Salinity Concentration Research Articles

Performance Analysis of Air Gap Membrane Distillation Process Enhanced with Air Injection for Water Desalination

Water scarcity is a global issue, and desalination is an alternative to providing fresh water. Renewable energies could be used in thermal desalination to produce freshwater from high saline concentration solutions. In this paper, the experimental performance of an air-injection-Air Gap Membrane Distillation (AGMD) module is presented. The effect of the operation parameters (saline solution temperature, air flow, and salt concentration) on the distilled water rate was evaluated. The air injection enhanced the distilled water rate by 22% at the highest air flow and a solution flow rate of 80 °C, compared to the conventional condition (without air injection) at a salt concentration of 100,000 ppm. Under the same operating conditions, the increase was 17% at a salt concentration of 70,000 ppm. The maximum distilled water rate was 14.10 L/m2·h at 80 °C and an airflow of 1.5 L/min with the highest salt concentration, while it was also 14.10 L/m2·h at the lower salt concentration was 14.10 L/m2·h. The distilled water quality also improved as the air flow increased, since a conductivity reduction of 66% was observed. With the described mathematical model, 94% of the calculated values fell within ±10% of the experimental data for both salt concentration conditions.

Enhancing Soil Salinity Evaluation Accuracy in Arid Regions: An Integrated Spatiotemporal Data Fusion and AI Model Approach for Arable Lands

Soil salinization is one of the primary factors contributing to land degradation in arid areas, severely restricting the sustainable development of agriculture and the economy. Satellite remote sensing is essential for real-time, large-scale soil salinity content (SSC) evaluation. However, some satellite images have low temporal resolution and are affected by weather conditions, leading to the absence of satellite images synchronized with ground observations. Additionally, some high-temporal-resolution satellite images have overly coarse spatial resolution compared to ground features. Therefore, the limitations of these spatiotemporal features may affect the accuracy of SSC evaluation. This study focuses on the arable land in the Manas River Basin, located in the arid areas of northwest China, to explore the potential of integrated spatiotemporal data fusion and deep learning algorithms for evaluating SSC. We used the flexible spatiotemporal data fusion (FSDAF) model to merge Landsat and MODIS images, obtaining satellite fused images synchronized with ground sampling times. Using support vector regression (SVR), random forest (RF), and convolutional neural network (CNN) models, we evaluated the differences in SSC evaluation results between synchronized and unsynchronized satellite images with ground sampling times. The results showed that the FSDAF model’s fused image was highly similar to the original image in spectral reflectance, with a coefficient of determination (R2) exceeding 0.8 and a root mean square error (RMSE) below 0.029. This model effectively compensates for the missing fine-resolution satellite images synchronized with ground sampling times. The optimal salinity indices for evaluating the SSC of arable land in arid areas are S3, S5, SI, SI1, SI3, SI4, and Int1. These indices show a high correlation with SSC based on both synchronized and unsynchronized satellite images with ground sampling times. SSC evaluation models based on synchronized satellite images with ground sampling times were more accurate than those based on unsynchronized images. This indicates that synchronizing satellite images with ground sampling times significantly impacts SSC evaluation accuracy. Among the three models, the CNN model demonstrates the highest predictive accuracy in SSC evaluation based on synchronized and unsynchronized satellite images with ground sampling times, indicating its significant potential in image prediction. The optimal evaluation scheme is the CNN model based on satellite image synchronized with ground sampling times, with an R2 of 0.767 and an RMSE of 1.677 g·kg−1. Therefore, we proposed a framework for integrated spatiotemporal data fusion and CNN algorithms for evaluating soil salinity, which improves the accuracy of soil salinity evaluation. The results provide a valuable reference for the real-time, rapid, and accurate evaluation of soil salinity of arable land in arid areas.

