Salt Pans Research Articles

Halophilic microbiome: Distribution, diversity and applications

Microorganisms that love salt are known as halophiles, and they are found in both the archaeal and eubacterial domains of life. Halophiles do naturally occur in mesmeric saline habitats such as hypersaline lakes, salt pans, salt marshes, saline soils, and solar salterns. The group of microorganisms that live in a salty environment is known as the halophilic microbiome. This group includes bacteria, algae, fungi, viruses, and more. According to how much salt they can tolerate, halophiles are divided into three categories: mild (0.3-0.8 M), moderate (0.8-3.4 M), and extreme (3.4-5.1 M). Seawater already covers the majority of the surface of the Earth and has a salinity of roughly 0.6 M. The most numerous and adaptable microorganisms are therefore those that thrive in such environments. Due to the presence of carotenoids, many halophiles exhibit red-pigmented colonies. This pigment resembles that of tomatoes, red peppers, pink flamingos, and other similar foods. In the production of traditional fermented foods like sauces and pickles, some halophiles play a specific role. Since the majority of their potential is still unknown, halophilic microbes have fewer but more significant biotechnological applications than thermophiles and alkaliphiles. Nevertheless, they could be an important source of many particular biomolecules, including salt-stable enzymes, biopolymers, and pigments. Halophiles may also be crucial for bioprocesses like bioleaching, bioremediation, biotransformation, and biofermentation. Halophiles might have some interesting uses in both medicine and agriculture. This review essay examined the diversity, distribution, and uses of halophiles.

Impact of Dead Sea Halo-Karst Development on an Earthen Dike Rehabilitation Project

From the 1970s, the Dead Sea experienced severe halo-karstification and anthropogenic modifications. Progressively, but at an accelerating rate, subsidence, landslides, and sinkholes have increased in number and magnitude. The hazards’ triggering factors are the terminal lake level lowering at more than one meter per year and the dynamic equilibrium of the hydrogeological system. Over the Lisan peninsula, archived satellite images revealed the extent of the damaged areas. On 22 March 2000, the destruction of dike 19 represented a loss of 38 M USD. This is the most important event recorded since the beginning of the Dead Sea recession some 50 years ago. In 2018, a rehabilitation project of that dike started. This research analyses the viability of the reinstatement works. The advanced space borne radar interferometry technique is applied to map ground deformations before and during the project. This article reveals that the ongoing rehabilitation and reinstatement works of dike 19 are threatened by ongoing halo-karstification processes. Field observations and subsidence/uplift dynamics support this statement. The past experiences are taken into consideration to adapt industrial expansion strategies. However, the permeability of the salt pan floor could trigger a fast development of a karst system able to destroy the rehabilitated dike 19.

Groundwater conceptual pollution model and related human health hazards, the main dilemma of a desert aquifer near ophiolite complex.

Groundwater is a finite resource in Davarzan region which is located between the ophiolite complex mountain in the north and salty playa at the south. The water samples were analyzed to assess the origin of groundwater pollution and explain links between the disturbed heavy metals composition of the earth's surface and the human health risks. The main heavy metal pollutants in the groundwater are Cr, Fe, As and Pb ions. In general, the groundwater salinity and some elements such as Cr and As are increased along with surface topography and groundwater flow directions from the northern ophiolite highlands recharge area to the adjacent desert discharging zone in the south. Despite the ophiolite complexes being the most enriched in Cr element, the lowest Cr concentration in the groundwater was measured near the ophiolite area, which is in the range of its discharged springs. Based on the groundwater conceptual pollution model, bedrock geochemistry controls the composition of soil and hence that of groundwater. The Cr samples show a direct relation with the EC value indicating that intrusion of salinity from the salt pan is probably another reason for the increased Cr concentration. The results of health risk assessment indicated that the groundwater suffered from significant contamination and if used for long-term without pre-treatment may pose serious health risks to human population via drinking water and irrigation of agricultural fields. This is the first attempt to apply hydrogeological setting along with the source of pollution and its health risk in a desert-ophiolitic area.

