Poikilitic hornblende ultramafic rocks, classically called cortlandtites after their first description along the Hudson River in New York, are among the more enigmatic rock types found in orogenic belts. Their defining texture is unmistakable under the microscope: enormous grains of hornblende, a hydrous calcium-magnesium-iron amphibole, that completely enclose smaller, rounded crystals of olivine and pyroxene. The rounded phases represent earlier-formed crystals, while the giant amphibole grew late, wrapping around everything in its path. Such rocks are minor but recurring constituents of granitic and metamorphic terranes, of the deep crustal and upper mantle sections of supra-subduction ophiolites, and even of xenoliths brought up from beneath active volcanic arcs. Because amphibole can hold enormous quantities of water in its crystal structure, these rocks are direct archives of the volatiles that circulate through subduction zones and drive arc magmatism.

The Abukuma occurrence had been described petrographically in earlier decades, but its origin remained unresolved. What makes this locality special is context: the poikilitic hornblende pyroxenite sits in contact with regionally metamorphosed rocks of the Nishidohira unit, and nearby are amphibole-rich gabbros that appear to be genetically related to it. Together they offer a natural laboratory for studying how amphibole-bearing magmas differentiate from the upper mantle down into the lower crust. The research team collected samples well away from the contacts with the surrounding metamorphic rocks and from thin leucocratic veins that cut the body, minimizing any contamination from later fluids, and then subjected the rocks to an exhaustive campaign of X-ray element mapping, electron microprobe analysis, laser ablation trace element measurements, and uranium-lead dating of zircon.

The resulting mineral inventory is strikingly unusual for an ultramafic rock. Olivine makes up roughly five percent of the mode, pyroxenes about fifty percent, and amphibole about forty-five percent, with only trace amounts of biotite, orthopyroxene and ilmenite. Crucially, no plagioclase is present at all, a detail that would prove central to the interpretation. The amphibole grains display vivid color zoning under transmitted light, from dark brown-black cores through brown margins to pale green rims. The dark cores are titanium-rich pargasite containing 1.3 to 2.1 weight percent TiO2, and they are riddled with exsolution lamellae of ilmenite, evidence that the original crystals were even more titanium-rich before decompression forced the iron-titanium oxide out of solution. The green rims and vermicular intergrowths are far poorer in titanium and aluminum, and their chemistry points to crystallization from an evolved, water-rich residual melt or fluid rather than a primitive magma.

The textural relationships tell a sequential story. The rounded olivine grains, with forsterite contents of only 65 to 76 percent, are too iron-rich to represent residual mantle peridotite and instead point to a cumulate origin, crystals settled out of an earlier magma. High-aluminum clinopyroxene and the dark high-titanium pargasite are in chemical equilibrium and crystallized first from the infiltrating melt. Later, as the melt fractionated and released hydrous fluids, low-aluminum vermicular clinopyroxene and low-titanium amphibole replaced the earlier phases, and orthopyroxene formed by reaction of olivine with a silica-rich melt or fluid. The absence of europium and strontium anomalies in the early amphibole and clinopyroxene confirms that no plagioclase had crystallized before the amphibole, consistent with the total lack of plagioclase in the rock.

The analytical centerpiece of the study is the reconstruction of the melt from which the dark amphibole grew. Amphibole incorporates many trace elements in predictable proportions relative to the melt around it, so with experimentally calibrated partition coefficients, the researchers could invert the crystal chemistry to recover the liquid composition. Using empirical thermobarometric equations and the open-source Thermobar package, they estimated a melt containing roughly 59 to 67 weight percent silica, 17 to 18 percent alumina, and 2 to 4 percent magnesium oxide at around 1000 degrees Celsius. The calculated trace element signature shows high light rare earth element to heavy rare earth element ratios, a weak positive strontium anomaly, and pronounced depletions in high-field-strength elements such as niobium, zirconium and titanium. That combination is the fingerprint of an adakite.

