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1.	Andersson, August (author) A Model for the Spectral Dependence of Aerosol Sunlight Absorption 2017 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 1:9, s. 533-539 Journal article (peer-reviewed)abstract Sunlight-absorbing aerosols, e.g., black and brown carbon (BC and BrC), have a potentially large, but highly uncertain contribution to climate warming. The spectral dependence of the aerosol absorption in the visible and near-UV regime is almost universally well-described with a heuristic power law, where the exponent is termed the absorption Angstrom exponent. However, the 2 underlying physicochemical causes for this relation are unknown. Here, a model is presented that predicts the emergence of the power law spectral dependence and unifies the absorption behavior of BC and BrC. Building on the theory of light absorption in amorphous materials, the interaction between multiple functional groups upon absorption is predicted to be a key feature for this broad spectral dependence. This aerosol amorphous absorption model is in agreement with recent empirical findings and provides a conceptual basis for the additional research needed to better constrain the optical properties of light-absorbing aerosols and their environmental impact.
2.	Boström, M., et al. (author) Dispersion Forces Stabilize Ice Coatings at Certain Gas Hydrate Interfaces That Prevent Water Wetting 2019 In: ACS Earth and Space Chemistry. - : American Chemical Society. - 2472-3452. ; 3:6, s. 1014-1022 Journal article (peer-reviewed)abstract Gas hydrates formed in oceans and permafrost occur in vast quantities on Earth representing both a massive potential fuel source and a large threat in climate forecasts. They have been predicted to be important on other bodies in our solar systems such as Enceladus, a moon of Saturn. CO 2 -hydrates likely drive the massive gas-rich water plumes seen and sampled by the spacecraft Cassini, and the source of these hydrates is thought to be due to buoyant gas hydrate particles. Dispersion forces can in some cases cause gas hydrates at thermal equilibrium to be coated in a 3-4 nm thick film of ice, or to contact water directly, depending on which gas they contain. As an example, the results are valid at a quadruple point of the water-CO 2 gas hydrate system, where a film is formed not only for the model with pure ice but also in the presence of impurities in water or in the ice layer. These films are shown to significantly alter the properties of the gas hydrate clusters, for example, whether they float or sink. It is also expected to influence gas hydrate growth and gas leakage.
3.	Brownwood, B., et al. (author) Gas-Particle Partitioning and SOA Yields of Organonitrate Products from NO3-Initiated Oxidation of Isoprene under Varied Chemical Regimes 2021 In: Acs Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 5:4, s. 785-800 Journal article (peer-reviewed)abstract Alkyl nitrate (AN) and secondary organic aerosol (SOA) from the reaction of nitrate radicals (NO3) with isoprene were observed in the Simulation of Atmospheric PHotochemistry In a large Reaction (SAPHIR) chamber during the NO(3)Isop campaign in August 2018. Based on 15 day-long experiments under various reaction conditions, we conclude that the reaction has a nominally unity molar AN yield (observed range 90 +/- 40%) and an SOA mass yield of OA + organic nitrate aerosol of 13-15% (with similar to 50 mu g m(-3) inorganic seed aerosol and 2-5 mu g m-3 total organic aerosol). Isoprene (5-25 ppb) and oxidant (typically similar to 100 ppb O-3 and 5-25 ppb NO2) concentrations and aerosol composition (inorganic and organic coating) were varied while remaining close to ambient conditions, producing similar AN and SOA yields under all regimes. We observe the formation of dinitrates upon oxidation of the second double bond only once the isoprene precursor is fully consumed. We determine the bulk partitioning coefficient for ANs (K-p similar to 10(-3) m(3) mu g(-1)), indicating an average volatility corresponding to a C-5 hydroxy hydroperoxy nitrate.
4.	Conrad, Sarah, et al. (author) Seasonal Variations of Redox State in Hemiboreal Soils Indicated by Changes of δ56Fe, Sulfate, and Nitrate in Headwater Streams 2019 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 3:12, s. 2816-2823 Journal article (peer-reviewed)abstract During recent decades, much focus has been put on the iron (Fe) isotope ratios in soils, rivers, and oceans, while studies on the variation in headwater streams are scarce. Here we assess seasonal water chemical data from 104 hemiboreal headwater streams. Between summer and late autumn, decreasing Fe concentrations and simultaneously increasing sulfate and nitrate concentrations suggest a shift from reduced to oxidized conditions in the soils along the main groundwater flow paths. Fe isotope data, obtained from a subpopulation of 16 streams, show low δ56Fe ratios during summer drought, indicating an important influx of reduced groundwater to the streams with primarily Fe(II) as an important Fe source. In total, the δ56Fe data ranged between −0.8 ± 0.1 and 1.8 ± 0.1‰ with the lowest values in summer and maximum δ56Fe ratios in late autumn or spring, indicating an influx of more oxidized, less Fe(II) rich groundwater during those seasons. Local differences in δ56Fe ratios between the headwater streams, seemed to be driven by the different soil redox status of the catchments. The streams with the lowest δ56Fe ratios during summer are characterized by a small share (4.4 ± 6.6%) of wetlands, indicating discharge of reduced groundwater from mainly anoxic, moist, organic-rich mineral soils during drought. Relatively high total organic carbon (TOC) concentrations (2.4 ± 1.1 mM) and low pH (5.2 ± 0.8) may have restricted efficient Fe(II) oxidation in streamwater especially during the late autumn survey. Our results from hemiboreal headwater streams reveal the importance of climatic, pedogenic, and land cover-derived controls on the provenance of stream Fe loads that is likely broadly applicable to similar streams elsewhere.
5.	D'Ambro, Emma L., et al. (author) Isothermal Evaporation of alpha-Pinene Ozonolysis SOA : Volatility, Phase State, and Oligomeric Composition 2018 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 2:10, s. 1058-1067 Journal article (peer-reviewed)abstract We present measurements of the isothermal evaporation of alpha-pinee ozonolysis secondary organic aerosol (SOA). Using a novel, filter-based method, we reproduce literature observations of the time-dependent evaporation of SOA particles. We apply two detailed physical models to interpret the evaporative behavior of both the bulk SOA and individual components. Both models find that a combination of effectively nonvolatile products, together with reversibly formed oligomers (or otherwise reactive monomers) having a decomposition lifetime of 9 to 28 h, best explains the evolution of composition and volatility as particles age in the absence of both organic vapors and oxidants, even under an assumption of relatively viscous (soft wax-like with a minimum diffusion coefficient of 1 x 10(-5) cm(2) s(-1)) particles. We find that the residence time in the SOA formation chamber and time spent undergoing isothermal evaporation, both indicative of the physical age of the aerosol, are the most important experimental parameters determining the evaporation rate. The evolution of volatility observed in these experiments is compared to field measurements in a boreal forest site. The ambient monoterpene-dominated SOA volatility is only reproduced in the laboratory after 24 h of extended aging in a dilute, dark, oxidant-free environment.
