Temperature Salinity Research Articles

Water column properties associated with massive algal bloom of green Noctiluca scintillans in the Arabian Sea

An algal bloom of Noctiluca scintillans (NS) was monitored for 20 days in the Arabian Sea during February 2017. The stations under the influence of NS had low temperature and high salinity compared to outside indicating influence of convective mixing. The microscopic cell count of NS reached a value of 52,600 cells l−1. The surface variability in oxygen and pCO2 measured alongside showed a strong disconnect. Modest supersaturation of surface waters (ΔpCO2 = 3–75 μatm) was observed around the NS bloom compared to outside. However, as these stations were under the influence of convective mixing, the observed change in pCO2 due to subsurface ventilation cannot be ruled out. From the viewpoint of climate change and its influence on oceanic processes, constant monitoring of this bloom becomes essential due to its survival strategy in nutrient-depleted conditions and light of the present observations.

Three-dimensional characteristics of mesoscale eddies in the western boundary current region of the Bay of Bengal using ROMS-NPZD

Eddies play an important role in transporting and redistributing the heat, salt, and biological parameters in the global ocean. In this study, three-dimensional physio-biochemical characteristics of an anticyclonic (AE) and a cyclonic eddy (CE) associated with the poleward western boundary current (WBC) in the Bay of Bengal (BoB) are analyzed using a coupled bio-physical ocean model (ROMS-NPZD). Due to eddy-induced upwelling (downwelling) associated with the CE (AE), monopole patterns of temperature and salinity anomaly around the eddy center are occurred with extremum values at 100 – 150 m and 50 – 100 m depth, respectively. The upward (downward) curvature with a tip at eddy centers is observed in the isothermal layer depth, 20℃ isotherm (D20) nutricline, and oxycline. The depth of D20 deepens and shallows at the center from the edge by ∼60 m and ∼40 m for AE and CE, respectively. A relatively thick barrier layer around the center of AE is noted as compared to the CE. Within eddy interior, temperature and salinity tendencies of horizontal advection show a strong dipole pattern with extremum at eddy edges. The AE currents show positive tendencies in horizontal advection of temperature (salinity) at its northeastern (southwestern) side, which is totally opposite to that of CE. Intense horizontal advections in the adjacent flanks of eddies to the eastward jet of the WBC are due to their strong interactions. Vertical advection shows a quadrupole structure with alternating positive and negative cells within the eddies following the distorted vertical velocity field. Diffusion terms within eddies are quite small compared to the advection. Abundances of chlorophyll-a (∼1.2 mg/m3) at the base of the mixed layer around the CE center are absent for the AE.

A correlation of heat transfer for falling film evaporation on the horizontal tube with multiple-precision expansion method

The falling film evaporation of water and seawater outside the horizontal tube is experimentally investigated under non-boiling condition, and the effects of spray density, evaporation temperature, tube pitch, circumferential position and seawater salinity on the falling film evaporation are studied. A competitive mechanism, based on the analysis of liquid film, is proposed to analyze the critical Reynolds number of the spray water, ReΓ, and the dual effects of liquid film on heat transfer coefficient. The experimental data covers tube diameter D=19∼38 mm, tube pitch s/D=1.3∼2.25, evaporation temperature Tsat=50∼70 °C, spray Reynolds number ReΓ=118∼1979, and salinity S=0∼60 g/kg. By summing up a large number of experimental data, the heat transfer coefficient correlation applying both water and seawater falling film evaporation on horizontal tubes is proposed. The correlation is also compared with previous studies about water and seawater, which shows a better and wider adaptability to experimental conditions.