The Role of Salicylic Acid in Salinity Stress Mitigation in Dizygostemon riparius: A Medicinal Species Native to South America

Salicylic acid (SA) is a bioregulator well-known for mitigating salinity damage in plants. However, no studies have examined the interaction between SA and salinity in Dizygostemon riparius, a species rich in bioactive molecules. Therefore, we aimed to evaluate the effect of SA application on Dizygostemon riparius under different salinity levels. A completely randomized experiment was conducted in a 2 × 3 factorial design (two SA concentrations of 0 and 100 µM and three salinity concentrations of 0, 200, and 400 mM NaCl) with five replicates. At 400 mM NaCl, leaf temperature increased by 11%, while relative water content and total soluble carbohydrates decreased by 30% and 35%, respectively, leading to reduced biomass accumulation. Notably, the SA application mitigated these effects by restoring relative water content under 400 mM NaCl and improving carboxylation efficiency and intrinsic water-use efficiency under 200 mM NaCl. Additionally, dry biomass was maintained under both 200 and 400 mM NaCl with SA treatment. These findings suggest that SA has a promising potential to alleviate salt stress in Dizygostemon riparius. Our results could inform cultivation practices, opening new perspectives on the use of SA as an attenuator of salinity stress.

Isolation and purification of esterase enzyme from marine bacteria associated with biodegradation of polyvinyl chloride (PVC).

Polyvinyl chloride (PVC) is the third most produced synthetic plastic and releases the most harmful and lethal environmental component after incineration and landfilling. Few studies on microbial degradation of PVC have been reported but very little knowledge about the enzymes. In the present study, esterase enzyme was isolated and partially purified from marine bacterial isolates (T-1.3, BP-4.3 and S-237 identified as Vibrio sp., Alteromonas sp., and Cobetia sp., respectively) having the capability of PVC degradation. Initially, a plate assay was carried out for testing esterase production by studying bacteria using 1-naphthyl acetate as substrate. Enzyme assay showed higher production of esterase i.e. 0.57 U mL-1 (2nd day), 0.46 U mL-1 (2nd day) and 0.55 U mL-1 (5th day) by bacterial isolate Vibrio sp., Alteromonas sp. and Cobetia sp., respectively incubated with PVC. Other enzymes like lipase, laccase and manganese peroxidase were much less or negligible compared to esterase enzyme production. Sephadex G-50 column purification had shown 58.62, 42.35 and 223.70 units mg-1 of a specific activity by esterase for bacterial isolates Vibrio sp., Alteromonas sp. and Cobetia sp., respectively. Further, Sephadex G-50 column purification removed all the contamination and gave a clear appearance of the band at 38, 20 and 20 KD for bacterial isolates Vibrio sp., Alteromonas sp., and Cobetia sp., respectively. Esterase has shown maximum stability at a range of pH between 6.0 to 7.5, temperature between 30 to 35°C and salinity concentration between 3 to 3.5M for all bacterial isolates. In conclusion, esterase enzyme has promising potential to degrade PVC which can contribute to the decline the plastic pollution in an eco-friendly manner from the environment.

Effect of salinity stress on the morphological parameters of <i>Hura crepitans</i> L. ameliorated with <i>Calapogonium mucunoides</i> DESV. and Biochar

Salinity is one of the most serious limiting factors for plant growth and production. This study assessed the effect of salinity stress on the morphological parameters of Hura crepitans ameliorated with Calapogonuim mucunoides Desv. and Biochar. Standard methodology was adopted to examine physicochemical properties of the soil and morphological parameters of the plant. The physicochemicalproperties of the experimental soils was significant at p=0.01. Morphological parameters of shoot length of H. crepitans at 1% non-amended saline soil for week 6 and 7 recorded 4.03±4.03cm which indicated a significant reduction (p=0.01) when compared to control 15.70±3.35 and 19.50±4.43cm respectively. The amelioration of the saline soil at 0.001% KI with biochar and C. mucunoides (21.80±0.05 and 22.43±3.52cm) of H. crepitans shoot length was significant when compared to the control 21.00±4.00cm. The higher the concentration of salinity, the lower the petiole length of H. crepitans for amended treatments. The photosynthetic pigment 56.70±2.47 of H .crepitans at 0.001% was significant (p=0.05) when compared to the control 51.36±2.99.This results showed that salinity causes a detrimental effect on some plant growth parameters. However, amelioration of saline soil with C. mucunoides and biochar recorded a satisfactory remediation effect on the growth of H. crepitans. Based on this research, amelioration treatment such as C. mucunoides and biochar can be use to improve crops planted in saline soil.

Characterization of alkaline protease enzyme produced from marine yeast Candida orthopsilosis AKB-1 and its applications.

