Molar NaCl Research Articles

Ratios rather than concentrations of nutritionally important elements may shape honey bee preferences for ‘dirty water’

1. Honey bees require minerals for a complete diet. However, minerals from flowers can be inadequate in concentration and composition. Therefore, honey bees may drink ‘dirty water’ from natural sources such as puddles. Some research has attempted to simulate this through honey bee bioassays, but to date, these have tested minerals individually, not as mixtures as would occur in nature. Here, for the first time, we use honey bees in bioassays in which a range of mineral mixtures are presented together in choice experiments.2. Six minerals (NaCl, KCl, CaCl2, MgCl2, NH4Cl, and KH2PO4) were used in mixtures to simulate different mineral stoichiometries, which may occur in ‘dirty water’, such as puddles, from which honey bees often drink. Based on the honey bee mineral tolerance ranges from the literature, these mixtures were offered in aqueous solutions at low, medium, high, and mixed molar concentrations. Deionised water and sucrose were neutral and positive controls, respectively. Petri dishes were set up in containers in a laboratory. Twenty worker honey bees (Apis mellifera L.) were placed into each container and observed for drinking behaviour for 1 h.3. Honey bees preferred the mixed molar treatment comprising a high Na:K ratio, a medium molarity of NaCl and a low molarity of the other minerals. This novel finding suggests that mixed mineral ‘dirty water’ should be investigated on a larger scale with multiple hives in the field and highlights the importance of stoichiometrically balanced honey bee diets.

Multivariate optimization approach applied to natural polymers from Ceratonia siliqua L. and Moringa oleifera Lam as coagulating/flocculating agents

ABSTRACT In this study, a multivariate experimental design was applied to optimize the operational conditions (seed mass, salt concentration, and pH) to employ Ceratonia siliqua L. (carob) and Moringa oleifera Lam (moringa) as coagulating/flocculating agents for water treatment. Currently, the coagulation stage in water treatment uses aluminium compounds, due to the characteristic reaction to natural alkalinity in raw water, and for its low market value. Considering that aluminium effects on human health are not sufficiently studied to acknowledge its toxicity, and its significant environmental impacts, it is suitable for the studies to search for alternatives to be employed in the water treatment that will be distributed to human consumption. This study was carried out with raw water of high turbidity level, 83.7 NTU. The raw water collected was also characterized according to pH, colour, Total Organic Carbon (TOC), Dissolved Organic Carbon (DOC), and Dissolved Organic Matter (DOM), with values of 6.7, 178 NTU, 6.80, 2.45 and 138.58 mg/L, respectively. The optimized results showed that with 2 g of seed, 0.5 mol of NaCl, and pH 11.0 In these conditions, moringa coagulant reached 90%, 86%, 6%, 67%, and 81% for turbidity, colour, DOC, TOC, and DOM removal, respectively, whereas the carob coagulant achieved 85%, 76%, 5%, 55.6%, 66.7%, respectively for the same parameters’ removal. Both coagulants presented lower sludge formation, 1.1 mL L−1 for moringa coagulant, and 1.1 mL L−1 for carob coagulant. The results could be considered promises, and natural polymers carob and moringa can be suggested as alternatives agents in coagulation/flocculation stages for water treatment.

Extraction lipids from chlorella vulgaris by supercritical CO2 for biodiesel production

This study investigated the impact of supercritical CO2 lipid extraction method (SCCO2) from Chlorella vulgaris microalgae for biodiesel production. In this research Chlorella vulgaris oil extracted using SCCO2 and conventional solvent (n-hexane and ethanol). Extraction method was carried out using high pressure CO-solvent the extraction experiments were conducted at (12L: 12D) light/dark regime in 8 treatments, including: T1 (without any shock), T2 (acidity shock, pH:11), T3 (salinity shock, 1 molar NaCl), T4 (nutritional shock, depletion of nutrition), T5 (acidity+salinity shock), T6 (acidity+nutritional shock), T7 (salinity+nutritional shock) and T8 (acidity+salinity+nutritional shock). For each experiment used 10 g algae biomass. The results of growth performance indicated that different medium conditions such as salinity, acidity and nutritional terms with light and dark time shocks can enhanced the Chlorella vulgaris biomass productivity (SGR (0.17±0.00), biomass productivity (0.34±0.05) and CO2 consumption rate (629.97±34.62). The major FAME profile of the obtained oils were (C16:0) palmitic, (C18:0) Stearic, (C22:1n9) ercucic, (C24:1n9) nervonic, (C22:6n3) DHA and (C20:3n3) eicosatrieonoic acids. The measured saponification value (SV) and iodine value (IV) showed no significant differences between the experimental samples (P<0.05). The best results of cetane number (CN) and degree of unsaturation (DU) values was recorded in TL7 (5062.04±23.14) and TL8 (40.93±1.20), respectively. At least, fatty acids content and lipid extracted by SCCO2 method under different pressure and temperature had the best results in 370 bar and 40 °C, while lowest restitution was seen in 200 bar and 40 °C, respectively. The results of this study illustrated that SCCO2 method had positive impact on oil extraction from Chlorella vulgaris had desirable properties.