Preparation and performance evaluation of PDDSA-MS composite as high temperature and high salinity filtration additive

Drilling operations in deep and ultra-deep wells encounter challenges arising from high temperature and saltwater intrusion, leading to reduced drilling efficiency and deteriorated performance of water-based drilling fluids. In order to alleviate the problem of increased filtration of drilling fluid under harsh environment, the composite (PDDSA-MS) was prepared by free radical polymerization using N, N-dimethyl acrylamide (DMAA), Dimethyl diallyl ammonium chloride (DMDAAC), Sodium styrene sulfonate (SSS), 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and KH570 modified SiO2 as raw materials. This composite contained absorption groups, hydration groups, rigid groups and nanomaterials. Through rigorous performance evaluations, it was observed that the addition of 1 wt% composite to a fresh water drilling fluid, resulting in a remarkably low filtration of 8.8 mL after aging at 260 °C. Furthermore, when 3 wt% composite was added to the 15 wt% NaCl salt water drilling fluid, the filtration was 8 mL after aging at 220 °C. This was attributed to the particle size of the composite and its ability to maintain the dispersion stability of drilling fluid, decelerate bentonite agglomeration, and make the surface of the formed filter cake dense and smooth. These findings demonstrated the thermal stability exhibited by composite, offering an effective solution for drilling operations in deep and ultra-deep wells.

China's conservation and restoration of coastal wetlands offset much of the reclamation-induced blue carbon losses.

China's coastal wetlands have experienced large losses and gains with rapid coastal reclamation and restoration since the end of the 20th century. However, owing to the difficulties in mapping soil organic carbon (SOC) in blue carbon stocks of coastal wetlands on a national scale, little is known about the spatial pattern of SOC stock in China's coastal wetlands and the loss and gain of SOC stock following coastal reclamation, conservation, and restoration over the past decades. Here, we developed a SOC stock map in China's coastal wetlands at 30 m spatial resolution, analyzed the spatial variability and driving factors of SOC stocks, and finally estimated SOC losses and gains due to coastal reclamation and wetland management from 1990 to 2020. We found that the total SOC stocks in China's coastal wetlands were 77.8 Tg C by 2020 with 3.6 Tg C in mangroves, 8.8 Tg C in salt marshes, and 65.4 Tg C in mudflats. Temperature, rainfall, and seawater salinity exerted the highest relative contributions to SOC spatial variability. The spatial trend of SOC density gradually decreased from south to north except for Liaoning province, with the lowest density in Shandong province. About 24.9% (19.4 Tg C) of SOC stocks in China's coastal wetlands were lost due to high-intensity reclamation, but SOC stock gained from conservation and restoration offset the reclamation-induced losses by 58.2% (11.3 Tg C) over the past three decades. These findings demonstrated the great potential of conservation and restoration of coastal wetlands in reversing the loss trend of blue carbon and contributing to the mitigation of climate change toward carbon neutrality. Our study provides significant spatial insights into the stocks, sequestration, and recovery capacity of blue carbon following rapid urbanization and management actions, which benefit the progress of global blue carbon management.

A salt-induced smart and tough clean hydrofracturing fluid with superior high-temperature and high-salinity resistance

Hydraulic fracturing is an important technology to improve oil and gas productivity for reservoirs of both conventional and unconventional. To minimize reservoir damage during hydraulic fracturing, researchers have aimed to develop clean fracturing fluids based on viscoelastic surfactants (VESs); however, reduced efficiency at high temperature and high salinity limits their wider applications. Here, an ultra-long-chain cationic surfactant docosyl(trimethyl)azanium chloride (DCTAC) was proposed to prepare fracturing fluid in the presence of high content of various inorganic salts to address this problem. DCTAC shows excellent salt tolerance, forming a homogeneous solution in 22 % NaCl or 55 % CaCl2 at 60 °C, which is several times higher than that for previously reported VESs. Salt can induce DCTAC to form an entangled three-dimensional wormlike micelles network, imparting the bulk fluid excellent rheological properties. DCTAC-thickened fluids show good sand-carrying and gel-breaking performance, and they can resist a temperature of up to 140 °C and a salinity level of at least 16 × 104 mg‧L−1. Compared with previously reported clean fracturing fluids, DCTAC-thickened fluid shows superior high-temperature and high-salinity resistance. The mechanism is elaborated and discussed. The findings in this study are helpful to understand surfactant aggregates stability and assist the development of novel stable supramolecular nanostructures.

