Huiming Bao's research while affiliated with Nanjing University and other places
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Publications (108)
Rationale
The oxygen isotope composition of phosphate (δ ¹⁸ O PO4 ) is widely employed for reconstructing paleotemperature and tracing biogeochemical phosphorus cycling. However, existing phosphate purification protocols do not work well for igneous rocks and igneous weathering profiles (IWPs). A reliable purification method is needed for measuring...
The largest negative inorganic carbon isotope excursion in Earth’s history, namely the Ediacaran Shuram Excursion (SE), closely followed by early animal radiation, has been widely interpreted as a consequence of oceanic oxidation. However, the primary nature of the signature, source of oxidants, and tempo of the event remain contested. Here, we sho...
Sulfate aerosols affect climate by scattering radiation and by changing the microphysical properties of water clouds. In much of the continental interiors that are overwhelmed by anthropogenic sulfate today, the nature of pre-industrial atmospheric sulfate remains pure speculation, which hampers our ability to quantify anthropogenic perturbation on...
Two cap carbonates overlying Cryogenian panglacial deposits are found in North‐East Svalbard of which the younger (635 Ma) forms the base of the Ediacaran Period. It is represented by a transgressive succession in which laminated dolostone, typically around 20 m thick (Member D1), is succeeded transitionally by a similar thickness of impure carbona...
Significance
Earth system’s response to major perturbations is of paramount interest. On the basis of multiple isotope compositions for pyrite, carbonate-associated sulfate, carbonates, and organics within, we inferred that the much-debated, enigmatic, extremely ¹³ C-depleted calcite cements in the ∼635-Ma cap carbonates in South China preserve geo...
Rationale When isotope composition is measured in dual-inlet mode with an isotope ratio mass spectrometer (IRMS), reference gas may be gradually enriched in heavy isotopes due to preferential loss of light ones from the bellow over time. Quantifying the degree of isotopic enrichment on the reference gas is imperative for high-precision isotopic ana...
Existing models for massively bedded barite (MBB) deposits (e.g., sedimentary exhalative and diagenetic/ cold-seep) satisfy some geological and geochemical observations, but none explain the Paleozoic clustering of MBB deposits in Earth history. Here we bring seawater redox history into the picture and propose a sulfate-limited euxinic seawater (SL...
Estimating Helium (He) concentration and isotope composition of the mantle requires quantifying He loss during magma degassing. The knowledge of diffusional He isotope fractionation in silicate melts may be essential to constrain the He loss. Isotopic mass dependence of He diffusion can be empirically expressed as D3He/D4He = (4/3)^β, where D is th...
Riverine dissolved sulfate (SO42−) sulfur and oxygen isotope variations reflect their controls such as SO42− reduction and re-oxidation, and source mixing. However, unconstrained temporal variability of riverine SO42− isotope compositions due to short sampling durations may lead to mischaracterization of SO42− sources, particularly for the pyrite-d...
Silicate melts have served as transport agents in the chemical and thermal evolution of Earth. Molecular dynamics simulations based on a deep neural network potential trained by ab initio data show that the viscosity of MgSiO3 melt decreases with increasing pressure at low pressures (up to ∼6 GPa) before it starts to increase with further compressi...
It is often assumed that the carbon isotope composition (δ13C) of carbonate minerals records that of the dissolved inorganic carbon (DIC) species with insignificant disequilibrium effect. However, results from field observations and laboratory experiments have shown that the δ13C difference between calcite and solution can vary up to 3‰ even under...
Several hundred meteorites with a total mass of over 100 kg were collected as the Alatage Mountain (AM) strewn field located in the Kumtag desert, Xinjiang Province, China. Twelve AM meteorites were studied in this work. Petrography, mineralogy, bulk chemistry, bulk oxygen isotopic compositions, and light noble gas concentrations and isotopic compo...
Diffusional isotope fractionation has been widely used to explain lithium (Li) isotope variations in minerals and rocks. Isotopic mass dependence of Li diffusion can be empirically expressed as D(7Li )/D(6Li ) =(6/7)^β, where D is the diffusivity of a Li isotope. The knowledge about temperature and compositional dependence of the β factor which is...
