Volatility Distribution Research Articles

Land of Gas and Dust – Exploring Bursting Cavities on Comet 67P

Abstract Gas and dust outbursts are recurring phenomena on comets, offering critical insights into their subsurface activities. On comet 67P/Churyumov-Gerasimenko, two distinct outburst types have been identified: CO2-dominated ”summer fireworks” near perihelion and water-driven events often linked to cliff collapses outside the perihelion period. While CO2-dominated outbursts are thought to originate from subsurface gas cavities, the properties of these cavities remain poorly understood. In this study, we modelled the outgassing dynamics and dust velocities of outburst events using Rosetta/ROSINA data to estimate the characteristics of subsurface gas cavities and their impact on ejected particle dynamics. Our results indicate that CO2-dominated events involve subsurface cavities with radii ranging from 15 to 62 m for an equivalent half-sphere geometry, depending on gas distribution assumptions. Conversely, water-driven outbursts would require subsurface temperatures far above equilibrium, supporting the hypothesis of mechanical processes like cliff collapses exposing ices to sublimation. Dust velocities in CO2-dominated events – while aligning with results from other Rosetta instruments – were notably higher across all grain sizes compared to water-driven events, reflecting distinct dynamics in dust ejection. These findings highlight the critical role of subsurface gas reservoirs in driving explosive outbursts and suggest a strong connection between cometary activity, volatile distribution, and structural conditions. This study emphasises the need for high-resolution data on subsurface volatiles from future missions and more refined modelling and experiments to further elucidate these mechanisms, with potential broader implications for our understanding of cometary activity.

Can volatile sulphides act as fumigant or contact toxicant in cowpea weevil, Callosobruchus maculatus F.?: a comparative analysis

For understanding the toxic action of volatile sulphides, we have evaluated the insecticidal efficacy of sulphide mixture (diallyldisulfide, diallylsulfide and diallyltrisulfide) against Callosobruchus maculatus F. adults by fumigant toxicity (FT) and contact toxicity (CT) bioassays. Further, diffusional characteristics of sulphides inside the treatment vials were analysed by GC-FPD and microstructural impacts on treated beetles were observed using SEM. In the comparative analysis, maximum level of insecticidal toxicity (0.88 µl/L of LC50), residue persistence (32.28 ppm/adult) and microstructural aberration in beetle elytra was observed in CT compared to FT bioassay (1.60 µl/L of LC50 and 22.67 ppm/adult of residue). Whereas, the GC-FPD based diffusion analysis indicated even distribution of volatiles inside the vials in both FT and CT bioassays. The study results suggests that volatiles act as fumigant/vapours in both bioassays with respect to even diffusion and toxicity occurs based on insect–volatile contacts inside the treatment chambers.

C/O ratios in self-gravitating protoplanetary discs with dust evolution

Abstract Elemental abundances, particularly the C/O ratio, are seen as a way to connect the composition of planetary atmospheres with planet formation scenario and the disc chemical environment. We model the chemical composition of gas and ices in a self-gravitating disc on timescales of 0.5 Myr since its formation to study the evolution of C/O ratio due to dust dynamics and growth and phase transitions of the volatile species. We use the thin-disc hydrodynamic code FEOSAD, which includes disc self-gravity, thermal balance, dust evolution, and turbulent diffusion, and treats dust as a dynamically different and evolving component interacting with the gas. It also describes freeze-out, sublimation, and advection of four most abundant volatile species: H $_2$ O, CO $_2$ , CH $_4$ , and CO. We demonstrate the effect of gas and dust substructures such as spirals and rings on the distribution of volatiles and C/O ratios, including the formation of multiple snowlines of one species, and point out the anticorrelation between dust-to-gas ratio and total C/O ratio emerging due to the contribution of oxygen-rich ice mantles. We identify time and spatial locations where two distinct trigger mechanisms for planet formation are operating and differentiate them by C/O ratio range: wide range of the C/O ratios of $0-1.4$ for streaming instability, and a much narrower range $0.3-0.6$ for gravitational instability (with the initial value of 0.34). This conclusion is corroborated by observations, showing that transiting exoplanets, which possibly experienced migration through a variety of disc conditions, have significantly larger spread of C/O in comparison with directly imaged exoplanets likely formed in gravitationally unstable outer disk regions. We show that the ice-phase $\textrm{C/O}\approx$ 0.2–0.3 between the CO, CO $_2$ , and CH $_4$ snowlines corresponds to the composition of the Solar system comets, that represent primordial planetesimals.

