Articles de revues : « Calcule time-Scales »

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Sahir, M. J. S. « Объединение классических и динамических неравенств, возникающих при анализе временных масштабов ». Вестник КРАУНЦ. Физико-математические науки, n^o 4 (29 décembre 2020) : 26–36. http://dx.doi.org/10.26117/2079-6641-2020-33-4-26-36.

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In this paper, we present an extension of dynamic Renyi’s inequality on time scales by using the time scale Riemann–Liouville type fractional integral. Furthermore, we find generalizations of the well–known Lyapunov’s inequality and Radon’s inequality on time scales by using the time scale Riemann–Liouville type fractional integrals. Our investigations unify and extend some continuous inequalities and their corresponding discrete analogues. В этой статье мы представляем расширение динамического неравенства Реньи на шкалы времени с помощью дробного интеграла типа Римана-Лиувилля. Кроме того, мы находим обобщения хорошо известного неравенства Ляпунова и неравенства Радона на шкалах времени с помощью дробных интегралов типа Римана-Лиувилля на шкале. Наши исследования объединяют и расширяют некоторые непрерывные неравенства и соответствующие им дискретные аналоги.

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Le-Anh, Duy, Ashit Rao, Amy Stetten, Subhash Ayirala, Mohammed Alotaibi, Michel Duits, Han Gardeniers, Ali AlYousef et Frieder Mugele. « Oil Displacement in Calcite-Coated Microfluidic Chips via Waterflooding at Elevated Temperatures and Long Times ». Micromachines 13, n^o 8 (14 août 2022) : 1316. http://dx.doi.org/10.3390/mi13081316.

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In microfluidic studies of improved oil recovery, mostly pore networks with uniform depth and surface chemistry are used. To better mimic the multiple porosity length scales and surface heterogeneity of carbonate reservoirs, we coated a 2.5D glass microchannel with calcite particles. After aging with formation water and crude oil (CRO), high-salinity Water (HSW) was flooded at varying temperatures and durations. Time-resolved microscopy revealed the CRO displacements. Precise quantification of residual oil presented some challenges due to calcite-induced optical heterogeneity and brine–oil coexistence at (sub)micron length scales. Both issues were addressed using pixel-wise intensity calibration. During waterflooding, most of the ultimately produced oil gets liberated within the first pore volume (similar to glass micromodels). Increasing temperature from 22 °C to 60 °C and 90 °C produced some more oil. Waterflooding initiated directly at 90 °C produced significantly more oil than at 22 °C. Continuing HSW exposure at 90 °C for 8 days does not release additional oil; although, a spectacular growth of aqueous droplets is observed. The effect of calcite particles on CRO retention is weak on flat surfaces, where the coverage is ~20%. The calcite-rich pore edges retain significantly more oil suggesting that, in our micromodel wall roughness is a stronger determinant for oil retention than surface chemistry.

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Van Rampelbergh, M., S. Verheyden, M. Allan, Y. Quinif, E. Keppens et P. Claeys. « Seasonal variations recorded in cave monitoring results and a 10 year monthly resolved speleothem δ18O and δ13C record from the Han-sur-Lesse cave, Belgium ». Climate of the Past Discussions 10, n^o 2 (22 avril 2014) : 1821–56. http://dx.doi.org/10.5194/cpd-10-1821-2014.

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Abstract. Speleothems provide paleoclimate information on multi-millennial to decadal scales in the Holocene. However seasonal or even monthly resolved records remain scarce. They require fast growing stalagmites and a good understanding of the proxy transfer function on very short time scales. The Proserpine stalagmite from the Han-sur-Less cave (Belgium) displays seasonal layers of 0.5 to 2 mm thickness that reconstruct paleoclimates at a monthly scale. Through a regular cave monitoring, we acquired a good understanding of how δ18O and δ13C signals in modern calcite reflect climate variations on sub-seasonal scale. Cave parameters vary seasonally in response to the activity of the vegetation cover and outside air temperature. From December to June, the cave remains in "winter-mode". Outside temperatures are cold inducing low cave air and water temperatures. Bio-productivity in the soil is limited leading to low pCO2, higher δ13C composition of the CO2 in the cave air and high discharge due to the inactivity of the plant coverage. From June to December, the cave switches to "summer-mode" and the measured factors display an opposite behavior. The δ18O and δ13C signals of fresh calcite precipitated on glass slabs vary seasonally. Lowest δ18O values occur during the summer-mode when the δ13C values are high. The δ18O composition of the calcite is in equilibrium with the drip water δ18O and display seasonal variations due to changes in the cave air and water temperature. In contrast to the δ18O signal, δ13C values of the calcite precipitated on the glass slabs do not reflect equilibrium conditions. Highest δ13C values occur during summer, when discharge rates are low increasing the evaporation effect on the thin water film covering the stalagmite. This same antithetical behavior of the δ18O vs. the δ13C signals is seen in the monthly resolved speleothem record that covers the period between 1976 and 1985 AD. Dark layers are formed during summer, while light layers are formed during winter when calcite deposition occurs fast. The darker the color of a layer, the more compact its calcite structure, the more negative its δ18O signal and the more positive its δ13C signal.

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Putranto, W. A., Y. Umardhani, Sulistyo, Yurianto et A. P. Bayuseno. « Analysis of calcium carbonate polymorphs deposited in water piping system and the effect of tartaric acid additive ». MATEC Web of Conferences 159 (2018) : 01054. http://dx.doi.org/10.1051/matecconf/201815901054.

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Calcium carbonate (CaCO3) formed in a water piping system was investigated in the presence of chemical additives tartaric acid (0.00 and 10.00 ppm) and various temperatures ((27 and 50ºC). The flow rate inside pipe (35 ml/min) were selected. Solutions of CaCl2 and Na2CO3 were prepared in water with equimolar to Ca2+ concentration of 3000 ppm. The induction time of scale nucleation varied from 24 min to 44 min. An increasing temperature of the solution resulted in more CaCO3 scale, mass, while the higher tartaric acid made the reduced mass of scales by 90%. SEM/EDS analysis verified CaCO3 with a plate like morphology. Also the XRPD Rietveld method provided the confirmation of a major phase of calcite and vaterite minerals followed by the minor of aragonite in the absence of tartaric acid and at room temperature. However, the presence of 10 ppm tartaric acid yielded the increasing result of calcite, while aragonite precipitation was hampered under the influence of tartaric acid. The presence of tartaric acid at increasing temperature of 50ºC could delay formation of calcite, whereas aragonite could be formed significantly. Thus the study showed the capacity of the tartaric acid in influencing CaCO3 crystallization.

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Khan, Hares, Alo Laas, Rafael Marcé, Margot Sepp et Biel Obrador. « Eutrophication and Geochemistry Drive Pelagic Calcite Precipitation in Lakes ». Water 13, n^o 5 (25 février 2021) : 597. http://dx.doi.org/10.3390/w13050597.

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Pelagic calcification shapes the carbon budget of lakes and the sensitivity of dissolved inorganic carbon (DIC) responses to lake metabolism. This process, being tightly linked to primary production, needs to be understood within the context of summer eutrophication which is increasing due to human stressors and global change. Most lake carbon budget models do not account for calcification because the conditions necessary for its occurrence are not well constrained. This study aims at identifying ratios between calcification and primary production and the drivers that control these ratios in freshwater. Using in situ incubations in several European freshwater lakes, we identify a strong relationship between calcite saturation and the ratio between calcification and net ecosystem production (NEP) (p-value < 0.001, R2 = 0.95). NEP-induced calcification is a short-term process that is potentiated by the increase in calcite saturation occurring at longer time scales, usually reaching the highest levels in summer. The resulting summer calcification event has effects on the DIC equilibria, causing deviations from the metabolic 1:1 stoichiometry between DIC and dissolved oxygen (DO). The strong dependency of the ratio between NEP and calcification on calcite saturation can be used to develop a suitable parameterization to account for calcification in lake carbon budgets.

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Blain, Gabriel C., et Monica C. Meschiatti. « Inadequacy of the gamma distribution to calculate the Standardized Precipitation Index ». Revista Brasileira de Engenharia Agrícola e Ambiental 19, n^o 12 (décembre 2015) : 1129–35. http://dx.doi.org/10.1590/1807-1929/agriambi.v19n12p1129-1135.

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ABSTRACT The Standardized Precipitation Index was developed as a probability-based index able to monitor rainfall deficit in a standardized or normalized way. Thus, the performance of this drought index is affected by the use of a distribution that does not provide an appropriate fit for the rainfall data. The goal of this study was to evaluate the adjustment of the gamma distribution for the rainfall amounts summed over several time scales (Pelotas, Rio Grande do Sul, Brazil), to assess the goodness-of-fit of alternative distributions to these rainfall series and to evaluate the normality assumption of the Standardized Precipitation Index series calculated from several distributions. Based on the Lilliefors test and on a normality test, it is verified that the gamma distribution is not suitable for calculating this Index in several timescales. The generalized normal distribution presented the best performance among all analysed distributions. It was also concluded that the drought early warning systems and the academic studies should re-evaluate the use of the gamma distribution in the Standardized Precipitation Index calculation algorithm. A computational code that allows calculating this drought index based on the generalized normal distribution has also been provided.

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Caley, T., et D. M. Roche. « δ18O water isotope in the iLOVECLIM model (version 1.0) – Part 3 : A palaeo-perspective based on present-day data–model comparison for oxygen stable isotopes in carbonates ». Geoscientific Model Development 6, n^o 5 (12 septembre 2013) : 1505–16. http://dx.doi.org/10.5194/gmd-6-1505-2013.

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Abstract. Oxygen stable isotopes (δ18O) are among the most useful tools in palaeoclimatology/palaeoceanography. Simulation of oxygen stable isotopes allows testing how the past variability of these isotopes in water can be interpreted. By modelling the proxy directly in the model, the results can also be directly compared with the data. Water isotopes have been implemented in the global three-dimensional model of intermediate complexity iLOVECLIM, allowing fully coupled atmosphere–ocean simulations. In this study, we present the validation of the model results for present-day climate against the global database for oxygen stable isotopes in carbonates. The limitation of the model together with the processes operating in the natural environment reveal the complexity of use the continental calcite-δ18O signal of speleothems for a global quantitative data–model comparison exercise. On the contrary, the reconstructed surface ocean calcite-δ18O signal in iLOVECLIM does show a very good agreement with the late Holocene database (foraminifers) at the global and regional scales. Our results indicate that temperature and the isotopic composition of the seawater are the main control on the fossil-δ18O signal recorded in foraminifer shells when all species are grouped together. Depth habitat, seasonality and other ecological effects play a more significant role when individual species are considered. We argue that a data–model comparison for surface ocean calcite δ18O in past climates, such as the Last Glacial Maximum (≈ 21 000 yr), could constitute an interesting tool for mapping the potential shifts of the frontal systems and circulation changes throughout time. Similarly, the potential changes in intermediate oceanic circulation systems in the past could be documented by a data (benthic foraminifers)-model comparison exercise whereas future investigations are necessary in order to quantitatively compare the results with data for the deep ocean.

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Caley, T., et D. M. Roche. « δ18O water isotope in the iLOVECLIM model (version 1.0) – Part 3 : A paleoperspective based on present-day data-model comparison for oxygen stable isotopes in carbonates ». Geoscientific Model Development Discussions 6, n^o 1 (4 mars 2013) : 1527–58. http://dx.doi.org/10.5194/gmdd-6-1527-2013.

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Abstract. Oxygen stable isotopes (18O) are among the most usual tools in paleoclimatology/paleoceanography. Simulation of oxygen stable isotopes allows testing how the past variability of these isotopes in water can be interpreted. By modelling the proxy directly in the model, the results can also be directly compared with the data. Water isotopes have been implemented in the global three-dimensional model of intermediate complexity iLOVECLIM allowing fully coupled atmosphere-ocean simulations. In this study, we present the validation of the model results for present day climate against global database for oxygen stable isotopes in carbonates. The limitation of the model together with the processes operating in the natural environment reveal the complexity of use the continental calcite 18O signal of speleothems for a data-model comparison exercise. On the contrary, the reconstructed surface ocean calcite δ18O signal in iLOVECLIM does show a very good agreement with late Holocene database (foraminifers) at the global and regional scales. Our results indicate that temperature and the isotopic composition of the seawater are the main control on the fossil δ18O signal recorded in foraminifer shells and that depth habitat and seasonality play a role but have secondary importance. We argue that a data-model comparison for surface ocean calcite δ18O in past climate, such as the last glacial maximum (&approx;21 000 yr), could constitute an interesting tool for mapping the potential shifts of the frontal systems and circulation changes throughout time. Similarly, the potential changes in intermediate oceanic circulation systems in the past could be documented by a data (benthic foraminifers)-model comparison exercise whereas future investigations are necessary in order to quantitatively compare the results with data for the deep ocean.

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Claes, Steven, Fadi H. Nader et Souhail Youssef. « Coupled experimental/numerical workflow for assessing quantitative diagenesis and dynamic porosity/permeability evolution in calcite-cemented sandstone reservoir rocks ». Oil & ; Gas Science and Technology – Revue d’IFP Energies nouvelles 73 (2018) : 36. http://dx.doi.org/10.2516/ogst/2018027.