![Fig. 3. The [PM 2.5 ] at different RH and SO 2 (concentration) ranges...](publication/347662764/figure/fig3/AS:986274546597892@1612157584466/The-PM-25-at-different-RH-and-SO-2-concentration-ranges-A-and-at-different-RH-and_Q320.jpg)
![Fig. 4. Effects of CDW on near-surface [PM 2.5 ] in the GZB. (A and B)...](publication/347662764/figure/fig4/AS:986274546610176@1612157584561/Effects-of-CDW-on-near-surface-PM-25-in-the-GZB-A-and-B-Diurnal-profiles-of_Q320.jpg)
Significance
Water vapor emitted from anthropogenic combustion for winter heating in northern China may exacerbate air pollution. This hypothesis is of considerable scientific and environmental interest. We conducted a multiyear sampling campaign of air vapor isotope compositions and associated atmospheric data from the city of Xi’an, located in an...
It is expected that information on the source, reaction
pathway, and reaction kinetics of an organic compound can be obtained from
its position-specific isotope compositions or intramolecular isotope
distribution (Intra-ID). To retrieve the information, we could use its
predicted equilibrium Intra-ID as a reference for understanding the observed
In...
Diffusional isotope fractionation occurs in geochemical processes (such as magma mixing, bubble growth, and crystal growth), even at magmatic temperatures. Isotopic mass dependence of diffusion is commonly expressed as (Di/Dj)=(mj/mi)^β, where Di and Dj are diffusion coefficients of two isotopes whose masses are mi and mj. How the dimensionless emp...
It is expected that information on the source, reaction pathway, and kinetics of an organic compound can be obtained from its position-specific isotope compositions or intramolecular isotope distribution (Intra-ID). To retrieve the information, we could use its equilibrium Intra-ID as a reference for understanding the observed Intra-IDs. Historical...
In the equatorial regions on Earth today, the seasonal cycle of the monthly mean surface air temperature is <10°C. However, deep (>1 m) sand wedges were found near the paleoequator in the Marinoan glaciogenic deposits at ~635 million years ago, indicating a large seasonal cycle (probably >30°C). Through numerical simulations, we show that the equat...
A predicted equilibrium intramolecular isotope distribution (Intra-ID) serves as a reference for measured position-specific (PS) isotope composition variation in an organic molecule. Equilibrium Intra-ID can be estimated from calculated reduced partition function ratios (RPFR or β factor), which are largely absent to date. For relatively small mole...
Understanding the origin of ocean island basalts (OIB) has important bearings on Earth’s deep mantle. Although it is widely accepted that subducted oceanic crust, as a consequence of plate tectonics, contributes material to OIB’s formation, its exact fraction in OIB’s mantle source remains ambiguous largely due to uncertainties associated with exis...
Methane has both biotic and abiotic origins, and the identification of its origins has important implications in understanding terrestrial processes as well as in searching for extraterrestrial life. Bulk stable isotope ratios (¹³C/¹²C and D/H) and multiply substituted isotopologues (¹³CH3D and ¹²CH2D2) have been used to distinguish methane's origi...
The Proterozoic Eon spans Earth's middle age during which many important transitions occurred. These transitions include the oxygenation of the atmosphere, emergence of eukaryotic organisms and growth of continents. Since the sulfur and oxygen cycles are intricately linked to most surface biogeochemical processes, these transitions should be record...
Sulfate-driven anaerobic oxidation of methane (SD-AOM) plays a critical role in regulating the global methane budget. Determination of the diagnostic triple isotope exponent θ33 (≡ln³³α/ln³⁴α) for SD-AOM can help to identify and quantify microbial sulfate reduction via SD-AOM in the environment. The history of Earth's surface redox conditions can...
A dual or multiple stable isotope relationships, e.g. a trajectory in a δ-δ (or δ'-δ') space, can be used to deduce the relationship of underlying diagnostic isotope fractionation factors (α) and therefore to reveal the mechanism of a reaction process. While temporal data sampled from a close-system can be treated by a Rayleigh Distillation model,...
