Composition Of Seawater Research Articles

Seafloor hydrothermal systems control long-term changes in seawater [Li+]: Evidence from fluid inclusions.

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 H2O at 150 Ma ago to 27 μmol/kg H2O 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 Mg2+/Ca2+ and 87Sr/86Sr, and the change from calcite to aragonite seas, KCl to MgSO4 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.

Pengembangan Alat Desalinasi Air Laut dengan Teknologi Thermal Energy Storage

The need for clean water in household life is very important because humans cannot live without it. The composition of seawater consists of 96.5% pure water and 3.5% other materials, namely salts, dissolved gases, and others. Indonesia is one of the countries that has the second-longest coastline in the world, so the potential for utilizing sea water is very large, one of which can be through the desalination process. Distillation itself is distillation, and its by-product is salt when seawater is heated using a heat energy source with a concentrated solar power (CSP) system. Based on research that has been done previously, the tool is a lab-scale seawater desalination device, but the process of making a lab-scale seawater desalination tool is not optimal. Then design the construction of a lab-scale seawater desalination device with the Multi Stage Flash (MSF) type, and the aim is to determine the performance and functionality of the MSF-type lab-scale seawater desalination device. The results show that the results of the coil heat exchanger development obtained an inlet temperature of 85.9°C and an outlet temperature of 67.8°C, and the room temperature in the chamber can be maintained at a temperature of 68.9°C. As for the components being developed, such as sea water pumps, hoses, tees, and sprayers, a sea water debit of 53.78 liters per hour has been obtained.

The Perturbation of the Guadalupian Marine Environment Triggered by Early-Stage Eruption of the Emeishan Large Igneous Province: Rare Earth Element and Sr-Nd Isotope Evidence from Zunyi Manganese Deposit, South China

Pure marine chemical sediments are archives of geochemical proxies for the composition of seawater and may provide information about the ancient hydrosphere–atmosphere system. The early stage of the Emeishan large igneous province (ELIP) was characterized by the subaqueous eruption of mafic igneous rocks around the J. altudaensis zone of the Capitanian Stage that has been proposed to have contributed to the Guadalupian mass extinction. However, detailed mechanisms and the impact of the eruption on the Guadalupian marine environment have yet to be assessed. Here, to examine the Guadalupian marine environment, we studied major and trace element concentrations, particularly rare earth element and yttrium data, along with high-precision Sr-Nd isotope ratios, of three types of Mn ores (i.e., clastic, massive, and oolitic) and siliceous limestones from the Zunyi Mn deposit in South China formed following the early-stage eruption of the ELIP. Our results indicate that the clastic Mn ores contain notable detrital mafic aluminosilicates. In contrast, the massive and oolitic Mn ores and siliceous limestones preserved the pristine geochemical signatures of the Middle–Late Permian seawater characterized by distinctly low (87Sr/86Sr)i and high εNd(t) values. These data indicate a strong impact of the early-stage submarine eruptions of the ELIP on the marine environment in South China and worldwide, likely through intensive seawater–rock interaction.

Injectivity assessment for CCS field-scale projects with considerations of salt deposition, mineral dissolution, fines migration, hydrate formation, and non-Darcy flow

This paper aims to review the main mechanisms identified in the lab scale that impact CO2 injectivity during CCS projects in saline aquifers and evaluate their relevance in field scale through numerical models. They may include water vaporization, salt precipitation in the dry-out zone, mineral dissolution, which can result in fines migration in porous media, CO2 hydrate formation, and effects of non-Darcy flow. All those mechanisms are observed from lab experiments and significantly impact reservoir petrophysical properties such as porosity and permeability and consequently on injectivity in field operations. This study includes these mechanisms in numerical models to quantify their impacts on the CO2 injectivity well index in synthetic and real field cases. In addition, a sensitivity analysis was performed for a range of brine compositions of seawater and higher salinities. This analysis shows an additional injectivity reduction as the salinity increases due to the halite scale, in agreement with the lab data from the literature. Another dependence evaluated in this study is when the ratio between capillary and viscous forces is decreased, reducing the injectivity. Additionally, when mineral reaction dissolution is considered in our modeling, it is possible to observe two occurring competitive phenomena, where the mineral dissolution can compensate for part of the injectivity loss due to salt deposition in the dry-out zone. That is especially relevant when the reservoir rock matrix is rich in reactive minerals, such as calcite and dolomite. However, mineral dissolution may lead to fines, and the risk of fines migration can lower the injectivity by at least 10% within five years of CO2 injection, according to our results. The mineral dissolution is also considered in these calculations, and the loss in injectivity is the net result of dissolution and fines migration. The gain in porosity–permeability as the results of mineral dissolution was modeled using the Kozeny-Carman equation. The results show the importance of considering the uncertainty of injectivity loss in CCS projects, where the amount of CO2 captured for storage must be injected often with no other alternatives, highlighting the need to provide flexibility in project planning to deal with such risks.

