Search Results (24)

Interactions between surface water and groundwater in arid regions regulate their response to climate and human impacts. In the salar systems of the Altiplano-Puna plateau (Bolivia, Chile, Argentina), understanding how surface waters connect to groundwater is crucial for accurate modeling and assessment. This study introduces new data and analysis using subsurface thermal profiles and modeling to identify flow patterns and possible surface water links. We document, to our knowledge, for the first time in the literature, deep-seated cooling of the subsurface caused by extreme evaporation rates. The subsurface is cooled by 4–5 degrees Celsius below the mean annual air temperature to depths greater than 50 m, even though groundwater inflow waters are elevated by 10 degrees °C due to geothermal heating. Three thermal zones are observed along the southern edge of Salar de Atacama, with temperature dropping from 28 °C to about 12 °C over 2.5 km. A 2D numerical model of groundwater and heat flow was developed to test various hydrological scenarios and understand the factors controlling the thermal regime. Two flow scenarios at the southern margin were examined: a diffuse flow model with uniform flow and flux to the surface and a focused flow model with preferential discharge at a topographic slope break. Results indicate that the focused flow scenario matches thermal data, with warm inflow water discharging into a transition zone between freshwater and brine, cooling through evaporation, re-infiltration, and surface flow, then re-emerging near lagoons at the halite nucleus margin. This research offers valuable insights into the groundwater hydraulics in the Salar de Atacama and can aid in monitoring environmental changes causally linked to lithium mining and upgradient freshwater extraction. Full article

Thick (900–1500 µm), crack-free lithium manganese oxide (LMO) electrodes with a polyvinylidene fluoride (PVDF)-based polymer electrolyte were prepared using an innovated slurry casting method. The selectivity and intercalation capacity of the thick electrodes of 900–1500 μm were evaluated in aqueous chloride solutions containing main cations in synthetic Salar de Atacama brine using cyclic voltammetry (CV) measurements. The CV data indicated that a high Li⁺ selectivity of Li/Na = 152.7 could be achieved under potentiostatic conditions. With the thickest electrode, while the mass specific intercalation capacity was 6.234 mg per gram of LMO, the area specific capacity was increased by 3–11 folds compared to that for conventional thin electrodes to 0.282 mg per square centimeter. In addition, 82% of capacity was retained over 30 intercalation/dis-intercalation cycles. XRD and electrochemical analyses revealed that both Faradaic diffusion-controlled or battery-like intercalation and Faradaic non-diffusion controlled or pseudocapacitive intercalation contributed to the capacity and selectivity. This work demonstrates a practical technology for thick electrode fabrication that promises to result in a significant reduction in manufacturing and operational costs for lithium extraction from brines. Full article

The extraction of lithium from salt flats such as the Salar de Atacama (SdA) has raised concerns about its potential impact on the local water balance. This study evaluates the possibility of including localized mining impacts on groundwater tables, lagoons, brine–freshwater mixing, evaporation, precipitation feedback, and recharge in a localized water footprint case study of lithium mining in the SdA. Using ready-to-use hydrogeological models, we primarily assessed the effects of lithium extraction on groundwater levels, evaporation, precipitation, and basin recharge dynamics. The influence on evaporation and recharge appears to be limited, with surplus evaporation due to mining accounting for a maximum of 4% of basin-wide evaporation. Regarding groundwater tables, drawdown exceeding 25 cm to several meters has largely been confined to areas that are not critical for local ecosystems. Available hydrogeological models have also helped to estimate whether the extraction of freshwater by mining companies can exacerbate groundwater drawdown during brine extraction. Consequently, non-overlapping, geographically distinct depression cones have been identified, but total water consumption by all users in the basin has not been considered. Furthermore, the aspect of model uncertainty requires further investigation, as do changes in lagoon areas and brine–freshwater mixing, which are not yet comprehensively captured by existing models. Full article

In the coming decades, anticipated population growth is projected to escalate the demand for essential resources such as NaCl, KCl, and LiCl, which are critical for human consumption, agriculture, and battery production. A substantial proportion of these salts is produced from brines using solar evaporation ponds. This article presents a one-dimensional surrogate mathematical model of an ideal solar evaporation pond working at a steady state. The ideal pond considers only water evaporation, with a uniform evaporation rate per unit area. The model’s equation, or the ideal solar evaporation law, allows calculating the ion concentration profile in an ideal pond just given the feed and discharge concentrations. The validation of the law was conducted with industrial data collected in the year 2023 in a lithium recovery plant throughout 15 ponds in series at the Salar de Atacama, Chile. The results verified that the model could accurately predict the monthly concentration profiles (R² in the range 0.9646 to 0.9864) if lithium does not precipitate in the pond. The model provides accurate values of pond inventories and area requirements for designing stages. The model’s relevance extends beyond the lithium industry to encompass any solar evaporation processes for salt recovery or solution concentration. Full article