We report a petrography, mineral chemistry, oxygen and chromium isotopic study of Grove Mountains (GRV) 020043 together with a subset of other acapulcoites and lodranites. GRV 020043 is a petrologic type 4 chondrite, with chondrules of diverse types and sizes, and is composed of low-Ca pyroxene (40 vol.%), olivine (24 vol.%), diopside (8 vol.%), pl...
The nitrate deposits of the Atacama Desert are unique when one considers that in most surface environments nitrate is produced or consumed by biological processes and is easily washed away by rain. Nitrate deposits have puzzled geologists since Charles Darwin's visit to the Atacama in 1835 and several hypotheses have been proposed to explain their...
Termination of the terminal Cryogenian Marinoan snowball Earth glaciation (~650-635 Ma) is associated with the worldwide deposition of a cap carbonate. Modeling studies suggest that, during and immediately following deglaciation, the ocean may have experienced a rapid rise in pH and physical stratification followed by oceanic overturn. Testing thes...
Isotope fractionation during the evaporation of silicate melt and condensation of vapor has been widely used to explain various isotope signals observed in lunar soils, cosmic spherules, calcium–aluminum-rich inclusions, and bulk compositions of planetary materials. During evaporation and condensation, the equilibrium isotope fractionation factor (...
![Compiled pCO2\documentclass[12pt]{minimal} \usepackage{amsmath}...](profile/Galen-Halverson/publication/326466578/figure/fig2/AS:731590242091052@1551436114577/Compiled-pCO2documentclass12ptminimal-usepackageamsmath-usepackagewasysym_Q320.jpg)
The global biosphere is commonly assumed to have been less productive before the rise of complex eukaryotic ecosystems than it is today1. However, direct evidence for this assertion is lacking. Here we present triple oxygen isotope measurements (∆17O) from sedimentary sulfates from the Sibley basin (Ontario, Canada) dated to about 1.4 billion years...
The field of isotope geochemistry began with the study of oxygen isotope geothermometry, most notably for carbonates. For traditional oxygen isotope geothermometry only the relationship between one rare isotope, oxygen-18, and the common isotope, oxygen-16, is used because for most terrestrial processes the ¹⁷O-¹⁶O relationship scales with the ¹⁸O-...
Riverine dissolved sulfate (SO4²⁻) sulfur and oxygen isotope variations reflect their controls such as SO4²⁻ reduction and re-oxidation, and source mixing. However, unconstrained temporal variability of riverine SO4²⁻ isotope compositions due to short sampling durations may lead to mischaracterization of SO4²⁻ sources, particularly for the pyrite-d...
The Atacama Desert’s hyper-aridity is closely linked to the development of world-class copper and nitrate/iodine ores and to regional tectonics and global paleoclimate changes in the Cenozoic era. The timing when the hyper-aridity commenced remains controversial, with proposed ages ranging from Late Oligocene to Pleistocene. In this study, we provi...
Rationale:
Although being out of equilibrium, biomolecules in organisms have the potential to approach isotope equilibrium locally because enzymatic reactions are intrinsically reversible. A rigorous approach that can describe isotope distribution among biomolecules and their apparent deviation from equilibrium state is lacking, however.
Methods:...
The equilibrium isotope fractionation factor αeq is a fundamental parameter in the study of stable isotope effects. Experimentally, it has been difficult to establish that a system has attained equilibrium. The three-isotope method, using the initial trajectory of changing isotope ratios (e.g. ¹⁶O, ¹⁷O, and ¹⁸O) to deduce the final equilibrium poin...
Due to the adverse impact of DDTs on ecosystems and humans, a full fate assessment deems a comprehensive study on their occurrence in soils over a large region. Through a sampling campaign across China, we measured the concentrations, enantiomeric fractions (EFs), compound-specific carbon isotope composition of DDT and its metabolites, and the micr...
