ACS Earth and Space Chemistry最新文献

The Arctic is rapidly warming, and aerosols play an increasingly important role by scattering and absorbing sunlight and by participating in cloud formation. Their optical and cloud-forming properties depend on the mixing state and chemical composition, but observations of these features remain limited. This study comprehensively characterizes 25,254 individual particles collected at Ny-Ålesund, Svalbard (November −December 2020), using microspectroscopy techniques to investigate their size, morphology, mixing state, and chemical composition. Fresh sea salt aerosols (SSA) were identified as the most abundant (∼85%), of the total observed aerosol population, with potential sources from sea spray and blowing snow. Air masses originating from the Arctic Ocean surrounding Svalbard likely contribute to increased concentrations of sub-micrometer “Fresh SSA” particles. “Aged SSA” particles (7.4%) are enriched in sulfur and nitrogen, compared to “Fresh SSA”. These elevated ratios may result from various atmospheric aging processes including the uptake of sulfuric and nitric acids. Our results suggest that aged SSA, with sizes larger than 300 nm, likely underwent chlorine depletion by sulfuric and nitric acids during transport. Additionally, elemental analysis reveals that both fresh and aged SSA can mix with dust particles, regardless of the SSA size (49.9% in sub-micrometer size and 50.1% in super-micrometer size, respectively). Dust particles are efficient ice-nucleating particles (INPs), and SSA is known to act as cloud condensation nuclei (CCN), and therefore, their mixtures may inherit both properties. The non-negligible number (4.4%) of SSA-dust mixtures underscores the importance of these particles as potential sources of CCN and INP in the Arctic atmosphere.

The infrared band strengths of D₂O and H₂O ices have been calculated from new spectra at 10, 70, and 155 K. In contrast to nearly all previous work, integration ranges are provided and close attention has been paid to the use of multiple ice samples and Beer’s Law (Beer–Lambert) plots to support the claim of a linear trend of band intensity with ice thickness. Optical constants have been calculated as averages from the results of multiple measurements, in what again seems to be the first such approach for water ices. A 200% discrepancy in H₂O optical constants in the literature is addressed and a resolution suggested. The new infrared intensity results for D₂O-ice are the first in many years and are compared to previous work from almost a half-century ago. The same new results are used to estimate the intensity of the O–D stretching mode of HDO in ices at 10 K, without the need for warming to higher temperatures. The new estimate can be used for calculating HDO abundances from ice observations made with the James Webb Space Telescope.

The Tatun Volcano Group (TVG) in northern Taiwan, situated at the junction of the Philippine Sea and Eurasian plates, hosts an active hydrothermal system with significant implications for volcanic hazard and geothermal resource management. From January 2016 through October 2022, we conducted monthly monitoring of major dissolved ions, dissolved gases (CO₂, H₂S, SO₂), and helium isotope ratios at the Da-you-keng (DYK) and Geng-zi-ping fumarolic fields. In addition, in 2019 and 2024 we sampled bubbling gases from 13 hot springs and ten groundwater wells across the TVG and adjacent regions, analyzing multispecies gas compositions and stable isotopes (³He/⁴He, δ¹³C, δ¹⁵N). High-density seismic data recorded 4550 microseismic events in 2020, nearly double the long-term average, enabling correlation of geochemical fluctuations with seismic unrest. We observed pronounced periodic variations in dissolved Cl^–, SO₄^2– and cations at the DYK, and complementary patterns of CO₂ and H₂S at both sites, reflecting episodic fluid recharge and redox shifts in the hydrothermal conduit system. Helium isotope ratios (corrected R/R_A = 5.64–7.24) and CO₂/³He−δ¹³C trends delineate mixing between mantle-derived and crustal sources, while N₂–He–Ar systematics reveal sediment contributions modulated by major faults. Spatially, elevated ³He/⁴He ratios are clustered around the DYK, with values decreasing along fault-controlled pathways, indicating focused deep degassing. Periods of heightened seismicity coincide with gas-ratio anomalies (CO₂/H₂S and ³He/⁴He) and surges in magmatic helium, suggesting ascending deep fluids contribute to both degassing and earthquake generation. The integrated geochemical–seismic analysis underscores ongoing volcanic activity in the TVG and provides a framework for enhancing eruption forecasting and guiding sustainable geothermal exploitation.