Adakites are intermediate to felsic arc rocks, first defined in 1990, characterized by high strontium but low yttrium and heavy rare earth contents, and generally attributed to partial melting of young, hot subducted oceanic basalt under amphibole or eclogite facies conditions. Alternative pathways exist, including melting of thickened lower crust or extensive garnet and amphibole fractionation, but all require unusual pressure and temperature conditions in the sub-arc system. The melt inferred from the Abukuma amphibole matches adakitic compositions from the Japanese arc record almost exactly, and critically, the spatial and temporal context clinches the connection. Adakitic granites and high-magnesium andesites, dated at 128 to 113 million years, are already documented in the nearby Kitakami Mountains to the northeast, where isotopic modeling indicates derivation from partial melting of subducted basaltic crust with a sedimentary contribution.

Zircon crystals recovered from both the poikilitic hornblende pyroxenite and the associated hornblende gabbro yielded concordant uranium-lead ages of 117.5 plus or minus 0.4 and 116.3 plus or minus 0.5 million years respectively, with all grains showing thorium-uranium ratios above 0.1 that confirm a magmatic rather than metamorphic origin. These ages overlap with the Kitakami adakitic pulse and place the formation of the ultramafic body squarely within the Early Cretaceous. The Irishiken granodiorite that intrudes the region nearby, dated in this study at 105.9 plus or minus 0.6 million years, is younger and marks a later thermal event that previous work has linked to the rapid exhumation of the Nishidohira metamorphic rocks. Thermobarometry on the reconstructed dark amphibole composition, corrected for ilmenite exsolution, gives pressures of 0.4 to 0.7 gigapascals and temperatures of 870 to 940 degrees Celsius, conditions consistent with the amphibole stability field in a magnesian andesitic melt and with the partial resorption of olivine that its rounded shapes record.

The relationship between the two rock types at the locality resolves a broader petrological question. Experiments show that when hydrous basaltic melt reacts with peridotite, hornblende-rich ultramafic rocks form where the melt is scarce and reaction dominates, whereas hornblende gabbro crystallizes where melt is abundant. The Abukuma pair fits this model precisely: at low melt-to-rock ratios, adakitic liquid invading pre-existing ultramafic rock converted it to poikilitic hornblende pyroxenite, buffered to high magnesium numbers by the host; at high melt-to-rock ratios, the same liquid pooled and crystallized as hornblende gabbro, with early amphibole, titanite and apatite sequestering calcium and trace elements before plagioclase finally appeared. Similar relationships between dunitic xenoliths and adakite-related microgabbro in the Kitakami Mountains show the process operating on a regional scale.

Taken together, the evidence portrays the southern Abukuma Mountains as a preserved slice of a plumbing system that tapped slab-derived melts during an extraordinary episode of Early Cretaceous subduction. At that time, the eastern margin of the Eurasian Plate was consuming the Izanagi, or Kula, oceanic plate, and the widespread adakitic magmatism across both the Kitakami and Abukuma regions implies that a young, hot segment of that plate was melting as it descended. The poikilitic hornblende pyroxenite, with its giant amphibole crystals acting as chemical sponges for water and incompatible elements, is thus not a geological curiosity but a key witness to how slab melts transform the deep crust and mantle beneath volcanic arcs. For anyone seeking to understand how continents are built from the inside out, this modest Japanese outcrop now offers one of the clearest windows available into that hidden, melt-rock conversation.

