Influence Of Seawater Research Articles

The Influence of Seawater on Fe(II)-Catalyzed Ferrihydrite Transformation and Its Subsequent Consequences for C Dynamics.

Short-range-ordered minerals like ferrihydrite often bind substantial organic carbon (OC), which can be altered if the minerals transform. Such mineral transformations can be catalyzed by aqueous Fe(II) (Fe(II)aq) in redox-dynamic environments like coastal wetlands, which are inundated with seawater during storm surges or tidal events associated with sea-level rise. Yet, it is unknown how seawater salinity will impact Fe(II)-catalyzed ferrihydrite transformation or the fate of bound OC. We reacted ferrihydrite with Fe(II)aq under anoxic conditions in the absence and presence of dissolved organic matter (DOM). We compared treatments with no salts (DI water), NaCl-KCl salts, and artificial seawater mixes (containing Ca and Mg ions) with or without SO42-/HCO3-. Both XRD and Mössbauer showed that NaCl-KCl favored lepidocrocite formation, whereas Ca2+/Mg2+/SO42-/HCO3- ions in seawater overrode the effects of NaCl-KCl and facilitated goethite formation. We found that the highly unsaturated and phenolic compounds (HuPh) of DOM selectively bound to Fe minerals, promoting nanogoethite formation in seawater treatments. Regardless of salt presence, only 5-9% of Fe-bound OC was released during ferrihydrite transformation, enriching HuPh relative to aliphatics in solution. This study offers new insights into the occurrence of (nano)goethite and the role of Fe minerals in OC protection in coastal wetlands.

Features of the Application of Coatings Based on the ZrN System to Increase Resistance to Mechanical Wear and Corrosion of Titanium Alloy Products

The coatings of ZrN, (Zr,Ti)N, (Ti,Zr,Hf)N and (Ti,Zr,Nb)N deposited on the titanium alloy substrate were compared. The wear resistance in the pin-on-disk test together with the Al2O3 indenter and the corrosion resistance in 3.5% NaCl solution were studied. It was found that the (Zr,Nb,Ti)N coating has the best resistance to wear, but has low corrosion resistance. The (Ti,Zr,Hf)N coating, on the contrary, has the best corrosion resistance, but low resistance to wear. The ZrN coating has good corrosion resistance combined with good resistance to wear. This coating is best suited for use in friction conditions with a ceramic counterbody under the influence of seawater. An important resource for increasing the properties of coatings is increasing their adhesion to the substrate, which can be achieved in two combined ways: (1) complete removal of the original oxide layer from the surface of the substrate and (2) the use of optimal compositions of the adhesive sublayer, which have not only high adhesive properties in relation to both the substrate and the coating, but also high strength. While the introduction of Nb into the ZrN coating composition increases wear resistance and the introduction of Hf increases corrosion resistance, the ZrN coating without additives best resists wear and corrosion simultaneously.

Characterization of surface integrity of 7075-T6 aluminum alloy subjected to microbiologically induced corrosion during high-speed machining

