Carbonate System Research Articles

Novel cage-like all-nitrogen molecular crystal stable under ambient conditions

Exploring whether cage-like molecular crystals similar to those in carbon systems exist in all-nitrogen systems is not only of great theoretical significance, but also of great practical application value as high-energy-density materials. Here, we predict a new type of cage-like all-nitrogen Td-N4 molecular crystal by using the CALYPSO method. The structure has mechanical and dynamic stability under ambient pressure. Moreover, Td-N4 molecular crystal has excellent thermal stability and can be stabilized to a high temperature of 2400 K. The reason why Td-N4 molecular crystal has such excellent stability is due to the high decomposition energy barrier (251.5 kJ/mol), and the most essential reason may be due to the strong double spherically aromatic of the molecule with the nucleus-independent chemical shift (NICS) of −70.5 ppm. It is worth noting that the energy density of the Td-N4 molecular crystal is 11.89 kJ/g, which is three times that of the TNT (4.3 kJ/g), twice that of HMX (5.7 kJ/g), and higher than that of the well-known cg-N structure (9.7 kJ/g). In addition, Td-N4 molecular crystal also has excellent properties with high Heat of detonation, detonation pressure and detonation velocity. The prediction of Td-N4 molecular crystal provides a very promising candidate for high energy density materials.

Uncertainty sources for measurable ocean carbonate chemistry variables

AbstractThe ocean carbonate system is critical to monitor because it plays a major role in regulating Earth's climate and marine ecosystems. It is monitored using a variety of measurements, and it is commonly understood that all components of seawater carbonate chemistry can be calculated when at least two carbonate system variables are measured. However, several recent studies have highlighted systematic discrepancies between calculated and directly measured carbonate chemistry variables and these discrepancies have large implications for efforts to measure and quantify the changing ocean carbon cycle. Given this, the Ocean Carbonate System Intercomparison Forum (OCSIF) was formed as a working group through the Ocean Carbon and Biogeochemistry program to coordinate and recommend research to quantify and/or reduce uncertainties and disagreements in measurable seawater carbonate system measurements and calculations, identify unknown or overlooked sources of these uncertainties, and provide recommendations for making progress on community efforts despite these uncertainties. With this paper we aim to (1) summarize recent progress toward quantifying and reducing carbonate system uncertainties; (2) advocate for research to further reduce and better quantify carbonate system measurement uncertainties; (3) present a small amount of new data, metadata, and analysis related to uncertainties in carbonate system measurements; and (4) restate and explain the rationales behind several OCSIF recommendations. We focus on open ocean carbonate chemistry, and caution that the considerations we discuss become further complicated in coastal, estuarine, and sedimentary environments.

PROCESSES OF FORMATION OF SODIUM BICARBONATE GROUNDWATER IN THE RAINWATER – SANDSTONE SYSTEM

In modeling, a study was made of the processes of the physical-chemical interaction between rainwater and sandstone. It was stated that as a result of the interaction, already in mineralization of water equal to 55 mg/l, there emerges a pure soda solution whose sharp oxidation properties, retaining up to 200 mg/l, change to sharp restorative when exceeding this value. At the mineralization of water equal to 30 mg/l, an intensive increase in the number of hydroxide ions in a solution makes it highly alkaline. The active removal of calcium from solution is due to the formation of not only solid phase calcite, whose share does not exceed 15 %, but largely limonite, whose content is as high as 25 %. The accumulation of high concentrations of sodium in a solution is caused by the absence of its secondary mineral formations in a wide range of the rock/water ratios. Under reservoir conditions, the solution is composed of carbonate. This solution, transferred from reservoir to surface conditions, undergoes transformation in the result of interaction with the atmosphere. A decrease in pH of the solution resulted in the acquisition of sharp oxidation properties, with the cation, sulfate, fluorine and chlorine contents remained at the level corresponding to the reservoir conditions and the cardinal changes affected the carbonate system components and silicon compounds. Hydrosilicate ion was transformed into precipitated silicon oxide. Carbonate ions were transformed into hydrocarbonate, and the additional hydrocarbonate ions were formed for the solution to preserve a state of equilibrium after the removal of the representative number of hydrosilicate ions therefrom. An amount of carbon required for their formation was extracted from the atmosphere. The solution became hydrocarbonate, with hydrosilicate ions almost disappeared therefrom. Different calculation options for model solution, which is in equilibrium with the atmosphere, correlate with the representative group of soda-type groundwater. The calculation results are confirmed by field observations over the authigenic mineral formation on a large part of the Russian territory.