Fluid provenance and genetic type of the Bubin Cu-Pb polymetallic deposit, Kohistan-Ladakh island arc, north Pakistan: Evidence from mineralogy, fluid inclusion and O-H-S-Pb isotopes

The Bubin Cu-Pb polymetallic deposit in Gilgit-Baltistan, Pakistan, is a well-known vein-type ore deposit located in the Kohitan-Ladakh island arc. Due to its significant economic importance as the most important deposit type in the Kohistan-Ladakh island arc, a comprehensive study on its ore genesis, fluids evolution, and genetic classification not only shed new light on our understanding the formation of such polymetallic deposit at a typical intra-oceanic arc, but also of help for the mineral exploration. Here, we present the results from electron probe micro-analyzer, fluid inclusions, Raman spectroscopy, and isotopic studies (O-H-S-Pb) to gain insights into the source of ore-forming fluids and materials, as well as the genetic-type and mechanism of ore precipitation for the Bubin deposit. The mineralization processes were divided into three main stages: Stage I (quartz-pyrite), Stage II (quartz-sulfide), and Stage III (quartz-carbonate). Stage II further comprised two sub-stages: IIa (quartz-chalcopyrite-magnetite) and IIb (quartz-galena-fahlore). The ore-forming fluids exhibited high to moderate temperatures (154–540 °C) and varying salinities (0.35–44.30 wt% NaCl) throughout the stages. Stage I fluids displayed critical behavior with high temperature and low salinity, and their isotopic signatures suggested a magmatic origin. Subsequently, the ore-forming fluids gradually evolved from primary magmatic origin to the mixing of meteoric water, as demonstrated by oxygen and hydrogen isotopic values (δ18Ofluid = -1.34 to 6.29 ‰, δD = -112.4 to −76.1 ‰). The δ34S values (-2.92 to 6.52 ‰) and Pb isotopic ratios (208Pb/204Pb = 39.06 to 40.93, 207Pb/204Pb = 15.72 to 15.99, and 206Pb/204Pb = 19.44 to 20.80) suggested a deep magmatic source for the ore-forming fluid, with metals primarily derived from the upper crust, likely associated with the Ladakh Batholith. Fluid boiling and maxing are the dominant mechanisms for ore mineral precipitation. Additionally, the high to moderate temperature and salinity, presence of solid-bearing and vapor rich inclusions, a Co/Ni ratio > 1, the Ni-As-Co diagram, and O-H-S-Pb isotopic evidence collectively support the classification of the Bubin Cu-Pb polymetallic deposit as an intrusion-related porphyry-style magmatic hydrothermal deposit.

Design of low-consumption epoxy resin porous plugging material via emulsification-curing method

Since the higher cost of epoxy resin, its application in reservoir plugging at high temperature and high salinity was seriously restricted. Herein, the expensive epoxy resin was used as the supporting skeleton to provide the mechanical strength required for plugging, while water was introduced via emulsification - curing method in the closed non-connected pores to reduce the material consumption. The curing kinetics of epoxy resin was studied using differential scanning calorimetry (DSC). On this basis, the high temperature stability and dynamic gel time of the epoxy resin emulsion were examined, and the microstructure and mechanical properties of the cured material were tested. Firstly, in the shear rate range of 10–100 s−1, the viscosity of epoxy resin emulsion was less than 1200 mPa·s under the condition of 20 ℃, meanwhile, the viscosity value was less than 100 mPa·s in high temperature environment of the reservoir (120 ℃), which meets the demand of mixing and injection. Secondly, in the W/O emulsion state, the curing reaction rate was accelerated. However, when the curing agent 4,4′-methylenebis[2,6-diethyl]aniline (DTD) is used instead of 3,3′-diethyl-4,4′-diaminodiphenyl methane (DEDDM), utilizing steric effect of double ethyl group, the thickening time is extended from 55 to 60 min to 110–120 min. Finally, after curing the epoxy resin emulsion, although mostly occupied by pore water (fw=50%), the increase in the curing degree made the elastic modulus increase from 0.017 MPa to 3.220 MPa compared with the pure epoxy resin, and the uniaxial compressive strength can reach 25.14 MPa.This design method can reduce the material consumption of epoxy resin by 30–35% while controlling leakage, providing an effective way for the construction of plugging materials in high temperature (120 ℃) and high salinity (21.81 ×104 mg/L) environment.