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Some of the world best hydrocarbon reservoirs (carbonates and siliciclastics) are also believed to be valuable for subsurface storage of CO2 and other fluids. Yet, these reservoirs are heterogeneous in terms of their mineralogy and flow properties, at varying spatial-temporal scales. Therefore, predicting the porosity and permeability (flow properties) evolution of carbonates and sandstones remains a tedious task. Diagenesis refers to the alteration of sedimentary rocks through geologic time, mainly due to rock-fluid interactions. It affects primarily the flow properties (porosity and permeability) of already heterogeneous reservoir rocks. In this project a new approach is proposed to calculate/quantify the influence of diagenetic phases (e.g. dissolution, cement plugging) on flow properties of typical sandstone reservoir rocks (Early Jurassic Luxembourg Formation). A series of laboratory experiments are performed in which diagenetic phases (e.g. pore blocking calcite cement in sandstone) are selectively leached from pre-studied samples, with the quantification of the petrophysical characteristics with and without cement to especially infer permeability evolution. Poorly and heavily calcite-cemented sandstone samples, as well as some intermediate cemented samples were used. The results show a distinctive dissolution pattern for different cementation grades and varying Representative Elementary Volumes (REVs). These conclusions have important consequences for upscaling diagenesis effects on reservoirs, and the interpretation of geochemical modelling results of diagenetic processes. The same approach can be applied on other type of cements and host-rocks, and could be improved by integrating other petrophysical analyses (e.g. petroacoustic, NMR).

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de Wet, Carol B., Andrew P. de Wet, Linda Godfrey, Elizabeth Driscoll, Samuel Patzkowsky, Chi Xu, Sophia Gigliotti et Melina Feitl. « Pliocene short-term climate changes preserved in continental shallow lacustrine-palustrine carbonates : Western Opache Formation, Atacama Desert, Chile ». GSA Bulletin 132, n^o 9-10 (23 décembre 2019) : 1795–816. http://dx.doi.org/10.1130/b35227.1.

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Abstract Multiple climate proxies indicate episodic changes in moisture levels within an ∼1 Ma duration (early–mid Pliocene) interval. Limestones within the Opache Formation, Calama Basin, Atacama Desert region, Chile, contain evidence for wetter and drier periods on short time scales. Proxies include carbonate lithological changes, paleontology (stromatolites, oncolites, gastropods, ostracods and diatoms), O and C stable isotopes, geochemistry, and mineralogical changes (aragonite, calcite, Mg-calcite, dolomite and gypsum) throughout a 30 m stratigraphic section. Stromatolite fossil cyanobacteria dark and light laminations and mesohaline to hypersaline diatom species suggest Pliocene annual seasonality. Short-term changes between wetter and drier conditions indicate that at least this part of the Atacama region was experiencing relatively rapid early–mid Pliocene climate instability. The predominance of limestone in the Opache Formation, in contrast to the 1500 m of Oligocene-Miocene siliciclastic conglomerates and sandstones, interpreted as arid climate alluvium, that underlie it, indicates a shift from arid or hyperarid climate to a semi-arid climate. Semi-arid conditions promoted limestone deposition in a shallow lacustrine-palustrine environment. In this setting, events such as storms with associated surface water flow, erosion, siliciclastic sand, gravel, and intraclast deposition, coupled with significant biological activity, represent sedimentation during more humid periods in a shallow lacustrine depositional environment. In contrast, limestone characterized by mudcracks, Navicula diatoms, and vadose syndepositional cementation, reflect periods of enhanced evaporation, water shallowing, and episodic desiccation, characteristic of a palustrine depositional system. These facies shifts, in conjunction with geochemical and isotopic proxy evidence, yield a sedimentary record of wetter and drier climate shifts.

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Branson, Oscar, Elisa A. Bonnin, Daniel E. Perea, Howard J. Spero, Zihua Zhu, Maria Winters, Bärbel Hönisch, Ann D. Russell, Jennifer S. Fehrenbacher et Alexander C. Gagnon. « Nanometer-Scale Chemistry of a Calcite Biomineralization Template : Implications for Skeletal Composition and Nucleation ». Proceedings of the National Academy of Sciences 113, n^o 46 (28 octobre 2016) : 12934–39. http://dx.doi.org/10.1073/pnas.1522864113.

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Plankton, corals, and other organisms produce calcium carbonate skeletons that are integral to their survival, form a key component of the global carbon cycle, and record an archive of past oceanographic conditions in their geochemistry. A key aspect of the formation of these biominerals is the interaction between organic templating structures and mineral precipitation processes. Laboratory-based studies have shown that these atomic-scale processes can profoundly influence the architecture and composition of minerals, but their importance in calcifying organisms is poorly understood because it is difficult to measure the chemistry of in vivo biomineral interfaces at spatially relevant scales. Understanding the role of templates in biomineral nucleation, and their importance in skeletal geochemistry requires an integrated, multiscale approach, which can place atom-scale observations of organic-mineral interfaces within a broader structural and geochemical context. Here we map the chemistry of an embedded organic template structure within a carbonate skeleton of the foraminifera Orbulina universa using both atom probe tomography (APT), a 3D chemical imaging technique with Ångström-level spatial resolution, and time-of-flight secondary ionization mass spectrometry (ToF-SIMS), a 2D chemical imaging technique with submicron resolution. We quantitatively link these observations, revealing that the organic template in O. universa is uniquely enriched in both Na and Mg, and contributes to intraskeletal chemical heterogeneity. Our APT analyses reveal the cation composition of the organic surface, offering evidence to suggest that cations other than Ca2+, previously considered passive spectator ions in biomineral templating, may be important in defining the energetics of carbonate nucleation on organic templates.

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Chen, Xiuhua, Wenlong Song, Yangjun Shi, Weidong Liu, Yizhu Lu, Zhiguo Pang et Xiao Chen. « Application of Cosmic-Ray Neutron Sensor Method to Calculate Field Water Use Efficiency ». Water 14, n^o 9 (9 mai 2022) : 1518. http://dx.doi.org/10.3390/w14091518.

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Field water use efficiency is an important parameter for evaluating the quality of field irrigation in irrigated areas, which directly affects the country’s food security and water resource allocation. However, most current studies use point-scale soil moisture (SM) or remote sensing water balance models to calculate the field water use coefficient, which cannot avoid errors caused by the spatial heterogeneity of SM and insufficient spatial resolution of remote sensing data. Therefore, in this study, the cosmic-ray neutron sensor (CRNS), Time-Domain Reflectometers (TDR) and Automatic Weather Stations (AWS) were used to monitor the meteorological and hydrological data such as SM, atmospheric pressure, and precipitation in the experimental area of Jinghuiqu Irrigation District for three consecutive years. The scale of the CRNS SM lies between the point and the remote sensing. Based on the CRNS SM, the calculation method for canal head and tail water was used to calculate the field water use efficiency to evaluate the level of agricultural irrigation water use in the experimental irrigation area. The results showed that CRNS could accurately detect the change in SM, and four irrigation events were monitored during the winter wheat growth period from October 2018 to June 2019; the calculation result of field water use efficiency in the experimental area was 0.77. According to the field water use efficiency of the same irrigation area from October 2013 to October 2015 in other studies, the field water use efficiency during the growing period of winter wheat in this area increased from 0.503 to 0.770 in 2013–2019, indicating a significant improvement in the field water use level. In general, this study not only solves the problem of low calculation accuracy of field water use efficiency caused by the mismatch of SM monitoring scales but also explores the application potential of CRNS in agricultural irrigation management and water resource allocation.

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Weidel, Brian C., Takayuki Ushikubo, Stephen R. Carpenter, Noriko T. Kita, Jonathan J. Cole, James F. Kitchell, Michael L. Pace et John W. Valley. « Diary of a bluegill (Lepomis macrochirus) : daily δ13C and δ18O records in otoliths by ion microprobe ». Canadian Journal of Fisheries and Aquatic Sciences 64, n^o 12 (1 décembre 2007) : 1641–45. http://dx.doi.org/10.1139/f07-157.

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Otoliths provide information about an individual fish’s environment at ecologically relevant time scales. We used ion microprobe analysis to produce high-resolution δ13C and δ18O time series from two age-4 bluegill (Lepomis macrochirus) otoliths, which provided insight into fish behavior and otolith fractionation processes. Scanning electron microscope images revealed δ13C and δ18O pit diameters of 10 and 15 µm, respectively, corresponding to 1–5 and 2–9 daily increments during rapid otolith growth and 6–9 and 12–25 increments near annual otolith growth checks. Spot-to-spot reproducibility (1 SD) of the calcite standards was <0.2‰ for δ18O and <0.4‰ for δ13C and was small enough to resolve a change in a fish’s ambient temperature of approximately 1 °C. A whole-lake 13C addition experiment elevated the δ13C of the lake’s dissolved inorganic carbon for 56 days during the summer of 2005. Mixing model results indicated that the proportion of dietary carbon in otoliths (M) was similar for both fish (BLG-3, M = 0.45; BLG-12, M = 0.35), but the relation between M and proxies of metabolic rate differed between fish. Otolith stable isotope analysis by ion microprobe can reveal the environmental history of an individual fish and contribute to our understanding of processes that influence isotope ratio fractionation in otoliths.

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Heslop, D., et A. Paul. « Can oceanic paleothermometers reconstruct the Atlantic Multidecadal Oscillation ? » Climate of the Past Discussions 6, n^o 5 (14 octobre 2010) : 2177–97. http://dx.doi.org/10.5194/cpd-6-2177-2010.

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Abstract. Instrumental records of North Atlantic sea surface temperature reveal a large-scale low frequency mode of variability that has become known as the Atlantic Multidecadal Oscillation (AMO). Proxy and modelling studies have demonstrated the important consequences of the AMO on other components of the climate system both within and outside the Atlantic region. Over longer time scales the past behavior of the AMO is predominantly constrained by terrestrial proxies and only a limited number of records are available from the marine realm itself. Here we use an Earth System-Climate Model of intermediate complexity to simulate AMO-type behavior in the Atlantic with a specific focus placed on the ability of ocean paleothermometers to capture the associated surface and subsurface temperature variability. Given their lower prediction errors and annual resolution, coral-based proxies of sea surface temperature appear to be capable of reconstructing the temperature variations associated with the past AMO with an adequate signal-to-noise ratio. Contrastingly, the relatively high prediction error and low temporal resolution of sediment-based proxies, such as the composition of foraminiferal calcite, limits their ability to produce interpretable records of past temperature anomalies corresponding to AMO activity.

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Rushton, Jeremy C., Doris Wagner, Jonathan M. Pearce, Christopher A. Rochelle et Gemma Purser. « Red-bed bleaching in a CO2 storage analogue : Insights from Entrada Sandstone fracture-hosted mineralization ». Journal of Sedimentary Research 90, n^o 1 (22 janvier 2020) : 48–66. http://dx.doi.org/10.2110/jsr.2020.4.

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ABSTRACT Improving our ability to predict the interactions between CO2 and reservoir rocks at geological time scales is of key importance if carbon capture and storage (CCS) is to have a role in climate-change mitigation, particularly in the light of likely regulatory requirements. Understanding and identifying the relevant geological processes over long time scales can be obtained only at natural-analogue sites. At one such site, in the Salt Wash Graben area of Utah, USA, widespread bleaching affects the Middle Jurassic red-bed “wet dune” Entrada Sandstone. Previous work has proposed a genetic link between the bleaching and spatially concomitant recent and modern CO2-rich fluids. The results presented here challenge some of the previous models and come from a detailed petrographic examination of mineralized fractures in the Entrada Sandstone that are centered in vertical extensions to the bleaching. These fractures typically contain complex mineralization assemblages. Pyrite was a paragenetically early phase, identifiable from common pseudomorphs of mixed iron oxides and oxyhydroxides that rarely contain relict pyrite. The pyrite contains up to 3 wt% arsenic. The volume of fracture-adjacent bleached sandstone is sufficient to have been the source of iron for the pyrite originally present in the fracture. The pyrite pseudomorphs occur at the center of fracture- and pore-filling cements that comprise intergrowths of hematite–goethite–jarosite–gypsum, an assemblage that suggests that their formation resulted from the oxidative alteration of pyrite, a genetic link supported by the arsenic present in the iron-bearing minerals. The presence of jarosite and proximal removal of earlier, sandstone-hosted carbonates are consistent with, and indicative of, the low-pH conditions associated with pyrite oxidation reactions. Calcite- and gypsum-cemented fractures crosscut, and contain fragments of, the pyrite-pseudomorphic and -oxidation assemblages, proving that they postdate pyrite formation and its subsequent oxidation, and that pyrite oxidation was not a result of modern weathering reactions. In outcrop, some calcite- and gypsum-cemented fractures link with travertine deposits associated with the modern and recent CO2-rich fluids. The mineral assemblages observed here, and the paragenetic sequence that we have inferred, suggest that the fracture-associated bleaching patterns result from the fracture-fed movement of sulfur-bearing reducing fluids, with hydrogen sulfide the most likely bleaching agent. We conclude that bleaching adjacent to fractures is not genetically related to modern CO2-bearing fluids despite the spatial relationship. The bleaching was already present when the modern fluids utilized the same fracture-based fluid pathways. We suggest that the more widespread regional bleaching formed contemporaneously with the fracture bleaching and followed similar mechanisms. This study highlights the complexity of interpreting analogue sites and the importance of using field and petrographic observations to unravel textures and events that are juxtaposed spatially but not temporally.