Subject of Research: Petrogenesis of poikilitic hornblende pyroxenite formed by adakitic melt–ultramafic rock interaction in the Early Cretaceous Abukuma Mountains, Japan

Article Title: Poikilitic hornblende pyroxenite in the southern end of the Abukuma Mountains, Northeast Japan, as result of adakitic magmatism

Article References: Wakazono, A., Fukuyama, M., Itano, K., Harigane, Y., Tamura, A., & Morishita, T. (2025). Poikilitic hornblende pyroxenite in the southern end of the Abukuma Mountains, Northeast Japan, as result of adakitic magmatism. Frontiers in Geochemistry, 3, Article 1697337. https://doi.org/10.3389/fgeoc.2025.1697337

Image Credits: AI Generated

DOI: 10.3389/fgeoc.2025.1697337

Keywords: poikilitic hornblende pyroxenite, adakite, Abukuma Mountains, amphibole, U-Pb zircon dating, Early Cretaceous, subduction zone, Izanagi plate, ultramafic rocks, melt-rock interaction, Japan, arc magmatism

The research, led by Raghda Emera and colleagues at the Harold Vance Department of Petroleum Engineering, focuses on serpentinization, the hydrothermal alteration of ultramafic rocks such as peridotite and dunite. When olivine, the dominant mineral in these rocks, reacts with water at elevated temperatures, ferrous iron is oxidized to ferric iron, and molecular hydrogen is released as a byproduct. The process has long been documented at mid-ocean ridge hydrothermal fields such as Lost City and Rainbow, but translating that natural phenomenon into a predictable, engineered energy resource has remained stubbornly difficult.

One of the study’s clearest messages concerns the identity of the reacting mineral itself. Olivine is a solid solution between a magnesium-rich end member, forsterite, and an iron-rich end member, fayalite. Prior thermodynamic work suggested that iron-rich olivine generates two to ten times more hydrogen per mole than magnesium-rich varieties, but direct experimental isolation of this effect had been lacking. The Texas A&M group ran controlled experiments on pure fayalite, pure forsterite, and an equal mixture of the two under identical conditions of 100 degrees Celsius, 33 bar, and near-neutral pH, removing all confounding variables.

The results were striking. Pure fayalite produced the highest hydrogen yields of any powdered sample, roughly five times more than a natural peridotite and more than double the yield of the 50-50 mixture. Pure forsterite, by contrast, generated no detectable hydrogen at the experimental temperature. The team’s calibrated kinetic models, which combine thermodynamic equilibrium calculations with Arrhenius-type rate laws, matched the laboratory data closely, with a maximum relative error of just 0.14. When the model was pushed to hypothetical compositions, a rock containing 61.5 percent fayalite produced nearly three times the hydrogen of a natural peridotite with 21 percent fayalite, confirming that iron availability is the single strongest lever on hydrogen generation.

Temperature ranked second in importance. Sensitivity simulations showed that raising temperature from 50 to 100 degrees Celsius increased simulated hydrogen generation roughly fourfold for pure fayalite, with smaller gains for mixed compositions. In the core-scale model, doubling the temperature from 100 to 200 degrees Celsius nearly doubled the peak hydrogen concentration, shifting the peak to around day three instead of days seven to nine. This steep dependence follows classic Arrhenius kinetics, in which the rate-limiting olivine dissolution step carries an activation energy of 60 to 80 kilojoules per mole, enough to produce a tenfold rate increase for roughly every 40 degrees Celsius of warming.

The pressure and pH results were more nuanced, and in some cases counterintuitive. Laboratory batch experiments appeared to show less hydrogen in the gas phase at higher pressures, but the authors traced this to an experimental artifact: pressurizing the reactor with nitrogen diluted the headspace and pushed more hydrogen into the dissolved phase. Back-calculations accounting for the nitrogen inventory still indicated a genuine decline in yield at the highest pressures in the batch tests, while the kinetic models, which free the chemistry from those artifacts, showed a modest positive effect of pressure. The team emphasizes that pressure is a secondary control compared to mineralogy and temperature.

pH effects turned out to depend on pressure, a coupling that single-variable experiments often miss. At 35 bar, the moderately alkaline pH of 8.5 consistently outperformed pH 9.5, reaching 431 ppm hydrogen at 28 days versus just 59 ppm. At 70 bar, the ranking flipped early in the experiment before converging, and pH 10.5 performed worst throughout. The authors suggest that higher alkalinity suppresses hydrogen generation under these conditions, likely by limiting mineral dissolution or promoting passivating coatings of secondary minerals on reactive surfaces.

