Role Of H2O Research Articles

In–depth understanding on the mechanism of ionic liquid-assisted enhancement of electrochemical CO2 reduction to formic acid

Although extensive research has been conducted on the electrochemical CO2 reduction reaction (CO2RR) using ionic liquid (IL) + acetonitrile and ILs + acetonitrile + H2O systems, it is a challenge to explain why ILs facilitate electrochemical CO2 reduction and why different ILs exhibit varying catalytic effects. In this paper, we utilized commercially available copper electrodes as the working electrode and employed three ILs (i.e., 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), and 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([BMIM][Tf2N])) as one of the additive components of electrolytes for electrochemical CO2RR. The relationship between the performance of electrochemical CO2RR to formic acid (FA) and different IL structures in binary and ternary systems was investigated through experiments. The mechanism of performance of electrochemical CO2RR to FA enhanced by ILs in the binary systems was explored at the molecular level through density functional theory (DFT) calculations. Furthermore, the role of H2O was elucidated in the ternary IL + acetonitrile + H2O system.

Role of H2O in Catalytic Conversion of C1 Molecules.

Due to their role in controlling global climate change, the selective conversion of C1 molecules such as CH4, CO, and CO2 has attracted widespread attention. Typically, H2O competes with the reactant molecules to adsorb on the active sites and therefore inhibits the reaction or causes catalyst deactivation. However, H2O can also participate in the catalytic conversion of C1 molecules as a reactant or a promoter. Herein, we provide a perspective on recent progress in the mechanistic studies of H2O-mediated conversion of C1 molecules. We aim to provide an in-depth and systematic understanding of H2O as a promoter, a proton-transfer agent, an oxidant, a direct source of hydrogen or oxygen, and its influence on the catalytic activity, selectivity, and stability. We also summarize strategies for modifying catalysts or catalytic microenvironments by chemical or physical means to optimize the positive effects and minimize the negative effects of H2O on the reactions of C1 molecules. Finally, we discuss challenges and opportunities in catalyst design, characterization techniques, and theoretical modeling of the H2O-mediated catalytic conversion of C1 molecules.

Influence of Soot Particles on the Gas-Phase Methane Conversion into Synthesis Gas: The Role of H2O and CO2 Additives

Influence of Soot Particles on the Gas-Phase Methane Conversion into Synthesis Gas: The Role of H2O and CO2 Additives

Stabilizing Co2C with H2O and K promoter for CO2 hydrogenation to C2+ hydrocarbons.

The decomposition of cobalt carbide (Co2C) to metallic cobalt in CO2 hydrogenation results in a notable drop in the selectivity of valued C2+ products, and the stabilization of Co2C remains a grand challenge. Here, we report an in situ synthesized K-Co2C catalyst, and the selectivity of C2+ hydrocarbons in CO2 hydrogenation achieves 67.3% at 300°C, 3.0 MPa. Experimental and theoretical results elucidate that CoO transforms to Co2C in the reaction, while the stabilization of Co2C is dependent on the reaction atmosphere and the K promoter. During the carburization, the K promoter and H2O jointly assist in the formation of surface C* species via the carboxylate intermediate, while the adsorption of C* on CoO is enhanced by the K promoter. The lifetime of the K-Co2C is further prolonged from 35 hours to over 200 hours by co-feeding H2O. This work provides a fundamental understanding toward the role of H2O in Co2C chemistry, as well as the potential of extending its application in other reactions.

The role of H2O on metamorphism and deformation at high pressure: A combined petrological and thermo-mechanical study based on the Gran Paradiso Unit, Western Alps

The role of H2O on metamorphism and deformation at high pressure: A combined petrological and thermo-mechanical study based on the Gran Paradiso Unit, Western Alps

Physical and chemical effects of H2O on mineral carbonation reactions in supercritical CO2