Морфолого-генетична та агрономічна характеристики контрастних за засоленням ґрунтів солонцевого комплексу Приорілля

The article presents the results of field and laboratory studies on the determination of the morphological, genetic and agronomic characteristics of the soils of the Solon complex of Prioril, contrasting in terms of salinity - the establishment of the peculiarities of the morphological structure of the profiles, the granulometric composition, and the parameters of the main agrochemical, salt and physicochemical parameters of the salt marsh of the meadow-black earth shallow salt marsh and black earth-meadow soil - as typical components of the salt complex of the Oril river valley. Standardized field survey and laboratory-analytical methods were used. It has been established that manifestations of halogenation increase with depth in the Luchno-chernozem salt marsh. Alkalinity in the humus-iluvial horizon increases to a strong degree, in deeper horizons - to a very strong one; the degree of salinity increases to medium, strong, and finally to very strong in the bedrock. According to the depth of the upper horizon of salt accumulation, this soil is classified as saline. The content of absorbed sodium in the humus-iluvial and illuvial horizons corresponds to the "saline" gradation. The chernozem-meadow soil is non-saline according to the content of toxic salts in the entire profile, there are no signs of physical and physico-chemical salinity. The content of the silt fraction in the salt marsh profile increases with depth and reaches its maximum value in the illuvial horizon, which is typical for salt marshes and is explained by the redistribution of soil colloids in the profile, the granulometric composition of the salt marsh in the humus-eluvial and illuvial horizons is light clay, in the humus-illuvial - medium clay. The profile of the chernozem-meadow soil is also heterogeneous in granulometric composition, which is heavier from medium loam in the humus horizon to heavy loam in the transitional horizons. The reason for this may be ancient alluvial processes that formed the soil-forming rock of the single-forest terrace. The content of humus in the salt pan in humus-eluvial and humus-iluvial horizons is average, the content of mineral (nitrate and ammonia) nitrogen is very low. The content of mobile potassium turned out to be elevated, and the content of mobile phosphorus was very high. In the chernozem-meadow soil, the content of humus in the humus arable horizon is high, in the first transitional one, it is average. The content of mineral nitrogen is low. The content of mobile phosphorus exceeds the upper limit of the high level by 3.5 times, and mobile potassium by 3.1 times, which is typical for the soils of closed depressions and is a consequence of long-term accumulation of surface runoff waters. Conclusions. The salt marsh complex of Priorillya with the number of salt marshes in the soil cover of about 50% is typical for the southern part of the Middle Forest Steppe in terms of the structure of soil profiles and soil halogenation. A characteristic feature of the studied salt marsh complex is the significant contrast of its components in terms of halogenation manifestations: at a short distance there are salt marsh highly saline salt marsh and leached chernozem-meadow soil without physical and physico-chemical signs of salinity.

The origin of the depressions interrupting the eastern Sierra Pampeanas broken foreland, explained by localized crustal extension through the juan Fernández ridge path, using gravimetric data

The Salinas Grandes and Salina de Ambargasta salt pans are located in the Eastern Sierras Pampeanas in the Pampean broken foreland zone, a product of the Chilean-Pampean flat subduction zone. This region constitutes an anomalously flat morphology of 350 × 150 km and occupies an extensive area in a northeast-southwest direction.These flat depressions abruptly interrupt the eastern Sierras Pampeanas morphology, burying the structure beneath Late Cenozoic-Quaternary deposits of the Andean orogenic front. We obtained from a previous model in spherical harmonics, the geometry of the Moho observing a lower crustal attenuation below the salt pan areas, which is maximum towards the north of the Salina de Ambargasta. From the Bouguer anomaly, calculated by unifying data from different sources, and its residual anomaly, we calculated the analytical signal to adjust the gravimetric anomaly's wavelength, which shows that this flat morphology follows NE to NNE gravity minima. Werner deconvolution and localized Euler deconvolution calculated from the residual Bouguer anomaly indicate that the anomalous masses are located above 15 km depth, by the wavelengths of the anomalies, presumably indicating the differential uplift of high-density rocks placed in the lower and mid-crust, following the measured crustal attenuations. Additionally, these solutions show that this NE depression is segmented by NNW structures perpendicular to the main trough. Crustal thickness attenuation is interpreted as related to the track of the Juan Fernandez Ridge beneath the eastern Pampean broken foreland sector, based on plate kinematic reconstructions. As depicted in recently released tomographic data, its tearing and related asthenospheric upwelling could have promoted lithospheric localized extension, explaining the Salinas Grandes-Ambargasta depressions that are segmenting the eastern Sierras Pampeanas at the Andean orogenic front.

