ACS Earth and Space Chemistry最新文献

The limited nutrient availability, extreme temperatures, and desiccation of Arctic volcanic regions provide a unique opportunity to study environments with multiple similarities to extraterrestrial systems. Dyngjusandur, Iceland, is a plain of nutrient-poor volcanic basaltic tephra shaped by alluvial and aeolian action, sharing spectroscopic similarities to analogous geological features observed on Mars. To obtain spatial information at different scales, two regions of the Dyngjusandur plain separated by 1 km and selected for their homogeneous appearance were sampled in this study. Sampling schemes each consisted of nested triangular grids of samples beginning at the 0.1 m scale and increasing to the 100 m scale. Additional samples were recovered in 1 cm increments to a depth of 7 cm. Biological and geophysical analyses were performed including 16S rRNA gene qPCR, DNA quantification, amplicon sequencing, moisture quantification, and separation of grain size fractions. The two sampling sites were found to have significantly different dsDNA content by the t-test (p-value = 0.001) and the Mann–Whitney u-test (p-value = 0.003). The DNA content (a proxy for biomass) showed the greatest variation at 10 m of sample separation, and both total dsDNA content and bacterial 16S rRNA gene copies showed significant correlations with sample grain size. Grain size distribution also appeared to influence the abundance of several bacterial phyla, with positive and negative correlations observed, though the same dominant phyla were observed across all samples studied. This work suggests that, in seemingly homogeneous environments undergoing aeolian resurfacing, the averages from a sample set collected at small spatial separation (1–10 m) may be sufficient to define baseline levels of biomass present and the abundances of the most prominent phyla on a larger (100 m–1 km) scale. However, sampling a larger site at smaller intervals (10 m) provides important characterization of site heterogeneity with diminishing information returns at increasingly smaller intervals (≤1 m).

Organic atmospheric aerosol particles are regularly oxidized, modifying their physical, chemical, and optical properties and affecting the radiative balance of the planet. The organic compound squalene is commonly found in organic particulate matter and regularly undergoes aging by atmospheric oxidants. Here, broadband light Mie spectroscopy is used to monitor the radius and refractive index dispersion of optically trapped squalene aerosol particles over near-ultraviolet to visible wavelengths of 0.320–0.480 μm, throughout atmospheric oxidation by ozone. Extension of broadband light Mie spectroscopy measurements to wavelengths <0.350 μm permits additional insights into the wavelength dependence of the refractive index. Exposure of a squalene particle (≈1 μm radius) to gaseous ozone (5, 38, 60 ppm) results in significant initial changes in particle radius and refractive index, consistent with the rapid loss of reactive functional groups (carbon–carbon double bond), followed by successive polymerization reactions between ozonolysis products. In contrast, exposure of squalene to gaseous oxygen in the presence of light results in an increase in the refractive index and a relatively smaller but delayed decrease in droplet radius. A waxy solid is formed after 30 and 75 min for the ozonolysis and light-induced oxidations of squalene, respectively, indicating faster solidification of squalene-containing organic aerosol in the presence of ozone.

The spectroscopic fingerprints of vibrationally excited states of astronomical molecules are interesting for multiple reasons. They are excellent temperature probes of the corresponding astronomical regions and are thought to be the origin of many unknown lines in astronomical survey spectra. Rovibrational spectra provide accurate vibrational energies and can guide subsequent pure rotational studies. The Automated Spectral Assignment Procedure (ASAP) greatly simplifies the rovibrational analysis when the rotational spectrum of either the upper or lower vibrational state is known with a high degree of accuracy (e.g., from a rotational analysis). Here, we present a new implementation of ASAP for the analysis of cyclopentadiene, a cyclic pure hydrocarbon that has already been detected astronomically toward the cold core of the Taurus Molecular Cloud. Using the synchrotron radiation extracted by the AILES beamline of the SOLEIL facility, we recorded mid- and far-infrared high-resolution spectra of cyclopentadiene. We analyzed the rovibrational spectrum of the ν₂₁ fundamental (961 cm^–1) with ASAP and used ASAP² to determine the vibrational energies of the eight vibrational modes below 860 cm^–1. ASAP² is an extension of ASAP for rovibrational bands where the rotational structures of the lower and upper states are known with high accuracy, leaving only the vibrational band center to be determined. The presented rovibrational fingerprints agree with the results from pure rotational spectroscopy, demonstrating the efficiency and reliability of our new ASAP implementation.