Bacteriovory of enteric bacteria by soil isolated amoeba depends on both temperature and salinity

Recycling of wastewater for agricultural irrigation is an important means for sustainable reuse practices, but a major concern of such practice is the introduction of pathogens and antibiotic determinants. Previous attempts to mitigate contaminants focused on water treatment, yet the growing appreciation of the soil microbial food web brings into focus its potential to mitigate pathogens introduced by recycled effluent. We hypothesized that effluent-introduced bacteria serve as prey to soil-free living amoeba (FLA), but predation is interfered with by environmental conditions such as temperature and/or salinity. To test our hypothesis, we first demonstrated that an enteric bacterium model, Escherichia coli, is preyed on by soil FLA. We then isolated 12 FLA from three soil types (loamy-sand, loam, and clay) and followed the predation dynamics in three prey types: E. coli, Serratia marsescens, and Enterococcus mundtii. Predation was simulated in an unstructured environment at various temperatures (20, 25, 30 °C), mimicking changing climatic conditions and salinities (2, 10, 30 mM NaCl), mimicking the relative ionic strength and conductivity applied by irrigation effluent. We found that the predation efficiency of the amoeba strains increased significantly increased (p < 0.01) at both low temperature (20 °C) and high salinity (30 mM NaCl) regardless of the types of prey. We suggest that increased salinity applied by effluent irrigation may benefit micropredators, while high temperatures may increase resistance to predation. Our results demonstrate the importance of understanding the effects of environmental conditions on soil trophic interactions and their potential benefits for agricultural practices.

Polyethylene Composite Particles as Novel Water Plugging Agent for High-Temperature and High-Salinity Reservoirs

Water channeling has always been one of the urgent problems during oilfield development. Especially for fractured reservoirs with high temperature, high salinity, and severe heterogeneity (e.g., deep carbonate reservoirs), it is difficult for the existing plugging agents to realize effective water plugging. In this paper, chemically stable polyethylene (PE) was selected as the main component to prepare multiscale PE composite particles that can be easily dispersed in water as a novel water plugging agent for fractured reservoir with high temperature and high salinity. The characteristics of the prepared PE composite particles, including thermal stability, salinity resistance, dispersibility, coalescence properties, and microscopic morphology, were systematically studied. Finally, the plugging performance of the particles was evaluated through visual physical simulation experiments. The prepared PE composite particles can be pulverized to a minimum of 6 μm, and the particle size is controllable within 6 μm to 3 mm by adjusting the pulverization parameters. The PE composite particles are easily dispersed in water by adding the dispersant, which is conducive to injectivity during the field application process. The particle size remains unchanged under the condition of salinity of 0–3.0 × 105 mg/L, which indicates that the prepared particles have good salt-resistant stability. After high-temperature aging, the particles adhere to each other, and the size of the agglomerations reach a size dozens of times larger than the initial size of the particle, which is conducive to effective plugging in fractures. Thermal degradation behavior analysis shows that the PE composite particles could theoretically withstand a temperature of 434.4 °C. It can be seen from the SEM images that after high-temperature melting and kneading with other components, the microstructure changes from a fibrous structure to a dense flake structure. Physical simulation experiments show that the PE composite particles accumulate in fracture after injection and form effective plugging through coalescence and adhesion of the particles, thereby realizing water flow diversion.

Spatial variability in plankton metabolic balance in the tropical Indian Ocean during spring intermonsoon