The present study has undertaken the isolation of marine yeasts from mangrove sediment samples and their ability to produce alkaline protease enzymes. A total of 14 yeast isolates were recovered on yeast-malt agar (YMA) and yeast extract peptone dextrose (YEPD) agar medium. After screening for proteolytic activity on skim milk agar, marine yeast isolate, AKB-1 exhibited a hydrolysis zone of 18mm. Optimal conditions for the enzyme production from yeast isolate AKB-1 were at 30°C, pH 8, fructose as carbon source, potassium nitrate as nitrogen source, and 25% saline concentration. Under the optimal conditions, the protease enzyme activity of the isolate AKB-1 was observed to be 978IU/mL. The structural and functional analysis was carried out through FTIR and HPLC analysis for the extracted protease enzyme. Furthermore, the enzyme produced was partially purified by solvent extraction using ethyl acetate and ammonium sulfate precipitation (3.4-fold) followed by dialysis (56.8-fold). The molecular weight of the purified enzyme was observed to be around 60kDa using SDS-PAGE. The extracted protein showed good antibacterial activity against six different clinical bacterial pathogens and the highest against Bacillus cereus (16 ± 0.5mm). The extracted protease enzyme was revealed to remove blood stains from cloth within 20min of application similar to the commercial detergent. The marine yeast isolate was further identified as Candida orthopsilosis AKB-1 (Accession number KY348766) through 18S rRNA sequencing, and a phylogenetic tree was generated.

Lipid metabolism improves salt tolerance of Salicornia europaea.

Salicornia europaea L., a succulent euhalophyte plant, has been found to exhibit optimal reproductive capabilities under appropriate salinity concentrations. However, the underlying metabolic changes are not yet fully understood. This study conducted a comprehensive analysis combining transcriptomic and lipidomic techniques to investigate the molecular mechanisms of lipid metabolism in response to different NaCl concentrations (0 and 200mM). Transcriptomic data demonstrated that salt treatment mainly affected processes including lipid biosynthesis, phosphatidylinositol signaling, and glycerophospholipid metabolism. The expression levels of several key genes involved in salt tolerance, namely SeSOS1, SeNHX1, SeVHA-A, SeVP1, and SePSS, were found to be upregulated upon NaCl treatment. A total of 485 lipid compounds were identified, of which 27 changed in abundance under salt treatment, including the enrichment of phospholipids and sphingolipids. Moreover, the increase in the double-bond index (DBI) was mainly due to phospholipids and sphingolipids. Comparing the acyl chain length (ACL) showed that the ACL coefficient of S1P significantly decreased under 200mM NaCl. This study suggests that S. europaea adapt to saline environments through altering phospholipids and sphingolipids to improve salt tolerance. The salinity response of S. europaea can provide important insights into the action of lipids and their salt adaptation mechanisms.

Potentially Pathogenic Vibrio spp. in Algal Wrack Accumulations on Baltic Sea Sandy Beaches

The Vibrio bacteria known to cause infections to humans and wildlife have been largely overlooked in coastal environments affected by beach wrack accumulations from seaweed or seagrasses. This study presents findings on the presence and distribution of potentially pathogenic Vibrio species on coastal beaches that are used for recreation and are affected by red-algae-dominated wrack. Using species-specific primers and 16S rRNA gene amplicon sequencing, we identified V. vulnificus, V. cholerae (non-toxigenic), and V. alginolyticus, along with 14 operational taxonomic units (OTUs) belonging to the Vibrio genus in such an environment. V. vulnificus and V. cholerae were most frequently found in water at wrack accumulation sites and within the wrack itself compared to sites without wrack. Several OTUs were exclusive to wrack accumulation sites. For the abundance and presence of V. vulnificus and the presence of V. cholerae, the most important factors in the water were the proportion of V. fucoides in the wrack, chl-a, and CDOM. Specific Vibrio OTUs correlated with salinity, water temperature, cryptophyte, and blue-green algae concentrations. To better understand the role of wrack accumulations in Vibrio abundance and community composition, future research should include different degradation stages of wrack, evaluate the link with nutrient release, and investigate microbial food-web interactions within such ecosystems, focusing on potentially pathogenic Vibrio species that could be harmful both for humans and wildlife.