The Microbial Diversity and Flavor Metabolism Regulation of Xiangzao During Different Natural Fermentation Time Periods.

Xiangzao brine is a special flavored food produced by the natural fermentation of Huangjiu lees. To clarify fermentation time on its quality, this study integrated flavoromics analysis, macro-genomics, and polypeptide omics to analyze the volatile flavor components, microbial species, and flavor peptide distributions of four groups of samples (XZ-1Y, XZ-2Y, XZ-3Y, and XZ-4Y) fermented for 1-4 years. The results showed that the samples fermented for 1 year had the highest contents of umami amino acids and umami peptides, and the samples fermented for 4 years had the highest contents of organic acids and fruity components. In addition, 42 volatile flavor components and 532 peptides were identified, including 393 umami taste peptides and only 37 bitter taste peptides. Correlation analysis showed that ethyl lactate and furfural were positively correlated with the abundance of Nocardioides and Stenotrophomonas, respectively. The abundance of Pseudomonas was positively correlated with four previously unreported umami peptides (FATPR, RELER, FNLERP, and RSSFLGQ) screened by molecular docking. This study provides a reference for the flavor metabolism regulation of Xiangzao brine.

Brownness of organics in anthropogenic biomass burning aerosols over South Asia

Abstract. In South Asia, biomass is burned for energy and waste disposal, producing brown carbon (BrC) aerosols whose climatic impacts are highly uncertain. To assess these impacts, a real-world understanding of BrC's physio-optical properties is essential. For this region, the order-of-magnitude variability in BrC's spectral refractive index as a function of particle volatility distribution is poorly understood. This leads to oversimplified model parameterization and subsequent uncertainty in regional radiative forcing. Here we used the field-collected aerosol samples from major anthropogenic biomass activities to examine the methanol-soluble BrC optical properties. We show a strong relation between the absorption strength, wavelength dependence, and thermo-optical fractions of carbonaceous aerosols. Our observations show strongly absorbing BrC near the Himalayan foothills that may accelerate glacier melt, further highlighting the limitations of climate models where variable BrC properties are not considered. These findings provide crucial inputs for refining climate models and developing effective regional strategies to mitigate BrC emissions.

Volatile Distribution in Flowers of Lathyrus odoratus L. by HS-SPME-GC Technique and Enantiomeric Separation Data.

Lathyrus odoratus L., commonly known as sweet pea, is a plant with a distinctive aroma that can develop in various habitats. An analysis of the aromatic profile of the species was conducted using the HS-SPME (solid-phase microextraction headspace) technique. This study aimed to explore the composition of and variation in the floral scent emissions of L. odorathus. The floral scents from fresh flowers were collected over different months and analyzed using gas chromatography coupled with mass spectrometry on apolar and polar stationary phase columns. In the apolar column, the majority compounds included linalool (19.27-5.79%), α-trans-bergamotene (29.4-14.21%), and phenyl ethyl alcohol (30.01-1.56%), while on the polar column, the predominant compounds included myrcene (13.25%), (E,E)-α-farnesene (26.33-8.16%), α-trans-bergamotene (42.09-24.82%), and others. This investigation was complemented by enantioselective analysis using a chiral phase based in cyclodextrins, which revealed the presence of (1R)-(+)-α-pinene, (S)-(-)-limonene, (R)-(+)-germacrene D, and (R)-(E)-nerolidol as enantiomerically pure components and linalool as a racemic mixture. Notably, the principal component analysis (PCA) and heatmap revealed variations among the chemical compounds collected at different harvest times. This demonstrates that temporal factors indeed impact chemical compound production. Furthermore, research on the aromatic properties of flowers provides a theoretical basis for studying and improving the components of their scent.

