Journal articles on the topic 'Bulk inorganic carbonate'
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Zhang, Xiang, Xin Chen, Ming Hui Feng, Zai Fang Zheng, Gong Pei Pan, and Hui Ping Lv. "Influences of Bulking and Porous Structure on Barium Nitrate as Pyrotechnic Oxidants." Advanced Materials Research 550-553 (July 2012): 27–31. http://dx.doi.org/10.4028/www.scientific.net/amr.550-553.27.
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An experimental investigation was carried out to explore the major physical and chemical properties of expanded barium nitrate. Expanded barium nitrate with porous structure was made. The method is as follows: moderately evaporate the solution of barium nitrate and inorganic vesicant; heat the crystallized mixture to decompose the inorganic vesicants. The inorganic vesicants are potassium carbonate, sodium carbonate, ammonium carbonate, ammonium oxalate, potassium acetate, ammonium acetate and ammonium perchlorate. The SEM shows that the modified barium nitrate with potassium carbonate has obvious porous structure. The bulk density of the modified barium nitrate with ammonium perchlorate decreases by 14.6% and the hygroscopicity of that with ammonium oxalate is only 0.06%. The one with sodium carbonate decomposes at 300°C. The safety test shows that both the impact sensitivity and friction sensitivity are 0%.
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Wang, Jirong, Xiaolin Xie, Zhigang Xue, Christophe Fliedel, and Rinaldo Poli. "Ligand- and solvent-free ATRP of MMA with FeBr3 and inorganic salts." Polymer Chemistry 11, no. 7 (2020): 1375–85. http://dx.doi.org/10.1039/c9py01840a.
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A new cost-effective and safe protocol for the bulk ATRP of MMA uses FeBr3, EBrPA and an inorganic compound (carbonate, bicarbonate, phosphate, hydroxide, chloride, bromide) of an alkali metal cation.
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Schobben, Martin, Sebastiaan van de Velde, Jana Gliwa, Lucyna Leda, Dieter Korn, Ulrich Struck, Clemens Vinzenz Ullmann, et al. "Latest Permian carbonate carbon isotope variability traces heterogeneous organic carbon accumulation and authigenic carbonate formation." Climate of the Past 13, no. 11 (November 22, 2017): 1635–59. http://dx.doi.org/10.5194/cp-13-1635-2017.
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Abstract. Bulk-carbonate carbon isotope ratios are a widely applied proxy for investigating the ancient biogeochemical carbon cycle. Temporal carbon isotope trends serve as a prime stratigraphic tool, with the inherent assumption that bulk micritic carbonate rock is a faithful geochemical recorder of the isotopic composition of seawater dissolved inorganic carbon. However, bulk-carbonate rock is also prone to incorporate diagenetic signals. The aim of the present study is to disentangle primary trends from diagenetic signals in carbon isotope records which traverse the Permian–Triassic boundary in the marine carbonate-bearing sequences of Iran and South China. By pooling newly produced and published carbon isotope data, we confirm that a global first-order trend towards depleted values exists. However, a large amount of scatter is superimposed on this geochemical record. In addition, we observe a temporal trend in the amplitude of this residual δ13C variability, which is reproducible for the two studied regions. We suggest that (sub-)sea-floor microbial communities and their control on calcite nucleation and ambient porewater dissolved inorganic carbon δ13C pose a viable mechanism to induce bulk-rock δ13C variability. Numerical model calculations highlight that early diagenetic carbonate rock stabilization and linked carbon isotope alteration can be controlled by organic matter supply and subsequent microbial remineralization. A major biotic decline among Late Permian bottom-dwelling organisms facilitated a spatial increase in heterogeneous organic carbon accumulation. Combined with low marine sulfate, this resulted in varying degrees of carbon isotope overprinting. A simulated time series suggests that a 50 % increase in the spatial scatter of organic carbon relative to the average, in addition to an imposed increase in the likelihood of sampling cements formed by microbial calcite nucleation to 1 out of 10 samples, is sufficient to induce the observed signal of carbon isotope variability. These findings put constraints on the application of Permian–Triassic carbon isotope chemostratigraphy based on whole-rock samples, which appears less refined than classical biozonation dating schemes. On the other hand, this signal of increased carbon isotope variability concurrent with the largest mass extinction of the Phanerozoic may provide information about local carbon cycling mediated by spatially heterogeneous (sub-)sea-floor microbial communities under suppressed bioturbation.
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Yoshida, Akihiko, Toshiki Miyazaki, Eiichi Ishida, and Masahiro Ashizuka. "Preparation of Cellulose-Carbonate Apatite Composites through Mechanochemical Reaction." Key Engineering Materials 284-286 (April 2005): 855–58. http://dx.doi.org/10.4028/www.scientific.net/kem.284-286.855.
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Organic-inorganic composites composed of organic polymer and carbonate hydroxyapatite (CHAp) would be useful bone substitute materials exhibiting low young’s modulus and bone-bonding bioactivity. In this work, such a composite was synthesized from cellulose (CEL)and CHAp through mechanochemical reaction. Homogeneous bulk CEL-CHAp composites were obtained when poly( ε-caprolactone) (PCL) was added as plasticizer with PCL/(PCL+CEL) weight ratio of 20 wt% or less. The CEL-CHAp composites contained B-type CHAp in inorganic phase. The composites with (CEL+PCL)/(CHAp) weight ratio = 20/80 and 10/90 kept the shape in simulated body fluid (SBF), and showed apatite formation after soaking in SBF. Therefore, the CEL-CHAp composites are expected to be materials with low young’s modulus and bioactivity.
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Lojen, Sonja, Ivan Sondi, and Mladen Juracic. "Geochemical conditions for the preservation of recent aragonite-rich sediments in Mediterranean karstic marine lakes (Mljet Island, Adriatic Sea, Croatia)." Marine and Freshwater Research 61, no. 1 (2010): 119. http://dx.doi.org/10.1071/mf09034.
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Conditions for the preservation of recent aragonite-rich sediments during early diagenesis in two semi-enclosed Mediterranean karstic seawater lakes on the island of Mljet (Adriatic Sea) were examined. The concentrations and stable isotope compositions of carbonate and sedimentary organic matter, as well as the geochemical parameters in pore water were measured. It was found that the smaller lake (Malo Jezero) receives considerably more terrestrial detritus than the larger lake (Veliko Jezero). A decrease in carbonate δ13C values with depth indicated a rather intensive transfer of organically derived C into the carbonate pool by diagenetic recrystallisation, masking the changes in carbonate δ13C caused by increasing amounts of aragonite. Dissolution of calcite as a result of CO2 released from the decomposition of organic debris and the upward diffusive flux of dissolved inorganic carbon were together responsible for up to 24% of the dissolved inorganic carbon added to the pore water. This indicated locally occurring carbonate dissolution, irrespective of its saturation state in the bulk sediment. Despite the larger input of terrigenous material into Malo Jezero, the carbonate content in the sediment was much higher than in Veliko Jezero, indicating greater authigenic aragonite production. As magnesium calcite accounted for most of the carbonate dissolution, aragonite preservation in the sediment is favoured.
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Rose, Catherine V., Samuel M. Webb, Matthew Newville, Antonio Lanzirotti, Jocelyn A. Richardson, Nicholas J. Tosca, Jeffrey G. Catalano, Alexander S. Bradley, and David A. Fike. "Insights into past ocean proxies from micron-scale mapping of sulfur species in carbonates." Geology 47, no. 9 (July 5, 2019): 833–37. http://dx.doi.org/10.1130/g46228.1.
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Abstract Geological reconstructions of global ocean chemistry and atmospheric oxygen concentrations over Earth history commonly rely on the abundance and stable isotopic composition (δ34S) of sulfur-bearing compounds. Carbonate-associated sulfate (CAS), sulfate bound within a calcium carbonate mineral matrix, is among the most commonly interrogated sulfur mineral phases. However, recent work has revealed variability in δ34SCAS values that cannot be explained by evolution of the marine sulfate reservoir, challenging the common interpretation that CAS is inherently a high-fidelity record of seawater sulfate. To investigate the source of this inconsistency, we used X-ray spectromicroscopy to map the micron-scale distribution of S-bearing sedimentary phases in Ordovician-aged (ca. 444 Ma) shallow marine carbonates from Anticosti Island, Québec, Canada. Clear differences in the abundance of CAS are observed between cements and fossils, suggesting that variance in bulk-rock data could be a consequence of component mixing and that coupled synchrotron-petrographic screening can identify the carbonate components that are most likely to retain primary CAS. Furthermore, we observe multiple, distinct forms of sulfate (both inorganic and organic). Differences in these forms among fossil clades could provide new insights into biomineralization mechanisms in extinct organisms.
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Wei, Qiang, Gang Zhang, Jie Yao, Xuejun Chen, Gongying Wang, and Xiangui Yang. "One-step bulk fabrication of a CaO/carbon heterogeneous catalyst from calcium citrate for rapid synthesis of dimethyl carbonate (DMC) by transesterification of ethylene carbonate (EC)." New Journal of Chemistry 45, no. 12 (2021): 5540–50. http://dx.doi.org/10.1039/d0nj06144a.
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Mu, Zhao, Kangren Kong, Kai Jiang, Hongliang Dong, Xurong Xu, Zhaoming Liu, and Ruikang Tang. "Pressure-driven fusion of amorphous particles into integrated monoliths." Science 372, no. 6549 (June 24, 2021): 1466–70. http://dx.doi.org/10.1126/science.abg1915.
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Biological organisms can use amorphous precursors to produce inorganic skeletons with continuous structures through complete particle fusion. Synthesizing monoliths is much more difficult because sintering techniques can destroy continuity and limit mechanical strength. We manufactured inorganic monoliths of amorphous calcium carbonate by the fusion of particles while regulating structurally bound water and external pressure. Our monoliths are transparent, owing to their structural continuity, with a mechanical strength approaching that of single-crystal calcite. Dynamic water channels within the amorphous bulk are synergistically controlled by water content and applied pressure and promote mass transportation for particle fusion. Our strategy provides an alternative to traditional sintering methods that should be attractive for constructing monoliths of temperature-sensitive biominerals and biomaterials.
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Preto, N., C. Agnini, M. Rigo, M. Sprovieri, and H. Westphal. "The calcareous nannofossil <i>Prinsiosphaera</i> achieved rock-forming abundances in the latest Triassic of western Tethys: consequences for the <i>δ</i><sup>13</sup>C of bulk carbonate." Biogeosciences 10, no. 9 (September 23, 2013): 6053–68. http://dx.doi.org/10.5194/bg-10-6053-2013.
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Abstract. The onset of pelagic biomineralization was a milestone in the history of the long-term inorganic carbon cycle: as soon as calcareous nannofossils became major limestone producers, the pH and supersaturation state of the global ocean were stabilized (the so-called mid-Mesozoic revolution). But although it is known that calcareous nannofossils were abundant already by the end of the Triassic, no estimates exist on their contribution to hemipelagic carbonate sedimentation. With this work, we estimate the volume proportion of Prinsiosphaera, the dominant late Triassic calcareous nannofossil, in hemipelagic and pelagic carbonates of western Tethys. The investigated Upper Triassic lime mudstones are composed essentially of microspar and tests of calcareous nannofossils, plus minor bioclasts. Prinsiosphaera had become a significant component of lime mudstones since the late Norian, and was contributing up to ca. 60% of the carbonate by the late Rhaetian in periplatform environments with hemipelagic sedimentation. The increasing proportion of Prinsiosphaera in upper Rhaetian hemipelagic lime mudstones is paralleled by an increase of the δ13C of bulk carbonate. We interpreted this isotopic trend as related to the diagenesis of microspar, which incorporated respired organic carbon with a low δ13C when it formed during shallow burial. As the proportion of nannofossil tests increased, the contribution of microspar with low δ13C diminished, determining the isotopic trend. We suggest that a similar diagenetic effect may be observed in many Mesozoic limestones with a significant, but not yet dominant, proportion of calcareous plankton.
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Preto, N., C. Agnini, M. Rigo, M. Sprovieri, and H. Westphal. "The calcareous nannofossil <i>Prinsiosphaera</i> achieved rock-forming abundances in the latest Triassic of western Tethys: consequences for the δ<sup>13</sup>C of bulk carbonate." Biogeosciences Discussions 10, no. 5 (May 14, 2013): 7989–8025. http://dx.doi.org/10.5194/bgd-10-7989-2013.