Perhaps the most consequential finding involves scale. The team compared the powdered batch experiments with a flow-through experiment on a fractured core of Twin Sisters dunite, a nearly pure olivine rock from Washington State containing 92.3 percent olivine. The core was split, propped open with a roughly one-millimeter fracture, and flooded with synthetic brine at 100 degrees Celsius while effluent gas was analyzed continuously by micro gas chromatography. Hydrogen rose to a peak near day seven and then declined, mirroring the model closely during the first eight days but diverging sharply afterward, with relative errors eventually exceeding 700 percent.

That divergence is scientifically revealing rather than a failure. In powdered systems with abundant, uniform mineral-fluid contact, reaction kinetics control the outcome. In fractured intact rock, transport takes over: serpentinization products such as chrysotile and magnetite precipitate on reactive surfaces, the roughly 40 to 44 percent solid volume expansion of serpentinization can occlude fracture apertures, and flow may channel away from unreacted mineral. The authors identify evolving reactive surface area, permeability feedback, and geomechanical deformation as the highest-priority additions to future models before laboratory numbers can be trusted at reservoir scale.

For the nascent geological hydrogen sector, the practical takeaway is concrete: exploration and stimulation programs should prioritize screening formations for fayalite, or iron-rich olivine content, as the dominant predictor of hydrogen yield, while remembering that the kinetically accessible maxima implied by powdered experiments require open, stimulated flow conditions to approach underground. The study, published in Frontiers in Geochemistry and partly funded by the U.S. Department of Energy’s ARPA-E program, provides a controlled dataset and a validated modeling framework that together mark a significant step toward making Earth’s own hydrogen factory predictable.

Subject of Research: Hydrogen generation from water-rock reactions in ultramafic rocks

Article Title: Experiments and geochemical modeling of hydrogen generation during water–rock reactions: effects of mineralogy and physicochemical conditions

Article References: Emera, R., Angelina, N. M., Gyaubea Matey-Korley, V., Isah, A., & Okoroafor, E. R. (2026). Experiments and geochemical modeling of hydrogen generation during water–rock reactions: effects of mineralogy and physicochemical conditions. Frontiers in Geochemistry, 4, Article 1913188. https://doi.org/10.3389/fgeoc.2026.1913188

Image Credits: AI Generated

DOI: 10.3389/fgeoc.2026.1913188

Keywords: geological hydrogen, serpentinization, olivine, fayalite, forsterite, ultramafic rocks, geochemical modeling, reactive transport, Arrhenius kinetics, mineralogy, hydrothermal reactions, pH

Olivine, a magnesium- and iron-rich silicate mineral abundant in ultramafic rocks, has long been celebrated as a candidate for CO2 mineralization. When CO2 dissolved in water encounters olivine, a chain of chemical reactions converts the carbon into carbonate minerals such as magnesite, effectively turning a greenhouse gas into stone. This process, known as mineral carbonation, is attractive because the captured carbon is stored permanently, with no risk of leakage back into the atmosphere over human timescales. Yet the practical challenge has always been speed. Natural weathering of olivine at Earth’s surface takes thousands to millions of years, and even under engineered conditions the reaction rates can vary dramatically depending on the composition of the mineral and the chemistry of the surrounding fluids.

One puzzling observation has stood out in the literature: calcium-bearing olivines, such as the mineral kirschsteinite, appear to react with carbon dioxide far more readily than their magnesium-bearing counterparts, such as the common mineral forsterite. The origin of this striking difference in reactivity has remained poorly understood, and the new study set out to resolve it. Rather than treating the cation itself as the sole actor, the researchers built a multiscale theoretical framework that connects the electronic structure of the mineral surface to the macroscopic dissolution rates that can be measured in the laboratory.