Mineral carbonation through reaction with supercritical CO2 (scCO2) is the ultimate pathway to permanent carbon storage for geological sequestration. Whether and how much H2O is required for the scCO2-mineral interaction to proceed readily, and the role of H2O in the reaction have been actively researched topics. We designed and built a novel in situ Raman reactor to study the carbonation product during brucite [Mg(OH)2]-scCO2 interaction, and investigated the role of free H2O by comparing the products in neat, H2O, and formamide (FM) conditions. We introduced FM to provide a physical polarity environment similar to that of H2O but without the chemical protonation effect. We further evaluated the role of structural H2O by conducting experiments with periclase (MgO). The in situ Raman analysis revealed the occurrence of brucite carbonation both in the presence of H2O and FM, demonstrating the effect of polarity in the reaction; in contrast, carbonation of periclase only occurred in H2O-saturated scCO2. The lack of carbonation of periclase with the presence of FM was attributed to the difficulty of magnesite mineralization, as CaCO3 was able to form in the CaO-FM-scCO2 system. Post-experimental X-ray diffractometry and Fourier-transform infrared spectrometry of the products showed that brucite carbonation yielded nesquehonite and hydromagnesite in H2O and FM, respectively; whereas periclase-scCO2 interaction in H2O produced a mixture of the two products. Rate calculations suggested that the carbonation reaction was much faster in H2O; nonetheless, 40–50% carbonation was still achieved in the Mg(OH)2-FM-scCO2 system after 330 h. Overall, our results showed that the brucite-scCO2 reaction could proceed without H2O under certain conditions – the polarity effect of H2O/FM was large enough to break the Mg–OH and MgO–H bonds and promote the carbonation process.

Estimation of third body efficiencies from experimental data: Application to hydrogen combustion

In this work, the role of H2O and CO2 as diluents is investigated, in operating conditions relevant to MILD combustion of hydrogen. Through virtual species analysis, the role of third body collisions emerges in phenomena such as ignition and speciation. Global sensitivity analysis shows that a single third body efficiency exhibits a larger impact than a group of sensitive reactions. For fall-off reactions, the adoption of a PLOG format, rather than a classical TROE can introduce errors as high as 2000% on macroscopic combustion targets due to the absence of key collision efficiencies. Heuristic optimization methods in OptiSMOKE++ provide best estimates and confidence regions for the third body efficiencies of H2O and CO2 in H+O2(+M)⇋HO2(+M) and H2O2(+M)⇋2OH(+M) in TROE formulation. Eventually, a method to extract this information using the PLOG formulation is proposed. This approach is applicable to other reactions in case theoretical calculations are unavailable or difficult to perform.

A density model for high-pressure carbonate-rich melts applied to carbonatitic magmatism in the upper mantle

Carbonatitic melts (<15 wt% SiO2) are widespread in the Earth's upper mantle and major conveyors of trace and volatile elements. Their migration through the mantle thus shapes the deep volatiles cycle and modifies its geochemical and geophysical signatures. Quantitative modelling of these processes has long been limited by the lack of continuous, predictive models for the physical properties of carbonate-rich melts, namely the density and viscosity, over a broad pressure-temperature-composition (P-T-X) range. Here we present a continuous model for the density of carbonate-rich melts in the system MgO-CaO-Na2O-K2O-Li2O-H2O-CO2 based on data compiled from the literature, including recent high pressure experimental and theoretical results. The model is calibrated on an extensive database of more than 880 data points over a temperature range of 800–2300 K and pressures from 10−4 GPa to 30 GPa, i.e. spanning most conditions of interest for the crust, upper mantle and transition zone. We have adopted a simple, volume-explicit Murnaghan EOS to describe the volumetric properties of each oxide component using 5 adjustable parameters optimized over the entire database and assume linear mixing in volume between the different oxide components in the calibration interval. The density model reproduces the calibration dataset with an average residual of ±0.05 g cm−3 and predicts densities with an average relative error of ±2%. Used in conjunction with reasonable constraints on the volumetric properties of SiO2 and FeO, the model permits density and seismic P-wave velocity VP predictions for complex carbonatitic melts experimentally equilibrated with various mantle lithologies (e.g. peridotite, eclogite, pelite). Our calculations demonstrate the first-order role of pressure by increasing both density and VP, with only a secondary role ascribed to temperature and composition. The role of H2O is contrasted and concealed by the interplay between the P-T-X conditions for the few experimental data available. Our predictions also show that both density and VP contrasts between carbonatitic melts and the host solid mantle diminish with depth, which implies larger effect of carbonate-rich melts on the seismic velocity signature of the Earth's upper mantle at shallower depths. Lastly, we pinpoint that carbonate melts are seismically faster than silicate melts, which together with their higher electrical conductivity, are promising diagnostic features to identify molten phases at depth and to discriminate between carbonate and silicate melts in the Earth's upper mantle using geophysical observations.

