Saline Water Sources Research Articles

Effect of Super Absorbent Polymer and Irrigation Deficit on Water Use Efficiency, Growth and Yield of Cotton

Sustainable use of water resources in agriculture is a necessity for many arid countries. In order to investigate the effect of water deficit, irrigation after 120 (control), 155 (moderate water stress) and 190 mm (sever water stress) pan evaporation and super absorbent polymer rates (SAP) (0, 30, 60 and 90 kg ha-1) on growth, yield and water use efficiency of cotton, an experiment was conducted as split plot based on a randomized complete block design with three replications. Moreover, the effect of water quality (distilled water and solutions of 0.25, 0.5, 0.75, 1 and 1.25% NaCl) was investigated on water holding capacity by SAP. Results revealed that moderate water stress (irrigation intervals of aprox. 15 days) along with 60 kg ha-1 SAP application was the best treatment in terms of growth and yield indices of cotton. The results for plant height, plant dry weight, boll number per plant and fiber yield in this treatment were 16, 28, 42 and 10% higher than control treatment, respectively. Water deficit and SAP application improved the water use efficiency (WUE) of cotton. The amount of WUE in moderate water stress treatment along with consumption of 60 or 90 kg ha-1 SAP was 26% higher than for control treatment. In addition, water holding capacity by SAP in distilled water treatment was 7 times higher than in the case of 1.25% NaCl solution. The overall results showed that irrigation deficit and SAP application are two appropriate strategies for crop production in areas affected by drought stress, especially if low saline water sources are used.

Effect of Super Absorbent Polymer and Irrigation Deficit on Water Use Efficiency, Growth and Yield of Cotton

Sustainable use of water resources in agriculture is a necessity for many arid countries. In order to investigate the effect of water deficit, irrigation after 120 (control), 155 (moderate water stress) and 190 mm (sever water stress) pan evaporation and super absorbent polymer rates (SAP) (0, 30, 60 and 90 kg ha-1) on growth, yield and water use efficiency of cotton, an experiment was conducted as split plot based on a randomized complete block design with three replications. Moreover, the effect of water quality (distilled water and solutions of 0.25, 0.5, 0.75, 1 and 1.25% NaCl) was investigated on water holding capacity by SAP. Results revealed that moderate water stress (irrigation intervals of aprox. 15 days) along with 60 kg ha-1 SAP application was the best treatment in terms of growth and yield indices of cotton. The results for plant height, plant dry weight, boll number per plant and fiber yield in this treatment were 16, 28, 42 and 10% higher than control treatment, respectively. Water deficit and SAP application improved the water use efficiency (WUE) of cotton. The amount of WUE in moderate water stress treatment along with consumption of 60 or 90 kg ha-1 SAP was 26% higher than for control treatment. In addition, water holding capacity by SAP in distilled water treatment was 7 times higher than in the case of 1.25% NaCl solution. The overall results showed that irrigation deficit and SAP application are two appropriate strategies for crop production in areas affected by drought stress, especially if low saline water sources are used.

Modeling sorghum response to irrigation water salinity at early growth stage

Agricultural water management in arid and semi-arid regions largely depends on availability and quality of irrigation water at different plant growth stages. In saline environments, plant response to salinity varies at different growth stages. Information on plant response to salinity at various growth stages can be used in managing saline waters for irrigation. This study was conducted to quantitatively assess response of sorghum (Sorghum bicolor L. Moench) to salinity at seedling stage. Consequently, an extensive experiment in natural saline sandy loam soil with five natural saline water treatments including 4, 6, 8, 10, and 12dS/m was conducted. The reason for selecting natural sources of saline water and a saline soil was to minimize deviations from natural conditions under which sorghum grows. Sorghum seeds were planted and seedles counted at 24h time intervals. The macroscopic models of Maas and Hoffman, van Genuchten and Hoffman, Dirksen et al., and Homaee et al. were used to predict relative seedlings at different salinity levels. The obtained results indicated that salinity threshold value EC* for sorghum at seedling stage is 1dS/m and the seedling rate reduces to 50 percent at 11dS/m of soil salinity. All evaluated models overestimated the EC* value. Calculated statistics indicated that the nonlinear salinity models are more accurate than the linear model. Among those, Homaee et al. model provided better predictions at seedling growth stage.