The tropical Indian Ocean consists of three basins, namely the Arabian Sea (AS), Bay of Bengal (BoB) and Southern Indian Ocean (SIO), with relatively nutrient-rich waters in the former two basins. It is hypothesized that the excess carbon produced in the northern Indian Ocean may support heterotrophic carbon demand in the SIO. In order to test this hypothesis, deck incubation experiments were conducted during the spring intermonsoon under the aegis of the Indian-GEOTRACES program. Nutrients in the mixed layer were low in the SIO compared to AS and BoB due to strong thermal stratification in the former region. Dominant net autotrophy was noticed in the AS whereas net heterotrophy in the BoB and SIO. High community respiration (CR) was observed in the BoB which may be supported by riverine organic carbon, whereas in situ produced and advected excess carbon from the northern Indian Ocean may support in AS and SIO respectively. Net community production (NCP) displayed an inverse (linear) relationship with temperature (salinity) in the euphotic zone in the BoB and SIO suggesting that stratification driven by river discharge and equatorial currents, respectively, reduced nutrients inputs through vertical mixing in the upper ocean resulting in the formation of the strong net heterotrophy and contrast to this was found in the AS due to increase in primary production due to nitrogen fixation. The euphotic zone integrated nutrients displayed a linear relationship with NCP and Gross Primary Production (GPP) indicating that the availability of nutrients controlled the plankton metabolic rates in the tropical Indian Ocean. The threshold of GPP for plankton metabolic balance in the tropical Indian Ocean (1.9 mmol O2 m−3 d−1) was close to that of the global mean (2.2 mmol O2 m−3 d−1). The slope of the log-log relationship between GPP and CR was 0.5 and it is close to that of the global mean value of 0.60.

The Shandong Peninsula as a geographical barrier: Divergence of the bartail flathead Platycephalus indicus resources and associated environmental factors in the Bohai Sea and Yellow Sea

Appropriate resources and environmental conditions are essential for the survival and development of living organisms. The Shandong Peninsula is situated between the Bohai Sea and Yellow Sea, offering a complex geographical environment with rich fisheries. This study aims to explore the divergent impact of the Shandong Peninsula on resource dynamics by analyzing the differences in environmental factors and distribution patterns of an important fishery resource, the bartail flathead Platycephalus indicus, between the Bohai Sea and Yellow Sea. We depicted the spatial driving effects of environmental factors on the bartail flathead resources using the generalized additive model (GAM). The results indicate that the surface temperature, as well as the surface and bottom salinity, of the Yellow Sea, are generally higher than those of the Bohai Sea. Conversely, the bottom temperature and Chlorophyll A concentration of the Bohai Sea are higher than those of the Yellow Sea. A distinct seasonal pattern was illustrated in the surface temperature, bottom temperature, and Chlorophyll A concentration. The surface and bottom temperatures displayed coherence, contrary to the Chlorophyll A concentration, which exhibited an inverse trend to temperature. And the bottom temperature exhibits a two-month delay relative to the surface temperature. The salinity levels at the surface and bottom remained fairly constant over the year. The abundance of bartail flathead varies seasonally and reaches its lowest point in spring. It thrives in the Bohai Sea during summer, while it predominates in the Yellow Sea during winter. In autumn, it is plentiful in both seas, with different distribution centers. The generalized additive model indicates that the optimal distribution area for bartail flathead is located between 120°E and 122°E. Bartail flathead abundance has a significant positive correlation with surface temperature, bottom temperature, and surface salinity, however, it has a significant negative correlation with bottom salinity and Chlorophyll A concentration. Depth does not show any significant correlation with bartail flathead abundance. These findings can serve as the basis for developing measures to protect crucial marine fishery resources and enhance fishery management practices.

Seasonal dynamics of bacterial community and co-occurrence with eukaryotic phytoplankton in the Pearl River Estuary

In this study, we investigated the taxonomic composition of the bacteria and phytoplankton communities in the Pearl River Estuary (PRE) through Illumina sequencing of the V3–V4 region of the 16 S rRNA gene. Furthermore, their relationships as well as recorded environmental variables were explored by co-occurrence networks. Bacterial community composition was different in two size fractions, as well as along the salinity gradient across two seasons. Free-living (FL) communities were dominated by pico-sized Cyanobacteria (Synechococcus CC9902) while Exiguobacterium, Halomonas and Pseudomonas were predominantly associated with particle-associated (PA) lifestyle, and Cyanobium PCC-6307 exhibited seasonal shifts in lifestyles in different seasons. In wet season, bacterial community composition was characterized by abundance of Cyanobacteria, Actinobacteria, and Bacteroidetes, which were tightly linked with high riverine inflow. While in dry season, Proteobacteria increased in prevalence, especially for Psychrobacter, NOR5/OM60 clade and Pseudomonas, which were thrived in lower water temperature and higher salinity. Moreover, we discovered that differences between PA and FL composition were more significant in the wet season than in the dry season, which may be due to better nutritional conditions of particles (indicated by POC%) in the wet season and then attract more diverse PA populations. Based on the analysis of plastidial 16 S rRNA genes, abundant small-sized mixotrophic phytoplankton (Dinophyceae, Euglenida and Haptophyta) were identified in the PRE. The complexity of co-occurrence network increased from FL to PA fractions in both seasons, which suggested that suspended particles can provide ecological niches for particle-associated colonizers contributing to the maintenance of a more stable community structure. In addition, the majority of phytoplankton species exhibited positive co-occurrences with both other phytoplankton species and bacterial counterparts, indicating the mutual cooperation between phytoplankton assemblages and specific bacterial populations e likely benefited from phytoplankton-derived organic compounds. This study enhances our understanding of the seasonal and spatial dynamics of bacterial communities and their potential relationship with phytoplankton assembly in estuarine waters.

