ACS Earth and Space Chemistry最新文献

Sugar-related organic molecules identified in carbonaceousmeteoritesprovide key insight into the extraterrestrial inventory of prebioticcompounds. Here, density functional theory (DFT) calculations areused to investigate the adsorption of representative sugar acids andsugar alcohols from the Murchison meteorite on the forsterite (010)surface, a model silicate mineral relevant to planetary materials.The results show that adsorption occurs primarily through oxygen-containingfunctional groups, with both hydroxyl (−OH) and carboxylic(−COOH) groups forming stable Mg–O bonds with surfacemagnesium sites. Adsorption via the –COOH group is consistentlystronger than via –OH due to the combined effect of Mg–Ocoordination and additional hydrogen bonding. Calculated adsorptionenergies indicate chemisorption and increase systematically with carbonchain length, reflecting enhanced stabilization for larger molecules.Structural and electronic analyses, including Mg–O bond distances,Bader charge distribution, and density of states, reveal charge redistributionand orbital hybridization at the adsorbate–surface interface.These findings support a plausible mechanism in which sugar moleculescan be stabilized on silicate mineral surfaces, facilitating theirpreservation and delivery in meteoritic environments. The resultshighlight the potential role of mineral surfaces as both stabilizingsubstrates and reactive platforms in prebiotic chemical evolution.

The ability of simple amphiphiles to assemble into stablemembranesis central to understanding how protocells may have formed on earlyEarth. In this work, we examine how small structural differences,specifically hydrocarbon chain length and headgroup identity, influencemembrane formation, stability, and permeability in mixed amphiphilesystems exposed to diverse conditions to understand the role of theenvironment in protocell evolution. Using automated sample preparationand confocal microscopy, we characterized eight compositions containingdecyl sulfate (DS), dodecyl sulfate (DDS), or dodecyl phosphate (DDP)across a range of pH values in ultrapure water, sea salt, or sea saltmixed with a complex prebiotic organic solution. Longer-chain andphosphate-containing amphiphiles formed more vesicles, particularlyat low pH and high ionic strength. DS exhibited consistently low andenvironment-insensitive critical vesicle concentrations (CVCs), whereasDDP displayed the highest sensitivity to alkaline conditions. DDP-containingvesicles were the least permeable, highlighting the lipid packinginfluence of the phosphate headgroup. Together, these findings showthat small modifications in amphiphile composition strongly affectmembrane properties across early Earth-like environments, demonstratingthe role of anionic surfactants in protocell emergence.

Solid mineral-basedparticles have been proposed as alternativesto sulfates for climate intervention by stratospheric aerosol injection,as a possible means for improving optical or chemical characteristicsto thereby minimize risks and uncertainties. However, the heterogeneousreactivity of solid particles toward stratospheric trace gases, andpossible implications to the ozone layer, is currently not fully constrained,particularly at stratospheric concentrations. Here we present a systematiccomparative study of the uptake of nitric acid (HNO₃),hydrogen chloride (HCl), and nitrogen dioxide (NO₂) onfour mineral surrogates, calcite, alumina, crystalline silica (quartz),and amorphous silica, using complementary Knudsen cell and flow-throughreactor techniques. We find that NO₂ uptake coefficientsare relatively small on all surfaces, with estimated heterogeneousremoval time scales indicating negligible direct impact on stratosphericnitrogen chemistry. Conversely, measuring HCl uptake over a concentrationrange spanning five orders of magnitude, we find substantial steady-stateuptake rates with a pronounced concentration dependence. Extractingadsorption isotherms, we find that the steady-state surface coverageof HCl at low concentrations differs by four orders of magnitude betweenthe surfaces, with calcite exhibiting the highest HCl uptake capacityand amorphous silica the least, suggesting a dominant role of surfaceacid–base character. Using HCl surface coverage as a proxyfor the reactive uptake coefficient of ClONO₂, we estimatethat amorphous silica could produce substantially lower ozone depletiondue to chlorine activation than calcite or alumina under equivalentinjection scenarios. We also find a marked difference in uptake betweenthe crystalline and amorphous forms of silica, underscoring the sensitivityof heterogeneous chemistry to surface microstructure and the importanceof selecting particles with low-reactivity surfaces, in addition tothe consideration of bulk characteristics. Our findings motivate thedevelopment of particles with surfaces tailored for minimizing SAIrisks and uncertainties, including minimal reactivity with stratosphericgases and background sulfate aerosols.