6.	Falcinelli, Stefano, et al. (author) The Fragmentation Dynamics of Simple Organic Molecules of Astrochemical Interest Interacting with VUV Photons 2019 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 3:9, s. 1862-1872 Journal article (peer-reviewed)abstract An experimental investigation on the fragmentation dynamics following the double photoionization of simple organic molecules of astrochemical interest, propylene oxide and N-methylformamide molecules, induced by VUV photons has been reported. Experiments used linearly polarized light in the 18–37 eV (propylene oxide) and 26–45 eV (N-methylformamide) photon energy range at the ELETTRA Synchrotron Facility of Trieste (Italy), coupling ion imaging and electron–ion–ion coincidence techniques with time-of-flight mass spectrometry. In the case of propylene oxide, six different two-body fragmentation processes have been recorded with the formation of CH2+/C2H4O+, CH3+/C2H3O+, O+/C3H6+, OH+/C3H5+, C2H3+/CH3O+, C2H4+/CH2O+ ion pairs. On the other hand, the double photoionization of N-methylformamide occurs producing two main fragmentation reactions, forming CH3+ + CH2NO+ and H+ + C2H4NO+. The relative cross sections and the threshold energies for all fragmentation channels are recorded as a function of the photon energy. Furthermore, in the case of the double photoionization of propylene oxide, the measure of the kinetic energy released distribution for the CH3+/C2H3O+ final ions with their angular distributions allowed the identification of a bimodal behavior indicating the possible formation of two different stable isomers of C2H3O+: acetyl and oxiranyl cations. The obtained results are important to clarify the physical chemistry of the elementary processes induced by the interaction of ionizing radiations with simple organic molecules of astrochemical interest: propylene oxide and N-methylformamide.
7.	Fauré, Nicolas, 1998, et al. (author) Unexpected Behavior of Chloride and Sulfate Ions upon Surface Solvation of Martian Salt Analogue 2023 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 7:2, s. 350-9 Journal article (peer-reviewed)
8.	Graeffe, Frans, et al. (author) Detecting and Characterizing Particulate Organic Nitrates with an Aerodyne Long-ToF Aerosol Mass Spectrometer 2023 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 7:1, s. 230-242 Journal article (peer-reviewed)abstract Particulate organic nitrate (pON) can be a major part of secondary organic aerosol (SOA) and is commonly quantified by indirect means from aerosol mass spectrometer (AMS) data. However, pON quantification remains challenging. Here, we set out to quantify and characterize pON in the boreal forest, through direct field observations at Station for Measuring Ecosystem Atmosphere Relationships (SMEAR) II in Hyytiälä, Finland, and targeted single-precursor laboratory studies. We utilized a long time-of-flight AMS (LToF-AMS) for aerosol chemical characterization, with a particular focus to identify CxHyOzN+ (“CHON+”) fragments. We estimate that during springtime at SMEAR II, pON (including both the organic and nitrate part) accounts for ∼10% of the particle mass concentration (calculated by the NO+/NO2+ method) and originates mainly from the NO3 radical oxidation of biogenic volatile organic compounds. The majority of the background nitrate aerosol measured is organic. The CHON+ fragment analysis was largely unsuccessful at SMEAR II, mainly due to low concentrations of the few detected fragments. However, our findings may be useful at other sites as we identified 80 unique CHON+ fragments from the laboratory measurements of SOA formed from NO3 radical oxidation of three pON precursors (β-pinene, limonene, and guaiacol). Finally, we noted a significant effect on ion identification during the LToF-AMS high-resolution data processing, resulting in too many ions being fit, depending on whether tungsten ions (W+) were used in the peak width determination. Although this phenomenon may be instrument-specific, we encourage all (LTOF-) AMS users to investigate this effect on their instrument to reduce the possibility of incorrect identifications.
9.	Gramlich, Yvette, 1993-, et al. (author) Impact of Biomass Burning on Arctic Aerosol Composition 2024 In: ACS Earth and Space Chemistry. - 2472-3452. Journal article (peer-reviewed)abstract Emissions from biomass burning (BB) occurring at midlatitudes can reach the Arctic, where they influence the remote aerosol population. By using measurements of levoglucosan and black carbon, we identify seven BB events reaching Svalbard in 2020. We find that most of the BB events are significantly different to the rest of the year (nonevents) for most of the chemical and physical properties. Aerosol mass and number concentrations are enhanced by up to 1 order of magnitude during the BB events. During BB events, the submicrometer aerosol bulk composition changes from an organic- and sulfate-dominated regime to a clearly organic-dominated regime. This results in a significantly lower hygroscopicity parameter κ for BB aerosol (0.4 ± 0.2) compared to nonevents (0.5 ± 0.2), calculated from the nonrefractory aerosol composition. The organic fraction in the BB aerosol showed no significant difference for the O:C ratios (0.9 ± 0.3) compared to the year (0.9 ± 0.6). Accumulation mode particles were present during all BB events, while in the summer an additional Aitken mode was observed, indicating a mixture of the advected air mass with locally produced particles. BB tracers (vanillic, homovanillic, and hydroxybenzoic acid, nitrophenol, methylnitrophenol, and nitrocatechol) were significantly higher when air mass back trajectories passed over active fire regions in Eastern Europe, indicating agricultural and wildfires as sources. Our results suggest that the impact of BB on the Arctic aerosol depends on the season in which they occur, and agricultural and wildfires from Eastern Europe have the potential to disturb the background conditions the most.
