Solar Saltworks Research Articles

The Ninth International Symposium on Salt and the Ecological Importance of Solar Saltworks

The Ninth International Symposium on Salt (www.worldsalt2009.com) organized by China National Salt Industry Corporation, China Salt Association and many other salt organizations of the world was held in the Beijing International Convention Center on the 4-7 September 2009. It is the ninth in a series of symposia since 1962 when the first meeting held in Cleveland, USA. The World Symposia on Salt specialize in reporting and discussing progress of the latest development and views of salt industry world wide. They cover the whole spectrum of subjects dealing with the science, engineering, technology, economics and history of all type of salts and other evaporites. One hundred eighty five (185) papers were presented in six parallel sessions grouped into the following topics: 1. Vacuum Salt Production and Reduction of Energy Consumption in Salt Production 2. Rock Salt Production and Utilization 3. Sea/Lake Salt and Biology 4. Salt Chemical Production 5. Salt Culture, History and Education 6. Salt and Health 7. Salt Processing and Quality Assurance 8. Iodized Salt for IDD Elimination 9. Salt Marketing More than twenty presentations were related to biological process of Solar Saltworks and their Ecological Importance, among 75 presentations that were dedicated to Solar Saltworks. The present work focuses on the presentations and also the discussions that took place in Beijing Salt Symposium that are mainly related to the topics of the 1st and 2nd International Conferences on the Ecological Importance of Solar Saltworks (1st and 2nd CEISSA, www.alasecology. org, www.gnest.org) held in Santorini, Greece, 2006 and Merida, Mexico, 2009 respectively.

Behaviour of trace elements during the naturel evaporation of sea water: case of solar salt works of Sfax saline (S.E. of Tunisia)

We have carried out a geochemical study on the behaviour of certain trace elements during the evaporative concentration of free brines (salinity from 41 to 400 ‰) of the solar salt works of Sfax saline (S.E of Tunisia). The elements concerned by this survey are Zinc, Cadmium, Manganese, Molybdenum, Lead, Copper, Aluminium, Iron and Barium. Adequate analytical techniques, adapted to this environment of high salinity, have been used to follow the evolution of the concentration of concerned elements in brines subjected to the evaporation. The results obtained have been presented in function of concentration factor calculated on the basis of the Lithium content in seawater (Coast of Sfax) and those in the brines of salt works. During the evaporation process, the concentration of trace elements in brines was affected by the evaporation phenomenon for the same reason as the major elements. Nevertheless, their concentrations remain very weak and don't reach their saturation doorsteps. The participation of these elements in the mineral phases can take place only by co-precipitation with saline paragenesis. It is the case of Zinc that can precipitate with Sulphates Salts, the Cadmium, Barium and Copper with Carbonate and Gypsum, the Manganese and the Molybdenum with Potassium Salts; others like Iron and Aluminium, are characterized by a very complex behaviour and are subjected, therefore to effects others than those of the evaporation and the co–precipitation. We can mention the activity of the biological system and adsorption phenomena, in particular, on the organic and mineral particles. They are frequent in ponds where brines are not yet very concentrated; allowing an important biological productivity. Contents in these elements are then variable and very dependent on the growth and the physiological state of the organic matter. These micro-organisms use some metals in their metabolic activities, and notably those that act like vitamin factors. The analysis of sediment and algae sampled from the first ponds of the saline, shows that they are capable as well to fix some important quantities of trace elements. The liberation of these elements by deterioration of organic matter, provoke the important fluctuations of their contents in free brines. In basins where the biologic activity is very limited because of the increase of brines salinity, the evolution of the concentration of trace elements translate the only effect of the evaporation, counterbalanced by adsorption phenomenon and the co-precipitation with the salts deposit.

