Advance indicator mineral research integrating field concentration and mineral identification techniques improves the exploration of critical minerals in the areas of transported cover. This article presents the development and evaluation of improved research methods for identification of heavy and indicator minerals, which are commonly applied in the exploration of precious, base, and critical metals. The results demonstrate that indicator mineral separation can be significantly optimized through tailored sample handling and enrichment techniques, enabling the selection of suitable processing methods for samples of varying sizes, grain-size fractions, and specific gravity classes. The use of on-site analytical methods, particularly portable XRD and XRF analyzers, markedly accelerates exploration workflows while reducing the reliance on costly laboratory analyses, resulting in substantial cost savings. In addition, advanced laboratory techniques, such as automated mineral identification using FE-SEM-EDS, enhance the efficiency and accuracy of mineral identification and provide reliable validation for field-based analyses. Several case studies in northern Finland confirm the robustness, usability, and data processing performance of both field and laboratory methods. This new concept has proven effective for discovering new sources of critical minerals, accelerating exploration, and reducing costs. Practical piloting further demonstrates the applicability of the developed methodological concept, with documented outcomes supporting industrial use and future exploration projects.
IntroductionUltramafic rocks rich in iron-bearing minerals are promising sources of geochemical hydrogen generation through water-rock reactions.MethodsThis study investigates how mineral composition, temperature, pressure, and initial pH influence hydrogen generation during hydrothermal water-rock reactions, using laboratory experiments and reactive-transport/thermodynamic simulations. Three novel contributions are made: a controlled experimental dataset isolating the effect of fayalite-to-forsterite ratio on hydrogen yield; a geochemical model combining thermodynamic equilibrium with Arrhenius kinetics, validated against experiments and used to explore conditions beyond the tested range; and an extension to core-scale flow-through experiments demonstrating that transport processes in fractured rock fundamentally alter hydrogen generation behavior relative to powdered-sample systems.Results & DiscussionMineral composition is the dominant control on hydrogen yield, followed by temperature. pH effects are pressure-dependent, and pressure alone has a modest positive effect. These results highlight critical parameter interactions and transport-reaction coupling that must be resolved before laboratory findings can be reliably translated to field-scale geological hydrogen systems.
Amphibole plays a pivotal role in mediating the flux of volatiles and partial melting that ultimately contribute to arc magmatism. The influence of amphibole from the lower crust to the upper mantle remains unclear due to limited opportunities for observation. Amphibole-rich ultramafic rock characterized by large poikilitic hornblende grains with olivine and pyroxenes occurs in the Nishidohira metamorphic rocks in the southern Abukuma Mountains of Northeast Japan (we call poikilitic hornblende pyroxenite hereafter). Amphibole exhibit zoning in color and chemical composition: the dark core has higher TiO2 and Al2O3 contents than the light green rims. Dark-colored high-TiO2 pargasitic amphibole formed early from magmatic melts. Melt compositions calculated from the dark-colored amphibole core based on melt-mineral partitioning indicate that the poikilitic hornblende pyroxenite resulted from adakitic magmatic activity. Reactions between pre-existing ultramafic rock and adakitic melt are likely to form poikilitic hornblende pyroxenite when the melt/rock ratio is low, and hornblende gabbro when the ratio is high. The U-Pb zircon age of approximately 120 Ma for poikilitic hornblende pyroxenite and associated hornblende gabbro is interpreted as a magmatic age. In the Early Cretaceous tectonic framework of Northeast Japan, adakitic magmatism is attributed to the westward subduction of the Izanagi (or Kula) plate beneath the eastern margin of the Eurasian Plate.