Enrichment of marine microbes to remove nitrogen of urea wastewater under salinity stress

Salinity (NaCl) and urea concentration significantly affect the diversity, structural and physiological function of microbial communities in the biological treatment of wastewater. However, the responses of microbial in high salt and urea wastewater remain elusive. Here, we investigated microbial community function and assembly of four regions using gradient domestication experiment combined with 16S rRNA gene sequencing and statistical methods. The results showed that with the increase of salinity and urea concentration, the consortium Xiamen could still remove most urea, while the other three consortia could not. The alpha diversity of microbial community initially decreased and then increased, showing a recovery trend. After domestication, the consortium Xiamen exhibited high physiological activity and complex network structure, and the community assembly process changed from stochastic to deterministic during the domestication. Furthermore, the keystones with low abundance were associated with urea removal and important for maintain the complexity of the networks, while Arenibacter and Oceanimonas were found to be keystones in maintaining efficient urea removal in harsh environments. To sum up, environmental effects dominated by salinity and urea concentration stress drove the community assembly and species coexistence that underpinned the microbial differentiation pattern at a geographic scale. These results provided new sights for elucidate how microbial response to salinity and urea during wastewater treatment.

Vertical stratification of arctic microbial communities near potential hydrocarbon seepage off Cape Dyer, Nunavut

AbstractClimate change disproportionately affects the Arctic, where warming is up to four times greater than the global annual average experienced in southern regions. Baffin Bay in the Canadian Arctic Archipelago is an ecologically and biologically significant area that will likely experience an increase in marine vessel traffic as a result of consistent declines in annual sea ice coverage. Along the western coast of Baffin Bay is known to be a region of active, natural hydrocarbon seeps where elevated levels of methane have been detected in previous surveys. Petroleum hydrocarbons released from the seafloor can fuel microbial production and shape the baseline microbiome. Establishing a microbial baseline is highly valuable as it contributes to a fundamental understanding of the existing microbial diversity that may be impacted in the future by anthropogenic stressors. In this study, 16S and 18S rRNA gene amplicon sequencing surveys revealed that the vertical stratification of the water column is largely driven by differences in depth, temperature, salinity, and inorganic nutrient concentrations. Chemical analysis provides further support that active petrogenic methane seepage occurs around Cape Dyer but not in areas targeted in this study. Presence of n-alkanes and toluene in association with hydrocarbon-synthesizing phytoplankton suggests biogenic production of these compounds. These findings provide a baseline for future environmental monitoring assessments to evaluate how the prokaryotic and eukaryotic microbiome may be impacted by ongoing climate change and anthropogenic stressors in western Baffin Bay.

Enhanced bioremediation of saline azo dye effluents using PersiLac3: A thermo-halotolerant laccase from a tannery metagenome

Large quantities of recalcitrant azo dye wastewater represent an important environmental issue, owing to their toxicity and the difficulty of their treatment under hypersaline conditions. By maintaining high activity under salt-rich conditions, salt-tolerant laccases offer a promising solution for the effective breakdown of toxic azo dyes, making them indispensable for the sustainable treatment of industrial wastewater. This study explored the identification and application of a thermo-halotolerant laccase, PersiLac3, for bioremediation of azo dye wastewater under high-salt conditions typical of textile effluents. The broad substrate oxidation potential of PersiLac3 was assessed across diverse temperatures, pH levels, and challenging conditions, such as high salt levels, and in the presence of organic solvents and inhibitors. Remarkably, PersiLac3 showed enhanced activity (112.25 %) in 3 M NaCl, highlighting its superior ability to adapt to saline conditions. Kinetic studies of PersiLac3 indicated high efficiency and affinity for its substrate at saline concentrations ranging from 1 to 6 M NaCl. PersiLac3 effectively decolorized the Congo red dye (82.9 %) in highly concentrated solutions (5000 mg/L) within 15 min, and its performance was further improved in the presence of wastewater-relevant ions, achieving 92.3 % dye removal. Monitoring real wastewater treatments, PersiLac3 reduced optical density, underscoring its potential for application in the bioremediation of dye-laden and saline wastewater streams. The adaptability of PersiLac3 to harsh, high-salinity environments, coupled with its rapid dye decolorization efficiency, is an innovative and powerful tool for addressing environmental pollution challenges and advancing waste treatment methodologies.