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Zeebe, R. E. « LOSCAR : Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir Model ». Geoscientific Model Development Discussions 4, n^o 2 (29 juin 2011) : 1435–76. http://dx.doi.org/10.5194/gmdd-4-1435-2011.

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Abstract. The LOSCAR model is designed to efficiently compute the partitioning of carbon between ocean, atmosphere, and sediments on time scales ranging from centuries to millions of years. While a variety of computationally inexpensive carbon cycle models are already available, many are missing a critical sediment component, which is indispensable for long-term integrations. One of LOSCAR's strengths is the coupling of ocean-atmosphere routines to a computationally efficient sediment module. This allows, for instance, adequate computation of CaCO3 dissolution, calcite compensation, and long-term carbon cycle fluxes, including weathering of carbonate and silicate rocks. The ocean component includes various biogeochemical tracers such as total carbon, alkalinity, phosphate, oxygen, and stable carbon isotopes. We have previously published applications of the model tackling future projections of ocean chemistry and weathering, pCO2 sensitivity to carbon cycle perturbations throughout the Cenozoic, and carbon/calcium cycling during the Paleocene-Eocene Thermal Maximum. The focus of the present contribution is the detailed description of the model including numerical architecture, processes and parameterizations, tuning, and examples of input and output. Typical CPU integration times of LOSCAR are of order seconds for several thousand model years on current standard desktop machines. The LOSCAR source code in C can be obtained from the author by sending a request to loscar.model@gmail.com.

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Akanni, Olatokunbo O., Hisham A. Nasr-El-Din et Deepak Gusain. « A Computational Navier-Stokes Fluid-Dynamics-Simulation Study of Wormhole Propagation in Carbonate-Matrix Acidizing and Analysis of Factors Influencing the Dissolution Process ». SPE Journal 22, n^o 06 (4 octobre 2017) : 2049–66. http://dx.doi.org/10.2118/187962-pa.

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Summary This study demonstrates the application of an alternative numerical-simulation approach to effectively describe the flow field in a two-scale carbonate-matrix-acidizing model. The modified model accurately captures the dissolution regimes that occur during carbonate-matrix acidizing. Sensitivity tests were performed on the model to compare the output with experimental observations and previous two-scale models in the literature. A nonlinear reaction-kinetics model for alternative acidizing fluids is also introduced. In this work, the fluid-field flow is described by the Navier-Stokes momentum approach instead of Darcy's law or the Darcy-Brinkman approach used in previous two-scale models. The present model is implemented by means of a commercial computational-fluid-dynamics (CFD) package to solve the momentum, mass-conservation, and species-transport equations in Darcy scale. The software is combined with functions and routines written in the C programming language to solve the porosity-evolution equation, update the pore-scale parameters at every timestep in the simulation, and couple the Darcy and pore scales. The output from the model simulations is consistent with experimental observations, and the results from the sensitivity tests performed are in agreement with previously developed two-scale models with the Darcy approach. The simulations at very-high injection rates with this model require less computational time than models developed with the Darcy approach. The results from this model show that the optimal injection rate obtained in laboratory coreflood experiments cannot be directly translated for field applications because of the effect of flow geometry and medium dimensions on the wormholing process. The influence of the reaction order on the optimal injection rate and pore volumes (PVs) of acid required to reach breakthrough is also demonstrated by simulations run to test the applicability of the model for acids with nonlinear kinetics in reaction with calcite. The new model is computationally less expensive than previous models with the Darcy-Brinkman approach, and simulations at very-high injection rates with this model require less computational time than Darcy-based models. Furthermore, the possibility of extending the two-scale model for acid/calcite reactions with more-complex chemistry is shown by means of the introduction of nonlinear kinetics in the reaction equation.

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Heslop, D., et A. Paul. « Can oceanic paleothermometers reconstruct the Atlantic Multidecadal Oscillation ? » Climate of the Past 7, n^o 1 (2 mars 2011) : 151–59. http://dx.doi.org/10.5194/cp-7-151-2011.

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Abstract. Instrumental records of the North Atlantic sea surface temperature reveal a large-scale low frequency mode of variability that has become known as the Atlantic Multidecadal Oscillation (AMO). Proxy and modelling studies have demonstrated the important consequences of the AMO on other components of the climate system both within and outside the Atlantic region. Over longer time scales, the past behavior of the AMO is predominantly constrained by terrestrial proxies and only a limited number of records are available from the marine realm itself. Here we use an Earth System-Climate Model of intermediate complexity to simulate AMO-type behavior in the Atlantic with a specific focus placed on the ability of ocean paleothermometers to capture the associated surface and subsurface temperature variability. Given their lower prediction errors and annual resolution, coral-based proxies of sea surface temperature appear to be capable of reconstructing the temperature variations associated with the past AMO with an adequate signal-to-noise ratio. In contrast, the relatively high prediction error and low temporal resolution of sediment-based proxies, such as the composition of foraminiferal calcite, limits their ability to produce interpretable records of past temperature anomalies corresponding to AMO activity. Whilst the presented results will inevitably be model-dependent to some degree, the statistical framework is model-independent and can be applied to a wide variety of scenarios.

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Zeebe, R. E. « LOSCAR : Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir Model v2.0.4 ». Geoscientific Model Development 5, n^o 1 (25 janvier 2012) : 149–66. http://dx.doi.org/10.5194/gmd-5-149-2012.

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Abstract. The LOSCAR model is designed to efficiently compute the partitioning of carbon between ocean, atmosphere, and sediments on time scales ranging from centuries to millions of years. While a variety of computationally inexpensive carbon cycle models are already available, many are missing a critical sediment component, which is indispensable for long-term integrations. One of LOSCAR's strengths is the coupling of ocean-atmosphere routines to a computationally efficient sediment module. This allows, for instance, adequate computation of CaCO3 dissolution, calcite compensation, and long-term carbon cycle fluxes, including weathering of carbonate and silicate rocks. The ocean component includes various biogeochemical tracers such as total carbon, alkalinity, phosphate, oxygen, and stable carbon isotopes. LOSCAR's configuration of ocean geometry is flexible and allows for easy switching between modern and paleo-versions. We have previously published applications of the model tackling future projections of ocean chemistry and weathering, pCO2 sensitivity to carbon cycle perturbations throughout the Cenozoic, and carbon/calcium cycling during the Paleocene-Eocene Thermal Maximum. The focus of the present contribution is the detailed description of the model including numerical architecture, processes and parameterizations, tuning, and examples of input and output. Typical CPU integration times of LOSCAR are of order seconds for several thousand model years on current standard desktop machines. The LOSCAR source code in C can be obtained from the author by sending a request to loscar.model@gmail.com.

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Qian, Weihong, et Yafen Zhu. « Little Ice Age Climate near Beijing, China, Inferred from Historical and Stalagmite Records ». Quaternary Research 57, n^o 1 (janvier 2002) : 109–19. http://dx.doi.org/10.1006/qres.2001.2283.

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AbstractFour data sets yield information about Holocene climatic change in China at different scales of space and time: (a) 120-yr ground temperature and precipitation measurements covering eastern China; (b) two NOAA 10-yr 850 hPa wind records that highlight features of data set a; (c) an 1100-year record of annual calcite accumulation on a stalagmite near Beijing, and (d) Lamb-type average wetness and temperature data from Chinese historical records back to A.D. 1470 and 1450, respectively. Dry–wet fluctuations and cold–warm oscillations are inferred using the long-term stalagmite thickness series. Quasi-70, 140, 450, and 750-yr oscillations have been detected using a wavelet transform technique. A phase relationship between temperature and precipitation oscillations has been identified based on modern observations and historical records. In northern China, relatively lower temperatures correlate with periods when precipitation shifted from above to below normal. Three colder periods during the Little Ice Age (LIA) in China are inferred, centered in the late 14th century (750-yr oscillation), the early 17th century (450-yr), and the 19th century (140-yr). The latest cool period (1950s–1970s) is found at the 70-yr oscillation. Interdecadal drought–flood and cold–warm differences are explained using modern circulation patterns. LIA climate in China was likely controlled by East Asian monsoon circulation anomalies that were affected by variations in continent–ocean thermal contrast.

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Shaffer, G., S. Malskǽr Olsen et J. O. P. Pedersen. « Presentation, calibration and validation of the low-order, DCESS Earth System Model ». Geoscientific Model Development Discussions 1, n^o 1 (23 juin 2008) : 39–124. http://dx.doi.org/10.5194/gmdd-1-39-2008.

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Abstract. A new, low-order Earth system model is described, calibrated and tested against Earth system data. The model features modules for the atmosphere, ocean, ocean sediment, land biosphere and lithosphere and has been designed to simulate global change on time scales of years to millions of years. The atmosphere module considers radiation balance, meridional transport of heat and water vapor between low-mid latitude and high latitude zones, heat and gas exchange with the ocean and sea ice and snow cover. Gases considered are carbon dioxide and methane for all three carbon isotopes, nitrous oxide and oxygen. The ocean module has 100 m vertical resolution, carbonate chemistry and prescribed circulation and mixing. Ocean biogeochemical tracers are phosphate, dissolved oxygen, dissolved inorganic carbon for all three carbon isotopes and alkalinity. Biogenic production of particulate organic matter in the ocean surface layer depends on phosphate availability but with lower efficiency in the high latitude zone, as determined by model fit to ocean data. The calcite to organic carbon rain ratio depends on surface layer temperature. The semi-analytical, ocean sediment module considers calcium carbonate dissolution and oxic and anoxic organic matter remineralisation. The sediment is composed of calcite, non-calcite mineral and reactive organic matter. Sediment porosity profiles are related to sediment composition and a bioturbated layer of 0.1 m thickness is assumed. A sediment segment is ascribed to each ocean layer and segment area stems from observed ocean depth distributions. Sediment burial is calculated from sedimentation velocities at the base of the bioturbated layer. Bioturbation rates and oxic and anoxic remineralisation rates depend on organic carbon rain rates and dissolved oxygen concentrations. The land biosphere module considers leaves, wood, litter and soil. Net primary production depends on atmospheric carbon dioxide concentration and remineralization rates in the litter and soil are related to mean atmospheric temperatures. Methane production is a small fraction of the soil remineralization. The lithosphere module considers outgassing, weathering of carbonate and silicate rocks and weathering of rocks containing old organic carbon and phosphorus. Weathering rates are related to mean atmospheric temperatures. A pre-industrial, steady state calibration to Earth system data is carried out. Ocean observations of temperature, carbon 14, phosphate, dissolved oxygen, dissolved inorganic carbon and alkalinity constrain air-sea exchange and ocean circulation, mixing and biogeochemical parameters. Observed calcite and organic carbon distributions and inventories in the ocean sediment help constrain sediment module parameters. Carbon isotopic data and carbonate vs silicate weathering fractions are used to estimate initial lithosphere outgassing and rock weathering rates. Model performance is tested by simulating atmospheric greenhouse gas increases, global warming and model tracer evolution for the period 1765 to 2000, as forced by prescribed anthropogenic greenhouse gas inputs and other anthropogenic and natural forcing. Long term, transient model behavior is studied with a set of 100 000 year simulations, forced by a slow, 5000 GtC input of CO2 to the atmosphere, and with a 1.5 million year simulation, forced by a doubling of lithosphere CO2 outgassing.

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Shaffer, G., S. Malskær Olsen et J. O. Pepke Pedersen. « Presentation, calibration and validation of the low-order, DCESS Earth System Model (Version 1) ». Geoscientific Model Development 1, n^o 1 (6 novembre 2008) : 17–51. http://dx.doi.org/10.5194/gmd-1-17-2008.

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Abstract. A new, low-order Earth System Model is described, calibrated and tested against Earth system data. The model features modules for the atmosphere, ocean, ocean sediment, land biosphere and lithosphere and has been designed to simulate global change on time scales of years to millions of years. The atmosphere module considers radiation balance, meridional transport of heat and water vapor between low-mid latitude and high latitude zones, heat and gas exchange with the ocean and sea ice and snow cover. Gases considered are carbon dioxide and methane for all three carbon isotopes, nitrous oxide and oxygen. The ocean module has 100 m vertical resolution, carbonate chemistry and prescribed circulation and mixing. Ocean biogeochemical tracers are phosphate, dissolved oxygen, dissolved inorganic carbon for all three carbon isotopes and alkalinity. Biogenic production of particulate organic matter in the ocean surface layer depends on phosphate availability but with lower efficiency in the high latitude zone, as determined by model fit to ocean data. The calcite to organic carbon rain ratio depends on surface layer temperature. The semi-analytical, ocean sediment module considers calcium carbonate dissolution and oxic and anoxic organic matter remineralisation. The sediment is composed of calcite, non-calcite mineral and reactive organic matter. Sediment porosity profiles are related to sediment composition and a bioturbated layer of 0.1 m thickness is assumed. A sediment segment is ascribed to each ocean layer and segment area stems from observed ocean depth distributions. Sediment burial is calculated from sedimentation velocities at the base of the bioturbated layer. Bioturbation rates and oxic and anoxic remineralisation rates depend on organic carbon rain rates and dissolved oxygen concentrations. The land biosphere module considers leaves, wood, litter and soil. Net primary production depends on atmospheric carbon dioxide concentration and remineralization rates in the litter and soil are related to mean atmospheric temperatures. Methane production is a small fraction of the soil remineralization. The lithosphere module considers outgassing, weathering of carbonate and silicate rocks and weathering of rocks containing old organic carbon and phosphorus. Weathering rates are related to mean atmospheric temperatures. A pre-industrial, steady state calibration to Earth system data is carried out. Ocean observations of temperature, carbon 14, phosphate, dissolved oxygen, dissolved inorganic carbon and alkalinity constrain air-sea exchange and ocean circulation, mixing and biogeochemical parameters. Observed calcite and organic carbon distributions and inventories in the ocean sediment help constrain sediment module parameters. Carbon isotopic data and carbonate vs. silicate weathering fractions are used to estimate initial lithosphere outgassing and rock weathering rates. Model performance is tested by simulating atmospheric greenhouse gas increases, global warming and model tracer evolution for the period 1765 to 2000, as forced by prescribed anthropogenic greenhouse gas inputs and other anthropogenic and natural forcing. Long term, transient model behavior is studied with a set of 100 000 year simulations, forced by a slow, 5000 Gt C input of CO2 to the atmosphere, and with a 1.5 million year simulation, forced by a doubling of lithosphere CO2 outgassing.