Reconstruction of the conditions for the formation of red-colored sandstones of the Tersky coast based on a comparative analysis of the structure of ancient and modern deposits (Kola Peninsula)

The paper presents the results of studying the Riphean red-colored sandstones of the Tersky coast of the White Sea. 21 structural elements characterizing the conditions of rock formation have been considered, including 15 ancient and 6 modern deposits. Observations were carried out for 10 years in two areas of the White Sea coast. The purpose of the research is to establish the reasons for the absence of organic matter, the origin of the hematite admixture in the Riphean sandstones, and to assess the climatic conditions during their formation. These issues are key to identifying the Proterozoic red formation. The data have shown that some rock structures are similar in ancient and modern deposits. Such structures include, for example, wave ripples repeating in detail the dimension, shape, and orientation in both epochs, and therefore can be used to assess ancient marine sedimentation conditions. However, most of the structures testify to fundamental differences in the conditions of rock formation. It has been established that takyrs were systematically formed in ancient rocks and hematite was deposited, which indicates the arid climate in the Riphean and the specific composition of sea water. The most important difference between ancient deposits is the absence of fauna and flora in them.

Seawater ageing of thermoplastic acrylic hybrid matrix composites for marine applications

Increasing usage of polymer composite materials necessitates the development of recyclable alternatives to traditional thermoset matrices or new techniques for recycling these materials. One family of promising recyclable matrices are the room temperature infusible acrylic resins, known commercially as Elium®. If these new materials are to be used in the tidal stream energy and shipping sectors, they must be able to withstand long-term immersion in seawater without significant losses in mechanical properties. In this study, accelerated seawater ageing is applied to acrylic/glass fibre and modified acrylic/glass fibre composites along with a traditional epoxy/glass fibre baseline. The mechanical properties (tensile, flexural, and short beam) are compared before and after ageing, and electron microscopy is used to examine fracture surfaces to determine the effects of water ingress on fracture propagation. In addition, the diffusion coefficients of the composites in seawater are compared and the changes in glass transition temperatures are used to determine the effects of plasticisation.

Barium isotope (re-)equilibration in the barite-fluid system and its implications for marine barite archives

Variations in the Ba isotopic composition of seawater are largely driven by the extent of barite precipitation in the marine photic zone and replenishment of Ba by upwelling and/or continental inputs. Pelagic barites offer a robust tool for tracing sources and sinks of Ba in the (paleo)ocean as they record these isotopic variations. Knowledge of the Ba isotope fractionation between barite and ambient waters is therefore imperative. Here, the Ba isotope fractionation between barite and Ba2+ (aq) under equilibrium conditions has been estimated by the three-isotope method with a 135Ba-enriched reactive fluid. The estimated Ba isotope fractionation was Δ137/134BaBarite-Ba2+ = −0.07 ± 0.08‰. Textural observations of barite crystals recovered up to 756 days of reaction reveal smoothing of solid surfaces but also typical dissolution features such as development of pits and cracks. Thus, dissolution/re-precipitation is likely the mechanism controlling the observed isotope exchange that is facilitated by the further development of porosity in the crystals. Additionally, the isotope exchange in the experimental runs fits a second-order law yielding a surface normalized isotope exchange rate of ∼2.8 × 10−10 mol/m2/s. This exchange rate could theoretically result in complete isotope exchange between pelagic barite with a typical edge size of 1 μm and ambient seawater or pore fluid within years, altering the barite's Ba isotopic composition during settling towards the seafloor and/or after deposition in marine sediments. Although there is considerable uncertainty in extrapolating experimental results to natural conditions and longer time scales, the rapid rates of exchange observed experimentally over short timescales suggest that isotope exchange in pelagic barite should be considered during interpretation of the Ba isotope composition as a paleoarchive.