Microbiologically Influenced Corrosion (MIC) is one of the primary causes of corrosion damage and equipment failure in industrial environments. This paper aims to investigate the impact of microbiologically influenced corrosion on the surface integrity of 7075-T6 aluminum alloy. Through experiments involving cryogenic treatment and machining, the study systematically compares the effects of different microbiologically influenced corrosion environments on 7075-T6 aluminum alloy. Techniques such as X-ray Diffraction (XRD), surface roughness measurement, Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and work hardening were used to elucidate the influence of natural seawater (Planktonic microorganisms, PM) and marine sediment (Benthic microorganisms, BM) corrosion on the surface integrity of 7075-T6 aluminum alloy.The results indicate that, compared to PM corrosion, BM corrosion results in a smaller surface roughness of 7075-T6 aluminum alloy. Specifically, the BM-10d specimen exhibits the smallest roughness at 0.353 μm. XRD and EDS analyses show that the corrosion products after microbiological corrosion are primarily a mixture of Al2O3, AlO(OH), and Al(OH)3. The peak intensity of AlO(OH) in the (200) crystal plane of the BM-5d corrosion product is notably higher than that of the 7075-T6 aluminum alloy under other conditions. In the PM environment, the corrosion products fully cover the entire surface of the workpiece and are accompanied by significant cracking. In contrast, in the BM environment, the corrosion products mainly exhibit a granular structure, are scattered across the workpiece surface, and the exposed substrate can be observed.The microhardness of the aluminum alloy after microbiological corrosion shows a trend of increasing initially, then decreasing, and finally stabilizing. The maximum depth of the hardened layer for PM-10d is 120 μm, with a maximum hardness of 178.74 HV. Compared to PM corrosion, BM corrosion results in a significantly greater hardened layer depth for 7075-T6 aluminum alloy, with the BM-10d hardened layer depth reaching approximately 140 μm and the peak hardness at 185.36 HV. Additionally, in the BM environment, the precipitates are fewer compared to those in the PM environment and exhibit a non-continuous, non-grain-boundary precipitation band.

Pengaruh Air Laut terhadap Kuat Tekan, Permeabilitas, dan Mikrostruktur Beton Geopolimer dengan Flyash dan Tanah Putih sebagai Pengganti Semen

The increasing infrastructure development of an area is sometimes located in an aggressive environment, one of which is in coastal areas so that direct contact with sea air cannot be avoided. This research aims to determine the effect of sea water on geopolymer concrete using fly ash and white soil as cement substitutes with testing parameters for compressive strength, permeability and microstructure. The test objects used were cylindrical in shape measuring 150x300 mm and 100x200 mm. The ratio of fly ash and white soil used was 85%:15% and the activator used was NaOH 8M and Na2SiO3 with a ratio of 1:2,5. The mixture proportion using a ratio of 1 fly ash: 1,497 sand: 2 split: 0,451 alkali activator with a mutual plan is 35 MPa. Tests were carried out after the concrete had gone through a curing process for 56 days, then the concrete was conditioned without soaking and with soaking for 28 days. Tests were carried out at concrete ages of 56 and 87 days. The test results show that geopolymer concrete with the influence of sea water has a higher compressive strength value and a smaller permeability coefficient compared to concrete without the influence of sea water. Microstructural testing of geopolymer concrete under the influence of sea air produces a matrix-shaped structure morphology that is denser with fewer pores compared to concrete without the influence of sea air.

Study on the Diffusion Mechanism of Infiltration Grouting in Fault Fracture Zone Considering the Time-Varying Characteristics of Slurry Viscosity Under Seawater Environment

Fault fracture zones are rock formations commonly encountered in submarine tunnels, and the diffusion mechanism of slurry in fault fracture zones has a crucial impact on submarine tunnel reinforcement. Based on the seepage equation of Bingham fluid, the tortuosity parameter, fractal theory, and variable viscosity equation are introduced to establish a spherical permeation grouting model of Bingham fluid considering the slurry diffusion path and viscosity time variability. The viscosity variation law with time of sulfur aluminate cement slurry under different seawater admixture conditions was tested, and the time-varying equation of viscosity of sulfur aluminate cement slurry was obtained by fitting. A set of fault fracture zone permeation grouting test system was developed, and a fault fracture zone grouting simulation test was carried out. The study shows that the diffusion distance calculated without considering the influence of slurry diffusion path and seawater is 1.63–1.91 times of the test value, which obviously overestimates the diffusion distance; the diffusion distance calculated with considering the influence of diffusion path and seawater is 1.06–1.35 times of the test value, which is in good agreement with the test value. The research results can provide some theoretical support for the design of grouting in seawater environment.