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Abstract. The onset of pelagic biomineralization marked a milestone in the history of the long term inorganic carbon cycle: as soon as calcareous nannofossils became major limestone producers, the pH and supersaturation state of the global ocean were stabilized (the so-called Mid Mesozoic Revolution). But although it is known that calcareous nannofossils were abundant already by the end of the Triassic, no estimates exist on their contribution to hemipelagic carbonate sedimentation. With this work, we estimate the volume proportion of Prinsiosphaera, the dominant Late Triassic calcareous nannofossil, in hemipelagic and pelagic carbonates of western Tethys. The investigated Upper Triassic lime mudstones are composed essentially of microspar and tests of calcareous nannofossils, plus minor bioclasts. Prinsiosphaera became a significant component of lime mudstones since the late Norian, and was contributing up to ca. 60% of the carbonate by the late Rhaetian in periplatform environments with hemipelagic sedimentation. The increasing proportion of Prinsiosphaera in upper Rhaetian hemipelagic lime mudstones is paralleled by a increase of the δ13C of bulk carbonate. We interpreted this isotopic trend as related to the diagenesis of microspar, which incorporated respired organic carbon with a low δ13C when it formed during shallow burial. As the proportion of nannofossil tests increased, the contribution of microspar with low δ13C diminished, determining the isotopic trend. We suggest that a similar diagenetic effect may be observed in many Mesozoic limestones with a significant, but not yet dominant, proportion of calcareous plankton.
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Mansour, Ahmed, Thomas Gentzis, Michael Wagreich, Sameh S. Tahoun, and Ashraf M. T. Elewa. "Short-Term Sea Level Changes of the Upper Cretaceous Carbonates: Calibration between Palynomorphs Composition, Inorganic Geochemistry, and Stable Isotopes." Minerals 10, no. 12 (December 7, 2020): 1099. http://dx.doi.org/10.3390/min10121099.
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Widespread deposition of pelagic-hemipelagic sediments provide an archive for the Late Cretaceous greenhouse that triggered sea level oscillations. Global distribution of dinoflagellate cysts (dinocysts) exhibited a comparable pattern to the eustatic sea level, and thus, considered reliable indicators for sea level and sequence stratigraphic reconstructions. Highly diverse assemblage of marine palynomorphs along with elemental proxies that relate to carbonates and siliciclastics and bulk carbonate δ13C and δ18O from the Upper Cretaceous Abu Roash A Member were used to reconstruct short-term sea level oscillations in the Abu Gharadig Basin, southern Tethys. Additionally, we investigated the relationship between various palynological, elemental, and isotope geochemistry parameters and their response to sea level changes and examined the link between these sea level changes and Late Cretaceous climate. This multiproxy approach revealed that a long-term sea-level rise, interrupted by minor short-term fall, was prevalent during the Coniacian-earliest Campanian in the southern Tethys, which allowed to divide the studied succession into four complete and two incomplete 3rd order transgressive-regressive sequences. Carbon and oxygen isotopes of bulk hemipelagic carbonates were calibrated with gonyaulacoids and freshwater algae (FWA)-pteridophyte spores and results showed that positive δ13Ccarb trends were consistent, in part, with excess gonyaulacoid dinocysts and reduced FWA-spores, reinforcing a rising sea level and vice versa. A reverse pattern was shown between the δ18Ocarb and gonyaulacoid dinocysts, where negative δ18Ocarb trends were slightly consistent with enhanced gonyaulacoid content, indicating a rising sea level and vice versa. However, stable isotope trends were not in agreement with palynological calibrations at some intervals. Therefore, the isotope records can be used as reliable indicators for reconstructing changes in long-term sea level rather than short-term oscillations.
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Sánchez-Marín, Paula, Claude Fortin, and Peter G. C. Campbell. "Copper and lead internalisation by freshwater microalgae at different carbonate concentrations." Environmental Chemistry 10, no. 2 (2013): 80. http://dx.doi.org/10.1071/en13011.
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Environmental context Metal–carbonato complexes have been reported to contribute to metal uptake and toxicity in aquatic organisms. We show that in the presence of lead–carbonato complexes, Pb internalisation by the microalga Chlamydomonas reinhardtii is higher than that predicted on the basis of the free Pb2+ concentration. This effect, which was not observed for another microalga that takes up Pb more slowly, is attributed to the very high rates of Pb uptake by C. reinhardtii, which result in diffusion limitation. Abstract The possible contribution of metal–carbonato complexes to metal uptake or toxicity has been mentioned several times in the literature, often in studies where dissolved inorganic carbon (DIC) concentrations and pH were varied together, but a thorough study of the effect on DIC on metal bioavailability to aquatic organisms has not been done. By using closed systems – allowing changes in DIC concentrations at fixed pH – and ion selective electrodes to determine free metal ion concentrations, we show that lead internalisation by the unicellular alga Chlamydomonas reinhardtii in the presence of high DIC concentrations is higher than predicted by the free Pb2+ ion concentration at bulk [Pb2+] lower than 50nM, but not at higher [Pb2+]. This effect is not observed for another microalga, Chlorella vulgaris, which shows a lower rate of Pb internalisation. Copper internalisation by C. reinhardtii seems also to be slightly higher than predicted on the basis of free Cu2+ at low (20nM) bulk Cu2+ concentrations but not at higher ones. The possibility that Pb (and Cu) internalisation by C. reinhardtii is partially limited by diffusion from the bulk solution to the algal surface is identified and discussed as a possible explanation for these results.
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Wolstenholme, Anne, G. T. Cook, A. B. MacKenzie, Philip Naysmith, P. S. Meadows, and Paul McDonald. "The Behavior of Sellafield-Derived 14C in the Northeast Irish Sea." Radiocarbon 40, no. 1 (1997): 447–58. http://dx.doi.org/10.1017/s0033822200018336.
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Radiocarbon is an important constituent of the low level, liquid, radioactive effluent discharged from the Sellafield nuclear fuel reprocessing plant in northwest England, but despite the fact that it gives the highest collective dose commitment of all the nuclides in the waste, its behavior in the Irish Sea is poorly defined. There is therefore a clear requirement for an improved understanding of 14C behavior in the Irish Sea, to assist with dose evaluation modeling and definition of the mixing and accumulation characteristics of the sediment in this area. In this context, results are presented here for a temporal study of 14C activities in four geochemical fractions of seawater and in a sediment core from the vicinity of the Sellafield effluent outfall. Clear 14C enrichments in the dissolved inorganic carbon (DIC) and particulate organic carbon (POC) components of seawater were observed, with temporal trends in activity that were related to variations in the Sellafield discharge. Smaller, but nevertheless detectable, enrichments were also observed for particulate inorganic carbon (PIC) and dissolved organic carbon (DOC) in the seawater. The distribution of 137Cs and 241Am revealed that the sediment core could be classified into three zones in which the intensity of mixing decreased discontinuously with depth. Bulk carbonate 14C analyses of the core demonstrated the presence of glacial or pre-glacial carbonate in the system, but failed to show any evidence of contaminant 14C input or provide information on sediment accumulation processes. In contrast, analysis of bulk organic matter from the sediment provided clear evidence of the recent perturbation of a well mixed system by input of younger material, consistent with the recent input of contaminant 14C from Sellafield and possibly weapons testing fallout.
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He, Zhong, Zengzilu Xia, Mengying Zhang, Jinbo Wu, and Weijia Wen. "Calcium Carbonate Mineralization in a Surface-Tension-Confined Droplets Array." Crystals 9, no. 6 (May 30, 2019): 284. http://dx.doi.org/10.3390/cryst9060284.
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Calcium carbonate biomimetic crystallization remains a topic of interest with respect to biomineralization areas in recent research. It is not easy to conduct high-throughput experiments with only a few macromolecule reagents using conventional experimental methods. However, the emergence of microdroplet array technology provides the possibility to solve these issues efficiently. In this article, surface-tension-confined droplet arrays were used to fabricate calcium carbonate. It was found that calcium carbonate crystallization can be conducted in surface-tension-confined droplets. Defects were found on the surface of some crystals, which were caused by liquid flow inside the droplet and the rapid drop in droplet height during the evaporation. The diameter and number of crystals were related to the droplet diameter. Polyacrylic acid (PAA), added as a modified organic molecule control, changed the CaCO3 morphology from calcite to vaterite. The material products of the above experiments were compared with bulk-synthesized calcium carbonate by scanning electron microscopy (SEM), Raman spectroscopy and other characterization methods. Our work proves the possibility of performing biomimetic crystallization and biomineralization experiments on surface-tension-confined microdroplet arrays.
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Hadden, Carla S., Kathy M. Loftis, Alexander Cherkinsky, Brandon T. Ritchison, Isabelle H. Lulewicz, and Victor D. Thompson. "Radiocarbon in Marsh Periwinkle (Littorina Irrorata) Conchiolin: Applications for Archaeology." Radiocarbon 61, no. 5 (May 28, 2019): 1489–500. http://dx.doi.org/10.1017/rdc.2019.53.
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ABSTRACTIn coastal and island archaeology, carbonate mollusk shells are often among the most abundant materials available for radiocarbon (14C) dating. The marsh periwinkle (Littorina irrorata) is one of these such species, ubiquitously found along the Atlantic and Gulf coasts of the United States in both modern and archaeological contexts. This paper presents a novel approach to dating estuarine mollusks where rather than attempting to characterize the size and variability of reservoir effects to “correct” shell carbonate dates, we describe a compound-specific approach that isolates conchiolin, the organic matter bound with the shell matrix of the L. irrorata. Conchiolin typically constitutes <5% of shell weight. In L. irrorata, it is derived from the snail’s terrestrial diet and is thus not strongly influenced by marine, hardwater, or other carbon reservoir effects. We compare the carbon isotopes (δ13C and Δ14C) of L. irrorata shell carbonate, conchiolin, and bulk soft tissue from six modern, live-collected specimens from Apalachicola Bay, Florida, with samples that represent possible sources of carbon within their environment including surface sediments, marsh plant tissues, and dissolved inorganic carbon (DIC) in water. Ultimately, this paper demonstrates that samples obtained from wet chemical oxidation of L. irrorata conchiolin produces accurate 14C dates.
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Else, Brent G. T., Araleigh Cranch, Richard P. Sims, Samantha Jones, Laura A. Dalman, Christopher J. Mundy, Rebecca A. Segal, Randall K. Scharien, and Tania Guha. "Variability in sea ice carbonate chemistry: a case study comparing the importance of ikaite precipitation, bottom-ice algae, and currents across an invisible polynya." Cryosphere 16, no. 9 (September 13, 2022): 3685–701. http://dx.doi.org/10.5194/tc-16-3685-2022.
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Abstract. The carbonate chemistry of sea ice is known to play a role in global carbon cycles, but its importance is uncertain in part due to disparities in reported results. Variability in physical and biological drivers is usually invoked to explain differences between studies. In the Canadian Arctic Archipelago, “invisible polynyas” – areas of strong currents, thin ice, and potentially high biological productivity – are examples of extreme spatial variability. We used an invisible polynya as a natural laboratory to study the effects of inferred initial ice formation conditions, ice growth rate, and algal biomass on the distribution of carbonate species by collecting enough cores to perform a statistical comparison between sites located within, and just outside of, a polynya near Iqaluktuttiaq (Cambridge Bay, Nunavut, Canada). At both sites, the uppermost 10 cm ice horizon showed evidence of CO2 off-gassing, while carbonate distributions in the middle and bottommost 10 cm horizons largely followed the salinity distribution. In the polynya, the upper ice horizon had significantly higher bulk total inorganic carbon (TIC), total alkalinity (TA), and salinity potentially due to freeze-up conditions that favoured frazil ice production. The middle ice horizons were statistically indistinguishable between sites, suggesting that ice growth rate is not an important factor for the carbonate distribution under mid-winter conditions. The thicker (non-polynya) site experienced higher algal biomass, TIC, and TA in the bottom horizon. Carbonate chemistry in the bottom horizon could largely be explained by the salinity distribution, with the strong currents at the polynya site potentially playing a role in desalinization; biology appeared to exert only a minor control, with some evidence that the ice algae community was net heterotrophic. We did see evidence of calcium carbonate precipitation but with little impact on the TIC:TA ratio and little difference between sites. Because differences were constrained to relatively thin layers at the top and bottom, vertically averaged values of TIC, TA, and especially the TIC:TA ratio were not meaningfully different between sites. This provides some justification for using a single bulk value for each parameter when modelling sea ice effects on ocean chemistry at coarse resolution. Exactly what value to use (particularly for the TIC:TA ratio) likely varies by region but could potentially be approximated from knowledge of the source seawater and sea ice salinity. Further insights await a rigorous intercomparison of existing data.