High-Efficiency Cationic Labeling Algorithm of Macroaggregated Albumin with 68Gallium.

The generator product radionuclide gallium-68(68Ga) is widely used for PET/CT imaging agents and the 68Ga-labeled MAA is an attractive alternative to 99mTc-labeled MAA. Using a commercially available MAA labeling kit for 99mTc, we presented a reliable synthesis protocol with a highly efficient, organic solvent-free cationic method in GMP conditions in the Scintomics automated synthesis unit. The labeling process was performed by incubating for 7 min at 90 °C in the borax vial containing the generator product 68GaCl3 MAA-HEPES eluted from the PSH+ cartridge with 1.5 mL 5 molar NaCl. Quality control of the final product content was examined, and radiopharmaceutical production was carried out in accordance with GMP guidelines. 68Ga eluted from the generator was obtained in more than 99% radiochemical purity and efficiency. In this case, the labeling efficiency was found to be >99%. When the results of SEM-EDX analysis in the final product were examined, it was determined that most of toxic metals were no appreciable in the product content. The radiochemical and chemical purity of the final product allows direct use without purification steps to remove "free 68Ga" or other toxic compounds.

More reasons to add less salt – NaCl's unfavourable impact on glass transition and moisture sorption of amorphous maltose-NaCl blends

Adding NaCl to maltose depressed the glass transition temperature (T g ) of freeze-dried maltose-(dissociated) NaCl powder (by up to 9.1 °C at 10%mol addition level) but did not impact sorption isotherm in the water activity (a w ) range of 0.1–0.3. Above 2%mol NaCl, moisture and NaCl had an antagonistic effect on T g depression of freeze-dried maltose-NaCl powder. According to linear and Flory-Fox models, T g increased linearly with mixtures’ molecular weight. T g and sorption isotherm curves were then combined to determine the a w at which glass transition occurs at various storage temperatures (i.e. critical a w ). From the combined curve, critical a w decreased linearly with increased NaCl concentration in the mixture. Furthermore, the critical a w depression was steeper at higher temperatures. Finally, neither processing (dry mixing versus freeze drying) nor NaCl concentration affected the crystallization kinetics of amorphous maltose during dynamic humidification (0 to over 90% relative humidity) at 25 °C. • NaCl lowered the temperature and humidity at which amorphous maltose becomes sticky. • Temperature sensitivity can be predicted by amorphous mixtures' molecular weight. • Adding ≤10%mol NaCl did not affect amorphous maltose's crystallization kinetics.

Thermodynamic Properties: Determination of the (NaCl + l-Proline + H2O) Ternary System Based on Potentiometric Measurements at T = (293.2, 303.2 and 313.2) K

In this work, the thermodynamic properties of the ternary (NaCl + l-proline + H2O) system are reported, based on the potentiometric technique. The potentiometric measurements were carried out by using self-made ion selective electrodes (ISE) on the galvanic cell of type Na-ISE | NaCl (mB), l-proline (mA), H2O | Ag/AgCl in various series of the l-proline aqueous solution (mA = 0.2227, 0.4571, 0.7043 and 0.9651) mol·kg−1 and NaCl in pure water over NaCl molalities ranging from (0.01 to 4.00) mol·kg−1 at T = (293.2, 303.2, and 313.2) K and p = 101.3 kPa. Correlation of the experimental data was performed based on the Pitzer model as modified by Esteso et al. (MP). The MP parameters obtained were used to calculate the natural logarithm of the ratio of l-proline activity coefficients in NaCl and water mixtures to l-proline activity coefficients in pure water ( $$\ln ({{\gamma_{{\text{A}}} } \mathord{\left/ {\vphantom {{\gamma_{{\text{A}}} } {\gamma_{{\text{A}}}^{0} }}} \right. \kern-\nulldelimiterspace} {\gamma_{{\text{A}}}^{0} }})$$ ), osmotic coefficients (φ), excess Gibbs energy (GE/RT) and water activity (aw) for different series of l-proline molality. The NaCl transfer Gibbs energy and McMillan–Mayer parameters were also calculated for the system. Good consistency was found between the MP and McMillan–Mayer model parameters.