Distribution of Pb, Zn, Fe, As, Sn, Sb, Bi, and Ni Between Oxide Liquid and Metal in the ‘CuO0.5’-CaO-AlO1.5 System in Equilibrium with Cu Metal at 1400 °C

AbstractThe increasing complexity of ore resources and recycled materials in the feed of pyrometallurgical processes present a technical challenge to the metallurgical engineers working on maximizing the recovery of the valuable elements and minimizing the environmental impact of the processes. To address this challenge, the availability of computational tools that can predict the mass and energy balance in complex systems is required. Then, the accurate description of phase equilibria in the complex multicomponent systems describing the chemistry of the pyrometallurgical processes becomes critical for the correct implementation of the indicated tools and facing the outlined industrial challenges. In the present study, the distribution of selected elements (Pb, Zn, Fe, As, Sn, Sb, Bi, and Ni) between oxide liquid and metal in the ‘CuO0.5’–CaO–AlO1.5 system in equilibrium with Cu metal at 1400 °C (liquidus of CaAl2O4) was experimentally studied using the equilibration and quenching technique followed by the electron probe X-ray microanalysis of the resulted samples. The study covered a wide range of effective p(O2) over the system from 10−11 to 10−3.5 (corresponding to formation of immiscible CuO0.5-rich slag). To avoid loss of volatile elements (Pb, Zn, As, Sn, Sb, and Bi), a correlation between ‘CuO0.5’ in oxide liquid and p(O2) in open system was obtained first, followed by studying the volatile elements distribution in closed conditions (Al2O3 crucible sealed in SiO2 ampoule), where ‘CuO0.5’ concentration was used as a marker to evaluate the effective p(O2) over the system. The experimental results were then used for the optimization of the thermodynamic model parameters of the system as part of the integrated experimental and self-consisting thermodynamic modeling research program of phase equilibria in the Cu–Pb–Zn–Fe–Ca–Si–Al–Mg–O–S–(As, Sn, Sb, Bi, Ag, Au, Ni, Cr, Co, and Na) gas/oxide liquid/matte/speiss/metal/solids system. Graphical Abstract

Influence of Terroir on the Grain Composition, and Volatile Profile of Irish Grain (Wheat) New Make Spirit

Terroir refers to the combination of environmental factors, such as climate, soil, and agricultural practices, that shape the characteristics of a crop, contributing to the unique qualities of the final product. The concept has been traditionally linked to wine, but some recent findings suggest that it also holds importance for distilled spirits. The expanding Irish distilling sector is shifting towards local raw materials such as wheat and rye, driven by regulatory changes, economic benefits, and consumer demand for sustainable local products. This research examines the effects of wheat variety, geographical location, and harvest year on grain composition and volatile composition of the new make spirit. For this study, twenty lab-scale wheat whiskey samples were produced from five different wheat varieties grown at two different locations in Ireland over two consecutive years. The wheat samples were analysed for grain composition and the volatile profiling of new make spirit samples by headspace solid-phase microextraction (HS-SPME) followed by gas chromatography–mass spectrometry (GC-MS). A total of fifty-one volatile compounds were detected, with ethanol, ethyl acetate, phenyl ethyl alcohol, and 3-methyl-1-butanol being predominant. Principal component analysis revealed that both the harvest year and geographical location moderately influenced the volatile compound distribution of the new make spirit, which is explained by a 43.25% variance. ANOVA analysis revealed that grain composition was significantly influenced by harvest year, location, and wheat variety. The 2020 samples showed higher protein and β-glucan content, whereas samples from the location Tipperary had higher starch content. This study indicates that terroir—specifically seasons (year) and geography (location)—affects the characteristics of wheat-based Irish whiskey, highlighting opportunities for distillers to differentiate their products by leveraging local environmental factors.