Emerging phylogeographic perspective on the toxigenic diatom genus Pseudo-nitzschia in coastal northern European waters and gateways to eastern Arctic seas: Causes, ecological consequences and socio-economic impacts

The diatom Pseudo-nitzschia H. Peragallo is perhaps the most intensively researched genus of marine pennate diatoms, with respect to species diversity, life history strategies, toxigenicity, and biogeographical distribution. The global magnitude and consequences of harmful algal blooms (HABs) of Pseudo-nitzschia are particularly significant because of the high socioeconomic impacts and environmental and human health risks associated with the production of the neurotoxin domoic acid (DA) among populations of many (although not all) species. This has led to enhanced monitoring and mitigation strategies for toxigenic Pseudo-nitzschia blooms and their toxins in recent years. Nevertheless, human adaptive actions based on future scenarios of bloom dynamics and proposed shifts in biogeographical distribution under climate-change regimes have not been implemented on a regional scale. In the CoCliME (Co-development of climate services for adaptation to changing marine ecosystems) program these issues were addressed with respect to past, current and anticipated future status of key HAB genera such as Pseudo-nitzschia and expected benefits of enhanced monitoring. Data on the distribution and frequency of Pseudo-nitzschia blooms in relation to DA occurrence and associated amnesic shellfish toxin (AST) events were evaluated in a contemporary and historical context over the past several decades from key northern CoCliME Case Study areas. The regional studies comprised the greater North Sea and adjacent Kattegat-Skagerrak and Norwegian Sea, eastern North Atlantic marginal seas and Arctic gateways, and the Baltic Sea. The first evidence of possible biogeographical expansion of Pseudo-nitzschia taxa into frontier eastern Arctic gateways was provided from DNA barcoding signatures. Key climate change indicators, such as salinity, temperature, and water-column stratification were identified as drivers of upwelling and advection related to the distribution of regional Pseudo-nitzschia blooms. The possible influence of changing variables on bloom dynamics, magnitude, frequency and spatial and temporal distribution were interpreted in the context of regional ocean climate models. These climate change indicators may play key roles in selecting for the occurrence and diversity of Pseudo-nitzschia species within the broader microeukaryote communities. Shifts to higher temperature and lower salinity regimes predicted for the southern North Sea indicate the potential for high-magnitude Pseudo-nitzschia blooms, currently absent from this area. Ecological and socioeconomic impacts of Pseudo-nitzschia blooms are evaluated with reference to effects on fisheries and mariculture resources and coastal ecosystem function. Where feasible, effective adaptation strategies are proposed herein as emerging climate services for the northern CoCLiME region.