Quantitative modeling is a powerful tool that allows us to develop an understanding of identity and extent of igneous processes on Earth and other planetary bodies. Such models are built upon data from experiments that describe the major and trace element behavior among the phases in a system of interest. Previous work on the analysis of calibration datasets has been done for many of the mafic rock forming minerals such as plagioclase, clinopyroxene, amphibole, olivine, and garnet. What is missing is an evaluation of the sources of uncertainty in the trace element orthopyroxene/melt partitioning experiments. The goal of this investigation is to document the identity and magnitude of a number of sources of uncertainty that were observed in the experimental database for low-Ca pyroxene/melt trace element partitioning. These include multiphase analyses (e.g., mineral and glass analysis in the same analytical volume) as well as uncertainty with regards to the specific structural state of the low-Ca pyroxene in the experiments (e.g., is the mineral reported orthopyroxene or pigeonite?). Our findings confirm earlier work documenting the dependence of the orthopyroxene/melt partition coefficients for the high field strength and rare earth elements on the Ca content of pyroxene. However, the development of predictive expressions for trace element partitioning between orthopyroxene and melt is compromised by a number of database characteristics related to commonly applied analytical methods and phase determinations. Specifically, the average composition of the experimental orthopyroxene and liquids overlap, but is different for each element (e.g., the average composition of all experiments where Sm was determined is different but overlap with those where Zr was determined). Second, the reported analytical uncertainty is significantly higher for experiments where the trace element determinations were done by laser inductively coupled plasma mass spectroscopy compared to secondary ion mass spectroscopy - an observation attributable to the differences in analytical volume between two analytical techniques. Lastly, most experimental studies did not determine the specific low-Ca pyroxene present but rather used the calcium content alone to identify orthopyroxene vs. pigeonite which we showed as unreliable. Taken together, these database characteristics impact any regression analysis and result in an internal bias in the predicted behavior of trace elements. Our ability to “fix” the database is inhibited by the current convention of publishing experimental partitioning data as averages and not publishing individual analyses - making essentially impossible to quantitatively understand the magnitude and sources of error.
Lithium is a critical element in battery technology for renewable energy storage applications. The mineral offers potential solutions to the current surge in global energy demand and can position Nigeria as a potential key player in the lithium supply chain. However, little to nothing is known of the lithium deposits in Nigeria. This review explores the formation, geology, and ongoing exploration activities of lithium in Nigeria. The study provides an overview of the geological settings and mineralogical characteristics of the Nigerian lithium-bearing pegmatites and ores, comparing them with global deposits. It also examines current lithium mining and processing techniques, identifies significant developmental challenges and recommends potential solutions to lithium exploration in Nigeria. Additionally, the paper discusses Nigeria’s policy landscape, investment gaps, and the government’s efforts to establish a sustainable lithium processing industry. The findings emphasise the need for best mineral extraction practices, improved beneficiation technologies, and strategic policy reforms to enhance Nigeria’s position in the global lithium market. The study concludes that with proper investment and regulatory frameworks, Nigeria has the potential to become a significant lithium supplier and contribute to the global transition towards clean energy.
The Lebowa Granite Suite (LGS), representing the youngest component of the Bushveld Igneous Complex (BIC) magmatism, is closely associated with numerous polymetallic mineralisation assemblages. The intrusion of the LGS was accompanied by both long-lived mineralising hydrothermal systems and the concomitant reactivation of regional faults, resulting in endogranitic and exogranitic mineralisation. Despite extensive studies on the mineralisation, classification, and geochemistry of the LGS as the host rock, the different facies of the LGS have not been extensively appraised to elucidate their petrological evolution from a pristine and barren state to differentiated-metasomatised fertile phases that host polymetallic mineralisation. Hence, the current study investigated two drill cores within the eastern limb of the BIC. These cores were logged, and a total of 25 samples representing Nebo, Bobbejaankop, Klipkloof, and Lease granites were collected for petrography and whole-rock geochemical studies. The BHDD 003 drill is characteristic of Nebo granite: leucocratic, equigranular, and biotite-bearing with common perthitic alkali-feldspar and biotite minerals showing pervasive sericite and chloritic alterations, respectively. The 648 KS/1 drill intersected Bobbejaankop granite, principally hypidiomorphic, characterized by pervasive sericite and minor microcline alterations in addition to chloritized magmatic biotite and hornblende. The Bobbejaankop granite grades into Lease granite, a fine-grained variety. The Klipkloof granite, generally microgranitic but often granophyric, caps the Bobbejaankop granite at the top. The geochemical results indicate that the Nebo, Bobbejaankop, Klipkloof, and Lease granites are ferroan, calcic to alkali-calcic, peraluminous A-type, and developed within intracratonic settings. The Bobbejaankop granite shows evidence of higher fractionation than the Nebo granite, with evidence of intensive magmatic-hydrothermal alterations revealed by TEDI (Ba x (Sr/Rb)), Zr/Hf vs Y/Ho, Nb/Ta ratios, and normalised REE plots. Furthermore, the Bobbejaankop, Klipkloof, and Lease granites possess lower Zr/Hf (<∼25), indicative of higher hydrothermal affluence and consequently a higher fertility index than the Nebo granite, implying that the former granites are more likely to host endogranitic polymetallic deposits. Normalised La/Yb ratios indicate that the facies of the LGS are also cogenetic, likely emanating from the differentiation of mantle-derived alkaline mafic magma, similar to RLS, which is dominated by the removal of alkalis via subsolidus hydrothermal alteration processes.