Abiotic hydrogen gas (H₂) produced by the serpentinizationof ultramafic rocks has far-reaching implications, from geologicalH₂ production to the origin of life. In spite of this importance,the atomic-scale mechanism of H₂ formation remains unclear.Here, we investigate H₂ generation pathways on the hydratedolivine (010) surface using density functional theory (DFT+U) calculationswith van der Waals corrections. Both the M1 and M2 surface terminations─formedby cleavage through the M1 or M2 metal ion sites, respectively─wereexamined, each containing isolated and paired Fe(II) ions. We findthat isolated surface Fe(II) resists oxidation: while Fe(II) can transientlydonate an electron to adsorbed H₂O and induce reductivedissociation, the resulting charge-neutral H^• isunstable and loses the electron upon hopping to a neighboring O site.The energy required for simultaneous formation of two H^• radicals is also prohibitively high (∼3.5 eV), renderingH₂ generation via the combination of two H^• radicals unlikely. In contrast, paired Fe(II) at M1–M1 (adjacentions on the M1 surface) and M1–M2 (cross-layer pairs) are proneto oxidation, forming a [H^δ+–H^δ–] reaction intermediate (aproton-hydride pair) that facilitates H₂ generation. Therate-limiting step of the overall process is the reductive dissociationof H₂O on surface Fe(II), with an activation energy of∼1.9 eV. These findings indicate that H₂ can begenerated directly on olivine surfaces without invoking secondaryminerals such as magnetite. The site-specific oxidation of Fe(II)pairs explains why a large proportion of iron ions entering secondaryminerals remain ferrous. Overall, H₂ production in serpentinizingsystems may hinge on the spatial proximity of Fe(II) ions.

Ozonepollution remains a major challenge for air quality management,ecology and public health because of its nonlinear formation chemistry,strong meteorological modulation, multiscale transport and toxicity.Although chemical transport models and conventional statistical approachesare widely used, their ability to resolve high-dimensional interactions,regime-dependent behavior, and data heterogeneity is often limited.In this context, machine learning (ML) has emerged as a powerful complement,enabling high-resolution ozone prediction, multisource data integration,and data-driven attribution of key drivers. However, the rapid expansionof ML applications has outpaced systematic, chemistry-informed guidanceon model selection, interpretability, and physical consistency. Thisreview critically synthesizes recent advances in ML-based ozone research,spanning classical methods, tree-based ensemble models, deep learningarchitectures, and hybrid physical–ML frameworks. Rather thanemphasizing predictive accuracy alone, we assess where different modelfamilies succeed or may mislead when applied to ozone problems characterizedby chemical regime transitions, nonstationarity, and limited observations.By proposing a structured heuristic that links model selection toozone research goals, this review aims to guide ML from a predictivetool toward a principled component of atmospheric chemistry analysis.Such a shift could enhance forecasting robustness, improve mechanisticunderstanding, and support policy-relevant assessments in ozone pollutionresearch.

Sugarsplay essential roles in genetic and metabolic processes.However, it remains unclear how the sugar backbone of DNA could haveformed under prebiotic conditions. In the context of the RNA worldhypothesis, the abiotic formation of ribose─the backbone ofRNA─has been demonstrated by hydrothermal and γ-irradiationexperiments under conditions simulating meteorite parent bodies. However,the abiotic synthesis of 2-deoxyribose─the backbone of DNA─fromsimple carbon sources, such as HCHO and CH₃OH, has beenlimited. Here, we show that γ-irradiation under alkaline aqueousconditions simulating the interiors of meteorite parent bodies enablesthe formation of sugars, including both 2-deoxyribose and ribose,from simple carbon sources. These findings imply that ribose and 2-deoxyribosecould have coexisted in small bodies from which carbonaceous meteoritesoriginated, and been delivered to the early Earth, where they couldhave acted as precursors for RNA and DNA. More broadly, our resultshighlight the importance of radiation-driven chemistry within asteroidsas a key contributor to a chemically diverse stage of early molecularevolution. Moreover, early chemical evolution may have involved abroader repertoire of sugar backbones than previously assumed andmultiple noncanonical nucleic acids could have contributed to theorigin of life.

Mineral dust is a major atmospheric aerosol componentand an efficientreactive surface for trace gases, yet the mechanisms governing volatileorganic compound uptake under realistic humidity conditions remainpoorly constrained. Here, the first mechanistic investigation of methylglyoxal(MGL) uptake is presented on natural mineral dust under humid atmospheres.Using in situ diffuse reflectance infrared Fourier transform spectroscopy,we examine MGL interactions with Saharan (M’Bour) and Gobidusts, as well as CaCO₃, at relative humidity (RH) from20 to 80% under atmospheric pressure and room temperature. Resultsshow that MGL uptake remains efficient at atmospherically relevantRH but decreases with increasing humidity due to competition withwater for surface sites. Beyond physical adsorption, MGL undergoesreactive processing on dust surfaces, forming enolic and diketonespecies. The balance between reversible monomer uptake and reactiveconversion is strongly controlled by RH and dust mineralogy. WhileM’Bour dust exhibits a Langmuir–Hinshelwood-type two-stepmechanism, Gobi dust displays more complex behavior involving multiplesurface sites and partial irreversibility. Importantly, MGL uptakeinduces permanent depletion of surface hydroxyl groups, suggestinglong-term modifications of dust hygroscopicity. These findings demonstratethat mineral dust acts as an active, humidity-dependent sink for MGLand provide mechanistic constraints essential for improving representationsof dicarbonyl heterogeneous chemistry and secondary organic aerosolformation in atmospheric models.