Understanding the temperature-dependent H2O promotion effect on SO2 resistance of MnOx-CeO2 catalyst for SCR denitration

Understanding how H2O affects SO2 tolerance of SCR catalysts at different working temperatures is of great importance. Herein, we reported that H2O addition at ultra-low temperature of 100 °C induced a significant promotion on SO2 tolerance of MnOx-CeO2 catalysts. Sole SO2 led to serious activity loss from 100% to 20%, while H2O coexistence alleviated the deactivation and an admirable activity of 60% was reserved. Combining experimental characterizations with DFT calculation, we demonstrated that H2O promoted hydroxyl formed on defect sites, which promoted more sulfite formation and retarded sulfates with strong electron-withdrawing capacity disturbing active Mn sites. In comparison with sulfates, sulfites exhibited less interference in adsorbed species, ensuring the occurrence of Eley-Rideal and Langmuir-Hinshelwood mechanisms. The present study discloses the unique temperature-dependent effect of H2O on SO2 tolerance, which is expected to deepen our understanding on the role of H2O in modulating surface species and catalytic behaviors of SCR catalysts.

Development of major element proxies for magmatic H2O content in oceanic basalts

Analysis of H2O concentrations in quenched glass has enabled significant improvements in our understanding of its role in mantle melting, magma differentiation, eruption dynamics, and the origin of mantle heterogeneity. Direct measurements of dissolved H2O in glass, however, are not always possible, and we lack robust methods of constraining magmatic H2O contents in aphyric, bulk rock samples that lack glass. Here, we present a major element hygrometer for mid-ocean ridge (MOR) and back-arc basin (BAB) basalt magmas based on the sensitivity of phenocryst phase assemblages to magmatic H2O contents, which translate into resolvable differences in liquid lines of descent (LLDs) as a function of magmatic H2O concentrations. Existing hygrometers lack sufficient resolution to be useful at the low H2O concentrations typical of MOR and BAB basalts (<1.0 wt%). We develop the major element proxy, Al2O3/FeO*(7.0) (fractionation-corrected to 7 wt% MgO), for determining magmatic H2O contents using cogenetic suites of oceanic basalts with well-defined LLDs and well-constrained H2O contents. H2O(7.0) positively correlates with Al2O3/FeO*(7.0) in the mid-ocean ridge basalt dataset, and this relationship is maintained in back-arc basin basalts with a broader range of water contents (up to 2.0 wt%). The main petrological control over this covariation is the role of H2O in suppressing plagioclase crystallization, while crystallization pressure and magmatic oxygen fugacity play lesser roles. Herein, we present an empirical model that uses Al2O3/FeO*(7.0) to estimate the magmatic water content in plagioclase-saturated oceanic basaltic magmas: H2O(7.0) = 1.109Al2O3/FeO∗(7.0) − 1.111. This model enables the estimation of magmatic H2O content using whole-rock major element data, which can be readily determined for aphyric or crystalline lavas that lack quenched glassy rinds, melt inclusions, or appropriate phenocryst assemblages.

Non-classical major histocompatibility factor H2-O counteracts gammaherpesvirus manipulation of the germinal center response

Abstract Gammaherpesviruses, such as Epstein Barr virus, infect 95% of adults and form lifelong infection primarily through manipulation of B cells. During primary infection, gammaherpesviruses establish latent infections within B cells and drive robust, polyclonal germinal center (GC) responses, which atypically include B cells specific to both viral and self antigens. Consequently, this humoral response results in production of both autoantibodies, and interestingly, antibodies reactive to antigens of non-human species. While this non-physiological production of antibodies suggests viral manipulation of immune tolerance, the underlying mechanisms driving these phenomena are poorly understood. Utilizing murine gammaherpesvirus 68 (MHV68), a rodent pathogen highly similar to EBV which serves as an animal model of EBV infection, we have discovered that the host factor H2-O (HLA-DO in humans) attenuates MHV68 latency establishment and the MHV68 driven GC response. H2-O acts as an inhibitor of H2-M (HLA-DM), the protein which regulates peptide exchange and thus the repertoire of peptides associated with the MHC-II peptide binding groove. We found that mice deficient in H2-O displayed increased MHV68 latent reservoirs, increased GC response, and a selective increase in dsDNA specific IgG, with no change in virus specific IgG at the peak of latent viral infection. These results show a novel role of H2-O in attenuating the non-physiological, self-directed B cell response driven by MHV68. Furthermore, these studies are the first to demonstrate that fine tuning of MHC-II antigen presentation is sufficient to alter the self-directed B cell differentiation usurped by a ubiquitous viral pathogen during establishment of life-long infection.