Continental outflows from Southeast and East Asia significantly influence aerosol distribution over southern peninsular India during the winter period, when northeast air mass dominates over the region, impacting sensitive ecosystems that regulate regional climate and rainfall patterns. To study the composition of atmospheric aerosols and document signatures of anthropogenic influence over background atmospheric environments, PM₁₀ and PM_2.5 aerosol samples were collected from the High-Altitude Cloud Physics Observatory (HACPO; 1820 m above MSL) located at Munnar, a hill-station situated on the windward side of the southern Western Ghats. The collected samples were subjected to offline chemical analyses to estimate the different components of aerosols including water-soluble inorganic ions, water-soluble organic carbon (OC) (WSOC), OC, elemental carbon (EC), and light absorption characteristics of water-soluble brown carbon (WS-BrC) as well as morphology and elemental characterization. Results show that NH₄⁺, SO₄^2–, NO₃^–, K⁺, and EC, predominantly from anthropogenic sources, contributed to 45% of PM₁₀ mass loading, with WS-BrC chromophores at 365 nm exhibiting increased abundance and enhanced absorbing capacity in winter, confirming the presence of pollutants influenced from northeastern continental transport. The PMF-identified sources showed distinct seasonal variability, with dust and secondary biogenic aerosols dominant in premonsoon and secondary inorganic aerosols and combustion-related sources prevailing in winter. The resolved source profiles exhibited strong similarity with previous regional studies, highlighting a consistent spatial pattern of long-range transported aged anthropogenic emissions across southern-peninsular India during the winter period, under the influence of northeast air-mass. Analysis of the surface morphology and elemental characterization of individual particles reveals that the particles exist in a mixed state, originating from both anthropogenic and natural sources, comprising carbonaceous components, mineral dust, and secondary-formed sulfate and nitrate. The findings from this study underscore the significant presence of anthropogenic aerosols over the pristine region of Western Ghats, comparable to that observed over other regions in peninsular India during the continental outflow period. Understanding the characteristics of these transported aerosols in this tropical hill station, which experiences relatively pristine atmospheric background conditions, can provide valuable insights into their impact on hygroscopic growth and cloud condensation nuclei activity within the existing aerosol system.

The Lanmuchang deposit in Guizhou, China, represents a unique Carlin-type system characterized by the concurrent enrichment of gold (Au), mercury (Hg), and thallium (Tl). This study integrated mineralogical and geochemical analyses to reveal the alteration processes, ore-forming conditions, and metallogenic mechanisms of the deposit. The results demonstrate that the ore-related alterations in the Lanmuchang deposit were dominated by silicification, decarbonation, argillization, and sulfidation. Gold mineralization occurred under low-temperature (200–230 °C), weakly acidic pH (∼4), and reducing conditions (log fs₂ = –11.4, log fo₂ = –35.3––39.5). Gold-bearing pyrite formation was jointly controlled by silicification, decarbonation, and sulfidation processes. Mercury mineralization occurred at 126–195 °C, weakly acidic to near-neutral pH (4.4–7.8), and variable fugacity (log fs₂ = –15.1––5.6, log fo₂ = –45––28.9). Cinnabar, as the primary Hg-bearing mineral, was likely precipitated during cooling and oxidation of hydrothermal fluid. Thallium mineralization occurred at lower temperatures (113–137 °C), neutral-alkaline pH (6.9–9.1), and lower fugacity conditions (log fs₂ = –18.8––15.1, log fo₂ <–42.2). Argillization processes (including kaolinization and illitization) potentially facilitated the mobilization of Tl, which was subsequently enriched in lorandite and pyrite under a weakly alkaline and reducing environment. The systematic variations in alteration styles and ore-forming conditions of Au, Hg, and Tl mineralization are interpreted as the key controlling factors for their spatial association and separation patterns, providing new insights into multimetal enrichment in Carlin-type deposits.

Autonomous Raman instruments deployed on Mars rovers, deep-sea landers, and mobile field robots must interpret raw spectra that are distorted by fluorescence baselines, peak shifts, and limited ground-truth labels. Using rigorously documented subsets of the RRUFF mineral database, we systematically evaluate one-dimensional convolutional neural networks (CNNs) and report four practical advances: (i) Reproducible, baseline-independent classification: Compact end-to-end CNNs surpass k-nearest-neighbors and support-vector classifiers built on handcrafted peak features, eliminating background-correction and peak-picking stages. Unlike earlier work, we isolate the contribution of learned features and ensure full reproducibility by releasing all data splits and preprocessing scripts. (ii) Pooling controlled robustness: By adjusting a single pooling parameter, CNNs accommodate Raman shift displacements up to 30 cm^–1, enabling a practical trade-off between translational invariance and class resolution, aligned with instrument stability and spectral variability. (iii) Label-efficient learning: Semisupervised generative adversarial networks and contrastive pretraining improve classification accuracy by up to 11% when only 10% of labels are available. While smaller than gains in vision tasks–due to Raman spectra’s lower complexity–these methods remain valuable for autonomous deployments with limited annotation. (iv) Constant time adaptation: Freezing the CNNs backbone and retraining only the softmax layer transfers the model to unseen minerals at $O\left(1\right)$ inference cost, outperforming Siamese networks on resource-limited robotic processors. The resulting workflow–train directly on raw spectra, tune pooling to instrument tolerance, add semisupervision when labels are scarce, and fine-tune lightly for new targets–offers a practical path toward robust, low-footprint Raman classification in autonomous field settings.