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Lutfullin, Azat A., Eduard M. Abusalimov, Aleksey E. Folomeev, Arslan R. Khatmullin, Andrey R. Sharifullin et Marat R. Sitdikov. « Complex matrix treatment technologies selection and adaptation for the injection wells of the Republic of Tatarstan oilfields ». Georesursy 24, n^o 4 (20 décembre 2022) : 91–101. http://dx.doi.org/10.18599/grs.2022.4.8.

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Nowadays, oil fields on the territory of the Republic of Tatarstan are developed with application of systems for reservoir pressure maintenance, involving injection of large volumes of water into the formation. Efficiency of waterflooding depends on the quality of the injected agent, and, despite the use of various technologies of preparation and treatment of injected water, with the lapse of time critical matrix porosity and permeability inevitably decreases. In this work the main sources of injection wells critical matrix clogging are considered: mechanical impurities, oil products and scales formation, and the results of the component composition analysis of deposits from cluster pumping stations are given. Using the Oddo-Thomson methodology, it is revealed that injected water is prone to calcite and barite deposition at bottomhole conditions. Physicochemical and core-flooding study of several reagents for removing colmatants: acid compositions, hydrocarbon solvents and complexing agents were carried out and their optimal formulations were determined. The matrix treatment technology, including the sequential injection of compositions based on hydrochloric and mud acids, was substantiated. An algorithm for calculating the optimal reagent volume has been developed on the basis of research data on the mineralogical composition of mechanical impurities and ionic composition of injected water. Four types of matrix treatment technologies were determined for the conditions of injection wells at the Romashkinskoye oil field Devonian formation, taking into account the composition of colmatant, and acid treatment designs were developed.

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Anderson, Lesleigh, Mark B. Abbott et Bruce P. Finney. « Holocene Climate Inferred from Oxygen Isotope Ratios in Lake Sediments, Central Brooks Range, Alaska ». Quaternary Research 55, n^o 3 (mai 2001) : 313–21. http://dx.doi.org/10.1006/qres.2001.2219.

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AbstractAnalyses of sediment cores from two lakes in the central Brooks Range provide temperature and moisture balance information for the past ∼8500 cal yr at century-scale resolution. Two methods of oxygen isotope analysis are used to reconstruct past changes in the effective moisture (precipitation minus evaporation) and temperature. Effective moisture is inferred from oxygen isotope ratios in sediment cellulose from Meli Lake (area ∼0.13 km2, depth 19.4 m). The lake has a low watershed-to-lake-area ratio (7) and significant evaporation relative to input. Summer temperature shifts are based on oxygen isotope analyses of endogenic calcite from Tangled Up Lake (area ∼0.25 km2, depth 3.5 m). This basin has a larger watershed-to-lake-area ratio (91) and less evaporation relative to input. Sediment oxygen isotope analyses from the two sites indicate generally more arid conditions than present prior to ∼6000 cal yr B.P. Subsequently, the region became increasingly wet. Temperature variability is recorded minimally at centennial scale resolution with values that are generally cool for the past ∼6700 cal yr. The timing and direction of climate variability indicated by the oxygen isotope time series from Meli and Tangled Up lakes are consistent with previously established late Holocene glacier advances at ∼5000 cal yr B.P. in the central Brooks Range, and high lake-levels at Birch Lake since ∼5500 cal yr B.P. This unique use of oxygen isotopes reveals both moisture balance and temperature histories at previously undetected high-resolution temporal scales for northern Alaska during the middle to late Holocene.

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He, Zhenbo, Li Zhang, Lihong Wang, Qiang Zhang et Lingyu Luan. « Anti-Scale Performance and Mechanism of Valonia Tannin Extract for Calcium Carbonate in Circulating Cooling Water System ». Sustainability 15, n^o 11 (30 mai 2023) : 8811. http://dx.doi.org/10.3390/su15118811.

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Natural-polymer-based antiscalants for various calcium scales have recently received significant attention due to their prominent structural features, such as hydroxyl, amino, and organic acids, as well as their environmental friendliness and widespread availability. In this study, a novel green antiscalant, namely modified valonia tannin extract (MVTE), was synthesized using valonia tannin extract (VTE), itaconic acid (IA), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS). The structure of MVTE was characterized by Fourier transform infrared spectroscopy (FT-IR). The crystal morphology, structure, and surface elementary composition of CaCO3 were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), respectively. Results indicate that MVTE with the best anti-scale performance is prepared when the valonia dosage is 2.5 g, the initiator dosage is 6 wt.%, the reaction temperature is 75 °C, and the reaction time is 3.5 h. Moreover, MVTE shows significantly improved resistance to temperature and alkalinity compared to VE. Results from SEM, XRD, and XPS demonstrate that MVTE can interfere with the regular growth of CaCO3 crystals through chelation, dispersion, and lattice distortion. This effect results in the generation of vaterite, which inhibits the deposition of CaCO3. Meanwhile, the molecular dynamics (MD) simulation was employed to further explore the anti-scale mechanisms at an atomistic level. The results illustrate that interaction energies originate from ionic and hydrogen bonds between MVTE and calcite, which ultimately improve the anti-scale performance of MVTE. In conclusion, MVTE can be an excellent antiscalant in circulating cooling water systems.

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Rivers, John M. « Warm acidified seawater : a dolomite solution ». Journal of Sedimentary Research 93, n^o 3 (21 mars 2023) : 187–201. http://dx.doi.org/10.2110/jsr.2022.087.

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ABSTRACT The “dolomite problem” is the product of two distinct observations. First, there are massive amounts of ancient marine limestone (CaCO3) deposits that have been replaced by the mineral dolomite (MgCa(CO3)2). However, recent (Holocene and Pleistocene) marine deposits contain relatively minuscule amounts of dolomite, although the occurrence of small quantities of dolomite is observed in many modern settings, from deep marine to supratidal. Second, low-temperature synthesis of dolomite in laboratory settings has been elusive, particularly in comparison to the ease with which common marine calcium carbonate minerals (aragonite and calcite) can be synthesized. Since low-temperature solid-state diffusion can be discounted as a method for Mg incorporation into calcium carbonate (as it operates on time scales too long to matter), the replacement of CaCO3 by dolomite is one of dissolution followed by precipitation. Therefore, an often overlooked but required factor in the replacement of limestone by dolomite is that of undersaturation regarding the original calcium carbonate mineral during replacement. Such conditions could conceivably be caused by rapid dolomite growth relative to aragonite and calcite dissolution–precipitation reactions, but laboratory studies, modern systems analyses, and observations of ancient deposits all point to this possibility being uncommon because dolomite growth is kinetically inhibited at low temperature. Pressure solution by force of dolomite crystallization is a second possible driver for CaCO3 undersaturation, but requires a confining stress most likely attained through burial. However, based on petrographic observations, significant amounts of ancient dolomite replaced limestone before burial (synsedimentary dolomite), and many such platforms have not suffered any significant burial. Because these possibilities of undersaturation caused by dolomite precipitation and crystal growth can be largely discounted, the undersaturation required for “dolomitization” to proceed is most likely to be externally forced. In modern natural systems, undersaturation and selective CaCO3 dissolution in marine porewaters is very common, even in warm-water environments, being forced by the breakdown of organic matter. Such dissolution is frequently attended, to varying degrees, by precipitation of a kinetically-less-favored but thermodynamically more stable phase of CaCO3. Laboratory studies as well as observations of modern systems show that when undersaturation is reached with respect to all common marine CaCO3 phases, dolomite assumes the role of this kinetically-less-favored precipitate. This degree of undersaturation is uncommon in modern shallow marine pore systems in warm-water settings, but it was more common during times of elevated atmospheric CO2, and ocean acidification. Furthermore, because oxidation of organic matter drives dolomite formation, near-surface organic-rich deposits such as the remains of microbial mat communities, were more predisposed to dolomite replacement in the acidified oceans of the ancient past relative to contemporaneous deposits that contained less organic matter. These observations lend to a more harmonious explanation for the abundance and occurrence of dolomite through time.

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Tan, Jingqiang, Guolai Li, Ruining Hu, Lei Li, Qiao Lyu et Jeffrey Dick. « Experimental Investigation of the Impacts of Fracturing Fluid on the Evolution of Fluid Composition and Shale Characteristics : A Case Study of the Niutitang Shale in Hunan Province, South China ». Energies 13, n^o 13 (29 juin 2020) : 3320. http://dx.doi.org/10.3390/en13133320.

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Hydraulic fracturing is a widely used technique for oil and gas extraction from ultra-low porosity and permeability shale reservoirs. During the hydraulic fracturing process, large amounts of water along with specific chemical additives are injected into the shale reservoirs, causing a series of reactions the influence the fluid composition and shale characteristics. This paper is focused on the investigation of the geochemical reactions between shale and fracturing fluid by conducting comparative experiments on different samples at different time scales. By tracking the temporal changes of fluid composition and shale characteristics, we identify the key geochemical reactions during the experiments. The preliminary results show that the dissolution of the relatively unstable minerals in shale, including feldspar, pyrite and carbonate minerals, occurred quickly. During the process of mineral dissolution, a large number of metal elements, such as U, Pb, Ba, Sr, etc., are released, which makes the fluid highly polluted. The fluid–rock reactions also generate many pores, which are mainly caused by dissolution of feldspar and calcite, and potentially can enhance the extraction of shale gas. However, precipitation of secondary minerals like Fe-(oxy) hydroxides and CaSO4 were also observed in our experiments, which on the one hand can restrict the migration of metal elements by adsorption or co-precipitation and on the other hand can occlude the pores, therefore influencing the recovery of hydrocarbon. The different results between the experiments of different samples revealed that mineralogical texture and composition strongly affect the fluid-rock reactions. Therefore, the identification of the shale mineralogical characteristics is essential to formulate fracturing fluid with the lowest chemical reactivity to avoid the contamination released by flowback waters.

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Quinn, Patrick, Robert M. Bowers, Xiaoyu Zhang, Thomas M. Wahlund, Michael A. Fanelli, Daniela Olszova et Betsy A. Read. « cDNA Microarrays as a Tool for Identification of Biomineralization Proteins in the Coccolithophorid Emiliania huxleyi (Haptophyta) ». Applied and Environmental Microbiology 72, n^o 8 (août 2006) : 5512–26. http://dx.doi.org/10.1128/aem.00343-06.

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ABSTRACT Marine unicellular coccolithophore algae produce species-specific calcite scales otherwise known as coccoliths. While the coccoliths and their elaborate architecture have attracted the attention of investigators from various scientific disciplines, our knowledge of the underpinnings of the process of biomineralization in this alga is still in its infancy. The processes of calcification and coccolithogenesis are highly regulated and likely to be complex, requiring coordinated expression of many genes and pathways. In this study, we have employed cDNA microarrays to investigate changes in gene expression associated with biomineralization in the most abundant coccolithophorid, Emiliania huxleyi. Expression profiling of cultures grown under calcifying and noncalcifying conditions has been carried out using cDNA microarrays corresponding to approximately 2,300 expressed sequence tags. A total of 127 significantly up- or down-regulated transcripts were identified using a P value of 0.01 and a change of >2.0-fold. Real-time reverse transcriptase PCR was used to test the overall validity of the microarray data, as well as the relevance of many of the proteins predicted to be associated with biomineralization, including a novel gamma-class carbonic anhydrase (A. R. Soto, H. Zheng, D. Shoemaker, J. Rodriguez, B. A. Read, and T. M. Wahlund, Appl. Environ. Microbiol. 72:5500-5511, 2006). Differentially regulated genes include those related to cellular metabolism, ion channels, transport proteins, vesicular trafficking, and cell signaling. The putative function of the vast majority of candidate transcripts could not be defined. Nonetheless, the data described herein represent profiles of the transcription changes associated with biomineralization-related pathways in E. huxleyi and have identified novel and potentially useful targets for more detailed analysis.