The role of H2O in NO formation and reduction during oxy-steam combustion of bituminous coal char

To improve the CO2 capture efficiency and reduce energy penalties in conventional oxy-fuel combustion systems, one possibility is to eliminate the use of recycled flue gas, by using steam and O2. This is known as oxy-steam combustion. However, the role of H2O in NO formation and reduction under oxy-steam combustion is not yet clear. Here, NO emissions during oxy-steam and air combustion of coal char were compared using both experiments and theoretical calculations, with an emphasis of the role of H2O and its resulting radicals in NO formation and reduction reactions. High concentration of H2O promotes both OH radicals and hydroxyl groups formation during oxy-steam combustion, which in turn effects NO formation and reduction reactions and eventually NO emissions. Specifically, NO formation under air combustion is largely determined by HCN conversion to NCO and then NO, whereas under oxy-steam combustion, high concentrations of OH radicals cause HCN to form NH2 and eventually NO as the dominant route. However, the conversion of HCN to NH2 and then NO is faster, and hence these OH radicals accelerate HCN oxidation to NO under oxy-steam combustion. Given that OH radicals and hydroxyl groups have little influence on NO reduction to N2, there is more NO production in oxy-steam combustion that air combustion.

The role of H2O in structural nitrogen migration during coal devolatilization under oxy-steam combustion conditions

Oxy-steam combustion is a promising technology for reducing CO2 emissions. During coal devolatilization under oxy-steam condition, the high steam concentration has a considerable influence on the migration of structural nitrogen. In this paper, the transformation of nitrogenous functionalities and the release of nitrogen-containing precursors in N2 and N2/H2O atmospheres at 1173–1373 K were measured experimentally. Using density functional theory calculation, the reaction networks of nitrogen migration under N2 and N2/H2O conditions were established, with the corresponding thermodynamics data. On this basis, a detailed kinetics analysis was conducted. Results showed that compared to a N2 atmosphere, the char prepared in a N2/H2O atmosphere exhibits a lower content of pyridinic N and higher contents of quaternary and pyrrolic N. This is because high OH radical concentrations inhibit the transformation of N-Q to N-6. Moreover, the adsorption of OH on pyridinic N leads to the formation of 2-pyridone, thereby making the conversion of N-6 to N-5 feasible. Furthermore, the decomposition of both N-6 and N-5 leads to the formation of HCN, while N-5 is the major source of NH3. In this process, the presence of hydroxyl groups inhibit the release of HCN and NH3, leading to lower emissions under N2/H2O than N2 conditions.

Effects of O2 and H2O on TiO2 photocatalytic mass loss self-cleaning efficiency for thin hydrocarbons layers

The self-cleaning properties provided by photocatalytic reactions have raised a lot of interest for many applications. Nowadays, the widespread analysis methods to study photocatalytic self-cleaning comprise mainly indirect methods such as UV–VIS spectroscopy, chromatography or contact angles measurements. Quartz Crystal Microbalance is another appropriate way to study how the surface is decontaminated because it has the advantage to directly measure the reactant mass. In this study the latter was used to investigate various parameters such as mass loss kinetics, effect of photocatalyst or contaminant effective thicknesses, illumination flux … A special attention was paid to the effects of humidity and O2 on the photocatalytic removal of nanometric paraffin oil (hydrocarbons) films over TiO2. QCM measurements were carried out for several H2O and O2 relative contents in the exposure. Ultimately, water is not essential but acts as a reaction promoter while O2 tends to be essential without significantly affecting the photocatalytic rate provided it is present in sufficient amount. Considering these observations and potential degradation pathways of paraffin oil hydrocarbons, the role of H2O and O2 is discussed.

The role of H2O in the removal of methane mercaptan (CH3SH) on Cu/C-PAN catalyst

Methane mercaptan (CH3SH) is a common organic sulfur in smelting flue gas, which has significant harm to the environment, industrial production and human health. Therefore, research on the purification of CH3SH has received extensive attention. Herein, we focused on the role of H2O in the removal of CH3SH, and revealed that H2O promotes the adsorption of CH3SH at low temperature and promotes its hydrolysis at high temperature, which significantly improves the removal of CH3SH. In this study, the polyacrylonitrile-based activated carbon fiber was prepared by electrospinning, with the diameter of about 300~400 nm. Cu, Fe and Mn were loaded by impregnation method, and the CH3SH removal efficiency were compared. The combination of characterization results by HR-TEM, XRD, XPS, NH3-TPD and activity evaluation as well as DFT calculation results finally revealed the removal mechanism of CH3SH with the participation of H2O.