Formation of molar tooth structures in low sulfate Precambrian oceans

Molar tooth structures (MTS) comprise calcite microspar-filled voids in fine-grained shallow-water carbonate, and were commonly formed in the Mesoproterozoic and early Neoproterozoic. However, the origin of MTS and links between the temporal distribution of MTS and contemporaneous seawater chemistry remains poorly understood. Here we report elemental and isotopic data for MTS and host rocks from the Mesoproterozoic Gaoyuzhuang Formation (∼1,600–1,550 Ma), North China Craton. The results reveal similar C, S and Sr isotope signatures between MTS and host rocks, which are close to the isotopic compositions of contemporaneous global seawater, suggesting an early diagenetic, seawater-buffered origin for MTS. A small sulfur isotopic fractionation between seawater sulfate and pyrite (Δ34SCAS-Py) of 4.1 ± 1.5‰ in host rocks is consistent with previously reported data, providing support for sub-millimolar sulfate concentrations in Mesoproterozoic seawater. Our observations suggest that the widespread occurrence of MTS through the Mesoproterozoic to early Neoproterozoic was broadly linked to sulfate scarcity in the ocean. We further propose that in Proterozoic oceans with sub-millimolar seawater sulfate concentrations, where aerobic and anaerobic methane oxidation was likely inhibited, methane produced via methanogenesis may have been more prone to accumulate in sediments, creating voids during escape. The absence of MTS across periods of higher sulfate concentrations during the Palaeoproterozoic and after the mid-Neoproterozoic, suggests that elevated sulfate concentrations promoted consumption of methane via anaerobic methane oxidation, thus preventing methane accumulation and the formation of sediment voids. Rapid lithification of the substrate as a result of elevated carbonate saturation may have also hindered the formation of MTS during these intervals. The link between MTS and changes in both oceanic sulfate levels and benthic methane fluxes gives a new perspective on temporal fluctuations in Earth’s redox state through time.

Graphene Nanopores Enhance Water Evaporation from Salt Solutions: Exploring the Effects of Ions and Concentration.

With increased water stress, the development of clean water technologies is an active area of research. Evaporation-based solutions offer the advantage of low energy consumption, and recently a 10-30 fold enhancement in water evaporation flux has been observed through Å-scale graphene nanopores (Lee, W.-C., et al., ACS Nano 2022, 16(9), 15382). Herein, using molecular dynamics simulations, we examine the suitability of Å-scale graphene nanopores in enhancing water evaporation from salt solutions (LiCl, NaCl, and KCl). Cation-π interactions between ions and the surface of nanoporous graphene are found to significantly influence ion populations in the nanopore vicinity, leading to varied water evaporation fluxes from different salt solutions. The highest water evaporation flux was observed for KCl solutions, followed by NaCl and LiCl solutions, with the differences reducing at lower concentrations. Relative to the bare liquid-vapor interface, 4.54 Å nanopores exhibit the highest evaporation flux enhancements ranging from 7 to 11, with an enhancement of 10.8 obtained for 0.6 M NaCl solution, which closely resembles seawater compositions. Functionalized nanopores induce short-lived water-water hydrogen bonds and reduce surface tension at the liquid-vapor interface, thereby lowering the free energy barrier for water evaporation with a negligible effect on the ion hydration dynamics. These findings can aid in developing green technologies for desalination and separation processes with low thermal energy input.

Interstitial carbonates in pillowed metabasaltic rocks from the Pilbara Craton, Western Australia: A vestige of Archean seawater chemistry and seawater-rock interactions