Impact of the particle mixing state on the hygroscopicity of internally mixed sodium chloride-ammonium sulfate single droplets: a theoretical and experimental study.

Sodium chloride (NaCl) is the main constituent of sea-salt aerosols. During atmospheric transport, sea-salt aerosols can interact with gases and other particles including secondary aerosols containing ammonium sulfate ((NH4)2SO4). This paper reports on the deliquescence relative humidity (DRH) of internally mixed sodium chloride-ammonium sulfate (NaCl/(NH4)2SO4) coarse particles by means of an acoustic levitation system fitted with a confocal Raman microscope (CRM). The chemical composition and physical state of individual levitated particles of different initial NaCl mole fractions were monitored during the deliquescence cycle by CRM. Experimental results were compared to the data predicted by the thermodynamic model E-AIM (Extended-Aerosol Inorganics Model). We demonstrated that NH4Cl, Na2SO4 and NH4NaSO4·2H2O are formed in recrystallized particles and coexist with NaCl and (NH4)2SO4. All these products are randomly distributed within the particles. Deliquescence curves described two or three-stage phase transitions depending on the initial composition of the droplet. Significant discrepancies between the model and the laboratory experiments were observed for NaCl mole fractions varying between 0.40 and 0.77 due to a divergence between the predicted and the truly present products in the particles' solid fraction during the humidification cycle.

Effect of sodium chloride on the behaviour of the lactose in aqueous solution studied from diffusion experiments and molecular dynamics simulations

Ternary mutual diffusion coefficients (D11, D22, D12 and D21) measured by the Taylor dispersion method are reported for aqueous solutions of (NaCl + lactose) at 298.15 K and NaCl concentrations up to 1.00 mol dm−3. The coupled diffusion of NaCl (1) and lactose (2) is significant, as indicated by the large negative cross-diffusion coefficients. In this sense, from the values of these cross-diffusion coefficients a counter-transport of 0.4 mol of NaCl per mol of diffusing lactose is inferred, whereas only 0.02 mol of lactose could be counter-transported by one diffusing mole of NaCl. The main diffusion coefficient data are compared with the binary ones of both pure solutes in water and discussed on the basis of Onsager-Fuoss and Pikal models. From these data and by performing molecular dynamics simulations, it is possible to obtain a better understanding of the effect of sodium chloride on the transport of lactose in aqueous solutions, as well as to assume the importance of the Na+-lactose short-range interaction, competing with the coulomb long-range interaction between the sodium and chloride ions, especially at low concentration of NaCl.

GENETIC ASSOCIATION AMONG MORPHOLOGICAL TRAITS OF ZEA MAYS SEEDLINGS UNDER SALT STRESS

Zea mays is an important cereal crop which has been used by human from last thousands of years as grain crop. It is very sensitive for drought, heat, cold, salinity and heavy metals toxicity. For evaluating corn for salt stress we have conducted an experiment in the greenhouse of IMBB, University of the Lahore. Four maize genotypes were selected for our research work, viz., B-316, EV-1097Q, Raka-poshi and Sahiwal-2002 under the treatments of salt were kept as following: control, 0.2Molar NaCl, 0.5Molar NaCl, 0.7Molar NaCl and 1Molar NaCl. The selection of genotypes for high shoot and root length under treatments 0.5Molar NaCl, 0.7Molar NaCl may be fruitful for the improvement of crop production and productivity. It was found from results that the B-316 performed better under all stress treatments for seedling traits as compared with EV-1097Q and Sahiwal-2020 maize genotypes. The results showed that higher genetic advance and heritability was recorded for both root length and shoot length. The significant and positive correlation was recorded among root length, shoot length, root dry weight and shoot dry weight. The regression analysis showed that the higher contribution for shoot length was found for root length. It was concluded from our study that the selection of maize genotypes may be fruitful on the basis of root length and shoot length to improve grain yield under salt stress conditions.