Energy Efficient and Environmentally Friendly Console Desalination Plant with Low Temperature Distillation

This article describes the console plant for desalination of saline water, which uses a quasi-adiabatic process with difference of the water temperature lower than 5 °C. That provides ecological safety when the seawater is used as a source of saline water. The main element of the installation is a patented heat mass transfer device with a huge surface area of contact. Only a small portion of saline water flows through device, which can be pre bactericidal treated, such as of quartz. In this case, the cold of the desalination plant can be utilized that allows using this cooled and dehumidified air for air conditioning. The article presents a thermodynamic diagram processing air and block diagram of this desalination plant, and an analysis of similar devices for desalination.

The use of fresh and saline water sources by the mangrove Avicennia marina

Mangroves are distributed along tropical and subtropical riverine and coastal shores. Although mangroves are highly adapted to saline environments, maintaining water uptake under saline conditions is energetically expensive. Therefore, salinity is a lim- iting factor for mangrove growth and productivity, and access to fresh water sources, such as rainwater and groundwater, which reduce water salinity, increase mangrove ecosystem productivity. Here, we investi- gated the extent of fresh water utilization by man- groves to better predict current and future mangrove productivity. We used the abundance of 18 O isotope in stem water to assess: (1) the extent of fresh water utilization by Avicennia marina (Forssk.) Vierh across hydrological settings; and (2) whether growth, mea- sured as increments in stem circumference, is sensitive to variation in rainfall availability. The d 18 O isotopic composition of stem water indicated mangroves use both fresh and saline water sources for metabolic processes. However, our results suggest that the proportion of fresh water used by mangroves increases with the availability of fresh water. Growth of the main stems of trees was correlated with rainfall (r 2 = 0.34 and r 2 = 0.37, P = 0.001). Our results

Autonomous operation and maintenance of small-scale PVRO systems for remote communities

Solar-powered reverse osmosis desalination (Photovoltaic-powered reverse osmosis [PVRO]) is a technically feasible method of providing fresh water to many remote communities with saline water sources. To be practical, these systems must be well operated and maintained by non-experts. Their productivity is a complex function of their locations, water chemistry and demand, and the solar radiation history at their locations, which is quite variable with time. A key aspect of the maintenance program is the cleaning of the reverse osmosis (RO) membranes, including system flushing and chemical cleaning. Guidelines for cleaning from membrane manufacturers do not consider the complex, variable operating conditions for these small solar-powered systems. Local operators do not have the expertise to determine how and when cleaning should be done. While cleaning will generally improve clean water production, it is costly, requires the system to be shut down, and uses some of the clean water produced. Here, simple, physics-based models of RO membrane fouling and remediation are used to find maintenance schedules that maximize water produced by a small-scale PVRO system under deterministic conditions, such as found in large RO plants using conventional grid power. However, it is shown that for small PVRO systems working in remote locations, the large uncertainties have a significant impact on optimal cleaning schedules.

Sources and doses of nitrogen in the production of sunflower plants irrigated with saline water

ABSTRACT The cultivation of sunflower allows its use as bio-fuel and alternative forage. It is a viable alternative in the semiarid regions. Current study evaluates the effect of saline water use, sources and doses of nitrogen fertilization on the production of sunflower in the experiment conducted in drainage lysimeters between May and August 2012, under protected conditions, at Pombal - PB Brazil. The experiment consisted of a randomized block design, with a 2 x 3 x 4 factorial arrangement and three replications. The treatments consisted of two levels of electrical conductivity of water - ECw (0.3 and 3.0 dS m-1), three sources of nitrogen (urea, ammonium sulfate and calcium nitrate) and four levels of N (40, 80, 120 and 160% of recommended dose - 100 mg kg-1, for trials in pots). Dry mass of chapter (DMC), mass of achenes (MAc), the number of viable seeds (MVS), total number of seeds (TNS) and internal (DCI) and external (DCE) diameter of chapter. Irrigation with water of ECw=3.0 dS m-1 negatively affected all variable evaluated. Doses of N 104 and 160% of recommended dose for trials in pots, resulted in the highest DMC, TNS, DCE and DCI. N sources and the interaction between factors did not affect significantly any of the variable evaluated.

