Strength Of Seawater Research Articles

Effects of salinity on glycerol conversion and biological phosphorus removal by aerobic granular sludge

Industrial wastewater often has high levels of salt, either due to seawater or e.g. sodium chloride (NaCl) usage in the processing. Previous work indicated that aerobic granular sludge (AGS) is differently affected by seawater or saline water at similar osmotic strength. Here we investigate in more detail the impact of NaCl concentrations and seawater on the granulation and conversion processes for AGS wastewater treatment. Glycerol was used as the carbon source since it is regularly present in industrial wastewaters, and to allow the evaluation of microbial interactions that better reflect real conditions. Long-term experiments were performed to evaluate and compare the effect of salinity on granulation, anaerobic conversions, phosphate removal, and the microbial community. Smooth and stable granules as well as enhanced biological phosphorus removal (EBPR) were achieved up to 20 g/L NaCl or when using seawater. However, at NaCl levels comparable to seawater strength (30 g/L) incomplete anaerobic glycerol uptake and aerobic phosphate uptake were observed, the effluent turbidity increased, and filamentous granules began to appear. The latter is likely due to the direct aerobic growth on the leftover substrate after the anaerobic feeding period. In all reactor conditions, except the reactor with 30 g/L NaCl, Ca. Accumulibacter was the dominant microorganism. In the reactor with 30 g/L NaCl, the relative abundance of Ca. Accumulibacter decreased to ≤1 % and an increase in the genus Zoogloea was observed. Throughout all reactor conditions, Tessaracoccus and Micropruina, both actinobacteria, were present which were likely responsible for the anaerobic conversion of glycerol into volatile fatty acids. None of the glycerol metabolizing proteins were detected in Ca. Accumulibacter which supports previous findings that glycerol can not be directly utilized by Ca. Accumulibacter. The proteome profile of the dominant taxa was analysed and the results are further discussed. The exposure of salt-adapted biomass to hypo-osmotic conditions led to significant trehalose and PO43−-P release which can be related to the osmoregulation of the cells. Overall, this study provides insights into the effect of salt on the operation and stability of the EBPR and AGS processes. The findings suggest that maintaining a balanced cation ratio is likely to be more important for the operational stability of EBPR and AGS systems than absolute salt concentrations.

TEMPO-oxidized cellulose nanofiber reinforced starch film with pH-responsive weakening and rapid marine-degradability

Self-standing films made of starch are a promising material for single-use packaging owing to their higher abundancy, degradability, and economical processability. However, weak mechanical strength and poor freshwater durability restricted their application. Our previous research demonstrated that blending TEMPO-oxidized cellulose nanofiber (TCNF) with modified starch enhances mechanical strength and freshwater durability through hemiacetal bonding. In this study, we demonstrated pH-responsive weakening in seawater and rapid marine-microbial degradability of TCNF reinforced modified starch films. The TCNF was blended with hydroxypropyl starch (HPS) and di-aldehyde starch (aldS) to develop the films. pH-responsive swelling and weakening were performed in freshwater and seawater with a variable pH from 4 to 9. Moreover, marine microbial degradability was evaluated in artificial marine environment. TCNF/modified starch film rapidly lost up to 80 % of its strength in seawater and has shown higher marine microbial growth and degradability compared to neat TCNF film. The TCNF/HPS film demonstrated the ideal behavior of both pH-responsive weakening with adequate microbial degradability. Therefore, it has the potential to become the next-generation packaging material to help address the problem of floating debris.

Reactive Transport Modelling of carbon mineralization – a machine learning-based approach