An experimental study on the wear performance of 3D printed polylactic acid and carbon fiber reinforced polylactic acid parts: Effect of infill rate and water absorption time

AbstractRapid prototyping, also known as additive manufacturing, is a nascent technology that is gaining traction in the context of environmental concerns and waste reduction, as well as the growing trend towards customized design. The additive manufacturing method, which has applications in diverse fields such as aviation, architecture, biomedical and automotive engineering, has also begun to be utilized in the construction of yachts and yacht hulls within the maritime industry. In this experimental study, the influences of sea water on polylactic acid (PLA) and carbon fiber reinforced polylactic acid (PLA/CF) parts manufactured at different infill rates (20%, 60% and 100%) were investigated. The parts were exposed to sea water for three different periods (1, 5, and 10 days) and subsequently subjected to wear tests. The dimensional accuracy, surface roughness, hardness, water absorption, volume loss, and friction coefficient of parts were measured and calculated. Additionally, the worn surfaces of the parts were investigated using field emission scanning electron microscope (FESEM) images. The findings indicate that PLA and PLA/CF parts can be produced with high dimensional accuracy. Furthermore, it can be reported that the water absorption of PLA/CF parts increased, particularly with an increase in the infill rate, while the volume loss decreased. Obtained results indicate the necessity of optimizing the 3D printing parameters and the relationship between the ambient conditions and the wear performance of the 3D printed parts.Highlights 3D printing is a highly promising method for the production of polymer composites. A pioneering study into the effect of infill rate and water absorption on the wear performance. Coefficient of friction values of PLA and PLA/CF parts ranged between 0.37 and 0.75. PLA/CF mostly exhibited higher volume loss than PLA with water absorption. Volume loss declines with a raise in the infill rate from 20% to 100%.

Quality and health impact of groundwater in a coastal region: a case study from west coast of southern India.

Seawater intrusion seriously threatens the quality of coastal groundwater, affecting nearly 40% of the world's population in coastal areas. A study was conducted in the Kamini watershed situated in the Udupi district of Karnataka to assess the groundwater quality and extent of seawater intrusion. During the pre-monsoon period, 57 groundwater and 3 surface water samples were analyzed to understand the impact of seawater on the groundwater and surface water. The analysis revealed that the groundwater in the study area is slightly alkaline. The weighted overlay analysis map indicated that 11% of the study area is unsuitable for drinking water due to the influence of seawater. The Piper plot analysis revealed that the groundwater is predominantly CaMgCl facies. The hydrogeochemical facies evolution diagram (HFED) showed that 62% of the groundwater is affected by seawater. The HFED and Piper plots also indicate that the surface water is also affected by seawater. These results are also supported by various molar ratios such as Cl- vs. Cl⁻/HCO3⁻, Cl⁻ vs. Na⁺/Cl⁻, Cl- vs. SO42-/Cl-, and Cl⁻/HCO3- vs. Mg2+/Ca2+, suggesting that the majority of the water sample has been affected by seawater. The saturation indices indicated that mineral dissolution has significantly contributed to groundwater salinization. The correlation between sulfate concentration and calcite and dolomite dissolution suggested the influence of seawater intrusion in the coastal aquifer. The process of reverse ion exchange mainly influences the groundwater chemistry according to chloroalkali indices. The total hazard index (THI) values of nitrate and fluoride exceeded limits, posing health risks to adults and children. Studies suggest that with time and space, seawater intrusion is increasing in some pockets of the study area, especially along the west coast.