Solar saltworks' wetland function

Salt, the world’s best-known mineral, is the chemical substance most related to human civilization history. Apart from his significance for the creation of life on the planet it has been used as main commodity for centuries. Man produces salt by solar evaporation since the dawn of human civilization. Nevertheless, recognition of the unique coastal ecosystems that developed in parallel with the Solar Saltworks production process evolution is often lacking. The environmental uniqueness of Solar Saltworks, particularly current operations, is based on the fact that they are integrated, constructed coastal ecosystems, where regular and hyper saline environments coexist and establish high significant shelters for wildlife. The basic steps of the Solar Salt Production Process Evolution are identified. The biological process that develops along with the salinity vector in the evaporating ponds and crystallizers produces food for many kinds of birds. Hundreds of bird species depend on Solar Saltworks ecosystem to feed and/or nest. Many of them have been identified as endangered species or protected by European or International conventions. The operation of the Coastal Saline Wetlands is outlined and compared with Solar Saltworks ecosystem. We emphasize on the case of “Aliki” lake, which is a natural saline coastal wetland located in Lemnos, a Northern Aegean Sea Island in Greece.

Environmental balance of salt production speaks in favour of solar saltworks

Solar saltworks are most efficient converters of solar energy into an inorganic commodity. Conversion rate of solar radiation into removal of water vapour from the brine takes place with 45% efficiency. Solar salt requires only a fraction of man made energy compared with salt produced by solution mining and thermal evaporation. Advanced technologies for biological management, crystallisation, harvesting techniques and salt processing, allow production of solar salt 99.94% pure, which is comparable with purity of vacuum salt. Proper biological management of solar saltworks leads to brine containing less organics. Organic compounds in brine adversely influence the crystal growth habit, which results in inclusions of impurities inside the salt crystals. Advanced salt purification technology is able to completely remove impurities from the salt crystals incurring insignificant salt processing losses. About 60% of salt produced worldwide is consumed by the chemical industry. High quality solar salt used as feedstock in membrane cell chloralkali plants causes equally low contaminated effluent discharge from brine treatment as vacuum salt. Trace elements that may cause membrane damage, such as iodine, or those elements that are critical to chlorine purity, such as bromine, are present in smaller quantities in solar salt than in many salts originating from rock salt deposits. Bird watchers driving in jeeps through solar saltworks may not realise that the vast water fields hosting flamingos are not only beautiful but that they contribute towards the shift in the environmental balance in the direction of higher overall ecological benefit as well.

Temporal and salinity impacts on the microbial diversity at the Eilat, Israel Solar Salt Plant

A major solar salt works in Israel is located just north of the town of Eilat and close to the airport. This solar salt works has been in operation since 1977 and produces about 170,000 tons a year. A three-year study was initiated to examine the temporal and salinity impacts on the microbial community throughout this saltern. At the time this study was begun in the late 1990's, there were several paradigms about the microbial community: 1. there is greatly reduced diversity as the water reaches saturation; 2. because of the relative stability of the salt concentrations in the various pans, there is little change in the microbial community; and, 3. halophilic Archaea are not found in ponds with less than 15% salt and halophilic Bacteria would not be found in pans at saturation. The first paradigm was developed based on a few studies using one medium and single observations of various salterns. The second paradigm was an assumption that had not been systematically tested, and the third paradigm, at least for the Bacteria, was shown in 1980 not to be true with the discovery of the genus Halomonas. We examined these paradigms by systematically studying on a seasonal basis the saltern at Eilat, Israel, as well as the Cargill Solar Salt Plant in Newark, California. Both traditional and molecular techniques have been used throughout these studies. Several different approaches were taken: plate counts were made on several different media, whole community carbon requirements were determined, molecular fingerprinting of the whole microbial community using the amplicon length heterogeneity approach was performed to determine the changes in the community composition over time, and partial characterization of the isolated pure cultures were all performed. Samples were taken at least twice a year corresponding to the cooler and hotter times of the year. Based on this extensive study there were significant differences in the plate counts and in the ratios of the various peaks found during the fingerprinting. It is safe to say now that the microbial community in the waters of a solar saltern is variable and both domains can be found throughout the saltworks.

Schinias wetland: A National Park or a solar saltwork?