Application of persulfate-assisted graphitic carbon, derived through pyrolysis of waste biomass, driven by visible light, for the removal of tetracycline from water: Mechanisms and performance influencing parameters

Sulfate radical based advanced oxidation process by using carbon-based materials has attracted widespread attention for removal of emerging contaminants in water. This paper reports the study on the efficacy of visible light activated persulfate (PS) – graphitic carbon (GC) system for the removal of tetracycline (TC) from water . Here GCs from residual agricultural biomass were synthesized via a facile and chemical-free pyrolysis route, and their characteristics were analyzed under varying thermal conditions, viz. temperature (550–950 °C) and heating rate (2.5–10 °C min−1). The GCs at high pyrolysis temperatures (> 700 °C) revealed graphitic and condensed aromatic carbon networks with enhanced textural properties, facilitating electron-mediated reactions through interconnected morphology. The methodology is derived from the research that shows certain pyrolysis derived carbon products are known to have transient photocurrent response, indicating semiconductor properties. Here, the visible light-driven GC/PS (950 °C, 5 °C min−1) system resulted in high TC removal efficiency of 91.23% within 180 min compared to other PS/GCs prepred under different conditions. The mass spectroscopy data shows that the GC/PS system successfully degraded TC into simpler products and achieved the highest mineralization efficiency of about 65.43 ± 3.62%. The radical scavenging experiments revealed that 1O2 and •OH were the dominant reactive oxygen species suppressing degradation of TC by 13% and 9%, respectively. It can be surmised that both radical and non-radical pathways facilitate TC degradation via dehydration, demethylation and oxidation of aromatic rings- due to both catalytic and physico-chemical properties of GC/PS .

Characterizing the Mechanisms of Ca and Mg Carbonate Ion-Pair Formation with Multi-Level Molecular Dynamics/Quantum Mechanics Simulations.

The carbonate minerals of Ca and Mg are abundant throughout the lithosphere and have recently garnered significant research interest as possible long-term carbon sinks in the sequestration of atmospheric carbon dioxide. Nonetheless, an understanding of the atomic-level processes comprising their mineralization remains limited. Here, we characterize and contrast the mechanisms of contact ion-pair formation in aqueous Ca and Mg carbonate systems, which represents the most fundamental step leading to the formation of their mineral solids. Utilizing multilevel embedded correlated wavefunction-based ab initio molecular dynamics/quantum mechanics simulations, we characterize not only the dynamics of these processes but also factors arising from the electronic structure of the involved species, revealing further details of the fundamentally different mechanisms for the interconversion between the contact ion-pairs and solvent-shared ion-pairs of Ca versus Mg carbonate.

Revisiting the relationship between the pore water carbon isotope gradient and bottom water oxygen concentrations

Reconstructing the oxygen content at the ocean floor provides insight into ocean circulation, ventilation, and carbon storage in the deep sea. The microbial breakdown of organic carbon within marine sediment through aerobic respiration consumes oxygen in the pore fluid and releases dissolved inorganic carbon. The offset in the carbon isotopic composition, δ13C, of epifaunal and infaunal foraminifera, Δδ13C, is considered to reflect the aerobic respiration of organic carbon and can be used to reconstruct the oxygen content of the bottom water. Previous work provided an empirical calibration that was suggested to be valid for oxygen reconstructions between 55 and 235 μmol kg−1. In this study, we apply a biogeochemical reactive transport model (RTM) to extend and update this calibration, allowing for the reconstruction of oxygen concentrations ([O2]) up to ∼300 μmol kg−1. Using the RTM and new bottom water [O2] and pore fluid measurements from Iberian Margin sediment cores, we also demonstrate that the calibration between the Δδ13C and bottom water [O2] must account for the coupled changes in the carbon system due to the respiration of organic carbon in the overlying ocean including the concentration and carbon isotopic composition of the dissolved inorganic carbon, and the δ13C of the organic carbon within the sediment column. We apply the improved calibration to reconstruct the changes in oxygen content at International Ocean Discovery Program (IODP) Site U1385 in the deep North Atlantic over the past 1.5 Myr.