Calcites hosted in the interpillow void spaces of extremely well preserved, 3.47–3.12 Ga pillow lavas of the Archean Pilbara Craton, Australia, provide new geochemical insights into the composition of Archean seawater and its interaction with basaltic crust. We present a comprehensive dataset of major and trace elements, radiogenic 147Sm-143Nd, 87Rb-87Sr, and stable C-O isotopes for these calcites.Based on their elemental composition and Post-Archean Australian Shale-normalized rare earth element and yttrium (REYPAAS) patterns, two types of calcites can be distinguished. Type I (n = 9) are coarse-grained calcites with elevated Mn concentrations (478–14,790 ppm) and high REY concentrations that match the basaltic host rock compositions. Petrographic textures in combination with geochemical data indicate precipitation from boiling seawater trapped between pillows during basalt eruption. Small light-REYPAAS depletions, only slightly super-chondritic Y/Ho (34.5–39.1), and low δ18O(VSMOW2) (9.25–16.66 ‰) suggest relatively high fluid-rock interactions of boiling seawater with the basaltic host rock. These characteristics are similar to those of interstitial carbonates found in modern mid-ocean ridge basalts. Type II carbonates (n = 6) are fine-grained, low-Mn (13.7–420 ppm) calcites that exhibit comparably high Sr concentrations (825–2,516 ppm) and anoxic modern seawater-like REYPAAS patterns, strong super-chondritic Y/Ho (39.1–55.8) and δ18O(VSMOW2) values of 9.10–13.18 ‰. These features hint to direct calcite precipitation from seawater within the degassing space with little fluid-rock interaction.Almost all (Type I and Type II) of the calcites investigated here, combined with their respective host rocks, yield well-defined Sm-Nd isochron ages for the Apex (3,466 ± 23 Ma), Euro (3,365 ± 43 Ma), Honeyeater (3,187 ± 33 Ma), and Bradley (3,131 ± 24 Ma) formations. Only calcites from the Mt. Ada Basalt and their associated host rocks show a ∼ 100 Ma younger Sm-Nd isochron age (3,361 ± 22 Ma) compared to the U-Pb zircon age of formation.Highly radiogenic initial Sr isotope compositions of the high-Mn calcites (Type I) and low Sr concentrations, suggest Sr remobilization for these calcites. In contrast, the low-Mn calcite (Type II) exhibit higher Sr concentrations and lower 87Sr/86Sr(i) of 0.7010–0.7011 at 3.34 Ga and 0.70137 at 3.12 Ga, suggesting increasing influence of crustal weathering on the composition of Paleoarchean seawater through time, and progressive decoupling from the Archean mantle (87Sr/86Sr(i) = 0.7003–0.7007).

Investigating Seawater Intrusion in Republic of South Africa’s Heuningnes, Cape Agulhas Using Hydrogeochemistry and Seawater Fraction Techniques

The Heuningnes Catchment in the Republic of South Africa was used as a case study in this research to describe the application of saltwater fraction/quantification and hydrogeochemistry methods to evaluate the extent of saline intrusion in the coastal aquifers. The argument of the research is that the presence of seawater incursion may be conclusively determined by combining the examination of the major ions, seawater fraction, stable isotopes of water, bromide, and geochemical modeling. Using stable isotopes of oxygen (18O) and deuterium (2H), major ions chemistry, seawater composition, and geochemical modeling, the genesis of salinity and mixing of different water masses were examined. Twenty-nine (29) samples of groundwater were examined. All samples showed water facies of the Na-Cl type, indicating a seawater-related origin. The significance of mixing in coastal aquifers under natural conditions was shown by the hydrogeochemical characteristics of key ions derived from ionic ratios, which demonstrated substantial adherence to mixing lines among endmembers for freshwater as well as saltwater (seawater). The quantification of seawater contribution in groundwater percentages varied from 0.01 to 43%, with three samples having concentrations of seawater above 50%. It was clear from the hydrogeochemical analysis and determination of the proportion of saltwater that the seawater intrusion impacted the coastal fresh groundwater. In addition, the chloride concentration in the groundwater ranged from 81.5 to 26,557.5 mg/L, with the corresponding δ18O values ranging from −5.5‰ to −0.9‰, which suggested that freshwater and saltwater were mixing. The Br−/Cl− ratios showed that evaporation had played a part in elevating groundwater salinity as well. Since saturation indices were below zero, the mineral dissolution could also contribute to the salinization of groundwater. Further proof of seawater incursion in the investigated catchment was supplied by geochemical modeling and bromide. Even though such tools were not verified in multiple coastal aquifers for widespread generalization, the study offered a scientifically significant understanding of the application of such tools on seawater intrusion in coastal aquifers and has useful recommendations for the aquifer setting of similar environments.

