Developing a cost-effective and environmentally friendly process for the production of valuable chemicals from abundant herbal biomass receives great attentions in recent years.Herein,taking advantage of the“lignin f...Developing a cost-effective and environmentally friendly process for the production of valuable chemicals from abundant herbal biomass receives great attentions in recent years.Herein,taking advantage of the“lignin first”strategy,corn straw is converted to valuable chemicals including lignin monomers,furfural and 5-methoxymethylfurfural via a two steps process.The key of this research lies in the development of a green and low-cost catalytic process utilizing magnetic Raney Ni catalyst and high boiling point ethylene glycol.The utilization of neat ethylene glycol as the sole slovent under atmospheric conditions obviates the need for additional additives,thereby facilitating the entire process to be conducted in glass flasks and rendering it highly convenient for scaling up.In the initial step,depolymerization of corn straw lignin resulted in a monomer yield of 18.1 wt%.Subsequently,in a dimethyl carbonate system,the carbohydrate component underwent complete conversion in a one-pot process,yielding furfural and 5-methoxymethylfurfural as the primary products with an impressive yield of 47.7%.展开更多
Prediction of production decline and evaluation of the adsorbed/free gas ratio are critical for determining the lifespan and production status of shale gas wells.Traditional production prediction methods have some sho...Prediction of production decline and evaluation of the adsorbed/free gas ratio are critical for determining the lifespan and production status of shale gas wells.Traditional production prediction methods have some shortcomings because of the low permeability and tightness of shale,complex gas flow behavior of multi-scale gas transport regions and multiple gas transport mechanism superpositions,and complex and variable production regimes of shale gas wells.Recent research has demonstrated the existence of a multi-stage isotope fractionation phenomenon during shale gas production,with the fractionation characteristics of each stage associated with the pore structure,gas in place(GIP),adsorption/desorption,and gas production process.This study presents a new approach for estimating shale gas well production and evaluating the adsorbed/free gas ratio throughout production using isotope fractionation techniques.A reservoir-scale carbon isotope fractionation(CIF)model applicable to the production process of shale gas wells was developed for the first time in this research.In contrast to the traditional model,this model improves production prediction accuracy by simultaneously fitting the gas production rate and δ^(13)C_(1) data and provides a new evaluation method of the adsorbed/free gas ratio during shale gas production.The results indicate that the diffusion and adsorption/desorption properties of rock,bottom-hole flowing pressure(BHP)of gas well,and multi-scale gas transport regions of the reservoir all affect isotope fractionation,with the diffusion and adsorption/desorption parameters of rock having the greatest effect on isotope fractionation being D∗/D,PL,VL,α,and others in that order.We effectively tested the universality of the four-stage isotope fractionation feature and revealed a unique isotope fractionation mechanism caused by the superimposed coupling of multi-scale gas transport regions during shale gas well production.Finally,we applied the established CIF model to a shale gas well in the Sichuan Basin,China,and calculated the estimated ultimate recovery(EUR)of the well to be 3.33×10^(8) m^(3);the adsorbed gas ratio during shale gas production was 1.65%,10.03%,and 23.44%in the first,fifth,and tenth years,respectively.The findings are significant for understanding the isotope fractionation mechanism during natural gas transport in complex systems and for formulating and optimizing unconventional natural gas development strategies.展开更多
Water-soluble organic matter(WSOM)significantly influences the transport of metals and organic contaminants in soils,yet the interaction specifics with antimony(Sb)remain largely unexplored.Antimony is of particular e...Water-soluble organic matter(WSOM)significantly influences the transport of metals and organic contaminants in soils,yet the interaction specifics with antimony(Sb)remain largely unexplored.Antimony is of particular environmental concern due to its toxic properties and harmful effects on ecosystems and human health.Employing a three-step fractionation method with polyvinylpyrrolidone(PVP),this study aimed to isolate and analyze humic acids(HA),PVP-non adsorbed fulvic acids(FAA),and PVP-adsorbed fulvic acids(FAB)from WSOM in soil spiked with Sb and incubated for 18 months.These fractions underwent chemical analysis for carbon(C),nitrogen(N),total organic carbon(TOC),and Sb,complemented by FTIR and 1H NMR spectroscopic characterization.The study revealed that HA wasmore aliphatic,with Sb predominantly associating with the fulvic acid(FA)fraction,accounting for 97%of Sb in extracts.Specifically,the FAA subfraction held substantial portions of total carbon(TC),total nitrogen(TN),total organic carbon(TOC),and Sb.Correlations between Sb concentrations and TN,TC,and TOC were significant.Extraction methods showed NaOH and Na_(4)P_(2)O_(7) outperformed HCl and deionised water in extracting TC,TN,and TOC,with higher Sb concentrations found in Na_(4)P_(2)O_(7) and NaOH extracts.This underscores the role of Fe/Al-SOM complexes in Sb soil availability.The results revealed that FAA subfraction accounted for 76%,64%and 94%of TN,TOC and Sb,respectively.Therefore,this research highlights the FAA fraction’s central role,predominantly comprising non-humic substances like amines,in the availability of C,N,and Sb in Sb-impacted soils.The findings offer insights for environmental management and remediation strategies.展开更多
Based on geochemical data from natural gas samples across spring water systems and sedimentary basins,including Songliao,Bohai Bay,Sanshui,Sichuan,Ordos,Tarim and Ying-Qiong,this paper systematically compares the geoc...Based on geochemical data from natural gas samples across spring water systems and sedimentary basins,including Songliao,Bohai Bay,Sanshui,Sichuan,Ordos,Tarim and Ying-Qiong,this paper systematically compares the geochemical compositions of abiogenic versus biogenic gases.Emphasis is placed on the diagnostic signatures of abiogenic gases in terms of gas composition,and carbon,hydrogen and helium isotopes.The main findings are as follows.(1)In hydrothermal spring systems,abiogenic alkane gases are extremely scarce.Methane concentrations are typically less than 1%,with almost no detectable C^(2+)hydrocarbons.The gas is dominantly composed of CO_(2),while N_(2)is the major component in a few samples.(2)Abiogenic alkane gases display distinct isotopic signatures,including enriched methane carbon isotopic compositions(δ^(13)C_(1)>-25‰generally),complete carbon isotopic reversal(δ^(13)C_(1)>δ^(13)C_(2)>δ^(13)C_(3)>δ^(13)C_(4)),and enriched helium isotope(R/Ra>0.5,CH_(4)/^(3)He≤10^(6)generally).(3)The hydrogen isotopic composition of abiogenic alkane gases may be characterized by a positive sequence(δD_(1)<δD_(2)<δD_(3)),or a complete reversal(δD_(1)>δD_(2)>δD_(3)),or a V-shaped distribution(δD_(1)>δD_(2),δD_(2)<δD_(3)).The hydrogen isotopic compositions of methane generally show limited variation(about 9‰),possibly due to hydrogen isotopic exchange with connate water.(4)In terms of identifying gas origin,CH_(4)/^(3)He-R/Ra andδ^(13)CCO_(2)-R/Ra charts are more effective than CO_(2)/^(3)He-R/Ra chart.These new geological insights provide theoretical clues and diagnostic charts for the genetic identification of natural gas and further research on abiogenic gases.展开更多
Microbial vanadate(V(V))reduction is a key process for environmental geochemistry and detoxification of vanadium(V).However,the electron transfer pathways and V isotope fractionation involved in this process are not y...Microbial vanadate(V(V))reduction is a key process for environmental geochemistry and detoxification of vanadium(V).However,the electron transfer pathways and V isotope fractionation involved in this process are not yet fully understood.In this study,the V(V)reduction mechanisms with concomitant V isotope fractionation by the Gram-positive bacterium Bacillus subtilis(B.subtilis)and the Gramnegative bacterium Thauera humireducens(T.humireducens)were investigated.Both strains could effectively reduce V(V),removing(90.5%±1.6%)and(93.0%±1.8%)of V(V)respectively from an initial concentration of 50 mg L^(-1) during a 10-day incubation period.V(V)was bioreduced to insoluble vanadium(IV),which was distributed both inside and outside the cells.Electron transfer via cytochrome C,nicotinamide adenine dinucleotide,and glutathione played critical roles in V(V)reduction.Metabolomic analysis showed that differentially enriched metabolites(quinone,biotin,and riboflavin)mediated electron transfer in both strains.The aqueous V in the remaining solution became isotopically heavier as V(V)bioreduction proceeded.The obtained V isotope composition dynamics followed a Rayleigh fractionation model,and the isotope enrichment factor(e)was(–0.54‰±0.04‰)for B.subtilis and(–0.32‰±0.03‰)for T.humireducens,with an insignificant difference.This study provides molecular insights into electron transfer for V(V)bioreduction and reveals V isotope fractionation during this bioprocess,which is helpful for understanding V biogeochemistry and developing novel strategies for V remediation.展开更多