NEIVAv1.0: Next-generation Emissions InVentory expansion of Akagi et al. (2011) version 1.0

Abstract. Accurate representation of fire emissions is critical for modeling the in-plume, near-source, and remote effects of biomass burning (BB) on atmospheric composition, air quality, and climate. In recent years application of advanced instrumentation has significantly improved knowledge of the compounds emitted from fires, which, coupled with a large number of recent laboratory and field campaigns, has facilitated the emergence of new emission factor (EF) compilations. The Next-generation Emissions InVentory expansion of Akagi (NEIVA) version 1.0 is one such compilation in which the EFs for 14 globally relevant fuel and fire types have been updated to include data from recent studies, with a focus on gaseous non-methane organic compounds (NMOC_g). The data are stored in a series of connected tables that facilitate flexible querying from the individual study level to recommended averages of all laboratory and field data by fire type. The querying features are enabled by assignment of unique identifiers to all compounds and constituents, including thousands of NMOC_g. NEIVA also includes chemical and physical property data and model surrogate assignments for three widely used chemical mechanisms for each NMOC_g. NEIVA EF datasets are compared with recent publications and other EF compilations at the individual compound level and in the context of overall volatility distributions and hydroxyl (OH) reactivity (OHR) estimates. The NMOC_g in NEIVA include ∼4–8 times more compounds with improved representation of intermediate volatility organic compounds, resulting in much lower overall volatility (lowest-volatility bin shifted by as much as 3 orders of magnitude) and significantly higher OHR (up to 90 %) than other compilations. These updates can strongly impact model predictions of the effects of BB on atmospheric composition and chemistry.

JWST Ice Band Profiles Reveal Mixed Ice Compositions in the HH 48 NE Disk

Planet formation is strongly influenced by the composition and distribution of volatiles within protoplanetary disks. With JWST, it is now possible to obtain direct observational constraints on disk ices, as recently demonstrated by the detection of ice absorption features toward the edge-on HH 48 NE disk as part of the Ice Age Early Release Science program. Here, we introduce a new radiative transfer modeling framework designed to retrieve the composition and mixing status of disk ices using their band profiles, and apply it to interpret the H2O, CO2, and CO ice bands observed toward the HH 48 NE disk. We show that the ices are largely present as mixtures, with strong evidence for CO trapping in both H2O and CO2 ice. The HH 48 NE disk ice composition (pure versus polar versus apolar fractions) is markedly different from earlier protostellar stages, implying thermal and/or chemical reprocessing during the formation or evolution of the disk. We infer low ice-phase C/O ratios around 0.1 throughout the disk, and also demonstrate that the mixing and entrapment of disk ices can dramatically affect the radial dependence of the C/O ratio. It is therefore imperative that realistic disk ice compositions are considered when comparing planetary compositions with potential formation scenarios, which will fortunately be possible for an increasing number of disks with JWST.

Secondary Organic Aerosol Formation during the Oxidation of Large Aromatic and Other Cyclic Anthropogenic Volatile Organic Compounds.

The secondary organic aerosol (SOA) production from the reactions of anthropogenic large volatile (VOCs) and intermediate volatility organic compounds (IVOCs) with hydroxyl radicals under high NO x conditions was investigated. The organic compounds studied include cyclic alkanes of increasing size (amylcyclohexane, hexylcyclohexane, nonylcyclohexane, and decylcyclohexane) and aromatic compounds (1,3,5-trimethylbenzene, 1,3,5-triethylbenzene and 1,3,5-tritert-butylbenzene). A considerable amount of SOA was formed from all examined compounds. For the studied cyclohexanes (C11-C16) there appears that the SOA yield depends nonlinearly on the length of their substitute chain. The large cyclohexanes had higher yields than the aromatic compounds, but the aromatic precursors produced a more oxidized SOA. This was due to the production of lower volatility and O:C first generation products by the cyclohexanes. Most oxidation products (with C* < 104 μg m-3) in the case of cyclohexanes are SVOCs (∼50%), while of aromatics are IVOCs (∼60%). Structure, molecular size, and length of the substitute chain of the parent hydrocarbon were found to play key roles in SOA formation, oxidation state, and volatility. The SOA volatility distribution, effective vaporization enthalpy, and effective accommodation coefficient were also quantified by combining SOA yields, thermodenuder (TD) and isothermal dilution measurements. Parameterizations for the Volatility Basis Set (VBS) are proposed for future use in chemical transport models.