Zinc, carbon, and oxygen isotopic variations associated with the Marinoan deglaciation

The "Snowball Earths" were cataclysmic events during the late Neoproterozoic's Cryogenian period (720-635 Ma) in which most, if not all, of Earth’s surface was covered in ice. Paleoenvironmental reconstructions of these events utilize isotopic systems, such as Δ17O and barium isotopes of barites. Other isotopic systems, such as zinc (Zn), can reflect seawater composition or environmental conditions (e.g., temperature changes) and biological productivity. We report here a multi-isotopic C, O, and Zn data set for carbonates deposited immediately after the Marinoan glaciation (635 Ma) from the Otavi Group in northern Namibia. In this study, we chemically separated calcite and non-calcitic carbonate phases, finding isotopically distinct carbon and oxygen isotopes. These could reflect changes in the source seawater composition and conditions during carbonate formation. Our key finding is largescale Zn isotopic variations over the oldest parts of the distal foreslope cap carbonate sections. The magnitude of variation is larger than any found throughout post-snowball cap carbonates to date, and in a far shorter sequence. This shows a heretofore undiscovered difficulty for Zn isotopic interpretations. The primary Zn sources are likely to be aeolian or alluvial, associated with the massive deglaciation related run-off from the thawing continent and a greater exposed surface for atmospheric aerosol entrainment. The samples with the lightest Zn isotopic compositions (δ66Zn < 0.3 ‰) potentially reflect hydrothermally sourced Zn dominating the carbonates’ Zn budget. This finding is likely unique to the oldest carbonates, when the meltwater lid was thinnest and surface waters most prone to upwelling of hydrothermally dominated Snowball Earth brine. On the other hand, local variations could be related to bioproductivity affecting the Zn isotopic composition of the seawater. Similarly, fluctuations in sea-level could bring the depositional site below and above a redoxcline, causing isotopic variations. These variations in Zn isotope ratios preclude the estimation of a global Zn isotopic signature, potentially indicating localized resumption of export production.

Stable tungsten isotopic composition of seawater over the past 80 million years

Abstract The isotopic composition of seawater provides valuable information on how the Earth system has evolved. Here we present the stable tungsten isotopic composition (δ186/184W) of seawater recorded in three ferromanganese (Fe-Mn) crusts spanning the past 80 million years in the Pacific. The δ186/184W of Fe-Mn crusts displays a pronounced decrease of ∼0.2‰ from 60 Ma to 40 Ma followed by a stable value of ∼0‰ since ca. 40 Ma. Multiple lines of evidence indicate an invariable equilibrium isotopic fractionation between Fe-Mn crusts and seawater. The consistent variations in δ186/184W in the three Fe-Mn crusts also indicate limited alteration by deposition regime or diagenetic overprinting. Thus, the δ186/184W of Fe-Mn crusts reflects mainly that of seawater. A simple mass-balance calculation and comparison to other proxies suggest that the early Cenozoic decrease of seawater δ186/184W was most likely caused by decreased W isotopic fractionation between seawater and W sinks linked to shifting sedimentation regimes. We propose that increased burial of organics and decreased Fe-Mn oxide (FMO) sedimentation may result in a smaller isotopic fractionation associated with W sinks by limiting the adsorption of W from the water column onto FMOs in openocean sediments. Our results demonstrate the potential of δ186/184W as a novel paleo-proxy for global biogeochemical cycling.

Biogeochemical cycling of chromium and chromium isotopes in the sub-tropical North Atlantic Ocean