Carbon mineralisation is currently one of the most promising Carbon Capture and Storage (CSS) options for permanent gas sequestration since it ensures a rapid conversion of carbon from the gas phase to a carbonate mineral. Mafic and ultramafic rocks are the best geological options for mineral carbonation due to the relatively fast dissolution rates of the mineral components that can release carbonatable divalent cations such as Mg2+, Sr2+, Ba2+, Mn2+, Ca2+ and Fe2+. Once in solution, these cations react with dissolved carbonate ions to form, under convenient pH and temperature conditions, carbonate minerals like calcite, magnesite, siderite, rhodochrosite, or dolomite.
 The viability of carbon mineralization with injection of freshwater has been proven in the CarbFix project [1]. The main feature of the CarbFix method is that CO2 (and other minor gases) is not injected under its gaseous form but already dissolved in an aqueous fluid, which greatly enhances the mineralisation rates. The methodology, however, requires vast amounts of water that can be a limited resource in many regions. Seawater may be the most viable water source for underground carbonation in many areas, but its use raises questions on the efficiency of the carbonation process. The high ionic strength of seawater makes the geochemical interactions between CO2-rock and seawater more complex and, so far, more unpredictable. Reactive transport modelling (RTM) based on experimental thermodynamic and kinetic data of seawater-basalt interaction [2, 3] can shed some light on the expected mineralisation progress in sites with different mineralogy and variable temperature conditions. Figure 1 shows the results obtained with a reactive transport model that simulates the injection of CO2-charged seawater in basaltic rock.
 geochemical reaction calculations in particular might be considerably slow and are sometimes redundant as they might be based on a very similar set of input values. These challenges are usually faced by introducing a number of simplifications in the models to meet the objectives of the simulation studies. Thus, alternative ways to solving the full system are a priori a potential way to reduce the computational burden of numerical models.
 One of such alternatives is Machine Learning (ML) and, more specifically, Artificial Neural Networks (ANN), which are inspired on biological neural networks as the ones found in the human brain. They contain several computational “neurons” arranged in different layers. Each of these neurons can be activated based on the response of the other connected neurons. The training process consists of feeding data into the ANN and fitting the connection weights between the neurons to reproduce and learn the hidden relationships of the data. Recently, the authors have coupled ANNs of a geochemical system into a reactive transport simulator [5]. In this approach, Supervised Machine Learning with ANNs is used to accurately predict the geochemical evolution in a reactive transport framework without the need of actually performing the (expensive) chemical equilibrium calculations in the reactive transport model.
 The goal of this work is to apply and further develop the technology based on Supervised Machine Learning algorithms to drastically boost the efficiency of reactive transport models of carbon mineralization in the Carbfix system [6]. Firstly, a set of geochemical models of CCS are developed in batch systems (0D) as well as reactive transport models in 1D axisymmetric, 2D, and 3D RTM modelling with different degrees of complexity. Modelling focuses on the injection of CO2-charged seawater into basaltic rocks. In this system, CO2 is consumed via a two-step reaction: (1) Dissolution of Basaltic Glass and release of cations (Ca and Mg), and (2) precipitation of Ca-Mg carbonates and other secondary minerals. The RTM models consider a 1 km domain and a characteristic mineralization of 3-4 years. As a first step, these models are solved with the convential (non ML-based) reactive transport simulator iCP [7]. Then, ANNs are trained and validated with the latest developments in setting up neural networks and used to solve these RTM systems with a Comsol-ML library. The resulting ANNs present good accuracies with coefficients of determination (R2) above 0.95 for all outputs, and a batch calculation speedup of 30 as compared to traditional chemical equilibration with PhreeqC. Preliminary results of RTM using ML to predict the chemical step indicate a speedup of on order of magnitude and reasonable accuracy as compared to conventional RTM. Our results demonstrate that it is conceivable to replace a geochemical solver in a RTM environment with significantly faster surrogate-based models powered by a machine learning algorithm

Non-targeted metabolomic evaluations during seed germination and seedling growth in Salicornia brachiata (Roxb.) under saline conditions