10.	Gustafsson, Jon-Petter (author) Competitive Arsenate and Phosphate Adsorption on Ferrihydrite as Described by the CD-MUSIC Model 2022 In: ACS Earth and space chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 6, s. 1397-1406 Journal article (peer-reviewed)abstract The solubility and bioavailability of arsenic in the environment are to a large extent governed by adsorption reactionswith iron (hydr)oxides, the extent of which is affected by competitive interactions with other ions, for example, phosphate. Here,batch experiments were performed with ferrihydrite suspensions to determine the adsorption of arsenate [As(V)] and phosphate(PO4)atdifferent As(V)-PO4ratios. A surface complexation model based on the Charge Distribution MUltisite Ion Complexation(CD-MUSIC) concept (the"Ferrihydrite CD-MUSIC model") was developed to describe these interactions in a way consistent withresults from spectroscopic studies. For this purpose, several previously published data sets on As(V) and PO4adsorption inferrihydrite suspensions were reviewed, including a number of systems containing other major ions (CO32-and Ca2+), and newsurface complexation constants were derived. During model development, it was found that the inclusion of ternary complexes wasnot needed to describe the observed Ca2+-PO4interactions. For both As(V) and PO4, the resulting model predicts the presence ofcorner-sharing bidentate complexes as well as monodentate complexes, with the latter being important particularly at low pH. Theexperimental results showed that As(V) and PO4displayed similar adsorption patterns in the single-ion systems studied, which wereconducted using a constant anion-to-Fe ratio of 0.2. Even so, As(V) was preferentially adsorbed over PO4in competitive systems,particularly at low As(V)-to-PO4ratios when theKdvalues for As(V) were up to 2.1 times as high as those for PO4. The model,which described these patterns very well, suggests that adsorbed As(V) consists of a larger fraction of bidentate complexes than inthe case of PO4. This causes aflatter adsorption isotherm for As(V), which leads to a stronger As(V) adsorption as the As(V)-to-Feratio decreases, compared to that for PO4
11.	Gålfalk, Magnus, et al. (author) Sensitive Drone Mapping of Methane Emissions without the Need for Supplementary Ground-Based Measurements 2021 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 5:10, s. 2668-2676 Journal article (peer-reviewed)abstract Methane (CH4) is one of the main greenhouse gas for which sources and sinks are poorly constrained and better capacity of mapping landscape emissions are broadly requested. A key challenge has been comprehensive, accurate, and sensitive emission measurements covering large areas at a resolution that allows separation of different types of local sources. We present a sensitive drone-based system for mapping CH4 hotspots, finding leaks from gas systems, and calculating total CH4 fluxes from anthropogenic environments such as wastewater treatment plants, landfills, energy production, biogas plants, and agriculture. All measurements are made onboard the drone, with no requirements for additional ground-based instruments. Horizontal flight patterns are used to map and find emission sources over large areas and vertical flight patterns for total CH4 fluxes using mass balance calculations. The small drone system (6.7 kg including batteries, sensors, loggers, and weather proofing) maps CH4 concentrations and wind speeds at 1 Hz with a precision of 0.84 ppb/s and 0.1 m/s, respectively. As a demonstration of the system and the mass balance method for a CH4 source that is difficult to assess with traditional methods, we have quantified fluxes from a sludge deposit at a wastewater treatment plant. Combining data from three 10 min flights, emission hotspots could be mapped and a total flux of 178.4 +/- 8.1 kg CH4 d(-1) was determined.
12.	Jayaweera, Avon P., et al. (author) On the Mechanism and Quantum Tunneling of the CO2 + OH Anion Reaction in Ice: A Computational Study 2024 In: ACS EARTH AND SPACE CHEMISTRY. - 2472-3452. ; 8:7, s. 1451-1459 Journal article (peer-reviewed)abstract The mechanism of the reaction between CO2 and OH- (anion) in ice cluster models was determined using density functional theory (DFT), employing the omega B97X-D functional and def2-TZVP basis sets for all atoms. A range of reaction barriers, 0.08-0.43 eV, were found, and the lowest energy path has a barrier of 0.08 eV, giving rise to the bicarbonate ion (HCO3-). Computed rate constants, accounting for quantum tunneling by employing the Eckart potential, suggest that the CO2 + OH- -> HCO3- reaction can operate in ice at low temperatures (e.g., 10 K). In contrast, relatively high reaction barriers (0.52-0.74 eV) were found for the CO2 + OH center dot (radical) -> HCO3 center dot (radical) reaction, and the computed rate constants at low temperatures (e.g., 10 K) are extremely small. Based on the computed data, we argue that OH- can react with CO2 trapped in interstellar ice at 10 K, and the product of the reaction, HCO3-, is stable in ice. On the other hand, the OH radical does not react with CO2 in ice. Therefore, we propose that OH anions in interstellar ice play a role in the formation of precursors of complex organic molecules (COMs) in the interstellar medium. The present findings will open a new dimension to explore the chemical evolution in the interstellar medium through the chemistry of anions in interstellar ices.
13.	Lambertsson, Lars, et al. (author) Rapid dissolution of cinnabar in crude oils at reservoir temperatures facilitated by reduced Sulfur Ligands 2018 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 2:10, s. 1022-1028 Journal article (peer-reviewed)abstract Mercury (Hg) is present in petrochemical samples, including crude oils, and the processing and use of petroleum products contribute to global Hg emissions. We present a refined theory on geochemical processes controlling Hg concentrations in crude oil by studying dissolution kinetics and solubility thermodynamics of cinnabar (α-HgS(s)) in different crude oils held at reservoir temperatures. In a black light crude oil, α-HgS(s) dissolved in an apparent zero-order reaction with a rate of 0.14−0.58 μmoles m−2 s −1 at 170−230 °C and an estimated activation energy of 43 kJ mol−1 . For crude oil samples with a total sulfur concentration spanning 0.15− 2.38% (w/w), the measured dissolution rate varied between 0.05 and 0.24 μmoles m−2 s−1 at 200 °C. Separate tests showed that thiols and, to a lesser extent, organic sulfides increased the solubility of α-HgS(s) in isooctane at room temperature compared to thiophenes, disulfides, and elemental sulfur. Long-term (14 days) α-HgS(s) solubility tests in a crude oil at 200 °C generated dissolved Hg concentrations in the 0.3% (w/w) range. The high α-HgS(s) dissolving capacity of the crude oils was more than 2 orders of magnitude greater than the highest reported Hg concentration in crude oils globally. On the basis of the kinetic and solubility data, it was further concluded that α-HgS(s) is not stable under typical petroleum reservoir conditions and would decompose to elemental mercury (Hg0 ). Our results suggest that source/reservoir temperature, abundance of reduced sulfur compounds in the crude oil, and dissolved Hg0 evasion processes are principal factors controlling the ultimate Hg concentration in a specific crude oil deposit.