Chromium (Cr) is a redox-sensitive element and because Cr isotopes are fractionated by redox and/or biological processes, the Cr isotopic composition of ancient marine sediments may be used to infer changes in past seawater oxygenation or biological productivity. While there appears to be a ‘global correlation’ between the dissolved Cr concentration and Cr isotopic composition of seawater, there is ongoing debate about the relative importance of external sources and internal cycling on shaping the distribution of dissolved Cr that needs to be resolved to validate the efficacy of using Cr isotopes as a paleo proxy. Here, we present full water column depth profiles of total dissolved Cr (Cr(VI)+Cr(III)) and dissolved Cr isotopes (δ53Cr), together with ancillary data, for three stations along a transect (GEOTRACES GApr08) across the sub-tropical North Atlantic. Concentrations of dissolved Cr ranged between 1.84 and 2.63 nmol kg-1, and δ53Cr values varied from 1.06 to 1.42‰. Although atmospheric dust, hydrothermal vents and seabed sediments have the potential to modify the distribution of Cr in the oceans, based on our observations, there is no clear evidence for substantial input of Cr from these sources in our study region although benthic inputs of Cr may be locally important in the vicinity of hydrothermal vents. Subsurface waters (below the surface mixed layer to 700 m water depth) were very slightly depleted in Cr (by up to ~0.4 nmol kg-1), and very slightly enriched in heavy Cr isotopes (by up to ~0.14‰), relative to deeper waters and the lowest Cr concentrations and highest δ53Cr values coincided with lowest concentrations of colloidal (0.02 to 0.2 μm size fraction) Fe. We found no direct evidence for biological uptake of dissolved Cr in the oligotrophic euphotic zone or removal of Cr in modestly oxygen depleted waters (O2 concentrations ~130 μmol kg-1). Rather, we suggest removal of Cr (probably in the form of Cr(III)) in subsurface waters is associated with the formation of colloid aggregates of Fe-(oxyhydr)oxides. This process is likely enhanced by the high lithogenic particle load in this region, and represents a previously unrecognized export flux of Cr. Regeneration of Cr in deeper waters leads to subtly increased levels of Cr alongside decreased δ53Cr values at individual sites, but this trend is more obvious at the global scale, with δ53Cr values decreasing with increasing radiocarbon age of deep waters, from 1.16 ± 0.10‰ (1SD, n=11) in deep Atlantic waters to 0.77 ± 0.10‰ (1SD, n=25) in deep Pacific waters. Removal of relatively isotopically light Cr from subsurface waters onto particulate material and regeneration of this Cr back into the dissolved phase in deep waters partly accounts for the systematic relationship between δ53Cr and Cr concentrations in seawater discussed by other studies.

The CoralHydro2k database: a global, actively curated compilation of coral δ18O and Sr ∕ Ca proxy records of tropical ocean hydrology and temperature for the Common Era

Abstract. The response of the hydrological cycle to anthropogenic climate change, especially across the tropical oceans, remains poorly understood due to the scarcity of long instrumental temperature and hydrological records. Massive shallow-water corals are ideally suited to reconstructing past oceanic variability as they are widely distributed across the tropics, rapidly deposit calcium carbonate skeletons that continuously record ambient environmental conditions, and can be sampled at monthly to annual resolution. Climate reconstructions based on corals primarily use the stable oxygen isotope composition (δ18O), which acts as a proxy for sea surface temperature (SST), and the oxygen isotope composition of seawater (δ18Osw), a measure of hydrological variability. Increasingly, coral δ18O time series are paired with time series of strontium-to-calcium ratios (Sr/Ca), a proxy for SST, from the same coral to quantify temperature and δ18Osw variability through time. To increase the utility of such reconstructions, we present the CoralHydro2k database, a compilation of published, peer-reviewed coral Sr/Ca and δ18O records from the Common Era (CE). The database contains 54 paired Sr/Ca–δ18O records and 125 unpaired Sr/Ca or δ18O records, with 88 % of these records providing data coverage from 1800 CE to the present. A quality-controlled set of metadata with standardized vocabulary and units accompanies each record, informing the use of the database. The CoralHydro2k database tracks large-scale temperature and hydrological variability. As such, it is well-suited for investigations of past climate variability, comparisons with climate model simulations including isotope-enabled models, and application in paleodata-assimilation projects. The CoralHydro2k database is available in Linked Paleo Data (LiPD) format with serializations in MATLAB, R, and Python and can be downloaded from the NOAA National Center for Environmental Information's Paleoclimate Data Archive at https://doi.org/10.25921/yp94-v135 (Walter et al., 2022).