Study on corrosion behavior and first-principle analysis of M50 steel in lubricating oil contaminated by salt water

The corrosive wear of M50 steel in lubricating oil contaminated with saline is a form of wear that often occurs within the main shaft bearings of aviation engines carried by aircraft working at sea. In the present paper, the corrosion behavior of M50 steel in lubricating oil contaminated with saline was studied. The open-circuit potential, polarization curve and impedance spectrum were analyzed by rotating electrochemical corrosion wear test. A three-layer interface microscopic molecular model was established with Materials Studio to simulate the dynamic corrosion evolution process of M50 steel self-matching pairs and the adsorption energy was calculated. The results show that the corrosion type is pitting corrosion. With the increase of saline concentration, the corrosion area becomes wider and shallower, and the size of the pitting core gradually decreases. The weight loss of M50 steel increases over time, but the trend slows down, which is also shown in the MS simulation results. Electrochemical tests show that the tribocorrosion of M50 steel is related to load, speed. As the load increases, the corrosion rate decreases. And, as the speed increases, the corrosion rate increases. This has practical significance for extending the understanding of tribocorrosion of M50 steel in marine atmospheric environments.

Enhancing Stability and Investigating Target Attainment of Benzylpenicillin in Outpatient Parenteral Antimicrobial Therapy: Insights from In Vitro and In Vivo Evaluations.

Background/Objective: Narrow-spectrum beta-lactam antibiotics such as benzylpenicillin and flucloxacillin are increasingly used in outpatient parenteral antimicrobial therapy (OPAT) programs to mitigate the adverse effects associated with broad-spectrum antibiotics. These beta-lactams require continuous administration via portable infusion devices during OPAT. However, the use of benzylpenicillin in OPAT requires special consideration because of its limited stability at elevated temperatures. Methods: We tested the benzylpenicillin stability, pH, and degradation of products in elastomeric pumps at different concentrations in saline and in buffered solution containing sodium citrate during a prolonged storage and at high temperatures (seven days at 2-8 °C followed by 24 h at 37 °C). Additionally, drug concentrations during intermittent bolus infusion and during OPAT were determined in five patients. The concentrations and degradation products of benzylpenicillin were measured using liquid chromatography mass spectrometry (LC-MS/MS). Results: Unbuffered benzylpenicillin solutions that were already degraded during refrigerator storage and analyte concentration were not measurable after 8 days. The stability of the buffered solutions was acceptable at all three of the tested concentrations (97.6 ± 1.3%, 96.3 ± 0.8%, and 94.9 ± 1.1% for 10 Mio IU, 20 Mio IU, and 40 Mio IU of benzylpenicillin). The stability was influenced by benzylpenicillin concentration, and several breakdown products were identified. Benzylpenicillin concentrations were measured in five patients during OPAT and ranged from 7.2 to 60 mg/L. Conclusions: Benzylpenicillin buffered with sodium citrate is a safe and convenient option for use in continuous infusions during OPAT and should be favored over broad-spectrum antibiotics. Therapeutic drug monitoring data indicate sufficient to high plasma levels when patients received benzylpenicillin as continuous infusions.

Niger Delta Oilfields Produced Water Characteristics and Treatment Technologies: Challenges and Solutions

The Nigerian Niger Delta oilfields have high water-to-oil ratio ranging from 50% to 95% water content, due to its secondary and tertiary production phases. Oil and gas producers could shut-in such wells, or develop cost effective approach for Produced Water, PW handling to meet reinjection or environmental permissibility. Thus, the study investigated the compositions and treatment techniques of Niger Delta oil and gas fields PW, and proffered solutions for actualizing minimal hazardous contaminants in PW. Characterization of PW from a Flow Station, an Oil processing and a Gas processing facilities showed biogeochemical homogeneity in the PW compositions with high organic and inorganic constituents, which are above injection and disposal specifications. The results of treated PW from the extant PW treatment (PWT) techniques showed that the total dissolved solids (TDS) concentration (6105.9 mg/l) from the Flow Station PW treatment facility did not meet the required specifications for injection into depleted wells or disposal into the environment (2,000.00 mg/l for inland, and 5,000.00 mg/l for nearshore). The salinity contents in the treated PW from the three PWT configurations were 2411.0 mg/l, 2218.6 mg/l, and 2165.4 mg/l, respectively, which were slightly above Nigerian Upstream Petroleum Regulatory Commission (NUPRC) specification (2000.0 mg/l) for nearshore disposal. The chemical oxygen demand (COD) concentration in the treated PW from the three PWT configurations were 153.0 mg/l, 148.1 mg/l, and 141.2 mg/l, respectively, which were above the NUPRC standard (125.0 mg/l). The oil and grease (O&G) concentration in the treated PW were 84.7 mg/l, 51.5 mg/l, and 58.0 mg/l, respectively, which also were above regulatory stipulation (30.0 mg/l) for nearshore disposal. The modular Bio-Unit + Ultra/Nanofiltration achieved more than 95% removal of both organic and inorganic constituents in the PW. Therefore, this study suggests that reconfiguring the extant PW treatment equipment with this cost-effective innovation would be the solution to PW treatment challenges in the Niger Delta oil and gas operations.