Extremophilic bacteria from extreme environments, such as the Atacama Desert, Salar de Huasco, and Antarctica, exhibit adaptations to intense UV radiation. In this study, we investigated the genomic and structural mechanisms underlying UV resistance in three bacterial isolates identified as Bacillus velezensis PQ169, Pseudoalteromonas sp. AMH3-8, and Rugamonas violacea T1-13. Through integrative genomic analyses, we identified key genes involved in DNA-repair systems, pigment production, and spore formation. Phylogenetic analyses of aminoacidic sequences of the nucleotide excision repair (NER) system revealed conserved evolutionary patterns, indicating their essential role across diverse bacterial taxa. Structural modeling of photolyases from Pseudoalteromonas sp. AMH3-8 and R. violacea T1-13 provided further insights into protein function and interactions critical for DNA repair and UV resistance. Additionally, the presence of a complete violacein operon in R. violacea T1-13 underscores pigment biosynthesis as a crucial protective mechanism. In B. velezensis PQ169, we identified the complete set of genes responsible for sporulation, suggesting that sporulation may represent a key protective strategy employed by this bacterium in response to environmental stress. Our comprehensive approach underscores the complexity and diversity of microbial adaptations to UV stress, offering potential biotechnological applications and advancing our understanding of microbial resilience in extreme conditions. Full article

As lithium demand increases, lithium brine from hyper-arid salt flats is becoming increasingly important, although there are concerns about its extraction’s impact on the local water balance. Water footprinting could address these impacts, yet studies lack consensus on whether to classify brine as water or a mineral. This study aims to review perspectives on lithium brine accounting within and beyond the water footprint context, focused on the Salar de Atacama, Chile, and to establish accounting principles for water footprinting, following the relevant ISO standard. Outside water footprinting, four perspectives on brine classification are identified: hydro-social/perceptual, molecular–thermodynamic, precautionary, and legal. Adopting some of these perspectives, e.g., the rationale of brine’s molecular–thermodynamic similarity to freshwater, some water footprint studies argue for accounting brine as equivalent to freshwater. However, they are a minority. According to ISO, brine should not be classified as freshwater, and the type of water and its functionality should be distinguished. We suggest some saline waters below a specific salinity threshold may function as freshwater and could be included in freshwater accounting. Additionally, lithium brine extraction can induce effects on surrounding water compartments. Since conventional water footprints overlook such local effects, we propose testing a set of site-specific accounting principles through case studies. Full article

Lithium is a metal with a highly promising outlook for future global demand. Its industrial processing relies on two primary methods: production from brines through solar evaporation ponds and production from rock sources via flotation, roasting, and subsequent leaching. Chile is currently the world’s second-largest producer of lithium, surpassed only by Australia. However, Chile’s lithium production process is significantly advantaged by the exceptionally high lithium concentration in the Salar de Atacama—the highest in the world—and the region’s high solar radiation, which enables the most cost-effective solar evaporation process globally. Despite these comparative advantages, Chile’s lithium production has stagnated in recent years. This stagnation can be attributed to the need for more flexible legislation surrounding the lithium industry or an increase in the number of CEOLs (Lithium Exploitation Contracts) to regain its position as the leading global producer of lithium. Furthermore, increased investment in national universities and research centers is essential to foster the development and implementation of new, clean technologies for future projects. By addressing these challenges, Chile has the potential to solidify its role as a key player in the global lithium market while promoting sustainable industrial practices. Full article

The average lithium content in the Earth’s crust is estimated at about 0.007%. Despite this, lithium is considered abundant and widely distributed, with significant extraction from various sources. Notably, the brines in the Salar de Atacama are highlighted for their high lithium concentration ~1800 mg/L. Lithium is currently recovered from these brines through a solar evaporation process. The brine is transferred through a series of ponds, increasing the lithium concentration from 0.2% to 6% over 18 months, while decanting other minerals like potassium, magnesium, and boron. This method is the most efficient and cost-effective globally due to the Salar de Atacama’s high lithium concentration of approximately 1800 ppm and the region’s intense solar radiation, which facilitates evaporation at no economic cost. This manuscript describes in detail the lithium and potassium extraction processes used in the Salar de Atacama. Full article