Seasonal and spatial variability of CO2 emissions in a large tropical mangrove‐dominated delta

AbstractThis study quantified the seasonal and spatial variability of partial pressure of CO2 (pCO2) and water‐atmosphere CO2 fluxes in the Parnaíba River Delta, the largest delta in the Americas. It is a pristine equatorial, mangrove‐dominated environment located in a transitional between humid and semi‐arid climates, with marked seasonality in rainfall and river discharge. Major channels and bays were sampled during dry and wet seasons, with continuous measurements of pCO2, temperature, salinity, and wind velocity. Subsurface water samples were collected in discrete stations for pH, total alkalinity (TA), dissolved inorganic carbon (DIC), dissolved oxygen and chlorophyll a quantification. A significant positive correlation between carbonate system parameters with salinity was found in both periods, with salinity significantly higher in the dry season. Strong deviations of pCO2, TA, and DIC from two endmembers conservative mixing were found, particularly in mangrove‐dominated waters, due to organic matter degradation. The Delta showed high spatial variability of pCO2, with the highest values in mangrove‐dominated waters, moderate in the river‐dominated regions, and lowest in the high salinity areas, suggesting that pCO2 variability is likely controlled by a combination of river‐ocean mixing and biological processes (respiration and photosynthesis). The Delta outgasses about 20 times less CO2 in the dry season (9.06 ± 11.09 mmol m−2.d−1) than in the rainy season (209.68 ± 250.87 mmol m−2 d−1). Our results indicate this large mangrove‐dominated tropical delta is an important source of CO2 to the atmosphere, but a sharp decrease was observed during dry periods.

Caves, Karst Features and Speleological Heritage in Chapada Diamantina, Bahia, Brazil

Chapada Diamantina is among the best known and most visited landscapes in Brazil. Located in the state of Bahia, Northeast region of the country, it is characterized by mountains and plateaus that developed on Proterozoic sedimentary and metasedimentary rocks. Much of its territory is covered by carbonate and siliciclastic rocks, where relevant karst systems develop, marked by the occurrence of sinking streams, sinkholes, and caves with a great diversity of morphologies, speleothems, subterranean fauna, and paleontological and archaeological records. Relevant carbonate systems occur in Iraquara, such as the Lapa Doce, Torrinha, and Pratinha caves, which represent important tourist attractions. Also in these rocks, stand out the Brejões Cave, with a 106-m high entrance, and the Toca da Boa Vista, the largest cave in South America, extending across 114 km. Cultural manifestations are present in the prehistoric cave paintings at Santa Marta Shelter and recent religious pilgrimages at Mangabeiras Cave, in Ituaçu. In turn, siliciclastic karst systems are mainly in Serra do Sincorá. The Lapão and Castelo caves have expressive speleogens and speleothems, as well as the Torras Cave, in the Igatu region, ranked as the second largest in Brazil considering siliciclastic rocks.

Nanocomposite synergy for enhanced oil recovery: Macro and micro analysis of CeO2/montmorillonite nanofluids in carbonate and sandstone reservoirs

Cerium (IV) oxide has shown great potential for serving as a mutually advantageous conjunction material when applied in a synergistic manner of use with other chemicals thanks to its oxygen storage capacity. Recently, many researchers have elaborated on novel synthesis methods for achieving nanocomposites (NCs) that combine inherent properties of nano-sized CeO2 with those of montmorillonite, as a low-cost base substance. CeO2/Montmorillonite nanocomposite synthesized by application of an environmentally friendly reducing and stabilizing agent. The success of the synthesis was verified by analytical techniques including Field-Emission Scanning Electron Microscopy, Thermo-Gravimetric analysis, Energy-Dispersive X-ray Spectroscopy and Mapping, X-Ray Diffraction analysis, Fourier-Transform Infrared spectroscopy. Nanofluids were prepared by dispersing the synthesized NCs, at different concentrations as aqueous colloidal solutions and then studied for investigating the nanofluid colloidal stability. Experimental studies were undertaken on the nanofluid functioning subjects of the fluid/fluid and fluid/fluid/rock interactions area in both macro and micro scales. Macro investigations of interfacial tension and wettability alteration and also micro-analysis of microfluidic injections with proper visualizations of created effects within pore structures were carried out. The results confirmed the proper synthesis of the NC and its stability in water-based nanofluids. CeO2 nano clays showed nearly 33 % optimization of the interfacial tension (IFT) (i.e., IFT decreased from the initial value of 27 to 18 mN/m at the NC concentration of 1000 ppm). However, their effect on the alteration of wettability was significant. Indeed, at the optimum concentrations, the contact angle decreased from 151° to 19.38° at the concentration of 500 ppm for carbonate lithology (87.1 % optimization) and also it decreased from 135.5° to 18.73° at the concentration of 1500 ppm for sandstone lithology (86.1 % optimization). The effect of wettability alteration for carbonate rocks was reported to be high enough for changing the wettability to a strong water-wet state while the wettability alteration for sandstone lithology was measured to be low. Both wettability alteration studies and micro visualizations validated the strong and low wettability alteration for carbonate and sandstone lithology systems. Also, the emulsion analysis was carried out on the micro-scaled images of the pores and throats with their containing fluids by a new method of color saturation investigation which showed a promising new emulsion analysis method for micro-scaled experiments.