Image Texture as Quality Indicator for Optical DEM Generation: Geomorphic Applications in the Arid Central Andes

The generation of Digital Elevation Models (DEMs) through stereogrammetry of optical satellite images has gained great popularity across various disciplines. For the analysis of these DEMs, it is important to understand the influence of the input data and different processing steps and parameters employed during stereo correlation. Here, we explore the effects that image texture, as well as the use of different matching algorithms (Block Matching (BM) and More Global Matching (MGM)), can have on optical DEMs derived from the flexible, open-source Ames Stereo Pipeline. Our analysis relies on a ∼2700 km2 clip of a SPOT6 tristereo scene covering the hyperarid, vegetation-free Pocitos Basin and adjacent mountain ranges in the northwestern Argentine Andes. A large, perfectly flat salt pan (paleolake bed) that covers the center of this basin is characterized by strong contrasts in image texture, providing a unique opportunity to quantitatively study the relationship between image texture and DEM quality unaffected by topography. Our findings suggest that higher image texture, measured by panchromatic variance, leads to lower DEM uncertainty. This improvement continues up to ∼103 panchromatic variance, above which further improvements in DEM quality are independent of local image texture but instead may have sensor or geometric origins. Based on this behavior, we propose that image texture may serve as an important proxy of DEM quality prior to stereo correlation and can help to set adequate processing parameters. With respect to matching algorithms, we observe that MGM improves matching in low-texture areas and overall generates a smoother surface that still preserves complex, narrow (i.e., ridge and valley) features. Based on this sharper representation of the landscape, we conclude that MGM should be preferred for geomorphic applications relying on stereo-derived DEMs. However, we note that the correlation kernel selected for stereo-matching must be carefully chosen depending on local image texture, whereby larger kernels generate more accurate matches (less artifacts) at the cost of smoothing results. Overall, our analysis suggests a path forward for the processing and fusion of overlapping satellite images with suitable view-angle differences to improve final DEMs.

Numerical modelling of a solar salt pan for improved salt production at Lake Katwe, Uganda

The solar salt pans at Lake Katwe are set up haphazardly without any scientific guidelines which compromises the annual throughput from the solar salt works. To improve on the design of the salt pans, the heat transfer dynamics of the salt pan have been numerically and experimentally studied in this study. A representative salt pan located at the shores of the lake Katwe with a surface area of 62 m2 and a depth of 0.2 m was used in this study. The numerical model was implemented in the OpenFOAM software where a 3D heat transfer salt pan model was studied using the Finite Volume Method under Lake Katwe climatic conditions. The model was governed by continuity, salt concentration, momentum, energy equations and the Boussinesq approximation. A field experiment that determined the temperature variation with depth was carried out. The correctness of the model results was verified against experimental data. The numerical simulation model revealed a salt pan brine temperature increase with time and the salt concentration significantly remained constant with time. The salt pan brine temperature increased from 303 K to 319.5 K after 5 h of the simulation time. The model and the experimental salt concentration and temperature profiles were found to be in a good agreement. The sensitivity analysis on the effect of the salt pan depth on brine temperature was studied. It was revealed that the shallower the salt pan, the higher the rate of heat gain. This study revealed that an optimum salt pan depth to yield a higher salt quantity under Lake Katwe climatic conditions was at 0.1 m.

Evolution of habitat quality and analysis of influencing factors in the Yellow River Delta Wetland from 1986 to 2020