14.	Lindholm, Jerry, et al. (author) Deconvolution of Smectite Hydration Isotherms 2019 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 3:11, s. 2490-2498 Journal article (peer-reviewed)abstract Sorption isotherm models have traditionally served as an invaluable tool to characterize synthesized and natural mineral particles. However, for particles susceptible to substantial hydration, such as the swelling smectite clay minerals and other layered minerals displaying intercalation of discrete water monolayers, traditional isotherm models inadequately describe the total water uptake as a result of the change in available surface sites and area during the hydration process. With the goal of deconvoluting the water uptake behavior of swelling smectite minerals, this research presents a novel composite isotherm model that describes water uptake by surface adsorption, condensation, and stepwise intercalation. A set of eight montmorillonite samples ion-exchanged with different countercations (Li+, Na+, K+, Cs+, Mg2+, Ca2+, Sr2+, and Cu2+) were used to develop this model, which was based on gravimetric uptake measurements and X-ray diffraction data of basal spacings obtained from relative humidity conditions up to 98% relative humidity.
15.	Liu, Wanyu, et al. (author) Chemical and Hygroscopic Characterization of Surface Salts in the Qaidam Basin: Implications for Climate Impacts on Planet Earth and Mars 2021 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 5:3, s. 651-662 Journal article (peer-reviewed)abstract Salt particles play important roles in many atmospheric processes due to their high hygroscopicity. Saline lakes and playas are sources of salt particles, which are normally mixed with mineral dust that can be transported over long distances. In this study, salt samples collected from four saline lakes and surrounding playas in the Qaidam Basin are studied for their physicochemical properties, focusing on the chemical compositions and hygroscopicity. The salt samples include brines, lakebed salts, crust salts, and crystallized brines. Thermodynamic models are used to explain the precipitating and hygroscopic behaviors based on ionic compositions of dissolved saline solutions. Regarding the ionic compositions, the crystallized brines are similar to the complex mineral compositions of brines, while the natural solid salts, including lakebed salts and crust salts, show very distinct composition differences. The main difference between brines and natural solid salts is the presence of Mg2+ and SO42–, which are primarily found in brines but not in the solid phases. Moreover, all the crust salts are dominated by NaCl regardless of the chemical compositions of the nearby saline lakes. Positive matrix factorization is applied to the ionic concentrations, and the results show that solid salts and brines are governed by different factors. The pH of brines correlates with Mg2+ concentrations and is potentially influenced by ambient CO2 uptake. The hygroscopicity experimental results and thermodynamic model outcomes show that the water uptake of different salt types is controlled by different salt components, that is, crystallized brines are controlled by MgCl2 and natural salts are governed by NaCl and KCl. The characterizations of saline lake and playa salts improve the understandings of the roles that surface salts potentially play in the climate systems of both Planet Earth and Mars.
16.	Lutz, Anna, 1986, et al. (author) Gas to Particle Partitioning of Organic Acids in the Boreal Atmosphere 2019 In: Acs Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 3:7, s. 1279-1287 Journal article (peer-reviewed)abstract Gas to particle partitioning of carboxylic acids was investigated using a high-resolution chemical ionization time-of-flight mass spectrometer (HR-CI-ToF-MS) with the filter inlet for gases and aerosol (FIGAERO). Specifically, the partitioning coefficients of 640 components with unique molecular composition were calculated from an assumed linear relationship between [particle]/[gas] versus the mass of the organic fraction (M-org) according to Raoult's law, i.e., equilibrium phase partitioning. We demonstrate that, using the full data set, most of the compounds do not follow a linear relationship. This is especially the case for low- and high-molecular-weight species. Using a subset of the data, with concurrent low sulfate ambient observations ([SO42- < 0.4 mu g m(-3)), the relationship improved significantly and K-i could be derived from the slope of a linear regression to the data. The 100 species with the highest R-2 (>= 0.7) of this regression are presented. The restrictions during high sulfate conditions can be explained by changes in either the equilibrium conditions (e.g., the activity coeffient, gamma(i)) or uptake kinetics (mass transfer limitation). This study demonstrates that partitioning of compounds in the complex ambient atmosphere follows ideal Raoult's law for some limited conditions and stresses the need for studies also in more polluted environments.
17.	Priestley, Michael, et al. (author) Volatility Measurements of Oxygenated Volatile Organics from Fresh and Aged Residential Wood Burning Emissions 2024 In: ACS EARTH AND SPACE CHEMISTRY. - : American Chemical Society. - 2472-3452. ; 8:2, s. 159-173 Journal article (peer-reviewed)abstract Residential wood combustion (RWC) is a dominant source of anthropogenic aerosol in urban areas. Complexities in aerosol chemical composition, semivolatile behavior, and secondary processing make estimating RWC impacts on climate and air quality challenging. A chemical ionization mass spectrometer with a filter inlet for gas and aerosols measured the gas-to-particle partitioning of organic compounds emitted from log wood and pellet burning stoves. Emissions were aged in an oxidation flow reactor to assess changes in the volatilities of the secondary aerosol. Effective saturation vapor concentrations (C*) of the measured species were derived using both the measured particle-to-gas concentration ratio (P- i/G( i)) and vapor pressure measurements (p(i)( 0)) calibrated using the maximum temperature during evaporation. These were used to derive new molecular formula (MF) parameterizations and were compared to selected previous parameterization. The fresh wood stove emissions were less volatile than those of the pellet stove (particle fractions of 0.96 vs 0.69), likely caused by poorer combustion conditions, producing a greater particle sink for organic vapors. After aging, the volatility of the emissions remained broadly similar, whereas all MF parameterizations showed increasing volatility. This was likely due to the measurement techniques capturing nonideal effects of partitioning that MF parameterizations cannot.