Schinias is a small coastal biotope under environmental pressure. Partial drainage of the wetland and different disturbing activities have degraded ecological habitats and decreased biodiversity for many decades. Recently, the construction of a rowing centre has restored hydrological regime and the area has been designated as a National Park; however, application of conservation measures meets difficulties of social and financial nature. In this paper, bird diversity is used as an indicator to examine Schinias’ ecosystem state, according to three different scenarios: the first one refers to the diversity that had been recorded before restoration of the hydrological regime; the second one refers to the diversity that has been recently recorded and corresponds to the actual condition of the National Park with the rowing center; the third one corresponds to a potential diversity that would be observed in case Schinias became a solar saltwork.

Management of biological systems for continuously-operated solar saltworks

The goal of every solar saltworks with seawater intake--continuous and economic production of high quality salt (sodium chloride) at design capacity—requires ability to simultaneously manage and coordinate physical systems with biological systems in the concentrating and crystallizing ponds. This effort requires close control of specified salinities, depths, and brine transfers, frequent surveillance and adjustments of planktonic and benthic communities and their key microorganisms, and timely recognition and correction of developing problems. This report reviews features and concepts that facilitate biological and physical management, considers causes and effects of common and severe disturbances and their solutions, and provides information that enable biological systems in the ponds of a solar saltworks aid rather than harm salt production.

Phytoplankton and macrofauna in the low salinity ponds of a productive solar saltworks: Spatial variability of community structure and its major abiotic determinants

This paper focuses on the structure of the phytoplankton and macrobenthic invertebrates communities in a productive solar saltworks, as well as the major abiotic determinants of the observed biotic patterns. The observed patterns in the structure of the biotic communities attest that the ecosystem of the low salinity ponds of Kalloni Saltworks is similar to a productive coastal lagoon. Major abiotic determinants include the salinity and confinement gradients, as well as inorganic nutrients loads. The episodic enrichment of the water column in the ponds with either new nutrients from the incoming seawater, or regenerated nutrients released from the sediment, was shown to stimulate the growth to bloom levels of phytoplankton species indicative of organic enrichment and coastal eutrophication. Algal biomass and the accumulated detritus and organic matter on and within the sediment are exploited by opportunistic herbivores and deposit feeders tolerant to organic enrichment. Management measures are needed for the mitigation of the productiveness of the low salinity ponds, e.g. lower water residence times, a shallower water column, facilitation of the oxygenation of the sediment, sediment removal in winter and culture and harvesting of the naturally occuring, edible Cerastoderma glaucum bivalves.

Structure, function and management of the biological system for seasonal solar saltworks

The structure and function of communities and biological systems favorable and unfavorable to salt production in the ponds of solar saltworks are described. Favorable systems maintain a diverse biota and power the organisms at levels that enable a saltworks to economically and continuously produce high quality salt at design capacity. Unfavorable systems-the result of disturbances and high concentrations of nutrients in the water-are dominated by a few species that release massive quantities of organic substances, decrease pond surface areas and volumes, and decrease salt quality and quantity. Management practices to obtain and maintain favorable systems under a variety of conditions are reviewed.

Phytoplankton assemblage of a solar saltern in Port Fouad, Egypt

The present study is the first investigation of the phytoplankton community in one of Egypt’s saltworks. The phytoplankton composition and distribution in five ponds of increasing salinity were investigated in the solar saltern of Port Fouad. The phytoplankton community consisted of 42 species belonging to cyanobacteria (16), diatoms (12), dinoflagellates (11), Euglenophyceae (2) and Chlorophyceae (1). The number of species decreased significantly and rapidly with increasing salinity, varying between 33 species in the first pond (P1) and one species in the crystallizer pond (P5). Conversely, the total phytoplankton density, except that recorded in P1, increased significantly with rising salinity, fluctuating between 8.7 and 56×105 individuals l−1 in P2 and P5 respectively. In spite of the local variations in climate and nutrient availability, the phytoplankton composition, density and spatial variations along the salinity gradient were, in many respects, very similar to what has been observed in other solar saltworks. The pond with the lowest salinity (P1−< 52gl−1) was characterized by a significant diversity and blooming of diatoms and dinoflagellates. Intermediate salinity ponds (P2 and P3) with salinity∼112–180gl−1 exhibited a decline in both species richness and density, but the stenohaline blue green algae (Synechocystis salina) did flourish. The highly saline concentrating ponds and crystallizers (P4 and P5) with salinity∼223–340gl−1 were characterized by few species, the disappearance of blue green algae and the thriving of the halotolerant green alga Dunaliella salina.