The assessment of habitat quality plays an important role in the effective conservation of wetland biodiversity. The Yellow River Delta Wetland is located in the intertwining zone of sea, terrestrial, and river ecosystems, increasing human activities and climate change posed a great threat to wetland biodiversity. This study first analyzed the spatial and temporal evolution characteristics of habitat quality in the Yellow River Delta Wetland under the evolution of the shoreline after runoff-sediment variability (1986–2020) using the InVEST-habitat quality model and then identified the dominant influence factors on habitat quality based on Geographical Detector. Finally, elasticity index was introduced to analyze the impacts of different reclamation activities on habitat quality. Results showed that the habitat quality decreased from 0.4798 in 1986 to 0.4078 in 2020, with high values of habitat quality concentrated in mudflat wetlands and low values of habitat quality concentrated in construction land and salt pans. The results of the Geographical Detector analysis showed that the influence of human activities, especially reclamation activities, had stronger effects on habitat quality than climatic factors. The elasticity index analysis showed that the elasticity of all three types of reclamation activities, namely, culture ponds, construction land, and salt pans, were negative from 1986 to 2005, 2005 to 2020, and 1986 to 2020. The reclamation activities had a negative impact on habitat quality. The habitat quality of the Yellow River Delta Wetland was most sensitive to the change in reclamation intensity of construction land from 1986 to 2020, and the sensitivity of the change of habitat quality to the change of reclamation intensity of culture ponds and salt pans was strengthening. This study explicitly revealed the effect of climate change and human activities on the habitat quality of the Yellow River Delta Wetland and proposed to analyze the response intensity of habitat quality to different reclamation activities by using the elasticity index, thus providing a scientific basis for mitigating the tradeoff between biodiversity conservation and rapid social development in the Yellow River Delta Wetland in the future.

Habitat Quality Assessment in the Yellow River Delta Based on Remote Sensing and Scenario Analysis for Land Use/Land Cover

Land Use/Land Cover (LULC) change is one of the core features of global change. Habitat quality is an essential representation of ecosystem service functioning and ecosystem health. It is of great significance to assess the habitat quality spatiotemporal heterogeneity caused by land-use change in the regional ecological environment for security and sustainable regional management. Based on the interpreted LULC data of the Yellow River Delta (YRD) in 2000, 2010, and 2020, the PLUS model was used to forecast different LULC 2030 scenarios. Specifically, this study aimed to analyze the LULC change in the YRD and use the InVEST model to evaluate the overall habitat quality in the historical period of the region and future scenarios. From 2000 to 2020, the most critical land-use changes within a 20 km radius from the coastline in the study area are mainly the sharp increase in construction land, mariculture and salt pan, and the sharp decline of coastal wetlands, which is mainly due to the high intensity of human development activities and the process of erosion and deposition in coastal zones and estuarine deltas. During the period, the average habitat quality in the YRD decreased yearly, with the overall regional habitat quality classified as intermediate. The habitat quality was the most significant in the 0–20 km range from the coastline because of the high intensity of human development activities in this area. The habitat quality in the YRD varied under different scenarios in 2030. In the baseline scenario (BS) and socio-economic development (SD) scenario, the habitat quality decreased continuously, but the habitat quality increased under the ecological protection (EP) scenario. This research can provide relevant scientific references for optimizing landscape patterns and improving habitat quality in the YRD region.

:Phoenicians and the Making of the Mediterranean

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Photoinhibition and β-carotene production from Dunaliella sp. isolated from salt pans of Goa

The microalgae Dunaliella is a commercially viable species and is well known for its extreme environmental tolerance and β-carotene production under stressful conditions. We examined the effect of salinity and light intensity on the growth and β-carotene production, respectively, in two different species of Dunaliella: Dunaliella sp. and D. salina, isolated from the salt pans of Goa. Both the species were cultured in growth media with different salinity levels to establish the optimum salinity favouring maximum cell growth. Thereafter, the cells were cultured under optimum NaCl concentration, exposed to a range of light intensity and monitored for β-carotene production. The two species, identified based on their molecular characteristics, displayed a significant difference in growth and β-carotene production. Both D. salina and Dunaliella sp. achieved a maximum of 11.82 × 106 cells mL−1 (0.613 µd−1) and 18.76 × 106 cells mL−1 (0.731 µd−1) at 0.75 M and 0.5 M salinity, respectively. D. salina accumulated a large amount of total carotenoid (36.95 pg. cell−1) when cultured at 0.75 M salinity and exposed to high light intensity (1000 µmol m−2 S−1). In contrast, the carotenoid content per cell was low in Dunaliella sp. (3.07 pg. cell−1) when cultured under optimal salinity (0.5 M) and high light intensity, indicating photoinhibition. We found that different Dunaliella species exhibit different photo-physiological properties that need further evaluation to identify the right candidate for industrial applications.