EVALUATION OF MAIZE SEEDLING TRAITS UNDER SALT STRESS

Maize is an important cereal crop lies at third after wheat and rice in Pakistan. It is very sensitive to salt, heat, drought, cold and heavy metal stresses. To evaluate the effects of salt (NaCl) on maize plant we have conducted a research experiment in the Green House of Institute of Molecular Biology and Biotechnology, The University of Lahore, Lahore. We select hybrid P1429, P5971 and P6103 of Maize to access the effect of different concentrations of NaCl stress included control, 0.25Molar NaCl, 0.5Molar NaCl, 0.75Molar NaCl, and 1Molar NaCl applications. The pots were filled with pure sand and seeds of each hybrid were sown in each pot and were let to germinate. After 7 days of germination the data was collected for leaf length, root length, shoot length and root/shoot length ratio. The pots were then given the treatment and data of above mentioned traits was recorded, the application of treatments and data recording were repeated 4 times. The data recorded (4 times each after one week) was subjected to pooled analysis of variance to find significant differences among hybrids and treatments. The result of our study showed that there were significant correlation among root length, shoot length and leaf length of seedlings, from average performance of hybrid P6103 was better as compared with other two hybrids under higher salt stress conditions. It was suggested from our study that the hybrid P6103 may be used as salt tolerance hybrids for improving grain and fodder yield of maize under salt stress condition.

GENETIC ASSOCIATION AMONG SEEDLING TRAITS OF ZEA MAYS UNDER MULTIPLE STRESSES OF SALTS, HEAVY METALS AND DROUGHT

Maize is highly sensitive for drought, heat, cold, salinity and heavy metals toxicity. The grain yield and quality of grains is highly affected due to abiotic environmental factors. For evaluating maize under drought as well as salts and heavy metals we have conducted an experiment in the greenhouse of IMBB (Institute of Molecular Biology and Biotechnology), University of the Lahore. Four maize genotypes were selected for our research work, viz., B-316, EV-1097Q, Raka-poshi and Sahiwal-2002. The seeds of selected maize genotypes were sown in 72 pots. Each of the pot was in triplicate for each of the maize genotype. The treatments of drought, salt and heavy metals were kept as following: Control, 50% irrigation water, 0.5m Molar NaCl, 0.5m Molar ZnSO4, 0.5m Molar AlCl3 and 0.5m Molar MgCl2. It has been revealed from results the performance of maize genotypes was variable under different treatments of heavy metals, drought and salt stress environments. The treatments of AlCl3 and NaCl were found as the higher toxic treatments for most of the study traits of maize which may decrease the photosynthetic rate and accumulations of organic compounds in maize seedlings and may cause the death of seedlings. Significant and positive correlation was reported between shoot length other studied traits while the higher contribution for shoot length was reported for root length, leaf area and fresh root/shoot weight ratio. It was found from results that the Sahiwal -2002 performed better under all stress treatments for seedling traits as compared with B-316, Raka-poshi and EV-1097Q maize genotypes.

EFFECTS OF SALT STRESS ON THE GROWTH TRAITS OF CHICKPEA (CICER ARIETINUM L.) AND PEA (PISUM SATIVUM L.) SEEDLINGS

Chickpea (Cicer arietinum L.) and pea (Pisum sativum L.) both are important legume crops grown throughout the world for protein and they also contain essential vitamins and fibers. Chick pea and pea are very sensitive to abiotic stress that includes heat, drought, cold and salt stress conditions. To access the effects of salt stress on the chick pea and pea an experiment was performed in the Green House of Institute of Molecular Biology and Biotechnology, The University of Lahore, Lahore. The seeds of both genotypes were grown in 18 pots with 2 kg pure sand and applied different concentrations of NaCl stress after 7 days of germination. The application of salt treatments was repeated 4 times each after 7days interval and data of different morphological traits was recorded each time. The treatments were included control, 0.25Molar NaCl, 0.5Molar NaCl concentrations. The data was recorded and pooled analysis of variance was carried out for significance of results. The average root length was recorded as 5.7522±0.0211cm and shoot length (11.139±0.0011cm) while average fresh plant weight was recorded as 0.5811±0.0002g under different salt stress conditions. The finding of our result proved that both varieties chickpea and pea showed variable behavior under salt stress conditions while the pea genotype showed more tolerant against different salt treatments which indicated pea genotypes may be used for future breeding to improve yield and growth of pea crop. The results showed that there was significant and positive correlation among root length, shoot length and leaf length of chickpea and pea seedlings which concluded that root length and shoot length may be used as selection criteria to induced stress tolerance in crop plants.