Soil Salinity Inversion Based on a Stacking Integrated Learning Algorithm

Soil salinization is an essential risk factor for agricultural development and food security, and obtaining regional soil salinity information more reliably remains a priority problem to be solved. To improve the accuracy of soil salinity inversion, this study focuses on the Manas River Basin oasis area, the largest oasis farming area in Xinjiang, as the study area and proposes a new soil salinity inversion model based on stacked integrated learning algorithms. Firstly, we selected four machine learning regression models, namely, random forest (RF), back propagation neural network, support vector regression, and convolutional neural network, for performance evaluation. Based on the model performance, we selected the more effective RF and BPNN as the basic regression models and further constructed a stacking integrated learning model. This stacking integration learning model improved the prediction accuracy by training a secondary model to fuse the prediction results of these two basic models as new features. We compared and analyzed the stacking integrated learning model with four single machine learning regression models. Findings indicated that the stacking integrated learning regression model fitted better and had good stability; on the test set, the stacking integrated learning regression model showed a relative increase of 8.2% in R2, a relative decrease of 14.0% in RMSE, and a relative increase of 6.5% in RPD when compared to the RF model, which was the single most effective machine learning regression model, and the stacking model was able to achieve soil salinity inversion more accurately. The soil salinity in the oasis areas of the Manas River Basin tended to decrease from north to south from 2016 to 2020 from a spatial point of view, and it was reduced in April from a temporal point of view. The percentage of pixels with a high soil salinity content of 2.75–2.80 g kg−1 in the study area had decreased by 19.6% in April 2020 compared to April 2016. The innovatively constructed stacking integrated learning regression model improved the accuracy of soil salinity estimation on the basis of the superior results obtained in the training of the single optimal machine learning regression model. As a consequence, this model can provide technological backup for fast monitoring and inversion of soil salinity as well as prevention and containment of salinization.

Chemical Spatiotemporal Characteristics and Environmental Driving Factors of Groundwater in Hetao Irrigation Area

To explore the chemical characteristics and environmental factors of groundwater in the Hetao Irrigation Area of Inner Mongolia, five irrigation fields, including UulanBuh, Jiefangzha, Yongji, Yichang, and Wulat, were selected as the research area. From 72 groundwater observation wells, a total of 216 groundwater samples were collected throughout three typical periods： the end of freeze-thaw （March）, the middle of irrigation （July）, and the end of autumn watering （November）. Comprehensive methods were utilized, such as statistical analysis, Piper three-line diagram, Gibbs diagram, ion ratio, and principal component analysis, to explore the changes in the groundwater chemical environment and the environmental driving factors of groundwater component formation. The groundwater drinking suitability was evaluated using the water quality index （WQI）, and the irrigation suitability was analyzed using the USSL and Wilcox plots. The results indicated that the groundwater in the research areas was generally saline, and the total anion and cation concentrations in each period in ascending order were as follows： late freeze-thaw stage, late autumn irrigation stage, and mid-irrigation stage, with Na+ and Cl- being the major contributing ions. The chemical type of groundwater was dominated by Cl-Na, followed by Cl·SO4-Ca·Mg and a coexistence with SO4-Ca·Mg, HCO3·Cl-Na, HCO3-Na, and HCO3-Ca·Mg. Based on WQI values, the shallow groundwater in Hetao Irrigation District was mainly classified as Class IV and Class V, and the quality was poor in general. According to the USSL diagram and Wilcox diagram, the comprehensive evaluation results showed that the salinity and sodium concentration of shallow groundwater in the irrigation area were generally high. A total of 80.6% of the water samples during the late freeze-thaw period, 76.1% during the mid-irrigation period, and 77.6% during the late autumn irrigation period lacked irrigation suitability. Two major controlling factors of groundwater chemical characteristics were present in the study area, namely, evaporation and rock weathering, and Na+ and Cl- mainly came from the dissolution and cation exchange of salt rocks. Agricultural irrigation and drought were the chief driving factors of groundwater chemical evolution in the Hetao Irrigation Area. The study provides technical support for optimizing agricultural management measures and a theoretical reference for rational utilization of groundwater resources in the Yellow River irrigation area of Inner Mongolia.