Magnesium chloride hydrates show a rich diversity of structural forms, with different hydration numbers ranging from 1 to 12. We show that this structural versatility is also present within the same hydration numbers, with the formation of a new phase of magnesium chloride decahydrate (MgCl₂·10H₂O-II) stable at the conditions of 0.03–0.40(14) GPa at 234(11) K and up to 2.11(3) GPa at 220(2) K, as determined by in situ single-crystal X-ray diffraction. The hydrogen bonding interactions of MgCl₂·10H₂O-II are identified and the bulk modulus determined at B₀ = 18.9(12) GPa at 220(2) K. We discuss the implication of this high-pressure MgCl₂ hydrate for icy moon compositional investigations and showcase the structural and density changes between the various hydrates in MgCl₂·nH₂O.

Noneruptive volcanic degassing is a major but poorly understood pathway of carbon recycling from Earth’s interior. Here we present a three-year (2019–2022) record of fumarolic CO₂ isotopic compositions (δ¹³C and δ¹⁸O) from six fumarolic sites within the Tatun Volcano Group, Taiwan, along with γ-ray data. The δ¹³C values showed pronounced temporal variability with spatial coherence in the region, reflecting changes in the CO₂ sources. Three CO₂ sources were identified: mantle, carbonate, and organic. Bayesian mixing models were used to constrain the contributions of these sources. The average contributions are approximately mantle 45%, organic matter 15%, and carbonate 40%, with the mantle and carbonate components representing deep sources while the organic matter reflects shallow sedimentary or hydrothermal sources. Episodic changes in the sources coincide with γ-ray anomalies, indicating subsurface fracturing that facilitates fluid migration to the surface. The coupled temporal variation in δ¹³C and γ-ray activity suggests that the CO₂ dynamics is largely controlled by caprock sealing and fluid accumulation beneath a low-permeability layer, leading to pressurization, fracturing, and the ascent of deep fluids and hydrothermal solutes. This study provides a conceptual framework for interpreting transient fumarolic CO₂ dynamics in volcanic–hydrothermal systems.

Isoprene is the single most abundant nonmethane hydrocarbon emitted into the atmosphere. Despite this, uncertainties in the oxidation chemistry remain. Here, we investigate the yields of Criegee intermediates that are produced from the ozonolysis reaction, where we conduct a series of atmospheric simulation chamber experiments in which the transient stabilized Criegee intermediates (sCIs) are titrated in the gas phase using either biacetyl or acetylpropionyl. This reaction yields a stable ketone-substituted secondary ozonide (SOZ), which was observed directly in the gas phase using a proton-transfer-reaction time-of-flight mass spectrometer operated in NH₄⁺ mode. Both C₁ and C₄ sCIs were observed in this way, with the mass of the NH₄⁺ adduct shifting according to the mass of the sCI and its diketone titrant. The relative abundance of the C₄ sCI was constrained against C₁ assuming a similar sensitivity for the two SOZ derivatives. This was supported by quantum chemical calculations that demonstrated very similar binding energies between NH₄⁺ and the C₁ and C₄ SOZ adducts. Our results demonstrate an overall yield of ∼11% for the long-lived C₄ sCIs, which may survive long enough to participate in various bimolecular reactions in the atmosphere.

In the past decade, there has been a significant shift in astrochemistry with a renewed focus on the role of nonthermal processes on the molecular interstellar medium, in particular energetic particles (such as cosmic ray particles and fast electrons) and X-ray radiation. This has been brought about in large part due to new observations of interstellar complex organic molecules in environments that would inhibit their formation, such as cold, dense gas in prestellar cores or in the highly energetic environments in galactic centers. In parallel, there has been a plethora of new laboratory investigations on the role of high-energy radiation and electrons on the chemistry of astrophysical ices, demonstrating the ability of this radiation to induce complex chemistry. In recent years, theoretical models have also begun to include newer cosmic-ray-driven processes in both the gas and ice phases. In this review, we unify aspects of the chemistry driven by X-ray radiation and energetic particles into a “high-energy astrochemistry”, defining this term and reviewing the underlying chemical processes. We conclude by examining various laboratories where high-energy astrochemistry is at play and identify future issues to be tackled.