Paragenetic sequences of carbonate and sulphide minerals of the Mamfe Basin (Cameroon): Indicators of palaeo-fluids, palaeo-oxygen levels and diagenetic zones

The occurrence of evaporite minerals in the Mamfe Basin (Albian–Cenomanian) is considered to be an indicator of aridity and palaeo-saline waters. A detailed lithostratigraphic analysis of the Mamfe sedimentary basin-fill indicates the occurrence of carbonate and sulphide minerals in close association with halite and gypsum within the Manyu, Mamfe and Bagba Members of the Nfaitok Formation. The composition and textures of these carbonate and sulphide minerals were studied using the Scanning Electron Microscope (SEM), attached to Energy Dispersive Atomic X-ray analyser (EDAX) that generates Backscattered and Secondary Electron Imaging (BSEI). Two paragenetic suites were encountered in this study; calcite/dolomite/ankerite/siderite and pyrite/sphalerite/galena respectively. The compositional and textural variability of different suite members appear to be conditioned by the competition for CO32- and SO42- anions by metal cations with respect to redox conditions and diagenetic stages. Early formed authigenic minerals exhibit euhedral textures, while late diagenetic minerals exhibit pseudomorphic textures, as cations with higher ionic radii integrate into earlier structures. Calcite is a precursor for dolomite, ankerite and siderite at late diagenetic stages. Pyrite, sphalerite and galena indicate deposition in anoxic and sulphate reducing environments. Micron-sized euhedral pyrite framboids are syn-depositional, while Pb–Zn mineralization in voids and cavities are formed at late diagenetic stages below the sulphate reduction zone (SRZ), where siderite forms encrustations around skeletal pyrite. The pristine source of saline water, SO42- and Mg2+ could be related to sea water splay into a lagoon. The source of Fe2+ is detrital, while Zn2+ and Pb2+ indicate metalliferous fluids with high heat flux, probably of hydrothermal origin.

Calcium, magnesium and strontium cycling in stratified, hardwater lakes: Lake Kinneret (Sea of Galilee), Israel

In stratified hardwater lakes, calcite crystallization in the epilimnion and partial dissolution in the hypolimnion play important roles in the cycling of Ca2+ in the water column. Mg2+ and Sr2+ coprecipitate with this mineral, to be released together with Ca2+ upon its dissolution. Here, we focus on Lake Kinneret (Sea of Galilee, Israel), a stratified, warm, hardwater lake, searching for an interpretable, high resolution picture of the processes that drive Ca2+, Mg2+ and Sr2+cycling in this and similar lakes elsewhere.In total, 1428 water samples were collected from the lake, and another 81 samples were collected from the Jordan River and two small streams discharging into it, covering a full monomictic cycle from December 2001 through March 2003. Particulate material was retrieved from sediment traps in the hypolimnion. The water samples were analyzed for Na+, K+, Mg2+, Ca2+, Sr2+, Cl−, SO42−, HCO3− and Br−, and the trapped particulates were examined under SEM and analyzed for their Ca, Mg, and Sr content. Individual calcite crystals within the particulate material underwent LA-ICP-MS analysis for Ca, Mg, and Sr.Downward transport of Ca2+ involves crystallization of calcite in the epilimnion, followed by its settling through the water column, followed by its partial dissolution in the hypolimnion. Magnesium and Sr2+ follow Ca2+ by coprecipitation in calcite and are released upon its dissolution in the hypolimnion. Upward cycling of the three solutes occurs through an admixture of the hypolimnetic water into the epilimnion during thermocline deepening, terminated by overturn of the lake.Removal rates of Mg2+ and Sr2+ from the lake, relative to that of Ca2+, and the water–calcite distribution coefficients, DMg and DSr, were calculated from the analyses using: (1) epilimnion water and ‘bulk’ particulates; (2) epilimnion water only; and (3) epilimnion water and calcite crystals in the particulates. The DSr values obtained were internally consistent (0.194±5.9%, 0.22–0.28, and 0.204–0.232, respectively); however, the DMg value for the ‘bulk’ particulates (0.0477) was ∼6 times higher than that corresponding to calcite crystals included therein (0.00841). This difference is attributed to phytoplankton debris in the ‘bulk’ particulates and should be of concern to geochemists using Mg/Ca ratios in limestone to reconstruct ancient aquatic environments.The cycling of Ca2+, Mg2+ and Sr2+ in the stratified lake is monitored by Mg/Ca vs. Sr/Ca regression diagrams, where each line represents the water column composition on a specific date. The distance of the data points from the initial (mixed lake) coordinates reflects the fractionation of Ca2+, Mg2+ and Sr2+ after the onset of stratification. The regression lines rotate in an orderly anticlockwise direction in response to the high calcite flux from the epilimnion in spring and the higher rate of Mg2+ replenishment than that of Sr2+, compensating for their loss in calcite. The release of Mg2+ and Sr2+ from dissolving calcite in the hypolimnion, at an Mg/Sr ratio (7.5eq/eq) much lower than that in the surrounding water (∼160eq/eq), lends additional support to the anticlockwise rotation. Reversal of rotation occurs in summer, when calcite crystallization and the freshwater supply slow down, and brackish and saline water sources take control over the Mg/Sr ratio in the lake. Subsequent turnover and mixing of the lake in winter reset the Mg/Ca and Sr/Ca ratios to their original values before the next stratification.