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Hadden, Carla S., Kathy M. Loftis, and Alexander Cherkinsky. "Carbon Isotopes (δ13C and Δ14C) in Shell Carbonate, Conchiolin, and Soft Tissues in Eastern Oyster (Crassostrea Virginica)." Radiocarbon 60, no. 4 (April 27, 2018): 1125–37. http://dx.doi.org/10.1017/rdc.2018.27.
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AbstractBiogeochemical analyses of eastern oysters (Crassostrea virginica) are frequently included in environmental monitoring and paleoecological studies because their shells and soft tissues record environmental and dietary signals. Carbon isotopes in the mineral phase of the shell are derived from ambient bicarbonate and dissolved inorganic carbon (DIC), while organic carbon present in soft tissue is of dietary origin. Mineral-bound organic matter within the carbonate shell matrix (“conchiolin”) is studied less frequently. The purpose of this study was to compare carbon isotope composition (δ13C and Δ14C) of conchiolin to those of shell carbonates and soft tissues in eastern oysters and assess the extent to which conchiolin can provide insight into paleoecological records. Eleven oyster specimens were live-collected from Apalachicola Bay, USA, as well as a set of environmental samples (water, sediment, and terrestrial plants). Overall, the δ13C values in all studied oyster tissue types record environmental signals related to carbon sources, with conchiolin being enriched in 13C by an average of 2.3‰ relative to bulk soft tissues. Δ14C values in oyster shell carbonates generally reflect the marine versus riverine source of DIC, while conchiolin Δ14C values are impacted by variable relative contributions of young and old organic matter. Environmental samples indicate a significantly large difference in Δ14C among sources, from –127‰ in particulate organic matter to approximately +15‰ in DIC. Conchiolin is significantly depleted in 14C relative to other tissue types, by as much as 56.6‰, posing a major obstacle to the use of conchiolin as an alternative material for radiocarbon dating.
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White, Richard Allen, Sarah A. Soles, Allyson L. Brady, Gordon Southam, Darlene S. S. Lim, and Greg F. Slater. "Biosignatures Associated with Freshwater Microbialites." Life 10, no. 5 (May 15, 2020): 66. http://dx.doi.org/10.3390/life10050066.
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Freshwater microbialites (i.e., lithifying microbial mats) are quite rare in northern latitudes of the North American continent, with two lakes (Pavilion and Kelly Lakes) of southeastern BC containing a morphological variety of such structures. We investigated Kelly Lake microbialites using carbon isotope systematics, phospholipid fatty acids (PLFAs) and quantitative PCR to obtain biosignatures associated with microbial metabolism. δ13CDIC values (mean δ13CDIC −4.9 ± 1.1‰, n = 8) were not in isotopic equilibrium with the atmosphere; however, they do indicate 13C-depleted inorganic carbon into Kelly Lake. The values of carbonates on microbialite surfaces (δ13C) fell within the range predicted for equilibrium precipitation from ambient lake water δ13CDIC (−2.2 to −5.3‰). Deep microbialites (26 m) had an enriched δ13Ccarb value of −0.3 ± 0.5‰, which is a signature of photoautotrophy. The deeper microbialites (>20 m) had higher biomass estimates (via PLFAs), and a greater relative abundance of cyanobacteria (measured by 16S copies via qPCR). The majority of PLFAs constituted monounsaturated and saturated PLFAs, which is consistent with gram-negative bacteria, including cyanobacteria. The central PLFA δ13C values were highly depleted (−9.3 to −15.7‰) relative to δ13C values of bulk organic matter, suggesting a predominance of photoautotrophy. A heterotrophic signature was also detected via the depleted iso- and anteiso-15:0 lipids (−3.2 to −5.2‰). Based on our carbonate isotopic biosignatures, PLFA, and qPCR measurements, photoautotrophy is enriched in the microbialites of Kelly Lake. This photoautotrophy enrichment is consistent with the microbialites of neighboring Pavilion Lake. This indication of photoautotrophy within Kelly Lake at its deepest depths raises new insights into the limits of measurable carbonate isotopic biosignatures under light and nutrient limitations.
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Luo, Shanglin, Mingfang Huo, Qin Xue, and Guohua Xie. "Numerical Simulation of S-Shaped Current–Voltage Curves Induced by Electron Traps in Inverted Organic Photovoltaics." International Journal of Molecular Sciences 23, no. 4 (February 12, 2022): 2039. http://dx.doi.org/10.3390/ijms23042039.
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Organic photovoltaics (OPVs) differ from their inorganic counterparts because of inevitable electronic disorders and structural heterogeneity. Charge carrier traps are inevitable in organic semiconductors. A common failure mechanism of OPVs is the development of an S-shaped current density–voltage characteristic (J-V curve). Herein, we focus on investigating the underlying physical mechanism of S-shaped deformation of J-V curve of the inverted organic photovoltaic devices with bulk-heterojunction, proven by experiments with the n-doped electron extraction layer and numerical simulations assuming electron traps (0.1 eV deeper) in the electron extraction layer. The numerical simulations are quite consistent with the experimental results. In addition, the open circuit voltage induced by S-kink is exemplified to be enhanced after removing the electron traps in the interlayer by introducing a dopant of cesium carbonate.
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Yin, Hang, Jing Dou, Liviana Klein, Ulrich K. Krieger, Alison Bain, Brandon J. Wallace, Thomas C. Preston, and Andreas Zuend. "Extension of the AIOMFAC model by iodine and carbonate species: applications for aerosol acidity and cloud droplet activation." Atmospheric Chemistry and Physics 22, no. 2 (January 21, 2022): 973–1013. http://dx.doi.org/10.5194/acp-22-973-2022.
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Abstract. Iodine and carbonate species are important components in marine and dust aerosols, respectively. The non-ideal interactions between these species and other inorganic and organic compounds within aqueous particle phases affect hygroscopicity, acidity, and gas–particle partitioning of semivolatile components. In this work, we present an extended version of the Aerosol Inorganic–Organic Mixtures Functional groups Activity Coefficients (AIOMFAC) model by incorporating the ions I−, IO3-, HCO3-, CO32-, OH−, and CO2(aq) as new species. First, AIOMFAC ion interaction parameters for aqueous solutions were determined based on available thermodynamic data, such as water activity, mean molal activity coefficients, solubility, and vapor–liquid equilibrium measurements. Second, the interaction parameters for the new ions and various organic functional groups were optimized based on experimental data or, where data are scarce, alternative estimation methods such as multiple linear regression or a simple substitution by analogy approach. Additional bulk water activity and electrodynamic balance measurements were carried out to augment the database for the AIOMFAC parameter fit. While not optimal, we show that the use of alternative parameter estimation methods enables physically sound predictions and offers the benefit of a more broadly applicable model. Our implementation of the aqueous carbonate–bicarbonate–CO2(aq) system accounts for the associated temperature-dependent dissociation equilibria explicitly and enables closed- or open-system computations with respect to carbon dioxide equilibration with the gas phase. We discuss different numerical approaches for solving the coupled equilibrium conditions and highlight critical considerations when extremely acidic or basic mixtures are encountered. The fitted AIOMFAC model performance for inorganic aqueous systems is considered excellent over the whole range of mixture compositions where reference data are available. Moreover, the model provides physically meaningful predictions of water activity under highly concentrated conditions. For organic–inorganic mixtures involving new species, the model–measurement agreement is found to be good in most cases, especially at equilibrium relative humidities above ∼ 70 %; reasons for deviations are discussed. Several applications of the extended model are shown and discussed, including the effects of ignoring the auto-dissociation of water in carbonate systems, the effects of mixing bisulfate and bicarbonate compounds in closed- or open-system scenarios on pH and solution speciation, and the prediction of critical cloud condensation nucleus activation of NaI or Na2CO3 particles mixed with suberic acid.
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Geilfus, N. X., R. J. Galley, O. Crabeck, T. Papakyriakou, J. Landy, J. L. Tison, and S. Rysgaard. "Inorganic carbon dynamics of melt pond-covered first year sea ice in the Canadian Arctic." Biogeosciences Discussions 11, no. 5 (May 23, 2014): 7485–519. http://dx.doi.org/10.5194/bgd-11-7485-2014.
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Abstract. Melt pond formation is a common feature of the spring and summer Arctic sea ice. However, the role of the melt ponds formation and the impact of the sea ice melt on both the direction and size of CO2 flux between air and sea is still unknown. Here we describe the CO2-carbonate chemistry of melting sea ice, melt ponds and the underlying seawater associated with measurement of CO2 fluxes across first year landfast sea ice in the Resolute Passage, Nunavut, in June 2012. Early in the melt season, the increase of the ice temperature and the subsequent decrease of the bulk ice salinity promote a strong decrease of the total alkalinity (TA), total dissolved inorganic carbon (TCO2) and partial pressure of CO2 (pCO2) within the bulk sea ice and the brine. Later on, melt pond formation affects both the bulk sea ice and the brine system. As melt ponds are formed from melted snow the in situ melt pond pCO2 is low (36 μatm). The percolation of this low pCO2 melt water into the sea ice matrix dilutes the brine resulting in a strong decrease of the in situ brine pCO2 (to 20 μatm). As melt ponds reach equilibrium with the atmosphere, their in situ pCO2 increase (up to 380 μatm) and the percolation of this high concentration pCO2 melt water increase the in situ brine pCO2 within the sea ice matrix. The low in situ pCO2 observed in brine and melt ponds results in CO2 fluxes of −0.04 to −5.4 mmol m–2 d–1. As melt ponds reach equilibrium with the atmosphere, the uptake becomes less significant. However, since melt ponds are continuously supplied by melt water their in situ pCO2 still remains low, promoting a continuous but moderate uptake of CO2 (~ −1mmol m–2 d–1). The potential uptake of atmospheric CO2 by melting sea ice during the Arctic summer has been estimated from 7 to 16 Tg of C ignoring the role of melt ponds. This additional uptake of CO2 associated to Arctic sea ice needs to be further explored and considered in the estimation of the Arctic Ocean's overall CO2 budget.
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Sengupta, Mita, David Jacobi, Yazeed Altowairqi, and Salma Al-Sinan. "Quantifying the links between geochemical and geophysical properties of organic-rich carbonate mudrocks." Leading Edge 38, no. 12 (December 2019): 914–22. http://dx.doi.org/10.1190/tle38120914.1.
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Source rocks possess complex heterogeneous matrices with soft organic matter, consisting mainly of kerogen, interspersed within a stiff inorganic mineral framework that varies in composition. There is not a clear understanding nor adequate knowledge of how geochemical properties influence the rock physics, especially when predicting a seismic response. While many attempts have been made to use seismic to empirically quantify these properties for the purpose of exploration, those attempts have often failed due to the complexity of the elastic properties of kerogen and the laminated geometry of the rock. This is due primarily to uncertainty over how these properties change with maturity as a result of burial and subsequent uplift. Therefore, knowledge of (1) the elastic properties of kerogen, (2) the amount and geometric distribution of organic matter within the rock matrix, and (3) the impact of kerogen maturity on its elastic properties is needed to predict a seismic response. An elastic property modeling method has been developed to address this challenge based on the integration of high-resolution microscopy, geochemical analysis, and velocity measurements. Using this approach, endmembers are obtained that allow for building rock-physics models that can predict elastic uncertainty from mineral heterogeneity and estimate the elastic properties of organic matter. Digital images, geochemical data, and velocity measurements coupled with maturity modeling suggest that bulk and shear softening of kerogen can help distinguish between maturity-induced seismic responses.
