Hydrochemistry of various stages of Brine in subsoil salt-pan

Manufacture of common salt by evaporation of natural brine has been renowned from past. The southern state of Tamil nadu in India, 75% of the salt is made by solar evaporation of sea brine, 20% from subsoil brine and therefore the rest from backwater. For the manufacture of salt and its by-products by the evaporation of brine, the information of each the composition of the brine and its phase chemistry is important. Underground brine (subsoil) is considered to be the sea water cut-off from oceans and concentrated by sunlight. It contains the elements of chloride, sulphate, calcium, magnesium, sodium and potassium in higher proportion. The physical parameter of rainfall data was collected because it interferes by diluting the brine and reducing the rate of evaporation. The monitoring of the physical and chemical parameters of brine at various stages viz, source, reservoir, condenser, crystallizer and bittern of the subsoil salt-pan gives plentiful possibilities for the management of the salt-pans. The results of chemical parameters and their seasonal dissimilarities were studied for a period of one year. (Jan-Dec 2019).

Genomic Characterization of a Prophage, Smhb1, That Infects Salinivibrio kushneri BNH Isolated from a Namib Desert Saline Spring

Recent years have seen the classification and reclassification of many viruses related to the model enterobacterial phage P2. Here, we report the identification of a prophage (Smhb1) that infects Salinivibrio kushneri BNH isolated from a Namib Desert salt pan (playa). Analysis of the genome revealed that it showed the greatest similarity to P2-like phages that infect Vibrio species and showed no relation to any of the previously described Salinivibrio-infecting phages. Despite being distantly related to these Vibrio infecting phages and sharing the same modular gene arrangement as seen in most P2-like viruses, the nucleotide identity to its closest relatives suggest that, for now, Smhb1 is the lone member of the Peduovirus genus Playavirus. Although host range testing was not extensive and no secondary host could be identified for Smhb1, genomic evidence suggests that the phage is capable of infecting other Salinivibrio species, including Salinivibrio proteolyticus DV isolated from the same playa. Taken together, the analysis presented here demonstrates how adaptable the P2 phage model can be.

Potential and limits of vegetation indices compared to evaporite mineral indices for soil salinity discrimination and mapping

The study aims to analyze the ability of the most popular and widely used vegetation indices (VI’s), including NDVI, SAVI, EVI and TDVI, to discriminate and map soil salt contents compared to the potential of evaporite mineral indices such as SSSI and NDGI. The proposed methodology leverages on two complementary parts exploiting simulated and imagery data acquired over two study areas, i.e. Kuwait-State and Omongwa salt-pan in Namibia. In the first part, a field survey was conducted on the Kuwait site and 100 soil samples with various salinity levels and contents were collected; as well as, herbaceous vegetation cover canopy (alfalfa and forage plants) with various LAI coverage rates. In a Goniometric-Laboratory, the spectral signatures of all samples were measured and transformed using the continuum removed reflectance spectrum (CRRS) approach. Subsequently, they were resampled and convolved in the solar-reflective spectral bands of Landsat-OLI, and converted to the considered indices. Meanwhile, soil laboratory analyses were accomplished to measure pHs, electrical conductivity (EC-Lab), the major soluble cations and anions; thereby the sodium adsorption ratio was calculated. These elements support the investigation of the relationship between the spectral signature of each soil sample and its salt content. Furthermore, on the Omongwa salt-pan site, a Landsat-OLI image was acquired, pre-processed and converted to the investigated indices. Mineralogical ground-truth information collected during previous field work and an accurate Lidar DEM were used for the characterization and validation procedures on this second site. The obtained results demonstrated that regardless of the data source (simulation or image), the study site and the applied analysis methods, it is impossible for VI's to discriminate or to predict soil salinity. In fact, the spectral analysis revealed strong confusion between signals resulting from salt-crust and soil optical properties in the VNIR wavebands. The CRRS transformation highlighted the complete absence of salt absorption features in the blue, red and NIR wavelengths. As well as the analysis in 2D spectral-space pointed-out how VI’s compress and completely remove the signal fraction emitted by the soil background. Moreover, statistical regressions (p ˂ 0.05) between VI's and EC-Lab showed insignificant fits for SAVI, EVI and TDVI (R2 ≤ 0.06), and for NDVI (R2 of 0.35). Although the Omongwa is a natural flat salt playa, the four derived VI’s from OLI image are completely unable to detect the slightest grain of salt in the soil. Contrariwise, analyses of spectral signatures and CRRS highlighted the potential of the SWIR spectral domain to distinguish salt content in soil regardless of its optical properties. Likewise, according to Kuwait spectral data and EC-Lab analysis, NDGI and SSSI incorporating SWIR wavebands have performed very well and similarly (R2 of 0.72) for the differentiation of salt-affected soil classes. These statistical results were also corroborated visually by the maps derived from these evaporite indices over the salt-pan site, as well as by their consistency with the validation points representing the ground truth. However, although both the indices have mapped the salinity patterns almost similarly, NDGI further highlights the gypsum content. While the SSSI show greater sensitivity to salt crusts present in the pan area that are formed from different mineral sources (i.e., halite, gypsum, etc.).