18.	Rader, Erika, et al. (author) Preferably Plinian and Pumaceous : Implications of Microbial Activity in Modern Volcanic Deposits at Askja Volcano, Iceland, and Relevancy for Mars Exploration 2020 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 4:9, s. 1500-1514 Journal article (peer-reviewed)abstract To search more efficiently for a record of past life on Mars, it is critical to know where to look and thus maximize the likelihood of success. Large-scale site selection for the Mars 2020 mission has been completed, but small (meter to 10 cm)-scale relationships of microenvironments will not be known until the rover reaches the surface. Over a 2 m transect at a modern volcanic deposit on the flank of Askja volcano in the barren highlands of Iceland, we compared two biological indicators (ATP activity and 16SrRNA amplicon sequence composition) to physical characteristics including bulk chemical composition, spectral signatures of mineralogy, and grain size. Using analytical instrumentation analogous to those available on Mars rovers, we were able to characterize the geological setting of the deposits and link physical parameters to microbial abundance and diversity. In general, methanogenesis, methanotrophy/methylotrophy, and nitrate reduction were the functional traits most associated with microbial community shift along the transect. Core microbiome members tended to be associated with nitrate reduction, and relative abundance of core microbes was strongly related to free water in the deposit. Community compositional shift of the rare microbiome was related to microenvironmental changes such as change in grain size, geochemistry, and age of deposit. These correlations lead us to suggest a sampling strategy that accounts for Martian geology, looking for undisturbed (not remobilized) explosive volcanic ash below pumice that could maximize diversity and abundance of different bioindicators. Our study also illustrates the importance of studying the variability across microenvironments in low biomass settings on earth.
19.	Rosati, Bernadette, et al. (author) New Particle Formation and Growth from Dimethyl Sulfide Oxidation by Hydroxyl Radicals 2021 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 5:4, s. 801-811 Journal article (peer-reviewed)abstract Dimethyl sulfide (DMS) is produced by plankton in oceans and constitutes the largest natural emission of sulfur to the atmosphere. In this work, we examine new particle formation from the primary pathway of oxidation of gas-phase DMS by OH radicals. We particularly focus on particle growth and mass yield as studied experimentally under dry conditions using the atmospheric simulation chamber AURA. Experimentally, we show that aerosol mass yields from oxidation of 50-200 ppb of DMS are low (2-7%) and that particle growth rates (8.2-24.4 nm/h) are comparable with ambient observations. An HR-ToF-AMS was calibrated using methanesulfonic acid (MSA) to account for fragments distributed across both the organic and sulfate fragmentation table. AMS-derived chemical compositions revealed that MSA was always more dominant than sulfate in the secondary aerosols formed. Modeling using the Aerosol Dynamics, gas- and particle-phase chemistry kinetic multilayer model for laboratory CHAMber studies (ADCHAM) indicates that the Master Chemical Mechanism gas-phase chemistry alone underestimates experimentally observed particle formation and that DMS multiphase and autoxidation chemistry is needed to explain observations. Based on quantum chemical calculations, we conclude that particle formation from DMS oxidation in the ambient atmosphere will most likely be driven by mixed sulfuric acid/MSA clusters clustering with both amines and ammonia.
20.	Rund, Phil, et al. (author) A Coupled Volatility and Molecular Composition Based Source Apportionment of Atmospheric Organic Aerosol 2023 In: ACS Earth and Space Chemistry. - 2472-3452. ; 7:7, s. 1365-1377 Journal article (peer-reviewed)abstract We apply non-negative matrix factorization (NNMF) to molecular composition and volatility measurements of ambient sub-micrometer particles made using a high-resolution time of flight chemical ionization mass spectrometer (HRToF-CIMS) equipped with a custom filter inlet for gases and aerosols (FIGAERO) as part of the Southern Oxidant and Aerosol Study (SOAS). The resulting factors have a representative thermogram, which carries information on the factor volatility and unique weights for individual ions corresponding to molecular components of measured organic aerosol (OA). These properties and the diurnal patterns of factor weights are used to assign a specific source to each factor. With no a priori information used as input, the routine produces a set of factors with spectra that align well with those previously determined from several laboratory chamber experiments. The factorization routine gains relevance and separation of OA composition when using resolved thermograms as input rather than integrated thermogram time series. Of the seven factors produced by NNMF using the thermogram data, three are attributed to monoterpene-derived OA with extremely low, low, and semivolatile volatility. These three factors together represent 68% of the total organic aerosol mass examined, consistent with previous studies using a spectral basis set. Additionally, two factors were sourced to isoprene chemistry, one representing IEPOX-derived SOA, and the other relating to other oxidation products exhibiting relatively low volatility. The two isoprene-related factors account for 22% of OA mass. Notably absent is a category exclusively capturing the behavior of particulate organic nitrates (PON), which may be consistent with the relatively low local concentrations of PON observed and points to limitations of factorization to fully characterize OA. However, NNMF applied to the volatility and molecular level information from the FIGAERO HRToF-CIMS can resolve dominant precursors and chemical properties of ambient OA components with minimal assumptions.
21.	Sandström, Hilda, 1992, et al. (author) A Thermodynamic Landscape of Hydrogen Cyanide-Derived Molecules and Polymers 2024 In: ACS Earth and Space Chemistry. - 2472-3452. ; 8:6, s. 1272-1280 Journal article (peer-reviewed)abstract Hydrogen cyanide (HCN)-derived molecules and polymers are featured in several hypotheses on the origin of life. Over half a century of investigations into HCN self-reactions have led to many suggestions regarding the structural nature of the products and an even greater number of proposed polymerization pathways. A comprehensive overview of possible reactions and structures is missing. In this work, we use quantum chemical calculations to map the relative Gibbs free energy of most HCN-derived molecules and polymers that have been discussed in the literature. Our computed free energies indicate that several previously considered polymerization pathways are not spontaneous and should be discarded from future consideration. Among the most thermodynamically favored products are polyaminoimidazole and adenine.
22.	Sandström, Hilda, 1992, et al. (author) The Beginning of HCN Polymerization: Iminoacetonitrile Formation and Its Implications in Astrochemical Environments 2021 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 5:8, s. 2152-2159 Journal article (peer-reviewed)abstract Hydrogen cyanide (HCN) is known to react with complex organic materials and is a key reagent in the formation of various prebiotic building blocks, including amino acids and nucleobases. Here, we explore the possible first step in several such processes, the dimerization of HCN into iminoacetonitrile. Our study combines steered ab initio molecular dynamics and quantum chemistry to evaluate the kinetics and thermodynamics of base-catalyzed dimerization of HCN in the liquid state. Simulations predict a formation mechanism of iminoacetonitrile that is consistent with experimentally observed time scales for HCN polymerization, suggesting that HCN dimerization may be the rate-determining step in the assembly of more complex reaction products. The predicted kinetics permits for iminoacetonitrile formation in a host of astrochemical environments, including on the early Earth, on periodically heated subsurfaces of comets, and following heating events on colder bodies, such as Saturn’s moon Titan.