The source of volcanism in the Cameroon volcanic line remains unresolved. To better constrain the mantle components involved, we measure light noble gas (He–Ne–Ar) isotopes and, for the first time, heavy noble gas (Kr–Xe) isotopes in mantle-derived gases from São Tomé, using high-precision dynamic mass spectrometry (DMS). Our data show that the source of São Tomé volcanism is a plume-like mantle reservoir, which is enriched in ²²Ne relative to nucleogenic ²¹Ne when compared to samples originating from the convecting upper mantle, as represented by Mid-Ocean Ridge Basalts (MORBs). In contrast, the isotopic compositions of helium and xenon appear similar to those of the MORB mantle. DMS analysis of Xe isotopes reveals that volcanic gases are affected by diffusive transport fractionation in the subsurface, causing small enrichment in the light isotopes (e.g., ¹²⁸Xe). After correction for this secondary fractionation, we observe a slight, yet discernible, ¹³⁶Xe excess relative to the MORB mantle, attributable to spontaneous fission of ²³⁸U. We hypothesize that this excess fissiogenic Xe may arise from the ²³⁸U associated with recycled crustal component(s) in the São Tomé mantle source, potentially related to the influence of the HIMU-type mantle. The consistent ¹²⁹Xe/¹³⁶Xe (relative to air) observed in both MORB and plume-influenced mantle components is difficult to reconcile with the commonly accepted view that ¹³⁶Xe excesses originate from two distinct sources─²³⁸U and ²⁴⁴Pu fission, respectively─in these separate mantle reservoirs. Further investigation is needed to determine whether the apparent homogeneity in ¹²⁹Xe/¹³⁶Xe excess across the mantle, which contrasts with the distinct sources and evolutionary histories of other volatile elements (e.g., He, Ne, and N₂), is coincidental or indicative of an underlying process.

Nanospectroscopic investigations of the mineralogical composition of materials returned via sample-return missions are crucial for our understanding of the origin and evolution of planetary objects in our Solar System. Here, we show that the emerging technique of photothermal polarimetric nanoscopy, a variant of atomic force microscopy-based infrared spectroscopy, enables one to derive infrared fingerprint spectra of minerals noninvasively on the nanoscale. Besides the spatially resolved identification of specific minerals and mineral phases, the evaluation of the polarization dependence of the photoinduced nanomechanical response, in combination with optical reference data, may allow the deduction of valuable structural information on individual nanocrystallites or grains embedded in solid matrices.

The ¹⁸²Hf–¹⁸²W system is a powerful isotopic tracer for exploring the early evolution of the Earth and other celestial bodies. However, high-precision ¹⁸²W/¹⁸⁴W ratio measurements remain challenging due to low W abundances and subtle isotopic variations in terrestrial samples. Here, an optimized digestion method and refined chemical separation protocols for silicate samples were developed, achieving a total W recovery of ∼90% for mafic rocks with an improved processing efficiency. Subsequently, a Nu Sapphire multicollector inductively coupled plasma mass spectrometer (MC–ICP–MS) was first successfully employed to analyze ¹⁸²W/¹⁸⁴W ratios. This method was optimized for samples with low W abundances of 25 ng g^–1, yet achieved intermediate measurement precision comparable to previous studies that typically analyzed samples with 50 ng g^–1 W. Our results demonstrate that the Alfa Aesar W standard solution, geological standards JB-3 and BHVO-2, as well as two tonalite–trondhjemite–granodiorite samples yield consistent μ¹⁸²W values with published values within uncertainty. The results support the capability of our method to detect subtle deviations in W isotopic ratios in terrestrial samples. Additionally, μ¹⁸²W values for a suite of geological standards, ranging from felsic to mafic compositions, were first reported. These newly reported data expand the global geochemical database and provide valuable references for future studies of tungsten isotope studies.

Electrical conductivity measurements of subsurface geochemical systems are used to detect the presence of aqueous fluids that drive chemical reactions in the Earth’s crust and mantle. Experiments on NaCl solutions show that their electrical conductivities (σ) have a non-monotonic dependence on pressure and temperature. In this paper, we study this important property based on an atomic-scale simulation approach. We perform molecular dynamics (MD) simulations of 1.05 mol/kg NaCl solutions along 473 K, 673 and 1073 K isotherms at pressures from 0.1 to 5 GPa. Two different interaction models are used for our MD simulations: ReaxFF, a many-body dissociative force field, and SPC/E, a two-body rigid force field. The simulations suggest that the non-monotonic behavior of the electrical conductivity is caused by a complex interplay between ion self-diffusion and ion pairing. Both models differ in their predictions. Electrical conductivity in the ReaxFF simulations is influenced by both ion self-diffusion and ion pairing at all the studied conditions, whereas the conductivity from the SPC/E model is completely diffusion-driven at low temperatures, with ion pairing effects observed at higher temperatures. We find that the absolute values of σ obtained from MD simulations are largely consistent with the experimental data up to about 1 GPa, but the surprisingly large increase of σ with temperature at higher pressures reported recently could not be reproduced.