Protected species in grassland habitats of Ukraine

Based on the analysis of more than 17,000 vegetation plots (relevés), the participation of 261 protected species (254 vascular plants, six lichens, and one bryophyte) in 30 EUNIS grassland habitat types was revealed. Vegetation plots were assigned to the habitat types using the EUNIS-ESy expert system with further verification. We consider as protected species those listed in the current edition of the Red Data Book of Ukraine, Resolution 6 of the Bern Convention, Annexes II and IV of the Habitat Directive, and the IUCN Red List (only categories VU, EN, CR). The participation of protected species was studied according to the following three criteria: (1) the total number of protected species in the plots assigned to a certain habitat type, (2) the number of plots in which at least one protected species is present, and (3) the mean number of protected species per plots within each habitat type. True steppes (R1B) and meadow steppes (R1A) differed with a significant predominance of the total number of protected species. Arctic alpine calcareous grassland (R44) and Continental dry rocky steppic grassland and dwarf scrub on chalk outcrops (R15) had the largest proportion of plots with protected species and the highest mean numbers of protected species per relevé. Saline habitats, in particular Temperate inland salt marsh (R63) and Semi desert salt pan (R64), were characterized by the smallest number of plots with protected species. Among all species, Gymnadenia conopsea, Stipa capillata, Colchicum autumnale and Gladiolus imbricatus occurred in the largest number of studied habitat types. Based on the results of the analysis, appropriate ways of optimizing the protection of grassland habitats and protected species are proposed.

Partial Purification of Extracellular Amylase From Halotolerant Actinomycetes Streptomyces brasiliensis MML2028

Amylase is considered as an industrially important enzyme as it occupies the most important function in the food, paper, and pharmaceutical industries. The present study is concerned with the optimization, production and partial purification of halotolerant amylase from newly isolated Streptomyces brasiliensis MML2028, from Kelambakkam salt pan, Tamil Nadu, India. The primary screening was carried out by well diffusion assay to find the zone of lysis. The assay was observed for each media optimization by measuring the release of reducing sugar (RS) by the 3,5 dinitro salicylic acid (DNS) method and expressed in the international unit (UI). Ammonium sulphate precipitation was used to partially purify the enzyme and then lyophilized. SDS-PAGE was performed to identify the molecular weight. The production medium was optimized with 1% of the starch substrate, 3% of NaCl at 24˚C and pH 9, and incubation of 9 days. The total activity of the partially purified α-amylase was observed to be 1806.9U/mL. The partially purified enzyme was more active with 3% NaCl, pH 8, and 24˚C which is known to be a halotolerant alkaline α-amylase. The enzyme showed tolerance towards magnesium, manganese ions, Triton x-100, and urea. De-inking of α-amylase showed good results proving that the enzyme activity is more efficient. Hence, the alkaliphilic amylase from Halotolerant actinomycetes S. Brasiliensis MML2028 could be a better microbial source that can be used in many industries, especially in paper and textiles.

Spatiotemporal detection of land use/land cover changes and land surface temperature using Landsat and MODIS data across the coastal Kanyakumari district, India

This study assesses the changes in land use/land cover (LULC) and land surface temperature (LST) to identify their impacts from 2000 to 2020 along the coast of Kanyakumari district, India using remote sensing techniques. Landsat images are used to estimate the LULC changes and the MODIS data for LST. The Maximum Likelihood Classification (MLC) method is used, and the LULC is classified into six categories: Agriculture Land, Barren Land, Salt Pan, Sandy Beach, Settlement, and Waterbody. Within the two decades of the present change detection study, upheave in the Settlement area of 49.89% is noticed, and the Agriculture Land is exploited by 20.09%. Salt Pan emits a high LST of 31.57 °C, and the Waterbodies are noticed with a low LST of 28.9 °C. However, the overall rate of LST decreased by 0.56 °C during this period. This study will help policymakers make appropriate planning and management to overcome the impact of LULC and LST in the forthcoming years.

Surface water groundwater interaction in water-stressed semi-arid western India: Insights from environmental isotopes

Understanding the groundwater-surface water interactions and groundwater recharge mechanism is paramount in the arid and semi-arid region which covers nearly 1/3rd of the continental area globally and depends on groundwater to sustain the ecology and livelihood of the people. One such region is semi-arid western India. This study uses seasonal isotopic (δ18O and d-excess) differences to study groundwater dynamics in semi-arid western India, in conjunction with the isotopic composition of India Summer Monsoon (ISM) to understand the rainfall - groundwater relationship, variation in recharge characteristics and quantification of groundwater recharge by rain. Some of the Important results of this study are (1) Temporal variation in the isotopic composition of shallow groundwater reveals that only ∼47% of the area is recharged by ISM rainfall; (2) Isotopic enrichment in post-monsoon season in certain regions (∼25%) indicates that deep static non-replenishable groundwater is extracted for irrigation which finds its way into shallower aquifers; (3) ∼25% (0.52 Billion Cubic Meters) of the available dynamic groundwater resource in South Gujarat is lost as submarine groundwater discharges into the Arabian Sea; (4) Groundwater in the coastal area near the Gulf of Kachchh is recharged by hypersaline waters from salt pan.