Stable Sr isotopic composition(δ^(88/86)Sr)can be used to study magmatic processes,but their fractionation mechanism during magmatic evolution remains unclear.To understand the fractionation behaviors of the stable S...Stable Sr isotopic composition(δ^(88/86)Sr)can be used to study magmatic processes,but their fractionation mechanism during magmatic evolution remains unclear.To understand the fractionation behaviors of the stable Sr isotopes during magmatism,we report theδ^(88/86)Sr values of the Huili granitic pluton,which was subjected to intensive crystal-melt separation.The Huili pluton consists of K-feldspar granite and more evolved albite granite,and the albite granite exhibits significantly higherδ^(88/86)Sr values(+0.36‰to+0.52‰)than that of K-feldspar granite(+0.11‰to+0.25‰).K-feldspar,which contributes most of the Sr budget of the K-feldspar granite,has slightly lowerδ^(88/86)Sr values(−0.01‰to+0.17‰)than the whole rock.Theδ^(88/86)Sr variation of the Huili granites can be explained by separation of melt from K-feldspar-dominated crystals,because crystallization of K-feldspar can result in heavy Sr isotopic composition of the extracted interstitial melt.Stable Sr and Ba isotopic ratios in the Huili granites are highly coupled toward the heavy direction,refl ecting their similar element partitioning and isotope fractionation behaviors between the crystalline K-feldspar and melt.This study indicates that melt extraction plays a key role in granitic magma evolution.展开更多
The lack of understanding of heavy metal speciation and solubility control mechanisms in smelting soils limits the effective pollution control.In this study smelting soils were investigated by an advanced mineralogica...The lack of understanding of heavy metal speciation and solubility control mechanisms in smelting soils limits the effective pollution control.In this study smelting soils were investigated by an advanced mineralogical analysis(AMICS),leaching tests and thermodynamic modelling.The aims were to identify the partitioning and release behaviour of Pb,Zn,Cd and As.The integration of multiple techniques was necessary and displayed coherent results.In addition to the residual fraction,Pb and Zn were predominantly associated with reducible fractions,and As primarily existed as the crystalline iron oxide-bound fractions.AMICS quantitative analysis further confirmed that Fe oxyhydroxides were the common dominant phase for As,Cd,Pb and Zn.In addition,a metal arsenate(paulmooreite)was an important mineral host for Pb and As.The pH-stat leaching indicted that the release of Pb,Zn and Cd increased towards low pH values while release of As increased towards high p H values.The separate leaching schemes were associated with the geochemical behaviour under the control of minerals and were confirmed by thermodynamic modelling.PHREEQC calculations suggested that the formation of arsenate minerals(schultenite,mimetite and koritnigite)and the binding to Fe oxyhydroxides synchronously controlled the release of Pb,Zn,Cd and As.Our results emphasized the governing role of Fe oxyhydroxides and secondary insoluble minerals in natural attenuation of heavy metals,which provides a novelty strategy for the stabilization of multi-metals in smelting sites.展开更多
The phenomenon of carbon isotopic fractionation,induced by the transport of methane in tight sedimentary rocks through processes primarily involving diffusion and adsorption/desorption,is ubiquitous in nature and play...The phenomenon of carbon isotopic fractionation,induced by the transport of methane in tight sedimentary rocks through processes primarily involving diffusion and adsorption/desorption,is ubiquitous in nature and plays a significant role in numerous geological and geochemical systems.Consequently,understanding the mechanisms of transport-induced carbon isotopic fractionation both theoretically and experimentally is of considerable scientific importance.However,previous experimental studies have observed carbon isotope fractionation phenomena that are entirely distinct,and even exhibit opposing characteristics.At present,there is a lack of a convincing mechanistic explanation and valid numerical model for this discrepancy.Here,we performed gas transport experiments under different gas pressures(1–5 MPa)and confining pressures(10–20 MPa).The results show that methane carbon isotope fractionation during natural gas transport through shale is controlled by its pore structure and evolves regularly with increasing effective stress.Compared with the carbon isotopic composition of the source gas,the initial effluent methane is predominantly depleted in^(13)C,but occasionally exhibits^(13)C enrichment.The carbon isotopic composition of effluent methane converges to that of the source gas as mass transport reaches a steady state.The evolution patterns of the isotope fractionation curve,transitioning from the initial non-steady state to the final steady state,can be categorized into five distinct types.The combined effect of multi-level transport channels offers the most compelling mechanistic explanation for the observed evolution patterns and their interconversion.Numerical simulation studies demonstrate that existing models,including the Rayleigh model,the diffusion model,and the coupled diffusion-adsorption/desorption model,are unable to describe the observed complex isotope fractionation behavior.In contrast,the multi-scale multi-mechanism coupled model developed herein,incorporating diffusion and adsorption/desorption across multi-level transport channels,effectively reproduces all the observed fractionation patterns and supports the mechanistic rationale for the combined effect.Finally,the potential carbon isotopic fractionation resulting from natural gas transport in/through porous media and its geological implications are discussed in several hypothetical scenarios combining numerical simulations.These findings highlight the limitations of carbon isotopic parameters for determining the origin and maturity of natural gas,and underscore their potential in identifying greenhouse gas leaks and tracing sources.展开更多
Lack of information regarding lithium(Li)crystal chemistry in numerous minerals,especially those containing trace amounts of Li(ranging from a few to tens of ppm),limits our understanding of Li isotopic fractionation ...Lack of information regarding lithium(Li)crystal chemistry in numerous minerals,especially those containing trace amounts of Li(ranging from a few to tens of ppm),limits our understanding of Li isotopic fractionation in pegmatites.In this study,we examined the Li isotopic composition and Li content in various Li-poor(e.g.,quartz or feldspar)together with Li-rich(sopdumene or lepidolite)mineral phases within granitic pegmatites.We compiled a comprehensive dataset,encompassing a broad spectrum of Li contents(ranging from a few to tens of thousands of ppm)and Li isotopic values(-8‰to 41‰).The minerals exhibit distinct Li isotopic signatures.Specifically,elbaite and beryl show the highest values,while biotite displays a negative average.Compared to individual minerals,whole rocks demonstrate lower Li isotopic values,with pegmatites exhibiting the highest and non-granitic pegmatite wall rocks showing the lowest.Our study also uncovers a clear“V”shape relationship between Li isotopic values and logarithm of Li contents,with different mineral groups occupying specific regions within this shape.Furthermore,a significant correlation was observed between average Li isotopic values and Li-O(OH,F)bond lengths in various minerals.These discoveries underscore the crucial role of crystal chemistry in shaping the Li isotopic behavior in pegmatites from a statistical perspective.展开更多