Experimental studies were conducted for metabolomic profiling during seed germination and seedling development in Salicornia brachaita under saline conditions. The results revealed accumulation of sucrose, mannose, glycerol, methionine, tryptophan, glycerol, protocathechoic acid, and mannonic acid in germinating seeds. Abundance of rhamnose, glucose, glutamine, fructose, ornithine, quininic acid, proline and ketoglutaric acid were recorded during emergence of radical (EoR) and cotyledonary stage (CS) at 50% strength of seawater (SW) salinity. Higher levels of myo-inositol, ethanolamine, isoleucine and talose at 48 hours (hrs) of imbibition, EoR and CS stages; while glycine, tyrosine and turanose were so at CS stage only. Under 200 mM NaCl, richness of stearic acid, quercetin, leucine, erythritol and psicose were noted at 48 hrs of imbibition followed by EoR stage. Fructose, ornithine, mannitol, asparagine, mallic acid, glucose and citric acid were abundant at EoR whereas aminobutanoic acid, hexanedioic acid and tyramine were so at CS stage. Among detected metabolites maximum number of metabolites showed hits with amioacyl-tRNA biosynthesis pathway and the amino acid biosynthesis pathway had maximum impact during seedling development. Role of metabolic pathways (including amino acid metabolism) and differential expression of genes related to these pathways are suggested in meeting the energy needs for varied biological activities during seed germination and subsequent seedling development in S. brachiata.

Interaction of Silica Nanoparticles with Microalgal Extracellular Polymers

The properties of engineered nanoparticles (NPs) in the marine environment are influenced not only by the high ionic strength of seawater but also by the interaction of NPs with naturally occurring components of seawater, especially natural organic matter. The aim of this study was to investigate the interaction of engineered silica nanoparticles (SiO2 NPs, diameter of 12 nm) with microalgal extracellular polymers (EPS) released by the marine diatom Cylindrotheca closterium. Dissolved organic carbon (DOC) content of the prepared EPS suspension (200 μg mL−1) used throughout the study was 3.44 mg C L−1. The incorporation of individual SiO2 NPs (height range 10–15 nm) and their nanoscale aggregates (height up to 25 nm, length up to 600 nm) into the EPS network was visualized by atomic force microscopy (AFM), whereas their molecular-level interaction was unraveled by the change in the signal of the Si-O group in their FTIR spectra. AFM imaging of C. closterium cells taken directly from the culture spiked with SiO2 NPs (10 μg mL−1) revealed that the latter are bound to the EPS released around the cells, predominantly as single NPs (height range 10–15 nm). Since AFM and dynamic and electrophoretic light scattering results demonstrated that SiO2 NPs dispersed in seawater without EPS showed enhanced aggregation (aggregate diameter of 990 ± 170 nm) and a 2.7-fold lower absolute zeta potential value compared to that measured in ultrapure water, our findings suggest that the presence of EPS biopolymers alters the aggregation affinity of SiO2 NPs in the marine environment. This might be of outmost importance during microalgal blooms when increased EPS production is expected because EPS, by scavenging and stabilizing SiO2 NPs, could prolong the presence of NPs in the water column and pose a threat to marine biota.

Role of salinity concomitant with asphaltene and resin on the interfacial tension of ionic liquid from imidazolium family

Imidazolium-based ionic liquids have been considered environmentally friendly surfactants with display high performance in the interfacial tension (IFT) reduction. On the other hand, adjusting/tuning ions composition of the aqueous media (such as SO4−, Ca2+, and Mg2+) is an important feature in the smart water-enhanced oil recovery process. Since oil composition (particularly asphaltene and rein fractions) demonstrates the remarkable impact on the interfacial behavior of crude oil/aqueous solution, the synergetic effect between [C12mim][Cl] IL and active ions in the seawater on the IFT of various synthetic oils were evaluated. The structural properties of asphaltene and resin fraction of two crude oil with API gravity of 32.3 (oil A) and 27.5 (oil B) (through preparing six synthetic oils) and tuning ion composition (through preparing five aqueous media) at an ionic strength of seawater (IS = 0.8 M) on the performance of the IL were evaluated. The results showed a lower IFT value of synthetic oils prepared by oil A than those prepared by oil B in the presence of all studied electrolyte solutions, due to the presence of more polar heteroatoms in the structure of asphaltene and resin extracted from oil A, indicates the dominant effect of the nature of oil type on the [C12mim]Cl surface activity compared to the effect of ion type (composition of brine).