Sulfate-driven anaerobic oxidation of methane (SD-AOM) supports chemosynthesis-based communities and limits the release of methane from marine sediments. Formation of authigenic carbonates at active methane seeps is promoted by SD-AOM stoichiometry. While distinctively small d 18 O/d 34 S slopes of pore fluid sulfate have been shown to typify moder...
The element oxygen has three stable isotopes: 16O, 17O, and 18O. For a defined process, a change in 18O16O scales with the corresponding change in 17O16O, or the fractionation factors 18α and 17α have a relationship of θ = ln17αln18α, in which the triple oxygen isotope exponent θ is relatively fixed but does vary with reaction path, temperature, an...
Non-traditional stable isotopes have increasingly been applied to studies of igneous processes including planetary differentiation. Equilibrium isotope fractionation of these elements in silicates is expected to be negligible at magmatic temperatures (δ57Fe difference often less than 0.2 per mil). However, an increasing number of data has revealed...
Small differences in triple isotope relationships, or Δ¹⁷O in the case of oxygen, have been increasingly used to study a range of problems including hydrological cycles, stratosphere-troposphere exchange, biogeochemical pathways and fluxes, and the Moon’s origin in the geochemical and cosmochemical communities. A Δ¹⁷O value depends on the triple is...
The Marinoan panglaciation (ca 650 to 635 Ma) is represented in north-east Svalbard by the 130 to 175 m thick Wilsonbreen Formation which contains syn-glacial carbonates in its upper 100 m. These sediments are now known to have been deposited under a CO2-rich atmosphere, late in the glaciation, and global climate models facilitate testing of propos...
Two global glaciations occurred during the Neoproterozoic. Snowball Earth theory posits that these were terminated after millions of years of frigidity when initial warming from rising atmospheric CO2concentrations was amplified by the reduction of ice cover and hence a reduction in planetary albedo. This scenario implies that most of the geologica...
The Antarctic ice cap significantly affects global ocean circulation and climate. Continental glaciogenic sedimentary deposits provide direct physical evidence of the glacial history of the Antarctic interior, but these data are sparse. Here we investigate a new indicator of ice sheet evolution: sulfates within the glaciogenic deposits from the Lew...
Ceria (CeO2) is a heavily studied material in catalytic chemistry for use as an oxygen storage medium, oxygen partial pressure regulator, fuel additive, and for the production of syngas, among other applications. Ceria powders are readily reduced and lose structural oxygen when subjected to low pO2 and/or high temperature conditions. Such dis-stoic...
Building upon fine particulate matter (PM2.5) data and the accompanying meteorological conditions in the fall of 2013, Guo et al. (1) conclude that local aerosol nucleation and growth dominantly contributed to severe haze in Beijing, whereas regional transport of PM2.5 played an “insignificant” role. Guo et al.’s conclusion is surprising because it...
Riverine dissolved sulfate (SO4(2-)) flux and sulfur stable isotope composition (δ(34)S) yield information on the sources and processes affecting surface sulfur cycling on different spatial and temporal scales. However, because pristine pre-industrial natural baselines of riverine SO4(2-) flux and δ(34)S cannot be directly measured, anthropogenic i...
The stable isotope composition of O2, O3, and H2O in the geological past conveys rich information on history of the Earth system. However, few compounds are known to record O2 or O3 isotope signals directly and reliably. Sulfate (SO42 −), a non-labile oxyanion capable of forming weakly soluble minerals, plays important roles in global sulfur, carbo...
The isotope composition of seawater sulfate is an important tracer of sulfur, carbon, and oxygen cycles in Earth’s deep past. Carbonate-associated sulfate (CAS) extracted by acid digestion is widely used as a proxy for sulfate in paleo-seawater from which the carbonate minerals precipitated. Early and late diagenesis, weathering, and laboratory pro...
A large perturbation in atmospheric CO2 and O2 or bioproductivity will result in a drastic pulse of (17)O change in atmospheric O2, as seen in the Marinoan Oxygen-17 Depletion (MOSD) event in the immediate aftermath of a global deglaciation 635 Mya. The exact nature of the perturbation, however, is debated. Here we constructed a coupled, four-box,...