Reagentless reduction of hydrogen carbonate-calcium hardness of water: equilibrium states and kinetics

The equilibrium states and kinetics of changes in the concentrations of carbonate system components in water with different calcium hardness are analyzed and the possibility of reducing this indicator by an environmentally friendly method, aeration, is evaluated. Changes in the concentrations of dissolved carbon dioxide, calcium ions, hydrogen ions (pH), bicarbonate and carbonate ions in water depending on the partial pressure of carbon dioxide in soil and atmospheric air and the kinetics of reducing the bicarbonate-calcium hardness of water during its natural and forced aeration were traced. It is shown that water purification by a stream of atmospheric air microbubbles with an average radius of 50 m and a flow rate of 10 l/min can reduce the hydrogen carbonate-calcium hardness from 8 mg-eq/l to 1 mg-eq/l in 100 liters of water in 20 minutes. In the paradigm of "green chemistry", this method is more rational, environmentally friendly, and economical than ion exchange or reverse osmosis, which are currently practiced to reduce hardness in decentralized water supply systems.

Temporal variations in the surface aragonite saturation state of the Yellow Sea: Observations at the Socheongcho Ocean Research Station during 2017–2022

Accurately constraining the natural variability of the carbonate system is essential for evaluating long-term changes in coastal areas, which result from the absorption of anthropogenic CO2. This is particularly important given the significant variation in physical and biological processes in these regions. In this regard, the analysis of surface carbonate chemistry in the Yellow Sea was conducted using discrete seawater samples obtained from the Socheongcho Ocean Research Station (37.423°N, 124.738°E) between 2017 and 2022. Our bottle data and sensor pH measurements revealed considerable seasonal variations of aragonite saturation state (ΩAR), typically ranging from 1.6 to 3.9. These variations are particularly pronounced during the summer and early winter. Our dataset serves as a baseline for understanding the long-term changes in ocean acidification in the Yellow Sea, the complex biogeochemical processes in coastal areas, and their impact on ocean acidification.

Field assessment of coconut-based activated carbon systems for the treatment of herbicide contamination

Once released into the environment, herbicides can move through soil or surface water to streams and groundwater. Filters containing adsorbent media placed in fields may be an effective solution to herbicide loss in the environment. However, to date, no study has investigated the use of adsorbent materials in intervention systems at field-scale, nor has any study investigated their optimal configuration. Therefore, the aim of this paper was to examine the efficacy of low-cost, coconut-based activated carbon (CAC) intervention systems, placed in streams and tributaries, for herbicide removal. Two configurations of interventions were investigated in two agricultural catchments and one urban area in Ireland: (1) filter bags and (2) filter bags fitted into polyethylene pipes. Herbicide sampling was conducted using Chemcatcher® passive sampling devices in order to identify trends in herbicide exceedances at the sites, and to quantifiably assess, compare, and contrast the efficiency of the two intervention configurations. While the Chemcatcher® passive sampling devices are capable of analysing eighteen different acid herbicides, only six different acid herbicides (2,4-D, clopyralid, fluroxypyr, MCPA, mecoprop and triclopyr) were ever detected within the three catchment areas, which were also the only acid herbicides used therein. The CAC was capable of complete herbicide removal, when the water flow was slow (0.5–1 m3 s−1), and the interventions spanned the width and depth of the waterway. Overall, the reduction in herbicide concentrations was better for the filter pipes than for the filter bags, with a 48% reduction in detections and a 37% reduction in exceedances across all the sampling sites for the filter pipe interventions compared to a 13% reduction in the number of detections and a 24% reduction in exceedances across all sampling sites for the filter bag interventions (p < 0.05). This study demonstrates, for the first time, that CAC may be an effective in situ remediation strategy to manage herbicide exceedances close to the source, thereby reducing the impact on environmental and public health.