At the heart of the framework is a seemingly humble chemical species: the nonbridging oxygen. In silicate minerals, oxygen atoms either bridge two silicon tetrahedra or dangle from a single silicon atom, the latter being known as nonbridging oxygens. These dangling oxygens are chemically more reactive, and the new work identifies them as the critical oxygen source for the surface reactions that initiate CO2 mineralization. When a CO2 molecule approaches the olivine surface, it is these nonbridging oxygens that participate directly in forming carbonate species, setting the stage for the dissolution of the metal cations and the eventual precipitation of solid carbonate.

The calculations, grounded in density functional theory, revealed that the type of cation modulates the reactivity of these surface oxygens in profound ways. In calcium-bearing olivine, the presence of Ca2+ alters the local electronic environment such that the energy barrier for calcium dissolution is reduced by 60 percent compared with the magnesium analogue. That seemingly modest energetic change has enormous kinetic consequences: the rate of ion release accelerates by six orders of magnitude, a millionfold increase. In chemical kinetics, a millionfold rate difference is the difference between a reaction that finishes in an afternoon and one that grinds on for centuries.

To test whether these atomic-scale predictions hold up at the laboratory scale, the team compared their calculated apparent dissolution rate constants with experimental observations. The agreement was remarkable. The computed rates reproduced the experimentally observed complete conversion of calcium olivine within hours under a carbon dioxide pressure of just one atmosphere, conditions that are mild by the standards of industrial carbonation processes. This cross-scale consistency, from quantum mechanical calculations of bond breaking to bulk conversion measurements in a reactor, provides strong evidence that surface carbonation reactions, rather than bulk transport or precipitation, are the governing bottleneck in olivine carbonation.

The implications of this mechanistic insight extend well beyond explaining a laboratory curiosity. For engineers designing CO2 mineralization systems, the framework offers a predictive basis for selecting and tailoring materials. If the reactivity of a silicate surface can be tuned by controlling the density and environment of nonbridging oxygens, then synthetic materials could be engineered to maximize the availability of these reactive sites, dramatically accelerating carbonation rates without resorting to extreme temperatures or pressures. The same logic applies to natural reservoirs: basaltic and ultramafic formations, which host vast quantities of reactive divalent cations, could be evaluated and ranked according to their surface chemistry rather than merely their bulk composition.

The study also carries a conceptual lesson for geochemistry more broadly. Dissolution rates of silicate minerals have traditionally been parameterized by empirical rate laws that depend on pH, temperature, and solution composition, but the atomic origins of those dependencies have often remained obscure. By demonstrating that cation identity acts on dissolution kinetics through its modulation of oxygen reactivity, the work provides a bridge between electronic structure theory and the macroscopic rate laws used in reactive transport models. Such bridges are essential if models of subsurface carbon storage are to move from descriptive to predictive, allowing operators to forecast how quickly injected CO2 will mineralize in a given formation and to design injection strategies accordingly.

For the global climate effort, the stakes are considerable. Ultramafic rocks are a global resource with vast potential for permanent CO2 mineralization, and basaltic reservoirs such as those already being used for pilot carbon storage projects in Iceland and the Columbia River Basalt Group in the United States have demonstrated that injected CO2 can mineralize within years rather than millennia. Understanding at the atomic level why certain minerals convert so much faster than others gives scientists a lever to pull: the possibility of accelerating the process further, whether through fluid chemistry manipulation, thermal treatment, or the design of engineered reactive materials that mimic the fast-reacting calcium olivines identified in this study.