Assessing the effect of size and shape factors on the devolatilization of biomass particles by coupling a rapid-solving thermal-thick model

In CFD modeling, while the isothermal assumption has conventionally been coupled for updating particle temperature, its applicability diminishes when dealing with thermally thick particles. A thermal-thick discrete phase model (DPM) is developed to simulate pyrolysis of biomass particle group at high heating rates and temperatures, with particles tracked in a Lagrangian scheme. The effects of particle size and shape on the volatile release and heating history are investigated. For spherical particles with a diameter of 9.6 mm, the temperature difference between the surface and center (∆T) does not disappear even up to 50 s. In the particle size range spanning from 200 μm to 9.6 mm, the duration required for a complete volatile release extends from 1.5 to 40 s. For cylindrical particles, in contrast to the particles with an aspect ratio (AR, ratio of particle length to diameter) of 1, the devolatilization time of particles with an AR of 15 can be shortened by more than 50 %. In addition, both the particle shape and size can significantly influence the volatile distribution within the reactor. This work contributes to understanding both the particle size and shape impact on heat and mass transfer during biomass pyrolysis at high heating rates.

Spatial and temporal characteristics of volatiles in the Cenozoic mantle beneath eastern China

Subduction of the paleo-Pacific Plate has transported volatiles from the surface to the interior of the Earth and significantly altered the chemical and physical properties of the Cenozoic mantle beneath eastern China. However, the characteristics of volatiles other than H2O in the Cenozoic mantle remain poorly constrained. To describe the spatiotemporal distribution of volatiles, including S, Cl, and H2O, in the Cenozoic mantle beneath eastern China, we performed reheating experiments and determined the composition of olivine-hosted melt inclusions from a large area (5.9 × 105 km2) of basalts. Calculations of the mantle-source compositions indicate that the Cenozoic mantle in North China is enriched in S but deficient in H2O and Cl, relative to that in South China. The distinctive features of volatiles likely arise from the different types of recycled materials in the mantle sources (such as Cl-containing sediments, carbonates, or sulfides in the altered oceanic crust) and their different proportions (from <1.7 % to 7 % of subducted sediments). Both the North China and South China mantles reached high volatile contents at 17.5–11.9 Ma, indicating that the activation of the South China mantle and the destruction of the North China Craton may have occurred simultaneously. These novel findings improve our understanding of mantle evolution beneath eastern China and will help in evaluating the contributions of slab subduction to the spatiotemporal heterogeneity of the lithospheric mantle during the Cenozoic.

Discrimination of coal geographical origins through HS-GC-IMS assisted with machine learning algorithms in larceny case

The process of globalization and industrialization has resulted in a rise in the theft of coal and other related products, thereby becoming a focal point for forensic science. This situation has engendered an escalated demand for effective detection and monitoring technologies. The precise identification of coal trace evidence presents a challenge with current methods, owing to its minute quantity, fine texture, and intricate composition. In this study, we integrated machine learning with the identification of volatiles to accurately differentiate coal geographical origins through the application of headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS). The topographic distribution of volatiles in coals was visually depicted to elucidate the subtle distinctions through spectra and fingerprint analysis. Additionally, four supervised machine learning algorithms were developed to quantitatively predict the geographical origins of natural coals utilizing the HS-GC-IMS dataset, and these were subsequently compared with unsupervised models. Remarkable volatile compounds were identified through the quantitative analysis and optimal Random Forest model, which offered a rapid readout and achieved an average accuracy of 100 % in coal identification. Our findings indicate that the integration of HS-GC-IMS and machine learning is anticipated to enhance the efficiency and accuracy of coal geographical traceability, thereby providing a foundation for litigation and trials.