Soft‐sediment deformation structures and Neptunian dykes across a carbonate system: Evidence for an earthquake‐related origin (Norian, Dolomia Principale, Southern Alps, Italy)

AbstractIdentification of the processes producing soft‐sediment deformation structures, common in siliciclastic deposits and less abundant in carbonate successions, is complex, because different processes may produce similar structures. Thus, interpreting the origin of these structures may be challenging: it requires both a detailed sedimentological study, and the knowledge of the depositional environment and stratigraphic evolution, in order to provide hints to identify the processes affecting sediments after deposition. Among the potential causes of the formation of soft‐sediment deformation structures, seismic shock is one of the possibilities, but their origin could be also related to other triggering mechanisms, such as volcanic activity, sediment loading, salt tectonics, fluid expulsion, meteorite impacts and mass movements. Although it is a plausible option, the interpretation of these structures as ‘seismites' is not obvious: it must be supported by different lines of evidence, considering that the correct interpretation of soft‐sediment deformation structures as a consequence of seismic shocks acquires important implications in palaeoseismology studies. The occurrence of diverse soft‐sediment deformation structures in a fault‐controlled basin (i.e. in a geological setting characterized by syndepositional tectonics) preserved in different subenvironments of a Norian carbonate system in the Southern Alps of Italy provides the chance to characterize different types of soft‐sediment deformation structures along a platform‐to‐basin depositional profile. Presence of pseudonodules in basinal resedimented limestone, sedimentary dykes and clinostratified breccias with unlithified clasts in slope settings and liquefaction of inner platform facies at the platform top testify to an origin compatible with multiple seismic shocks, repetitively affecting the same stratigraphic intervals. The diverse types of soft‐sediment deformation structures in the studied carbonate system provide a rich catalogue of structures related to seismic shocks, representing a possible reference for other similar settings.

Amplified Subsurface Signals of Ocean Acidification

AbstractWe evaluate the impact of anthropogenic carbon (Cant) accumulation on multiple ocean acidification (OA) metrics throughout the water column and across the major ocean basins using the GLODAPv2.2016b mapped product. OA is largely considered a surface‐intensified process caused by the air‐to‐sea transfer of Cant; however, we find that the partial pressure of carbon dioxide gas (pCO2), Revelle sensitivity Factor (RF), and hydrogen ion concentration ([H+]) exhibit their largest responses to Cant well below the surface (&gt;100 m). This is because subsurface seawater is usually less well‐buffered than surface seawater due to the accumulation of natural carbon from organic matter remineralization. pH and aragonite saturation state (ΩAr) do not exhibit spatially coherent amplified subsurface responses to Cant accumulation in the GLODAPv2.2016b mapped product, though nonlinear characteristics of the carbonate system work to amplify subsurface changes in each OA metric evaluated except ΩAr. Regional variability in the vertical gradients of natural and anthropogenic carbon create regional hot spots of subsurface intensified OA metric changes, with implications for vertical shifts in biologically relevant chemical thresholds. Cant accumulation has resulted in subsurface pCO2, RF, and [H+] changes that significantly exceed their respective surface change magnitudes, sometimes by &gt;100%, throughout large expanses of the ocean. Such interior ocean pCO2 changes are outpacing the atmospheric pCO2 change that drives OA itself. Re‐emergence of these waters at the sea surface could lead to elevated CO2 evasion rates and reduced ocean carbon storage efficiency in high‐latitude regions where waters do not have time to fully equilibrate with the atmosphere before subduction.

