Substantial heterogeneity of carbon and oxygen stable-isotope compositions of single layers or specimens of natural carbonate materials: New evidence from replicate sampling of continental carbonates affirms previous evidence from marine limestones

ABSTRACT The uncertainty of measurements of carbon and oxygen stable-isotope ratios of carbonate materials is commonly assumed to be the analytical uncertainty determined from replicate analyses of single samples, but this ignores the possibility that heterogeneity of the material studied is greater than the analytical uncertainty. To test this question, we took eight samples from each of 13 layers or specimens of various non-marine (“continental”) carbonates and found ranges of δ13C and δ18O of 0.3 to 5.1‰, all exceeding the range of the typical lab-reported analytical uncertainty, ± 0.1‰, placed around single samples. These results are similar to previous replicate sampling of marine limestone layers, which revealed ranges of 0.2 to 2.8‰. Both sets of results, and other published data, demonstrate that analytical uncertainty derived from replicate analysis of a single sample is not a valid estimate of the uncertainty of δ13C or δ18O values characterizing a layer or specimen, and they remind us that we should not place great credence in anomalies or events defined by single samples of layers or specimens, regardless of the replication of analysis of that single sample. Our results indicate that the required layer-level or specimen-level uncertainty can be derived only from replicate sampling at different locations in layers or specimens, and that the layer-level or specimen-level uncertainty is inevitably greater than typical lab-reported analytical uncertainty. Credibility of anomalies or events in time series would be increased by replicate sampling of a random or dispersed subset of layers to estimate the variability of all layers and/or by replicate sampling of layers at and around a potential but unconfirmed event. The significance of the variability discussed above is evident in use of δ18O data to estimate paleotemperatures, where a difference of 1‰ in δ18O implies a difference of 4°C in temperature. Use of a single sample resulting in mischaracterization of the δ18O of an ancient material by 1.5‰ relative to the true mean for that material (which our results suggest is quite possible) would lead to a corresponding misestimation of temperature of 6°C, a significant difference in paleoenvironmental studies.

Tannylated Calcium Carbonate Materials with Antacid, Anti-Inflammatory, and Antioxidant Effects

Calcium carbonate (CaCO3)-based materials have received notable attention for biomedical applications owing to their safety and beneficial characteristics, such as pH sensitivity, carbon dioxide (CO2) gas generation, and antacid properties. Herein, to additionally incorporate antioxidant and anti-inflammatory functions, we prepared tannylated CaCO3 (TA-CaCO3) materials using a simple reaction between tannic acid (TA), calcium (Ca2+), and carbonate (CO32−) ions. TA-CaCO3 synthesized at a molar ratio of 1:75 (TA:calcium chloride (CaCl2)/sodium carbonate (Na2CO3)) showed 3–6 μm particles, comprising small nanoparticles in a size range of 17–41 nm. The TA-CaCO3 materials could efficiently neutralize the acid solution and scavenge free radicals. In addition, these materials could significantly reduce the mRNA levels of pro-inflammatory factors and intracellular reactive oxygen species, and protect chondrocytes from toxic hydrogen peroxide conditions. Thus, in addition to their antacid property, the prepared TA-CaCO3 materials exert excellent antioxidant and anti-inflammatory effects through the introduction of TA molecules. Therefore, TA-CaCO3 materials can potentially be used to treat inflammatory cells or diseases.

Investigation of the Geochemical Composition and Paleo-Depositional Environment of Ubo and Ikpeshi Marble Deposit, Southwestern Nigeria: A Comparative Study

The marble deposits at Ubo and Ikpeshi areas of Edo state, Southwestern Nigeria, were studied in order to determine the major elements and the paleo-depositional environment of the original sediments using standard methods. Results obtained using test of difference between Ubo and Ikpeshi marbles showed that CaO (51.977±0.922 & 54.726±0.23), MgO (3.034±0.829 & 0.499±0.115), Na2O (1.7±0.73 & 0.024±0.008), MgCO3 (6.337±1.734 & 1.034±0.238), Cu (24.589±0.692 & 27.447±0.711), Ni (23.907±0.854 & 30.979±0.494), all for Ubo and Ikpeshi respectively; with Ni showing highest significance with P<0.01. The Ubo marble deposit occurs as a lensoid body within the younger metasedimentary sequence. The major element composition reveal a mean chemical composition of CaO (51.97 and 54.73 %), MgO (3.0 and 0.49 %), SiO2 (0.74 and 0.70%), K2O (0.08 and 0.04%), Na2O (1.70 and 0.02%), Al2O3 (0.75 and 0.25%), Fe2O3 (0.34 and 0.25%), and Loss on Ignition - L.O.I (43.34 and 49.31%) in Ubo and Ikpeshi marbles respectively, which is indicative that the marble samples were all calcitic. The low values of the total alkali content in the marble samples from the two locations indicate that the environment of deposition of the original carbonate materials that metamorphosed into marbles from both locations must have been a shallow, highly saline environment with probably little influx of salty brine water in the basin. Silica was used as an abscissa in these plots because it shows substantial variations among the marbles with most of the linear relationship between silica and the various oxides showing negative correlation, this probably reflects the admixture of the carbonates with chert. The trend of the plots of Na2O + K2O vs. SiO2 for the marbles from both locations show a variation in the salinity. Keywords: Ubo, Ikpeshi, Marble, Marine Environment, Metasedimentary