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Zhu, Huixing, Tianfu Xu, Hailong Tian, Guanhong Feng, Zhijie Yang et Bing Zhou. « Understanding of Long-Term CO2-Brine-Rock Geochemical Reactions Using Numerical Modeling and Natural Analogue Study ». Geofluids 2019 (15 juillet 2019) : 1–16. http://dx.doi.org/10.1155/2019/1426061.

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To further understand the interactions of CO2-brine-rock at geological time scales, in this study, a 1D reactive transport model of CO2 intrusion into sandstone of the Longtan Formation (P2l) in the Huangqiao area, China, was constructed based on site-specific data. The simulation time is consistent with the retention time of CO2 in the Longtan sandstone Formation and is set to 20 Ma. The reactive transport model is calibrated and revised using the measured data for sandstone samples from Well X3 (i.e., the natural analogue). By comparing the simulation results with measured data for the natural analogue, the long-term geochemical reactions are investigated. The simulation results indicate that the brine-rock interactions induced by CO2 can be roughly divided into two stages. First, susceptible minerals (e.g., chlorite, ankerite, calcite, and feldspar minerals) dissolve rapidly under acidic conditions formed by the dissolution of CO2. The precipitation of siderite is facilitated by the dissolution of ankerite and chlorite. Smectite-Ca and dawsonite precipitate due to the dissolution of anorthite and albite, respectively. Dawsonite begins to convert into smectite-Na when albite is completely dissolved. As the reactions continue, intermediate products (i.e., illite, smectite-Na, and smectite-Ca) generated in the first stage become the reactants and subsequently react with CO2 and brine. These three clay minerals are not stable under acidic conditions and transform into kaolinite and paragenetic quartz in the later stage of reaction. Comparing the simulation results of the Base Case with the measured data for the natural analogue and inspired by previous studies, the scour of kaolinite is supposed to have occurred in this region and is considered in the revised model by introducing a coefficient of the scour of kaolinite (i.e., Case 2). The simulation results of Case 2 fit well with the measured data on mineral assemblage, and the trend of the sandstone porosity growth caused by the CO2-brine-rock reaction is captured by our simulation results. The combination of numerical simulation and natural analogue study indicates that the joint effects of long-term CO2-brine-rock reactions and scour of kaolinite increase the pore space of the host rock and result in an increase in quartz content in the sandstone.

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He, Haibo, Xinfang Ma, Fan Lei, Xinqiu Liu, Ming Jiang, Yue Li et Jianye Mou. « An Experimental Investigation of Interaction between CO2 Solution and Rock under Reservoir Conditions in the Jimsar Shale Oil Formation ». Processes 12, n^o 4 (27 mars 2024) : 673. http://dx.doi.org/10.3390/pr12040673.

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Chemical sequestration is one important manner of CCUS. The injection of CO2 into an oil reservoir can not only sequestrate CO2 but also raise the oil recovery factor. The performance of chemical sequestration of CO2 depends on the interaction between CO2 solution and reservoir rock. In this paper, we have conducted three different scales of experiments, e.g., microscopic scale, core scale, and time scale, to fully investigate the interaction and resultant variation to mineral content, microscopic structure, porosity, and permeability under reservoir conditions (i.e., reservoir temperature of 90 °C) in Jimusar shale oil formation. The microscopic-scale experiment applied SEM and hyperspectral scanning to obtain microscopic pore throat structure and element distribution before and after soaking the rock in CO2 solution. The core-scale experiment employed XRD to evaluate mineral content variation caused by CO2 solution. Core flooding experiments were conducted to evaluate porosity and permeability variation caused by the dissolution of CO2 solution into the core samples. The third type of experiment was employed to investigate the effect of time sequence on the dissolution, in which the time ranged from 1 day to 14 days continuously. The experimental results indicate that, under Jimsar reservoir conditions, CO2 solution exhibits a relatively robust dissolution capability, causing significant alterations to the properties of the core samples. Specifically, the CO2 solution effectively dissolves carbonate upon contact. Calcite is the primary target for dissolution, followed by dolomite. In the presence of sufficient CO2, complete dissolution of all carbonates is achievable. On a microscopic scale, dissolution primarily occurs in the calcium-rich areas, leaving other regions unaffected. The typical pore size resulting from CO2 solution-induced dissolution ranges from several to dozens of micrometers. This dissolution process significantly enhances both porosity and permeability. For Jimsar shale core samples, porosity experienced an increase of over 20%, and permeability nearly doubled. Under Jimsar reservoir conditions at 90 °C, CO2 solution can consume all carbonates present in core samples within 8 days. The increase in porosity and permeability is rapid during the initial days and stabilizes around the 6th day. These research findings establish a theoretical foundation for CO2 chemical sequestration.

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Frieder, C. A., S. H. Nam, T. R. Martz et L. A. Levin. « High temporal and spatial variability of dissolved oxygen and pH in a nearshore California kelp forest ». Biogeosciences 9, n^o 10 (12 octobre 2012) : 3917–30. http://dx.doi.org/10.5194/bg-9-3917-2012.

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Abstract. Predicting consequences of ocean deoxygenation and ocean acidification for nearshore marine ecosystems requires baseline dissolved oxygen (DO) and carbonate chemistry data that are both high-frequency and high-quality. Such data allow accurate assessment of environmental variability and present-day organism exposure regimes. In this study, scales of DO and pH variability were characterized over one year in a nearshore kelp forest ecosystem in the Southern California Bight. DO and pH were strongly, positively correlated, revealing that organisms on this upwelling shelf are not only exposed to low pH but also to low DO. The dominant scale of temporal DO and pH variability occurred on semidiurnal, diurnal and event (days–weeks) time scales. Daily ranges in DO and pH at 7 m water depth (13 mab) could be as large as 220 μmol kg−1 and 0.36 units, respectively. Sources of pH and DO variation include photosynthesis within the kelp forest ecosystem, which can elevate DO and pH by up to 60 μmol kg−1 and 0.1 units over one week following the intrusion of high-density, nutrient-rich water. Accordingly, highly productive macrophyte-based ecosystems could serve as deoxygenation and acidification refugia by acting to elevate DO and pH relative to surrounding waters. DO and pH exhibited greater spatial variation over a 10 m increase in water depth (from 7 to 17 m) than along a 5 km stretch of shelf in a cross-shore or alongshore direction. Over a three-month time period, mean DO and pH at 17 m water depth were 168 μmol kg−1 and 7.87, respectively. These values represent a 35% decrease in mean DO and 37% increase in [H+] relative to near-surface waters. High-frequency variation was also reduced at depth. The mean daily range in DO and pH was 39% and 37% less, respectively, at 17 m water depth relative to 7 m. As a consequence, the exposure history of an organism is largely a function of its depth of occurrence within the kelp forest. With knowledge of local alkalinity conditions and high-frequency temperature, salinity, and pH data, we estimated pCO2 and calcium carbonate saturation states with respect to calcite and aragonite (Ωcalc and Ωarag) for the La Jolla kelp forest at 7 m and 17 m water depth. pCO2 ranged from 246 to 1016 μatm, Ωcalc was always supersaturated, and Ωarag was undersaturated at the beginning of March for five days when pH was less than 7.75 and DO was less than 115 μmol kg−1. These findings raise the possibility that the benthic communities along eastern boundary current systems are currently acclimatized and adapted to natural, variable, and low DO and pH. Still, future exposure of coastal California populations to even lower DO and pH may increase as upwelling intensifies and hypoxic boundaries shoal, compressing habitats and challenging the physiological capacity of intolerant species.

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Zhao, Enlai, Enyuan Wang et Haopeng Chen. « Study on Dynamic Parameters and Energy Dissipation Characteristics of Coal Samples under Dynamic Load and Temperature ». Processes 11, n^o 12 (29 novembre 2023) : 3326. http://dx.doi.org/10.3390/pr11123326.

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Coal and rock dynamic disasters such as rock burst and outburst seriously threaten the sustainable development of the coal mining industry, which are intimately correlated with the nonlinear dynamic response process of the deep coal and rock mass. This study conducts coal dynamic experiments under vibration load from room temperature to 60 °C by using the split Hopkinson bar (SHPB) with a temperature real-time control system and analyzes the variation in stress and strain and the energy dissipation characteristics of coal during the dynamic load process. The expression equation of dissipated energy of coal at different scales is established, and the judgment conditions of the macroscopic mechanical behavior of coal are analyzed theoretically. The stress curves show a multi-stress peak phenomenon when the coal samples are subjected to different temperatures and dynamic loads, and the coal’s dynamic stress and temperature show a polynomial fitting relationship at different stages. When the coal sample is subjected to temperature and dynamic load, the macroscopic changes in incident energy, reflected energy, and dissipated energy are consistent; that is, various energies gradually increase to a fixed value and tend to stabilize with the time of stress wave action. The transmission energy exhibits a rising trend in correlation with the duration of the dynamic load action, but the value is less than 0.1 J. The growth gradients of the different energies, in descending order, are: the growth gradient of incident energy, reflection energy, dissipation energy, and transmission energy. The energy inflection point appears at 60 °C. Based on the linear elastic fracture mechanics and damage mechanics theories, the expression for coal energy dissipation from the nanoscale to the microscale is established, and the relationship between energy dissipation and macroscopic mechanical behavior response of the coal samples is analyzed. The main physical components of the coal sample are calcite and kaolinite. Within the temperature range of 18–60 °C, the macroscopic failure form of the coal is horizontal tensile failure. The study results are introduced into dynamic disaster prevention and control and the surrounding rock system stability evaluation in deep mines.

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Chen, Jian, Jie Xu, Susu Wang, Zhenyu Sun, Zhong Li, Wanglu Jia et Ping’an Peng. « Dissolution of Different Reservoir Rocks by Organic Acids in Laboratory Simulations : Implications for the Effect of Alteration on Deep Reservoirs ». Geofluids 2021 (22 mars 2021) : 1–16. http://dx.doi.org/10.1155/2021/6689490.

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Organic acids are important agents in the alteration of deep reservoirs. It is difficult, however, to assess the impact of organic acid alteration on deep reservoirs because different dissolution processes may occur during diagenesis. This study simulated the dissolution of three different types of reservoir rocks by acetic acid in a closed system and compared the mineral and elemental composition, surface morphology, pore structure, and water chemistry variations of the initial and altered samples. The study demonstrated that both micrite and sucrosic dolostone are strongly dissolved, losing about 20%–30% of their initial rock sample weights. Observation under SEM showed that the limestone dissolved homogenously, whereas the dolostone showed honeycomb-like dissolution. Both carbonate samples showed the development of large voids, including holes and cavities of micrometer scale, but nanopores of various sizes were blocked. In contrast, lithic arkose was heterogeneously altered, losing a weight proportion of about 13% by dissolution of calcite cement. These micrometer-scale microfissures were developed, but those nanometer-scale pores just varied in a narrow range of sizes. The volume increase in all three reservoir types is mainly attributed to the dissolution of carbonate minerals. In deep reservoirs, in situ generated organic acids can enlarge existing cavities in carbonates and develop microfissures in sandstones. The microfissure porosity in sandstone is limited but can increase through other geological processes such as overpressure. More importantly, these acids can maintain the acidity of pore waters, inhibit the precipitation of dissolved minerals, and help to preserve reservoir porosity. Although temperature plays an insignificant role in laboratory simulations, it influences both the generation and destruction processes of organic acids in deep reservoirs on geologic time scales and, thus, warrants further attention. The results provide a basis for recognizing the typical patterns of organic acid dissolution on different reservoir rocks and further suggest the potential role of organic acids in the formation and preservation of secondary porosity in deeply buried reservoirs.

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Battaglia, G., M. Steinacher et F. Joos. « A probabilistic assessment of calcium carbonate export and dissolution in the modern ocean ». Biogeosciences Discussions 12, n^o 24 (21 décembre 2015) : 20223–82. http://dx.doi.org/10.5194/bgd-12-20223-2015.

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Abstract. The marine cycle of calcium carbonate (CaCO3) is an important element of the carbon cycle and co-governs the distribution of carbon and alkalinity within the ocean. However, CaCO3 fluxes and mechanisms governing CaCO3 dissolution are highly uncertain. We present an observationally-constrained, probabilistic assessment of the global and regional CaCO3 budgets. Parameters governing pelagic CaCO3 export fluxes and dissolution rates are sampled using a Latin-Hypercube scheme to construct a 1000 member ensemble with the Bern3D ocean model. Ensemble results are constrained by comparing simulated and observation-based fields of excess dissolved calcium carbonate (TA*). The minerals calcite and aragonite are modelled explicitly and ocean–sediment fluxes are considered. For local dissolution rates either a strong, a weak or no dependency on CaCO3 saturation is assumed. Median (68 % confidence interval) global CaCO3 export is 0.82 (0.67–0.98) Gt PIC yr−1, within the lower half of previously published estimates (0.4–1.8 Gt PIC yr−1). The spatial pattern of CaCO3 export is broadly consistent with earlier assessments. Export is large in the Southern Ocean, the tropical Indo–Pacific, the northern Pacific and relatively small in the Atlantic. Dissolution within the 200 to 1500 m depth range (0.33; 0.26–0.40 Gt PIC yr−1) is substantially lower than inferred from the TA*-CFC age method (1 ± 0.5 Gt PIC yr−1). The latter estimate is likely biased high as the TA*-CFC method neglects transport. The constrained results are robust across a range of diapycnal mixing coefficients and, thus, ocean circulation strengths. Modelled ocean circulation and transport time scales for the different setups were further evaluated with CFC11 and radiocarbon observations. Parameters and mechanisms governing dissolution are hardly constrained by either the TA* data or the current compilation of CaCO3 flux measurements such that model realisations with and without saturation-dependent dissolution achieve skill. We suggest to apply saturation-independent dissolution rates in Earth System Models to minimise computational costs.