Advancing ocean subsurface thermal structure estimation in the Pacific Ocean: A multi-model ensemble machine learning approach

Estimation of the ocean subsurface thermal structure (OSTS) is important for understanding thermodynamic processes and climate variability. In the present study, a novel multi-model ensemble machine learning (Ensemble-ML) model is developed to retrieve subsurface thermal structure in the Pacific Ocean by integrating sea surface data with Argo observations. The Ensemble-ML model integrates four individual machine learning models to enhance estimation accuracy and reliability. Our results exhibit good agreement between the satellite sea surface temperature (SST) and sea surface salinity (SSS) data and Argo observations, providing validation for the utilization of these datasets in the Ensemble-ML model. The Ensemble-ML model exhibits better performance compared to individual machine learning models, with an average root mean square error (RMSE) of 0.3273 °C and an average coefficient of determination (R²) of 0.9905. Notably, incorporating geographical information as input variables enhance model performance, emphasizing the importance of considering spatial context in OSTS estimation. The Ensemble-ML model accurately captures the spatial distribution of OSTS across depths and seasons in the Pacific Ocean, effectively reproducing critical temperature features while maintaining strong agreement with Argo observations. Nevertheless, its performance shows relative weakness within the thermocline layer and the equatorial Pacific region (spanning from 10°S to 10°N latitude), which are characterized by complex circulation systems. Despite these challenges, the Ensemble-ML model effectively reproduces the spatial distribution of OSTS of the Pacific Ocean. This indicates the potential of machine learning models, particularly ensemble models, for enhancing OSTS estimation in the Pacific Ocean and other regions, offering valuable insights for future research and applications in physical oceanography.

Analysis of Ocean–Lithosphere–Atmosphere–Ionosphere Coupling Related to Two Strong Earthquakes Occurring in June–September 2022 on the Sea Coast of Philippines and Papua New Guinea

Scientific progress in the context of seismic precursors reveals a systematic mechanism, namely lithosphere–atmosphere–ionosphere coupling (LAIC), to elaborate the underlying physical processes related to earthquake preparation phases. In this study, a comprehensive analysis was conducted for two earthquakes that occurred on the sea coast through tidal force fluctuation to investigate ocean–lithosphere–atmosphere–ionosphere coupling (OLAIC), based on oceanic parameters (i.e., sea potential temperature and seawater salinity), air temperature and electron density profiles. The interrupted enhancement and diffusion process of thermal anomalies indicate that the intensity of seismic anomalies in the atmosphere is affected by the extent of land near the epicenter. By observing the evolution of the ocean interior, we found that the deep water was lifted and formed upwelling, which then diffused along the direction of plate boundaries with an “intensification-peak-weakening” trend under the action of the accelerated subduction of tectonic plates. Furthermore, the analysis shows that the seismic anomalies have two propagation paths: (i) along active faults, with the surface temperature rising as the initial performance, then the air pressure gradient being generated, and finally the ionosphere being disturbed; (ii) along plate boundaries, upwelling, which is the initial manifestation, leading to changes in the parameters of the upper ocean. The results presented in this study can contribute to understanding the intrinsic characteristics of OLAIC.

Numerical Simulation Calculation of Thermal Discharge Water Diffusion in Coastal Nuclear Power Plants

Coastal areas have become the primary location for nuclear power plant sites due to the convenience of seawater cooling. In China, the diffusion range of thermal discharge water has always been a hot research topic as the basis for sea use areas. The main physical process of heat loss in the numerical simulation of thermal discharge from power plants is heat exchange between the water surface and air. Currently, the methods for calculating this heat loss include the heat flux method and the water surface heat exchange coefficient method. Taking a power plant in Zhejiang as the research object, the MIKE 3 temperature–salinity module (heat flux method) and MIKE ECO Model (water surface heat exchange coefficient method) were used for modeling, and the diffusion of thermal discharge water under different modules was compared and analyzed. The results show that the calculated area of the water temperature rise envelope between the two modules differed significantly under the same conditions. The surface 4 °C temperature rise area, as calculated using ECO Model, was 45.8% smaller than that of the temperature–salinity module. The MIKE 3 temperature–salinity module can simulate the heat accumulation of water under thermal buoyancy, producing a significant thermal stratification phenomenon; the ECO module does not accurately represent the heat exchange process between the water surface and the air, and it does not adequately capture the significant vertical stratification that occurs in real-world scenarios. On this basis, this study not only lays a foundation for further exploring the impact of thermal discharge water from this powerhouse on the structure of surrounding marine biological communities and dissolved oxygen content in water bodies but also provides scientific evidence for the selection of modules when simulating thermal discharge water with the MIKE model.