Factors controlling mechanisms of groundwater salinization and hydrogeochemical processes in the Quaternary aquifer of the Eastern Nile Delta, Egypt

In this study, combining interpretations of conservative dissolved ions and environmental isotopes in water were used to investigate the main factors and mechanisms controlling groundwater salinization and hydrogeochemical processes in the Eastern Nile Delta, Egypt. Hydrogeochemical and isotopic study has been carried out for 61 water samples from the study area. Total dissolved solid (TDS) contents of groundwater are highly variable rising along flowpath from the south (410 mg/L) to the north (14,784 mg/L), implying significant deterioration and salinization of groundwater. Based on TDS and ionic ratios, groundwater samples were classified into three groups. In low-saline groups, water chemistry is greatly influenced by cation exchange, mineral dissolution/precipitation, anthropogenic pollutants and mixing with surface water. Whilst, in high-saline groups, water chemistry is affected by salt-water intrusion, reverse cation exchange and evaporation. The chemical constituents originating from saline water sources, reverse ion exchange and mineral dissolution are successfully differentiated using ionic delta and saturation index approaches. The δ18O–δ2H relationship plots on a typical evaporation line, suggesting potential evaporation of the recharging water prior to infiltration. Isotope evidence concludes that the groundwater have been considerably formed by mixing between depleted meteoric water recharged under different climatic conditions and recently infiltrating enriched surface water and excess of irrigation water. The δ18O data in conjunction with chloride concentrations provide firm evidence for impact of dissolution of marine-origin evaporite deposits, during past geologic periods, on groundwater salinity in the northern region. Moreover, the relation between 14C activities and Cl− concentration confirms this hypothesis.

On the simulation of temperature and salinity fields in the Arctic Ocean

This paper considers the formation of the thermohaline structure of the Arctic Ocean: the formation of the salinity field and a freshwater reservoir in the Beaufort Sea and the transport of warm Atlantic water into the central part of the Arctic Ocean. A new version of the Finite Element Model of the Arctic Ocean (FEMAO) with a low spatial resolution is used. The main distinctions of this version are the following features: a new equation of state, a more sophisticated parameterization of vertical turbulence, modified formulations for the boundary conditions on open boundaries (using satellite data on the sea level) and at the upper boundary of the ocean, and the use of a variable eddy diffusivity in the parameterization of the eddy transport of a scalar. Our experiments indicated that the use of the parameterization of the eddy transport of a scalar enhances the transport of warm Atlantic waters to the central part of the Arctic Ocean through the Fram Strait; the results are most realistic when a variable coefficient is used. The Neptune effect has a contradictory role and, in the future, a higher spatial resolution should be used instead of this parameterization. We revealed that a key factor in the thermohaline fields on a large time scale is the interaction with the Atlantic Ocean, which is the source of heat and saline water.

