in sediments. Enrichment factor shows that chromium and strontium are probably of anthropogenic origin in this region. Keywords

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Keul, N., G. Langer, L. J. de Nooijer et J. Bijma. « Effect of ocean acidification on the benthic foraminifera Ammonia ; sp. is caused by a decrease in carbonate ion concentration ». Biogeosciences Discussions 10, n^o 1 (25 janvier 2013) : 1147–76. http://dx.doi.org/10.5194/bgd-10-1147-2013.

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Abstract. About 30% of the anthropogenically released CO2 is taken up by the oceans, which causes surface ocean pH to decrease and is commonly referred to as Ocean Acidification (OA). Foraminifera are one of the most abundant groups of marine calcifiers, estimated to precipitate ca. 50% of biogenic calcium carbonate in the open oceans. We have compiled the state of the art of OA effects on foraminifera, because the majority of OA research on this group was published within the last 3 yr. Disparate responses of this important group of marine calcifiers to OA were reported, highlighting the importance of a process based understanding of OA effects on foraminifera. The benthic foraminifer Ammonia sp. was cultured using two carbonate chemistry manipulation approaches: While pH and carbonate ions where varied in one, pH was kept constant in the other while carbonate ion concentration varied. This allows the identification of teh parameter of the parameter of the carbonate system causing observed effects. This parameter identification is the first step towards a process based understanding. We argue that [CO32−] is the parameter affecting foraminiferal size normalized weights (SNW) and growth rates and based on the presented data we can confirm the strong potential of foraminiferal SNW as a [CO32−] proxy.

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Politi, Yael, David R. Batchelor, Paul Zaslansky, Bradley F. Chmelka, James C. Weaver, Irit Sagi, Steve Weiner et Lia Addadi. « Role of Magnesium Ion in the Stabilization of Biogenic Amorphous Calcium Carbonate : A Structure−Function Investigation ». Chemistry of Materials 22, n^o 1 (12 janvier 2010) : 161–66. http://dx.doi.org/10.1021/cm902674h.

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NIEBUHR, BIRGIT. « Geochemistry and time-series analyses of orbitally forced Upper Cretaceous marl–limestone rhythmites (Lehrte West Syncline, northern Germany) ». Geological Magazine 142, n^o 1 (janvier 2005) : 31–55. http://dx.doi.org/10.1017/s0016756804009999.

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A cyclic marl–limestone succession of Middle–Late Campanian age has been investigated with respect to a Milankovitch-controlled origin of geochemical data. In general, the major element geochemistry of the marl–limestone rhythmites can be explained by a simple two-component mixing model with the end-members calcium carbonate and ‘average shale’-like material. Carbonate content varies from 55 to 90%. Non-carbonate components are clay minerals (illite, smectite) and biogenic silica from sponge spicules, as well as authigenically formed zeolites (strontian heulandite) and quartz. The redox potential suggests oxidizing conditions throughout the section. Trace element and stable isotopic data as well as SEM investigations show that the carbonate mud is mostly composed of low-magnesium calcitic tests of planktic coccolithophorids and calcareous dinoflagellate cysts (calcispheres). Diagenetic overprint results in a decrease of 2% δ18O and an increase in Mn of up to 250 ppm. However, the sediment seems to preserve most of its high Sr content compared to the primary low-magnesium calcite of co-occurring belemnite rostra. The periodicity of geochemical cycles is dominated by 413 ka and weak signals between 51 and 22.5 ka, attributable to orbital forcing. Accumulation rates within these cycles vary between 40 and 50 m/Ma. The resulting cyclic sedimentary sequence is the product of (a) changes in primary production of low-magnesium calcitic biogenic material in surface waters within the long eccentricity and the precession, demonstrated by the CaCO3 content and the Mg/Al, Mn/Al and Sr/Al ratios, and (b) fluctuations in climate and continental weathering, which changed the quality of supplied clay minerals (the illite/smectite ratio), demonstrated by the K/Al ratio. High carbonate productivity correlates with smectite-favouring weathering (semi-arid conditions, conspicuously dry and moist seasonal changes in warmer climates). Ti as the proxy indicator for the detrital terrigenous influx, as well as Rb, Si, Zr and Na, shows only low frequency signals, indicating nearly constant rates of supply throughout the more or less pure pelagic carbonate deposition of the long-lasting third-order Middle–Upper Campanian sedimentary cycle.