PO4 recovery using mixtures of biochar and carbonate materials

&lt;p&gt;The recovery of PO&lt;sub&gt;4&lt;/sub&gt; from wastewaters by using biochar proves not to be completely satisfactory. The surface of the biochar is typically negatively charged, which prevents the adsorption of PO&lt;sub&gt;4&lt;/sub&gt;. For this reason, mixtures of biochar and natural carbonate materials have been tested as a novel sorbent material for PO&lt;sub&gt;4 &lt;/sub&gt;recovery from both synthetic-and waste- water. The goal of the research is to obtain a PO&lt;sub&gt;4 &lt;/sub&gt;based complex starting from natural second-generation materials such as food industry byproducts, plants and other residues to prepare fertilisers compliant to the component material category CMC 6 defined in the Regulation &lt;strong&gt;(&lt;/strong&gt;EU) 2019/1009/EU It has to be noted that natural carbonate materials are not pure CaCO&lt;sub&gt;3&lt;/sub&gt;, but present small impurities that contribute to modify their properties. Therefore, the use of carbonate materials obtained from different sources can lead to different performances when it comes to PO&lt;sub&gt;4&lt;/sub&gt; removal from wastewaters.&lt;/p&gt;&lt;p&gt;In this work we present results of PO&lt;sub&gt;4&lt;/sub&gt; removal obtained from a mixture of biomass and different carbonate materials. The mixture has been treated through a specific thermal protocol to obtain two different calcium-oxide rich charcoals here named composites C1 and C2. Initially, each composite was added to synthetic waters with different PO&lt;sub&gt;4 &lt;/sub&gt;concentration, with a composite:water ratio of 1:1000. The initial concentrations of PO&lt;sub&gt;4 &lt;/sub&gt;were 10, 100 and 1000 mg/l. After treatment with the composite, regardless of whether C1 or C2 was used, the PO&lt;sub&gt;4 &lt;/sub&gt;concentration in the waters with initial concentration of 10 and 100 mg/L was nearly zero, with pH values at equilibrium around 11.9. The treatment of the water with initial PO&lt;sub&gt;4 &lt;/sub&gt;concentration of 1000 mg/l shows a reduction of 20% and 40% with C1 and C2, respectively, with final pH values around 7.8.&lt;/p&gt;&lt;p&gt;After addition of the composites to the water, the solutions present very high pH values except for the water with the highest concentration. Although this is an optimal situation for the removal of PO&lt;sub&gt;4&lt;/sub&gt;, it leads to two problems. First, the filtered water is not suitable for direct disposition in sewers, since the pH is higher than the limit established by the wastewater legislation (9.5). Second, a pH value larger than 9 determines the precipitation of PO&lt;sub&gt;4 &lt;/sub&gt;regardless of the presence of the composite, which suggests that the PO&lt;sub&gt;4&lt;/sub&gt; is not adsorbed by the composites, thus not leading to the desired complex&lt;/p&gt;&lt;p&gt;In order to quantify the exact amount of PO&lt;sub&gt;4&lt;/sub&gt; adsorbed by the composite, the experiments have been repeated under controlled pH, keeping it around a value of 7 by the use of a mild acid. In this condition, after 1h treatment, 50% of phosphate was removed and bound to the composite&lt;/p&gt;&lt;p&gt;The work intends to present the results at laboratory scale and next steps at higher TRL.&lt;/p&gt;

Fabrication of patterned calcium carbonate materials through template-assisted microbially induced calcium carbonate precipitation

A simple and green approach based on template-assisted microbially induced calcium carbonate precipitation for the fabrication of patterned calcium carbonate materials was demonstrated.

Widespread carbon-bearing materials on near-Earth asteroid (101955) Bennu

Asteroid (101955) Bennu is a dark asteroid on an Earth-crossing orbit that is thought to have assembled from the fragments of an ancient collision. We use spatially resolved visible and near-infrared spectra of Bennu to investigate its surface properties and composition. In addition to a hydrated phyllosilicate band, we detect a ubiquitous 3.4-micrometer absorption feature, which we attribute to a mix of organic and carbonate materials. The shape and depth of this absorption feature vary across Bennu’s surface, spanning the range seen among similar main-belt asteroids. The distribution of the absorption feature does not correlate with temperature, reflectance, spectral slope, or hydrated minerals, although some of those characteristics correlate with each other. The deepest 3.4-micrometer absorptions occur on individual boulders. The variations may be due to differences in abundance, recent exposure, or space weathering.

Physical and chemical characteristics of 1300 lakes and ponds across the Canadian Arctic

Lakes and ponds are a major feature of the Arctic landscape and are recognized as effective ‘sentinels of change’. Here we present water chemistry characteristics of lakes and ponds (n=1300 with 26 variables) across the Canadian Arctic collated from published studies. We also extracted geological and ecoregion data in an attempt to determine the key drivers. In general, most lakes were shallow (85.4%, <10 m), nutrient (phosphorus) poor (oligotrophic = 45.6% and ultra-oligotrophic = 24.8%), located at low elevation (66.5%, <200 m asl), close to coastlines (72.5%, 0-50 km), and underlain by sedimentary geology (66.5%). The first two components from Principal Component Analysis explained 49.3% of the variation in the dataset; the first component was dominated by conductivity/carbonate materials, and the second component suggested allochthonous inputs of phosphorus. In general, bedrock geology is the primary driver of water chemistry; as such, there were major differences between lakes underlain by igneous and sedimentary rocks. Those on sedimentary bedrock tend to have higher pH, nutrients and higher inorganic ion concentrations.