IntroductionDifferences exist in the morphological features of asbestos and the abilities of measuring tools over the spectrum of the particle size distribution in ground bulk mineral powders. Amphiboles and serpentine most often occur naturally without an asbestos component, although amphiboles typically produce elongate mineral particles when ground. For reasons of defining health risks, attempts to conclusively distinguish between asbestos and non-asbestos occurrences are warranted. Asbestiform morphological characteristics are more readily visible in the coarser size fraction of a ground mineral powder. Therefore, a procedure was developed to isolate and analyze the coarse size fraction of mineral mixtures for asbestos.MethodsThe morphological characteristics of asbestos spiked into ground mineral powders at 100 ppm and 500 ppm concentrations were evaluated. Three types of asbestos, Lone Pine tremolite, Health and Safety Laboratory (HSL) chrysotile, and short-fiber Calidria chrysotile, were spiked into a coarsely crushed talc matrix. Spiked samples were aggressively co-ground to simulate a milled mineral powder final product. The coarsest particles in the mixture were isolated using a wet-sieving technique and evaluated by scanning electron microscopy (SEM) and polarizing light microscopy (PLM). A production-scale ultrafine milled talc sample containing trace amounts of amphibole was also analyzed using the wet-sieve approach.ResultsAsbestos was readily detected by both SEM and PLM in the coarsest size fraction at these low concentrations, despite aggressive grinding. Classic morphological features of asbestos, such as occurrence in bundles and presence of long, thin fibers showing curvature, were observed for all types of asbestos by both SEM and PLM at both concentrations. There were no morphology differences between the 500 ppm and 100 ppm concentrations, although fewer particles were observed in the latter, as expected. Trace amounts of amphibole asbestos were detected in the production-scale ultrafine milled talc sample which showed classic asbestiform morphology even though the sample had been ground to a 1.5 μm median particle size.DiscussionResults show that the presence of asbestos can be confirmed in ground bulk mineral powders using this analysis approach and detection by SEM and/or PLM is limited only by the amount of material analyzed. This approach is opposite to types of asbestos analyses that concentrate on the finest particles (such as those performed by transmission electron microscopy (TEM)), which can sometimes be inconclusive. The production-scale ultrafine milled talc sample provided proof of concept for this approach. The techniques described can be used to accurately determine if a mineral product contains asbestos or an asbestos component.
Diamonds are unique samples that enlarge our vision of the physical and chemical reactions occurring in Earth’s deep, inaccessible mantle. By investigating the minerals and fluids trapped within them, it is possible to ascertain the key conditions relevant to diamond formation, such as pressure, temperature, and oxygen fugacity. In this study, we investigated a diamond from the Rio Sorriso area, Juína (Brazil), a site known for the high abundance of sublithospheric diamonds discovered there. The diamond contained both colorless and greenish optically visible inclusions of Na–Cr-bearing diopside, high-Mg olivine, and enstatite. Thermobarometric estimates of the polished and entrapped inclusions suggest that the diamond likely formed at pressures between 4 and 5 GPa and temperatures of 1,050 °C–1,150 °C. Major and trace elements data from one polished clinopyroxene provide evidence of interaction between the local peridotite and an oxidized Na-rich carbonated melt—a generally proposed growth medium from which diamonds may have crystallized. Our study thus demonstrates that diamonds from underneath the Amazonian craton did not originate solely at lower mantle depths but also within a metasomatized lithospheric mantle.