A revision of Artemia biodiversity in Macaronesia

In a biogeographical context, the term Macaronesia broadly embraces the North Atlantic archipelagos of the Azores, Madeira, Selvagens, the Canary Islands, and Cape Verde. The peculiar arid climatic conditions in some of these places have led to the development of marine salt exploitations, which can be counted among the hypersaline habitats of the brine shrimp Artemia (Branchiopoda, Anostraca). Parthenogenetic populations of this anostracan were described in the Canary Islands during the last decades of the 20th century, while the American Artemia franciscana species was recently found in the Cape Verde archipelago. Following an invasive pattern, this exotic species has recently reached the Canary Islands, too. This paper reports information dealing with biotope loss (solar saltworks) in this biogeographical region, together with possible consequences concerning the arrival of invasive species, two factors that frequently promote dramatic biodiversity losses. The discussion of this threat focuses mainly on the Canary Islands archipelago where native species of Artemia still exist.

Recent analog of gypsified microbial laminites and stromatolites in solar salt works and the Miocene gypsum deposits of Saudi Arabia and Egypt

Accumulation of microbial mats and stromatolites dominate in the crystallization ponds of solar salt works west of Alexandria, Egypt. These microbial mats are laminar in the permanent submerged part of the ponds. The microbial mats commonly form sites for growth of gypsum crystals during periods having higher salinity. In the dominant submerged part of the pond, domal stromatolites are common around groundwater seepage holes. In the shallow, intermittent margin of the ponds, the laminated microbial structure forms laterally close-linked hemispheroidal stromatolite type, with unidirectional and multidirectional ripple mark-like morphology on their surface. The microbial laminite and stromatolite types in the modern solar salt works are similar to the organic-rich Miocene gypsum beds of El-Barqan (west Alexandria, Egypt) and Rabigh (north Jeddah, Saudi Arabia). The Miocene organic-rich beds consist of interlayered dark-colored microbial laminae and light-colored gypsum laminae. These beds may have three different variations: regular even lamination, laterally closed-linked hemispheroidal stromatolites, and/or discrete hemispheroidal stromatolites. Petrographic examination of the microbial laminites and stromatolites in the solar salt works and the Miocene gypsum beds indicate that the dark-colored, organic-rich laminae are composed of micritized microbial laminae and/or brown organic filaments. In El-Barqan area, the light-colored gypsum-rich laminae are composed of either gypsum crystal fragments, or lenticular and prismatic gypsum. These gypsum crystals are either entrapped within the microbial filaments or are nucleated at the surface of the microbial laminae to form a radial pattern, whereas in Rabigh area, the light-colored gypsum-rich laminae are composed of secondary porphyrotopic, poikilotopic, or granular gypsum crystals. By comparison of the microbial structure in the Miocene gypsum beds with the recent occurrence of the microbial laminites and stromatolites in the solar salt works, it is demonstrated that the organic-rich Miocene gypsum beds were formed in a very shallow salina with slightly fluctuating brine levels.

Brazilian solar saltworks - ancient uses and future possibilities

Coastal solar saltworks of Brazil are exploited for sea salt, which becomes progressively concentrated by evaporation. This study aimed to review the current and new potential uses of these systems, in order to provide more dynamic for this activity. The first evaporation ponds are also used for artisanal fisheries, ensuring the livelihood of many families. All the brine rich in secondary salts (bittern) can be widely used by the chemical industry, while the Brazil shows an incipient production of "flower of salt", a salt with distinct characteristics with higher market value than sodium chloride. On the other hand, the saltponds have a high potential for management and obtaining of large populations of Artemia spp., purifying the brine through the action as biological filter. This microcrustacean occurs naturally in intermediate salinity ponds, being commonly used in aquaculture. Species of microalgae and halobacteria found in the saltworks are employed for extraction of beta-carotene and glycerol, used in an extensive list of products with high commercial value. These ecosystems represent refuge zones for many species of migratory birds, becoming imperative to promote the conservation of these hypersaline wetlands.

