Perceptions and Acceptance of Desalinated Seawater for Irrigation: A Case Study in the Níjar District (Southeast Spain)

In the context of increasing demand for irrigation water—but, at the same time, with the constraints in the supply from traditional resources—desalinated seawater has been recognized as one of the alternative sources of water to increase the supply for agricultural irrigation. However, its use among farmers has not yet started to expand. Policy makers need to understand what is causing the low acceptance levels of farmers, and how their attitudes could be improved. This is the first study that has conducted an analysis of farmers’ perceptions and acceptance of the use of desalinated seawater for irrigation. The study is based on collected data from a survey completed by farmers in southeastern Spain who do not use desalinated seawater. The main results indicate that desalinated seawater as a water supply source has the lowest acceptance level for farmers. Barriers for its use are price, the need for additional fertilization, and the perception that it would negatively affect the yield and crop quality. The farmers’ general level of knowledge about the impact of using desalinated seawater in agriculture is extremely low. Furthermore, farmers consider it a priority that their startup investment should be subsidized and that water prices should be reduced. Based on the study findings, this paper makes recommendations for the decision-making process in order to improve farmers’ acceptance levels

Mitigation of corrosion attack on carbon steel coated cermet alloy in different anion contents

This research study evaluated the corrosion mechanism attack on carbon steel coated with cermet alloys (WC9% Ni) in seawater at different sulphate-to-chloride ratios. The four different sulphate-to-chloride ratios were synthesised with the same seawater salinity of 3.5 % and same pH of real seawater. The corrosion tests involved immersion and electrochemical tests. The immersion test is used to determine the cermet coating ability to withstand the corrosion attack based on different ratios of anions present in the seawater at different periods of immersion. The corrosion attack was characterized by optical and Scanning Electron Microscopy (SEM). The aggressive anions present in the seawater influenced the corrosion attack on the cermet coating. For immersion test, results revealed that increasing sulphate more than chloride, increased the weight loss of cermets. The electrochemistry analysis showed that the passive layer forms on cermet coating prevented the material from further corrosion attack. However, due to its porosity, the passive layer collapsed and exposed the material for other corrosion reaction. For electrochemical test, the result shows that the solution with sulphate-to-chloride ratio of 0.14 (real seawater) has the highest corrosion current and Open Circuit Potential (OCP) compared to other solutions (different sulphate-to-chloride ratio). In conclusion, sulfate and chloride show their competition to attack the cermet coating on carbon steel and the higher the amount of chloride present in seawater, the higher the corrosion rate and pits formed on the cermet coating

Properties of plain concrete produced employing recycled aggregates and sea water

The final publication is available at Springer via http://dx.doi.org/10.1007/s40999-017-0229-0The generation of construction and demolition waste (C&DW) is a noteworthy environmental and economic concern. The development of new applications in which Recycled Mixed Aggregates (RMA) can be used will lead to a reduction of landfills growth. Moreover, the use of seawater shall represent another advance in sustainability due to the consequent reduction of fresh water consumption, which can be a limited resource in certain areas. Although seawater is not generally recommended for concrete production, especially in reinforced concretes, seawater could be a viable replacement for fresh water in the production of plain concretes. This study intends to analyse the possibility of using RMA and seawater in the production of concrete to be used in port sites. This study is based on three different parameters: cement class, water source and RMA content. The results highlighted the beneficial effects of using type III cement, especially with regard to durability properties. The concretes produced employing RMA and type III cement achieved lower value of sorptivity coefficient and higher values of ultrasonic pulse velocity (UPV), chloride ion penetration resistance and electrical resistivity than those produced with natural aggregates and type I cement. Moreover, the use of seawater in concretes with type III cement not only produced higher density and lower absorption capacity but also higher mechanical properties by creating a denser cement matrix, which proved to suffer low decrease by RMA addition.Peer ReviewedPostprint (author's final draft