Salinity challenges and adaptive strategies in salinization-affected coastal Bangladesh: Implications for agricultural sustainability and water resource management

Abstract Salinization has become a rising global concern due to its notable effects on agriculture and freshwater resources. Coastal region of Bangladesh has been struggling with elevated levels of soil and water salinity, exacerbated by storm surges and rising sea levels. We assessed nutrient and salinity contents in agricultural and homestead lands, and the level of salinity in pond and canal water in six sub-districts in coastal Bangladesh. Finally, using household (HH) survey, focus group discussion (FGD) and key informant interview (KII), we explored the adaptive practices and challenges of salinity issues in agriculture and drinking water management. Soil nitrogen, phosphorus, and potassium contents exhibited significant variations across the sub-districts, which reflect the diversity of agricultural practices and soil management strategies. However, there was no notable difference in soil salinity across the sub-districts, which underscores the commonality of soil salinity as a pressing concern. Shyamnagar (13.99 dS m−1) recorded the highest level of pond water salinity, followed by Assasuni (13.96 dS m−1), Dacope (13.91 dS m−1), Koyra (13.58 dS m−1), Morrelganj (13.33 dS m−1), and Mongla (13.19 dS m−1) sub-districts, which highlights that water salinity decreased from exposed coast to the landward areas. Respondents in HH surveys, FGDs and KIIs identified salinity as a major challenge in agriculture and drinking water. Furthermore, climate-related stresses were recognized as significant challenges impacting crop productivity. The research highlights the feasibility of rainwater harvesting, with 89%–100% of HHs harvest rainwater in HH tanks, as an effective adaptive practice for managing drinking water. The study emphasizes the positive impact of vermicompost in reducing soil salinity levels, which is demonstrated by the 43%–88% of HHs using this practice, indicating its potential as a nature-based solution to address soil salinization. The findings underscore the need for resilient agricultural systems and sustainable water management approaches to tackle these challenges.

Odonata assemblages at two urban wetlands in West Bengal, India

Adult Odonata represent valuable indicators of natural habitat quality, ecosystem integrity, and pollution status in freshwater ecosystems. This study aimed to investigate how varying climatic condition, sub-habitat types, and physicochemical ambience of wetlands impact Odonata diversity. We compared the abundance and richness of Odonata in two urban wetlands and their surrounding areas: Purulia Sahebbandh (PS) located amidst Purulia town and faced higher anthropogenic threats, and Adra Sahebbandh (AS) located in a slightly remote location. Sampling was conducted over a period of one year (December 2018 to November 2019) using the Pollard walk method and direct search technique. A total of 47 Odonata species were recorded, including 33 species of dragonflies (Anisoptera) and 14 species of damselflies (Zygoptera). AS exhibited significant higher overall abundance compared to PS, with the monsoon season showing the highest abundance in both wetlands. Water-associated vegetation zones harbored the highest species richness. Species richness and abundance significantly differed among most of the sub-habitat types. Physicochemical factors such as pH, electrical conductivity, salinity, nitrate and phosphate concentrations, and dissolved oxygen significantly influenced Odonata abundance and species richness. The urban location, pollution load, and lack of natural vegetation in PS’s surrounding areas likely contributed to the lower Odonata abundance. Implementing sustainable management measures for wetlands and their surroundings is crucial to enhancing ecosystem services and supporting Odonata populations.

A novel green nanocomposite for EOR: Experimental Investigation of IFT Reduction, wettability Shift, and nanofluid stability