Uncertainty has been identified around the release behavior of nonpertechnetate species from cementitious waste forms disposed at locations with a pathway to potable water. Nonpertechnetate species have been identified in the legacy nuclear wastes stored at the Hanford Site, yet little is known regarding the retention behavior of nonpertechnetate species from cementitious waste forms. This work presents an evaluation of the nonpertechnetate species immobilized as cementitious waste forms using real Hanford tank waste. The tank waste samples were stripped of pertechnetate leaving a nonpertechnetate inventory dominated by either Tc(VI) or Tc(I). Semidynamic leach testing of the resulting waste form samples was combined with a resin contact of the leachates to show a significant oxidation of the nonpertechnetate to pertechnetate (>80% conversion). The rate of oxidation and release of the nonpertechnetate compound was slower in the presence of reducing blast furnace slag in the waste form suggesting that reducing conditions can slow the oxidation process. These results mature the understandings around the behavior of nonpertechnetate within cementitious waste forms and around long-term waste form modeling for how to handle the release from a nonpertechnetate inventory in the parent waste stream.

The extraction of plant essential nutrients from extraterrestrial regolith will be necessary to ensure the sustainability of lunar and martian agriculture. An essential instrument of these outposts will be bioregenerative life support systems (BLiSS) that attempt to fully recycle nutrients from organic wastes. While BLiSS may not be fully efficient and lead to a reduction in the quantity of some elements, it is necessary to explore if regolith can be used to fortify the composition of BLiSS effluent. Lunar (JSC-1A) and martian simulants (MGS-1) were reacted with a high-fidelity BLiSS effluent from NASA’s Kennedy Space Center (KSC) in a 24 h batch experiment and compared to reactions with an inorganic nutrient solution and water. Net sorption and dissolution of elements were determined by quantification of reacting solutions using inductively coupled plasma-optical emission spectroscopy (ICP-OES), with P demonstrating Langmuir and Zn and K demonstrating Freundlich sorption isotherms. The lunar simulant desorbed sizeable quantities of S, followed by Ca and Mg, while the martian simulant desorbed S, followed by Mg, Ca, and Na. Elemental bonding of C, N, P, and Ca was observed on the simulant solid phase with X-ray photoelectron spectroscopy (XPS) after reaction with BLiSS solution. Minerals after experimentation were observed using scanning electron microscope−electron dispersive spectroscopy (SEM-EDS), revealing pitting in JSC-1A and covering of nanoparticles in MGS-1. There were marked differences between the reactions of the inorganic nutrient solution compared to BLiSS effluent, indicating the necessity to study high-fidelity solutions over single-element model systems. Overall, lunar and martian regoliths contain highly soluble components that may fortify BLiSS effluents with valuable metals and plant essential nutrients.

The thioketenyl cation (HCCS⁺) has been recently detected in the dark cloud TMC-1 by radioastronomical observations within the QUIJOTE survey. However, the infrared (IR) spectrum of this ion is yet to be reported in the literature. Spectroscopic reference data are essential for the search of HCCS⁺ using the James Webb Space Telescope, not only in molecular clouds and star-forming regions, but also in the ionospheres and upper atmospheres of exoplanets. In this work, we demonstrate a method for the selective generation of the HCCS⁺ ion in its triplet ground state (³Σ^–) and use this method to obtain IR band positions for HCCS⁺. The IR-action spectrum of H₂-tagged HCCS⁺ has been measured in a cryogenic 22-pole ion trap via IR photodissociation (IR-PD) spectroscopy with the FELIX light source in the wavenumber regions 450–1850 and 3000–3350 cm^–1. Spectral information is complemented by theoretical calculations on the fragmentation mechanisms leading to the formation of HCCS⁺ from dissociative ionization of 2,5-dibromothiophene. The assignment of the experimental HCCS⁺ vibrational bands is aided by comparison with ab initio computed values from literature and from calculations at the UB3LYP/cc-pVQZ level of theory, for both the triplet (³Σ^–) and singlet (¹Σ⁺) states of HCCS⁺. The experimental HCCS⁺ spectra show an overall good agreement with the scaled theoretical values (to account for anharmonicity effects), facilitating assignment of the IR spectral features. These findings will enable new reactivity investigations and spectroscopic measurements to be conducted, and for HCCS⁺ to be included in astrochemical models and databases.