Insights on physiological, antioxidant and flowering response to salinity stress of two candidate ornamental species: the native coastal geophytes Pancratium maritimum L. and Eryngium maritimum L

Increasing seawater influence in coastal areas is an ongoing environmental issue. Gardening is a widespread activity mainly in touristic areas such as the Mediterranean coasts. However, the use of exotic species well adapted to salinity encompasses the risk of invasive species introduction. This study aimed to evaluate salinity tolerance of native geophytes, Pancratium maritimum L. and Eryngium maritimum L., to assess their use as ornamental species in salt affected coastal areas. Experiments were conducted using cultivated plants for flowering response and physiological and enzymatic antioxidant response. Six treatments were applied for two months, exposing plants to seawater (SW) dilutions (Tap-Water, 6.25%SW, 12.5%SW, 25%SW, 50%SW and 100%SW). Taxa decreased inflorescence production being this effect more architectonical in E. maritimum and affecting all inflorescence integrity in P. maritimum. Flowering time was strongly delayed and reduced in P. maritimum, while E. maritimum showed smaller effects among treatments. Physiological and biochemical response showed at moderate salinity levels (1/4SW) variation concomitant with late stress response and senescence in P. maritimum, with decreased water use efficiency, NPQ values, and enzymatic activity, and increased malondialdehyde (MDA) levels. In contrast, E. maritimum showed early stress response with steady gas exchange response, increasing NPQ values and catalase (CAT) and superoxide dimutase (SOD) activity, and decreasing MDA levels with salinity. Glutathione enzymes showed limited participation in both species. The results of this study suggest that neither species can be classified as halophytes, but they exhibit tolerance to low and moderate salinity levels, making them suitable for ornamental use.

Mineralogical and Geochemical Composition of Late Permian Coals from Dengfeng Coalfield, North China: Conversion of Clay Minerals in Coal during Coalification

Dengfeng Coalfield represents a significant coalfield in Henan Province, North China. It is therefore essential to gain an understanding of the mineralogy and geochemistry of the Dengfeng coal, both from a geochemical perspective and in terms of the wider environmental context. In this study, a total of 27 coal bench samples were collected from the No. II1 coal of the Dengfeng Coalfield. The mineral species and major elements were quantitatively analysed using the X-ray diffraction and X-ray fluorescence methods, respectively. The minerals in the Dengfeng coal are dominated by ammonian illite and kaolinite with average contents of 3.73% and 7.47%, respectively. These are followed by calcite (2.74% on average) and ankerite (0.49%). The mean value of the kaolinite Hinkley index, which is a quantitative measure of kaolinite crystallinity, is 1.26. This suggests that kaolinite formation is primarily driven by diagenetic recrystallisation. The ammonian illite exhibits an average d001 of 10.2995 Å, indicative of a prevalence of NH4+ interlayer cations, with K+ also present in notable quantities. The ratio of NH4⁺ to (NH4⁺ + K⁺) has an average value of 0.90, which is indicative of the predominance of NH4⁺. The mean value of the illite Kübler index, which is a quantitative measure of illite crystallinity, is 0.264. This suggests that the diagenetic conditions correspond to the rank of the Dengfeng coal. The kaolinite present in the Dengfeng coal is suggested to have been derived from terrigenous detritus and subsequently subjected to diagenetic recrystallisation, resulting in a relatively high Hinkley index. The ammonian illite in the Dengfeng coal was predominantly formed through the conversion of the precursor kaolinite, with the influence of seawater during peat accumulation favouring the conversion of kaolinite to ammonian illite.

Geochemistry of BIF in the Quadrilátero ferrífero, Brazil, as a proxy to neoarchean paleoenvironmental and depositional conditions