Fertiliser drawn forward osmosis desalination: the concept, performance and limitations for fertigation

With the world’s population growing rapidly, pressure is increasing on the limited fresh water resources. Membrane technology could play a vital role in solving the water scarcity issues through alternative sources such as saline water sources and wastewater reclamation. The current generation of membrane technologies, particularly reverse osmosis (RO), has significantly improved in performance. However, RO desalination is still energy intensive and any effort to improve energy efficiency increases total cost of the product water. Since energy, environment and climate change issues are all inter-related, desalination for large-scale irrigation requires new novel technologies that address the energy issues. Forward osmosis (FO) is an emerging membrane technology. However, FO desalination for potable water is still a challenge because, recovery and regeneration of draw solutes require additional processes and energy. This article focuses on the application of FO desalination for non-potable irrigation where maximum water is required. In this concept of fertiliser drawn FO (FDFO) desalination, fertilisers are used as draw solutions (DS). The diluted draw solution after desalination can be directly applied for fertigation without the need for recovery and regeneration of DS. FDFO desalination can make irrigation water available at comparatively lower energy than the current desalination technologies. As a low energy technology, FDFO can be easily powered by renewable energy sources and therefore suitable for inland and remote applications. This article outlines the concept of FDFO desalination and critically evaluates the scope and limitations of this technology for fertigation, including suggestions on options to overcome some of these limitations.

Forward osmosis for applications in sustainable energy development

Forward osmosis (FO) provides a method of harvesting the osmotic potential difference between fresh and saline waters to produce electricity. FO occurs when fresh water and saline water are placed on opposite sides of a semi-permeable membrane. When this occurs water naturally flows from the freshwater side of the membrane to the saline side. This water flux continues until the osmotic pressure difference on both sides of the membrane equalize. The water flux will cause the pressure to increase in the saline water. If the saline water is seawater the pressure can reach as high as 410 psi. This pressure can be harvested as hydraulic power, similar to that of a hydroelectric dam. Such a system is called pressure retarded forward osmosis (PRO) and it can be used anywhere fresh water mixes with saline water. The worldwide potential energy of this resource, based on locations where rivers mix with oceans, is reported to be in excess of 1600 tera-watt-hour (TWH) per year [1]. In arid regions, such as California, where few major rivers reach the ocean, the ap¬plicability of PRO is limited. In these regions it makes sense to look for alternative sources of fresh water. This project evaluates an approach where, rather than siteing a PRO power plant in ways that potentially impact sensitive costal environments, they are sited at wastewater treatment plants that discharge into the ocean or other sources of saline water and are effective in a comprehensive environmental management and design role. Electricity can then be generated from the mixing of the treatment plants outfall and seawater while providing a high level of additional treatment and environmental protection. In the state of California alone, 1,350 million gallons per day of treated municipal wastewater is discharged into the Pacific Ocean. Using PRO this represents about a 26 megawatt resource. In addition to the electricity produced, the PRO also provides tertiary treat¬ment of the wastewater treatment plant’s outfall. It is comparable to treatment with reverse osmosis membranes. The combination of PRO and tertiary treatment (PRO/TT) provides the mutual benefit of sustainable power production and advanced wastewater treatment. This is particularly important in locations where regulation is requiring treatment plants to tertiary treat wastewater. PRO/TT can be used to offset the cost of providing treatment by generating electricity that can be sold for profit or used to help power the treatment plant.

Production of Freshwater and Energy from Earth’s Atmosphere

The author offers a new, cheap method for the extraction of freshwater from the Earth’s atmosphere. The suggested method is fundamentally dictinct from all existing methods that extract freshwater from air. All other industrial methods extract water from a saline water source (in most cases from seawater). This new method may be used at any point in the Earth except the Polar Zones. It does not require long-distance freshwater transportation. If seawater is not utilized for increasing its productivity, this inexpensive new method is very environmentally-friendly. The author’s method has two working versions: 1) In the first variant warm (or hot) atmospheric air is lifted by the inflatable tube in a high altitude and atmospheric water vapor is condensed into freshwater: 2) in the second version, the warm air is pumped 20-30 meters under the sea-surface. In the first version, wind and solar heating of air are used for causing air flow. In version 2) wind and fans are used for causing air movment. The first method does not need energy, the second needs a small amount. Moreover, in variant 1) the freshwater has a high pressure (> 30 or more atm) and can be used for production of energy such as electricity and in that way the freshwater cost is lower. For increasing the productivity the seawater is injected into air and a solar air heater may be used. The solar air heater produces a huge amount of electricity as a very powerful electrical generation plant. The offered electricity installation is 100 - 200 times cheaper than any common electric plant of equivalent output.