A hydrogeological study of the shallowest part of the halite nucleus of the Salar de Atacama is presented, focusing on the isotopic variability in δ¹⁸O and δ²H (SMOW) in the brine. It is observed that intensive brine extraction has induced upward vertical flows from the lower aquifer, which presents with a lighter isotopic composition (δ¹⁸O: −0.87‰ to −2.49‰; δ²H: −26.04‰ to −33.25‰), toward the upper aquifer, which has more variable and enriched isotopic values. Among the possible explanations for the lighter isotopic composition of the lower aquifer waters is the influence of paleolakes formed during the wetter periods of the Late Pleistocene and Holocene that recharged the underlying aquifers. The geological structure of the Salar, including faults and the distribution of low-permeability layers, has played a determining role in the system’s hydrodynamics. This study emphasizes the need for continuous and detailed monitoring of the isotopic composition to assess the sustainability of the water resource in response to brine extraction and future climate changes. Additionally, it suggests applying this methodology to other salt flats in the region for a better understanding of hydrogeological processes in arid zones. The research provides an integrative view of the relationship between resource extraction, water management, and ecosystem conservation in one of the most important salars in the world. Full article

This study investigates water consumption in two areas with limited water resources—the Salar de Atacama and Salar de Atacama-Vertiente Pacifico basins in Chile’s Antofagasta Region—with the aim of developing strategies that incorporate social and environmental aspects into water management. A qualitative approach was employed that involved a focus group with twelve water management representatives and surveys of the general population (468 responses). Additionally, the current state of water rights in the two basins was examined and the feasibility of the proposed strategies was assessed. The findings reveal that the mining industry’s development approach is mostly viewed as negative, mainly due to inadequate community engagement, confidential consumption data, and limited government oversight. The quantitative findings indicate that 53.8% of respondents see the main obstacle as the lack of a solution satisfying both parties. Additionally, 35.3%, 24.4%, and 22.4% believe transparency, objective information provision, and detailed resource usage disclosure by mining companies would help. Adopting a comprehensive water stewardship approach that considers social and environmental factors would enable a novel contribution to a more effective and sustainable water resource management system in northern Chile, mitigating communities’ negative perceptions of the industry and facilitating the integration of communities and involved agents. Therefore, improved management and transparent collaboration among stakeholders are essential for responsible water resource use in mining. Full article

Salar de Ascotán is a high-altitude arsenic-rich salt flat exposed to high ultraviolet radiation in the Atacama Desert, Chile. It hosts unique endemic flora and fauna and is an essential habitat for migratory birds, making it an important site for conservation and protection. However, there is limited information on the resident microbiota’s diversity, genomic features, metabolic potential, and molecular mechanisms that enable it to thrive in this extreme environment. We used long- and short-read metagenomics to investigate the microbial communities in Ascotán’s water, sediment, and soil. Bacteria predominated, mainly Pseudomonadota, Acidobacteriota, and Bacteroidota, with a remarkable diversity of archaea in the soil. Following hybrid assembly, we recovered high-quality bacterial (101) and archaeal (6) metagenome-assembled genomes (MAGs), including representatives of two putative novel families of Patescibacteria and Pseudomonadota and two novel orders from the archaeal classes Halobacteriota and Thermoplasmata. We found different metabolic capabilities across distinct lineages and a widespread presence of genes related to stress response, DNA repair, and resistance to arsenic and other metals. These results highlight the remarkable diversity and taxonomic novelty of the Salar de Ascotán microbiota and its rich functional repertoire, making it able to resist different harsh conditions. The highly complete MAGs described here could serve future studies and bioprospection efforts focused on salt flat extremophiles, and contribute to enriching databases with microbial genome data from underrepresented regions of our planet. Full article