Real-Time In situ XRD Study of Simvastatin Crystallization in Levitated Droplets

Simvastatin (SV) is an important active pharmaceutical ingredient (API) for treatment of hyperlipidemias, which is known to exist in different crystalline and amorphous phases. It is, therefore, an interesting model to investigate how the outcome of evaporative crystallization in the contactless environment of an acoustically levitated droplet may be influenced by key experimental conditions, such as temperature, solvent properties (e.g., polarity and hygroscopicity), and dynamics of the evaporation process. Here, we describe a real-time and in situ study of simvastatin evaporative crystallization from droplets of three solvents that differ in volatility, polarity, and protic character (acetone, ethanol, and ethyl acetate). The droplet monitorization relied on synchrotron X-ray diffraction (XRD), Raman spectroscopy, imaging, and thermographic analysis. A pronounced solvent-dependent behavior was observed. In ethanol, a simvastatin amorphous gel-like material was produced, which showed no tendency for crystallization over time; in ethyl acetate, a glassy material was formed, which crystallized on storage over a two-week period to yield simvastatin form I; and in acetone, form I crystallized upon solvent evaporation without any evident presence of a stable amorphous intermediate. The XRD and Raman results further suggested that the persistent amorphous phase obtained from ethanol and the amorphous precrystallization intermediate formed in ethyl acetate were similar. Thermographic analysis indicated that the evaporation process was accompanied by a considerable temperature decrease of the droplet surface, whose magnitude and rate correlated with the solvent volatility (acetone > ethyl acetate > ethanol). The combined thermographic and XRD results also suggested that, as the cooling effect increased, so did the amount of residual water (most likely captured from the atmosphere) remaining in the droplet after the organic solvent was lost. Finally, the interpretation of the water fingerprint in the XRD time profiles was aided by molecular dynamics simulations, which also provided insights into the possible role of H2O as an antisolvent that facilitates simvastatin crystallization.

B isotopic constraints on the role of H2O in mantle wedge melting

The role of water on melting in the mantle wedge is still debated due to large uncertainty on the estimates of H2O flux beneath arcs. B has been proven as an effective proxy for water flux because B and H2O show similar chemical behaviors during subduction. The Habahe mafic dikes from the Chinese Altai were emplaced within a narrow area (<20 km from south to north) during the northward subduction of the Junggar Ocean in the middle Paleozoic. These dikes have been classified into four types with distinct geochemical and Sr-Nd-Hf-Pb isotopic compositions, which originated from mantle sources metasomatized by different subduction components, including melts from subducted sediments (Type-I, Type-IV), fluids from subducted sediments (Type-II), and melts from subducted oceanic crust (Type-III). We present B content and isotope data for the Habahe mafic dikes to investigate the influence of subduction components on melting in the mantle wedge. Type-I and -III mafic dikes all have negative δ11B values (−7.7‰ to −5.0‰) with variable B contents (3.65–13.4 ppm) and B/Nb ratios (2.10–7.39), indicating B isotopically light features for the subducted sediments and oceanic crust. Type-II mafic dikes have lower B contents (3.97–9.90 ppm) and higher B/Nb ratios (7.07–14.4) than Type-I mafic dikes, with a wide range of δ11B values from −7.8‰ to −2.7‰. This suggests that their mantle source may have been metasomatized by fluids from subducted serpentinite besides fluids from subducted sediments. Type-IV mafic dikes have higher B contents (17.0–27.5 ppm) and B/Nb ratios (25.0–40.8), and heavier B isotopic compositions (δ11B = −2.9‰ to +3.5‰) than Type-I mafic dikes. This indicates involvement of fluids from the slab serpentinite in metasomatism of their mantle source in addition to melts from the subducted sediments. The Habahe mafic dikes show wide range of B/Nb ratios, suggesting that different amounts of water were added into their mantle sources. These dikes exhibit variable Zr/Yb and Nb/Yb ratios, and constantly low TiO2/Yb, indicating their formation through different degrees melting of depleted mantle sources. Their Zr/Yb and Nb/Yb ratios are negatively correlated with B/Nb, which reflects elevation of the melting degree of their mantle sources as increasing water input. Similar trends are also observed in basalts from global arcs and their major and trace elements correlate well with B/Nb ratios. Thus, water flux should play an important role on melting in the mantle wedge and control magma compositions of the arcs.