Isotope eff ects are pivotal in understanding silicate melt evaporation and planetary accretion processes.Based on the Hertz-Knudsen equation,the current theory often fails to predict observed isotope fractionations o...Isotope eff ects are pivotal in understanding silicate melt evaporation and planetary accretion processes.Based on the Hertz-Knudsen equation,the current theory often fails to predict observed isotope fractionations of laboratory experiments due to its oversimplified assumptions.Here,we point out that the Hertz-Knudsen-equation-based theory is incomplete for silicate melt evaporation cases and can only be used for situations where the vaporized species is identical to the one in the melt.We propose a new model designed for silicate melt evaporation under vacuum.Our model considers multiple steps including mass transfer,chemical reaction,and nucleation.Our derivations reveal a kinetic isotopic fractionation factor(KIFF orα)αour model=[m(^(1)species)/m(^(2)species)]^(0.5),where m(species)is the mass of the reactant of reaction/nucleation-limiting step or species of diffusion-limiting step and superscript 1 and 2 represent light and heavy isotopes,respectively.This model can eff ectively reproduce most reported KIFFs of laboratory experiments for various elements,i.e.,Mg,Si,K,Rb,Fe,Ca,and Ti.And,the KIFF-mixing model referring that an overall rate of evaporation can be determined by two steps jointly can account for the eff ects of low P_(H2)pressure,composition,and temperature.In addition,we find that chemical reactions,diffusion,and nucleation can control the overall rate of evaporation of silicate melts by using the fitting slope in ln(−ln f)versus ln(t).Notably,our model allows for the theoretical calculations of parameters like activation energy(E_(a)),providing a novel approach to studying compositional and environmental eff ects on evaporation processes,and shedding light on the formation and evolution of the proto-solar and Earth-Moon systems.展开更多
It is well-known that the equilibrium isotope fractionation of mercury(Hg)includes classical massdependent fractionations(MDFs)and nuclear volume effect(NVE)induced mass-independent fractionations(MIFs).However,the ef...It is well-known that the equilibrium isotope fractionation of mercury(Hg)includes classical massdependent fractionations(MDFs)and nuclear volume effect(NVE)induced mass-independent fractionations(MIFs).However,the effect of the NVE on these kinetic processes is not known.The total fractionations(MDFs+NVEinduced MIFs)of several representative Hg-incorporated substances were selected and calculated with ab initio calculations in this work for both equilibrium and kinetic processes.NVE-induced MIFs were calculated with scaled contact electron densities at the nucleus through systematic evaluations of their accuracy and errors using the Gaussian09 and DIRAC19 packages(named the electron density scaling method).Additionally,the NVE-induced kinetic isotope effect(KIE)of Hg isotopes are also calculated with this method for several representative Hg oxidation reactions by chlorine species.Total KIEs for 202 Hg/^(198)Hg ranging from−2.27‰to 0.96‰are obtained.Three anomalous^(202)Hg-enriched KIEs(δ^(202)Hg/^(198)Hg=0.83‰,0.94‰,and 0.96‰,)caused by the NVE are observed,which are quite different from the classical view(i.e.,light isotopes react faster than the heavy ones).The electron density scaling method we developed in this study can provide an easier way to calculate the NVE-induced KIEs for heavy isotopes and serve to better understand the fractionation mechanisms of mercury isotope systems.展开更多
The research progress of isotopic fractionation in the process of shale gas/coalbed methane migration has been reviewed from three aspects: characteristics and influencing factors, mechanism and quantitative character...The research progress of isotopic fractionation in the process of shale gas/coalbed methane migration has been reviewed from three aspects: characteristics and influencing factors, mechanism and quantitative characterization model, and geological application. It is found that the isotopic fractionation during the complete production of shale gas/coalbed methane shows a four-stage characteristic of “stable-lighter-heavier-lighter again”, which is related to the complex gas migration modes in the pores of shale/coal. The gas migration mechanisms in shale/coal include seepage, diffusion, and adsorption/desorption. Among them, seepage driven by pressure difference does not induce isotopic fractionation, while diffusion and adsorption/desorption lead to significant isotope fractionation. The existing characterization models of isotopic fractionation include diffusion fractionation model, diffusion-adsorption/desorption coupled model, and multi-scale and multi-mechanism coupled model. Results of model calculations show that the isotopic fractionation during natural gas migration is mainly controlled by pore structure, adsorption capacity, and initial/boundary conditions of the reservoir rock. So far, the isotope fractionation model has been successfully used to evaluate critical parameters, such as gas-in-place content and ratio of adsorbed/free gas in shale/coal etc. Furthermore, it has shown promising application potential in production status identification and decline trend prediction of gas well. Future research should focus on:(1) the co-evolution of carbon and hydrogen isotopes of different components during natural gas migration,(2) the characterization of isotopic fractionation during the whole process of gas generation-expulsion-migration-accumulation-dispersion, and(3) quantitative characterization of isotopic fractionation during natural gas migration in complex pore-fracture systems and its application.展开更多
[Objective] This study aimed to promote the combination of cultivation and livestock farming, and to explore an environment-protecting farming style. [Method]The effects of anaerobically fermented complete compound so...[Objective] This study aimed to promote the combination of cultivation and livestock farming, and to explore an environment-protecting farming style. [Method]The effects of anaerobically fermented complete compound sow feed, added with Lactobacillus and Bacillus subtilis, on the chemical fractionation of copper, iron, zinc and manganese in feed and pig manure and skatole content in pig manure were investigated. [Result] Compared with those in the non-fermented feed, in the fermented feed and pig manure, the acetic acid-extractable copper, iron, zinc and manganese contents increased significantly（P0.05）, the reduced copper and iron contents increased significantly（P 0.05）, the oxidized copper and iron contents reduced significantly（P0.05）, and the residual copper contents remained unchangeable（P0.05）. The pH value of fermented feed decreased significantly（P0.05）, and that of pig manure increased significantly（P0.05）. The skatole content in pig manure decreased significantly（P 0.01）. The Lactobacillus abundance and amylase and cellulase activity increased significantly（P 0.05）. [Conclusion] The fermentation of feed changed the chemical fractionation of copper, iron, zinc and manganese in feed and pig manure, and reduced the manure odor.展开更多
An anomalous isotope effect exists in many heavy element isotope systems （e.g., Sr, Gd, Zn, U）. This effect used to be called the ＂odd--even isotope effect＂ because the odd mass number isotopes behave differently ...An anomalous isotope effect exists in many heavy element isotope systems （e.g., Sr, Gd, Zn, U）. This effect used to be called the ＂odd--even isotope effect＂ because the odd mass number isotopes behave differently from the even mass number isotopes. This mass-indepen- dent isotope fractionation driving force, which originates from the difference in the ground-state electronic energies caused by differences in nuclear size and shape, is cur- rently denoted as the nuclear field shift effect （NFSE）. It is found that the NFSE can drive isotope fractionation of some heavy elements （e.g., Hg, T1, U） to an astonishing degree, far more than the magnitude caused by the con- ventional mass-dependent effect （MDE）. For light ele- ments, the MDE is the dominant factor in isotope fractionation, while the NFSE is neglectable. Furthermore, the MDE and the NFSE both decrease as temperatures increase, though at different rates. The MDE decreases rapidly with a factor of 1/T2, while the NFSE decreases slowly with a factor of 1/T. As a result, even at high temperatures, the NFSE is still significant for many heavy element isotope systems. In this review paper, we begin with an introduction of the basic concept of the NSFE, including its history and recent progress, and follow with the potential implications of the inclusion of the NFSE into the kinetic isotope fractionation effect （KIE） and heavy isotope geochronology.展开更多