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Mateus, Nuno, Bruno Gonçalves, Juliana Exel, Pedro Esteves et Jaime Sampaio. « Short-term effects of adding 1-m wide to each side of the basketball court on youth players’ performance ». Cuadernos de Psicología del Deporte 20, n^o 3 (22 juillet 2020) : 82–94. http://dx.doi.org/10.6018/cpd.376321.

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El propósito de este estudio fue identificar los efectos a corto plazo en las respuestas físicas, técnicas y tácticas de jóvenes jugadores de baloncesto cuando la dimensión de la cancha aumenta 1-m de ancho en cada lado. Catorce jugadores jóvenes participaron en juegos simulados de baloncesto de 5 vs. 5, en dos condiciones diferentes: cancha regular (28x15m) y cancha más amplia (28x17m, 1-m de ancho a cada lado). Además de la evaluación de los indicadores físicos y técnicos, también se utilizaron datos de posición para calcular las siguientes variables: distancia al oponente más cercano, distancia al compañero de equipo más cercano, coeficiente de dispersión del equipo y distancia entre los centroides de los equipos. Los resultados indicaron que, en la condición de cancha más amplia, la dispersión de las trayectorias de movimiento de los jugadores durante la fase ofensiva aumentó, lo que tuvo ligeras repercusiones en sus respuestas físicas y en los patrones de juego de los equipos. En contrapartida, durante la fase defensiva, los jugadores tienden a moverse dentro de las referencias espaciales regulares, independientemente de la manipulación del ancho de la cancha. En general, este estudio enfatiza que los efectos a corto plazo de cambiar las dimensiones de la cancha son relativamente ligeros, lo que sugiere que las restricciones informativas pueden requerir bastante más tiempo para producir cambios concretos en el rendimiento de los jugadores. This study aimed to identify short-term effects in basketball players’ physical responses, technical performance, and tactical behaviour when the court dimension is increased 1-m wide to each side. Fourteen youth players participated in 5 vs. 5 simulated basketball games, under two different conditions: regular court (28x15m) and wider court (28x17m, 1-m wider for each side). Besides the assessment of physical and technical indicators, positional data were also used to compute the following variables: distance to the nearest opponent, distance to the nearest teammate, stretch-index and distance between centroids. Results indicated that in the wider court condition, the dispersion of player’s displacement trajectories during the offensive phase increased, which had slight repercussions on their physical responses and in the teams’ playing patterns. Conversely, during the defensive phase, players tended to move within the regular spatial references, regardless of court width manipulation. Overall, this study emphasizes that short-term effects of changing the court dimensions are relatively negligible, suggesting that informational constraints might require longer time-scales to yield robust changes in players’ performance. Este estudo teve como objectivo identificar os efeitos a curto prazo na performance física, técnica e tática de jovens jogadores de basquetebol, quando a largura do campo é aumentada 1-m para cada lado. Catorze jovens jogadores participaram em jogos simulados de 5 vs. 5, em dois contextos distintos: campo regular (28x17m) e campo amplo (28x17m, 1-m mais largo para ambos os lados). Paralelamente à avaliação de indicadores físicos e técnicos, foram também recolhidos dados posicionais, com o intuito de calcular as seguintes variáveis: distância ao oponente mais próximo, distância ao companheiro de equipa mais próximo, coeficiente de dispersão da equipa e distancia entre os centroides das equipas. Os resultados demonstraram que no contexto de campo amplo, a dispersão das trajetórias de movimento dos jogadores aumentou durante a fase ofensiva, o que acarretou ligeiras repercussões nos perfis físicos e nos padrões de jogo das equipas. Em contrapartida, durante a fase defensiva, os jogadores tendem a mover-se dentro dos referenciais espaciais, independentemente da manipulação do tamanho do campo. No geral, este estudo realçou que os efeitos a curto prazo de alterar as dimensões do campo são pouco expressivos, o que sugere que os constrangimentos de informação podem requerer substancialmente mais tempo para produzir alterações concretas no rendimento dos jogadores.

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Maioni, Melissa. « Il livello di speranza nei pazienti oncologici in cura chemioterapica. Un’indagine sperimentale / The level of hope in the cancer patients receiving chemotherapy. An experimental investigation ». Medicina e Morale 67, n^o 5 (11 décembre 2018) : 525–43. http://dx.doi.org/10.4081/mem.2018.555.

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La speranza è una caratteristica multidimensionale che coinvolge diverse dimensioni umane, il cui costrutto è stato più volte studiato in molteplici ambiti disciplinari. Il presente studio si propone di: valutare l’impatto della patologia in relazione al livello di speranza; comparare il livello di speranza con altre variabili cliniche e socio-demografiche, attraverso lo studio di 83 pazienti oncologici del Policlinico Campus Bio-Medico di Roma in cura chemioterapica, e di 83 soggetti sani, con caratteristiche socio-demografiche comparabili al campione clinico, a cui sono state sottoposte due scale: l’HHI (Herth Hope Scale) e la SF-12 (Questionario sullo stato di salute). L’analisi statistica utilizzata è finalizzata a valutare l’interdipendenza lineare tra le due variabili considerate (la speranza e lo stato di salute) sulla popolazione in generale e nelle sottopopolazioni considerate, tramite il calcolo dell’indice R2. I risultati mostrano che: a) il campione sperimentale composto per l’84,3% da pazienti affetti da cancro al IV stadio, ha mediamente un medio livello di speranza (media ± es = 35.47 ± 0.78); b) non emerge una correlazione significativa tra lo stato di salute e il livello di speranza; c) non emergono differenze significative riguardo il livello di speranza, mentre emergono delle differenze significative relativamente alla PCS (stato di salute fisica). I dati raccolti indicherebbero come la speranza sia una dimensione indipendente dalla diagnosi, dalla stadiazione della patologia, dal sesso, dal tipo di ospedalizzazione, dallo stato civile e non si modifichi nelle varie fasce d’età. Sembrerebbe un costrutto che si mantiene stabile nel tempo e che viene scarsamente influenzato da altre variabili. ---------- Hope is a multidimensional characteristic that involves different human dimensions, the construction of which has been studied several times in multiple disciplinary fields. The present study aims to: assess the impact of the pathology in relation to the level of hope; compare the level of hope with other clinical and socio-demographic variables, through the study of 83 cancer patients receiving chemotherapy at the Policlinico Campus Bio-Medico in Rome, and 83 healthy subjects, with socio-demographic characteristics comparable to the clinical sample, who were given two scales: the HHI (Herth Hope Index) and the SF-12 (SF-12 Health Survey). The statistical analysis used is aimed at assessing the linear interdependence between the two variables under consideration (hope and health) for the general population and the subpopulations under consideration, by calculating the R2 index. The results show that: a) the experimental sample, 84.3% of which was composed of stage IV cancer patients, had an average hope level (mean ± es = 35.47 ± 0.78); b) there was no significant correlation between health and hope; c) there were no significant differences in hope levels, while there were significant differences in physical health (PCS). The data collected would indicate that hope is a dimension independent of diagnosis, disease stage, sex, type of hospitalization, marital status and does not change in the various age groups. It would seem to be a construct that remains stable over time and is poorly influenced by other variables.

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Ma, Yandong, Jingbo Zhao, Tianjie Shao, Zhifeng Jia, Zhiqiang Zhao et Zilong Guan. « Hydrological Cycle and Lake Water Source Indicated by Microrelief-Evaporite-Vegetation-Runoff Assemblage of Badain Jaran Desert ». Water 11, n^o 7 (29 juin 2019) : 1350. http://dx.doi.org/10.3390/w11071350.

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The hydrologic process of the sandy desert remains a focus in research in arid areas. Three major natural phenomena that can indicate the hydrological cycle in the extremely dry Badain Jaran Desert were found, namely the assemblage of megadune microrelief and evaporite, megadune vegetation and microrelief, as well as lakeside runoff and vegetation. The microrelief sand layer water, evaporite minerals, and lakeside hydrogeological features were analyzed by the drying and weighing method, environmental scanning electron microscopy with energy spectrum analysis functions, and a hydrogeological borehole survey. The water content of the microrelief 0–0.5 m sand layer is between 4.7% and 9.3%. The evaporite minerals are mainly composed of calcite (CaCO3) and gypsum (CaSO4). The shallow groundwater system in the off-shore area of lakes consists of an aeolian sand layer, a peat layer, and a lacustrine sedimentary layer, and the phreatic water with a thickness of 20 cm to 40 cm is reserved in the bottom of aeolian sand layer with a peat layer as a waterproof baseboard. Based on these results, the above three natural phenomena can be explained as follows: (1) The assemblage of megadune microrelief and evaporite was caused by the outcropping of water from megadune vadose zone in the form of preferential flow for a long time. Its leading edge differential wind erosion and calcium cemented fine sand layer indicate that water from the megadune vadose zone moves to and recharges the microrelief water along the micro-scale fine sand layer, during which, it features a multiple layer as it is controlled by a vertical dune bedding structure. (2) The small-scale assemblage of megadune vegetation and microrelief indicates that the water from the megadune vadose zone moved laterally and led to vegetation development, and the assemblage of microrelief and vegetation at a slope scale indicates that the vadose zone water presented multilayer enrichment and runoff producing due, to a great extent, to the bedding structures of different spacial locations. (3) The assemblage of lakeside runoff and vegetation is related to the phreatic water recharged by precipitation surrounding the lake, which indicates that the megadune water recharged by precipitation moved to the bottom of the megadune and constituted supply to the lake water. The three assemblages fully demonstrate that the megadune water recharged by precipitation in this desert could recharge the groundwater water and even lake water in the form of preferential flow due to the control of the bedding structure of different scales within the megadune. The results of lake water balance and the occurrence conditions of phreatic water surrounding the lake imply that the precipitation in this desert plays an important role in sustaining the lake. This study provides reliable evidence for revealing the essence of the hydrological cycle and the source of lake water in the Badain Jaran Desert, which indicates that although precipitation is small, it cannot be ignored in arid sandy desert areas.

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Lavaniegos, B. E., O. Molina -González et M. Murcia -Riaño. « ZOOPLANKTON FUNCTIONAL GROUPS FROM THE CALIFORNIA CURRENT AND CLIMATE VARIABILITY DURING 1997-2013 ». CICIMAR Oceánides 30, n^o 1 (27 juin 2015) : 45. http://dx.doi.org/10.37543/oceanides.v30i1.143.