As an important link in the global carbon cycle, the carbon sink function of inland water bodies has attracted much attention in recent years. In particular, the autochthonous production (AP) associated with aquatic photosynthesis in karst surface waters converts dissolved inorganic carbon (DIC) into autochthonous organic carbon (the “carbon sink by carbonate weathering coupled with aquatic photosynthesis, CCW”), which is the key to the formation of a long-term stable carbonate weathering sink. After nearly 20 years of development, the “CCW” theory, as a nature-based solution, has been found to have a win-win mechanism of sink enhancement and water environment improvement. The specific mechanism is that dissolved aquatic CO2 (CO2(aq)) fertilization can effectively alleviate the carbon limitation of the water body, promote the productivity of the water body to achieve carbon sink enhancement, and achieve the inhibition of eutrophication through the modification of the biological structure and the co-precipitation of CaCO3 and phosphorus to enhance the efficiency of phosphorus removal. In conclusion, the carbon fertilization of AP effect in karst surface water bodies has a huge carbon storage capacity and water environment improvement capacity. This paper reviews the detailed process of AP effect in karst surface waters, especially about the possibility of carbon sink and eutrophication mitigation win-win by CO2 fertilization of water bodies and its mechanism of action. Finally, based on the current research gaps, we outline the future research priorities of AP in karst surface water bodies. This study will provide new theoretical basis and scientific support for the regulation of carbon sinks and water quality safety in karst surface waters.
Globally peatlands store 25% of global soil organic carbon but this large carbon store is at risk under climate change and from widespread anthropogenic disturbances. The impact of climate change on tropical peatlands, which represent 23%–30% of the global peatland area, is particularly poorly understood and Earth System Models do not yet include a suitable representation of the soil carbon cycle for tropical peatlands. Peat decomposition via soil heterotrophic respiration to CO2 (SHR-CO2) is a main component of the peatland carbon cycle. However, the lack of consensus on the importance of different drivers and the scarcity of empirical data hinders model development. Therefore, this study reviews the drivers of SHR-CO2 (moisture, temperature, decomposability and, nutrients and decomposers) for tropical peatlands. We compile available empirical data to inform model development; and highlight priorities for future experimental work that would enable further model refinement. We point out that the sharp decrease of SHR-CO2 under anoxic water-saturated conditions is a major parameter for tropical peat decomposition and the ratio of SHR-CO2 under anoxic conditions to the SHR-CO2 at the optimum moisture is 0.10 ± 0.08. Additionally, we highlight that, at present, the common assumption that SHR-CO2 doubles with an 10°C increase (Q10 of ca. 2) remains the most parsimonious option considering the lack of empirical data to establish a more process-based peatland SHR-CO2 temperature relationship. Finally, we identify three priorities to advance tropical peatland model improvement: (1) narrowing the constraint on the optimum moisture range for SHR-CO2 in tropical peatlands, (2) investigating the interaction between moisture and temperature sensitivity, and (3) identifying the most widely applicable metric to characterise peat decomposability that might enable quantitative comparison across the tropics.
Leaf wax biomarkers permit chemotaxonomic identification of past vegetation in archaeological contexts. At the birthplace of Buddha, Lumbini in Nepal, archaeological evidence of a multi-phase tree shrine from the earliest beginnings of Buddhism has been uncovered in archaeological sequences within the Mayadevi Temple. As yet there has been no scientific attempt to establish the species of tree(s) occupying the “central open space” within the ancient shrine, or in the wider sacred landscape, despite this being an issue of significance for understanding early Buddhist practice. The cuticular leaf waxes of three tree species sacred and venerated in Buddhist tradition - Saraca asoca, F. religiosa and Shorea robusta were characterised, with additional identification achieved following hydrolysis of triterpenoid esters. Diagnostic distributions of triterpenoid esters were observed for F. religiosa leaves (β-amyrin, α-amyrin and lupeol esters with C16:0, C18:2, C18:1, C18:0, C20:2, C20:1, C20:0, and C22:0 fatty acids, Ψ-taraxasteryl eicosanoate, Ψ-taraxasterol behenate) and S. robusta leaves (taraxeryl linoleate). Chronologically controlled and contextualised analyses of archaeological soil lipids characterise the triterpenoid ester distribution within the main shrine’s “central open space”, an adjacent palaeo-channel, the monastic site and early village mound. The presence of β-amyrin palmitate and α-amyrin palmitate, with longer-chain homologues (β-amyrin stearate, α-amyrin stearate and β-amyrin eicosadienoate) in the soil indicate that the F. religiosa tree occupied the “central open space” throughout development of the tree shrine, alongside a F. religiosa grove close to the palaeo-channel adjacent to the Mayadevi Temple. Beyond these locations, F. religiosa occurred only rarely in the historic Lumbini landscape, although there are enhanced triterpenoid esters in a foundation pit in the village and in an occupation surface from the monastic site; there is no biomarker evidence of other trees. F. religiosa is a sacred tree species of long-standing in South Asia; our analysis indicates its transition into Buddhist religious culture and demonstrates that leaf-wax biomarkers can provide enhanced visibility to archaeological tree shrines in South Asia.