Synthesis of a network‐structured polymer with low viscosity effect and its use as filtrate reducer for water‐based drilling fluids

AbstractWith the development of deep formations, high temperature and high salinity seriously affect the rheology and filtration performance of water‐based drilling fluids. Therefore, in this study, a network‐structured polymer (DSD‐β‐CD) with low viscosity effect was synthesized using β‐cyclodextrin (β‐CD) as the backbone and N,N‐dimethylacrylamide (DMAA), sodium p‐styrene sulfonate (SSS), and dimethyl diallyl ammonium chloride (DMDAAC) as monomers. The polymer was analyzed by transmission electron microscope, Fourier transform infrared spectrum, nuclear magnetic resonance, and thermogravimetric analysis. The filtrate reducer in this study showed excellent temperature and salt resistance, the filtration loss of the water‐based drilling fluid containing 3.5% DSD‐β‐CD and 18% NaCl was 5.1 mL after hot rolling at 220°C for 16 h. Additionally, its viscosity was 0.2 mPa s higher than that of the water‐based drilling fluid with 18% NaCl, showing an excellent low viscosity effect. The filtration loss reduction mechanism of DSD‐β‐CD was investigated by viscosity analysis, mud cake analysis, particle size distribution, hydration swelling of bentonite, and Zeta potential. The results showed that DSD‐β‐CD could be adsorbed on the surface of bentonite particles through hydrogen bonds and ionic bonds, which increased the dispersion of bentonite particle and the compactness of the mud cake, thus reducing the filtration loss.

Effect of Temperature and Water Salinity on Electrical Surface Conduction of Clay Particles

In this study, the combined effect of temperature (T) and pore water salinity on electrical surface conduction parameters was investigated. Two new electrical surface conduction parameters, namely, electrical conductivity of effective solid (σs) and size of diffuse double layer (DDL) water per unit volume of soil (χ), were considered in this study. The tested samples included two commercially available clays and four natural clay soils with diverse physico-chemical properties. The two surface conduction parameters were also used to assess the influence of temperature (T) and pore water salinity, as well as the electrical conductivity of free water (σFW), on the evolution of the free swelling index (FSI) of clays/clay soils through experimental methods. The findings suggested that elevated temperature and σFW increased σs but reduced χ, as well as the FSI of clays/clay soils. Furthermore, the rate of reduction for both χ and FSI augmented under the influence of increased free water salinity, particularly for clays/clay soils with high swelling capacity. The combined reductions of χ and FSI provided substantial evidence that clay DDL thickness decreases as T and σFW increase concurrently.

A novel profile modification HPF-Co gel satisfied with fractured low permeability reservoirs in high temperature and high salinity

Conformance control and water plugging are a widely used EOR method in mature oilfields. However, majority of conformance control and water plugging agents are unavoidable dehydrated situation in high-temperature and high-salinity low permeability reservoirs. Consequently, a novel conformance control system HPF-Co gel, based on high-temperature stabilizer (CoCl2·H2O, CCH) is developed. The HPF-Co bulk gel has better performances with high temperature (120 °C) and high salinity (1×105 mg/L). According to Sydansk coding system, the gel strength of HPF-Co with CCH is increased to code G. The dehydration rate of HPF-Co gel is 32.0% after aging for 150 d at 120 °C, showing excellent thermal stability. The rheological properties of HPF gel and HPF-Co gel are also studied. The results show that the storage modulus (G′) of HPF-Co gel is always greater than that of HPF gel. The effect of CCH on the microstructure of the gel is studied. The results show that the HPF-Co gel with CCH has a denser gel network, and the diameter of the three-dimensional network skeleton is 1.5–3.5 μm. After 90 d of aging, HPF-Co gel still has a good three-dimensional structure. Infrared spectroscopy results show that CCH forms coordination bonds with N and O atoms in the gel amide group, which can suppress the vibration of cross-linked sites and improve the stability at high temperature. Fractured core plugging test determines the optimized polymer gel injection strategy and injection velocity with HPF-Co bulk gel system, plugging rate exceeding 98%. Moreover, the results of subsequent waterflooding recovery can be improved by 17%.