Morphometric, Hydrogeologic and Hydrochemical Analyses of Solar Saltwork Pond Region, in Meha Area, Northwest Sharqat City, Iraq

The study determines the shape, area, and discharge properties and other factors of morphometric analysis and drainage pattern to characterize the optimum location for salt harvesting in the salt ponds in Meha area, northwest Sharqat city, Iraq. The morphometric analysis confirms the idea of the upward leakage of salt rich water from the deep ground water along the surface of deep fault. The hydrogeological data of groundwater leakage encourage the method of harvesting salt by evaporation ponds. Also, the relationship between hydrochemical parameters, their variation with the period of evaporation, increasing of Na+ and Cl– percentages, and decreasing of other component support the salt production in the area.

Tracing Waterbird Exposure to Total Mercury and Selenium: A Case Study at the Solar Saltworks of Thyna (Sfax, Tunisia)

Saltworks have emerged as important alternative/complementary feeding habitats for avifauna. However, the consequences of such habitat shifts in terms of changes in exposure to contaminants are poorly understood. We evaluated the exposure of the waterbird community breeding at the saltworks of Thyna (Tunisia) to total Hg (THg) and Se according to their differential use of saltworks dietary resources, as revealed by δ¹³C and δ¹⁵N values in their eggs (included species [n] -sorted according to increasing reliance on saltworks resources: Yellow-legged Gull Larus michahellis [12], Common Tern Sterna hirundo [12], Slender-billed Gull Larus genei [15], Little Egret Egretta garzetta [20], and Pied Avocet Recurvirostra avosetta [22]). Concentrations of THg and Se were under the threshold points for deleterious effects. Egg THg concentrations significantly decreased as the dietary contribution of saltworks resources increased (mean: 3.23, 1.66, 0.76, 0.4, and 0.27 μg/g dw, respectively). Conversely, egg Se concentrations did not vary according to foraging habitats (2.49, 2.96, 2.61, 3.27, and 1.5 μg/g dw, respectively). Tracing waterbird exposure to THg and Se at saltworks was feasible through the use stable isotopic assays of eggs. Birds using saltworks are not exposed to higher concentrations of THg and Se than in adjacent marine habitats.

Evolutionary origin and phylogeography of the diploid obligate parthenogen Artemia parthenogenetica (Branchiopoda: Anostraca).

BackgroundUnderstanding the evolutionary origin and the phylogeographic patterns of asexual taxa can shed light on the origin and maintenance of sexual reproduction. We assessed the geographic origin, genetic diversity, and phylogeographic history of obligate parthenogen diploid Artemia parthenogenetica populations, a widespread halophilic crustacean.Methodology/Principal FindingsWe analysed a partial sequence of the Cytochrome c Oxidase Subunit I mitochondrial gene from an extensive set of localities (including Eurasia, Africa, and Australia), and examined their phylogeographic patterns and the phylogenetic relationships of diploid A. parthenogenetica and its closest sexual relatives. Populations displayed an extremely low level of mitochondrial genetic diversity, with one widespread haplotype shared by over 79% of individuals analysed. Phylogenetic and phylogeographic analyses indicated a multiple and recent evolutionary origin of diploid A. parthenogenetica, and strongly suggested that the geographic origin of parthenogenesis in Artemia was in Central Asia. Our results indicate that the maternal sexual ancestors of diploid A. parthenogenetica were an undescribed species from Kazakhstan and A. urmiana.Conclusions/SignificanceWe found evidence for multiple origin of parthenogenesis in Central Asia. Our results indicated that, shortly after its origin, diploid A. parthenogenetica populations underwent a rapid range expansion from Central Asia towards the Mediterranean region, and probably to the rest of its current geographic distribution. This contrasts with the restricted geographic distribution, strong genetic structure, and regional endemism of sexual Artemia lineages and other passively dispersed sexual continental aquatic invertebrates. We hypothesize that diploid parthenogens might have reached their current distribution in historical times, with a range expansion possibly facilitated by an increased availability of suitable habitat provided by anthropogenic activities, such as the spread of solar saltworks, aided by their natural dispersal vectors (i.e., waterbirds).

