ACS Earth and Space Chemistry最新文献

1,1-Diethoxyethane (DEE) is an oxygenated VOC with several uses in industry. This can result in its emission to the atmosphere, where it will undergo reactions with OH radicals. The kinetics of this reaction and its variation with temperature in the range of 273–363 K were examined in this work using pulsed laser photolysis─laser-induced fluorescence (PLP-LIF) experiment. The rate coefficient at 298 K was measured to be (1.78 ± 0.05) × 10^–11 cm³ molecule^–1 s^–1. The rate coefficients follow an Arrhenius equation k_DEE+OH^PLP-LIF (273–363 K) = (5.50 ± 1.10) × 10^–13 exp [(1026 ± 63)/T] cm³ molecule^–1 s^–1 with an inverse dependence on temperature. The rate coefficients calculated using the variational transition state theory at the CCSD(T)/aug-cc-pVDZ//M06-2X/aug-cc-pVDZ level also show good agreement with the measured values. Acetaldehyde and ethanol were identified as the products of the title reaction, and a mechanism for the degradation of DEE was elucidated. The impact of DEE emissions on the troposphere was also assessed using its atmospheric lifetime, radiative efficiency (RE), global warming potential (GWP) and photochemical ozone creation potential (POCP_E).

Studying the physicochemical properties of ice in astronomical environments is crucial to understanding the chemical processes involved in cosmic events such as comet and planet formation. The physical characteristics and chemical evolution on the surfaces of cosmic objects such as comets or interstellar grains offer key insights into these processes. This study focuses on α-pinene, a carbon- and hydrogen-rich molecule, which serves as a model for investigating radical-driven synthesis of more complex molecules under space-like conditions. It also provides a useful analogy for complex terrestrial organic molecules and sheds light on how organic matter interacts with water and radiation in extraterrestrial environments. In this work, we simulate the effects of heavy-ion cosmic ray bombardment on chiral molecules in the interstellar medium by analyzing the radiolysis of a C₁₀H₁₆/H₂O (1:1) mixture irradiated with 61.3 MeV ⁸⁴Kr¹⁵⁺ ions. Fourier Transform Infrared (FTIR) spectroscopy is employed to monitor the chemical evolution of ice samples at 10 K, both before and after irradiation. We identify 12 C_nH_m and ten C_nH_mO_k molecules, including complex products such as naphthalene (C₁₀H₈), glycolaldehyde (HCOCH₂OH), and methyl formate (HCOOCH₃). The most abundant hydrogenated product is acetylene (C₂H₂), followed by naphthalene (C₁₀H₈), while the most abundant oxygenated molecules are vinyl alcohol (CH₂CHOH) and ethanol (CH₃CH₂OH). Notably, the formation of CO₂ is minimal in this experiment. The destruction cross-sections of α-pinene and water in the (1:1) mixture are determined to be 3.5 and 6.4 × 10^–13 cm², respectively. The formation cross-sections for the products resulting from radiolysis are on average 2 × 10^–14 cm² for hydrocarbons and 0.6 × 10^–14 cm² for the oxygenated products.

Understanding the fate and transport of per- and polyfluoroalkyl substances (PFAS) at contaminated sites is crucial for effective remedial and regulatory decision-making. This interdisciplinary study offers a novel approach for estimating and mapping PFAS sorption properties and their impact on PFAS fate and transport. By integrating electromagnetic induction (EMI) surveys, physical and chemical sediment characterization, mineralogical characterization, and batch sorption experiments of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), we develop a comprehensive mapping of sorption dynamics. Sediments collected from a compound bar deposit were analyzed to establish correlations between EMI signal, sediment characteristics, and PFOA and PFOS sorption distribution coefficients (K_d). Sorption behavior and EMI response of these compounds were consistent with the sediments’ physical and chemical properties where K_d and electrical conductivity was higher with finer grain size, higher organic matter content, and higher aluminum and iron contents. The study demonstrates that EMI effectively maps PFAS sorption properties spatially, providing crucial insights into the sedimentological controls that govern both EMI responses and PFAS sorption. Correlation analysis yielded Pearson correlation values of 0.71 for EMI-PFOA K_d and 0.56 for EMI-PFOS K_d, underscoring the potential of EMI in predicting the spatial distribution of PFAS sorption in complex sedimentary environments. While these Pearson correlation values indicate moderate to strong correlations, their significance is amplified by the cost-effectiveness and extensive aerial coverage of EMI, the sparsity of sediment samples typically collected for batch sorption, and their spatial distribution. These results highlight the potential of EMI to identify sorption hotspots, thereby guiding targeted remediation efforts and enhancing site management strategies, ultimately reducing both costs and environmental impacts.