Antimicrobial and antioxidative electrospun cellulose acetate-essential oils nanofibrous membranes for active food packaging to extend the shelf life of perishable fruits

Food preservation is critical to meeting the growing demand for fresh foods. We construct novel active packaging using active chemicals to extend the shelf life of fresh fruit and vegetables. In our study, we harnessed electrospinning technology to manufacture cellulose acetate nanofibers (CANFs) using natural, highly volatile cinnamon bark oil (CNO) and clove bud oil (CBO). The CNO and CBO loaded electrospun fibers were characterized and applied as active packaging membrane to evaluate the impact on shelf life of fresh grapes and tomatoes. Scanning electron microscopy (SEM), fourier-transform infrared spectroscopy (FT-IR), and gas chromatography–mass spectrometry (GC–MS) analysis indicated a uniform volatile component distribution, average fiber diameters, regulated release kinetics, and substantial antioxidant, and antibacterial activities. The use of 50 % w/w CNO and CBO-loaded CANFs as an active food packaging membrane for a shelf-life study of fresh grapes and tomatoes at 4 °C confirmed the microbiological safety of consumption for 40 days compared to 15 days in control samples, with a lesser reduction in physiochemical properties despite sensory evaluation revealing a shelf-life extension until 30 days.The efficacy and potential benefits of sustainable and effective packaging strategies are highlighted in this study, making it a promising alternative for preserving perishable tomatoes and grapes.

Volatile-char interactions during biomass pyrolysis: Effects of functionalized graphitized carbon nanotubes on volatile distribution of cellulose and its model compounds

Volatile-char interactions are prevalent in biomass pyrolysis processes. To gain deeper insights into their impact on biomass pyrolysis volatile distribution, interactions between volatile compounds and char during flash pyrolysis of glucose, cellobiose, and cellulose were investigated using a pyrolysis–gas chromatography/mass spectrometry detection technique, by modifying both the chain lengths of the raw materials and the functional groups of graphitized multi-walled carbon nanotubes (CNTs). The results reveal that volatile-char interactions markedly influence the distribution of the final pyrolysis products derived from glucose-based compounds. In the presence of any type of CNTs, dehydrated saccharides in the primary products, particularly levoglucosan (LG), exhibit the highest sensitivity to the interactions. Consequently, primary products such as LG and 5-hydroxymethylfurfural (HMF) undergo secondary pyrolysis, yielding compounds such as levoglucosenone (LGO) and 5-methyl-2-furancarboxaldehyde (FCM). Additionally, CNTs without functional groups are advantageous for the production of expensive LGO (The relative abundance reached 9.65%), whereas the relative abundance of FCM increases significantly with hydroxyl-, carboxyl-, and amino-modified carbon nanotubes. Particularly, the relative abundance of FCM is highest in the presence of amino-modified carbon nanotubes, regardless of whether the feedstock is glucose, cellobiose, or cellulose, with values of 25.14%, 23.32%, and 4.23%, respectively. Furthermore, consistent changes in product distribution trends among different glucose-based compounds under identical CNT conditions suggest that glycosidic bonds have minimal impact on volatile-char interactions.

Trace element detection in anhydrous minerals by micro-scale quantitative nuclear magnetic resonance spectroscopy

Nominally anhydrous minerals (NAMs) composing Earth’s and planetary rocks incorporate microscopic amounts of volatiles. However, volatile distribution in NAMs and their effect on physical properties of rocks remain controversial. Thus, constraining trace volatile concentrations in NAMs is tantamount to our understanding of the evolution of rocky planets and planetesimals. Here, we present an approach of trace-element quantification using micro-scale Nuclear Magnetic Resonance (NMR) spectroscopy. This approach employs the principle of enhanced mass-sensitivity in NMR microcoils. We were able to demonstrate that this method is in excellent agreement with standard methods across their respective detection capabilities. We show that by simultaneous detection of internal reference nuclei, the quantification sensitivity can be substantially increased, leading to quantifiable trace volatile element amounts of about 50 ng/g measured in a micro-meter sized single anorthitic mineral grain, greatly enhancing detection capabilities of volatiles in geologically important systems.