Влияние особенностей северо-западной части Черного моря на развитие морской деятельности в регионе

The article highlights a unique geopolitical position and considers the specific features of the northwestern part of the Black Sea including its shallow water, seawater composition, rich natural resources, as well as many transport corridors passing through it. There is carried out analysis of the influence of the specific features on the de-velopment of marine activities in the studied region, development and use of marine resources. Modern ways of the developing international transport corridors and increasing flows of international transit of oil, gas, mineral fertilizers and food allow to consider the northwestern part of the Black Sea as a special transport zone connecting coastal states, as well as the countries of the Caspian and Mediterranean regions with Europe. The factors that make it possible to develop the ports in the region and transport logistics for transportation of goods and passengers between the countries are considered. The role of the significant availability of hydrocarbon reserves in the considered part of the sea in the development of specialized ports and related transport logistics is determined. Analysis of the dependence of the growing intensity of the development of ports and transport logistics on the development of maritime activities for the study, development and use of resources is carried out. It has been inferred about the significant influence exerted by the peculiarities of the north-western part of the Black Sea on the development of maritime activities of the coastal countries including Russia.

Exploratory data analysis (EDA) machine learning approaches for ocean world analog mass spectrometry

Many upcoming and proposed missions to ocean worlds such as Europa, Enceladus, and Titan aim to evaluate their habitability and the existence of potential life on these moons. These missions will suffer from communication challenges and technology limitations. We review and investigate the applicability of data science and unsupervised machine learning (ML) techniques on isotope ratio mass spectrometry data (IRMS) from volatile laboratory analogs of Europa and Enceladus seawaters as a case study for development of new strategies for icy ocean world missions. Our driving science goal is to determine whether the mass spectra of volatile gases could contain information about the composition of the seawater and potential biosignatures. We implement data science and ML techniques to investigate what inherent information the spectra contain and determine whether a data science pipeline could be designed to quickly analyze data from future ocean worlds missions. In this study, we focus on the exploratory data analysis (EDA) step in the analytics pipeline. This is a crucial unsupervised learning step that allows us to understand the data in depth before subsequent steps such as predictive/supervised learning. EDA identifies and characterizes recurring patterns, significant correlation structure, and helps determine which variables are redundant and which contribute to significant variation in the lower dimensional space. In addition, EDA helps to identify irregularities such as outliers that might be due to poor data quality. We compared dimensionality reduction methods Uniform Manifold Approximation and Projection (UMAP) and Principal Component Analysis (PCA) for transforming our data from a high-dimensional space to a lower dimension, and we compared clustering algorithms for identifying data-driven groups (“clusters”) in the ocean worlds analog IRMS data and mapping these clusters to experimental conditions such as seawater composition and CO2 concentration. Such data analysis and characterization efforts are the first steps toward the longer-term science autonomy goal where similar automated ML tools could be used onboard a spacecraft to prioritize data transmissions for bandwidth-limited outer Solar System missions.

Distinct REY sources recorded in the Doushantuo phosphorite

During the Ediacaran period, massive marine phosphorites were deposited worldwide, which could represent a global sink of rare earth elements and yttrium (REY) in oceans. In the Doushantuo Formation of South China, the REY source has been preliminarily constrained as the mixed sources of seawater and terrigenous matter in these phosphorites. However, the REY composition of both seawater and terrigenous endmembers is still unclear; therefore, it’s difficult to identify the contributions of seawater and terrigenous sourced REY. In this work, REY and other trace elements of bulk phosphorites, in situ carbonates, and apatite grains were analyzed from a drill core (Fangmashan) of the Doushantuo Formation in South China. Combined with mineralogical observations, the REY composition of seawater and terrigenous endmembers is well-constrained. Along the investigated Fangmashan drill core, all in situ carbonates (calcites and dolomites) show a modern seawater-like REY pattern, indicating that the REY characteristics of the Doushantuo seawater could be similar to those of modern oxic seawater without significant changes. Alternatively, apatites from the lower and upper phosphorites showed distinct REY patterns. One type of apatite in the upper phosphorites showed a modern seawater-like REY pattern, indicating authigenic REE enrichment from the seawater column. However, another type of apatite in the upper phosphorites with an REE pattern that deviated from seawater showed high ΣREY (∼691.16 ± 309.78) and low Y/Ho (∼40.52 ± 4.05), probably reflecting mixed REY sources and/or the effects of early diagenesis. It is noted that most apatites in the lower phosphorites are obviously enriched in light REY (LREY: La - Nd) compared to heavy REY (HREY: Ho - Lu and Y), which may represent a significant contribution of the terrestrial REY source. This study reveals that the REY composition of paleo-seawater could be similar to modern seawater as early as the Neoproterozoic and supports a significant contribution to understanding the difference in the REY composition of phosphorites in geological history.