Equilibrium isotope fractionation of thallium(Tl) includes the traditional mass-dependent isotope fractionation effect and the nuclear volume effect(NVE). The NVE dominates the overall isotope fractionation, especiall...Equilibrium isotope fractionation of thallium(Tl) includes the traditional mass-dependent isotope fractionation effect and the nuclear volume effect(NVE). The NVE dominates the overall isotope fractionation, especially at high temperatures. Heavy Tl isotopes tend to be enriched in oxidized Tl^3+-bearing species. Our NVE fractionation results of oxidizing Tl^+ to Tl^3+ can explain the positive enrichments observed in ferromanganese sediments. Experimental results indicate that there could be0.2–0.3 e-unit fractionation between sulfides and silicates at 1650 ℃. It is consistent with our calculation results,which are in the range of 0.17–0.38 e-unit. Importantly,Tl’s concentration in the bulk silicate Earth(BSE) can be used to constrain the amount of materials delivered to Earth during the late veneer accretion stage. Because the Tl concentration in BSE is very low and its Tl isotope composition is similar with that of chondrites, suggesting either no Tl isotope fractionation occurred during numerous evaporation events, or the Tl in current BSE was totally delivered by late veneer. If it is the latter, the Tl-contentbased estimation could challenge the magnitude of late veneer which had been constrained by the amount of highly siderophile elements in BSE. Our results show that the lateaccreted mass is at least five-times larger than the previously suggested magnitude, i.e., 0.5 wt% of current Earth’s mass. The slightly lighter 205 Tl composition of BSE relative to chondrites is probable a sign of occurrence of Tlbearing sulfides, which probably were removed from the mantle in the last accretion stage of the Earth.展开更多
Equilibrium Zn isotope fractionation was inves- tigated using first-principles quantum chemistry methods at the B3LYP/6-311G level. The volume variable cluster model method was used to calculate isotope fractionation ...Equilibrium Zn isotope fractionation was inves- tigated using first-principles quantum chemistry methods at the B3LYP/6-311G level. The volume variable cluster model method was used to calculate isotope fractionation factors of sphalerite, smithsonite, calcite, anorthite, for- sterite, and enstatite. The water-droplet method was used to calculate Zn isotope fractionation factors of Zn^2＋-bearing aqueous species; their reduced partition function ratio factors decreased in the order [Zn（H2O）6]^2＋ 〉 [ZnCl（H2O）5]^ ＋ 〉 [ZnCl2（H2O）4] 〉 [ZnCl3（H20）2]^-〉 ZnCl4]^2-. Gas- eous ZnCl2 was also calculated for vaporization processes. Kinetic isotope fractionation of diffusional processes in a vacuum was directly calculated using formulas provided by Richter and co-workers. Our calculations show that in addition to the kinetic isotope effect of diffusional processes, equilibrium isotope fractionation also contributed nontriv- ially to observed Zn isotope fractionation of vaporization processes. The calculated net Zn isotope fractionation of vaporization processes was 7-7.5‰, with ZnCl2 as the gas- eous species. This matches experimental observations of the range of Zn isotope distribution of lunar samples. Therefore, vaporization processes may be the cause of the large distri- bution of Zn isotope signals found on the Moon. However, we cannot further distinguish the origin of such vaporization processes; it might be due either to igneous rock melting inmeteorite bombardments or to a giant impact event. Fur- thermore, isotope fractionation between Zn-bearing aqueous species and minerals that we have provided helps explain Zn isotope data in the fields of ore deposits and petrology.展开更多
The potential utilization and development of the Ba isotope tool depend on an accurateδ^(137/134)Ba determination of the samples.During the chemical purification,whether the adsorption process on the surface of the i...The potential utilization and development of the Ba isotope tool depend on an accurateδ^(137/134)Ba determination of the samples.During the chemical purification,whether the adsorption process on the surface of the ionexchange resin could lead to the Ba isotopic fractionation and the degree of fractionation directly influence the accurateδ^(137/134)Ba determination.In the present work,first-principles calculations based on the density functional theory were used to quantify the Ba isotopic equilibrium fractionation factor between the aqueous solution and the resin in the acid leaching process.By constructing and optimizing the geometric configurations of Ba-containing species,Ba(H_(2)O)_(n)^(2+),Ba(H_(2)O)_(n)Cl_(2),Ba(H_(2)O)_(n)(NO_(3))2,and the adsorbed Ba^(2+)on the surface of the resin,extracting the harmonic vibrational frequencies,we finally at 298 K obtained the fractionations,Δ^(137/134)Ba_(soln-ads)=0.07‰,Δ^(137/134)Ba_(Ba(H_(2)O)_(n)Cl_(2)-ads)=0.05‰,andΔ^(137/134)-Ba^(Ba(H_(2)O)_(n)(NO_(3))2-ads)=0.02‰.Overall,there were almost no Ba isotope fractionations during leaching.Although the Ba isotope fractionation can be magnified by the Rayleigh fractionation process in purification,the difference inδ137/134Ba between the initial and final stages did not exceed0.060‰(or 0.045‰)when leaching the standard sample with HCl or HNO_(3),which is equal to or less than the accuracy of Ba isotopic analysis.At a common yield of89.75%,Ba isotopic fractionation induced by incomplete recovery was 0.015‰for HCl(or 0.011‰for HNO_(3)).Finally,if the influence of an incomplete recovery on theδ137/134Ba determination needs to be ignored,the recovery is suggested to be not less than 67%for HCl(or 46%for HNO_(3)).展开更多
Typical sediments from Taihu Lake, a meso-to-hypereutrophic lake, were collected and examined on the basis of P-fractionation by sequential extraction scheme. Sedimentary inorganic phosphorus were fractioned into four...Typical sediments from Taihu Lake, a meso-to-hypereutrophic lake, were collected and examined on the basis of P-fractionation by sequential extraction scheme. Sedimentary inorganic phosphorus were fractioned into four forms and the rank order according to the mean concentration of P-fractions in Taihu Lake was NaOH-P>BD-P>HCl-P>NH_4Cl-P. The concentrations of BD-P were linearly correlated with the content of active Fe(R2=0.96). Also, the linear relationship between the sum of BD-P and NaOH-P and the sum of active Fe and active Al content was observed within the six sediments investigated(R2=0.96). Moreover, the bio-available phosphorus(BAP) content was estimated by the sum of NH_4Cl-P, BD-P, and NaOH-P, viz. BAP=NH_4Cl-P+NaOH-P+BD-P. In Taihu Lake, the BAP contents are ranging from 0.10 mg/g dw to 1.25 mg/g dw, and average 0.40 mg/g dw for all sediment samples. The relative contributions of BAP to total sedimentary phosphorus(TP) and inorganic sedimentary phosphorus(IP) range from 18.67% to 50.79%(33.61% on average) and from 52.82% to 82.09%(67.81% on average), respectively.展开更多
This work investigated the distribution and speciation of Cd, Cu, Pb, Fe and Mn in the shallow sediments of Jinzhou Bay, Northeast China, which has been heavily contaminated by nonferrous smelting activities. The conc...This work investigated the distribution and speciation of Cd, Cu, Pb, Fe and Mn in the shallow sediments of Jinzhou Bay, Northeast China, which has been heavily contaminated by nonferrous smelting activities. The concentrations of Cd, Cu and Pb in sediments were found to be 100, 13 and 7 times, respectively, being higher than the national guideline （GB 18668-2002）. Sequential extraction test showed that 39%-61% of Cd were exchangeable fractions, indicating that Cd in the sediments posed a high risk to local environments. While Cu and Pb were at moderate risk levels. According to the relationships between percentage of metal speciation and total metal concentration, it was concluded that the distributions of Cd, Cu and Pb in some geochemical fractions were dynamic in the process of pollutants migration and the stability of metals in sediments of Jinzhou Bay decreased in the order of Pb 〉 Cu 〉 Cd.展开更多
REE fractionation during the weathering of dolomite has been recognized for decades.A regolith profile on dolomite in southwest Yunnan of China was selected to investigate the behaviors of REE during weathering.The we...REE fractionation during the weathering of dolomite has been recognized for decades.A regolith profile on dolomite in southwest Yunnan of China was selected to investigate the behaviors of REE during weathering.The weathering of dolomite is divided into two stages：the pedogenesis stage and soil evolution stage,corresponding to the saprolites and soils respectively in the regolith profile. SiO_2,TiO_2,P_2O_5,Zr,Hf,Nb and Ta were immobile components during the weathering by and large, while Al_2O_3,K_2O and Fe_2O_3 were lost during the soil evolution stage in the physical form（clay minerals probably）.REE were fractionated during the whole weathering of dolomite.The field weathering profile and the lab acid-leaching experiments on dolomite indicate that MREE were enriched clearly relative to other REE during the pedogenesis stage in a ＂capillary ascending-adsorption＂ mechanism, but they did not fractionate clearly in the soil evolution stage.REE were lost and accumulated in the weathering front of dolomite during the soil evolution stage in a ＂physical-chemical leaching＂ mechanism.展开更多
基金supported by the Fundamental Research Funds for the Central Universities(QNTD202302)National Natural Science Foundation of China(22378024)the Foreign expert program(G2022109001L).