Mine wastes can pose environmental and human health risks, especially when they contain high concentrations of potentially toxic metal(loid)s. In this study, the geochemistry (bulk and sequential extraction analysis, paste pH) and mineralogy (X-ray diffraction, scanning electron microscopy, electron microprobe analysis) of Co in mine wastes from Cobalt (Canada) and Cornwall (UK) were characterised to assess potential Co and other metal(loid) mobility in the aquatic environment. Cobalt concentrations in Nipissing high- and low-grade tailings at Cobalt were high (up to 5,630 mg kg −1 and 1,230 mg kg −1 , respectively), and were several orders of magnitude higher than those at Poldice, Wheal Unity, and Dolcoath in Cornwall (average 40 mg kg −1 , 76 mg kg −1 , and 59 mg kg −1 , respectively). Community Bureau of Reference (BCR)-sequential extraction analysis suggested that Co was equally mobile within the samples from Cobalt and Cornwall, with averages of 46% extracted in the exchangeable fraction. Erythrite was the most important secondary Co-bearing mineral that occurred widely in the Nipissing tailings. Other Co-bearing secondary minerals included arseniosiderite, scorodite, and Fe oxyhydroxides. Primary Co-bearing minerals identified included cobaltite and safflorite-skutterudite, and Co was also taken up in primary arsenopyrite, loellingite, pyrite and chalcopyrite. At the sites in Cornwall, however, Co-bearing primary and secondary minerals were not identified. Instead, Co was observed as a trace component in primary arsenopyrite, pyrite, and chalcopyrite and in secondary scorodite and Fe-Mn oxyhydroxides. Despite these mineralogical and other geological and processing differences, Co showed consistently high potential for mobilization from the wastes. In addition, risk assessment codes for Co fell in the medium to very high risk category in the aquatic and non-aquatic environments. This classification suggests that the mine waste-hosted Co is likely to affect humans via the food chain. Further research is required to determine if Co shows similar behaviour in mine wastes globally.
Under arid and semi-arid climate conditions, as is the case in many Moroccan regions, the availability and quality of water are the main keys to the sustainable development of agricultural zones. In the Fritissa region covering Middle Moulouya and a part of Lower Moulouya, North-eastern Morocco, irrigation practices are necessary for agricultural activities, in an environment with significant population growth, and limited water resources. The main aim of this study is to assess the quality of groundwater and its suitability for irrigation purposes, and to determine the possible water-rock interaction processes that influence the groundwater chemistry. The approach is based on the analysis of major ions contents and the calculation of quality indices namely pH, Electrical conductivity (EC), Total Dissolved Solids (TDS), Total Hardness (TH), Sodium Percentage (Na%), Residual Sodium Carbonate (RSC), Sodium Adsorption Ratio (SAR) and Permeability Index (PI) for 94 groundwater samples. Piper classification is used to determine the chemical water facies, while commonly used distribution and geochemical diagrams helped to discuss the possible interaction processes between water and aquifer rocks. The studied groundwater showed varying values for pH (5.8–8.8), salinity (367–3301 mg/L) and total hardness (15–186 mg/l as CaCO 3 ). Ca-Mg-HCO 3 , Ca-Mg-SO 4 -Cl, and mixed water facies types are found, while one sample showed Na-K-SO 4 -Cl facies. The plotting of samples in Gibbs diagrams suggests possible water-rock interactions, that are confirmed by geochemical distribution diagrams. The Wilcox diagram showed that most of the water samples are of excellent to good and good to permissible categories, while the US salinity Hazard diagram revealed low sodium hazard and low, medium and high levels of salinity. Groundwater is suitable for irrigation according to current international standards if some precautions are considered.