The research, funded by the Japan Society for the Promotion of Science through KAKENHI grants and by ENEOS Xplora Inc., represents a convergence of quantum chemistry, geochemistry, and reaction engineering aimed squarely at one of the hardest problems in decarbonization: what to do with the CO2 once it is captured. By showing that the answer to rapid mineralization lies in the fine-grained choreography of oxygen atoms at a mineral surface, the Tokyo team has turned a long-standing puzzle into a design principle. As carbon capture and storage infrastructure scales up worldwide, the ability to predict and engineer mineral reactivity from first principles may prove to be one of the quiet but decisive advances that turns permanent geological carbon storage from a promising idea into a dependable industrial reality.

Subject of Research: Atomic-scale mechanisms of olivine surface carbonation and CO2 mineralization kinetics

Article Title: Surface carbonation governs olivine reactivity for rapid CO2 mineralization

Article References: Surface carbonation governs olivine reactivity for rapid CO2 mineralization. (n.d.). https://doi.org/10.1038/s41467-026-78548-z

Image Credits: AI Generated

DOI: 10.1038/s41467-026-78548-z

Keywords: CO2 mineralization, olivine, carbon capture and storage, geochemistry, density functional theory, nonbridging oxygens, dissolution kinetics, ultramafic rocks, carbonate minerals, basalt reservoirs, reaction mechanisms, climate mitigation

Chromium is a metal of two faces. In its trivalent form, Cr(III), it is a trace nutrient that humans actually require for glucose metabolism, and it tends to bind tightly to soils and sediments, staying put in the environment. In its hexavalent form, Cr(VI), it is something altogether more sinister: a mobile, highly soluble oxidized anion that is classified as a human carcinogen when inhaled and is associated with serious toxic effects when ingested. The difference between these two species is a matter of a few electrons, but that small electrochemical gap separates an essential nutrient from a poison. Yet most environmental monitoring programs around the world still report only total chromium, a single number that lumps the benign and the hazardous together as if they were the same substance.

The research team, led by Banu Kutlu together with Tarık Baydar, Vesile Yıldırım and Zekeriya Konurhan, set out to test whether species-specific measurements provide genuinely additional information beyond that operational total. Their study area is geologically primed for chromium chemistry. The region sits within the Tunceli Ophiolite, a slab of depleted mantle peridotite hosting chromitite deposits, the kind of ultramafic rock that contains abundant chromium-bearing minerals such as chromite. When these rocks weather naturally, chromium can be released into water, and under the right geochemical conditions, manganese oxides and other oxidants can convert the relatively harmless Cr(III) into the hazardous Cr(VI). This means that in ultramafic terrain, hexavalent chromium is not exclusively an industrial artifact; it can be geogenic, produced by the slow chemistry of rock and water long before any mine arrived.

To disentangle these influences, the researchers collected surface-water samples across the watershed for a full year and measured Cr(III) and Cr(VI) separately using species-specific UV–Visible spectrophotometric methods. The operational total chromium was then defined as the sum of the two separately measured species, a calculated value rather than an independently measured total. The results spanned an enormous range: from below the detection limit up to 578.13 micrograms per liter. For context, the World Health Organization guideline for total chromium in drinking water is 50 micrograms per liter, and the calculated total exceeded that screening benchmark at 14 of the 28 stations. That figure alone is striking, but the species-level data told a far more nuanced story.

Cr(III) predominated throughout most of the watershed, consistent with the reducing, mineral-rich conditions that favor the trivalent form. The highest Cr(VI) concentration occurred at a single localized hotspot, a concentrated pocket of the oxidized species rather than a watershed-wide plume. Yet here lies the study’s central warning: when the team screened the data against Cr(VI)-specific thresholds under an assumed scenario of untreated drinking-water ingestion, multiple stations exceeded those screening levels. In other words, a watershed could pass a total chromium test at some locations while still harboring concentrations of the carcinogenic species that warrant attention. Operational total chromium, the study concludes, did not consistently identify the spatial distribution of Cr(VI)-related potential risk.