Precambrian Algoma-type banded iron formations (BIFs) are biochemical metasedimentary rocks formed in the deep water environment relatively close to centers of volcanic expansion and can be characterized on the basis of their paleodepositional environment and the associated rock types. These rocks may contain geochemical signatures indicative of changes in the redox conditions of the Archean ocean. Such variations in the Meso- and Neoarchean are crucial in understanding the processes that led to the gradual increase of oxygen in the early atmosphere, culminating in the Great Oxidation Event (2.4–2.3 Ga). Oxide- and carbonate-facies BIFs were intercepted by drill cores in the Pilar gold deposit in the NE sector of the Quadrilátero Ferrífero (QF), Brazil, located in the Neoarchean Rio das Velhas greenstone belt. These rocks are interbedded with mafic and ultramafic metavolcanic rocks and carbonaceous phyllites. In light of the potential to reconstruct paleodepositional evidence indicative of the Earth's atmospheric redox history based on this stratigraphy, we have considered specific proxies from geological and geochemical observations. Pilar BIFs geochemistry exhibits positive anomalies of La, Eu, and Y, indicating characteristics inherited from seawater and high-temperature hydrothermal fluids. In addition, a superchondritic Y/Ho ratio further supports the influence of seawater. The signatures of the major elements Al2O3 and other immobile elements typical of detrital sediments corroborate the interpretation that these rocks were deposited in a deep marine environment with low clastic influence. Furthermore, negative Ce/Ce*SN anomalies in some sections of the Pilar BIF indicate limited oxygen availability which, together with Mo, U, V, and Zn trace-element enrichment factors, indicate deposition under suboxic/euxinic conditions. This research, together with other similar BIF data from the NW QF provide new insights into the paleoenvironmental conditions prevailing during the formation of the Archean volcano sedimentary basins that compose the southern São Francisco craton (SFC).

Seagrasses on the move: Tracing the multi-decadal species distribution trends in lagoon meadows using Landsat imagery

Seagrass meadows play a vital role for lagoon ecosystems and their biota, sustaining multiple ecosystem services. Their distribution and functioning are closely tied to the environmental pressures induced by global changes. Long-term monitoring of seagrass species and communities is, hence, important to depict their response to past and future scenarios. The availability of long term open-access satellite data offers a new remote sensing perspective for monitoring seagrass communities dynamics in shallow waters, especially when combined with machine learning algorithms. In this study, seasonal multispectral images (from 1999 to 2019) were collected from Landsat 5 Thematic Mapper and 8 Operational Land Imager satellites to map the seagrass meadows, at the community and species levels, within the vast Grado and Marano lagoon (Northeast Italy) using a Random Forest (RF) algorithm. RF models were calculated using an extensive field training dataset collected in 2010 (n = 426) and reached an overall accuracy of 0.92 and 0.76 for the classification at the community and species levels, respectively. The change detection analysis revealed an increase of 14.16 km2 (+ 39%) of the whole seagrass community cover over the period, at a rate of 1.59 km2year−1. Despite the coarse spatial resolution (30 m) of the Landsat's images, the classification of seagrasses at species level achieved a good overall accuracy (0.76), evidencing Nanozostera noltei as the species with the highest cover increase (+13.87 km2 over the time period). The observed expansion is likely caused by an increase of the sea water influence that is radically modifying Adriatic brackish water bodies, emphasizing the connection between the ongoing environmental changes and the rapid responses of seagrass meadows.

The Chemical Composition of some Waters from Slacks in Rameswaram Island, Madras State

Analyses of pH, total dissolved solids, CO,, HCO3, Cl, SO4, Ca, Mg, Na and K are presented for water samples from dune slacks in Rameswaram Island. Comparison of these analyses has been attempted with well waters from the area, sea water and world average fresh water. It is inferred that these slacks are under the influence of sea water but ion-exchange process similar to those in arid alkali soils appear to be responsible for Ca/HCO3 ratios of less than unity and Na/Cl and Mg/Cl ratios greater than those in sea water. Exceptionally high Na2Co3 and NaHCO3, contents in one of the slack waters is explained on the basis of sulphate reduction due to favourable conditions developed locally there.

The Quality and Classification of some Slack Water at Digha Shore, Midnapur District, West Bengal

Slack waters at Digha, Midnapur district, West Bengal are used for irrigation in Betel Cultivation. For quality of slack waters, estimations for pH, T. S. S., CO2, HCO3, Cl, SO4 Ca, Mg and Na were done. These slack Waters are compared - with the local sea water and world average Fresh water It is inferred that these slack waters-are not under the Influence of sea water and can well be compared with world average fresh water. Salinity and sodium hazards are low in slack waters, as such they can be used for irrigation with advantage.