Urban populations and the sprawl of urban environments are increasing in the United States as well as globally. The local hydrologic cycle is directly impacted by urban development through greater generation of surface runoff and export of water through subterranean pipes networks to surface water bodies. These pipe networks carry waters that have potentially dramatic effects on the chemistry of groundwater and surface water bodies. In this work, we sampled waters from the Olentangy River and two subterranean outfalls that flow into the river in Columbus, Ohio United States. We measured the major ion, nutrient, and dissolved silica concentrations of each water source to identify how the urban landscape impacts the chemistry of a river that travels from an agricultural landscape to an urban environment. The outfalls had elevated concentrations of all major ions (Na+, K+, Mg2+, Ca2+, Cl−, SO42-) and H4SiO4. However, the Olentangy river typically had greater NO3− and soluble reactive phosphorus (SRP) concentrations. Sources of elevated ion export include road salts and combined storm runoff (Na+, Cl−), municipal water treatment practices (K+, Na+, SO42-), and concrete pipe weathering (Ca2+, Mg2+, K+, H4SiO4, SO42-). Utilizing stable isotopes of water, δ18O and δ2H, we identified that the water in the pipe networks is typically a mix of multiple precipitation events, but there is evidence of flushing following high-volume precipitation events. The contribution of high TDS waters from subterranean urban outfalls modified the ion abundance in the Olentangy river and produces a tendency towards freshwater salinization syndrome. This is particularly apparent when comparing the chemistry of the urban Olentangy to the agricultural corridor of the river and its other source waters. This research details the transformation of a river as it flows from an agricultural to urban landscape and provides data on the chemistry of source waters that facilitate the river’s chemical changes.
The glacier ice algae Ancylonema alaskanum and Ancylonema nordenskiöldii grow in harsh dynamic environments on bare ice surfaces. In these environments, they contribute to the continuous darkening of the ice surface, which in turn accelerates the ice melt. However, investigation into their adaptation and resilience in these environments is necessary in order to understand their robustness and potential for increasing the intensity of blooms. In this study, it was examined how variations in environmental parameters such as pH, salinity, light and temperature impacted the photophysiology of the glacier ice algae during a bloom in Greenland. Through in situ incubations and pulse-amplitude-modulation (PAM) fluorometric measurements, the photophysiological responses of algal cells were assessed. Results suggest that light intensity significantly influences glacier ice algae photophysiology, with cells exhibiting better performance (in terms of a higher theoretical maximum light coefficient and maximum quantum efficiency) under lower light intensity. Moreover, while light emerges as the primary driver of photophysiology, glacier ice algae demonstrate tolerance to a broad range of pH and temperatures four times higher than those experienced during Greenland’s summer.
Hydrogen (H 2 ) is widely viewed as critical to the decarbonization of industry and transportation. Water electrolysis powered by renewable electricity, commonly referred to as green H 2 , can be used to generate H 2 with low carbon dioxide emissions. Herein, we analyze the critical mineral and energy demands associated with green H 2 production under three different hypothetical future demand scenarios, ranging from 100–1,000 Mtpa H 2 . For each scenario, we calculate the critical mineral demands required to build water electrolyzers ( i.e. , electrodes and electrolyte) and to build dedicated or additional renewable electricity sources ( i.e. , wind and solar) to power the electrolyzers. Our analysis shows that scaling electrolyzer and renewable energy technologies that use platinum group metals and rare earth elements will likely face supply constraints. Specifically, larger quantities of lanthanum, yttrium, or iridium will be needed to increase electrolyzer capacity and even more neodymium, silicon, zinc, molybdenum, aluminum, and copper will be needed to build dedicated renewable electricity sources. We find that scaling green H 2 production to meet projected net-zero targets will require ∼24,000 TWh of dedicated renewable energy generation, which is roughly the total amount of solar and wind projected to be on the grid in 2050 according to some energy transition models. In summary, critical mineral constraints may hinder the scaling of green H 2 to meet global net-zero emissions targets, motivating the need for the research and development of alternative, low-emission methods of generating H 2 .
Air quality and the concentration of polycyclic aromatic hydrocarbons (PAHs) in urban environments are increasingly becoming a concern. Measuring air quality and PAHs, and linking these to specific activities, requires deploying and recovering sampling devices to capture and measure any changes. From May 2020 to June 2021, during the “lockdown” period of the COVID-19 pandemic, acrocarpous and pleurocarpous mosses were collected from five types of site in Aberdeen, United Kingdom, and the concentration of PAHs measured to track changes in PAHs as travel-related activities changed. The predominant types of PAHs found on mosses were of the four- and five-ring varieties, with the four-ring variety of PAH (medium molecular weight) becoming more dominant as the lockdown was lifted. However, for most sites, the concentration of PAHs was evidently perturbed by the transient lifting, reimposing, and then lifting of lockdown conditions, which either directly limited travel or changed people’s motivations to travel by car. Molecular diagnostic ratios or molecular marker parameters used to infer the source of PAHs varied little and were nearly always consistent with PAHs deriving from combustion in vehicle engines. Thus, even when travel was limited, PAHs were still derived from vehicle usage, although the overall concentrations on mosses were much lower. On average, the lowest PAH concentrations were found on mosses collected from a recreational park located the furthest from traffic. The highest PAH concentrations were observed on mosses collected from residential car parks during periods when the lockdown had been lifted. However, mosses from the same residential car parks had very low PAH concentrations during periods of travel restrictions, strongly suggesting that, for mosses, local factors and patterns of vehicle usage strongly determine their exposure to PAHs. Therefore, mosses within urban environments can be used for monthly monitoring of PAHs as they are able to detect changes induced by human behaviour.