Measurements and predictive models of high-pressure H2 solubility in brine (H2O+NaCl) for underground hydrogen storage application

In the context of Underground Hydrogen Storage (UHS), the stored gas is in direct contact with brine (residual brine from the cavern or formation water of deep aquifers). Therefore, knowledge of the phase equilibria (solubility of hydrogen in brine and water content in the hydrogen-rich phase) in the geological reservoir is necessary for the study of hydrogen mobility and reactivity, as well as the control, monitoring and optimization of the storage. The absence of measured data of high-pressure H2 solubility in brine has recently led scientists to develop predictive models or to generate pseudo-data using molecular simulation. However, experimental measurements are needed for model evaluation and validation. In this work, an experimental apparatus based on the “static-analytic” method developed and used in our previous work for the measurement of gas solubility in brine was used. New solubility data of H2 in H2O+NaCl were measured more or less under the geological conditions of the storage, at temperatures between 323 and 373 K, NaCl molalities between 0 and 5m, and pressures up to 230 bar. These data were used to parameterize and evaluate three models (Geochemical, SW, and e-PR-CPA models) tested in this work. Solubility and water content tables were generated by the e-PR-CPA model, as well as a simple formulation (Setschenow-type relationship) for quick and accurate calculations (in the fitting range) of H2 solubility in water and brine was proposed. Finally, the developed models estimate very well the water content in hydrogen-rich phase and capture and calculate precisely the salting-out effect on H2 solubility.

An Electrochemical Neutralization Cell for Spontaneous Water Desalination

Summary We show that conversion of acid-base neutralization energy into electrical energy via reversible H2 redox can be used to spontaneously desalinate saline water while generating electric power and consuming ∼13.6 kJ for the removal of 1 mol of NaCl. This electrochemically driven neutralization pathway exhibits a positive temperature coefficient for the open circuit voltage (1.63 ± 0.11 mV/K), which, in turn, means it can harvest ∼24 kJ/mol of entropic heat, at room temperature, from the surroundings as electrical driving force. Our demonstration of desalination without the aid of an external power supply by performing reversible redox reactions and involving only gases, water, H+, and OH−, such that the products and the reactants of the reaction do not contaminate the desalinated water, opens up an unprecedented pathway for addressing the potable water crises looming over the 21st century.

Effect of LPSO phases and aged-precipitations on corrosion behavior of as-forged Mg–6Gd–2Y–1Zn–0.3Zr alloy

This paper analyzed the effect of long period stacking ordered phases (LPSO) and aged-precipitations on corrosion behavior of Mg–6Gd–2Y–1Zn–0.3Zr magnesium alloys. As-forged alloys were subjected to aging at 225°C for a period of 4 and 12h such as to acquire the required microstructure. For these as-forged Mg alloys, some structures of LPSO phases were broken and replaced by fine dynamic recrystallized grains. After undergoing the aging treatment for a 4h period, these alloys demonstrated a higher number of recrystallized grains and lesser LPSO phases. However, the 12 aging of the alloys produced the least number of LPSO phases, but produced a considerable amount of aged-precipitations on the recrystallized grains. During the period of 120h immersion in 0.1mol NaCl solution, the corrosion behavior of the alloys was mainly determined by the decreased volume fraction of LPSO phases and the increased volume fraction of aged-precipitations. Alloys after aging for a 12h period, displayed the most critical corrosion rate owing to the severe micro-galvanic corrosion between high voltage aged-precipitations or LPSO phases and Mg-matrix, whereas, the alloys after aging for a 4h period, displayed the best corrosion resistance due to the lesser volume fraction of LPSO phases. As-forged alloys with the most amount of volume fraction of LPSO phases displayed a moderate corrosion resistance.

Solubility and Physical Properties of Calcium Sulfate Dihydrate in NaCl and Glycerol Aqueous Solution at 303.15, 323.15, and 343.15 K

The solubility of calcium sulfate dihydrate (CaSO4·2H2O) was measured in NaCl and glycerol aqueous solution with the mass fraction of glycerol 0–80% and molality of NaCl 0–6 m in the temperature ra...