The Effect of Water Quality Characteristics on Cavitation Noise

This study investigated the effects of seawater on cavitation noise using a water jet test, a two-dimensional wing test, and a three-dimensional wing test. A model propeller cavitation test was conducted in a cavitation tunnel using seawater, in order to determine the effects of propeller cavitation more precisely. In the cavitation tests, measured propeller performance for both cavitation noise inception and desinence, as well as the cavitation noise spectrum (see, for example, figure 7). On the basis of the results of the present propeller cavitation test and tests that were carried out previously, we discuss how to control the water quality in the cavitation tunnel to reproduce the cavitation phenomena, especially cavitation noise, in seawater (see, for example, figure 9)

Fluorescence spectroscopy applied to the optimisation of a desalting step by electrodialysis for the characterisation of marine organic matter

The isolation and characterisation of marine dissolved organic matter (DOM) are still not readily achieved today. The study of this chemically complex material is particularly difficult, especially as it is hindered by the high salinity of seawater. It is therefore essential to develop a method in which a sufficient quantity of marine organic matter can be collected for structural analyses. Reverse osmosis (RO) is often used for the concentration of DOM from freshwaters, due to the fact that DOM is not modified during RO and that DOC recoveries are high (about 80%). Unfortunately, RO cannot be used directly to isolate marine DOM,since both salts and organic matter are concentrated during the process. Therefore, marine samples have to be desalted before their concentration by RO. Our aim was to develop a desalting step of seawater by electrodialysis (ED), whilst minimising DOM modifications and losses. The process was first developed with small volumes (2 L) of artificial and Mediterranean seawater and was then applied to larger volumes.We showed that 20 L of Mediterranean seawater could be rapidly desalted (in less than 7 h) and, by monitoring the quality of DOM in desalted subsamples collected during ED using spectrofluorometry, that the quality of DOM was not significantly modified. It was concluded that desalted samples were still representative of the initial seawater samples. It should be noted, however, that care has to be taken in choosing the ratio of the volume of water to be desalted over the membrane surface area in order to limit DOM modifications and losses. Electrodialysis efficiently removed up to 75% of the salts present in the seawater samples whilst recovering most of unaltered DOM. ED and RO could then be combined in order to isolate, concentrate and characterise marine organic matter

The use of algorithms to predict surface seawater dimethyl sulphide concentrations in the SE Pacific, a region of steep gradients in primary productivity, biomass and mixed layer depth

Dimethyl sulphide (DMS) is an important precursor of cloud condensation nuclei (CCN), particularly in the remote marine atmosphere. The SE Pacific is consistently covered with a persistent stratocumulus layer that increases the albedo over this large area. It is not certain whether the source of CCN to these clouds is natural and oceanic or anthropogenic and terrestrial. This unknown currently limits our ability to reliably model either the cloud behaviour or the oceanic heat budget of the region. In order to better constrain the marine source of CCN, it is necessary to have an improved understanding of the sea-air flux of DMS. Of the factors that govern the magnitude of this flux, the greatest unknown is the surface seawater DMS concentration. In the study area, there is a paucity of such data, although previous measurements suggest that the concentration can be substantially variable. In order to overcome such data scarcity, a number of climatologies and algorithms have been devised in the last decade to predict seawater DMS. Here we test some of these in the SE Pacific by comparing predictions with measurements of surface seawater made during the Vamos Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) in October and November of 2008. We conclude that none of the existing algorithms reproduce local variability in seawater DMS in this region very well. From these findings, we recommend the best algorithm choice for the SE Pacific and suggest lines of investigation for future work

Key physicochemical characteristics governing organic micropollutant adsorption and transport in ion-exchange membranes during reverse electrodialysis