The challenge of predicting groundwater quality impacts in a CO2 leakage scenario: Results from field, laboratory, and modeling studies at a natural analog site in New Mexico, USA

Abstract A vital aspect to public and regulatory acceptance of carbon sequestration is assurance that groundwater resources will be protected. Theoretical and laboratory studies can, to some extent, be used to predict the consequences of leakage. However, direct observations of CO 2 flowing through shallow drinking water aquifers are invaluable for informing credible risk assessments. To this end, we have sampled shallow wells in a natural analog site in New Mexico, USA, where CO 2 from natural sources is upwelling from depth. We collected major ion, trace element, and isotopic ( 3 H, 18 O, and Sr) data and, coupled with laboratory experiments and reactive transport modeling, have concluded that the major control on groundwater quality at this site is not chemical reaction of CO 2 with the aquifer but intrusion of saline waters upwelling with the CO 2 . Using reactive transport modeling based on field data, we show the difference in reactivity of the CO 2 and CO 2 /saline water source terms, particularly with respect to carbonate mineralogy. Sr isotopes were used to investigate whether aquifer waters were affected by carbonate mineral reaction with CO 2 or by saline water intrusion. Preliminary data suggest that Sr isotopes can successfully be used to discriminate between the two types of source terms at Chimayo; this technique shows promise for monitoring CCS sites. In developing predictive capabilities for future sites, it is critical to identify the solid phases and specific reactions controlling dissolved trace metal concentrations in both the presence and absence of CO 2 . We have conducted laboratory experiments to identify these phases and have found that some elements (e.g., U, Ca) are largely controlled by ion exchange and/or carbonate minerals. In the experiments, the concentration of some metals increases after exposure to CO 2 (although concentrations remain below the U.S. EPA primary drinking water standards); we are currently extending these experiments to determine if the reactions causing the increase are reversible and, if so, on what time scales. Metal scavenging by secondary mineral precipitation, as observed at other natural analog sites, may be important at certain temporal scales. We are using the information gained from this field and laboratory study to develop predictive models for application to risk assessment at future CCS sites. The models will be particularly useful in identifying the temporal and spatial scales of water quality changes and in developing possible mitigation strategies in the case of leaks at engineered CCS sites.

The potential of blue energy for reducing emissions of CO2 and non-CO2 greenhouse gases

Salinity gradient power (or blue energy) is a renewable energy source mentioned in the literature since the 1950s. It refers to the production of electricity by mixing of two solutions with different salt concentrations, for example river and sea water. The global potential of salinity power has been estimated in the 1970s as substantial, but the state of membrane technology at that time – crucial for energy recovery – did not permit the practical use of this resource. More recently, the interest in salinity power has been growing because of the need for carbon neutral, renewable sources of electricity. This study aims to assess the potential of salinity-gradient power for reducing emissions of CO2 and non-CO2 greenhouse gases. First, we discuss the global technical potential for blue energy, i.e. the maximum amount of energy that could be retrieved at the current state of technology. We focus on rivers as source of fresh water and seas as source of saline water. The analysis is based on global datasets of annual river discharges for more than 5000 world rivers. The resulting estimates of global and regional potentials for salinity gradient power are used to estimate the potential for reducing greenhouse gases, assuming that salinity power would reduce the need for fossil fuels. The results are shown for global totals, regional totals and selected rivers.

Spatial distribution of saline water and possible sources of intrusion into a tropical freshwater lagoon and the transitional effects on the lacustrine ichthyofaunal diversity

The spatial distribution of saline water and possible sources of intrusion into Lekki lagoon and transitional effects on the lacustrine ichthyofaunal characteristics were studied during March, 2006 and February, 2008. The water quality analysis indicated that, salinity has drastically increased recently in the lagoon (0.007 to 4.70%). This study has identified three possible sources for saline water intrusion, beyond the seasonal input from the two adjacent lagoons (Lagos and Mahin), salt water intrusion by subsurface flow through the barrier beach from the ocean, and leaching of ions through lagoon bottom sediments. Eighty one fish species belonging to 40 families, 56 genera and 14 orders encountered were mostly freshwater, euryhaline and marine species adapted to life in the lagoon. The shell fish included the freshwater prawns Macrobrachium spp and the portunid crab Callinectes amnicola . This high number of fish species recorded from Lekki Lagoon in this study has confirmed the fact that this lagoon is a transition area between brackish water (Lagos Lagoon and Mahin Creek) and freshwater (Rivers Saga and Oshun). Key words: Spatial distribution, saline water, lacustrine, ichthyofaunal, diversity.