Polyphenols extraction kinetics from Ascophyllum nodosum seaweed employing water and saltwater: Effect of ultrasound sonication

Saltwater (S), with the same ionic strength of seawater, was employed as solvent to extract polyphenols from seaweeds. Aqueous extracts were chemically characterized by means of total polyphenols (TPC), carbohydrates (CHOS) and uronic acids (UA) content and antioxidant capacities (DPPH, ABTS and FRAP). S-extracts showed lower TPC than those obtained with distilled water (D) using two different extraction methods, conventional solid-liquid extraction (SLE) and ultrasound-assisted extraction (UAE). The antioxidant capacities of both non-sonicated extracts did not show significant (p < 0.05) differences. SLE kinetics employing both solvents (D and S) were successfully modelled by Peleg's model, and equilibria were achieved after 15 min. Long-time UAE (15 min) increased phytochemical content in both D- and S-extracts with respect to SLE. Extracts showed three main (A, B, and C) regions from RP-HPLC profiles with different peak areas and shapes. Normalized regions areas from RP-HPLC were related to antioxidant activities by linear regressions and showed that B-region was the main responsible of phytochemical features of the extracts. SLE with saltwater promoted the leaching of other compounds (mainly proteins) that formed intermolecular complexes. These interactions were notoriously diminished with UAE. At these conditions, saltwater can be employed as eco-friendly solvent according to the green chemistry principles.

Vaterite production and particle size and shape control using seawater as an indirect carbonation solvent

Vaterite, a type of calcium carbonate, has recently raised the potential for use as a drug delivery material and a filler for bone defects due to its high specific surface area and solubility, low specific gravity, and high porosity. However, existing methods of producing fine-particle vaterite exhibit limitations that annexed processes such as adding excessive additives or irradiating ultrasound are necessary, and mass production is impossible. We developed a simple, chemical additive-free, low-cost technology with mass production capability that can overcome problems faced in conventional vaterite production. We found that seawater is favorable for vaterite production and enables the reduction of its particle size because of its supersaturation in CaCO3, absence of magnesium, and high viscosity, and the reduced surface energy of vaterite. Using seawater as a solvent for indirect carbonation, we succeeded in producing a vaterite content of 100% containing fine particles without additives or additional processing. Spherical or elliptical vaterite was separately formed by adjusting the ionic strength of seawater. In addition, the ionic strength of seawater controlled the surface area and pore size of vaterite.

Adhesion shear strength test method for freshwater/seawater ice on carbon ceramic brake pads of amphibious aircraft

PurposeBased on the mechanical model of typical shear tests, this study aims to propose the test principle and method of freshwater/seawater ice adhesion shear strength of carbon ceramic brake pads for amphibious aircraft, designs and builds the test equipment, prepares the freshwater/seawater ice samples and completes the tests.Design/methodology/approachThis study examines the influence of the icing process, mechanism, temperature and freshwater/seawater on ice adhesion shear strength of carbon ceramic brake pads and puts forward a test method for the freshwater/seawater ice adhesion shear strength of amphibious aircraft brake pads.FindingsThe obtained results examine the influence of the icing process, mechanism, temperature and freshwater/seawater on ice adhesion shear strength of carbon ceramic brake pads. The adhesion shear strength of frozen freshwater and of the seawater of Dalian, Qingdao, Fuzhou and Zhuhai on the surface of aircraft brake pads is measured at –10 to –50°C. It is found that the shear strength of freshwater increases first and then decreases with the decrease of temperature. The adhesion shear strength of seawater; however, increases mainly linear with the decrease of temperature.Originality/valueThe value of this paper is that the test method proposed and test results for the freshwater/seawater ice adhesion shear strength of amphibious aircraft brake pads provide technical support for the anti-icing design of amphibious aircraft brake devices.