文摘Developing a cost-effective and environmentally friendly process for the production of valuable chemicals from abundant herbal biomass receives great attentions in recent years.Herein,taking advantage of the“lignin first”strategy,corn straw is converted to valuable chemicals including lignin monomers,furfural and 5-methoxymethylfurfural via a two steps process.The key of this research lies in the development of a green and low-cost catalytic process utilizing magnetic Raney Ni catalyst and high boiling point ethylene glycol.The utilization of neat ethylene glycol as the sole slovent under atmospheric conditions obviates the need for additional additives,thereby facilitating the entire process to be conducted in glass flasks and rendering it highly convenient for scaling up.In the initial step,depolymerization of corn straw lignin resulted in a monomer yield of 18.1 wt%.Subsequently,in a dimethyl carbonate system,the carbohydrate component underwent complete conversion in a one-pot process,yielding furfural and 5-methoxymethylfurfural as the primary products with an impressive yield of 47.7%.
基金supported by the Natural Science Foundation of China(Grant No.42302170)National Postdoctoral Innovative Talent Support Program(Grant No.BX20220062)+3 种基金CNPC Innovation Found(Grant No.2022DQ02-0104)National Science Foundation of Heilongjiang Province of China(Grant No.YQ2023D001)Postdoctoral Science Foundation of Heilongjiang Province of China(Grant No.LBH-Z22091)the Natural Science Foundation of Shandong Province(Grant No.ZR2022YQ30).
文摘Prediction of production decline and evaluation of the adsorbed/free gas ratio are critical for determining the lifespan and production status of shale gas wells.Traditional production prediction methods have some shortcomings because of the low permeability and tightness of shale,complex gas flow behavior of multi-scale gas transport regions and multiple gas transport mechanism superpositions,and complex and variable production regimes of shale gas wells.Recent research has demonstrated the existence of a multi-stage isotope fractionation phenomenon during shale gas production,with the fractionation characteristics of each stage associated with the pore structure,gas in place(GIP),adsorption/desorption,and gas production process.This study presents a new approach for estimating shale gas well production and evaluating the adsorbed/free gas ratio throughout production using isotope fractionation techniques.A reservoir-scale carbon isotope fractionation(CIF)model applicable to the production process of shale gas wells was developed for the first time in this research.In contrast to the traditional model,this model improves production prediction accuracy by simultaneously fitting the gas production rate and δ^(13)C_(1) data and provides a new evaluation method of the adsorbed/free gas ratio during shale gas production.The results indicate that the diffusion and adsorption/desorption properties of rock,bottom-hole flowing pressure(BHP)of gas well,and multi-scale gas transport regions of the reservoir all affect isotope fractionation,with the diffusion and adsorption/desorption parameters of rock having the greatest effect on isotope fractionation being D∗/D,PL,VL,α,and others in that order.We effectively tested the universality of the four-stage isotope fractionation feature and revealed a unique isotope fractionation mechanism caused by the superimposed coupling of multi-scale gas transport regions during shale gas well production.Finally,we applied the established CIF model to a shale gas well in the Sichuan Basin,China,and calculated the estimated ultimate recovery(EUR)of the well to be 3.33×10^(8) m^(3);the adsorbed gas ratio during shale gas production was 1.65%,10.03%,and 23.44%in the first,fifth,and tenth years,respectively.The findings are significant for understanding the isotope fractionation mechanism during natural gas transport in complex systems and for formulating and optimizing unconventional natural gas development strategies.
基金financial support provided by the University of New England,Australia for conducting this research。
文摘Water-soluble organic matter(WSOM)significantly influences the transport of metals and organic contaminants in soils,yet the interaction specifics with antimony(Sb)remain largely unexplored.Antimony is of particular environmental concern due to its toxic properties and harmful effects on ecosystems and human health.Employing a three-step fractionation method with polyvinylpyrrolidone(PVP),this study aimed to isolate and analyze humic acids(HA),PVP-non adsorbed fulvic acids(FAA),and PVP-adsorbed fulvic acids(FAB)from WSOM in soil spiked with Sb and incubated for 18 months.These fractions underwent chemical analysis for carbon(C),nitrogen(N),total organic carbon(TOC),and Sb,complemented by FTIR and 1H NMR spectroscopic characterization.The study revealed that HA wasmore aliphatic,with Sb predominantly associating with the fulvic acid(FA)fraction,accounting for 97%of Sb in extracts.Specifically,the FAA subfraction held substantial portions of total carbon(TC),total nitrogen(TN),total organic carbon(TOC),and Sb.Correlations between Sb concentrations and TN,TC,and TOC were significant.Extraction methods showed NaOH and Na_(4)P_(2)O_(7) outperformed HCl and deionised water in extracting TC,TN,and TOC,with higher Sb concentrations found in Na_(4)P_(2)O_(7) and NaOH extracts.This underscores the role of Fe/Al-SOM complexes in Sb soil availability.The results revealed that FAA subfraction accounted for 76%,64%and 94%of TN,TOC and Sb,respectively.Therefore,this research highlights the FAA fraction’s central role,predominantly comprising non-humic substances like amines,in the availability of C,N,and Sb in Sb-impacted soils.The findings offer insights for environmental management and remediation strategies.
基金Supported by PetroChina Science and Technology Research and Technology Development Project(2021DJ0502)Open Research Project of Key Laboratory of Shale Gas Resources Exploration,Ministry of Natural Resources(Chongqing Institute of Geology and Mineral Resources)(KLSGE-2023).
文摘Based on geochemical data from natural gas samples across spring water systems and sedimentary basins,including Songliao,Bohai Bay,Sanshui,Sichuan,Ordos,Tarim and Ying-Qiong,this paper systematically compares the geochemical compositions of abiogenic versus biogenic gases.Emphasis is placed on the diagnostic signatures of abiogenic gases in terms of gas composition,and carbon,hydrogen and helium isotopes.The main findings are as follows.(1)In hydrothermal spring systems,abiogenic alkane gases are extremely scarce.Methane concentrations are typically less than 1%,with almost no detectable C^(2+)hydrocarbons.The gas is dominantly composed of CO_(2),while N_(2)is the major component in a few samples.(2)Abiogenic alkane gases display distinct isotopic signatures,including enriched methane carbon isotopic compositions(δ^(13)C_(1)>-25‰generally),complete carbon isotopic reversal(δ^(13)C_(1)>δ^(13)C_(2)>δ^(13)C_(3)>δ^(13)C_(4)),and enriched helium isotope(R/Ra>0.5,CH_(4)/^(3)He≤10^(6)generally).(3)The hydrogen isotopic composition of abiogenic alkane gases may be characterized by a positive sequence(δD_(1)<δD_(2)<δD_(3)),or a complete reversal(δD_(1)>δD_(2)>δD_(3)),or a V-shaped distribution(δD_(1)>δD_(2),δD_(2)<δD_(3)).The hydrogen isotopic compositions of methane generally show limited variation(about 9‰),possibly due to hydrogen isotopic exchange with connate water.(4)In terms of identifying gas origin,CH_(4)/^(3)He-R/Ra andδ^(13)CCO_(2)-R/Ra charts are more effective than CO_(2)/^(3)He-R/Ra chart.These new geological insights provide theoretical clues and diagnostic charts for the genetic identification of natural gas and further research on abiogenic gases.
基金supported by the National Natural Science Foundation of China(U21A2033)the Fundamental Research Funds for the Central Universities(2652022103).