Radon is a gas associated with coal that is released during coal mining, storage, processing, transportation and utilization. Poor ventilation and small spaces can cause a sharp increase in the environmental radon concentration, increasing the potential radiation risk to miners. Coal radon emanation is related to the physical parameters of coal. In this study, a theoretical model of the radon exhalation of coal piles is established and the six main forms of radon gas generated by radium decay in coal are analyzed. It is determined that the main physical parameters affecting radon release are the radium nuclides, inorganic minerals, moisture, and pore structure. On this basis, the radon concentrations and physical parameters associated with different types of coal (lignite, long flame coal, weak caking coal, gas coal, coking coal, lean coal, and anthracite) in China’s coalfields are measured. The Gray correlation analysis method is then used to obtain the order of influence of coal physical parameters on radon release, i.e., radium concentration > total pore volume > moisture content > inorganic mineral content. The study results have important research significance and application value because they can be used to improve miners’ awareness of radon risks and provide fundamental data for coal-related enterprises to reduce radon pollution and formulate reasonable radon control measures.

Microbial iron(III) (Fe(III)) reduction plays an important role in the environment and is fundamentally driven by the oxidation of organic matter. However, most studies have primarily focused on how different Fe(III) is reduced by different bacteria, while largely overlooking the oxidation side of the reaction. Sugars as primary organic carbon inputs in soils can be utilized by some Fe(III)-reducing bacteria as electron donors. However, the effect of sugar input on microbial Fe(III) reduction remains poorly understood. In this study, we determined Fe(III) reduction kinetics and the extent of three glucose-metabolizing bacteria (Aeromonas sp. CD, Enterobacter sp. DN, and Bacillus sp. GX) at different glucose concentrations. Our results showed a positive correlation between glucose concentrations and the reduction of Fe(III) minerals (ferrihydrite), with significant increases in both the reduction rate and extent observed at low to moderate glucose levels (5–32 mM). However, compared to ferrihydrite, increasing glucose concentrations had a smaller effect on enhancing the reduction rate and extent of Fe(III)-citrate by the three strains. Glucose concentrations also influenced the promoting effect of an electron shuttle (AQDS), which enhanced ferrihydrite reduction at low glucose concentrations (5 mM) but exhibited weaker or even inhibitory effects at higher glucose concentrations (32–65 mM). Aeromonas sp. CD, with Mtr-based extracellular electron transfer systems (EET), exhibited higher Fe(III)-citrate reduction rates than the other strains, but the difference in ferrihydrite reduction rates was not as pronounced as in reducing Fe(III)-citrate and ferrihydrite with AQDS. Overall, this study highlights the crucial role of sugars and sugar-metabolizing Fe(III)-reducing bacteria in the iron biogeochemical cycle.

Unsaturated nitriles are significant in prebiotic and astrochemistry. Dicyanoacetylene, in particular, is a possible precursor of uracil and was previously detected in Titan’s atmosphere. Its null dipole moment hindered detection through rotational spectroscopy in interstellar clouds, and it escaped identification until recently, when its protonated form NC₄NH⁺ was finally detected toward the Taurus molecular cloud (TMC-1) (Agúndez et al., Astronom. Astrophys. 2023, 669, L1). Given the low-temperature conditions of both Titan and TMC-1, a facile formation route must be available. Low-temperature kinetics experiments and theoretical characterization of the entrance channel demonstrated that the CN + HC₃N reaction is a compelling candidate for NC₄N formation in cold clouds. Here, we report on a combined crossed-molecular beams (CMB) and theoretical study of the reaction mechanism up to product formation, demonstrating that NC₄N + H is the sole open channel from low to high temperatures (collision energies). Indeed, unlike other CN reactions, the formation of the isocyano isomer (3-isocyano-2-propynenitrile) was not seen to occur at the high collision energy (44.8 kJ/mol) of the CMB experiment. Preliminary calculations on the related CN + HC₅N reaction indicate that the reaction channel leading to NC₆N + H is exothermic and occurs via submerged transition states. We therefore expect it to be fast and that the mechanism is generalizable to the entire family of CN +cyanopolyyne reactions. Furthermore, we derive some properties of the related reactions C₂H + CNCN (isocyanogen) and CN + HCCNC (isocyanoacetylene): the C₂H + CNCN reaction leads to the formation of HC₃N + CN, and the main channel of the CN + HCCNC reaction also leads to CN + HC₃N. This last reaction efficiently converts isocyanoacetylene and, by extension, any isocyanopolyyne into their cyano counterparts without a net loss of cyano radicals. Finally, we also characterized the entrance channel of the reaction C₂H + NC₄N and verified that the addition of C₂H to all possible sites of NC₄N is characterized by a significant entrance barrier, thus confirming that, once formed, dicyanoacetylene terminates the growth of cyanopolyynes via the sequence of steps involving polyynes, cyanopolyynes, and C₂H/CN radicals.