Speciation of yttrium and the rare earth elements in seawater: Review of a 20-year analytical journey

This review describes a program that we have conducted for more than 20 years, first at the University of South Florida and then at the University of Maryland Center for Environmental Science, to systematically measure stability constants for solution complexes of yttrium and all rare earth elements (YREE), except Pm, at the ionic strength of seawater (I ~ 0.7). This effort informs our goal of better characterizing and understanding YREE speciation in the marine environment, in the presence of both inorganic and organic ligands (and sorbents). Since all YREE appear to show similar behavior as a function of ionic strength, patterns of stability constants for individual ligands have been extrapolated to I = 0 whenever sufficient data for at least one member of the series are available. Complexes with hydroxide, fluoride and chloride, carbonate, and sulfate, are treated in detail, being the most prominent inorganic YREE ligands. A natural siderophore (DFOB) and synthetic polyaminopolycarboxylic acids (NTA, EDTA, DTPA) are given as examples of strong organic YREE complexation which, while remaining poorly quantified, is thought to be important. Several YREE ligands that play a negligible role in seawater, or for which data are as yet scarce, are also briefly discussed. Many different and sometimes novel analytical approaches were used in our experiments and these are summarized in the introductory sections, along with a primer on the theory of chemical speciation. This paper is intended as a retrospective of our work, not as a critical review of all available data. Literature values are thus cited primarily for comparison with our results, to support specific arguments, or to highlight prior discrepancies that prompted our own studies.

Study of the influence of seawater and sea sand on the mechanical and microstructural properties of concrete

With the continuous increase of infrastructural construction worldwide, the supply of river sand and fresh water for making concrete encountered enormous shortage, especially for coastal regions. To alleviate this problem, researchers have started to investigate the possibility of consuming seawater and sea sand as alternatives. This paper reports the results of a comprehensive study on the mechanical and microstructural properties of seawater and sea sand concrete. Three types of concrete: seawater and sea sand concrete (SSC), sea sand concrete (SC), and ordinary concrete (OC), were prepared following two different water/binder ratio. Compressive strength, flexural strength, dynamic modulus of elasticity, and stress-strain relationship as well as microstructural analysis of all the concrete types were investigated. It was observed that the use of seawater and sea sand has led to an increase of the early age compressive strength but slightly decrease of the 28 days strength. The flexural strength of seawater and sea sand concrete, sea sand concrete has been ameliorated at 28 days, when compared, to ordinary concrete. The dynamic modulus of elasticity of concrete made with either seawater and sea sand or sea sand has been significantly enhanced, especially at the early age. X-ray diffraction pattern (XRD) and scanning electron microscopy (SEM) analyses further confirmed that sea sand and seawater have a remarkable effect on the surface morphology and the significant contrast from ordinary concrete due to the dominance of the ettringite phase with crystals that have a fibrous shape, which leads to a compacted and less porous structure and enhancement of the mechanical behavior.

Photosynthetic Gas Exchange and Chlorophyll a Fluorescence in Salicornia brachiata (Roxb.) Under Osmotic Stress

Osmotic stress negatively affects the photosynthetic efficiency and cause a significant loss of crop productivity. Salicornia brachiata (Roxb.) is a eu-halophyte. We hereby report on photosynthetic gas exchange and chlorophyll fluorescence in S. brachiata under sodium chloride (NaCl), seawater and polyethylene glycol (PEG) induced osmotic stress. It grows luxuriantly and exhibited a higher tolerance index and better accumulation of organic solutes under 100% strength of seawater (32.5 ppt) and 0.5 M NaCl salinity. It exhibited comparatively better gas exchange, stomatal conductance, PSII photochemistry and electron transfer under 100% strength of seawater salinity. Higher chlorophyll a/b ratio under stress conditions indicated a lower ratio of PSII to PSI and balanced excitation of PSI and PSII in S. brachiata resulting in efficient photosynthetic processes. The lower total chlorophyll/carotenoids ratio and higher non-photochemical quenching indicated the photo-protection and safer dissipation of heat energy in S. brachiata under stress. The 100% strength of seawater and 0.5 M NaCl salinity in S. brachiata did not cause significant changes in antenna size, connectivity between PSII reaction centres (RCs) and reduction of electrons on PSII donor side. The 20% PEG induced the inactivation of RCs and cause damage to PSII RCs in S. brachiata thus reduced the electron transfer from QA– to QB pool-sized and activity of water-splitting complex. Higher φ(P0) and FV/FM in S. brachiata under seawater salinity indicated a comparatively better quantum yield of primary photochemistry. The higher PITotal in S. brachiata under 100% strength of seawater and 0.5 M NaCl stress indicated a better energy flux reaching to PSII RCs, electron transport and performance of RCs. The higher strengths of osmotic stress cause reduction in the quantum yield of PSII electron transport and capturing efficiency of excitation energy by open PSII RCs in S. brachiata.