The health-risk dimension of the work adds another layer of urgency. Using both deterministic calculations and an empirical bootstrap approach, a probabilistic method that resamples the data thousands of times to capture uncertainty, the team estimated screening-level hazard quotients for adults and children consuming the water untreated. The estimates were consistently higher for children than for adults, a familiar pattern in risk assessment that reflects children’s higher water intake relative to body weight and their greater susceptibility to early-life exposures, a principle the U.S. Environmental Protection Agency has formalized in its guidance on early-life susceptibility to carcinogens. Importantly, the researchers are careful about what their numbers do and do not show: direct untreated consumption of the sampled surface waters was not verified, so the results are screening-level indications of potential risk rather than confirmed exposures.

The mineralogical arm of the investigation brought the rocks themselves into the courtroom. Using X-ray diffraction to identify crystalline phases, scanning electron microscopy with energy-dispersive spectroscopy to examine mineral chemistry at microscopic scales, and Fourier-transform infrared spectroscopy to probe molecular structures, the team characterized the solid phases that control chromium’s fate. These techniques matter because chromium mobility in water is governed by which minerals are dissolving, which surfaces are adsorbing the metal, and which oxidants such as iron-manganese nodules are available to catalyze the conversion of Cr(III) to Cr(VI). Multivariate statistical analyses of the hydrochemical data were then used to trace the fingerprints of different water sources and processes across the watershed.

One of the study’s most honest findings is what it could not determine. Mining-influenced stations generally exhibited higher chromium concentrations than their counterparts elsewhere in the watershed, suggesting that mining activity does contribute to mobilization. But the relative contributions of natural geogenic weathering and mining-related mobilization could not be quantitatively apportioned. This is a genuinely difficult problem in ultramafic terrain, where the ore being mined and the bedrock being weathered are chemically similar, and it underscores why isotopic tracing and other advanced source-apportionment tools remain critical for future work in such settings.

The broader implications reach far beyond eastern Türkiye. Ophiolite belts and ultramafic landscapes ring the Mediterranean, the Balkans, the Middle East and beyond, and natural hexavalent chromium in groundwater interacting with such rocks has been documented from Greece to California. In chromite mining regions, communities often depend on local water supplies, and reviews of drinking-water quality in mining areas have repeatedly flagged heavy-metal contamination as a public health concern. If monitoring programs in these regions rely on total chromium alone, they may systematically miss the spatial pattern of the species that matters most for human health, or conversely, they may raise alarms over stations where the chromium is almost entirely the benign trivalent form.

The message of this study is ultimately a call for smarter measurement. Chromium speciation, the researchers conclude, provided additional environmentally and toxicologically relevant information beyond operational total chromium for evaluating chromium mobility and screening-level potential human health risks in this ultramafic watershed. As analytical methods for species-specific determination become more accessible and validated, the case for building speciation into routine monitoring grows stronger. For the communities living along the rivers of the Pülümür and Ovacık regions, and for millions of others downstream of the world’s ultramafic and mining landscapes, the difference between counting all chromium and counting the right chromium could one day prove decisive for public health.

Subject of Research: Chromium speciation and human health risks in surface waters of an ultramafic mining watershed

Article Title: Hydrogeochemical controls on chromium speciation and potential human health risks in surface waters of an ultramafic mining watershed

Article References: Kutlu, B., Baydar, T., Yıldırım, V., & Konurhan, Z. (2026). Hydrogeochemical controls on chromium speciation and potential human health risks in surface waters of an ultramafic mining watershed. Environmental Geochemistry and Health, 48(14), Article 562. https://doi.org/10.1007/s10653-026-03456-6

Image Credits: AI Generated

DOI: 10.1007/s10653-026-03456-6

Keywords: chromium speciation, Cr(VI), Cr(III), ultramafic rocks, mining watershed, surface water, heavy metal contamination, human health risk assessment, drinking water quality, geogenic chromium, Eastern Anatolia, Environmental Geochemistry and Health