文摘Microbial vanadate(V(V))reduction is a key process for environmental geochemistry and detoxification of vanadium(V).However,the electron transfer pathways and V isotope fractionation involved in this process are not yet fully understood.In this study,the V(V)reduction mechanisms with concomitant V isotope fractionation by the Gram-positive bacterium Bacillus subtilis(B.subtilis)and the Gramnegative bacterium Thauera humireducens(T.humireducens)were investigated.Both strains could effectively reduce V(V),removing(90.5%±1.6%)and(93.0%±1.8%)of V(V)respectively from an initial concentration of 50 mg L^(-1) during a 10-day incubation period.V(V)was bioreduced to insoluble vanadium(IV),which was distributed both inside and outside the cells.Electron transfer via cytochrome C,nicotinamide adenine dinucleotide,and glutathione played critical roles in V(V)reduction.Metabolomic analysis showed that differentially enriched metabolites(quinone,biotin,and riboflavin)mediated electron transfer in both strains.The aqueous V in the remaining solution became isotopically heavier as V(V)bioreduction proceeded.The obtained V isotope composition dynamics followed a Rayleigh fractionation model,and the isotope enrichment factor(e)was(–0.54‰±0.04‰)for B.subtilis and(–0.32‰±0.03‰)for T.humireducens,with an insignificant difference.This study provides molecular insights into electron transfer for V(V)bioreduction and reveals V isotope fractionation during this bioprocess,which is helpful for understanding V biogeochemistry and developing novel strategies for V remediation.
基金supported by National Natural Science Foundation of China(42473009).
文摘Stable Sr isotopic composition(δ^(88/86)Sr)can be used to study magmatic processes,but their fractionation mechanism during magmatic evolution remains unclear.To understand the fractionation behaviors of the stable Sr isotopes during magmatism,we report theδ^(88/86)Sr values of the Huili granitic pluton,which was subjected to intensive crystal-melt separation.The Huili pluton consists of K-feldspar granite and more evolved albite granite,and the albite granite exhibits significantly higherδ^(88/86)Sr values(+0.36‰to+0.52‰)than that of K-feldspar granite(+0.11‰to+0.25‰).K-feldspar,which contributes most of the Sr budget of the K-feldspar granite,has slightly lowerδ^(88/86)Sr values(−0.01‰to+0.17‰)than the whole rock.Theδ^(88/86)Sr variation of the Huili granites can be explained by separation of melt from K-feldspar-dominated crystals,because crystallization of K-feldspar can result in heavy Sr isotopic composition of the extracted interstitial melt.Stable Sr and Ba isotopic ratios in the Huili granites are highly coupled toward the heavy direction,refl ecting their similar element partitioning and isotope fractionation behaviors between the crystalline K-feldspar and melt.This study indicates that melt extraction plays a key role in granitic magma evolution.
基金funded by the National Key Research and Development Program of China(No.2019YFC1803601)the National Natural Science Foundation of China(No.42177392)the Fundamental Research Funds for the Central Universities of Central South University(No.2021zzts0122)。
文摘The lack of understanding of heavy metal speciation and solubility control mechanisms in smelting soils limits the effective pollution control.In this study smelting soils were investigated by an advanced mineralogical analysis(AMICS),leaching tests and thermodynamic modelling.The aims were to identify the partitioning and release behaviour of Pb,Zn,Cd and As.The integration of multiple techniques was necessary and displayed coherent results.In addition to the residual fraction,Pb and Zn were predominantly associated with reducible fractions,and As primarily existed as the crystalline iron oxide-bound fractions.AMICS quantitative analysis further confirmed that Fe oxyhydroxides were the common dominant phase for As,Cd,Pb and Zn.In addition,a metal arsenate(paulmooreite)was an important mineral host for Pb and As.The pH-stat leaching indicted that the release of Pb,Zn and Cd increased towards low pH values while release of As increased towards high p H values.The separate leaching schemes were associated with the geochemical behaviour under the control of minerals and were confirmed by thermodynamic modelling.PHREEQC calculations suggested that the formation of arsenate minerals(schultenite,mimetite and koritnigite)and the binding to Fe oxyhydroxides synchronously controlled the release of Pb,Zn,Cd and As.Our results emphasized the governing role of Fe oxyhydroxides and secondary insoluble minerals in natural attenuation of heavy metals,which provides a novelty strategy for the stabilization of multi-metals in smelting sites.
基金the National Natural Science Foundation of China(Grant Nos.42302170,42302160)the Innovation Platform for Academicians of Hainan Province(YSPTZX202301)+3 种基金the National Postdoctoral Innovative Talent Support Program(Grant No.BX20220062)the National Science Foundation of Heilongjiang Province of China(Grant No.YQ2023D001)the Project of Sanya Yazhou Bay Science and Technology City(Grant No.SCKJ-JYRC-2023-01)CNPC Innovation Found(Grant No.2022DQ02-0104).
文摘The phenomenon of carbon isotopic fractionation,induced by the transport of methane in tight sedimentary rocks through processes primarily involving diffusion and adsorption/desorption,is ubiquitous in nature and plays a significant role in numerous geological and geochemical systems.Consequently,understanding the mechanisms of transport-induced carbon isotopic fractionation both theoretically and experimentally is of considerable scientific importance.However,previous experimental studies have observed carbon isotope fractionation phenomena that are entirely distinct,and even exhibit opposing characteristics.At present,there is a lack of a convincing mechanistic explanation and valid numerical model for this discrepancy.Here,we performed gas transport experiments under different gas pressures(1–5 MPa)and confining pressures(10–20 MPa).The results show that methane carbon isotope fractionation during natural gas transport through shale is controlled by its pore structure and evolves regularly with increasing effective stress.Compared with the carbon isotopic composition of the source gas,the initial effluent methane is predominantly depleted in^(13)C,but occasionally exhibits^(13)C enrichment.The carbon isotopic composition of effluent methane converges to that of the source gas as mass transport reaches a steady state.The evolution patterns of the isotope fractionation curve,transitioning from the initial non-steady state to the final steady state,can be categorized into five distinct types.The combined effect of multi-level transport channels offers the most compelling mechanistic explanation for the observed evolution patterns and their interconversion.Numerical simulation studies demonstrate that existing models,including the Rayleigh model,the diffusion model,and the coupled diffusion-adsorption/desorption model,are unable to describe the observed complex isotope fractionation behavior.In contrast,the multi-scale multi-mechanism coupled model developed herein,incorporating diffusion and adsorption/desorption across multi-level transport channels,effectively reproduces all the observed fractionation patterns and supports the mechanistic rationale for the combined effect.Finally,the potential carbon isotopic fractionation resulting from natural gas transport in/through porous media and its geological implications are discussed in several hypothetical scenarios combining numerical simulations.These findings highlight the limitations of carbon isotopic parameters for determining the origin and maturity of natural gas,and underscore their potential in identifying greenhouse gas leaks and tracing sources.
基金financially supported by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(No.2019QZKK0802)。
文摘Lack of information regarding lithium(Li)crystal chemistry in numerous minerals,especially those containing trace amounts of Li(ranging from a few to tens of ppm),limits our understanding of Li isotopic fractionation in pegmatites.In this study,we examined the Li isotopic composition and Li content in various Li-poor(e.g.,quartz or feldspar)together with Li-rich(sopdumene or lepidolite)mineral phases within granitic pegmatites.We compiled a comprehensive dataset,encompassing a broad spectrum of Li contents(ranging from a few to tens of thousands of ppm)and Li isotopic values(-8‰to 41‰).The minerals exhibit distinct Li isotopic signatures.Specifically,elbaite and beryl show the highest values,while biotite displays a negative average.Compared to individual minerals,whole rocks demonstrate lower Li isotopic values,with pegmatites exhibiting the highest and non-granitic pegmatite wall rocks showing the lowest.Our study also uncovers a clear“V”shape relationship between Li isotopic values and logarithm of Li contents,with different mineral groups occupying specific regions within this shape.Furthermore,a significant correlation was observed between average Li isotopic values and Li-O(OH,F)bond lengths in various minerals.These discoveries underscore the crucial role of crystal chemistry in shaping the Li isotopic behavior in pegmatites from a statistical perspective.
基金supported by Chinese NSF project(42,130,114)the strategic priority research program(B)of CAS(XDB41000000)the pre-research Project on Civil Aerospace Technologies No.D020202 funded by Chinese National Space Administration(CNSA)and Guizhou Provincial 2021 Science and Technology Subsidies(No.GZ2021SIG).