Surface free energies parameters in carbonate rock/nonacidic crude oil/brines systems

ABSTRACT Since knowing the effect of salt type is a vital parameter during smart-water injection for enhanced oil recovery (EOR) purposes, surface-free energies on the carbonate surface contacted by crude oil and different aqueous solutions with 0.7 ionic strength (about the ionic strength of seawater) are studied for solutions containing NaCl, Na2SO4, KCl, CaCl2, MgCl2, and MgSO4. For this purpose, the interfacial tension (IFT) of crude oil/aqueous solution and contact angle of oil/rock/brine are measured concomitant with the calculation of works of cohesion (WC) and adhesion (WA) as well as spreading coefficient (SC). Maximum equilibrium IFT reduction was observed for MgSO4 (from 22.7 to 12.71 mN.m−1). Besides, the calculated adsorption times using the exponential decay model reveal that the chloride salts of MgCl2 and KCl has the minimum and maximum adsorption time of 1600 s and 3400 s, respectively. Moreover, the contact angle measurements demonstrate that it is possible to change the wettability condition of rock surface from strongly oil-wet to strongly water-wet (about 20°) using Na2SO4 while the other utilized salts can change the contact angle from 170° to neutral wetness condition of 100°. The obtained results show that the best SC was obtained for DW due to its significant wettability alteration capability (from strongly oil-wet toward neutral state) compared with brine solutions. To sum up, according to the results it can be concluded that solution congaing MgSO4 can introduce the lowest IFT value and the highest wettability alteration from the initial strongly oil-wet state toward a neutral state, while Na2SO4 solution leading the lowest contact angle of about 20° which is the most favorable condition (strongly water-wet).

Seed germination, seedling growth and seedling development associated physiochemical changes in Salicornia brachiata (Roxb.) under salinity and osmotic stress

Salicornia brachiata (Roxb.) exhibits seed germination and grows luxuriantly under extremely saline conditions. We hereby report seed germination potential, seedling growth and seedling development associated physiochemical changes in S. brachiata. Seawater above 75 % strength, NaCl above 400 mM and PEG above 20 % reduced seed germination by 50 % in S. brachiata. Germination energy, coefficient of velocity of germination, relative salt injury, and different germination indexes decreased with stress strength. NaCl at 1000 mM and PEG at 40 % completely inhibited seed germination in S. brachiata. In recovery studies, 100 % seeds germinated once the inhibitory stress was removed. S. brachiata exhibited a significantly higher seed vigor index under 75 % strength of seawater and 200 mM NaCl. Malondialdehyde accumulation during seedling development was in accordance with the accumulation of reactive oxygen species (ROS). Sugar, free amino acid, and proline contents varied with seedling development and type of stress. Higher accumulation of polyphenols and flavonoids during seedling development helped to reduce the ROS accumulation. Accumulation of inorganic ions varied and S. brachiata maintained the ratio of K+/Na+ once the seedling is established. S. brachiata exhibited comparatively higher activity of the studied cell wall hydrolases, which helped to maintain hydration and elasticity of cell wall during seed germination and seedling development. Differentially higher activity of superoxide dismutase, guaiacol peroxidase and glutathione oxidase during seedling development under stress conditions helped to reduce the ROS accumulation. The results indicated that among stress solutions of similar osmolarity, maximum inhibition was observed in the seawater and it was followed by NaCl and PEG at seed germination stage.