Recent developments in reverse osmosis desalination membranes

Reverse osmosis (RO) desalination is one of the main technologies for producing fresh water from seawater and other saline water sources. The membrane properties greatly affect the water productivity and energy costs in the reverse osmosis desalinatin processes. Recent years have seen significant research efforts devoted to developing high-performance RO membranes. This article reviews recent activities in the development of RO membranes with improved flux and salt rejection, chlorine tolerance, fouling resistance and thermal stability. In particular, this review mainly focuses on the modification of current polymeric membrane materials, and synthesis and separation performance of new polymer membranes, inorganic membranes and mixed matrix membranes.

Characterization of salt-water intrusion in the lower Esino Valley, Italy using a three-dimensional numerical model

A seawater-intrusion study was conducted at an oil-refinery site located on the coast in the lower Esino Valley, Italy. A steady-state density-dependent flow model was used in order to understand the position of the freshwater/salt-water interface, as influenced by the hydrogeologic structure and the presence of industrial activities and a river. Collected data and model results showed that in a large part of the area, the salt-water interface is steep and can penetrate only a few meters inland. On the other hand, close to the river mouth, seawater represents the main saline source for the aquifer. The river, in connection with the sea, can enhance seawater encroachment into the coastal aquifer; a long-term survey of river level and chloride concentrations in groundwater is recommended to further improve the physical model and to obtain a better calibration. At the refinery site, two “secondary” sources of saline water were identified and were demonstrated to have had a great influence on the presence of brackish waters in the unconfined aquifer: leakage from the fire-extinguishing system (network of pipes containing seawater) and rough sea events. This confirmed that groundwater contamination by chloride can result from means other than seawater intrusion.

Geochemical process regulating groundwater quality in a coastal region with complex contamination sources: Barka, Sultanate of Oman

An investigation was carried out to evaluate the geochemical processes regulating groundwater quality in a coastal region, Barka, Sultanate of Oman. The rapid urban developments in Barka cause depletion of groundwater quantity and deterioration of quality through excessive consumption and influx of pollutants from natural and anthropogenic activities. In this study, 111 groundwater samples were collected from 79 wells and analysed for pH, EC, DO, temperature, major ions, silica and nutrients. In Barka, water chemistry shows large variation in major ion concentrations and in electrical conductivity, and implies the influence of distinguished contamination sources and hydrogeochemical processes. The groundwater chemistry in Barka is principally regulated by saline sources, reverse ion exchange, anthropogenic pollutants and mineral dissolution/precipitation reactions. Due to ubiquitous pollutants and processes, groundwater samples were classified into two groups based on electrical conductivity. In group1, water chemistry is greatly influenced by mineral dissolution/precipitation process and lateral recharge from upstream region (Jabal Al-Akdar and Nakhal mountains). In group 2, the water chemistry is affected by saline water intrusion, sea spray, reverse ion exchange and anthropogenic pollutants. Besides, high nitrate concentrations, especially in group 2 samples, firm evidence for impact of anthropogenic activities on groundwater quality, and nitrate can be originated by the effluents recharge from surface contamination sources. Ionic ratios such as SO4/Cl, alkalinity/Cl and total cation/Cl indicate that effluents recharged from septic tank, waste dumping sites and irrigation return flow induce dissolution of carbonate minerals, and enhances solute load in groundwater. The chemical constituents originating from saline water sources, reverse ion exchange and mineral dissolution are successfully differentiated using ionic delta, the difference between the actual concentration of each constituent and its theoretical concentration for a freshwater–seawater mix calculated from the chloride concentration of the sample, and proved that this approach is a promising tool to identify and differentiate the geochemical processes in coastal region. Hence, both regular geochemical methods and ionic delta ensured that groundwater quality in Barka is impaired by natural and human activities.