InSAR coherence-change detection (CCD) is a promising remote sensing technique that is able to map areas affected by torrential sediment transport triggered by flash floods in arid environments. CCD maps the changes in the interferometric coherence between synthetic aperture radar images (InSAR coherence), a parameter that measures the stability of the radar signal between two different SAR images, i.e., data acquisitions. In arid environments, such changes are mainly due to changes in the surface. However, the residual effect of other factors on the InSAR coherence cannot be completely excluded. Therefore, CCD-based maps contain the uncertainty of whether the detected changes are actual changes in the observed surface or just errors related to those residual effects. Thus, in this paper, the results of four CCD mapping methods, with different degrees of complexity and sensitivity to the different factors affecting the InSAR coherence, are compared in order to evaluate the existence of the errors and their importance. The obtained CCD maps are also compared with changes in satellite optical images and a field campaign. The results lead to the conclusion that CCD maps are reliable in the identification of the zones affected by sediment transport, although the precision in the delimitation of the affected area remains an open issue. However, highly rugged relief areas still require a thorough analysis of the results in order to discard the geometric effects related to the perpendicular baseline. Full article

Coherence change detection (CCD) is a remote sensing technique used to map phenomena that, under certain conditions, can be directly related to changes in Interferometric SAR (InSAR) coherence. Mapping the areas affected by sediment transport events in arid environments is one of the most common applications of CCD. However, the reliability of these maps remains an unsolved issue. This paper focuses on verifying that InSAR coherence is indeed able to detect all the fluvial sediment transport events that have actually mobilised sediments in arid environments by building a classification model and validating its results. The proposed methodology is tested in three study areas in Salar de Atacama, Chile, using three years of Sentinel data plus a fourth year for validation, and meteorological records of rainfall, the relative humidity of the air and snow cover. The results prove that InSAR coherence can be used to remotely detect sediment transport events related to flash floods in arid environments, that it might have a greater detection ability than meteorological records and that the perpendicular baseline does have a relevant effect on the InSAR coherence that needs to be considered. All these findings will increase the reliability of maps based on InSAR coherence. In addition, the proposed method will allow focusing the mapping tasks only on the relevant dates and, once calibrated, the classification model will enable the automatised remote detection of new events. Full article

Electromembrane processes for LiOH production from lithium brines obtained from solar evaporation ponds in production processes of the Salar de Atacama are considered. In order to analyze high concentrations’ effect on ion exchange membranes, the use of concentrated LiCl aqueous solutions in a bipolar membrane electrodialysis process to produce LiOH solutions higher than 3.0% by mass is initially investigated. For this purpose, a mathematical model based on the Nernst–Planck equation is developed and validated, and a parametric study is simulated considering as input variables electrolyte concentrations, applied current density, stack design, process design and membrane characteristics. As a novelty, this mathematical model allows estimating LiOH production in a wide concentration range of LiCl, HCl and LiOH solutions and its effect on the process, providing data on final LiOH solution purity, current efficiency, specific electricity consumption and membrane performance. Among the main results, a concentration of 4.0% to 4.5% by LiOH mass is achieved, with a solution purity higher than 95% by mass and specific electrical energy consumption close to 4.0 kWh/kg. The work performed provides key information on process sensitivity to operating conditions and process design characteristics. These results serve as a guide in the application of this technology to lithium hydroxide production. Full article

In extreme environments, microbial organisms reside in pockets with locally habitable conditions. Micro-climates conducive to the persistence of life in an otherwise inhospitable environment—“refugia”—are spatially restricted and can be micro- to centimeters in extent. If martian microbes are preserved in fossil refugia, this presents a double-edged sword for biosignature exploration: these locations will be specific and targetable but small and difficult to find. To better understand what types of features could be refugia in martian salt-encrusted basins, we explore a case study of two terrestrial habitats in salt-encrusted paleo-lake basins (salars): Salar Grande (SG) in the Atacama Desert and Salar de Pajonales (SdP) in the Altiplano Puna plateau of Chile. We review the formation of salt constructs within SG and SdP, which are the features that serve as refugia in those salars, and we explore the connection between the formation of salt constructs at the local scale with the larger-scale geologic phenomena that enable their formation. Our evaluation of terrestrial salars informs an assessment of which chloride basins on Mars might have had a high potential to form life-hosting salt constructs and may preserve biosignatures, or even host extant life. Our survey of martian salars identifies 102 salars in regions with a geographic context conducive to the formation of salt constructs, of which 17 have HiRISE coverage. We investigate these 17 martian salars with HiRISE coverage and locate the presence of possible salt constructs in 16 of them. Salt constructs are features that have may have been continuously habitable for the past ~3.8 Byr, have exceptional preservation potential, and are accessible by robotic exploration. Future work could explore in detail the mechanisms involved in the formation of the topographic features we identified in salt-encrusted basins on Mars to test the hypothesis that they are salt constructs. Full article