文摘Isotope eff ects are pivotal in understanding silicate melt evaporation and planetary accretion processes.Based on the Hertz-Knudsen equation,the current theory often fails to predict observed isotope fractionations of laboratory experiments due to its oversimplified assumptions.Here,we point out that the Hertz-Knudsen-equation-based theory is incomplete for silicate melt evaporation cases and can only be used for situations where the vaporized species is identical to the one in the melt.We propose a new model designed for silicate melt evaporation under vacuum.Our model considers multiple steps including mass transfer,chemical reaction,and nucleation.Our derivations reveal a kinetic isotopic fractionation factor(KIFF orα)αour model=[m(^(1)species)/m(^(2)species)]^(0.5),where m(species)is the mass of the reactant of reaction/nucleation-limiting step or species of diffusion-limiting step and superscript 1 and 2 represent light and heavy isotopes,respectively.This model can eff ectively reproduce most reported KIFFs of laboratory experiments for various elements,i.e.,Mg,Si,K,Rb,Fe,Ca,and Ti.And,the KIFF-mixing model referring that an overall rate of evaporation can be determined by two steps jointly can account for the eff ects of low P_(H2)pressure,composition,and temperature.In addition,we find that chemical reactions,diffusion,and nucleation can control the overall rate of evaporation of silicate melts by using the fitting slope in ln(−ln f)versus ln(t).Notably,our model allows for the theoretical calculations of parameters like activation energy(E_(a)),providing a novel approach to studying compositional and environmental eff ects on evaporation processes,and shedding light on the formation and evolution of the proto-solar and Earth-Moon systems.
基金This paper is supported by Chinese NSF project(42130114)the strategic priority research program(B)of CAS(XDB41000000)the pre-research Project on Civil Aerospace Technologies No.D020202 funded by Chinese National Space Administration(CNSA)。
文摘It is well-known that the equilibrium isotope fractionation of mercury(Hg)includes classical massdependent fractionations(MDFs)and nuclear volume effect(NVE)induced mass-independent fractionations(MIFs).However,the effect of the NVE on these kinetic processes is not known.The total fractionations(MDFs+NVEinduced MIFs)of several representative Hg-incorporated substances were selected and calculated with ab initio calculations in this work for both equilibrium and kinetic processes.NVE-induced MIFs were calculated with scaled contact electron densities at the nucleus through systematic evaluations of their accuracy and errors using the Gaussian09 and DIRAC19 packages(named the electron density scaling method).Additionally,the NVE-induced kinetic isotope effect(KIE)of Hg isotopes are also calculated with this method for several representative Hg oxidation reactions by chlorine species.Total KIEs for 202 Hg/^(198)Hg ranging from−2.27‰to 0.96‰are obtained.Three anomalous^(202)Hg-enriched KIEs(δ^(202)Hg/^(198)Hg=0.83‰,0.94‰,and 0.96‰,)caused by the NVE are observed,which are quite different from the classical view(i.e.,light isotopes react faster than the heavy ones).The electron density scaling method we developed in this study can provide an easier way to calculate the NVE-induced KIEs for heavy isotopes and serve to better understand the fractionation mechanisms of mercury isotope systems.
基金National Postdoctoral Innovative Talent Support Program(BX20220062)National Natural Science Foundation of China(41672130 and 41972123)SINOPEC Corp.(P17027-3)。
文摘The research progress of isotopic fractionation in the process of shale gas/coalbed methane migration has been reviewed from three aspects: characteristics and influencing factors, mechanism and quantitative characterization model, and geological application. It is found that the isotopic fractionation during the complete production of shale gas/coalbed methane shows a four-stage characteristic of “stable-lighter-heavier-lighter again”, which is related to the complex gas migration modes in the pores of shale/coal. The gas migration mechanisms in shale/coal include seepage, diffusion, and adsorption/desorption. Among them, seepage driven by pressure difference does not induce isotopic fractionation, while diffusion and adsorption/desorption lead to significant isotope fractionation. The existing characterization models of isotopic fractionation include diffusion fractionation model, diffusion-adsorption/desorption coupled model, and multi-scale and multi-mechanism coupled model. Results of model calculations show that the isotopic fractionation during natural gas migration is mainly controlled by pore structure, adsorption capacity, and initial/boundary conditions of the reservoir rock. So far, the isotope fractionation model has been successfully used to evaluate critical parameters, such as gas-in-place content and ratio of adsorbed/free gas in shale/coal etc. Furthermore, it has shown promising application potential in production status identification and decline trend prediction of gas well. Future research should focus on:(1) the co-evolution of carbon and hydrogen isotopes of different components during natural gas migration,(2) the characterization of isotopic fractionation during the whole process of gas generation-expulsion-migration-accumulation-dispersion, and(3) quantitative characterization of isotopic fractionation during natural gas migration in complex pore-fracture systems and its application.
基金Supported by National Natural Science Foundation of China(31172245)Major Agricultural Application Technology Innovation Project in Shandong Province(LCNZ[2014]38)~~
文摘[Objective] This study aimed to promote the combination of cultivation and livestock farming, and to explore an environment-protecting farming style. [Method]The effects of anaerobically fermented complete compound sow feed, added with Lactobacillus and Bacillus subtilis, on the chemical fractionation of copper, iron, zinc and manganese in feed and pig manure and skatole content in pig manure were investigated. [Result] Compared with those in the non-fermented feed, in the fermented feed and pig manure, the acetic acid-extractable copper, iron, zinc and manganese contents increased significantly（P0.05）, the reduced copper and iron contents increased significantly（P 0.05）, the oxidized copper and iron contents reduced significantly（P0.05）, and the residual copper contents remained unchangeable（P0.05）. The pH value of fermented feed decreased significantly（P0.05）, and that of pig manure increased significantly（P0.05）. The skatole content in pig manure decreased significantly（P 0.01）. The Lactobacillus abundance and amylase and cellulase activity increased significantly（P 0.05）. [Conclusion] The fermentation of feed changed the chemical fractionation of copper, iron, zinc and manganese in feed and pig manure, and reduced the manure odor.
基金funding support from the973 Program(2014CB440904)Chinese NSF projects(41225012,41490635,41530210)
文摘An anomalous isotope effect exists in many heavy element isotope systems （e.g., Sr, Gd, Zn, U）. This effect used to be called the ＂odd--even isotope effect＂ because the odd mass number isotopes behave differently from the even mass number isotopes. This mass-indepen- dent isotope fractionation driving force, which originates from the difference in the ground-state electronic energies caused by differences in nuclear size and shape, is cur- rently denoted as the nuclear field shift effect （NFSE）. It is found that the NFSE can drive isotope fractionation of some heavy elements （e.g., Hg, T1, U） to an astonishing degree, far more than the magnitude caused by the con- ventional mass-dependent effect （MDE）. For light ele- ments, the MDE is the dominant factor in isotope fractionation, while the NFSE is neglectable. Furthermore, the MDE and the NFSE both decrease as temperatures increase, though at different rates. The MDE decreases rapidly with a factor of 1/T2, while the NFSE decreases slowly with a factor of 1/T. As a result, even at high temperatures, the NFSE is still significant for many heavy element isotope systems. In this review paper, we begin with an introduction of the basic concept of the NSFE, including its history and recent progress, and follow with the potential implications of the inclusion of the NFSE into the kinetic isotope fractionation effect （KIE） and heavy isotope geochronology.
基金the funding supports from the strategic priority research program (B) of CAS (XDB18010100)Chinese NSF projects (Nos. 41530210, 41490635)
文摘Equilibrium isotope fractionation of thallium(Tl) includes the traditional mass-dependent isotope fractionation effect and the nuclear volume effect(NVE). The NVE dominates the overall isotope fractionation, especially at high temperatures. Heavy Tl isotopes tend to be enriched in oxidized Tl^3+-bearing species. Our NVE fractionation results of oxidizing Tl^+ to Tl^3+ can explain the positive enrichments observed in ferromanganese sediments. Experimental results indicate that there could be0.2–0.3 e-unit fractionation between sulfides and silicates at 1650 ℃. It is consistent with our calculation results,which are in the range of 0.17–0.38 e-unit. Importantly,Tl’s concentration in the bulk silicate Earth(BSE) can be used to constrain the amount of materials delivered to Earth during the late veneer accretion stage. Because the Tl concentration in BSE is very low and its Tl isotope composition is similar with that of chondrites, suggesting either no Tl isotope fractionation occurred during numerous evaporation events, or the Tl in current BSE was totally delivered by late veneer. If it is the latter, the Tl-contentbased estimation could challenge the magnitude of late veneer which had been constrained by the amount of highly siderophile elements in BSE. Our results show that the lateaccreted mass is at least five-times larger than the previously suggested magnitude, i.e., 0.5 wt% of current Earth’s mass. The slightly lighter 205 Tl composition of BSE relative to chondrites is probable a sign of occurrence of Tlbearing sulfides, which probably were removed from the mantle in the last accretion stage of the Earth.