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Zooplankton plays an important role in recycling matter and energy trough the pelagic ecosystem. The California Current is one of the large marine ecosystems with high productivity and bio-physical variability at multiple time scales. An interannual scale or longer periods requires data series sufficiently long to ensure reliable averages of zooplankton abundance in order to estimate their low frequency variability. Here, tendencies in physical and biological variables are presented for the period 1997-2013 with data obtained from IMECOCAL cruises in the Mexican sector of the California Current. The area was divided into four regions, two oceanic (off North and Central Baja California) and two neritic (Vizcaino bay and Gulf of Ulloa). Sea surface temperature (SST) and El Niño Oceanic Index (ONI) showed correlation in all areas, while extratropical indices (PDO and NPGO) exhibited different tendencies among the regions. The PDO had significant correlation with SST only in the central and Vizcaino bay regions. The NPGO was not correlated with temperature but presented significantly strong correlation with sea surface salinity in all regions, which has been attributed to changes in large-scale circulation of the north Pacific subtropical gyre. In spite of a significant influence of the El Niño Southern Oscillation (ENSO) in SST, the correlation between ONI and zooplankton abundance was limited to gelatinous herbivorous (tunicates) from the North region. Local influence was remarkable in Vizcaino bay where the tunicates showed a period of negative abundance anomalies (2000-2004) followed by increasing positive anomalies between 2005 and 2013 associated with positive upwelling index anomalies. Geometric mean abundance of salps (per oceanographic cruise) averaged in Vizcaino bay 33.3 ind m-3 during 2005-2013 compared to 1.4 ind m-3 in 2000-2004. Salps partially displaced crustacean herbivores since they compete for feeding particles; copepods decreased from 88.2 ind m-3 during 2000-2004 to 59.7 ind m-3 in 2005-2013; and euphausiids from 16.1 ind m-3 to 10.4 ind m-3. In the oceanic domain a period of saline stratification during 2002-2006 was associated with positive anomalies of all trophic groups (crustaceans, tunicates and carnivores). Alternation of particular taxa of tunicates and carnivores is discussed. The increase of gelatinous organisms associated to higher stratification in the oceanic region and enhanced upwellng in the coastal shelf appears to be in detriment of crustaceans, though the time-series are short to outline a more defined trend. That tendency is particularly disturbing in Vizcaino bay affecting the availability of food for fishes and other predators. Grupos funcionales de zooplancton de la corriente de California y variabilidad climática durante 1997-2013 El zooplancton juega un papel fundamental en el flujo de materia y energía en el ecosistema pelágico. La Corriente de California es uno de los grandes ecosistemas marinos con elevada productividad y amplia variabilidad físico-biológica a múltiples escalas temporales. A escala interanual y de mayor periodo es necesario contar con series de datos lo suficientemente extensas temporalmente que permitan calcular promedios robustos de la abundancia del zooplancton y poder estimar la variabilidad de baja frecuencia. En el presente estudio se muestran las tendencias en variables físicas y biológicas del periodo 1997-2013 de los datos obtenidos por los cruceros IMECOCAL en el sector mexicano de la Corriente de California. El área fue dividida en cuatro regiones, dos oceánicas (frente a Baja California, Norte y Central) y dos neríticas (Bahía Vizcaíno y Golfo de Ulloa). En todas las regiones la temperatura superficial del mar (TSM) estuvo correlacionada con El Niño Oceanic Index (ONI). Los índices extratropicales (PDO y NPGO) mostraron diferentes tendencias entre regiones. El PDO tuvo fuerte correlación con la TSM solo en la región central y en Bahía Vizcaíno. El NPGO no se correlacionó con la temperatura pero presentó correlación significativa con la salinidad superficial del mar en todas las regiones, lo cual ha sido atribuido a cambios en la circulación a gran escala del giro subtropical del Pacífico norte. A pesar de una influencia significativa del ENSO en la TSM, la correlación entre el ONI y la abundancia del zooplancton estuvo limitada a los herbívoros gelatinosos (tunicados) de la región Norte. La influencia local fue notable en Bahía Vizcaíno donde los tunicados mostraron un periodo de anomalías negativas (2000-2004) seguido por un periodo con anomalías positivas de creciente amplitud entre 2005 y 2013 asociadas con anomalías positivas del índice de surgencias. La abundancia expresada mediante medias geométricas de salpas (por crucero) mostró en Bahía Vizcaíno 33.3 ind m-3 durante 2005-2013 comparada con 1.4 ind m-3 en 2000-2004. Las salpas desplazaron parcialmente a los crustáceos herbívoros puesto que ambos compiten por las partículas de alimento; los copépodos disminuyeron de 88.2 ind m-3 durante 2000-2004 a 59.7 ind m-3 en 2005-2013; los eufáusidos disminuyeron de 16.1 ind m-3 a 10.4 ind m-3. En el dominio oceánico un periodo de estratificación salina durante 2002-2006 estuvo asociado con anomalías positivas de todos los grupos tróficos (crustáceos, tunicados y carnívoros). Se discute la alternancia de taxa particulares de tunicados y carnívoros. El incremento de organismos gelatinosos asociado a una mayor estratificación en la región oceánica y a la intensificación de las surgencias en la plataforma costera parece ir en detrimento de los crustáceos, aunque las series de tiempo son cortas para establecer una tendencia definida. Dicha tendencia es particularmente perturbadora en Bahía Vizcaíno al afectar la disponibilidad de alimento para peces y otros depredadores.

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Lavaniegos, B. E., O. Molina -González et M. Murcia -Riaño. « ZOOPLANKTON FUNCTIONAL GROUPS FROM THE CALIFORNIA CURRENT AND CLIMATE VARIABILITY DURING 1997-2013 ». CICIMAR Oceánides 30, n^o 1 (27 juin 2015) : 45. http://dx.doi.org/10.37543/oceanides.v30i1.143.

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Zooplankton plays an important role in recycling matter and energy trough the pelagic ecosystem. The California Current is one of the large marine ecosystems with high productivity and bio-physical variability at multiple time scales. An interannual scale or longer periods requires data series sufficiently long to ensure reliable averages of zooplankton abundance in order to estimate their low frequency variability. Here, tendencies in physical and biological variables are presented for the period 1997-2013 with data obtained from IMECOCAL cruises in the Mexican sector of the California Current. The area was divided into four regions, two oceanic (off North and Central Baja California) and two neritic (Vizcaino bay and Gulf of Ulloa). Sea surface temperature (SST) and El Niño Oceanic Index (ONI) showed correlation in all areas, while extratropical indices (PDO and NPGO) exhibited different tendencies among the regions. The PDO had significant correlation with SST only in the central and Vizcaino bay regions. The NPGO was not correlated with temperature but presented significantly strong correlation with sea surface salinity in all regions, which has been attributed to changes in large-scale circulation of the north Pacific subtropical gyre. In spite of a significant influence of the El Niño Southern Oscillation (ENSO) in SST, the correlation between ONI and zooplankton abundance was limited to gelatinous herbivorous (tunicates) from the North region. Local influence was remarkable in Vizcaino bay where the tunicates showed a period of negative abundance anomalies (2000-2004) followed by increasing positive anomalies between 2005 and 2013 associated with positive upwelling index anomalies. Geometric mean abundance of salps (per oceanographic cruise) averaged in Vizcaino bay 33.3 ind m-3 during 2005-2013 compared to 1.4 ind m-3 in 2000-2004. Salps partially displaced crustacean herbivores since they compete for feeding particles; copepods decreased from 88.2 ind m-3 during 2000-2004 to 59.7 ind m-3 in 2005-2013; and euphausiids from 16.1 ind m-3 to 10.4 ind m-3. In the oceanic domain a period of saline stratification during 2002-2006 was associated with positive anomalies of all trophic groups (crustaceans, tunicates and carnivores). Alternation of particular taxa of tunicates and carnivores is discussed. The increase of gelatinous organisms associated to higher stratification in the oceanic region and enhanced upwellng in the coastal shelf appears to be in detriment of crustaceans, though the time-series are short to outline a more defined trend. That tendency is particularly disturbing in Vizcaino bay affecting the availability of food for fishes and other predators. Grupos funcionales de zooplancton de la corriente de California y variabilidad climática durante 1997-2013 El zooplancton juega un papel fundamental en el flujo de materia y energía en el ecosistema pelágico. La Corriente de California es uno de los grandes ecosistemas marinos con elevada productividad y amplia variabilidad físico-biológica a múltiples escalas temporales. A escala interanual y de mayor periodo es necesario contar con series de datos lo suficientemente extensas temporalmente que permitan calcular promedios robustos de la abundancia del zooplancton y poder estimar la variabilidad de baja frecuencia. En el presente estudio se muestran las tendencias en variables físicas y biológicas del periodo 1997-2013 de los datos obtenidos por los cruceros IMECOCAL en el sector mexicano de la Corriente de California. El área fue dividida en cuatro regiones, dos oceánicas (frente a Baja California, Norte y Central) y dos neríticas (Bahía Vizcaíno y Golfo de Ulloa). En todas las regiones la temperatura superficial del mar (TSM) estuvo correlacionada con El Niño Oceanic Index (ONI). Los índices extratropicales (PDO y NPGO) mostraron diferentes tendencias entre regiones. El PDO tuvo fuerte correlación con la TSM solo en la región central y en Bahía Vizcaíno. El NPGO no se correlacionó con la temperatura pero presentó correlación significativa con la salinidad superficial del mar en todas las regiones, lo cual ha sido atribuido a cambios en la circulación a gran escala del giro subtropical del Pacífico norte. A pesar de una influencia significativa del ENSO en la TSM, la correlación entre el ONI y la abundancia del zooplancton estuvo limitada a los herbívoros gelatinosos (tunicados) de la región Norte. La influencia local fue notable en Bahía Vizcaíno donde los tunicados mostraron un periodo de anomalías negativas (2000-2004) seguido por un periodo con anomalías positivas de creciente amplitud entre 2005 y 2013 asociadas con anomalías positivas del índice de surgencias. La abundancia expresada mediante medias geométricas de salpas (por crucero) mostró en Bahía Vizcaíno 33.3 ind m-3 durante 2005-2013 comparada con 1.4 ind m-3 en 2000-2004. Las salpas desplazaron parcialmente a los crustáceos herbívoros puesto que ambos compiten por las partículas de alimento; los copépodos disminuyeron de 88.2 ind m-3 durante 2000-2004 a 59.7 ind m-3 en 2005-2013; los eufáusidos disminuyeron de 16.1 ind m-3 a 10.4 ind m-3. En el dominio oceánico un periodo de estratificación salina durante 2002-2006 estuvo asociado con anomalías positivas de todos los grupos tróficos (crustáceos, tunicados y carnívoros). Se discute la alternancia de taxa particulares de tunicados y carnívoros. El incremento de organismos gelatinosos asociado a una mayor estratificación en la región oceánica y a la intensificación de las surgencias en la plataforma costera parece ir en detrimento de los crustáceos, aunque las series de tiempo son cortas para establecer una tendencia definida. Dicha tendencia es particularmente perturbadora en Bahía Vizcaíno al afectar la disponibilidad de alimento para peces y otros depredadores.

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Winterle, James R., et William M. Murphy. « Time Scales for Dissolution of Calcite Fracture Fillings and Implications for Saturated Zone Radionuclide Transport at Yucca Mountain, Nevada ». MRS Proceedings 556 (1999). http://dx.doi.org/10.1557/proc-556-713.

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AbstractAn analysis was performed to estimate time scales for dissolution of calcite fracture fillings in the fractured tuff aquifer that underlies Yucca Mountain (YM), Nevada, where groundwater is chemically undersaturated with respect to calcite. The impetus for this analysis originates from speculation that undissolved calcite in the saturated zone is evidence for limited diffusive exchange between fracture and matrix waters. Assuming that matrix diffusion is the rate-limiting process, the time scale for dissolution of calcite fracture fillings depends on the amount of calcite initially deposited, the distance between flowing fractures, the degree of chemical disequilibrium, and the rate of diffusion. Assuming geochemistry of J-13 well water in free-flowing fractures, estimated time scales for complete dissolution of matrix-entrapped calcite range from about 104yr for a 2 mm-thick deposit located I m from a flowing fracture, to over 107 yr for a 2 cm-thick deposit located 100 m from a flowing fracture. We conclude that, given the geochemical and hydrologic characteristics observed at YM, the persistence of calcite minerals over geologic time scales in aquifers where flowing water is under-saturated with calcite does not necessarily preclude matrix diffusion as a dilution mechanism. However, our model suggests that the effective spacing between flowing fractures may be large enough to diminish the overall benefit of matrix diffusion to proposed high-level waste repository performance.

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Cranga, M., L. Trotignon, C. Martial et E. Castelier. « Simulation of the Evolution of a Clay Engineered Barrier by Interaction With Granitic Groundwater : Dynamics and Characteristic Time Scales ». MRS Proceedings 506 (1997). http://dx.doi.org/10.1557/proc-506-629.

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ABSTRACTThe chemical evolution of a clay engineered barrier in a deep repository interacting with various groundwaters is predicted using the TRIO-EF code supported by additional models tested against experimental data. Main results of this work are related to the long term evolution of the porewater and the buffering effect of the clay barrier in the presence of ion exchange sites and calcite, when exposed to representative granitic groundwaters or more acidic or alkaline waters.

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Cole, Selina R., David F. Wright et Jeffrey R. Thompson. « Calcite-aragonite seas as a driver of echinoderm evolution ? Experimental insight and deep-time decoupling ». Geology, 12 septembre 2023. http://dx.doi.org/10.1130/g51444.1.

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Seawater magnesium (Mg) and calcium (Ca) have undergone secular fluctuations throughout the Phanerozoic, controlling whether the dominant calcium carbonate precipitant is calcite or aragonite + high-Mg calcite. Although these oscillations in seawater Mg/Ca ratios have been implicated as an important control on Phanerozoic diversification of calcifying marine organisms, determining the degree to which Mg/Ca ratios affected different clades requires integration of experimental data with historical patterns of biodiversity from the fossil record. We explore short-term and long-term responses of echinoderms to shifting calcite-aragonite seas by combining experimental and deep-time biodiversity investigations. While experimental results support a strong relationship between Mg/Ca ratios and short-term echinoderm regeneration rates, patterns of Phanerozoic echinoderm diversification dynamics show no correspondence with Mg/Ca ratios or calcite-aragonite sea transitions. This decoupling between short- and long-term responses of echinoderms to seawater Mg/Ca ratios suggests echinoderms were relatively unaffected by seawater chemistry throughout their evolutionary history, possibly due to their ability to alter skeletal Mg fractionation and/or adapt to gradual shifts in seawater chemistry. Notably, our results indicate a strict uniformitarian extrapolation of experimental results over geological time scales may not be appropriate for many calcifying marine invertebrates. Instead, the effect of seawater Mg/Ca ratios should be evaluated for individual clades using both experimental and deep-time biodiversity data in a time series.

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Placencia-Gόmez, Edmundo, Judith Robinson, Lee Slater et Nikolla P. Qafoku. « Spectral induced polarization monitoring of induced calcite precipitation in subsurface sediments ». Geophysical Journal International, 17 août 2022. http://dx.doi.org/10.1093/gji/ggac318.