Paleo-Hydrothermal Predecessor to Perennial Spring Activity in Thick Permafrost in the Canadian High Arctic, and Its Relation to Deep Salt Structures: Expedition Fiord, Axel Heiberg Island, Nunavut

Paleo-Hydrothermal Predecessor to Perennial Spring Activity in Thick Permafrost in the Canadian High Arctic, and Its Relation to Deep Salt Structures: Expedition Fiord, Axel Heiberg Island, Nunavut

Temperature and Gas/Brine Content Affect Seismogenic Potential of Simulated Fault Gouges Derived From Groningen Gas Field Caprock

AbstractWe investigated the rate‐and‐state frictional properties of simulated anhydrite‐carbonate fault gouge derived from the basal Zechstein caprock overlying the seismogenic Groningen gas reservoir in the NE Netherlands. Direct shear experiments were performed at in situ conditions of 50–150 °C and 40‐MPa effective normal stress, using sliding velocities of 0.1–10 μm/s. Reservoir pore fluid compositions were simulated using 4.4 Molar NaCl brine, as well as methane, air, and brine/gas mixtures. Brine‐saturated samples showed friction coefficients (μ) of 0.60–0.69, with little dependence on temperature, along with velocity strengthening at 50–100 °C, transitioning to velocity weakening at 120 °C and above. By contrast, gas filled, evacuated and partially brine‐saturated samples showed μ values of 0.72 ± 0.02 plus strongly velocity‐weakening behavior accompanied by stick slip at 100 °C (the only temperature investigated for gas‐bearing and dry samples). A microphysical model for gouge friction, assuming competition between dilatant granular flow and thermally activated compaction creep, captures the main trends seen in our brine‐saturated samples but offers only a qualitative explanation for our gas‐bearing and dry samples. Since the reservoir temperature is ~100 °C, our results imply high potential for seismogenic slip nucleation on faults that cross cut and juxtapose the basal Zechstein anhydrite‐carbonate caprock against the Groningen reservoir sandstone, specifically in the gas‐filled upper portion of the reservoir system.

Predicting solubility of CO2 in brine by advanced machine learning systems: Application to carbon capture and sequestration

Carbon dioxide (CO2) capture and sequestration in saline aquifers have turned into a key focus as it becomes an effective way to reduce CO2 in the atmosphere. The solubility of CO2 in brine is of vital role in monitoring CO2 sequestration. In this study, based on molality of NaCl, pressure and temperature, modeling of CO2 solubility in brine has been carried out utilizing multilayer perceptron (MLP) and radial basis function neural network (RBFNN). Levenberg-Marquardt (LM) algorithm was implemented to optimize the MLP model, while genetic algorithm (GA), particle swarm optimization (PSO) and artificial bee colony (ABC), were applied to optimize the RBFNN model. To this end, a widespread experimental databank including 570 data sets gathered from literature was considered to implement the proposed models. Graphical and statistical assessment criteria were considered to investigate the performances of these models. The obtained results revealed that all the proposed techniques are in excellent correspondence with experimental data. In addition, the performance analyses showed that RBFNN-ABC model exhibits the higher accuracy in the prediction of CO2 solubility in brine compared with the other proposed smart approaches and the existing well-known models. The RBFNN-ABC model yields a root mean square error (RMSE) value of 0.0289 and an R2 of 0.9967. Finally, the RBFNN-ABC model validity was confirmed and a small number of probable doubtful data was detected.

Influence of Surface Roughness on the Contact Angle due to Calcite Dissolution in an Oil–Brine–Calcite System: A Nanoscale Analysis Using Atomic Force Microscopy and Geochemical Modeling

Low-salinity water flooding appears to be a promising means to improve oil recovery in carbonate reservoirs because of a wettability alteration process. Contact angle measurement is a direct approach to reveal the wettability alteration in an oil–brine–carbonate system. However, questions have been raised about using contact angle measurement to justify the wettability alteration. This is because the contact angle may be significantly affected by surface roughness variation in the presence of low-salinity water because of calcite dissolution during the contact angle measurement. To clarify the cause and effect of wettability alteration during low-salinity water flooding, we measured the contact angle on two calcite substrates with similar surface roughness (7 and 4 nm) in the presence of high-salinity water (1 mol NaCl + 0.01 mol CaCl2) and low-salinity water (100 times diluted high-salinity water). Moreover, we measured the surface roughness of the substrates before and after the contact angle measuremen...