Effect of drilling fluid on concrete-soil/rock interface shear strength in seawater drilling environment

In this article, the results of an experimental study on the effect of drilling fluid on concrete-soil/rock interface shear strength in the seawater drilling environment are presented. The series of direct shear tests using a purpose-designed shear box with seawater were performed considering different types of drilling fluid and base material, various normal stress levels at the interface, and filtration times. The results indicated that bentonite drilling fluid significantly decreased the concrete-soil/rock interface shear strength while a negligibly small effect was observed for polymer drilling fluid, confirming the findings from the previous studies. It was also observed that the degree of interface shear strength reduction when using bentonite drilling fluid varied with the type of base material as well as the level of normal stress at the interface. The results also confirmed that the groundwater chemistry does not alter governing mechanism of the drilling fluids and the concrete-soil/rock interface interaction and that significant benefit can also be expected when using polymer-based drilling fluid over bentonite in terms of the side resistance of a drilled shaft in seawater drilling environment as well.

PENGARUH AIR PDAM, LAUT, COMBERAN PADA PROSES CURING TERHADAP KUAT TEKAN BETON Fc 14,53 Mpa

Concrete is a mixture of concrete forming materials, namely: fine aggregate, coarse aggregate, cement, and water. Each concrete construction always be able to show its function, ie strength and endurance during the planned life. Therefore, in this research concrete treatment is known to increase the concrete but also need to know how long the concrete treatment is good Only requires water from the loss of water experienced. Thus the research is conducted to find out how much the influence of curing process uses sea water, PDAM sewage toward to the strength of concrete press. This research was conducted with the use of 3 types of water that is water PDAM, sea water, sewage. Cylindrical tests specimen with diameter 15 cm and height 30 cm. Each sample is made of 3 specimens by the age of 7 days. The value of compressive strength in PDAM water, seawater, sewage successively at the age of 7 days is 13,522 MPa, 8,759 MPa, 10,296 MPa. The value of compressive strength of Water PDAM at 7 days has increased compared to the compressive strength value of seawater and sewage, while the value of compressive strength of seawater has decreased compared to the rising sewage. So it can be concluded that the value of the highest compressive strength is water PDAM at the age of 7 days.

Effect of seawater intrusion on radioactive strontium (90Sr) sorption and transport at nuclear power plants

Abstract Batch sorption and column experiments were conducted to investigate and compare sorption and transport behavior of 90Sr on the assumption of seawater intrusion at nuclear power plants. Batch sorption experiments were carried out on fractured rocks and bedrocks using synthetic groundwater and seawater both spiked with 90Sr. In general, higher 90Sr sorption occurred on fractured rock samples than on bedrocks, because of the presence of weathered secondary minerals (iron oxide and clay) on fractured rock surfaces. However, one particular bedrock sample (WSP-B) which has higher porosity and carbon amount than fractured rock samples also showed the higher 90Sr sorption than its comparable fractured rocks. For all batch sorption studies, 90Sr sorption distribution coefficient, K d decreased from groundwater to seawater environment due to the higher ionic strength of seawater (6.4×10−1–7.7×10−1 M) compared to groundwater (4.0×10−3–6.0×10−3 M). The three different ionic strength solutions were used in column experiments, and the results showed that transport behavior of Sr through a fractured rock had similar sorption trend to batch sorption results. The highest mobility (or least retardation) for Sr was found for 100% seawater solution compared to the highest retardation (or least mobility) for 100% groundwater solution. These sorption and transport data of Sr on solid materials contacted with various ionic strength solutions corroborate empirically defensible information for assessment of radioactive contamination in groundwater below the NPP sites located nearby shores. In addition, the experimental data will be incorporated to improve transport models of 90Sr in the subsurface environment for severe nuclear accidents.

Hormosira banksii (Phaeophyceae): a tough survivor in the harsh conditions of high intertidal pools in southeast Australia