23.	Sewiło, Marta, et al. (author) Complex Organic Molecules in Star-Forming Regions of the Magellanic Clouds 2019 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 3:10, s. 2088-2109 Research review (peer-reviewed)abstract The Large and Small Magellanic Clouds (LMC and SMC), gas-rich dwarf companions of the Milky Way, are the nearest laboratories for detailed studies on the formation and survival of complex organic molecules (COMs) under metal-poor conditions. To date, only methanol, methyl formate, and dimethyl ether have been detected in these galaxies-all three toward two hot cores in the N113 star-forming region in the LMC, the only extragalactic sources exhibiting complex hot-core chemistry. We describe a small and diverse sample of the LMC and SMC sources associated with COMs or hot-core chemistry, and compare the observations to theoretical model predictions. Theoretical models accounting for the physical conditions and metallicity of hot molecular cores in the Magellanic Clouds have been able to broadly account for the existing observations, but they fail to reproduce the dimethyl ether abundance by more than an order of magnitude. We discuss future prospects for research in the field of complex chemistry in the low-metallicity environment. The detection of COMs in the Magellanic Clouds has important implications for astrobiology. The metallicity of the Magellanic Clouds is similar to that of galaxies in the earlier epochs of the universe; thus, the presence of COMs in the LMC and SMC indicates that a similar prebiotic chemistry leading to the emergence of life, as it happened on Earth, is possible in low-metallicity systems in the earlier universe.
24.	Singh, Dharmendra Kumar, et al. (author) Photochemical Processing of Inorganic and Organic Species in the Canadian High Arctic Aerosols : Impact of Ammonium Cation, Transition Metals, and Dicarboxylic Acids before and after Polar Sunrise at Alert 2021 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 5:10, s. 2865-2877 Journal article (peer-reviewed)abstract Temporal variations and correlation statistics of major inorganic and organic species and carbonaceous components of the total suspended particulate matter (TSPM) at Alert were concurrently studied. Organic carbon (OC) and water-soluble organic carbon (WSOC) declined from February to mid-March together with elemental carbon (EC), but OC and WSOC increased in April while EC stayed low, suggesting photochemical production of organic aerosols. WSOC/OC ratios peaked in mid-April (89%). The ammonium availability index (AAI) increases from 31% (before sunrise) to 58% (after sunrise). Strong correlations of NH4+ with WSOC and dicarboxylic acids (DCAs) were found, implying the formation of organic salts at polar sunrise. K+ is substantially correlated (R2 = 0.96; p = 0.03) with levoglucosan before sunrise; however, the correlation decreases after. Significant correlations were found for 5 cations (NH4+, Na+, K+, Mg2+, and Ca2+), 2-alkaline earth metals (Ca and Mg), and 3 transition metals (Fe, Cu, and Mn) with DCAs and WSOC during both periods. Fe and Cu are strongly correlated (up to R2 = 0.80; p < 0.05) with DCAs before and after polar sunrise, implying the Fenton reaction both in dark and light periods. On the basis of the significant correlation, we found the plausibility of Fenton chemistry of Fe and Cu with oxalic acid. In the multiple linear regression model, Mn is the most significant predictor of WSOC followed by Cu and Fe after sunrise. This study demonstrates the importance of the photochemical processing of Arctic aerosols that are carried by long-range transport to the Arctic at Alert, and bridges and answers the research gap and some questions raised in our previous study (regarding, for example, the impacts of inorganic species, primarily NH4+ and transition metals on organic aerosols).
25.	Tan, George K., et al. (author) Spatial Variation in Results of Biosignature Analyses of Apparently Homogeneous Samples from Mars Analogue Environments in Iceland 2022 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 6:6, s. 1472-1481 Journal article (peer-reviewed)abstract The search for signs of life on Mars and beyond is time consuming and labor-intensive; hence, it is critical to understand how to design sampling strategies that can maximize the likelihood of success. Two distinct Mars analogue environments in Iceland were selected to represent volcanic resurfacing and glacial environments where characterization of different biosignatures at various spatial scales (100 m, 10 m, 1 m, 10 cm) was performed. This study serves the twofold purposes of (1) understanding the different levels of biosignature distributions in these analogue environments and (2) the spatial distributions of biosignatures in these environments, with an overarching goal of drawing lessons from low biomass Mars analogue environments to inform the best sampling strategies for sample collection strategies on Mars. Our results show that samples should be collected for analysis at large (at least 100 m spacing) to capture most differences within an apparently homogeneous environment of the aged resurfaced volcanic region like Mælifellssandur, whereas a smaller spacing at 10 m scale is necessary for younger glacial–volcanic environments like Fimmvörduháls. This study also illustrates the importance of understanding the variability across spatial scales in sampling design for future planetary missions.
26.	Triesch, Nadja, et al. (author) Sea Spray Aerosol Chamber Study on Selective Transfer and Enrichment of Free and Combined Amino Acids 2021 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 5:6, s. 1564-1574 Journal article (peer-reviewed)abstract Free (FAAs) and combined amino acids (CAAs) were investigated on size-resolved samples of nascent sea spray aerosol (SSA) particles generated during controlled laboratory experiments. Compared to seawater, the amino acids were strongly enriched on the SSA particles. The enrichment factors (EFaer) on submicron SSA particles (EFaer Sigma(FAA): 2.5 x 10(6) and EFaer Sigma CAA: 7.9 x 10(5)) were 1-2 orders of magnitude higher than on supermicron ones (EFaerSFAA: 1.0 x 105 and EFaer Sigma(CAA): 7.3 x 10(4)) and continuously increased toward smaller SSA particles. Molecular-level analysis showed that the more polar the FAAs, the more they are enriched on the SSA particles (especially FAAs with polar acid side chains, e.g., aspartic acid: EFaer of 5.8 x 10(6)). Comparison of the amino acids present on nascent SSA with those present on ambient marine aerosol particles revealed a higher complexity of the amino acids of the nascent SSA, suggesting that atmospheric processes likely reduce the amino acid diversity. In addition, our results highlight that although almost all the amino acids studied are transferred to the atmosphere via bubble bursting under controlled conditions, two amino acids, gamma-aminobutyric acid (GABA) and glycine likely have additional sources to the atmosphere. GABA is likely formed on ambient marine submicron aerosol particles to a large extent (35-47% of Sigma FAA). Glycine likely originates from long-range transport processes or photochemical reactions, as discussed in the literature; however, our results highlight the potential for a direct oceanic source via bubble bursting (similar to 20% of Sigma FAA). Overall, bubble-bursting-derived total amino acids made up 11-18% of the mass of dissolved organic carbon on the submicron SSA particles.