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Summary Co-precipitation of contaminants within the crystalline structure of calcite is a promising natural attenuation or remedial technology being considered at contaminated sites. We explore the sensitivity of the spectral induced polarization (SIP) method to induced calcite precipitation in natural sediments as a path forward to non-invasively monitor these sites. We performed time-lapse column experiments using phased (I-IV) injections over 40 days on natural sediments from the Hanford Site (Washington State, USA). In the phased injections, abiotic calcite precipitation was induced and confirmed to have occurred. Previous work on glass beads and homogeneous sand was limited to high frequency detection of calcite, however in this work we observed the development of two polarization mechanisms, one at high frequency (>100 Hz) and one at low frequency (< 100 Hz). Based on the characteristic frequencies from the SIP high and low frequency regimes, characteristic length scales (L) were computed where the adsorption mode of Na+ versus Ca2+ was compared by using diffusion coefficients corresponding to Na+ versus an arithmetically averaged value for Na+ and Ca2+. Using the diffusion coefficient of Na+, the high frequency L was found to correlate well with the size of the calcite crystals. The low frequency L correlated well with the individual natural sediment grain sizes within the columns. During late experimental times (day 36 and 40), the characteristic low frequency in two of the experimental columns shifted to lower frequencies (<0.001 Hz) which may signify SIP sensitivity of the formed calcite with the sediment grains. In field applications, the development of a low frequency polarization length scale to monitor calcite precipitation is promising for field monitoring applications, however further laboratory work needs to be performed to examine the SIP sensitivity of calcite formation in the presence of natural sediments.

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Hale, Sina, Elisabete Trindade Pedrosa, Arne Jacob, Marcel Reinhardt, Frieder Enzmann, Michael Kersten, Christoph Butscher et Philipp Blum. « Upscaling calcite dissolution rates in a tight reservoir sandstone ». Environmental Earth Sciences 81, n^o 11 (19 mai 2022). http://dx.doi.org/10.1007/s12665-022-10399-5.

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AbstractCalcite is a highly abundant mineral in the Earth’s crust and occurs as a cement phase in numerous siliciclastic sediments, where it often represents the most reactive component when a fluid percolates through the rock. Hence, the objective of this study is to derive calcite dissolution rates on different scales in a reservoir sandstone using mineral surface experiments combined with vertical scanning interferometry (VSI) and two types of core plug experiments. The 3D geometry of the calcite cement phase inside the rock cores was characterized by X-ray micro-computed tomography (µXCT) and was used to attempt dissolution rate upscaling from the mineral surface to the core scale. Initially (without upscaling), our comparison of the far-from-equilibrium dissolution rates at the mineral surface (µm-mm-scale, low fluid residence time) and the surface normalized dissolution rates obtained from the core experiments (cm-scale, high fluid residence time) revealed differences of 0.5–2 orders of magnitude. The µXCT geometric surface area connected to the open pore space $$\left( {GSA_{{Cc,{\text{open}}}} } \right)$$ G S A C c , open considers the fluid accessibility of the heterogeneously distributed calcite cement that can largely vary between individual samples, but greatly affects the effective dissolution rates. Using this parameter to upscale the rates from the µm- to the cm-scale, the deviation of the upscaled total dissolution rates from the measured total dissolution rates was less than one order of magnitude for all investigated rock cores. Thus, $$GSA_{{Cc,{\text{open}}}}$$ G S A C c , open showed to be reasonably suitable for upscaling the mineral surface rates to the core scale.

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Di Biagio, Claudia, Jean-François Doussin, Mathieu Cazaunau, Edouard Pangui, Juan Cuesta, Pasquale Sellitto, Milagros Ródenas et Paola Formenti. « Infrared optical signature reveals the source–dependency and along–transport evolution of dust mineralogy as shown by laboratory study ». Scientific Reports 13, n^o 1 (15 août 2023). http://dx.doi.org/10.1038/s41598-023-39336-7.

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AbstractAdvancing knowledge of the mineralogical composition of dust is key for understanding and predicting its climate and environmental impacts. The variability of dust mineralogy from one source to another and its evolution during atmospheric transport is not measured at large scale. In this study we use laboratory measurements to demonstrate that the extinction signature of suspended dust aerosols in the 740 − 1250 cm−1 atmospheric window can be used to derive dust mineralogy in terms of the main infrared − active minerals, namely quartz, clays, feldspars and calcite. Various spectral signatures in dust extinction enable to distinguish between multiple global sources with changing composition, whereas modifications of the dust extinction spectra with time inform on size − dependent particles mineralogy changes during transport. The present study confirms that spectral and hyperspectral infrared remote sensing observations offer great potential for elucidating the size − segregated mineralogy of airborne dust at regional and global scales.

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Ko, Saebom, Yue Zhao, Xin Wang, Zhaoyi (Joey) Dai, Samridhdi Paudyal, Chong Dai, Amy Kan et Mason Tomson. « Deposit Prevention of Mineral Scales Using a Universal Dispersant of Carboxymethyl Cellulose ». SPE Journal, 1 juillet 2022, 1–11. http://dx.doi.org/10.2118/210596-pa.

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Summary As the world’s demands for energy and water increase, innovative technologies have been implemented to produce more energy and water, sometimes in unconventional fields. It brought in new challenges of highly saline water formation and souring of wellbore or formation. Under these circumstances, the conventional threshold inhibition methods might be ineffective in controlling mineral scales. To develop a new feasible method to manage more difficult mineral scale problems, we investigated a single approach to prevent complex mineral scales from deposition using a water-soluble polymer of carboxymethyl cellulose (CMC). We also examine the effect of the combination of conventional threshold scale inhibitors and CMC for complex mineral scale control. Our results showed that a polymeric dispersant of CMC successfully prevented zinc and lead sulfide, barium and calcium sulfate, and calcium and iron carbonate scales from deposition, similar to what we had observed previously with iron sulfide. CMC combined with phosphonate inhibitors of diethylenetriamine penta(methylene phosphonic) acid (DTPMP) or hexamethylene diamine tetra(methylene phosphonic) acid (HDTMP) also enhanced the inhibition performance of phosphonate inhibitors. PbS and ZnS were successfully dispersed in the presence of CMC as low concentrations of CMC as 2 mg/L for PbS and 5 mg/L for ZnS in solution passed through a 1.2-μm pore-size membrane. For barite scale control, the combination of CMC and DTPMP inhibited barite formation for 2 hours, while CMC for only 5 minutes and DTPMP for 18 minutes. The mass of barite deposit on 316 stainless steel was reduced by three-order magnitudes in the combination of DTPMP and CMC, compared with DTPMP alone. The scanning electron microscope (SEM) image of barite precipitated in CMC and DTPMP showed that its morphology was no longer a rhombic plate. According to the transmission electron microscope (TEM) image, the surface of barite was covered by CMC, and after a 6-hour reaction, its size was 45.6 nm, which was slightly larger than that at induction time (10–35 nm). Gypsum crystal formation was also inhibited for at least 6 hours in combining CMC and HDTMP. For calcite scale control in the presence of 20 mg/L of CMC, calcite formations and growth were prevented for 134 minutes, and particle sizes remained in the nanosize range (average particle size of 396 nm) for a 15-hour reaction. Iron carbonate treated with 200 mg/L of CMC-250k and CMC-700k was dispersed for at least 2 hours under our experimental conditions. This study demonstrated that CMC effectively performed as a universal dispersant bringing a new feasible method to manage complex mineral scale problems.

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Simonet Roda, Maria, Erika Griesshaber, Lucia Angiolini, Claire Rollion-Bard, Elizabeth M. Harper, Maria Aleksandra Bitner, Sara Milner Garcia et al. « The architecture of Recent brachiopod shells : diversity of biocrystal and biopolymer assemblages in rhynchonellide, terebratulide, thecideide and craniide shells ». Marine Biology 169, n^o 1 (20 novembre 2021). http://dx.doi.org/10.1007/s00227-021-03962-4.

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AbstractBiological hard tissues are a rich source of design concepts for the generation of advanced materials. They represent the most important library of information on the evolution of life and its environmental conditions. Organisms produce soft and hard tissues in a bottom-up process, a construction principle that is intrinsic to biologically secreted materials. This process emerged early on in the geological record, with the onset of biological mineralization. The phylum Brachiopoda is a marine animal group that has an excellent and continuous fossil record from the early Cambrian to the Recent. Throughout this time interval, the Brachiopoda secreted phosphate and carbonate shells and populated many and highly diverse marine habitats. This required great flexibility in the adaptation of soft and hard tissues to the different marine environments and living conditions. This review presents, juxtaposes and discusses the main modes of mineral and biopolymer organization in Recent, carbonate shell-producing, brachiopods. We describe shell tissue characteristics for taxa of the orders Rhynchonellida, Terebratulida, Thecideida and Craniida. We highlight modes of calcite and organic matrix assembly at the macro-, micro-, and nano-scales based on results obtained by Electron Backscatter Diffraction, Atomic Force Microscopy, Field Emission Scanning Electron Microscopy and Scanning Transmission Electron Microscopy. We show variation in composite hard tissue organization for taxa with different lifestyles, visualize nanometer-scale calcite assemblies for rhynchonellide and terebratulide fibers, highlight thecideide shell microstructure, texture and chemistry characteristics, and discuss the feasibility to use thecideide shells as archives of proxies for paleoenvironment and paleoclimate reconstructions.

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Ross, Benjamin. « Gas-Phase Transport of Carbon-14 Released from Nuclear Waste into the Unsaturated Zone ». MRS Proceedings 112 (1987). http://dx.doi.org/10.1557/proc-112-273.

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AbstractGas-phase carbon-14 dioxide released from spent fuel buried in unsaturated rocks will move upward by molecular diffusion and advection. The flux resulting from molecular diffusion will be determined by the concentration gradient of gaseous carbon-14 dioxide. Advection will be caused by density-driven flow of the pore gas. Such flow occurs under present conditions as a result of annual and diurnal temperature changes and differences in chemical composition between pore gas and air, and it will be enhanced when the spent fuel heats the rock. The advective flux will be determined by the gas-phase concentration of carbon-14 and by the velocity of convective flow of the pore gas. Gas-phase concentrations of carbon-14 dioxide will be strongly influenced by isotopic exchange with bicarbonate dissolved in water that is retained in the unsaturated zone by capillary forces. Isotopic equilibrium between these two phases will be attained very rapidly on repository time scales. If the liquid phase is saturated with calcium carbonate, precipitation of calcite may provide a sink for removal of carbon-14 from the mobile phases.

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Weldeghebriel, Mebrahtu F., et Tim K. Lowenstein. « Seafloor hydrothermal systems control long-term changes in seawater [Li ⁺ ] : Evidence from fluid inclusions ». Science Advances 9, n^o 30 (28 juillet 2023). http://dx.doi.org/10.1126/sciadv.adf1605.

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Secular variations in the major ion chemistry and isotopic composition of seawater on multimillion-year time scales are well documented, but the causes of these changes are debated. Fluid inclusions in marine halite indicate that the Li concentration in seawater [Li + ] SW declined sevenfold over the past 150 million years (Ma) from ~184 μmol/kg H 2 O at 150 Ma ago to 27 μmol/kg H 2 O today. Modeling of the lithium geochemical cycle shows that the decrease in [Li + ] SW was controlled chiefly by long-term decreases in ocean crust production rates and mid-ocean ridge and ridge flank hydrothermal fluxes without requiring changes in continental weathering fluxes. The decrease in [Li + ] SW parallels the 150 Ma increase in seawater Mg 2+ /Ca 2+ and 87 Sr/ 86 Sr, and the change from calcite to aragonite seas, KCl to MgSO 4 evaporites, and greenhouse to icehouse climates, all of which point to the importance of plate tectonic activity in regulating the composition of Earth’s hydrosphere and atmosphere.

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Dai, Zhaoyi, Yue Zhao, Xin Wang, Amy T. Kan et Mason Tomson. « Novel Barite Crystallization and Inhibition Model Based on Surface Adsorption ». SPE Journal, 1 février 2023, 1–11. http://dx.doi.org/10.2118/214327-pa.

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Summary Inorganic mineral crystallization is a critical process for numerous industrial and geoengineering processes, including oil and gas production and transportation, geothermal energy exploitation, membrane filtration, cooling tower, heat exchanger, to mention a few. Its unexpected formation can cause significant engineering, economic, and safety issues. Scale inhibitors have been widely used in various geoengineering projects as one of the most efficient and economic methods for mineral scale control. However, after decades of research, the inhibition mechanisms still remain unknown. This study applied a newly developed mechanistic mineral crystallization and inhibition model to barite, one of the most difficult mineral scales to be remediated. This new model assumes that inhibitors prolong the crystallization induction time by adsorbing onto the nucleus surface following a Langmuir-type adsorption isotherm and increasing the surface tension. The new model accurately predicts the barite crystallization induction time without or with 10 commonly used scale inhibitors. More importantly, the adsorption affinity constants (i.e., KL) fitted with the new model from the barite crystallization induction time matched well with those fitted from the direct inhibitor adsorption testing and from measuring barite crystal growth rate changes due to various inhibitors. A good correlation was also observed between the KL values of various inhibitors with barite from this study and those with other minerals (i.e., hydroxyapatite and calcite) from the literature. Such good agreements and correlations validated the adsorption mechanism adopted in the new mechanistic model. This study will deepen the understanding of mineral crystallization and inhibition mechanisms and improve scale management in various industrial and geoengineering processes.

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