Observation of a potential-dependent switch of water-oxidation mechanism on Co-oxide-based catalysts

Summary O–O bond formation is a key elementary step of the water-oxidation reaction. However, it is still unclear how the mechanism of O–O coupling depends on the applied electrode potential. Herein, using water-in-salt electrolytes, we systematically altered the water activity, which enabled us to probe the O–O bond-forming mechanism on heterogeneous Co-based catalysts as a function of applied potential. We discovered that the water-oxidation mechanism is sensitive to the applied potential: At relatively low driving force, the reaction proceeds through an intramolecular oxygen coupling mechanism, whereas the water nucleophilic attack mechanism prevails at high driving force. The observed mechanistic switch has major implications for the understanding and control of the water-oxidation reaction on heterogeneous catalysts.

3.Al-Based Metal-Organic Framework MFM-300 and MIL-160 for SO2 Capture: A Molecular Simulation Study

SO2 emission from fossil fuels combustion in the environment has led to various environmental and health hazards drawing the significant attention of the world to control. SO2 capture through metal-organic frameworks (MOFs) as adsorbent is a promising environmental technology to eliminate the emission of SO2. Many factors have been identified that influence the activity of SO2 separations for flue gases by MOFs, but the precise mechanisms of selectivity underlying the interactions between host and guest molecules are still unclear. Moreover, the role of H2O in flue gases needs to be considered since it is an essential factor in practical engineering applications. In this work, the MOFs of MIL-160 and MFM-300 are selected to capture SO2 from flue gases with various components, which have been experimentally demonstrated to have great feature in flue gas desulfurization. Force-field-based grand canonical Monte Carlo (GCMC) simulations combined with density functional theory (DFT) are employed to predict the strength of host/guest interactions and the adsorption isotherms for all guests in flue gas in MIL-160 and MFM-300. The results show that MIL-160 has an outstanding SO2/CO2 selectivity up to 220 (298 K, 1bar), compared to MFM-300 with 53. CO2 and SO2 binding furanyl groups in MIL-160 are stronger than binding hydroxyl groups in MFM-300. We also found that the increasing weakens the performance of SO2 capture due to the predominant H2O adsorption in the separation process.

MAGLAB: A computing platform connecting geophysical signatures to melting processes in Earth's mantle

Decompression melting of the upper mantle produces magmas and volcanism at the Earth's surface. Experimental petrology demonstrates that the presence of CO2 and H2O enhances peridotite melting anywhere within the upper mantle down to approximately 200–300 km depth. The presence of mantle melts with compositions ranging from carbonate-rich to silicate-rich unavoidably affects the geophysical signals retrieved from Earth's mantle. Geochemical investigations of erupted intraplate magmas along with geophysical surveys allow for constraining the nature and volume of primary melts, and a sound formalism is required to integrate these diverse datasets into a realistic model for the upper mantle including melting processes. Here, we introduce MAGLAB, a model developed to calculate the composition and volume fraction of melts in the upper mantle, together with the corresponding electrical conductivity of partially molten mantle peridotites at realistic pressure-temperature conditions and volatile contents. We use MAGLAB to show how the compositions of intraplate magmas relate to variations in lithosphere thickness. Progressive partial melting of a homogeneous peridotitic mantle source can in theory create the diversity of compositions observed among the spectrum of intraplate magma types, with kimberlite melts beneath thick continental shields, alkaline magmas such as melilitite, nephelinite and basanite beneath thinner continents and relatively old plus thick oceanic lithospheres, and ‘regular’ basalts beneath the youngest and thinnest oceanic lithospheres as well as beneath significantly thinned continental lithospheres. MAGLAB calculations support recent experimental findings about the role of H2O in the upper mantle on producing primary kimberlitic melts in addition to CO2. We demonstrate the robustness of MAGLAB calculations by reproducing the compositions of erupted melts as well as associated mantle electrical conductivities beneath the Society hotspot in the Pacific Ocean. A comparison of our simulations with magnetotelluric surveys at various oceanic settings shows that the heterogeneities in electrical conductivity of Earth's upper mantle are related to variations in volatile content via the presence of small (generally <<1 wt%) and heterogeneously distributed fractions of CO2-H2O-bearing melts.