27.	Wang, Xiaoming, et al. (author) Binding geometries of silicate species on ferrihydrite surfaces 2018 In: ACS Earth and Space Chemistry. - : AMER CHEMICAL SOC. - 2472-3452. ; 2:2, s. 125-134 Journal article (peer-reviewed)abstract Silicate sorption on ferrihydrite surfaces, as monomers, oligomers, and polymers, strongly affects ferrihydrite crystallinity, thermodynamic stability, and surface reactivity. How these silicate species bind on ferrihydrite surfaces is, however, not well understood. We have determined silicate binding geometries using a combination of X-ray absorption spectroscopy (XAS), differential atomic pair distribution function (d-PDF) analysis, and density functional theory (DFT) calculations. Silicon K-edge absorption pre edges and DFT-predicted energies indicate that silicate forms monomeric monodentate mononuclear (MM) complexes at low silicate sorption loadings. With increasing silicate loading, the pre-edge peak shifts to higher energies, suggesting changes in the silicate binding geometry toward multidentate complexation. The d-PDF analysis determines the Si Fe interatomic distance to be 3.25 A for the high-loading samples. The DFT calculations indicate that such distance corresponds to an oligomer in the bidentate binuclear (BB) binding geometry. The transition of the silicate sorption geometry accompanied by polymerization can affect stability of ferrihydrite and its adsorption and redox reactivity and increase the degree of Si isotopic fractionation upon silicate sorption on Fe oxides. MM monomeric complexes and BB oligomeric complexes should be used for surface complexation models predicting silicate sorption on Fe oxide surfaces.
28.	Yeşilbaş, Merve, et al. (author) Cohesive vibrational and structural depiction of intercalated water in montmorillonite 2018 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 2:1, s. 38-47 Journal article (peer-reviewed)abstract The vibrational spectral profiles of Na- and Ca-montmorillonite (MMT) of controlled water layer populations (nW) was extracted by chemometric analysis of new Fourier transform infrared (FTIR) spectroscopy data and validated by mixed-layer modeling of previously published X-ray diffraction data. These efforts resolved FTIR spectral profiles of 0W, 1W, and 2W interlayers, which can now be used to explore the distinct hydration states of MMT. These spectral profiles reflect water populations organized around interlayer cations (Na+, Ca2+), interacting with siloxane groups of the basal face of the interlayer, and with other bound and “free” water molecules. This cohesive description of water-bearing clays provides the link needed to relate vibrational to structural attributes of these geochemically important materials.
29.	Yeşilbaş, Merve, et al. (author) Ice and cryosalt formation in saline microporous clay gels 2018 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 2:4, s. 314-319 Journal article (peer-reviewed)abstract Hydrated clay minerals that are common to Earth’s atmosphere and terrestrial and aquatic environments can form gels that host saline solutions. Using cryogenic electron microscopy and vibration spectroscopy, we show that saline gels of montmorillonite frozen at < −90 °C host elongated hexagonal ice (Ih) microcrystals embedded in a network of honeycomb micropores. Freezing segregates salts into walls of aggregated clay nanoparticles sharing face-to-face contacts. Above ∼ −50 °C, clay gels that are sufficiently dense (≫10 g/L) and flexible (Na-exchanged montmorillonite) also host the cryosalt mineral hydrohalite (NaCl·2H2O), either co-existing or entirely replacing Ih in the gels. Hydrohalite does not form in gels of low-density (<10 g/L) or rigid (Ca-exchange montmorillonite) clay particles. These results suggest that hydrohalite forms in expandable clay gels that are sufficiently dense and flexible to retain saline solutions within their walls, possibly through interparticle capillary and hydration forces. These forces effectively oppose water diffusion to growing ice microcrystals within micropores, thus prolonging the lifetime of hydrohalite within these hydrated clay gels. Our findings tie the fate of ice and cryosalt nucleation and growth to the water-retention capability of expandable clay gels.
30.	Yun, Jingwei, et al. (author) Effects of Inorganic Acids and Organic Solutes on the Ice Nucleating Ability and Surface Properties of Potassium-Rich Feldspar 2021 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 5:5, s. 1212-1222 Journal article (peer-reviewed)abstract Mineral dust particles can initiate the freezing of cloud droplets in the atmosphere. The freezing efficiency of these particles can, however, be strongly affected by solutes, such as inorganic acids, polyols, and carboxylic acids. Here, we report the effects of inorganic acids (HNO3 and HCl), polyols, and carboxylic acids at low concentrations on the ice nucleating ability of potassium-rich feldspar (K-rich feldspar) using the droplet freezing technique. The inorganic acids and carboxylic acids decreased the median freezing temperature of droplets containing K-rich feldspar by up to 7 °C, while the polyols had no significant effect on the median freezing temperature. For the inorganic acids and carboxylic acids, the median freezing temperature was a strong function of the pH of the droplets, with the median freezing temperature decreasing as the pH decreased. By examining the surface properties of K-rich feldspar exposed to different concentrations of HCl with cryogenic X-ray photoelectron spectroscopy, we show that the decrease in the ice nucleating ability of K-rich feldspar by the inorganic acids and carboxylic acids was likely caused by ion exchange (H3O+ with parent K+ in microcline) and the incongruent dissolution of Al with respect to Si at K-rich feldspar surfaces. The decrease in the ice nucleating ability of K-rich feldspar by the carboxylic acids only related to the pH of the droplets rather than the type of carboxylic acid and their expected binding mechanisms on K-rich feldspar. This study focuses on rare ice nucleating active sites (with an ice nucleating active site density of 10-600 cm-2) of the K-rich feldspar and short exposure times between the solutes and the K-rich feldspar. Further studies are needed to investigate more abundant ice nucleating active sites and longer exposure times, as well as K-rich feldspar samples from different sources.