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Liu, Zhaoming, Zhisen Zhang, Zheming Wang, Biao Jin, Dongsheng Li, Jinhui Tao, Ruikang Tang, and James J. De Yoreo. "Shape-preserving amorphous-to-crystalline transformation of CaCO3 revealed by in situ TEM." Proceedings of the National Academy of Sciences 117, no. 7 (February 3, 2020): 3397–404. http://dx.doi.org/10.1073/pnas.1914813117.
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Organisms use inorganic ions and macromolecules to regulate crystallization from amorphous precursors, endowing natural biominerals with complex morphologies and enhanced properties. The mechanisms by which modifiers enable these shape-preserving transformations are poorly understood. We used in situ liquid-phase transmission electron microscopy to follow the evolution from amorphous calcium carbonate to calcite in the presence of additives. A combination of contrast analysis and infrared spectroscopy shows that Mg ions, which are widely present in seawater and biological fluids, alter the transformation pathway in a concentration-dependent manner. The ions bring excess (structural) water into the amorphous bulk so that a direct transformation is triggered by dehydration in the absence of morphological changes. Molecular dynamics simulations suggest Mg-incorporated water induces structural fluctuations, allowing transformation without the need to nucleate a separate crystal. Thus, the obtained calcite retains the original morphology of the amorphous state, biomimetically achieving the morphological control of crystals seen in biominerals.
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Geilfus, N. X., J. L. Tison, S. F. Ackley, R. J. Galley, S. Rysgaard, L. A. Miller, and B. Delille. "Sea ice <i>p</i>CO<sub>2</sub> dynamics and air–ice CO<sub>2</sub> fluxes during the Sea Ice Mass Balance in the Antarctic (SIMBA) experiment – Bellingshausen Sea, Antarctica." Cryosphere 8, no. 6 (December 20, 2014): 2395–407. http://dx.doi.org/10.5194/tc-8-2395-2014.
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Abstract. Temporal evolution of pCO2 profiles in sea ice in the Bellingshausen Sea, Antarctica, in October 2007 shows physical and thermodynamic processes controls the CO2 system in the ice. During the survey, cyclical warming and cooling strongly influenced the physical, chemical, and thermodynamic properties of the ice cover. Two sampling sites with contrasting characteristics of ice and snow thickness were sampled: one had little snow accumulation (from 8 to 25 cm) and larger temperature and salinity variations than the second site, where the snow cover was up to 38 cm thick and therefore better insulated the underlying sea ice. We show that each cooling/warming event was associated with an increase/decrease in the brine salinity, total alkalinity (TA), total dissolved inorganic carbon (TCO2), and in situ brine and bulk ice CO2 partial pressures (pCO2). Thicker snow covers reduced the amplitude of these changes: snow cover influences the sea ice carbonate system by modulating the temperature and therefore the salinity of the sea ice cover. Results indicate that pCO2 was undersaturated with respect to the atmosphere both in the in situ bulk ice (from 10 to 193 μatm) and brine (from 65 to 293 μatm), causing the sea ice to act as a sink for atmospheric CO2 (up to 2.9 mmol m−2 d−1), despite supersaturation of the underlying seawater (up to 462 μatm).
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Geilfus, N. X., J. L. Tison, S. F. Ackley, S. Rysgaard, L. A. Miller, and B. Delille. "Impact of snow cover on CO<sub>2</sub> dynamics in Antarctic pack ice." Cryosphere Discussions 8, no. 3 (June 23, 2014): 3263–95. http://dx.doi.org/10.5194/tcd-8-3263-2014.
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Abstract. Temporal evolution of pCO2 profiles in sea ice in the Bellingshausen Sea, Antarctica, in October 2007 shows that the CO2 system in the ice was primarily controlled by physical and thermodynamic processes. During the survey, a succession of warming and cold events strongly influenced the physical, chemical and thermodynamic properties of the ice cover. Two sampling sites with contrasting characteristics of ice and snow thickness were sampled: one had little snow accumulation (from 8 to 25 cm) and larger temperature and salinity variations than the second site, where the snow cover was up to 38 cm thick and therefore better insulated the underlying sea ice. We confirm that each cooling/warming event was associated with an increase/decrease in the brine salinity, total alkalinity (TA), total dissolved inorganic carbon (TCO2), and in situ brine and bulk ice CO2 partial pressures (pCO2). Thicker snow covers muted these changes, suggesting that snow influences changes in the sea ice carbonate system through its impact on the temperature and salinity of the sea ice cover. During this survey, pCO2 was undersaturated with respect to the atmosphere both in situ, in the bulk ice (from 10 to 193 μatm), and in the brine (from 65 to 293 μatm), and the ice acted as a sink for atmospheric CO2 (up to 2.9 mmol m−2 d−1), despite the underlying supersaturated seawater (up to 462 μatm).
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Regenberg, M., D. Nürnberg, J. Schönfeld, and G. J. Reichart. "Early diagenetic overprint in Caribbean sediment cores and its effect on the geochemical composition of planktonic foraminifera." Biogeosciences 4, no. 6 (November 12, 2007): 957–73. http://dx.doi.org/10.5194/bg-4-957-2007.
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Abstract. Early diagenetic features are noticed in the vicinity of carbonate platforms. Planktonic foraminifera of two tropical Atlantic deep-sea sediment cores show the strict relation between micro-scale euhydral crystallites of inorganic precipitates, higher oxygen isotope values and Mg/Ca ratios, and lower Sr/Ca ratios than expected for their pelagic environment in the time interval of ~100 000–550 000 calendar years before present. Laser ablation Mg/Ca (Sr/Ca) of crystallite-bearing foraminiferal chamber walls revealed 4–6 times elevated (2–3 times depleted) ratios, when ablating the diagenetic overgrowth. Crystalline overgrowth in proportion of 10–20% are estimated to cause the observed geochemical alteration. The extent of foraminiferal Mg/Ca alteration, moreover, seems to be controlled by the composition of the bulk sediment, especially the content of high-magnesium calcite. Anomalous ratios of >6 mmol/mol only occur, when high-magnesium calcite has dissolved within the sediment. The older parts (back to ~800 kyrs) of the records are characterized by similar trends of Mg/Ca and Sr/Ca. We discuss possible scenarios to accommodate the obtained geochemical information.
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Regenberg, M., D. Nürnberg, J. Schönfeld, and G. J. Reichart. "Early diagenetic overprint in Caribbean sediment cores and its effect on the geochemical composition of planktonic foraminifera." Biogeosciences Discussions 4, no. 4 (July 4, 2007): 2179–213. http://dx.doi.org/10.5194/bgd-4-2179-2007.
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Abstract. Early diagenetic features are noticed in the vicinity of carbonate platforms. Planktonic foraminifera of two tropical Atlantic deep-sea sediment cores show the strict relation between micro-scale euhydral crystallites of inorganic precipitates, higher oxygen isotope values and Mg/Ca ratios, and lower Sr/Ca ratios than expected for their pelagic environment in the time interval of ~100 000–550 000 calendar years before present. Laser ablation Mg/Ca (Sr/Ca) of crystallite-bearing foraminiferal chamber walls revealed 4–6 times elevated (2–3 times depleted) ratios, when ablating the diagenetic overgrowth. Crystalline overgrowth in proportions of 10–20% are estimated to cause the observed geochemical alteration. The extent of foraminiferal Mg/Ca alteration, moreover, seems to be controlled by the composition of the bulk sediment, especially the content of high-magnesium calcite. Anomalous ratios of >6 mmol/mol only occur, when high-magnesium calcite has dissolved within the sediment. The older parts (back to ~800 kyrs) of the records are characterized by similar trends of Mg/Ca and Sr/Ca. We discuss possible scenarios to accommodate the obtained geochemical information.
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Dong, Lili, and Meng Kou. "Soil Aggregate Stability and Carbon Density in Three Plantations in the Loess Plateau, China." Forests 13, no. 7 (July 13, 2022): 1096. http://dx.doi.org/10.3390/f13071096.
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Afforestation plays an important role in mitigating soil erosion and improving soil quality in the Loess Plateau. However, there is no consistent conclusion about the effect of tree species on soil properties. Robinia pseudoacacia, Pinus tabulaeformis, and Malus pumila plantations were selected as the research objects. Soil indices such as the content of soil organic carbon (SOC) and inorganic carbon (SIC), carbon density, soil aggregate stability, and bulk density were selected to study the effects of different plantations on soil properties. The mean weight diameter (MWD) was calculated to evaluate soil aggregate stability. The results showed that: (1) MWD of R. pseudoacacia was 22%–67% lower than that of P. tabuliformis across the 0–80 cm soil layers. MWD of M. pumila was 27%–45% and 57%–78% lower than that of R. pseudoacacia and P. tabuliformis across 0–50 cm layers. (2) SOC of P. tabuliformis was 61%–127% and 67%–148% higher than that of R. pseudoacacia and M. pumila, respectively, while SIC was 55%–82% and 12%–14% lower than that of R. pseudoacacia and M. pumila. (3) Soil carbon density, including soil organic carbon density and inorganic carbon density, of P. tabuliformis was 36%–49% and 3%–31% lower than that of R. pseudoacacia and M. pumila, respectively. (4) Aggregate organic carbon increased with increasing aggregate size, while inorganic carbon decreased. Water-stable aggregates with larger sizes had higher soil organic carbon and lower carbonate calcium. (5) The inorganic carbon in soil was both a binder and a dispersant of soil aggregates, which depends on its content. P. tabuliformis should be planted in the semi-arid area of the Loess Plateau in China, because this species was able to increase soil organic matter and improve soil structure compared with the other two species.
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Cuevas, Ignacio Andrés, Funeka Nkosi, Kristina Edstrom, and Mario Valvo. "Handling the Carbonates: Interfacial Engineering of Garnet Electrolytes." ECS Meeting Abstracts MA2022-01, no. 55 (July 7, 2022): 2262. http://dx.doi.org/10.1149/ma2022-01552262mtgabs.
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Since Murugan et al. [1] discovered the Li7La3Zr2O12 (LLZO) inorganic solid state electrolyte composition, extensive work has been devoted to understanding its behavior and optimizing its structural and compositional features. Although improvement of its bulk and composition has allowed reaching ionic conductivities roughly in the range of mS/cm, much more work is needed in terms of assembling actual all-solid-state batteries by using this material. In this work, we aim at a two fold improvement of the LLZO surface contact with the electrodes by not only creating a new layer on the surface of this ceramic electrolyte, but also by converting the non-conductive lithium carbonate layer [2] that forms on the LLZO surface upon air exposure. Through this rational approach, we expect a chemically relevant surface transformation, linked to a change in the electrochemical performance, via facilitation of the ionic transport through the surface of the ceramic pellet and an improved interface contact. LLZO pellets are treated with boric acid [3] in order to form borate species on their surface, substituting totally or partially the carbonate species that hinder ionic conductivity on the surface. The influence of both atmospheric exposure, treatment and stirring on the resulting pellets is tracked via Raman, XPS and XRD analyses to obtain a comparison and assess the impact of these factors. The final effect of the boric acid treatment is checked via SEM-EDX and electrochemical impedance spectroscopy (EIS) analyses, to determine both morphological and electrochemical effects of the surface modification, which will further influence the interfacial characteristics of the pellet with both electrodes, with a special focus on the lithium side. Our results show an improvement of the surface properties of the pellets, due to the morphological and chemical modification of the LLZO surface, without affecting the bulk properties. [1] Ramaswamy Murugan, Venkataraman Thangadurai, and Werner Weppner. “Fast lithium ion conduction in garnet-type Li7La 3Zr2O12”. In: Angewandte Chemie - International Edition 46.41 (2007), pp. 7778–7781. issn: 14337851. doi: 10.1002/anie.200701144. [2] Asma Sharafi et al. “Impact of air exposure and surface chemistry on Li-Li7La3Zr2O12 interfacial resistance”. In: Journal of Materials Chemistry A 5.26 (2017), pp. 13475–13487. issn: 20507496. doi: 10.1039/c7ta03162a. [3] Yadong Ruan et al. “Acid induced conversion towards a robust and lithiophilic interface for Li-Li7La3Zr2O12 solid-state batteries”. In: Journal of Materials Chemistry A 7.24 (2019), pp. 14565–14574. issn: 20507496. doi: 10.1039/c9ta01911a. Figure 1
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Geilfus, N. X., R. J. Galley, O. Crabeck, T. Papakyriakou, J. Landy, J. L. Tison, and S. Rysgaard. "Inorganic carbon dynamics of melt-pond-covered first-year sea ice in the Canadian Arctic." Biogeosciences 12, no. 6 (March 31, 2015): 2047–61. http://dx.doi.org/10.5194/bg-12-2047-2015.