Application of the δ44/40Ca-δ88/86Sr multi-proxy to Namibian Marinoan cap carbonates

Several studies have exploited the stable calcium (Ca) and strontium (Sr) isotope compositions of marine carbonate rocks to investigate ancient carbon cycle dynamics, seawater geochemistry, and controls on carbonate production and preservation. However, the two proxies have rarely been applied together. Based on knowledge achieved to date, the δ44/40Ca-δ88/86Sr multi-proxy can distinguish signatures imparted by mass-dependent fractionation and reservoir mixing, including early diagenesis and shifts in the isotopic composition of seawater. In detail, the δ44/40Ca-δ88/86Sr multi-proxy represents a five-isotope system because the determination of δ88/86Sr values requires analysis of fractionation-corrected 87Sr/86Sr ratios, which provide additional constraints on mixing. Here, we apply the novel δ44/40Ca-δ88/86Sr multi-proxy to two Marinoan (ca. 635 Ma) “cap carbonate” sequences from Namibia. Cap carbonates were widely deposited after the Neoproterozoic Marinoan Snowball Earth Event, but controversy surrounds their origin. We find that the rocks archive primary environmental signals deriving from a combination of seawater-glacial meltwater mixing and kinetic isotope effects. In an outer platform section, dolostone δ44/40Ca and δ88/86Sr values define a line predicted for kinetic mass-dependent isotope fractionation. This dolostone mostly precipitated from meltwater. Moreover, stratigraphically higher samples exhibiting the fastest precipitation rates display elevated 87Sr/86Sr ratios, consistent with long-held expectations that a rapid deglacial weathering pulse forced cap carbonate formation. An inner-platform dolostone shows greater effects from water-mass mixing but still reveals that precipitation rates increased up-section. Overlying limestones show greater Ca and Sr contributions from seawater. Amplification of local coastal processes during global ice sheet collapse offers a simple but sufficient proposition to explain the Ca isotope heterogeneity of cap carbonates. Detection of kinetic isotope effects provides evidence for predominantly rock-buffered diagenesis and further offers a basis for developing the δ44/40Ca-δ88/86Sr multi-proxy as an indicator of saturation state and pCO2.

Controls on potassium incorporation in foraminifera and other marine calcifying organisms

Seawater chemistry exerts an important control on the incorporation of trace elements into the shells of marine calcifying organisms. Variability in the major ion chemistry of seawater is a tracer of past geological processes, and the influence of seawater chemistry on trace element incorporation in calcium carbonate can be harnessed to determine changes in the composition of seawater through time. Here, we investigate whether key oceanographic parameters (temperature, salinity, and the carbonate system) affect the incorporation of potassium (K) into foraminiferal calcite, and explore the utility of K/Ca ratios in foraminifera as an indicator of past variability in the seawater Ca2+ concentration. We analysed both low-Mg and high-Mg modern foraminifera, including planktonic (Globigerinoides ruber) and shallow-dwelling larger benthic (Operculina ammonoides) species, using laser-ablation sector-field inductively-coupled plasma mass spectrometry (LA-SF-ICPMS). Both species show no resolvable influence of temperature, salinity, pH, or [CO32−] on K incorporation across the range that these vary at our samples sites. In order to determine the effect of the seawater Ca concentration ([Ca2+]sw) on K incorporation, we analysed laboratory-cultured O. ammonoides, the close living relative of the abundant Eocene Nummulites, grown at four different [Ca2+]sw. We find a significant relationship between seawater and shell K/Ca, albeit with a shallower slope compared to most other trace elements which we suggest is driven by a crystal growth rate effect on K incorporation, constrained using culture experiments of O. ammonoides grown at different pH. If the K+ concentration has remained relatively constant throughout the Phanerozoic Eon, our data may pave the way forward for the use of K/Ca as a direct proxy for past [Ca2+]sw variability. Alternatively, coupling K/Ca with the similar Na/Ca proxy would allow more accurate reconstruction of [Ca2+]sw or verification of whether [K+]sw and [Na+]sw have indeed remained within narrow bounds.