Minimizing the Environmental Impact of Sea Brine Disposal by Coupling Desalination Plants with Solar Saltworks: A Case Study for Greece

The explosive increase in world population, along with the fast socio-economic development, have led to an increased water demand, making water shortage one of the greatest problems of modern society. Countries such as Greece, Saudi Arabia and Tunisia face serious water shortage issues and have resorted to solutions such as transporting water by ships from the mainland to islands, a practice that is expensive, energy-intensive and unsustainable. Desalination of sea-water is suitable for supplying arid regions with potable water, but extensive brine discharge may affect marine biota. To avoid this impact, we explore the option of directing the desalination effluent to a solar saltworks for brine concentration and salt production, in order to achieve a zero discharge desalination plant. In this context, we conducted a survey in order to evaluate the potential of transferring desalination brine to solar saltworks, so that its disposal to the sea is avoided. Our analysis showed that brine transfer by trucks is prohibitively expensive. In order to make the zero discharge desalination plant economically feasible, efforts should be directed into developing a more efficient technology that will result in the production of only a fraction of the brine that is produced from our systems today.

Properties of seawater bitterns with regard to liquid-desiccant cooling

This study concerns the properties of the concentrated bittern solutions occurring as by-product from solar salt works, in relation to their potential use as liquid desiccants in cooling systems. Solutions of compositions similar to those of bitterns have been made up in the laboratory, as have concentrated mixtures of MgCl2–MgSO4–H2O. Measurements of vapour pressure have been carried out using an isoteniscope and are reported together with measurements of density and viscosity. Several theoretical models representing these properties are reviewed and compared against the experimental results; the average agreement between theory and experiment is within 5% for vapour pressure and better for the preferred models of the other two properties. Based on these findings, an expression is provided for the equilibrium relative humidity of bitterns as a function of concentration relative to raw seawater. The vapour pressures of bittern solutions are found to be similar to those of solutions containing only magnesium chloride but having the same mass fraction of total salts. Therefore magnesium chloride solution is a reasonable model for bitterns for the purpose of developing the proposed cooling system.

Characterization of Dunaliella salina strains by flow cytometry: a new approach to select carotenoid hyperproducing strains

In the present work the characterization of different strains of Dunaliella salina from established cell culture collections and various isolates from solar saltworks located in the Canary Island, as well as one mutant, was carried out in order to assess the existence of intraspecific differences and to determine the potential productivity of each one. Morphological characteristics such as cellular size and cellular complexity and parameters linked to cellular physiology, such as pigment content or cellular growth rate, were determined by means of traditional techniques as well as flow cytometry. Results showed a high morphological and physiological intraspecific variability among the studied strains. Results suggest that the application of the lipidic dye Nile red allowed the development of a cytometric method faster than the traditional techniques to select carotenoid hyperproducing strains of microalgae.

Communities structure of the planktonic halophiles in the solar saltern of Sfax, Tunisia

The composition and distribution of the main planktonic halophilic micro-organisms (heterotrophic and autotrophic picoplankton, nanoplankton, phytoplankton, ciliates) and metazooplankton were investigated in six ponds of increasing salinity in the solar salt works of Sfax, Tunisia, from January to December 2003. Marked changes in the composition and biomass of the communities were found along the salinity gradient, especially at salinities of 150 and 350. Autotrophic picoplankton, nanoplankton, diatoms, dinoflagellates and ciliates characterized the less salted ponds. Planktonic biomass was the highest at intermediate salinity as a consequence of a bloom of Ochromonas. Species richness of phytoplankton, ciliates and zooplankton greatly decrease above a salinity of 150 and typical halophiles ( Dunaliella salina, cyanobacteria, Fabrea salina and Artemia salina) were found between 150 and 350 salinity. In this environment, F. salina appeared more adapted than the brine shrimp to survive during phytoplankton blooms. The halophilic plankton was however almost entirely composed of heterotrophic prokaryotes in the crystallizers. We thus observed a progressive disappearance of the autotrophic planktonic communities along the salinity gradient. Multivariate analysis of the communities provides evidence that ponds represent discrete aquatic ecosystems within this salt works.