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Abstract. Melt pond formation is a common feature of spring and summer Arctic sea ice, but the role and impact of sea ice melt and pond formation on both the direction and size of CO2 fluxes between air and sea is still unknown. Here we report on the CO2–carbonate chemistry of melting sea ice, melt ponds and the underlying seawater as well as CO2 fluxes at the surface of first-year landfast sea ice in the Resolute Passage, Nunavut, in June 2012. Early in the melt season, the increase in ice temperature and the subsequent decrease in bulk ice salinity promote a strong decrease of the total alkalinity (TA), total dissolved inorganic carbon (TCO2) and partial pressure of CO2 (pCO2) within the bulk sea ice and the brine. As sea ice melt progresses, melt ponds form, mainly from melted snow, leading to a low in situ melt pond pCO2 (36 μatm). The percolation of this low salinity and low pCO2 meltwater into the sea ice matrix decreased the brine salinity, TA and TCO2, and lowered the in situ brine pCO2 (to 20 μatm). This initial low in situ pCO2 observed in brine and melt ponds results in air–ice CO2 fluxes ranging between −0.04 and −5.4 mmol m−2 day−1 (negative sign for fluxes from the atmosphere into the ocean). As melt ponds strive to reach pCO2 equilibrium with the atmosphere, their in situ pCO2 increases (up to 380 μatm) with time and the percolation of this relatively high concentration pCO2 meltwater increases the in situ brine pCO2 within the sea ice matrix as the melt season progresses. As the melt pond pCO2 increases, the uptake of atmospheric CO2 becomes less significant. However, since melt ponds are continuously supplied by meltwater, their in situ pCO2 remains undersaturated with respect to the atmosphere, promoting a continuous but moderate uptake of CO2 (~ −1 mmol m−2 day−1) into the ocean. Considering the Arctic seasonal sea ice extent during the melt period (90 days), we estimate an uptake of atmospheric CO2 of −10.4 Tg of C yr−1. This represents an additional uptake of CO2 associated with Arctic sea ice that needs to be further explored and considered in the estimation of the Arctic Ocean's overall CO2 budget.
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Su, Xiao-li, Li-hua Nie, and Shou-zhuo Yao. "A novel gas-diffusion/flow-injection system coupled with a bulk acoustic wave impedance sensor for total inorganic carbonate and its application to determination of total inorganic and total organic carbon in waters." Analytica Chimica Acta 349, no. 1-3 (August 1997): 143–51. http://dx.doi.org/10.1016/s0003-2670(97)00250-x.
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Kimball, Justine, Robert Eagle, and Robert Dunbar. "Carbonate “clumped” isotope signatures in aragonitic scleractinian and calcitic gorgonian deep-sea corals." Biogeosciences 13, no. 23 (December 12, 2016): 6487–505. http://dx.doi.org/10.5194/bg-13-6487-2016.
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Abstract. Deep-sea corals are a potentially valuable archive of the temperature and ocean chemistry of intermediate and deep waters. Living in near-constant temperature, salinity, and pH and having amongst the slowest calcification rates observed in carbonate-precipitating biological organisms, deep-sea corals can provide valuable constraints on processes driving mineral equilibrium and disequilibrium isotope signatures. Here we report new data to further develop “clumped” isotopes as a paleothermometer in deep-sea corals as well as to investigate mineral-specific, taxon-specific, and growth-rate-related effects. Carbonate clumped isotope thermometry is based on measurements of the abundance of the doubly substituted isotopologue 13C18O16O2 in carbonate minerals, analyzed in CO2 gas liberated on phosphoric acid digestion of carbonates and reported as Δ47 values. We analyzed Δ47 in live-collected aragonitic scleractinian (Enallopsammia sp.) and high-Mg calcitic gorgonian (Isididae and Coralliidae) deep-sea corals and compared results to published data for other aragonitic scleractinian taxa. Measured Δ47 values were compared to in situ temperatures, and the relationship between Δ47 and temperature was determined for each group to investigate taxon-specific effects. We find that aragonitic scleractinian deep-sea corals exhibit higher values than high-Mg calcitic gorgonian corals and the two groups of coral produce statistically different relationships between Δ47–temperature calibrations. These data are significant in the interpretation of all carbonate clumped isotope calibration data as they show that distinct Δ47–temperature calibrations can be observed in different materials recovered from the same environment and analyzed using the same instrumentation, phosphoric acid composition, digestion temperature and technique, CO2 gas purification apparatus, and data handling. There are three possible explanations for the origin of these different calibrations. The offset between the corals of different mineralogy is in the same direction as published theoretical predictions for the offset between calcite and aragonite although the magnitude of the offset is different. One possibility is that the deep-sea coral results reflect high-Mg and aragonite crystals attaining nominal mineral equilibrium clumped isotope signatures due to conditions of extremely slow growth. In that case, a possible explanation for the attainment of disequilibrium bulk isotope signatures and equilibrium clumped isotope signatures by deep-sea corals is that extraordinarily slow growth rates can promote the occurrence of isotopic reordering in the interfacial region of growing crystals. We also cannot rule out a component of a biological “vital effect” influencing clumped isotope signatures in one or both orders of coral. Based on published experimental data and theoretical calculations, these biological vital effects could arise from kinetic isotope effects due to the source of carbon used for calcification, temperature- and pH-dependent rates of CO2 hydration and/or hydroxylation, calcifying fluid pH, the activity of carbonic anhydrase, the residence time of dissolved inorganic carbon in the calcifying fluid, and calcification rate. A third possible explanation is the occurrence of variable acid digestion fractionation factors. Although a recent study has suggested that dolomite, calcite, and aragonite may have similar clumped isotope acid digestion fractionation factors, the influence of acid digestion kinetics on Δ47 is a subject that warrants further investigation.
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Kimball, J., R. E. Tripati, and R. Dunbar. "Carbonate "clumped" isotope signatures in aragonitic scleractinian and calcitic gorgonian deep-sea corals." Biogeosciences Discussions 12, no. 23 (December 4, 2015): 19115–65. http://dx.doi.org/10.5194/bgd-12-19115-2015.
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Abstract. Deep-sea corals are a potentially valuable archive of the temperature and ocean chemistry of intermediate and deep waters. Living in near constant temperature, salinity and pH, and having amongst the slowest calcification rates observed in carbonate-precipitating biological organisms, deep-sea corals can provide valuable constraints on processes driving mineral equilibrium and disequilibrium isotope signatures. Here we report new data to further develop "clumped" isotopes as a paleothermometer in deep-sea corals as well as to investigate mineral-specific, taxon-specific, and growth-rate related effects. Carbonate clumped isotope thermometry is based on measurements of the abundance of the doubly-substituted isotopologue 13C18O16O2 in carbonate minerals, analyzed in CO2 gas liberated on phosphoric acid digestion of carbonates and reported as Δ47 values. We analyzed Δ47 in live-collected aragonitic scleractinian (Enallopsammia sp.) and calcitic gorgonian (Isididae and Coralliidae) deep-sea corals, and compared results to published data for other aragonitic scleractinian taxa. Measured Δ47 values were compared to in situ temperatures and the relationship between Δ47 and temperature was determined for each group to investigate taxon-specific effects. We find that aragonitic scleractinian deep-sea corals exhibit higher values than calcitic gorgonian corals and the two groups of coral produce statistically different relationship between Δ47-temperature calibrations. These data are significant in the interpretation of all carbonate "clumped" isotope calibration data as they show that distinct Δ47-temperature calibrations can be observed in different materials recovered from the same environment and analyzed using the same instrumentation, phosphoric acid composition, digestion temperature and technique, CO2 gas purification apparatus, and data handling. There are three possible explanations for the origin of these different calibrations. The offset between the corals of different mineralogy is in the same direction as published theoretical predictions for the offset between calcite and aragonite, although the magnitude of the offset is different. One possibility is that the deep-sea coral results reflect that crystals may attain nominal mineral equilibrium clumped isotope signatures only under conditions of extremely slow growth. In that case, a possible explanation for the attainment of disequilibrium bulk isotope signatures and equilibrium clumped isotope signatures by deep-sea corals is that extraordinarily slow growth rates can promote the occurrence of isotopic reordering in the interfacial region of growing crystals. We also cannot rule out a component of a biological "vital-effect" influencing clumped isotope signatures in one or both orders of coral. Based on published experimental data and theoretical calculations, these biological "vital" effects could arise from kinetic isotope effects due to the source of carbon used for calcification, temperature- and pH-dependent rates of CO2 hydration and/or hydroxylation, calcifying fluid pH, the activity of carbonic anhydrase, the residence time of dissolved inorganic carbon in the calcifying fluid, and calcification rate. A third possible explanation is the occurrence of variable acid digestion fractionation factors. Although a recent study has suggested that dolomite, calcite, and aragonite may have similar clumped isotope acid digestion fractionation factors, the influence of acid digestion kinetics on Δ47 is a subject that warrants further investigation.
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Motegi, C., T. Tanaka, J. Piontek, C. P. D. Brussaard, J. P. Gattuso, and M. G. Weinbauer. "Effect of CO<sub>2</sub> enrichment on bacterial metabolism in an Arctic fjord." Biogeosciences 10, no. 5 (May 15, 2013): 3285–96. http://dx.doi.org/10.5194/bg-10-3285-2013.
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Abstract. The anthropogenic increase of carbon dioxide (CO2) alters the seawater carbonate chemistry, with a decline of pH and an increase in the partial pressure of CO2 (pCO2). Although bacteria play a major role in carbon cycling, little is known about the impact of rising pCO2 on bacterial carbon metabolism, especially for natural bacterial communities. In this study, we investigated the effect of rising pCO2 on bacterial production (BP), bacterial respiration (BR) and bacterial carbon metabolism during a mesocosm experiment performed in Kongsfjorden (Svalbard) in 2010. Nine mesocosms with pCO2 levels ranging from ca. 180 to 1400 μatm were deployed in the fjord and monitored for 30 days. Generally BP gradually decreased in all mesocosms in an initial phase, showed a large (3.6-fold average) but temporary increase on day 10, and increased slightly after inorganic nutrient addition. Over the wide range of pCO2 investigated, the patterns in BP and growth rate of bulk and free-living communities were generally similar over time. However, BP of the bulk community significantly decreased with increasing pCO2 after nutrient addition (day 14). In addition, increasing pCO2 enhanced the leucine to thymidine (Leu : TdR) ratio at the end of experiment, suggesting that pCO2 may alter the growth balance of bacteria. Stepwise multiple regression analysis suggests that multiple factors, including pCO2, explained the changes of BP, growth rate and Leu : TdR ratio at the end of the experiment. In contrast to BP, no clear trend and effect of changes of pCO2 was observed for BR, bacterial carbon demand and bacterial growth efficiency. Overall, the results suggest that changes in pCO2 potentially influence bacterial production, growth rate and growth balance rather than the conversion of dissolved organic matter into CO2.
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Amthor, Joachim E., Karl Ramseyer, Tom Faulkner, and Peter Lucas. "Stratigraphy and sedimentology of a chert reservoir at the Precambrian-Cambrian Boundary: the Al Shomou Silicilyte, South Oman Salt Basin." GeoArabia 10, no. 2 (April 1, 2005): 89–122. http://dx.doi.org/10.2113/geoarabia100289.