Atmospheric simulationchambers are controlled experimentalplatformsused for studying atmospheric processes under near-realistic conditions.Here, a new facility specifically designed for research on troposphericmultiphase chemistry is presented. After introducing the facilityand its characteristics, the effects of initial methylglyoxal (MGLY)concentration, seed acidity, and relative humidity (RH) on secondaryorganic aerosol (SOA) formation from MGLY photooxidation in a coupledgas–particle system are examined. The Shandong University atmosphericsimulation chamber (SDU-C), located on Qingdao Campus, China, is afully computer-controlled, collapsible 18 m³ cylindricalchamber made of a 0.7 mm thick Teflon film, with a diameter of 3 mand a height of 2.4 m. Characterization experiments determined theSDU-C light intensity and wall-loss rates of NO₂, NO, O₃, and seed particles. The NO₂ photolysis frequency,J(NO₂), was (4.5 ± 0.02) ×10^–4·s^–1, while the wall-loss rates for NO, NO₂, O₃, and seed particles were (1.6 ± 0.1)×10^–6·s^–1, (6.6 ±1.4) ×10^–6·s^–1, (4.2± 0.7) ×10^–6·s^–1, and (4.4 ± 0.4) ×10^–5·s^–1, respectively. As its first application, a series of MGLY photooxidationexperiments were conducted with gas-phase oxidation initiated by OHradicals. Results showed that the initial MGLY uptake and photooxidation-drivenSOA formation increased with higher initial MGLY concentration [MGLY]₀, seed acidity, and RH. At 11% RH with neutral seeds, particlemass increased from 0.4 to 26.9 and 31.4 μg·m^–3 as the initial MGLY concentration increased from 72 to 144 and 216ppb, respectively. After ultraviolet A (UVA) irradiation, SOA massreached 43.2 μg·m^–3 for super acidicseeds at 50% RH and 216 ppb MGLY. Most particle-phase MGLY existsas oligomers (>95%), with higher [MGLY]₀ and RH, whilestrong acidity raises monomer levels. Overall, the characterizationfindings and first application indicate that SDU-C offers a reliableexperimental platform for exploring atmospheric multiphase chemistry,gas–particle partitioning, and SOA formation under controlledconditions.

Weak infrared (IR) bands near 1384 and 1353 cm^–1 (λ = 7.225 and 7.391 μm) have been observed in spectraof dark, cold molecular clouds for nearly 30 years. In 2000, we usedseveral lines of spectroscopic and chemical evidence to assign thesetwo features to the formate anion, HCOO^–. Here weexamine a recently proposed reassignment of the same two peaks toformamide and acetaldehyde. We find that radiolysis of ices made ofthe more-abundant interstellar ice compounds (e.g., H₂O,CO, CH₃OH) does not lead to an IR-detectable level of formamideand that only with a significant variation of ice composition frominterstellar values can acetaldehyde be made in a detectable amount.We conclude that the interstellar IR features reported near 1384 and1353 cm^–1 can be confidently assigned to HCOO^–, placing formate alongside cyanate (OCN^–) as the only two anions yet identified in interstellar ices. Suggestionsmade earlier to aid in IR spectral assignments in laboratory and extraterrestrialices are repeated and emphasized.

The origin of Earth’s water requires explanationof bothits abundance and its elevated D/H ratio relative to the solar nebula.Previous work (Asaduzzaman et al., 2015) demonstrated that dissociativechemisorption of water on olivine grains in the solar nebula couldsupply several ocean equivalents of water to the growing Earth. However,this mechanism has been challenged on isotopic grounds, as it doesnot inherently explain the enrichment of D/H ratios relative to solarvalues. Here, I quantify hydrogen isotopic fractionation between nebulargas and a set of condensed phases using a combination of quantum chemicalcalculations and statistical thermodynamics. Equilibrium fractionationfactors are determined as functions of temperature for (i) chemisorbedhydroxyls on olivine surfaces, (ii) structural hydroxyls in apatiteand pyroxenes (including pigeonite), and (iii) representative organiccompounds. The results show that deuterium is preferentially partitionedinto condensed phases, with enrichment factors increasing systematicallywith decreasing temperature. The calculated enrichment factors reachvalues comparable to those observed in terrestrial water, carbonaceouschondrites, Mars, and asteroid Vesta at temperatures of ∼175–300K. Kinetic constraints based on hydrogen diffusion in olivine indicatethat isotopic equilibration between gas and grain surfaces is plausiblewithin the lifetime of the solar nebula. These findings demonstratethat equilibrium gas–grain isotopic fractionation can naturallygenerate elevated D/H ratios in water adsorbed onto silicate grains.This study offers an explanation to prior criticism of adsorption-basedmodels by showing that nebular water can acquire terrestrial-likeisotopic compositions through low-temperature equilibration with grainsurfaces. Chemisorption-mediated accretion therefore provides a plausiblecomplementary mechanism for explaining both the abundance and isotopiccomposition of water in Earth and other inner solar system bodies,and may reduce part of the required contribution from carbonaceouschondrites.