Enhanced Organic Nitrate Formation from Peroxy Radicals in the Condensed Phase.

Organic alkoxy (RO) and peroxy (RO2) radicals are key intermediates in multiphase atmospheric oxidation chemistry, though most of the study of their chemistry has focused on the gas phase. To better understand how radical chemistry may vary across different phases, we examine the chemistry of a model system, the 1-pentoxy radical, in three phases: the aqueous phase, the condensed organic phase, and the gas phase. In each phase, we generate the 1-pentoxy radical from the photolysis of n-pentyl nitrite, run the chemistry under conditions in which RO2 radicals react with NO, and detect the products in real time using an ammonium chemical ionization mass spectrometer (NH4 + CIMS). The condensed-phase chemistry shows an increase in formation of organic nitrate (RONO2) from the downstream RO2+NO reaction, which is attributed to potential collisional and solvent-cage stabilization of the RO2-NO complex. We further observe an enhancement in the yield of carbonyl relative to hydroxy carbonyl products in the condensed phase, indicating changes to RO radical kinetics. The different branching ratios in the condensed phase impact the product volatility distribution as well as HO x -NO x chemistry, and may have implications for nitrate formation, aqueous aerosol formation, and radical cycling within atmospheric particles and droplets.

How obliquity has differently shaped Pluto’s and Triton’s landscapes and climates

Triton and Pluto are believed to share a common origin, both forming initially in the Kuiper Belt but Triton being later captured by Neptune. Both objects display similar sizes, densities, and atmospheric and surface ice composition, with the presence of volatile ices N2, CH4, and CO. Yet their appearance, including their surface albedo and ice distribution strongly differ. What can explain these different appearances? A first disparity is that Triton is experiencing significant tidal heating due to its orbit around Neptune, with subsequent resurfacing and a relatively flat surface, while Pluto is not tidally activated and displays a pronounced topography. Here we present long-term volatile transport simulations of Pluto and Triton, using the same initial conditions and volatile inventory, but with the known orbit and rotation of each object. The model reproduces, to first order, the observed volatile ice surface distribution on Pluto and Triton. Our results unambiguously demonstrate that obliquity is the main driver of the differences in surface appearance and in climate properties on Pluto and Triton, and give further support to the hypothesis that both objects had a common origin followed by a different dynamical history.

Cabin air dynamics: Unraveling the patterns and drivers of volatile organic compound distribution in vehicles.

Volatile organic compounds (VOCs) are ubiquitous in vehicle cabin environments, which can significantly impact the health of drivers and passengers, whereas quick and intelligent prediction methods are lacking. In this study, we firstly analyzed the variations of environmental parameters, VOC levels and potential sources inside a new car during 7 summer workdays, indicating that formaldehyde had the highest concentration and about one third of the measurements exceeded the standard limit for in-cabin air quality. Feature importance analysis reveals that the most important factor affecting in-cabin VOC emission behaviors is the material surface temperature rather than the air temperature. By introducing the attention mechanism and ensemble strategy, we present an LSTM-A-E deep learning model to predict the concentrations of 12 observed typical VOCs, together with other five deep learning models for comparison. By comparing the prediction-observation discrepancies and five evaluation metrics, the LSTM-A-E model demonstrates better performance, which is more consistent with field measurements. Extension of the developed model for predicting the 10-day VOC concentrations in a realistic residence further illustrates its excellent environmental adaptation. This study probes the not-well-explored in-cabin VOC dynamics via observation and deep learning approaches, facilitating rapid prediction and exposure assessment of VOCs in the vehicle micro-environment.