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ABSTRACT The Al Shomou Silicilyte is a unique source and reservoir rock found in the South Oman Salt Basin, where up to 400 m thick and several kilometers wide slabs of silicilyte are entrapped in salt domes at depths of 4 to 5 km. Discovered in the early 1990s, the play is characterized by light and sour oil, high overpressures (19.8 kPa/m), and a high-porosity, low-permeability microcrystalline silica matrix rich in organic matter, deposited around the Precambrian-Cambrian boundary. The palaeogeographic setting during the Al Shomou Silicilyte deposition was a restricted, marine intra-cratonic basin, surrounded by carbonate platforms. The basin was most likely segmented into structural highs and lows, with potential relief of more than 200 m. The deposits of the Al Shomou Silicilyte are stratigraphically ‘sandwiched’ by two regionally extensive shale units, the underlying ‘U’-Shale Formation and the overlying Thuleilat Shale Member. The basinal Al Shomou Silicilyte and the time-equivalent platform carbonates were deposited during a TST to HST in sea-level characterised by reduced siliciclastic input. Silicilyte formation was replaced by the regionally extensive lower Thuleilat Shale and Thamoud Carbonate. The Al Shomou Silicilyte is typically organic-rich, finely laminated and consists of 80–90% microcrystalline quartz with a crystal-size of 2–3 microns. Commonly, the silica crystals form sheet-like aggregates with high intercrystalline microporosity (up to 30%). Other authigenic phases in the silicilyte are pyrite, apatite, magnesite and illite/smectite clay minerals. Minor silt- and sand-sized detrital components are mica/illite flakes, K-feldspar, quartz and sedimentary rock fragments. The organic material averages 7% of the bulk rock volume and is finely disseminated and/or concentrated in laminae. No identifiable macro- or microfossils have been found to-date in the silicilyte. The textural and chemical characteristics suggest formation in a reducing, probably anoxic environment below wave base. The 300–400 m thickness and uniform character of the silicilyte indicate relatively stable conditions during deposition. The lack of recognizable biogenic components and only traces of detrital particles, suggest that the silicilyte is mostly composed of chemically formed silica. The microcrystalline silica could well be the result of a rapid inorganic nucleation of silica gel. The large volumes of silica necessary for silicilyte formation require a silica reservoir of reasonable magnitude, i.e. sea water. A model with a stratified water column is proposed, in which the oxic surface waters probably represented the site of organic productivity and carbonate deposition, and the deeper water at the thermocline/chemocline, the site of silica formation and bacterial mat growth. Silica gel formation may well have been linked to the biological cycle, i.e. mediated by sulfate-reducing bacteria (chemoautotrophs). Comparison with other siliceous deposits indicates that there are no known analogues. Models proposed for banded iron formations are probably the closest approximation to the type of processes involved in the formation of the silicilyte. Given its apparent chronostratigraphic position at the Precambrian-Cambrian boundary, it may well represent a global deepwater facies related to key events which are suggestive of extinction and faunal turnover at the Precambrian-Cambrian boundary.
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Dalal, RC, and RJ Mayer. "Long term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland. I. Overall changes in soil properties and trends in winter cereal yields." Soil Research 24, no. 2 (1986): 265. http://dx.doi.org/10.1071/sr9860265.
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Changes in fertility of some southern Queensland soils resulting from extended periods of cultivation are presented, together with trends in yields of winter cereals on these soils. Six major soils of the cereal-belt, cropped for maximum periods of 20-70 years were examined. These were: Black earths, Waco soil; grey, brown and red clays (brigalow), Langlands-Logie soil; grey, brown and red clays (poplar box), Cecilvale soil; grey, brown and red clays (belah), Billa Billa soil; grey, brown and red clays (coolibah), Thallon soil; red earths, Riverview soil. Organic matter and its constituents, especially total organic C, organic C in the light fraction, total N and mineralizable N, were affected most by cultivation, showing decreases of 19-67% overall. Other soil properties probably associated with organic matter, including bulk density and DTPA (diethylenetriaminepentaacetic acid) extractable manganese, were also significantly affected by cultivation in all soils. Soil properties affected least by cultivation were concentrations of inorganic phosphorus, total and exchangeable potassium, calcium carbonate, and dithionite extractable iron and aluminium. Most other soil properties studied (organic P, total sulfur, pH, exchangeable magnesium and sodium, exchangeable sodium percentage, and oxalate-extractable iron and aluminium) were affected by cultivation in at least four soils. Four factors accounted for 70% of the total variation among the 45 soil properties considered. They appeared to represent organic matter, clay colloids, iron and aluminium oxides, and soluble salts. Dry matter yield and/or N uptake of winter cereal crops (wheat and barley) measured in 1983 showed significant decreasing trends with period of cultivation in all soils.
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Padhan, Dhaneshwar, A. K. Pradhan, Mahasweta Chakraborty, and Arup Sen. "Assessment of the effects of land use pattern on distribution of sulphur fractions in soil." Journal of Applied and Natural Science 8, no. 3 (September 1, 2016): 1685–91. http://dx.doi.org/10.31018/jans.v8i3.1023.
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In the present investigation, various forms of sulphur (S) viz., total S, organic S, inorganic S and available S were estimated in soils under four different land uses viz., Rice-rice, rice-green gram, mango orchard and a fallow. Soils samples were taken up to a profile depth of 0.60m at 3 depths i.e. 0-0.20m, 0.20-0.40m and 0.40-0.60m. Thesoils were found to be slightly acidic to moderately acidic in reaction (5.83-6.59), showing an increase along the depth irrespective of the land use pattern. Soil organic carbon (SOC) content (mean 5.5 gkg-1) was found well above the low level of SOC in soils. Calcium carbonate content, bulk density and clay content of soils didn’t maintain any definite pattern along the depth. All forms of S were found to decrease along depth irrespective of the land use patterns. The available S content ranged from 12.2 to 21.4mgkg-1 of soils. The relative preponderance of all the forms of S followed the order: mango orchard> fallow> rice-rice> rice-green gram. On an average organic S and available S fractions constituted 93 and 6 per cent of total S respectively. A correlation matrix revealed that all the forms of S maintained a significant positive correlation with SOC content while a negative correlation with pH of the soils. The results of the study will be useful in managing the different fractions of S in soils in order to maintain its availability well above the critical level.
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Wu, Daidai, Tiantian Sun, Rui Xie, Mengdi Pan, Xuegang Chen, Ying Ye, Lihua Liu, and Nengyou Wu. "Characteristics of Authigenic Minerals around the Sulfate-Methane Transition Zone in the Methane-Rich Sediments of the Northern South China Sea: Inorganic Geochemical Evidence." International Journal of Environmental Research and Public Health 16, no. 13 (June 28, 2019): 2299. http://dx.doi.org/10.3390/ijerph16132299.
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Sediments at marine cold seep areas provide potential archives of past fluid flow, which allow insights into the evolution of past methane seepage activities. However, signals for anaerobic oxidation of methane (AOM) might be obscured in bulk sediments in cold-seep settings due to several factors, especially flood and turbidite deposition. Comprehensive inorganic data were gathered in this study to explore the availability of related records at cold seeps and to provide insights into the evolution of past methane seepage activities. Sediments collected from the site 973-4 in the Taixinan Basin on the northern slope of the South China Sea were characterized in terms of total carbon and sulfur, δ13C values of total organic carbon (δ13CTIC), δ34S values of chromium reducible sulfur (δ34SCRS), and foraminiferal oxygen and carbon isotopes. The results confirmed a strong correlation between formation of authigenic minerals and AOM. Moreover, the 34S enrichments and abundant chromium reducible sulfur (CRS) contents in the authigenic sulfides in the sulfate–methane transition zone (SMTZ) within 619–900 cm below seafloor (cmbsf) reflected past high methane fluxes supported by constant methane seepages. Lithological distribution and AMS (Accelerator Mass Spectra) 14C dating of planktonic foraminifera show that the turbidite (~35.14 ka) was related to a foraminifera-rich interval (Unit II: 440-619 cmbsf) and increased carbonate productivity during the last glacial maximum (LGM). Enrichment of Mo and U was observed accompanied by low contents of nutrient metals (Al, Ti, V, Ni, Fe, Mn, and Cu) in Unit II. The foraminifera-rich interval (Unit II) of cold seep sediments was probably linked to the phenomenon of inconsecutive sedimentary sequence due to the turbidites, which resulted in the lack of Fe, Mn, and Ba enrichment. There is no U enrichment but only Mo enrichment within Unit III, which might be related to H2S produced by AOM during the methane seepages. Based on the above results, it can be speculated that this area has experienced multiple-episodes of methane seep events. Further exploration of AOM should focus on the risks of rapid deposition, especially the impact of turbidity current on sediments.
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Paul, A. J., L. T. Bach, K. G. Schulz, T. Boxhammer, J. Czerny, E. P. Achterberg, D. Hellemann, et al. "Effect of elevated CO<sub>2</sub> on organic matter pools and fluxes in a summer Baltic Sea plankton community." Biogeosciences 12, no. 20 (October 28, 2015): 6181–203. http://dx.doi.org/10.5194/bg-12-6181-2015.
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Abstract. Ocean acidification is expected to influence plankton community structure and biogeochemical element cycles. To date, the response of plankton communities to elevated CO2 has been studied primarily during nutrient-stimulated blooms. In this CO2 manipulation study, we used large-volume (~ 55 m3) pelagic in situ mesocosms to enclose a natural summer, post-spring-bloom plankton assemblage in the Baltic Sea to investigate the response of organic matter pools to ocean acidification. The carbonate system in the six mesocosms was manipulated to yield average fCO2 ranging between 365 and ~ 1230 μatm with no adjustment of naturally available nutrient concentrations. Plankton community development and key biogeochemical element pools were subsequently followed in this nitrogen-limited ecosystem over a period of 7 weeks. We observed higher sustained chlorophyll a and particulate matter concentrations (~ 25 % higher) and lower inorganic phosphate concentrations in the water column in the highest fCO2 treatment (1231 μatm) during the final 2 weeks of the study period (Phase III), when there was low net change in particulate and dissolved matter pools. Size-fractionated phytoplankton pigment analyses indicated that these differences were driven by picophytoplankton (< 2 μm) and were already established early in the experiment during an initial warm and more productive period with overall elevated chlorophyll a and particulate matter concentrations. However, the influence of picophytoplankton on bulk organic matter pools was masked by high biomass of larger plankton until Phase III, when the contribution of the small size fraction (< 2 μm) increased to up to 90 % of chlorophyll a. In this phase, a CO2-driven increase in water column particulate carbon did not lead to enhanced sinking material flux but was instead reflected in increased dissolved organic carbon concentrations. Hence ocean acidification may induce changes in organic matter partitioning in the upper water column during the low-nitrogen summer period in the Baltic Sea.
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Adkins, Jess F., John D. Naviaux, Adam V. Subhas, Sijia Dong, and William M. Berelson. "The Dissolution Rate of CaCO3 in the Ocean." Annual Review of Marine Science 13, no. 1 (January 2021): 57–80. http://dx.doi.org/10.1146/annurev-marine-041720-092514.
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The dissolution of CaCO3 minerals in the ocean is a fundamental part of the marine alkalinity and carbon cycles. While there have been decades of work aimed at deriving the relationship between dissolution rate and mineral saturation state (a so-called rate law), no real consensus has been reached. There are disagreements between laboratory- and field-based studies and differences in rates for inorganic and biogenic materials. Rates based on measurements on suspended particles do not always agree with rates inferred from measurements made near the sediment–water interface of the actual ocean. By contrast, the freshwater dissolution rate of calcite has been well described by bulk rate measurements from a number of different laboratories, fit by basic kinetic theory, and well studied by atomic force microscopy and vertical scanning interferometry to document the processes at the atomic scale. In this review, we try to better unify our understanding of carbonate dissolution in the ocean via a relatively new, highly sensitive method we have developed combined with a theoretical framework guided by the success of the freshwater studies. We show that empirical curve fits of seawater data as a function of saturation state do not agree, largely because the curvature is itself a function of the thermodynamics. Instead, we show that models that consider both surface energetic theory and the complicated speciation of seawater and calcite surfaces in seawater are able to explain most of the most recent data.This new framework can also explain features of the historical data that have not been previously explained. The existence of a kink in the relationship between rate and saturation state, reflecting a change in dissolution mechanism, may be playing an important role in accelerating CaCO3 dissolution in key sedimentary environments.
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JARVIS, IAN, ANDREW S. GALE, HUGH C. JENKYNS, and MARTIN A. PEARCE. "Secular variation in Late Cretaceous carbon isotopes: a new δ13C carbonate reference curve for the Cenomanian–Campanian (99.6–70.6 Ma)." Geological Magazine 143, no. 5 (July 3, 2006): 561–608. http://dx.doi.org/10.1017/s0016756806002421.