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Daux, Valérie, Alain Foucault, Frédéric Melieres et Mélanie Turpin. « Sapropel-like Pliocene sediments of Sicily deposited under oxygenated bottom water ». Bulletin de la Société Géologique de France 177, n^o 2 (1 mars 2006) : 79–88. http://dx.doi.org/10.2113/gssgfbull.177.2.79.

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Abstract The Pliocene Punta Piccola series, deposited on the Sicily sill at 100–400 m depths, consists of alternating whitish hemipelagic marl and carbonate-poor, organic-carbon-richer, brownish dark marl. The rhythmic bedding is interpreted to result from the precession driven alternation of more or less humid periods. In the present study, we compare the mineralogical and geochemical composition (isotope ratios of oxygen and carbon; Ca, Mn, Mg, Sr, and Fe concentrations) of the carbonate fractions of the whitish marl to those of the dark layers to evaluate the environmental changes that likely produced these alternations. High Mn concentrations in the dark layers, and the occurrence of pseudo-kutnahorite (Mn-Ca mixed carbonate), bioturbation, ostracodes, and benthic foraminifera favour the hypothesis of the dark-layer deposition taking place under oxygen-bearing bottom waters. The original value of the concentration of the organic carbon in the dark layers of Punta Piccola, estimated from the δ13C measured in the carbonate fraction, was higher than the post-diagenetic one. It may have reached 7% in the dark layer 107, which was therefore a true sapropel at the time of deposition. This result indicates that anoxic conditions are not a prerequisite for sapropelic sediment formation. However, the pristine concentration of the organic carbon in the dark layers at Punta Piccola is lower than those of coeval sapropels cored in the nearby deep settings, which were deposited under an anoxic water column. This difference may result from the effect of water column anoxia on the organic carbon content. Diagenetic reactions took place in the dark layers through the oxidation of large amounts of organic matter. The dissolution of primary calcium carbonates (biogenic in origin) and the reduction of Fe and Mn oxyhydroxides led the interstitial solutions to be supersaturated towards Mn-rich calcite and/or pseudo-kutnahorite. The secondary carbonates are Mg-enriched and Sr and Fe-depleted. The negative shifts of the δ18O signal in the carbonates of the dark layers of Punta Piccola are consistent with an increased river discharge in the Mediterranean at the time of deposition.

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Keul, N., G. Langer, L. J. de Nooijer et J. Bijma. « Effect of ocean acidification on the benthic foraminifera Ammonia ; sp. is caused by a decrease in carbonate ion concentration ». Biogeosciences 10, n^o 10 (1 octobre 2013) : 6185–98. http://dx.doi.org/10.5194/bg-10-6185-2013.

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Abstract. About 30% of the anthropogenically released CO2 is taken up by the oceans; such uptake causes surface ocean pH to decrease and is commonly referred to as ocean acidification (OA). Foraminifera are one of the most abundant groups of marine calcifiers, estimated to precipitate ca. 50 % of biogenic calcium carbonate in the open oceans. We have compiled the state of the art literature on OA effects on foraminifera, because the majority of OA research on this group was published within the last three years. Disparate responses of this important group of marine calcifiers to OA were reported, highlighting the importance of a process-based understanding of OA effects on foraminifera. We cultured the benthic foraminifer Ammonia sp. under a range of carbonate chemistry manipulation treatments to identify the parameter of the carbonate system causing the observed effects. This parameter identification is the first step towards a process-based understanding. We argue that [CO32−] is the parameter affecting foraminiferal size-normalized weights (SNWs) and growth rates. Based on the presented data, we can confirm the strong potential of Ammonia sp. foraminiferal SNW as a [CO32−] proxy.

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Zhou, Xueli, Weizhen Liu, Jian Zhang, Can Wu, Xinwen Ou, Chen Tian, Zhang Lin et Zhi Dang. « Biogenic Calcium Carbonate with Hierarchical Organic–Inorganic Composite Structure Enhancing the Removal of Pb(II) from Wastewater ». ACS Applied Materials & ; Interfaces 9, n^o 41 (9 octobre 2017) : 35785–93. http://dx.doi.org/10.1021/acsami.7b09304.

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