The ∼635 Ma Marinoan glaciation is marked by dramatic Earth system perturbations. Deposition of nonmass-dependently (17)O-depleted sulfate (SO(4)(2-)) in worldwide postglacial sediments is, thus far, unique to this glaciation. It is proposed that an extremely high-pCO(2) atmosphere can result in highly (17)O-depleted atmospheric O(2), or the Marino...
We have recently reported non-mass-dependent 17O depletion in sulfate deposited after the Marinoan glacial meltdown at ca. 635 million years ago. Further investigation linking the Δ17O of barite to its sedimentological-geological context in Marinoan South China reveals that the 17O depletion in sulfate is most pronounced at sites near paleo-contine...
In both laboratory experiments and natural environments where microbial dissimilatory sulfate reduction (MDSR) occurs in a closed system, the ((³⁴S/³²S)sample/(³⁴S/³²S)standard − 1) for dissolved SO4²⁻ has been found to follow a typical Rayleigh-Distillation path. In contrast, the corresponding ((¹⁸O/¹⁶O)sample/(¹⁸O/¹⁶O)standard) − 1) is seen to pl...
Large-scale nitrate deposits are rare on Earth's surface due to the high solubility of nitrate minerals. Exceptions are found in extremely old (to 14 m.y.) and hyperarid deserts such as the Atacama Desert in northern Chile, or the McMurdo Dry Valleys in Antarctica. The nitrate in both of these regions has been determined to originate from atmospher...
The Grove Mountains (GRV) 021663 meteorite was collected from the Grove Mountains region of Antarctica. The meteorite is composed primarily of olivine (Fa 5.4), orthopyroxene (Fs 4.7 Wo 3.0), chromian diopside (En 53.6 Fs 2.4 Wo 44), troilite, kamacite, and plagioclase (Ab 74.5 Or 4 An 21.5). Minor phases include schreibersite and K-feldspar. The m...
Distinct, non-mass-dependent 17O depletion was reported in barite from Marinoan cap dolostones (~ 635 Ma) in South China, and has been interpreted as an indication of an extremely high-pCO2 atmosphere (Bao et al., 2008). There is a significant variation in the magnitude of the 17O anomaly even among samples from the same outcrops. Understanding the...
Aqueous oxidation of sulfide minerals to sulfate is an integral part of the global sulfur and oxygen cycles. The current model for pyrite oxidation emphasizes the role of Fe2+–Fe3+ electron shuttling and repeated nucleophilic attack by water molecules on sulfur. Previous δ18O-labeled experiments show that a variable fraction (0–60%) of the oxygen i...
Isotope fractionation resulting from gas diffusion along a thermal gradient has always been considered entirely mass-dependent. A previous report, however, showed that non-mass-dependent (17)O anomalies can be generated simply by subjecting O(2) gas in an enclosure to a thermal gradient. To explore the underlying mechanism for the anomalies, we tes...
In order to understand spatial variations of stable isotope geochemistry in the Quruqtagh basin (northwestern China) in the aftermath of an Ediacaran glaciation, we analyzed carbonate carbon isotopes (δ13Ccarb), carbonate oxygen isotopes (δ18Ocarb), carbonate associated sulfate sulfur (δ34SCAS) and oxygen isotopes (δ18OCAS), and pyrite sulfur isoto...
Cryogenic or heating methods have been widely used in experiments involving gas purification or isolation and in studying phase changes among solids, liquids, or gases for more than a century. Thermal gradients are often present in these routine processes. While stable isotopes of an element are known to fractionate under a thermal gradient, the la...
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Volcanic eruptions release a large amount of sulphur dioxide (SO(2)) into the atmosphere. SO(2) is oxidized to sulphate and can subsequently form sulphate aerosol, which can affect the Earth's radiation balance, biologic productivity and high-altitude ozone concentrations, as is evident from recent volcanic eruptions. SO(2) oxidation can occur via...
The oxygen isotope composition of terrestrial sulfate is affected measurably by many Earth-surface processes. During the Neoproterozoic, severe "snowball" glaciations would have had an extreme impact on the biosphere and the atmosphere. Here, we report that sulfate extracted from carbonate lenses within a Neoproterozoic glacial diamictite suite fro...