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Carbon stable-isotope variation through the Cenomanian–Santonian stages is characterized using data for 1769 bulk pelagic carbonate samples collected from seven Chalk successions in England. The sections show consistent stratigraphic trends and δ13C values that provide a basis for high-resolution correlation. Positive and negative δ13C excursions and inflection points on the isotope profiles are used to define 72 isotope events. Key markers are provided by positive δ13C excursions of up to +2‰: the Albian/Cenomanian Boundary Event; Mid-Cenomanian Event I; the Cenomanian/Turonian Boundary Event; the Bridgewick, Hitch Wood and Navigation events of Late Turonian age; and the Santonian/Campanian Boundary Event. Isotope events are isochronous within a framework provided by macrofossil datum levels and bentonite horizons. An age-calibrated composite δ13C reference curve and an isotope event stratigraphy are constructed using data from the English Chalk. The isotope stratigraphy is applied to successions in Germany, France, Spain and Italy. Correlation with pelagic sections at Gubbio, central Italy, demonstrates general agreement between biostratigraphic and chemostratigraphic criteria in the Cenomanian–Turonian stages, confirming established relationships between Tethyan planktonic foraminiferal and Boreal macrofossil biozonations. Correlation of the Coniacian–Santonian stages is less clear cut: magnetostratigraphic evidence for placing the base of Chron 33r near the base of the Upper Santonian is in good agreement with the carbon-iso-tope correlation, but generates significant anomalies regarding the placement of the Santonian and Campanian stage boundaries with respect to Tethyan planktonic foraminiferal and nannofossil zones. Isotope stratigraphy offers a more reliable criterion for detailed correlation of Cenomanian–Santonian strata than biostratigraphy. With the addition of Campanian δ13C data from one of the English sections, a composite Cenomanian–Campanian age-calibrated reference curve is presented that can be utilized in future chemostratigraphic studies.The Cenomanian–Campanian carbon-isotope curve is remarkably similar in shape to supposedly eustatic sea-level curves: increasing δ13C values accompanying sea-level rise associated with transgression, and falling δ13C values characterizing sea-level fall and regression. The correlation between carbon isotopes and sea-level is explained by variations in epicontinental sea area affecting organic-matter burial fluxes: increasing shallow sea-floor area and increased accommodation space accompanying sea-level rise allowed more efficient burial of marine organic matter, with the preferential removal of 12C from the marine carbon reservoir. During sea-level fall, reduced seafloor area, marine erosion of previously deposited sediments, and exposure of basin margins led to reduced organic-carbon burial fluxes and oxidation of previously deposited organic matter, causing falling δ13C values. Additionally, drowning of carbonate platforms during periods of rapid sea-level rise may have reduced the global inorganic relative to the organic carbon flux, further enhancing δ13C values, while renewed platform growth during late transgressions and highstands prompted increased carbonate deposition. Variations in nutrient supply, changing rates of oceanic turnover, and the sequestration or liberation of methane from gas hydrates may also have played a role in controlling carbon-isotope ratios.
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Balfour, Victoria N., Stefan H. Doerr, and Peter R. Robichaud. "The temporal evolution of wildfire ash and implications for post-fire infiltration." International Journal of Wildland Fire 23, no. 5 (2014): 733. http://dx.doi.org/10.1071/wf13159.
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Changes in the properties of an ash layer with time may affect the amount of post-fire runoff, particularly by the formation of ash surface crusts. The formation of depositional crusts by ash have been observed at the pore and plot scales, but the causes and temporal evolution of ash layers and associated crusts have not yet been thoroughly investigated. In the long term, ash crusting effects will decrease as the ash layer is removed by wind and water erosion, but in the short term ash crusting could contribute to the observed changes in post-fire runoff. This research addresses these topics by studying the evolution over time of highly combusted ash layers from two high-severity wildfires that occurred in Montana in 2011. More specifically, this research was designed to assess the potential for ash crusts to form and thereby contribute to the observed decreases in infiltration after forest fires. Results indicate that high-combustion ash can evolve due to post-fire rainfall. Plots that exhibited a visible ash crust also displayed a significant decrease in effective porosity and hydraulic conductivity. These decreases in ash layer characteristics were attributed to raindrop compaction and ash hydration resulting in the formation of carbonate crystals, which decreased effective porosity and flow within the ash layer. During this same time period, inorganic carbon content more than doubled from 11 to 26% and bulk density significantly increased from 0.22 to 0.39gcm–3 on crusted plots. Although raindrop impact increased the robustness of the ash crust, mineralogical transformations must occur to produce a hydrologically relevant ash crust. These results indicate that post-fire rainfall is an important control on the properties of the ash layer after burning and on crust formation. The observed temporal changes indicate that the timing of ash sampling can alter the predictions as to whether the ash layer is effecting post-fire infiltration and runoff. Despite the reduction in infiltration capacity, the formation of post-fire ash crusts could prove beneficial to post-fire hazard mitigation by stabilising the ash layer, and reducing aeolian mixing and erosion.
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Conterosito, Eleonora, Luca Palin, Rocco Caliandro, Wouter van Beek, Dmitry Chernyshov, and Marco Milanesio. "CO2 adsorption in Y zeolite: a structural and dynamic view by a novel principal-component-analysis-assisted in situ single-crystal X-ray diffraction experiment." Acta Crystallographica Section A Foundations and Advances 75, no. 2 (February 6, 2019): 214–22. http://dx.doi.org/10.1107/s2053273318017618.
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The increasing efficiency of detectors and brightness of X-rays in both laboratory and large-scale facilities allow the collection of full single-crystal X-ray data sets within minutes. The analysis of these `crystallographic big data' requires new tools and approaches. To answer these needs, the use of principal component analysis (PCA) is proposed to improve the efficiency and speed of the analysis. Potentialities and limitations of PCA were investigated using single-crystal X-ray diffraction (XRD) data collected in situ on Y zeolite, in which CO2, acting as an active species, is thermally adsorbed while cooling from 300 to 200 K. For the first time, thanks to the high sensitivity of single-crystal XRD, it was possible to determine the sites where CO2 is adsorbed, the increase in their occupancy while the temperature is decreased, and the correlated motion of active species, i.e. CO2, H2O and Na+. PCA allowed identification and elimination of problematic data sets, and better understanding of the trends of the occupancies of CO2, Na+ and water. The quality of the data allowed for the first time calculation of the enthalpy (ΔH) and entropy (ΔS) of the CO2 adsorption by applying the van 't Hoff equation to in situ single-crystal data. The calculation of thermodynamic values was carried out by both traditional and PCA-based approaches, producing comparable results. The obtained ΔH value is significant and involves systems (CO2 and Y zeolite) with no toxicity, superb stability and chemical inertness. Such features, coupled with the absence of carbonate formation and framework inertness upon adsorption, were demonstrated for the bulk crystal by the single-crystal experiment, and suggest that the phenomenon can be easily reversed for a large number of cycles, with CO2 released on demand. The main advantages of PCA-assisted analysis reside in its speed and in the possibility of it being applied directly to raw data, possibly as an `online' data-quality test during data collection, without any a priori knowledge of the crystal structure.
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Nabiollahi, Kamal, Eskandari Heshmat, Amir Mosavi, Ruth Kerry, Mojtaba Zeraatpisheh, and Ruhollah Taghizadeh-Mehrjardi. "Assessing the Influence of Soil Quality on Rainfed Wheat Yield." Agriculture 10, no. 10 (October 12, 2020): 469. http://dx.doi.org/10.3390/agriculture10100469.
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Soil quality assessment based on crop yields and identification of key indicators of it can be used for better management of agricultural production. In the current research, the weighted additive soil quality index (SQIw), factor analysis (FA), and multiple linear regression (MLR) are used to assess the soil quality of rainfed winter wheat fields with two soil orders on 53.20 km2 of agricultural land in western Iran. A total of 18 soil quality indicators were determined for 100 soil samples (0–20 cm depth) from two soil orders (Inceptisols and Entisols). The soil properties measured were: pH, soil texture, organic carbon (OC), cation exchange capacity (CEC), electrical conductivity (EC), soil microbial respiration (SMR), carbonate calcium equivalent (CCE), soil porosity (SP), bulk density (BD), exchangeable sodium percentage (ESP), mean weight diameter (MWD), available potassium (AK), total nitrogen (TN), available phosphorus (AP), available Fe (AFe), available Zn (AZn), available Mn (AMn), and available Cu (ACu). Wheat grain yield for all of the 100 sampling sites was also gathered. The SQIw was calculated using two weighting methods (FA and MLR) and maps were created using a digital soil mapping framework. The soil indicators determined for the minimum data set (MDS) were AK, clay, CEC, AP, SMR, and sand. The correlation between the MLR weighting technique (SQIw-M) and the rainfed wheat yield (r = 0.62) was slightly larger than that the correlation of yield with the FA weighted technique (SQIw-F) (r = 0.58). Results showed that the means of both SQIw-M and SQIw-F and rainfed wheat yield for Inceptisols were higher than for Entisols, although these differences were not statistically significant. Both SQIw-M and SQIw-F showed that areas with Entisols had lower proportions of good soil quality grades (Grades I and II), and higher proportions of poor soil quality grades (Grades IV and V) compared to Inceptisols. Based on these results, soil type must be considered for soil quality assessment in future studies to maintain and enhance soil quality and sustainable production. The overall soil quality of the study region was of poor and moderate grades. To improve soil quality, it is therefore recommended that effective practices such as the implementation of scientifically integrated nutrient management involving the combined use of organic and inorganic fertilizers in rainfed wheat fields should be promoted.
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Sani,, A., A. M. Isah, U. K. Adamu, I. A. Adam, M. D. Garba, N. Abdullahi, M. A. Dandago, et al. "Effect of Hydrocarbon Contaminated Irrigation Water On Some Selected Soil Physical and Chemical Properties of Sudan Savannah Alfisols." Global Journal of Agricultural Research 10, no. 5 (May 15, 2022): 28–46. http://dx.doi.org/10.37745/gjar.2013/vol10n52846.
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Due to fresh water scarcity challenges around the world, high increase in the demand for agricultural irrigation water from different sources including hydrocarbon contaminated wastewater increases. However, these wastewaters can alter soil physical and chemical properties. The aim of this study is to evaluate the impact of the hydrocarbon contaminated irrigation water on some selected soil physical and chemical properties from three phases of Sharada industrial area, Kano, Nigeria. Soil and water samples were collected from three different phases of the industrial area and analyzed using standard laboratory procedures. The hydrocarbon irrigation water quality analyses indicated that the hydrocarbon concentration in all phases was low and below irrigation reuse standard. However, the major irrigation water quality parameters; chemical oxygen demand (COD), biochemical oxygen demand (BOD), nitrate nitrogen (NO3-N), hydrogen carbonate (HCO3), ammonium-nitrogen (NH4-N), potassium (K), chlorine (Cl) and orthophosphate phosphorus (PO4-P) in all phases were all high and above irrigation reuse standard in comparison to other parameters that were compliant to standard according to literature. Pertaining the impact of the hydrocarbon irrigation water on soil properties, results revealed that soil texture was sandy loam and loamy sand, pH was neutral while bulk density (BD), electrical conductivity (EC), organic carbon (OC), total nitrogen (TN), potassium (K), sodium (Na), calcium (Ca), magnesium (Mg), cation exchange capacity (CEC) and phosphorus (P) were increased and higher compared with control soils. However, they are low in terms of concentration when compared with literature rating standard except P. Moreover, Ca, Mg, CEC and P of the soils showed significant variation statistically (P<0.05) in comparison to the remaining soil properties that recorded no significant statistical difference (P>0.05) in all phases and control soils after irrigation with the hydrocarbon wastewater. Overall, the research indicated that, the hydrocarbon wastewater was not fit for irrigation and has impacted relatively on some physical and chemical soil properties. Hence, all industries in Sharada should be directed by authorities to avoid direct discharge of their effluents without thorough quality investigation. In addition, farmers should also be educated to periodically monitor and assess the irrigation water quality of the effluents prior to application as well as incorporation of organic and inorganic amendments in the irrigated soils to uplift the concentration of the soil properties with concomitant improvement in soil fertility and quality of the study area.