An assessment of HgII to preserve carbonate system parameters in organic‐rich estuarine waters

AbstractThis work assesses the effectiveness of sample preservation techniques for measurements of pHT (total scale), total dissolved inorganic carbon (CT), and total alkalinity (AT) in organic‐rich estuarine waters as well as the internal consistency of measurements and calculations (e.g., AT, pHT, and CT) in these waters. Using mercuric chloride (HgCl2)‐treated and untreated water samples, measurements of these carbonate system parameters were examined over a period of 3 months. Respiration of dissolved organic matter in untreated samples created large discrepancies in CT concentrations (~37 μmol kg−1 increase, p &lt; 0.0001), while CT was effectively constant in treated samples (3095.0 ± 1.14 μmol kg−1). AT changes were observed for both treated and untreated samples, with HgCl2‐treated samples showing the greatest variation (~ 26 μmol kg−1 decrease, p &lt; 0.001). In response to changing AT/CT ratios, pHT changes occurred in both treated and untreated samples but were relatively small in treated samples. Results in organic‐rich estuarine waters that reflect the in situ carbonate system characteristics of the samples at the time of collection can be improved when samples obtained for CT and AT analysis are collected and stored separately. Accurate analyses of CT can be obtained by filtration and preservation with HgCl2. Accuracy of AT analyses can be improved by filtration and storage without adding HgCl2. The quality of pHT measurements can be improved by prompt analysis in the field and, if this cannot be accomplished, then samples can be preserved with HgCl2 and measured in the laboratory within 1 week.

Investigating the controls on architecture and facies distribution of a carbonate ramp to shelf system: Insights from stratigraphic forward modeling of the Jurassic Smackover Formation, Gulf of Mexico

To develop a better understanding of the controls on the stratigraphic architecture of carbonate systems, it is necessary to quantify the impact of the physical and chemical variables responsible. The growth, distribution, and nature of carbonate factories are dependent on various space and time-dependent variables, such as paleotopography, accommodation, sediment supply, energy and slope of the system, and water chemistry.The Upper Jurassic Smackover Formation is a heterogeneous hydrocarbon source rock and reservoir in the semi-restricted Conecuh Embayment of southwestern Alabama. It consists of a lower transgressive unit composed of microbialite and mudstone/wackestone, and an upper regressive mixed carbonate-siliciclastic unit composed of oolitic packstone-grainstone, microbialite, bioturbated to laminated carbonate mudstone, and shale. The physiographic setting of the Conecuh Embayment, along with the variability in the carbonate factory types, eustatic sea level fluctuations, and sea-water circulation presents an exceptional site for evaluating the controls on carbonate platform/shelf margin to slope architecture.Stratigraphic forward modeling using DionisosFlow, calibrated with a geologic cross-section built from well log and core data, was carried out to test the impact of antecedent topography, accommodation, and carbonate factory type on the facies distribution and architecture of the carbonate shelf. Results of our study indicate that geometries in the transgressive Smackover shelf are controlled by accommodation and rate of carbonate production, while limited accommodation controlled the stratigraphic architecture of the regressive system.

Ikaite formation in streams affected by steel waste leachate: First report and potential impact on contaminant dynamics

Highly alkaline (pH 9–12) waters can arise from a range of globally significant and environmentally impactful industrial processes such as lime, steel and cement production, alumina refining and energy generation (e.g. combustion ashes). Such residue storage sites are often characterized by extreme geochemical conditions that can be hazardous to aquatic life but are quickly becoming a critical focus for resource recovery and carbon capture initiatives. The very high rates of mineral precipitation at these sites can give rise to the formation of transient minerals that are not currently well understood. As such our estimates of carbon budgets and understanding of trace metal dynamics at highly alkaline sites is currently limited. This study provides a significant advancement in the basis for characterising hyperalkaline carbonate systems through identification and chemical analysis of transient minerals forming in sites receiving high pH (>11) steel slag leachate in northern England. Whilst most of the secondary deposits at the study sites appear to be dominated by calcite, this study provides the first account of ikaite (CaCO3.6H2O) crystallization within steel-slag leachate, using novel field (Fourier Transform Infra-Red) supported by rapid laboratory (X-Ray Diffraction) validation. This study suggests that ikaite is a secondary mineral with a primary phase being amorphous calcium carbonate (ACC). Trace element analysis of ikaite forming in these steel-slag leachate affected waters is demonstrates its strong affinity to incorporate relatively large inventories of potentially harmful metals (e.g. lead and cadmium). Importantly, ikaite is only stable at low temperatures (−4 to 8 °C) and thus is of significant concern given its potential to release hazardous pulses of contamination during warming events in the spring. The findings provide an improved understanding of carbonate precipitation processes at highly alkaline sites which in turn should influence future research endeavours around mineral carbonation, trace metal dynamics and environmental remediation at these sites globally.