基金support from973 Program Fund(No.2014CB440904)Chinese National Science Fund Projects(Nos.41530210,41490635,41403051)
文摘Equilibrium Zn isotope fractionation was inves- tigated using first-principles quantum chemistry methods at the B3LYP/6-311G level. The volume variable cluster model method was used to calculate isotope fractionation factors of sphalerite, smithsonite, calcite, anorthite, for- sterite, and enstatite. The water-droplet method was used to calculate Zn isotope fractionation factors of Zn^2＋-bearing aqueous species; their reduced partition function ratio factors decreased in the order [Zn（H2O）6]^2＋ 〉 [ZnCl（H2O）5]^ ＋ 〉 [ZnCl2（H2O）4] 〉 [ZnCl3（H20）2]^-〉 ZnCl4]^2-. Gas- eous ZnCl2 was also calculated for vaporization processes. Kinetic isotope fractionation of diffusional processes in a vacuum was directly calculated using formulas provided by Richter and co-workers. Our calculations show that in addition to the kinetic isotope effect of diffusional processes, equilibrium isotope fractionation also contributed nontriv- ially to observed Zn isotope fractionation of vaporization processes. The calculated net Zn isotope fractionation of vaporization processes was 7-7.5‰, with ZnCl2 as the gas- eous species. This matches experimental observations of the range of Zn isotope distribution of lunar samples. Therefore, vaporization processes may be the cause of the large distri- bution of Zn isotope signals found on the Moon. However, we cannot further distinguish the origin of such vaporization processes; it might be due either to igneous rock melting inmeteorite bombardments or to a giant impact event. Fur- thermore, isotope fractionation between Zn-bearing aqueous species and minerals that we have provided helps explain Zn isotope data in the fields of ore deposits and petrology.
基金financially supported by the Hebei Natural Sciences Foundation(Grant Nos.D2020402004 and D2021402020)Hebei Education Department Key Program(Grant No.ZD2018086)+1 种基金the State Natural Sciences Foundation(Grant No.41603011)Hebei University of Engineering Doctoral Special Program(Grant Nos.17129033019 and 17129033020)。
文摘The potential utilization and development of the Ba isotope tool depend on an accurateδ^(137/134)Ba determination of the samples.During the chemical purification,whether the adsorption process on the surface of the ionexchange resin could lead to the Ba isotopic fractionation and the degree of fractionation directly influence the accurateδ^(137/134)Ba determination.In the present work,first-principles calculations based on the density functional theory were used to quantify the Ba isotopic equilibrium fractionation factor between the aqueous solution and the resin in the acid leaching process.By constructing and optimizing the geometric configurations of Ba-containing species,Ba(H_(2)O)_(n)^(2+),Ba(H_(2)O)_(n)Cl_(2),Ba(H_(2)O)_(n)(NO_(3))2,and the adsorbed Ba^(2+)on the surface of the resin,extracting the harmonic vibrational frequencies,we finally at 298 K obtained the fractionations,Δ^(137/134)Ba_(soln-ads)=0.07‰,Δ^(137/134)Ba_(Ba(H_(2)O)_(n)Cl_(2)-ads)=0.05‰,andΔ^(137/134)-Ba^(Ba(H_(2)O)_(n)(NO_(3))2-ads)=0.02‰.Overall,there were almost no Ba isotope fractionations during leaching.Although the Ba isotope fractionation can be magnified by the Rayleigh fractionation process in purification,the difference inδ137/134Ba between the initial and final stages did not exceed0.060‰(or 0.045‰)when leaching the standard sample with HCl or HNO_(3),which is equal to or less than the accuracy of Ba isotopic analysis.At a common yield of89.75%,Ba isotopic fractionation induced by incomplete recovery was 0.015‰for HCl(or 0.011‰for HNO_(3)).Finally,if the influence of an incomplete recovery on theδ137/134Ba determination needs to be ignored,the recovery is suggested to be not less than 67%for HCl(or 46%for HNO_(3)).
基金The Grand Projects of Innovation Engineering Chinese Academy of Sciences(No. KZCX1 SW 12 2002 2006)
文摘Typical sediments from Taihu Lake, a meso-to-hypereutrophic lake, were collected and examined on the basis of P-fractionation by sequential extraction scheme. Sedimentary inorganic phosphorus were fractioned into four forms and the rank order according to the mean concentration of P-fractions in Taihu Lake was NaOH-P>BD-P>HCl-P>NH_4Cl-P. The concentrations of BD-P were linearly correlated with the content of active Fe(R2=0.96). Also, the linear relationship between the sum of BD-P and NaOH-P and the sum of active Fe and active Al content was observed within the six sediments investigated(R2=0.96). Moreover, the bio-available phosphorus(BAP) content was estimated by the sum of NH_4Cl-P, BD-P, and NaOH-P, viz. BAP=NH_4Cl-P+NaOH-P+BD-P. In Taihu Lake, the BAP contents are ranging from 0.10 mg/g dw to 1.25 mg/g dw, and average 0.40 mg/g dw for all sediment samples. The relative contributions of BAP to total sedimentary phosphorus(TP) and inorganic sedimentary phosphorus(IP) range from 18.67% to 50.79%(33.61% on average) and from 52.82% to 82.09%(67.81% on average), respectively.
基金supported by the National Basic Research Program (973) of China (No.2009CB426301)the National Natural Science Foundation of China (No.40773076,40703026)
文摘This work investigated the distribution and speciation of Cd, Cu, Pb, Fe and Mn in the shallow sediments of Jinzhou Bay, Northeast China, which has been heavily contaminated by nonferrous smelting activities. The concentrations of Cd, Cu and Pb in sediments were found to be 100, 13 and 7 times, respectively, being higher than the national guideline （GB 18668-2002）. Sequential extraction test showed that 39%-61% of Cd were exchangeable fractions, indicating that Cd in the sediments posed a high risk to local environments. While Cu and Pb were at moderate risk levels. According to the relationships between percentage of metal speciation and total metal concentration, it was concluded that the distributions of Cd, Cu and Pb in some geochemical fractions were dynamic in the process of pollutants migration and the stability of metals in sediments of Jinzhou Bay decreased in the order of Pb 〉 Cu 〉 Cd.
基金supported by the National Basic Research Program of China(973 Program) (2009CB421006)the State Key Laboratory of Geological Processes and Mineral Resources (GPMR200843)
文摘REE fractionation during the weathering of dolomite has been recognized for decades.A regolith profile on dolomite in southwest Yunnan of China was selected to investigate the behaviors of REE during weathering.The weathering of dolomite is divided into two stages：the pedogenesis stage and soil evolution stage,corresponding to the saprolites and soils respectively in the regolith profile. SiO_2,TiO_2,P_2O_5,Zr,Hf,Nb and Ta were immobile components during the weathering by and large, while Al_2O_3,K_2O and Fe_2O_3 were lost during the soil evolution stage in the physical form（clay minerals probably）.REE were fractionated during the whole weathering of dolomite.The field weathering profile and the lab acid-leaching experiments on dolomite indicate that MREE were enriched clearly relative to other REE during the pedogenesis stage in a ＂capillary ascending-adsorption＂ mechanism, but they did not fractionate clearly in the soil evolution stage.REE were lost and accumulated in the weathering front of dolomite during the soil evolution stage in a ＂physical-chemical leaching＂ mechanism.