A stable nanofluid (NF) is crucial for success of nano-enhanced oil recovery (nEOR) processes. However, this represents a significant challenge as nanoparticles (NPs) tend to agglomerate under high salinity and NP concentration adversely affecting the oil recovery. New nanomaterials including functionalized nanoparticles also known as nanocomposites (NC) can help to overcome these issues. In this paper, first, we reported synthesis, characterization, and performance evaluation of a novel hydrophobic CuO-SiO2-Montmorillonite-K+-Thiazine NC for the first time. The NC was characterized using Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Analysis (EDAX), X-Ray Diffraction (XRD), Thermogravimetry Analysis (TGA), and Fourier Transform Infrared Spectroscopy (FTIR). SEM analysis showed that the NC is composed of uniformly distributed NPs. EDAX results confirmed presence of Cu, SiO2, O2, and Cl in the NC. XRD analysis indicated that SiO2 is the dominant phase in the crystal lattice and responsible for adsorption capacity of the NC. TGA analysis showed that the NC will be thermally stable in typical reservoir temperatures (∼80°C). FTIR results confirmed presence of Si-O, Cu-O, Si-O-Si, Al-O-Si, Al-OH, and OH bonds in the NC. In the second phase of this research work, the novel NC was used to investigate recovery of a Kazakhstani paraffinic heavy crude oil from Berea sandstone with focus on IFT reduction, oil recovery, wettability alteration, and stability analysis of the NFs. NFs were prepared with NC concentrations of 250, 500, and 1,000 ppm using moderate salinity (MS), low salinity (LS), and distilled water (DW). The results showed that the optimal NF (250 ppm LS) exhibited a high zeta potential value (−65.5 mV) indicating a high stability which is superior to all of the previously reported NCs. This high stability is attributed to use of thaizine as a source of natural surfactant. The optimum NF also altered the wettability of the sandstone by 77.6% and the contact angle (CA) was reduced from 117.9° to 26.4° making the system strongly water wet. The nanoclay has significantly facilitated the wettability alteration. The optimum NF also reduced the IFT by 92.3% from 27.42 mN/m to 2.11 mN/m. An incremental oil recovery of 20% was also achieved in the tertiary or EOR stage of oil. A comparison with the NCs reported in the literature confirmed the excellent performance of this novel NC in terms of NF stability, IFT reduction, and wettability alteration. The novel NC has a great potential for nEOR and other oilfield and environmental applications.

Optimization of iron, phosphate, and salinity in nutrient medium using response surface methodology for enhancing biochemical composition in Chlorella sp. culture

Microalga Chlorella sp. is a highly scientifically and commercially attractive unicellular microorganism and has developed a stable industry as a nutritional supplement for people and animals. Various nutrient media have been used to grow Chlorella sp. cultures to enhance their growth, pigmentation, and lipid content. However, the optimal biochemical composition and density of Chlorella sp. cultures require an understanding of optimizing the nutrient medium to study their production. The present study aims to investigate the effects of iron, phosphate, and salinity concentrations by working synergically in a nutrient medium on the growth responses, pigments, and lipid accumulation of Chlorella sp. culture using a response surface methodology (RSM) approach. Using the result from the RSM software, a total of 18 experimental groups (E1 – E18) were evaluated, and one confirmation (C) study was conducted. The results revealed that the E7 experiment in Chlorella sp. culture provided the highest cell density and specific growth rate (SGR) with 176.00 × 106 cells mL−1 and 0.35 day−1, respectively. Similarly, the E5 and E1 experiments produced the highest cell density of 166.10 × 106 cells. mL−1 and 152.13 × 106 cells mL−1, respectively. The SGR was also increased at 0.33 day−1 in the E5 experiment and 0.33 day−1 in the E1 experiment. Consequently, the culture of Chlorella sp. containing high iron and phosphate concentrations and lower salinity in a nutrient medium had the highest number of cells, SGR, and pigment accumulation (chlorophyll a and total carotenoid). In addition, the presence of high salinity concentrations reduces Chlorella sp. growth. However, the increase in the growth of Chlorella sp. culture did not indicate an increase in other biochemical compositions. In some cases, biochemical compositions are high due to nutritional limitations or stress factors. For example, in pigment accumulation, chlorophyll a pigment accumulation was increased in experiment E7 (51.57 μg mL−1), while total carotenoid accumulation was increased in experiment E8 (20.68 μg mL−1). In addition, increasing salinity concentration increased chlorophyll a and total carotenoid contents per cell, but decreased Chlorella sp. growth as shown in the E4 experiment, which achieved chlorophyll a levels of 1.38 pg cell−1 and total carotenoid levels of 0.52 pg cell−1. Furthermore, Chlorella sp. culture produces a higher lipid accumulation of 37.38 % in the E3 experiment. Hence, the results of this study contribute to understanding the optimal biochemical composition and cell growth of Chlorella sp. cultures.