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Bouillon, S., A. Yambélé, R. G. M. Spencer, D. P. Gillikin, P. J. Hernes, J. Six, R. Merckx, and A. V. Borges. "Organic matter sources, fluxes and greenhouse gas exchange in the Oubangui River (Congo River basin)." Biogeosciences Discussions 9, no. 1 (January 3, 2012): 63–108. http://dx.doi.org/10.5194/bgd-9-63-2012.
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Abstract. The Oubangui is a major tributary of the Congo River, draining an area of ~ 500 000 km2 mainly consisting of wooded savannahs. Here, we report results of a one year long 2-weekly sampling campaign in Bangui (Central African Republic) since March 2010 for a suite of physico-chemical and biogeochemical characteristics, including total suspended matter (TSM), bulk concentration and stable isotope composition of particulate organic carbon (POC and δ13CPOC), particulate nitrogen (PN and δ15NPN), dissolved organic carbon (DOC and δ13CDOC), dissolved inorganic carbon (DIC and δ13CDIC), dissolved greenhouse gases (CO2, CH4 and N2O), and dissolved lignin composition. We estimated the total annual flux of TSM, POC, PN, DOC and DIC to be 2.33 Tg yr−1, 0.14 Tg C yr−1, 0.014 Tg N yr−1, 0.70 Tg C yr−1, and 0.49 Tg C yr−1, respectively. Most elements showed clear hysteresis over the hydrograph. δ13C signatures of both POC and DOC showed strong seasonal variations (−30.6 to −25.8 ‰, and −31.8 to −27.1 ‰, respectively) but with contrasting patterns. Our data indicate that the origins of POC and DOC may vary strongly over the hydrograph and are largely uncoupled, differing up to 6 ‰ in δ13C signatures. The low POC/PN ratios, high % POC and low and variable δ13CPOC signatures during low flow conditions suggest that during this period, the majority of the POC pool consists of in situ produced phytoplankton, consistent with concurrent pCO2 (partial pressure of CO2) values only slightly above and occasionally, below, atmospheric equilibrium. Dissolved lignin characteristics (carbon-normalised yields, cinnamyl:vanillyl phenol ratios, and vanillic acid to vanillin ratios) showed marked differences between high and low discharge conditions. We observed a~strong seasonality in pCO2, ranging between 470 ± 203 ppm for Q<1000 m3 s−1 (n=10) to a maximum of 3750 ppm during the first stage of the rising discharge. Water-atmosphere CO2 fluxes were estimated to average ~ 105 g C m−2 yr−1, i.e. more than an order of magnitude lower than current estimates for large tropical rivers globally. While our TSM and POC fluxes are similar to previous estimates for the Oubangui, DOC fluxes were ~ 30 % higher and bicarbonate fluxes were ~ 35 % lower than previous reports. DIC represented 58 % of the total annual C flux, and under the assumptions that carbonate weathering represents 25 % of the DIC flux and that CO2 from respiration drives chemical weathering, this flux is equivalent to ~ 50 % of terrestrial-derived riverine C transport. Although tropical rivers are often assumed to show much higher CO2 effluxes compared to temperate systems, we show that in situ production may be high enough to dominate the particulate organic carbon pool, and lower pCO2 values to near equilibrium values during low discharge conditions.
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Bouillon, S., A. Yambélé, R. G. M. Spencer, D. P. Gillikin, P. J. Hernes, J. Six, R. Merckx, and A. V. Borges. "Organic matter sources, fluxes and greenhouse gas exchange in the Oubangui River (Congo River basin)." Biogeosciences 9, no. 6 (June 8, 2012): 2045–62. http://dx.doi.org/10.5194/bg-9-2045-2012.
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Abstract. The Oubangui is a major tributary of the Congo River, draining an area of ~500 000 km2 mainly consisting of wooded savannahs. Here, we report results of a one year long, 2-weekly sampling campaign in Bangui (Central African Republic) since March 2010 for a suite of physico-chemical and biogeochemical characteristics, including total suspended matter (TSM), bulk concentration and stable isotope composition of particulate organic carbon (POC and δ13CPOC), particulate nitrogen (PN and δ15NPN), dissolved organic carbon (DOC and δ13CDOC), dissolved inorganic carbon (DIC and δ13CDIC), dissolved greenhouse gases (CO2, CH4 and N2O), and dissolved lignin composition. δ13C signatures of both POC and DOC showed strong seasonal variations (−30.6 to −25.8‰, and −31.8 to −27.1‰, respectively), but their different timing indicates that the origins of POC and DOC may vary strongly over the hydrograph and are largely uncoupled, differing up to 6‰ in δ13C signatures. Dissolved lignin characteristics (carbon-normalised yields, cinnamyl:vanillyl phenol ratios, and vanillic acid to vanillin ratios) showed marked differences between high and low discharge conditions, consistent with major seasonal variations in the sources of dissolved organic matter. We observed a strong seasonality in pCO2, ranging between 470 ± 203 ppm for Q < 1000 m3 s−1 (n=10) to a maximum of 3750 ppm during the first stage of the rising discharge. The low POC/PN ratios, high %POC and low and variable δ13CPOC signatures during low flow conditions suggest that the majority of the POC pool during this period consists of in situ produced phytoplankton, consistent with concurrent pCO2 (partial pressure of CO2) values only slightly above and, occasionally, below atmospheric equilibrium. Water-atmosphere CO2 fluxes estimated using two independent approaches averaged 105 and 204 g C m−2 yr−1, i.e. more than an order of magnitude lower than current estimates for large tropical rivers globally. Although tropical rivers are often assumed to show much higher CO2 effluxes compared to temperate systems, we show that in situ production may be high enough to dominate the particulate organic carbon pool, and lower pCO2 values to near equilibrium values during low discharge conditions. The total annual flux of TSM, POC, PN, DOC and DIC are 2.33 Tg yr−1, 0.14 Tg C yr−1, 0.014 Tg N yr−1, 0.70 Tg C yr−1, and 0.49 Tg C yr−1, respectively. While our TSM and POC fluxes are similar to previous estimates for the Oubangui, DOC fluxes were ~30% higher and bicarbonate fluxes were ~35% lower than previous reports. DIC represented 58% of the total annual C flux, and under the assumptions that carbonate weathering represents 25% of the DIC flux and that CO2 from respiration drives chemical weathering, this flux is equivalent to ~50% of terrestrial-derived riverine C transport.
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Islam, Md Shahidul, and Tadashi Ito. "257 Characterization of the Physico-chemical Properties of and Plant Response to Ecologically Sound Organic Substrates in Relation to Rockwool." HortScience 35, no. 3 (June 2000): 435D—435. http://dx.doi.org/10.21273/hortsci.35.3.435d.
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Characterization of physico-chemical properties of ecologically sound unprocessed coconut (Cocos nucifera L.) coir and carbonated rice husk in relation to rockwool were investigated to examine the crop performance along with productivity of tomatoes (Lycopersicon esculentum Mill.). In all substrates, the water-filled pore space and water-holding capacity were larger and air-filled pore space was smaller. Bulk densities, water-holding capacity, and water-filled, air-filled, and total pore spaces were lower in carbonated rice husk than coconut coir and rockwool. These values in coconut coir and carbonated rice husk were increased by use. Most of the physical properties, EC, pH, and inorganic elements, of these natural organic substrates were within appropriate levels as growing media. There were little differences in plant height, stem diameter, percent fruit set, harvest index, ascorbic acid, total soluble solid, fruit pH, and leaf chlorophyll ratio. But, number of nodes, internode length, leaf number and area, days to first anthesis, flower number, and fruit number and weight differed significantly among treatments. There was smaller fluctuation in absolute growth rate, relative growth rate, net assimilate rate, and leaf area ratio among the treatments. It appeared that carbonated rice husk and the coconut coir gave better crop performance than rockwool under moderate high temperatures (30 and 35 °C compared to 25 °C). Furthermore, crop productivity from the organic substrate coconut coir and carbonated rice husk gave more profit than that of rockwool. Thus, carbonated rice husk and coconut coir substrates can be used successfully as a bag culture media amendment for producing vegetables, especially in tropical and subtropical areas.
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Conterosito, Eleonora, Luca Palin, Diego Antonioli, Maria Riccardi, Enrico Boccaleri, Maurizio Aceto, Marco Milanesio, and Valentina Gianotti. "On the Rehydration of Organic Layered Double Hydroxides to form Low-Ordered Carbon/LDH Nanocomposites." Inorganics 6, no. 3 (August 14, 2018): 79. http://dx.doi.org/10.3390/inorganics6030079.
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Low-ordered carbon/layered double hydroxide (LDH) nanocomposites were prepared by rehydration of the oxides produced by calcination of an organic LDH. While the memory effect is a widely recognized effect on oxides produced by inorganic LDH, it is unprecedented from the calcination/rehydration of organic ones. Different temperatures (400, 600, and 1100 °C) were tested on the basis of thermogravimetric data. Water, instead of a carbonate solution, was used for the rehydration, with CO2 available from water itself and/or air to induce a slower process with an easier and better intercalation of the carbonaceous species. The samples were characterized by X-ray powder diffraction (XRPD), infrared in reflection mode (IR), and Raman spectroscopies and scanning electron microscopy (SEM). XRPD indicated the presence of carbonate LDH, and of residuals of unreacted oxides. IR confirmed that the prevailing anion is carbonate, coming from the water used for the rehydration and/or air. Raman data indicated the presence of low-ordered carbonaceous species moieties and SEM and XRPD the absence of separated bulky graphitic sheets, suggesting an intimate mixing of the low ordered carbonaceous phase with reconstructed LDH. Organic LDH gave better memory effect after calcination at 400 °C. Conversely, the carbonaceous species are observed after rehydration of the sample calcined at 600 °C with a reduced memory effect, demonstrating the interference of the carbonaceous phase with LDH reconstruction and the bonding with LDH layers to form a low-ordered carbon/LDH nanocomposite.
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Ishikawa, N. F., M. Yamane, H. Suga, N. O. Ogawa, Y. Yokoyama, and N. Ohkouchi. "Chlorophyll <i>a</i>-specific Δ<sup>14</sup>C, δ<sup>13</sup>C and δ<sup>15</sup>N values in stream periphyton: implications for aquatic food web studies." Biogeosciences 12, no. 22 (November 26, 2015): 6781–89. http://dx.doi.org/10.5194/bg-12-6781-2015.
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Abstract. Periphytic algae attached to a streambed substrate (periphyton) are an important primary producer in stream ecosystems. We determined the isotopic composition of chlorophyll a in periphyton collected from a stream flowing on limestone bedrock in the Seri River, central Japan. Stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) and natural radiocarbon abundances (Δ14C) were measured in chlorophyll a (δ13Cchl, δ15Nchl and Δ14Cchl) and bulk (δ13Cbulk, δ15Nbulk and Δ14Cbulk) for periphyton, a pure aquatic primary producer (Cladophora sp.) and a terrestrial primary producer (Quercus glauca). Periphyton δ13Cbulk and δ13Cchl values did not necessarily correspond to δ13Cbulk for an algal-grazing specialist (Epeorus latifolium). Periphyton Δ14Cchl values (−258 ‰ in April and −190 ‰ in October) were slightly lower than Δ14Cbulk values (−228 ‰ in April and −179 ‰ in October) but were close to the Δ14C value for dissolved inorganic carbon (DIC; −217 ± 31 ‰), which is a mixture of weathered carbonates (Δ14C = −1000 ‰), CO2 derived from aquatic and terrestrial organic matters (variable Δ14C) and dissolved atmospheric CO2 (Δ14C approximately +30 ‰ in 2013). Δ14Cchl values were also close to Δ14Cbulk for E. latifolium (−215 ‰ in April and −199 ‰ in October) and Cladophora sp. (−210 ‰), whereas the Δ14Cbulk value for Q. glauca (+27 ‰) was closer to Δ14C for atmospheric CO2. Although the bulk isotopic composition of periphyton is recognised as a surrogate for the photosynthetic algal community, natural periphyton is a mixture of aquatic and terrestrial organic materials. Our results indicate that the bulk periphyton matrix at the study site consists of 89 to 95 % algal carbon (derived from 14C-depleted DIC) and 5 to 11 % terrestrial organic carbon (derived from 14C-enriched atmospheric CO2).