Eco-sustainable design of seawater sea-sand slag-based geopolymer mortars incorporating ternary solid waste

This study aimed to explore the feasibility of utilizing geopolymer as alternatives to Ordinary Portland Cement (OPC) in marine engineering. Eco-friendly seawater sea-sand slag-based geopolymer mortars (SS-SGMs) were prepared by blending seawater, sea-sand, Basalt Fibres (BF), Polypropylene Fibres (PPF), and ternary solid waste. The effects of activator modulus, alkaline content, water-to-binder ratio, and the volume fractions of BF and PPF on the mechanical performance, environmental impact, and cost of SS-SGMs were researched using the L16(4)5 Taguchi orthogonal method. Three evaluation methods were used to assess the impact of the different factors. First, the influence of a single factor was analyzed using methods of range and variance analysis. Subsequently, three new evaluation metrics were proposed to consider the synergistic effects of mechanical performance, environment, and cost. Finally, a Gray-Technique of Ordering Preferences by Similarity to Ideal Solution (Gray-TOPSIS) model was established, and the influence weights of each factor were proposed, thereby determining the optimal solution in a multi-index evaluation system. The recommended optimal mix proportion for SS-SGMs was determined as follows: activator modulus of 1.0, alkaline content of 4%, water-to-binder ratio of 0.42, PPF volume fraction of 0.4%, and BF volume fraction of 0.3%. Compared to OPC with the same strength grade, SS-SGMs demonstrated similar costs, a reduction in carbon emissions by approximately 75–83%, a decrease in energy consumption by around 50–67%, and lower drying shrinkage than traditional geopolymer. Under the influence of seawater, the products of SS-SGMs were capable of forming chloride-ion adsorbing products like hydrotalcite and Brucite. Additionally, the formation of C4AH13 and ion clusters can enhance the matrix density, thereby improving the mechanical performance of SS-SGMs.

Hydrogeochemical characterization and water quality evaluation for drinking and irrigation purposes of coastal aquifers of Middle Andaman

A comprehensive study to characterize the hydrogeochemistry of the region and the impact of saltwater intrusion on groundwater was conducted along the eastern coast of Middle Andaman of Andaman and Nicobar (A&N) Islands. The escalating population growth and intensified tourism activities have resulted in the over-extraction of groundwater. Seismic activities led to the opening of lineaments to the sea and the dissolution of limestone in the influence of seawater. 24 groundwater samples and 1 reference sample from sea were taken from various locations of middle Andaman. The analysis involved the determination of major cations, anions, and heavy metals using Inductively Coupled Plasma Optical Emission spectroscopy (ICP), spectrophotometry, and flame photometry. Furthermore, X-ray diffraction analysis, binary diagrams, Chloro-alkaline indices (CAI), Gibbs Plot, correlation matrix, Piper plot, Chadha’s plot and Principal Component Analysis (PCA) to the major ions data indicated rock-water interactions, strong correlations among alkali and alkaline earth metals, and interactions between seawater and carbonate minerals respectively. The water quality index indicated “very poor to unsuitable for drinking purposes” in 24% of the samples. Additionally, indices for irrigation suitability; total hardness (TH), residual sodium carbonate (RSC), and Magnesium adsorption ratio (MAR) were found to be detrimental for irrigation in 80%, 08%, and 12% of the water samples, respectively. These results highlight the importance of implementing effective water resource management techniques, such as groundwater extraction rates, adopting appropriate water treatment technologies to mitigate the adverse impacts of heavy metals, saltwater intrusion and maintain water quality for human consumption and agricultural use in the region.