Examination of the regulation of energy metabolism, antioxidant response, and ammonia detoxification in hard clam, Mercenaria mercenaria, under hypersalinity stress

With global warming on the rise, hypersalinity events are occurring with increasing frequency due to accelerated evaporation rates of seawater. Hypersalinity affects the distribution, growth, and physiological processes of aquatic organisms, especially for osmoconforming bivalves that lack complete means of osmoregulation. In this way, knowledge concerning comprehensive metabolic regulation is limited in hypersalinity-stressed bivalves. The hard clam, Mercenaria mercenaria, is an important pond-farmed bivalve in China, with an annual output value of 150 million USD. This species can be farmed in salt pans because it is highly resistant to hypersalinity. In this study, we investigated the comprehensive pattern of metabolic regulation in hard clams under hypersalinity stress. We identified 979 metabolites in the gills of hard clams, 295 of which were differentially accumulated after different periods of exposure to hypersalinity (8 h, 1 day, and 5 days), compared with the control. Critical hypersalinity-responsive metabolites, including acyl carnitine, oxidized lipids, and several antioxidants were identified using K-means analysis. During hypersalinity exposure, the activities of hexokinase and pyruvate kinase, and the pyruvic acid content significantly increased, suggesting that glycolysis was enhanced. Alanine and glycine were identified as key free amino acids involved in osmoregulaion. After 5 days of hypersalinity exposure, the accumulation of alanine and lactic acid marked the initiation of anaerobic glycolysis. The up-regulation of amino acid catabolism and inhibition of ammonia excretion led to ammonia accumulation in the gills. Glutamine synthetase and glutamate dehydrogenase activities significantly increased to reduce ammonia toxicity. Many antioxidant metabolites, such as allantoin, cinnamic acid, and trigonelline, were dramatically up-regulated to relieve hypersalinity-induced oxidative stress. The accumulation of lysophosphatides suggested that cell membranes damaged by prolonged oxidative stress and/or hyperosmosis were dissolved by phospholipase A1. This process helped to maintain overall cellular homeostasis. Potential biomarkers of hypersalinity stress in hard clams were identified. These results will facilitate the assessment of the physiological status of hard clam in aquaculture and provide novel insights into the metabolic regulatory mechanisms of bivalves under hypersalinity stress.

Actions for the Conservation and Restoration of the Dunes and Wetlands in the Salinas of San Pedro del Pinatar: LIFE-Salinas Project (Murcia, Southeast of Spain)

The LIFE SALINAS project, co-financed by the European Union, aims for the conservation and improvement of the protected area named the Regional Park of Las Salinas and Arenales de San Pedro del Pinatar (Region of Murcia, Spain). The main objectives are, among others, to stop the erosion of the dunes in front of a 500 m long beach and to expand the breeding habitat of aquatic birds. Between the dune and the beach, a barrier was placed to protect the dune from the effects of storms. The dunes were fenced, placed with sand traps and revegetation was carried out with native species in the most degraded areas. Within the salt pans, 1800 m of new sandy dikes were built to separate the salt ponds. The results have been the recovery of the dune ecosystem and the increase in the population of nesting aquatic birds and other species, as well as an increase in the quality and production of salt.