The co-generation of electricity and electrodialysis of seawater in a hybrid system is a promising approach to overcome water scarcity. Reverse electrodialysis harvests energy from the salinity gradient, where seawater is used as a high salinity stream while secondary treated wastewater can be used as a sustainable low salinity stream. Treated wastewater contains organic micropollutants, which can be transported to the seawater stream. The current research establishes a connection between adsorption and transport of organic micropollutants in ion exchange membranes, using a cross-flow stack in adsorption and zero-current experiments. To mimic the composition of treated wastewater, a mixture of nineteen organic micropollutants of varied physicochemical characteristics (e.g. size, charge, polarity, hydrogen donor/acceptor count, hydrophobicity) at environmentally relevant concentrations was used. Depending on the charge, micropollutants develop different types of mechanisms responsible for short-distance interactions with ion-exchange membranes, which has a direct influence in their transport behavior. This study provides a rational basis for the optimization/design of next-generation ion-exchange membranes, in which the permeability toward organic micropollutants should be also included. This investigation highly contributes to understanding the potential hazard posed by organic micropollutants in reverse electrodialysis in seawater desalination systems, where treated wastewater is used as a low salinity stream

Effects of low seawater pH on the marine polychaete Platynereis dumerilii

An important priority for any organism is to maintain internal cellular homeostasis including acidbase balance. Yet, the molecular level impacts of changing environmental conditions, such as low pH, remain uncharacterised. Herein, we isolate partial Na+/H+ exchangers (NHE), carbonic anhydrase (CA), and calmodulin (CaM) genes from a polychaete, Platynereis dumerilii and investigate their relative expression in acidified seawater conditions. mRNA expression of NHE was significantly down-regulated after 1 h and up-regulated after 7 days under low pH treatment (pH 7.8), indicating changes in acid-base transport. Furthermore, the localisation of NHE expression was also altered. A trend of down regulation in CA after 1 h was also observed, suggesting a shift in the CO2 and HCO3- balance. No change in CaM expression was detected after 7 days exposure to acidified seawater. This study provides insight into the molecular level changes taking place following exposure to acidified seawater in a non-calcifying, ubiquitous, organism

Persistent organic pollutants in the Atlantic and southern oceans and oceanic atmosphere

Persistent organic pollutants (POPs) continue to cycle through the atmosphere and hydrosphere despite banned or severely restricted usages. Global scale analyses of POPs are challenging, but knowledge of the current distribution of these compounds is needed to understand the movement and long-term consequences of their global use. In the current study, air and seawater samples were collected Oct. 2007–Jan. 2008 aboard the Icebreaker Oden en route from Göteborg, Sweden to McMurdo Station, Antarctica. Both air and surface seawater samples consistently contained α-hexachlorocyclohexane (α-HCH), γ-HCH, hexachlorobenzene (HCB), α-Endosulfan, and polychlorinated biphenyls (PCBs). Sample concentrations for most POPs in air were higher in the northern hemisphere with the exception of HCB, which had high gas phase concentrations in the northern and southern latitudes and low concentrations near the equator. South Atlantic and Southern Ocean seawater had a high ratio of α-HCH to γ-HCH, indicating persisting levels from technical grade sources. The Atlantic and Southern Ocean continue to be net sinks for atmospheric α-, γ-HCH, and Endosulfan despite declining usage

Short-term effects of CO₂-induced low pH exposure on target gene expression in Platynereis dumerilii

Objective: Increasing atmospheric CO₂ concentration are causing changes to the seawater carbonate chemistry, lowering the pH and we study potential impacts of these changes at the molecular level in a non-calcifying, marine polychaete species Platynereis dumerilii. Methods: we investigate the relative expression of carbonic anhydrase (CA), Na+/H+ exchangers (NHE), and calmodulin (CaM) genes from P. dumerilii under acidified seawater conditions (pH 7.8) induced by CO₂ using qPCR. Results: mRNA expression of CA in the CO₂-induced worms was significantly up-regulated at low pH conditions (pH 7.8, 1h), suggesting changes in acid-base balance. In contrast, the expression of NHE and CaM showed no significant change. In addition, we compare these results to a previous study using inorganic acid (HCl)-induced pH changes. Conclusions: results suggest that carbonate chemistry has an impact on gene expression that differs from pH-associated change. To our knowledge, this is the first study that compares low pH exposure experiments using HCl and CO₂ as the inducing agents