Effects of the 2021 La Palma volcanic eruption on groundwater hydrochemistry: Geochemical modelling of endogenous CO2 release to surface reservoirs, water-rock interaction and influence of thermal and seawater

Volcanic islands face unique challenges in protecting and managing their water resources due to their small size, limited freshwater availability, and vulnerability to natural hazards. The recent 2021 eruption of the Tajogaite volcano on La Palma Island in the Canary Islands, Spain, raised concerns regarding the potential impact on groundwater hydrochemistry. This work aimed to characterize and model the processes that lead to the measured hydrochemical impacts in the groundwater of La Palma as a consequence of the volcanic eruption. The study involved conducting three groundwater sampling campaigns during the eruption, and six after the eruption ceased. A total of 15 monitored points, including piezometers, wells, water galleries, and the main gully collector of the island, all relatively close (2 to15 km) to the erupted volcano, were sampled for the analysis of major solutes and SiO2. Unpublished hydrochemical data previous to the eruption were provided by the local water management authorities of La Palma (CIALP) and the Geological Survey of Spain (IGME). Statistical analyses were performed to assess the differences in groundwater composition before, during, and after the eruption, and a Principal Component Analysis (PCA) mixing model was calculated. Three compositional extreme waters were defined as end members in the system: (1) a high SiO2 computed thermal end member; (2) a low salinity computed fresh groundwater; (3) and seawater. The results of the mixing model showed two main events of maximum mixing ratios in the fresh groundwater reservoirs of La Palma after the eruption; the first one of seawater in July 2022, and the next one of thermal fluids in December 2022. This water mixing during and after the eruption, together with a volcanic CO2 input to the reservoirs, led to significant increases in the concentrations of Na, Ca, SiO2 and SO4 in fresh groundwater, as well as a drop in pH. The significance of these findings relies in improving our understanding of the effects of volcanic eruptions on groundwater, emphasizing the necessity for frequent monitoring and evaluation, given the scarcity and vulnerability of groundwater resources in volcanic islands.

Unravelling the genesis and depositional setting of Neoproterozoic banded iron formation from central Eastern Desert, Egypt

The Neoproterozoic banded iron formations (BIFs) are widely occurred in the Egyptian Eastern Desert. This study integrates field observations, petrographic studies, geochemical data, and lead isotopes to construct the genesis and depositional environment of Wadi El-Mis hama BIF deposits. The iron layers, primarily of oxide facies within a volcano-sedimentary sequence, comprise magnetite-rich beds alternating with jaspilite or silicate laminae. The studied BIFs exhibit a dominant composition of SiO2 and Fe2O3t with relatively low contents of TiO2 and Al2O3. The positive correlation of REEs (La, Sm, Yb) with Zr and low concentrations of HFSEs (Ta, Nb, Th, Hf) indicate a primary formation mechanism of chemical precipitation, maintaining original geochemical signatures. Geochemical patterns show depletion in LREEs, enrichment in HREEs (La/YbPAAS = 0.08–0.12), and positive La anomalies (La/LaPAAS = 1.15–8.57), consistent with seawater influence. Additionally, various geochemical discrimination diagrams supported by elevated super-chondritic Y/Ho values (29.6–38.7), weak positive Eu anomalies, and low contents of transition metals (Cu and Zn), point to the interaction of low-temperature (<200°C) hydrothermal fluids (bearing Fe and Si) with seawater during the deposition of the BIFs. The lack of significant negative Ce anomalies along with low Ni/Co, U/Th, and Cu/Zn ratios, imply that the iron mineralization was precipitated from dysoxic to oxic conditions. The geochemical and Pb isotopic data suggest that the iron deposits formed in an extensional geodynamic setting (intra-oceanic arc basin environment) due to the subduction of the Mozambique Plate, with signatures closely matching other Precambrian Algoma-type BIFs.