Influences of land reclamation on soil bacterial communities of abandoned salt pans in the Yellow River Delta

AbstractReclamation has been widely accepted as a means to restore abandoned lands. Most studies focused on the improvement of land reclamation explore soil nutrients and microbial activities. However, the effects of time since reclamation on bacterial communities of abandoned salt pans are still unclear. The object of our study are is to: (i) assess the successional change of soil physicochemical properties and bacterial communities in abandoned salt pans with different reclamation histories; and (ii) determine the main limiting factors on the improvement of soil quality in abandoned salt pans. The soils in farmland [reclamation time for blank (RTBL)] and six abandoned salt pans with 1 year (RT1), 2 years (RT2), 3 years (RT3), 4 years (RT4), 8 years (RT8), and 9 years (RT9) since reclamation were sampled to investigate the temporal variation of soil properties, heavy metal content, bacterial community composition, and diversity. Results showed that the soil bulk density (BD), total dissolved salt and median particle size (MMAD) decreased with the increase of time since reclamation, while soil nutrients (soil organic matter, total nitrogen, available phosphorus, available potassium) showed an opposite trend. The bacterial α‐diversity increased first, then decreased. Land reclamation enhanced the relative abundances of Acidobacteria, Chloroflexi, and Actinobacteria but reduced the relative abundances of Proteobacteria, Gemmatimonadetes, and Bacteroidetes. Compared with RTBL, the soil nutrients and bacterial community structure in RT1, RT2, RT3, and RT4 showed a significant difference. After 8‐9 years (RT8 and RT9) of reclamation, the soil nutrients and bacterial community structure in reclaimed abandoned salt pans showed RTBL. Therefore, time since reclamation is a vital driving force for restoring soil physicochemical properties and bacterial communities in abandoned salt pans.

Natural hydrogen emanations in Namibia: Field acquisition and vegetation indexes from multispectral satellite image analysis

Natural hydrogen exploration is now active in various places of the world. Onshore, correlation between natural H2 generation and the presence of iron rich rocks especially from Archean and Neoproterozoic cratons have been observed. Emanations and accumulations of H2 have already been confirmed in such geological settings in Australia, South Africa and Brazil. The geological similitude and the presence of numerous sub circular depressions that are a good proxy for hydrogen emanations suggest that hydrogen resources may also exist in Namibia. We present here the results of a data acquisition campaign which allowed us to confirm the presence of natural hydrogen in this country in the vicinity of Neoproterozoic Banded Iron Formation. The H2 content in the soil, as in Brazil, is variable within the depressions in time and space and is particularly time sensitive across the day. Comparison of the H2 signal versus time within these two regions shows a similar behavior of the soils with an increase of the H2 flow at the middle of the day. In addition, these new data allow us to better constrain the morphological characteristics of such H2-emiting depressions. By using satellite images and digital elevation model we propose a new proxy to differentiate potentially H2-emiting features from other type of depressions such as Salt Pan. The Landsat multispectral images and their processing through NDVI and SAVI indexes, that highlight a ring of healthy vegetation around the sub circular area with scarce vegetation already observed appear able to discriminate between H2 emitting structures and other soft depressions.

Microplastic contamination in processed and unprocessed sea salts from a developing country and potential risk assessment

In aquatic environments, microplastics (MPs) are pervasive which could have a considerable negative impact on the environment, organisms and pose a risk to human health. However, knowledge about the exposure and ecological risk of MPs in the coastal ecosystems of developing countries is limited. In this study, we analyzed salt samples from five commonly consumed processed and unprocessed sea salts of different commercial brands originated from 15 salt pans in Bangladesh to assess the abundance, characteristics and potential risks of MPs. The quantities of MPs in unprocessed salts (average 195 ± 56 item/kg) were higher than those in the processed salts (average 157 ± 34 item/kg). One-way analysis of variance (ANOVA) showed significant (p < 0.05) differences among the average numbers of MPs in both processed and unprocessed salts. MP levels in this study were 2–3 times higher than those reported from some other countries. Fiber-shaped and transparent MPs were dominant in both cases. MPs less than 0.5 mm in size were the most abundant in both unprocessed (58.2%) and processed (62.2%) salts. Fourier-transform infrared spectroscopy (FTIR) analysis confirmed five types of polymers, including polyethylene terephthalate (PET−35%), polypropylene (PP−27.5%), polyethylene (PE−25%), polystyrene (PS−10%), and Nylon (2.5%) in the studied salts. The sea salts were classified as potential hazard index (PHI) levels IV to V, indicating serious MP contamination, whereas potential ecological risk factor (Ei), potential ecological risk index (RI), and pollutant load index (PLI) indicated moderate levels of pollution of MPs. Domestic and municipal wastewater effluents to Bay of Bengal and fishing activities may attributed to presence of MPs in the sea salt. These findings can be used by consumers, salt industries and policy makers to reduce MPs levels during consumption, production and policymaking.