The Mount Meager Volcanic Complex (Q̓welq̓welústen) is an active glacier-capped volcanic massif in the Garibaldi Volcanic Belt (British Columbia) and the only known glaciovolcanic cave system in North America steadily releasing sulfur-rich gases. In September 2022, leveraging specialized cave explorer expertise, the fumarole-carved ice cave at the Job Glacier on Mt. Meager was surveyed. Direct measurements of fumarolic gas concentrations were taken at the source, with H2S >200 ppm, SO2 >100 ppm, CO2 ∼5,200 ppm, and CO ∼230 ppm. Snowpack and fumarole-associated sediments were characterized for microbial diversity, functional potential, and biogeochemistry including measurements of nutrients, major ions, dissolved organic and inorganic carbon concentrations as well as the stable isotope compositions of carbon, sulfur, hydrogen and oxygen. Green algae (Chlorophyta) dominated the snowpack, consistent with other Pacific Northwest glaciers. Representatives of Firmicutes were the most abundant bacterial sequences detected in our samples, contrasting with other glacier and snowpack samples which harbor abundant Sphingobacteria, Betaproteobacteria, and Alphaproteobacteria. Sediments and water collected inside the cave were mostly high in SO42- (5.3–185.2 mg/L) and acidic (pH = 3.6–6.0), while most other major anions and cations were below detection of the method used. Snow at the cave entrance had more SO42- (0.08 mg/L) and lower pH (5.9) than snow collected at a distance (SO42- undetectable, pH 7.6), suggesting influence by fumarole exhalations. Negative δ13C values of organic matter (−29.0‰ to −26.1‰, respectively) in sediments suggest in-situ microbial carbon transformations, findings that are supported by the presence of genes encoding complete heterotrophic and autotrophic carbon transformation pathways. The δ34S value of H2S was ∼0‰, suggesting a deep magmatic origin; however, both sulfur-oxidizing and sulfate-reducing microbial phyla were present in the sediment samples as were genes encoding both dissimilatory sulfur-oxidizing and sulfate-reducing pathways. Metagenomic data suggest diverse chemosynthetic lifestyles in the cave microbial community. This study provides insight on the microbiomes associated with a sulfidic glaciovolcanic system and identifies unique analog features for icy celestial bodies like Saturn’s moon Enceladus, where cryovolcanic activity may carry biomarkers from the subsurface and deposit them on surface ice.
Sphingolipids have long been of interest to the scientific community for their roles in eukaryotic cell structuring and disease pathology. Less is known about the occurrence and function of these diverse compounds in the bacterial domain of life, with most studies on bacterial sphingolipids focused on eukaryotic disease research and host-pathogen or host-symbiont interactions. Thus, bacterial contributions to environmental sphingolipid pools are poorly understood and the function of these lipids outside of pathogenicity remains largely unexplored. This report marks the first instance of sphingolipid production in a member of the phylum Acidobacteria, a globally ubiquitous phylum of soil bacteria. The occurrence of core- and intact-ceramides is reported for the Acidobacterium Solibacter usitatus under various environmentally relevant conditions. Shifts in the production of ceramides across temperature, pH, and oxygen gradients in this organism suggest that these compounds play a role in the physiological adaptation to environmental fluctuations. Additionally, the genetic basis of bacterial ceramide biosynthesis in this species is assessed and used to explore the potential for ceramide biosynthesis across the bacterial domain of life. The extent of the biosynthetic potential for Acidobacteria to produce ceramides coupled to the abundance of their genes in soil metagenomes suggests that soil sphingolipids should not be solely attributed to eukaryotic production.