Nuclear waste repository designs require immobilizing contaminants, including pertechnetate (TcO₄^–). Clay functionalized with organic cations (organoclay) has been shown to immobilize TcO₄^–. The current work measures the physicochemical properties of organoclays, tests each organoclay’s ability to retain TcO₄^–, and provides computational data for the orientation of the alkylammonium cation within the interlayer as well as binding energies for the pertechnetate–alkylammonium–clay system. The results show consistency between experimental and computational interplanar spacings and orientations, with indications that alkylammonium cations are sorbed to both the clay edge and interlayer sites during functionalization. Pertechnetate–alkylammonium interactions are calculated, and implications for TcO₄^– sequestration by organoclay are discussed.

Aqueous mixtures of inorganic and organic solutes display complex chemical behavior upon freezing. These systems are analogous to the ocean waters of icy moons in the outer solar system and play an important role in impacting the habitability and astrobiological potential of microenvironments contained in the ice shells. In this study, putative Enceladus ice cores are synthesized in the presence of a range of organic compounds typically found in carbonaceous chondrite meteorites (glycerol, glyceric acid, and 2,3-dihydroxybenzoic acid), and their spatial distribution is investigated using Raman imaging. The results demonstrate an intricate interplay among the water, ice, organic, and salt phases in dictating the partitioning of these components within the ice. Specifically, glycerol and glyceric acid are found to preferentially associate with hydrohalite, the primary salt hydrate that forms upon freezing (carbonates are also observed in these samples). However, the 2,3-dihydroxybenzoic acid (DHBA) system is found to exhibit a drastically different outcome, where the DHBA molecules agglomerate into organic-rich pockets instead of being colocated with the salt hydrates. Based on the molecular interactions previously demonstrated in the crystal structure of DHBA, we assign this behavior to the hydrophobicity of its aromatic ring and the presence of intramolecular hydrogen bonding, coupled with the slow-freezing condition that typically expels impurities from the ice and allows the DHBA molecules to come together. The findings provide insights into the chemical composition of brine channels, which hold important implications for the search for organics in ocean world ice shells. Particularly, while salt-rich zones may present enticing targets to look for simple organics, larger and more complex species with hydrophobic aromatic rings may be occluded elsewhere inside the ice, potentially requiring a more dedicated sampling/detection strategy.

The thermal maturation assessment of organic matter (OM) is crucial for understanding the hydrocarbon generation and expulsion processes in oil-bearing rocks. Vitrinite, a maceral found in coal samples, has its reflectance (%Ro) measurement widely used as a paleotemperature indicator in organic-rich sedimentary rocks. However, alternative methods are necessary to determine paleotemperature in sedimentary basins where vitrinite is scarce or absent, such as in presalt formations. This work used Raman spectroscopy to determine the reflectance equivalent in OM present in carbonate rocks from a presalt petroleum system (Santos Basin, Brazil). Vitrinite fragments present in palynofacies sections from a well of the Potiguar Basin, Rio Grande do Norte, Brazil, collected in different depths, with %Ro obtained in the range from 0.46 to 2.72%, were used as reference material to model calibration using their Raman spectral parameters, assisted by the Machine Learning Least Absolute Shrinkage and Selection Operator (LASSO) algorithm. The strategy was employed to analyze 30 samples of presalt carbonate rocks containing solid bitumen, whose Raman spectral parameters were used to determine their equivalent reflectance values (%R_Raman). Calibration with vitrinite samples was done using excitation radiation with wavelengths at 532 and 632.8 nm. The %R_Raman values were determined for all rock-containing bitumen samples using the exciting radiations. The methodology has proven to be an effective way to determine the OM thermal maturity.

Organic compounds, including sugars and their precursors, have been identified in the interstellar medium (ISM) and are of special prebiotic interest. Herein, we perform a detailed kinetic and thermodynamic analysis at CCSD(T)//M06–2X/aug-cc-pVTZ+ZPE level of three sugar precursors, glycolaldehyde (GA), glyceraldehyde (GLY), and dihydroxyacetone (DI), evaluating both their unimolecular degradation and formation pathways in the temperature range of 10–500 K. Our results reveal that all three species exhibit high activation energies for thermal fragmentation (E_a > 70 kcal mol^–1), which implies effective kinetic stability in cold environments (∼10K). This supports their possible persistence in dense molecular clouds and aligns with the mechanism proposed by [Yang, Z. Mol. Phys. 2024, 122, e2134832], where third-body collisions can stabilize reactive bimolecular complexes even at low temperatures. Among the formation routes investigated, the association of HCOH and H₂CO to form GA occurs predominantly through the barrierless abstraction of the hydroxylic hydrogen from trans-HCOH by carbonyl oxygen. Additionally, the thermal degradation indicates that DI exhibits a higher propensity for dissociation than its aldehydic counterparts (GA and GLY) above 100 K, although this difference diminishes at higher temperatures (>300 K), where their rates converge. These findings highlight the importance of integrating kinetic and thermodynamic data into astrochemical models to accurately assess the formation, survival, and destruction of organic molecules in different astrophysical environments.