Spatio-temporal modelling for the evaluation of an altered Indian saline Ramsar site and its drivers for ecosystem management and restoration

Saline lakes occupy 44% and 23% of the volume and area of all lakes that are tending to suffer from extended dryness, reduced hydro period, or complete desiccation by 2025. The current study is conducted on Sambhar Salt Lake, the largest inland saline Ramsar, site of India, contributing to 9.86% of total salt production. The lake is under threat due to illegal salt pan encroachment, losing brine worth 300 million USD. The objective was to identify the key drivers that affect the lake at a landscape level. Geospatial modelling was conducted for 96 years (1963–2059) at a decadal scale, integrating ground data (birds-soil-water). Land Use Land Cover (LULC) classification was conducted using CORONA aerial imagery of 1963, along with Landsat imageries, using supervised classification for 1972, 1981, 1992, 2009, and 2019, and future prediction for 2029, 2039, 2049, and 2059. Further, images were classified into 8 classes that include the Aravali hills, barren land, saline soil, salt crust, salt pans, wetland, settlement, and vegetation. Past trends show a reduction of wetland from 30.7 to 3.4% at a constant rate (4.23%) to saline soil, which subsequently seemed to increase by 9.3%, increasing thereby the barren land by 4.2%; salt pans by 6.6%, and settlement by 1.2% till 2019. Future predictions show loss of 40% wetland and 120% of saline soil and net increase in 30% vegetation, 40% settlement, 10% salt pan, 5% barren land, and a net loss of 20%, each by Aravali hills and salt crust. Additionally, the ground result shows its alteration and reduction of migratory birds from 3 million to 3000. In the light of UN Decade on Ecosystem Restoration (2021–2030), restoration strategies are suggested; if delayed, more restoration capital may be required than its revenue generation.

Shallow groundwater chemical evolution, isotopic hyperfiltration, and salt pan formation in a hypersaline endorheic basin: Pilot Valley, Great Basin, USA

Endorheic basin brines are of economic significance as sources of boron, iodine, magnesium, potassium, sodium sulfate, sodium carbonate, and tungsten, and they are a major source of the critical metal lithium. Although evaporation is the primary hypersalinization driver for evaporative water bodies, recent investigations have proposed more novel mechanisms for some subsurface brine. This investigation explores shallow groundwater hypersalinization. The chemical evolution and isotopic fractionation of shallow hypersaline groundwater in the clay-rich arid endorheic basin sediments of Pilot Valley, Great Basin (USA), were investigated. Groundwater evolves from fresh in the mountain bedrock and alluvial fans, to brackish and saline at the alluvial fan–playa interface, and to hypersaline in the upper 12 m of basin sediments. Alluvial fan systems are isolated from each other and have varying groundwater 3H and 14C travel times. Nonevaporative in-situ isotopic fractionation of up to −8‰ in δ18O is attributed to clay sequence hyperfiltration. Groundwater flow-path sulfate and chloride mineral dissolution is the primary driving mechanism for both interface and basin groundwater evolution. Evaporation only impacts the groundwater quality in a small portion of the basin where the groundwater is within ~1 m of the ground surface. Here capillary action carries dissolved soluble salts to the land surface. Episodic flooding redissolves and carries the precipitated salt to the annually flooded salt pan where it accumulates as a salt crust during the dry season. The Pilot Valley model may help explain the buildup accumulative layers of soluble salt that when remobilized becomes subsurface brine.

Plant Growth Promotion Function of Bacillus sp. Strains Isolated from Salt-Pan Rhizosphere and Their Biocontrol Potential against Macrophomina phaseolina

In recent decades, intensive crop management has involved excessive use of pesticides or fertilizers, compromising environmental integrity and public health. Accordingly, there has been worldwide pressure to find an eco-friendly and safe strategy to ensure agricultural productivity. Among alternative approaches, Plant Growth-Promoting (PGP) rhizobacteria are receiving increasing attention as suitable biocontrol agents against agricultural pests. In the present study, 22 spore-forming bacteria were selected among a salt-pan rhizobacteria collection for their PGP traits and their antagonistic activity against the plant pathogen fungus Macrophomina phaseolina. Based on the higher antifungal activity, strain RHFS10, identified as Bacillus vallismortis, was further examined and cell-free supernatant assays, column purification, and tandem mass spectrometry were employed to purify and preliminarily identify the antifungal metabolites. Interestingly, the minimum inhibitory concentration assessed for the fractions active against M. phaseolina was 10 times lower and more stable than the one estimated for the commercial fungicide pentachloronitrobenzene. These results suggest the use of B. vallismortis strain RHFS10 as a potential plant growth-promoting rhizobacteria as an alternative to chemical pesticides to efficiently control the phytopathogenic fungus M. phaseolina.