Response to Seawater Exposure During the Flowering Stage of Two Dune-Building Grasses: Calamagrostis arenaria (L.) Roth and Thinopyrum junceum (L.) Á.Löve

Human disturbance and seawater intrusion have unpredictable effects on coastal species. Dune systems are crucial coastal habitats because they provide natural front protection against seawater influence. Adult plant stands in dunes are important since they maintain dune structure. This study evaluated salinity stress responses in adult plants of two key dune-building grasses differing in salt tolerance: Thinopyrum junceum (tolerant) and Calamagrostis arenaria (less tolerant). Cultivated plants were exposed to various seawater (SW) dilutions (Tap-Water, 6.25%, 12.5%, 25%, 50%, and 100%) and gas exchange measurements and oxidative stress biomarkers were determined after two months of treatment. Stress conditions were maintained until flowering to assess effects on the reproductive effort. The reproductive response showed high plasticity at various inflorescence stages in T. junceum, minimizing abortion processes. C. arenaria showed lower plasticity and higher abortion rates. Physiological traits responded similarly to salinity in both species, with greater effect on Fv/Fm decrease and non-photochemical quenching increase for T. junceum. Biochemical patterns of response were also similar, with increasing enzymatic activities at 25% SW treatment, mainly for glutathione reductase and peroxidase (GSH and GPx), and stress damage occurring at 50% and 100% SW treatments for increased malonaldehyde (MDA) levels. These findings provide insight into the salinity tolerance mechanisms of dune-building grasses. Higher salinity tolerance is suggested for T. junceum based on better reproductive effort. Higher juvenile tolerance, faster growth, and plant cycle adjustments are indicated as key traits for higher salinity tolerance of T. junceum in contrast to C. arenaria.

Effects of seawater and sea sand on early creep of concrete under different stress levels

Early-age creep of seawater sea sand concrete has a profound effect on construction engineering. This study investigates the ramifications of seawater and sea sand on the early-age creep behavior of concrete subjected to different compressive stresses. To discern the impact of seawater and sea sand on deformation, creep tests were conducted. In parallel, mechanical tests, shrinkage deformation tests, and capillary water absorption tests were conducted to elucidate the influence of seawater and sea sand on macroscopic performance. Moreover, mercury intrusion porosimetry and scanning electron microscopy were deployed to scrutinize the concrete's pore structure and microstructure. The findings reveal that seawater and sea sand precipitate augmented shrinkage and creep deformations in concrete, with seawater exerting a more pronounced effect. Furthermore, seawater and sea sand diminish the porosity of concrete, optimizing its pore structure by curtailing the count of large pores and augmenting the number of gel pores and capillary pores, thereby bolstering its durability. Seawater also reduces the critical stress threshold for the manifestation of nonlinear creep in early-age concrete, while sea sand exerts a minimal influence. These insights hold substantial implications for comprehending the influence of seawater and sea sand on the early-age creep of concrete and offer valuable guidance for their practical deployment in engineering projects.

Observations of Atmospheric Corrosion Testing on Heated Austenitic Stainless Steel Surfaces: Exploring the Role of Inert Dust Particulates and Seawater

Relevant atmospheric corrosion laboratory testing environments were developed to explore the influence of inert dust and seawater on the corrosion susceptibility of stainless steel in spent nuclear fuel dry storage conditions. Measurements from dust collected on in-service dry storage canisters were applied to develop exposure conditions. Three atmospheric exposure conditions, two static and one cyclic, were examined with three different surface coverages: co-deposited large dust and seawater, co-deposited small dust and seawater, and solely seawater. Stainless steel coupons representative of spent nuclear fuel dry storage canister material were subjected to the various corrosion environments, with the results from exposures up to 1 year presented here. Post exposure, corrosion damage was analyzed using optical microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Initial observations are presented herein, and potential implications with respect to the influence of inert dust particles on corrosion susceptibility are summarized. In general, the co-deposition of dust and salt resulted in larger pits and exhibited mixed modes of corrosion that were not observed in the no-dust conditions (i.e., crevicing, filiform, and pits within pits). The presence of the inert dust may influence brine spreading and/or act as crevice formers, leading to enhanced corrosion. This study highlights the significance of incorporating dust particulate(s) beyond the deliquescent chemistries to fully evaluate atmospheric corrosion severity.