31.	Yun, Jingwei, et al. (author) Surface Composition Dependence on the Ice Nucleating Ability of Potassium-Rich Feldspar 2020 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 4:6, s. 873-881 Journal article (peer-reviewed)abstract Mineral dust particles are one of the most abundant types of ice nucleating particles in the atmosphere. During atmospheric transport, these particles can be coated with water-soluble solutes, which can modify their ice nucleating ability. Although previous studies have shown that even low concentrations of water-soluble solutes can modify the ice nucleating properties of mineral dust particles, our understanding of this topic is far from complete. We examined the effects of a series of alkali metal nitrates at low concentrations (5 × 10–5 M to 5 × 10–3 M) on the surface composition and immersion freezing of potassium-rich feldspar (K-rich feldspar). Immersion freezing was investigated with the droplet freezing technique, and the surface composition was investigated with cryogenic X-ray photoelectron spectroscopy. K+ increased the median freezing temperature of the droplets, while the other alkali metal cations either had no effect or decreased the median freezing temperature. The changes in the median freezing temperature of the droplets due to the presence of nitrates followed the order K+ ≥ Li+ ≥ Na+ ≥ Rb+ ≥ Cs+ and, except for Cs+, were correlated to the K/Al ratio at the surface of K-rich feldspar. The K/Al ratio is possibly an indicator of the abundance of certain types of K-bearing microcline surfaces that drive the immersion freezing of K-rich feldspar, while Cs+ likely influences the immersion freezing of K-rich feldspar by an additional mechanism, possibly blocking ice nucleation sites by adsorption. Our work also shows that the cation charge density (charge density over the surface area of a single cation) is not a good predictor of the effects of cations on the immersion freezing of K-rich feldspar in our experiments.
32.	Zhong, Cheng, et al. (author) Temporal Changes in Microbial Community Composition and Geochemistry in Flowback and Produced Water from the Duvernay Formation 2019 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 3:6, s. 1047-1057 Journal article (peer-reviewed)abstract Microbial activity in flowback and produced water (FPW) may negatively influence shale oil and gas extraction. However, the impacts of using recycled produced water (RPW) for subsequent fracturing jobs are not well-understood. In this study, we compared time series of FPW samples from two horizontally fractured wells drilled into the Duvernay Formation in Alberta, Canada; well 1 used RPW in the makeup of the hydraulic fracturing fluid (HFF) whereas well 2 did not. 16S rRNA gene sequencing and live/dead cell enumeration were used to track microbial communities. Within 20 days of flowback, total dissolved solids in well 1 and well 2 increased from 5310 mg/L and 288 mg/L to over 150,000 mg/L, and FPW temperatures increased from 20 and 9 degrees C to 77 and 71 degrees C, respectively. Alkyl dimethyl benzyl ammonium chloride (biocide) in well 2 decreased from 25 mu g/L to below the detection limit of 0.5 mu g/L. Cellular biomass decreased from similar to 10(5) cells mL(-1) to less than the detection limit of 10(5) cells mL(-1) in both wells, and the community in the samples was initially diverse but rapidly shifted to become dominated by the sulfidogenic lineage Halanaerobium. Methanogens were detected at low relative abundance within archaea, with DNA concentrations in FPW after 20 days inadequate for sequencing. Comparing the two wells, the start time of Halanaerobium enrichment was considerably shortened in well 1 relative to well 2. Our results suggest that subsurface environmental parameters primarily drive the rapid enrichment of sulfidogenic and halotolerant bacteria and current recycling strategies can facilitate the growth of these bacteria, whereas biocide seems to be a less important factor in this shift.
33.	Ångström, Jonas, et al. (author) Formation of Hydrous, Pyroxene-Related Phases from LiAlSiO4 Glass in High-Pressure Hydrothermal Environments 2019 In: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 3:1, s. 8-16 Journal article (peer-reviewed)abstract Hydrous Al-bearing pyroxene-related phases were synthesized by subjecting LiAlSiO4 glass to hydrothermal environments at pressures of 5-10 GPa and temperatures of 400-600 degrees C. LiAlSiO3(OH)(2) formed at 5 GPa, whereas at 10 GPa, product mixtures of LiAlSiO3(OH)(2) and Li3Al4(Si2O7)(SiO3)(2)(OH)(5) were obtained. The monoclinic structure of LiAlSiO3(OH)(2) has been previously characterized from single-crystal X-ray diffraction data (Spektor, K.; Fischer, A.; Haussermann, U. Crystallization of LiAlSiO4 Glass in Hydrothermal Environments at Gigapascal Pressures-Dense Hydrous Aluminosilicates. Inorg. Chem. 2016, 55 (16), 8048-8058, 10.1021/acs.inorgchem.6b01181). It resembles that of alpha-spodumene (LiAlSi2O6) and constitutes alternating layers of chains of corner-condensed SiO4 tetrahedra and chains of edge-sharing AlO6 octahedra. OH groups are part of the octahedral Al coordination and extend into channels provided within the SiO4 tetrahedron chain layers. The structure solution of Li3Al4(Si2O7)(SiO3)(2)(OH)(5), as detailed here, was achieved by rotational electron diffraction analysis, and the model was refined against synchrotron powder X-ray diffraction data (space group C2/c, a = 4.921 angstrom, b = 25.849 angstrom, c = 9.170 angstrom, and beta = 99.42 degrees). The crystal structure of Li3Al4(Si2O7)(SiO3)(2)(OH)(5) features chains and pairs of corner-condensed SiO4 tetrahedra, with the Si atoms equally distributed among the two structural units, and thus Li3Al4(Si2O7)(SiO3)(2)(OH)(5) is a rare example of a mixed inosorosilicate. LiAlSiO3(OH)(2) and Li3Al4(Si2O7)(SiO3)(2)(OH)(5) are structurally closely related to recently discovered hydrous magnesium aluminosilicate phases (i.e., HAPY and HySo), which form at conditions similar to the hydrous lithium aluminosilicates. The conjecture is made that hydrothermal environments following chlorite but also lawsonite breakdown generally afford conditions for the formation of hydrous, pyroxene-related, aluminosilicate phases, with compositions of M2(1-m)M1TO(3+n)(OH)(2-o) (0 < m, n, and o < 1). These phases could be transients in breakdown reactions but also stable at cold slab conditions and, thus, may play an important role to water storage and transport to the transition zone.

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