Dual-Stackelberg game-based trading in community integrated energy system considering uncertain demand response and carbon trading

Given the uncertainties in integrated demand response and carbon trading mechanism, this paper utilizes a dual-Stackelberg game framework to propose trading strategies among multiple entities within such a system. The innovation of this study lies in its development of a collaborative optimization method that encompasses extensive competition between the supply and demand sides, considering the synergistic incentives of carbon trading on the source-side and uncertain responses on the load-side. Firstly, a typical system framework is constructed involving various participants, clarifying energy and carbon market mechanisms and incorporating users’ psychological characteristics in demand response uncertainty. Secondly, a dual-Stackelberg game model is established, and the existence and uniqueness of game equilibrium are demonstrated. Finally, the model's effectiveness is validated through various scenarios. The results indicate that the equilibrium benefits of each entity are 6643.81, 7747.16, 8029.01 yuan, and 9326.62 yuan. The carbon trading mechanism can effectively constrain and reduce the system's carbon emissions by 10.20 %. Furthermore, accounting for user uncertainties in integrated demand response behavior leads to an 18.54 % increase in the peak-to-valley difference in electricity demand. It is concluded that the presented methodology provides innovative insights for addressing trading challenges within hierarchical integrated energy markets.

Barnacle-rich facies as a tool for palaeoenvironmental reconstructions

Palaeoenvironmental data are fundamental in determining the manifold impacts of climate change. This paper argues that sessile barnacles are an excellent palaeoenvironmental proxy: they are present in nearly all nearshore environments, and their shell consists of diagenetically stable low-magnesium calcite and grows fast enough to record short-term variations. To demonstrate their utility, specimens from several Western Mediterranean Pliocene and Pleistocene barnacle-rich deposits are analysed herein, using for the first time a combination of sedimentology, taphonomy, stable isotope geochemistry and detailed comparisons with modern counterparts. Within shelf carbonate systems, barnacle diversity is highest in the shallow, nearshore waters and decreases moving offshore, thus providing a good proxy for the reconstruction of water depth and distance from the coastline. Barnacle taphonomy is also informative. Well-preserved complete specimens are characteristic of protected areas, whereas less well-preserved specimens occur in high-energy areas. The presence/absence of opercular plates is also particularly relevant for evaluating hydrodynamic conditions. As regards the C and O stable isotope ratios, due to the porous and coarse-grained nature of the deposits in which barnacle remains are usually found, the shells are often exposed to meteoric water percolation during diagenesis. Among the analysed specimens, only those collected from fine-grained deposits display no evidence of alteration and have isotopic ratios in line with those of their modern counterparts. These fossils display intra-shell variations that in modern barnacles have been related to short-term environmental changes (e.g., seasonal cycles). These results demonstrate that barnacles can always be useful for detailed palaeoenvironmental reconstructions based on skeletal assemblages. Furthermore, with further research aimed at gathering more data and assessing potentially interfering signals, they could become useful proxies for palaeoseasonality.

Mini-Kilns for Charcoal-Making: An Eco-Friendly Solution for Small-Scale Production of Charcoal and Wood Vinegar

Charcoal is one of the most essential energy sources in the world and is used mainly for domestic and industrial purposes. Brazilian charcoal production occurs in rudimentary masonry kilns without concern for process safety or energy waste. This work aimed to develop a mini carbonization system of three kilns coupled to a vertical smoke burner for optimized and environmentally correct charcoal and wood vinegar (WV) production on small farms. The project was divided into three parts for dimensioning: the three-kiln set, the WV condensing device, and the smoke burner. The condenser was designed following the procedures from the standards of TEMA (Tubular Exchangers Manufacturers Association); ASME (Society of Mechanical Engineers of the United States) Section VIII, Division 1; and the NR-13 (Regulatory Standard) of ABNT (Brazilian Association of Technical Standards). In contrast to the current scenario, in which primitive carbonization technologies are still employed, bringing about low charcoal yields and significant pollution release, the use of a mini-kiln that allows charcoal production and wood vinegar recovery combined with pollutant smoke burning is an interesting eco-friendly solution. Thus, the mini-kiln model presented here brings a low cost and environmental safety to the charcoal production chain, reaching sustainability parameters and offering higher income opportunities to small producers.