Acritarchs from the Chuanlinggou Formation (ca. 1700Ma) were first reported by Xing and Liu (1973) [Xing, Y.S., Liu, G.Z., 1973. On Sinian micro-flora in Yenliao Region of China and its geological significance. Acta Geological Sinica 1, 1–64] and some were later described as eukaryotes by Yan (1982) [Yan, Y.Z., 1982. Schizofusa from the Chuanlinggo...
Understanding the composition of the atmosphere over geological time is critical to understanding the history of the Earth system, as the atmosphere is closely linked to the lithosphere, hydrosphere and biosphere. Although much of the history of the lithosphere and hydrosphere is contained in rock and mineral records, corresponding information abou...
Philippot et al. (Reports, 14 September 2007, p. 1534) interpreted multiple–sulfur isotopic compositions of ∼3.5-billion-year-old marine
sulfide deposits as evidence that early Archaean microorganisms were not sulfate reducers but instead metabolized elemental
sulfur. However, their data can be better explained by a scenario involving poor mixing o...
1] Sulfate, nitrate, and chloride are major water-soluble anions in soils of the McMurdo Dry Valleys (MDV), Antarctica. We measured the chloride stable isotope composition of 40 soil samples from 16 different soil profiles. The soil profiles come from three different microclimate zones in the MDV: a coastal thaw zone, which fosters a seasonally sat...
To improve our knowledge about the geochemical and environmental aftermath of Neoproterozoic global glaciations, we analyzed stable isotopes (δ13C, δ18O, δ34S) and elemental concentrations (Ca, Mg, S, Sr, Fe, and Mn) of the ∼ 10-m-thick Zhamoketi cap dolostone atop the Tereeken diamictite in the Quruqtagh area, eastern Chinese Tianshan. Available c...
The discovery of 33S anomalies in Archean sedimentary rocks has established that the early Earth before ∼2.2Ga (billion years ago) had a very different sulfur cycle than today. The origin of the anomalies and the nature of early sulfur cycle are, however, poorly known and debated. In this study, we analyzed the total sulfur and oxygen isotope compo...
Abundant graphite particles occur in amphibolite-grade quartzite of the Archean-Paleoproterozoic Wutai Metamorphic Complex in the Wutaishan area of North China. Petrographic thin section observations suggest that the graphite particles occur within and between quartzite clasts and are heterogeneous in origin. Using HF maceration techniques, the Wut...
This study investigates the sulfur and oxygen isotope fractionations of dissimilatory sulfate reduction and works to recon-cile the relationships between the oxygen and sulfur isotopic and elemental systems. We report results of experiments with natural populations of sulfate-reducing bacteria using sediment and seawater from a marine lagoon at Fll...
1] Many soils of the McMurdo Dry Valleys (MDV), Antarctica, being old, hyperarid, and frigid, have accumulated abundant atmospheric salts over the last several million years. This salt repository offers an opportunity to study atmospheric chemistry (past and present), the origin and transport of ions in soils, the weathering activity of soils, and...
Secondary atmospheric sulfates (SAS) is the ultimate oxidation product and sink for sulfur gases of biological, volcanic, and anthropogenic origins on Earth. Their presence in the atmosphere as aqueous or solid phases contributes to acid rain and climate change, thus, understanding SAS formation pathways is pertinent. There has been extensive measu...
Recent studies demonstrate that important information on sulfur source, oxidation pathway, transport pattern, and reaction kinetics of atmospheric oxidation of sulfur gases can be uncovered by measuring multiple isotope compositions of the oxidation product - secondary atmospheric sulfate (SAS). SAS from Earth's distant past, however, is rarely pre...
In the laboratory, barite precipitated from a solution with a high nitrate/sulfate ratio can have a significant amount (up to 28% by weight) of nitrate occluded in barite crystals that cannot be simply washed away. The impurity poses a serious problem for an accurate measurement of the oxygen isotope compositions for atmospheric sulfate, since atmo...