Hormosira banksii, the most successful intertidal fucoid in the southern hemisphere, usually inhabits only the lower shore. On Kainga Reef, at 36°S on the New South Wales coast, it is one of only two macroalgae in most of the pools on a platform above xthe lowest high water; 29 pools in the middle of the platform were monitored photographically for 12 years. Recruitment was not seasonal. It took about 5–8 months for germlings to become visible, when they consisted of about 3 vesicles. The growth rate of germlings was between linear and exponential. Individuals could become fertile when they were 11–14 months old. Adult frond growth rate in the mid-platform pools, measured in situ, was highest in autumn but similar in the other seasons. In summer, however, in pools at the edge of the reef, often flushed by waves, the growth rate was as fast in summer as in autumn, either because of better provision of scarce nutrients or because of less inhibition by high temperature. Mortality, both of individuals and of fronds, was highest in the summer when pool isolation for one or more tidal cycles, caused by the coincidence of low high tide levels and a calm sea, was more common. Hormosira could tolerate full summer sunlight, water temperatures of up to 40°C, 140 psu (four times the strength of seawater) but not dehydration. Dehydration caused inter-annual variation in cover and in the total number of plants present, but with no overall trend over 12 years. Sand cover and rotting cast weed could also cause mortality. Survivorship was Slobodkin’s Type IV, with few plants reaching 4 years but high longevity after that, due to the establishment of a holdfast which could regenerate new fronds. Compared with other fucoids, growth was slow. The lifestyle resembles that of Ascophyllum nodosum.

Salt tolerance at single cell level in giant-celled Characeae.

Characean plants provide an excellent experimental system for electrophysiology and physiology due to: (i) very large cell size, (ii) position on phylogenetic tree near the origin of land plants and (iii) continuous spectrum from very salt sensitive to very salt tolerant species. A range of experimental techniques is described, some unique to characean plants. Application of these methods provided electrical characteristics of membrane transporters, which dominate the membrane conductance under different outside conditions. With this considerable background knowledge the electrophysiology of salt sensitive and salt tolerant genera can be compared under salt and/or osmotic stress. Both salt tolerant and salt sensitive Characeae show a rise in membrane conductance and simultaneous increase in Na+ influx upon exposure to saline medium. Salt tolerant Chara longifolia and Lamprothamnium sp. exhibit proton pump stimulation upon both turgor decrease and salinity increase, allowing the membrane PD to remain negative. The turgor is regulated through the inward K+ rectifier and 2H+/Cl- symporter. Lamprothamnium plants can survive in hypersaline media up to twice seawater strength and withstand large sudden changes in salinity. Salt sensitive C. australis succumbs to 50–100 mM NaCl in few days. Cells exhibit no pump stimulation upon turgor decrease and at best transient pump stimulation upon salinity increase. Turgor is not regulated. The membrane PD exhibits characteristic noise upon exposure to salinity. Depolarization of membrane PD to excitation threshold sets off trains of action potentials, leading to further loses of K+ and Cl-. In final stages of salt damage the H+/OH- channels are thought to become the dominant transporter, dissipating the proton gradient and bringing the cell PD close to 0. The differences in transporter electrophysiology and their synergy under osmotic and/or saline stress in salt sensitive and salt tolerant characean cells are discussed in detail.

Impact of seawater salts on the viscoelastic behavior of flocculated mineral suspensions

The impact of several electrolytes present in seawater on the rheological properties of flocculated alumina suspensions was assessed by using creep testing at pH conditions both above and below the isoelectric point. Flocculated suspensions were obtained by adding a high molecular weight anionic polymer flocculant to a cylinder of alumina suspension and aggregating the suspension using the plunger method. The suspension was allowed to sediment and the supernatant liquid decanted prior to tests of the viscoelastic properties of the resulting sediment. Salts analyzed were MgCl2, CaCl2 and NaCl, known as water structure makers, and KI and KCl, known as water structure breakers. A high salt concentration of 0.5M was used to approach the ionic strength of seawater. For both pH's studied, the sediments demonstrated viscoelastic non-linear behavior observed as a non-linear relationship between yield strain and applied stress. In the absence of flocculant, it has been observed that the viscosity and yield stress of a suspension increase in the presence of structure maker salts for the case of both silica and alumina suspensions. In the presence of flocculant, new results are found: when the solid and flocculant were of opposite charge, the shear yield stress of the alumina suspensions increased with the breaker character of the salts, however when the solid and flocculant were of similar charge, then the yield stress is independent of the character of the salts. Similar water structures on the interacting surfaces lead to strong particle networks. The work demonstrates the importance of salt-surface interaction to the rheology of suspensions in the presence of polymer flocculants, as is typical of many mineral processing operations world-wide.