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
Taking deep coal-rock gas in the Yulin and Daning-Jixian areas of the Ordos Basin,NW China,as the research object,full-diameter coal rock samples with different cleat/fracture development degrees from the Carboniferou...Taking deep coal-rock gas in the Yulin and Daning-Jixian areas of the Ordos Basin,NW China,as the research object,full-diameter coal rock samples with different cleat/fracture development degrees from the Carboniferous Benxi Formation were selected to conduct physical simulation and isotope monitoring experiments of the full-life-cycle depletion development of coal-rock gas.Based on the experimental results,a dual-medium carbon isotope fractionation(CIF)model coupling cleats/fractures and matrix pores was constructed,and an evaluation method for free gas production patterns was established to elucidate the carbon isotope fractionation mechanism and adsorbed/free gas production characteristics during deep coal-rock gas development.The results show that the deep coal-rock gas development process exhibits a three-stage carbon isotope fractionation pattern:“Stable(Ⅰ)→Decrease(Ⅱ)→Increase(Ⅲ)”.A rapid decline in boundary pressure in stageⅢleads to fluctuations in isotope value,characterized by a“rapid decrease followed by continued increase”,with free gas being produced first and long-term supply of adsorbed gas.The CIF model can effectively match measured gas pressure,cumulative gas production,and δ^(13)C_(1) value of produced gas.During the first two stages of isotope fractionation,free gas dominated cumulative production.During the mid-late stages of slow depletion production,the staged pressure control development method can effectively increase the gas recovery.The production of adsorbed gas is primarily controlled by the rock's adsorption capacity and the presence of secondary flow channels.Effectively enhancing the recovery of adsorbed gas during the late stage remains crucial for maintaining stable production and improving the ultimate recovery factor of deep coal-rock gas.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
Carbon isotope fractionation served as a key geochemical indicator for understanding shale gas storage and migration.However,the detailed mechanism of the fractionation behaviors of methane isotopes(^(12)CH_(4)/^(13)C...Carbon isotope fractionation served as a key geochemical indicator for understanding shale gas storage and migration.However,the detailed mechanism of the fractionation behaviors of methane isotopes(^(12)CH_(4)/^(13)CH_(4))was still limited,especially under two-phase flow.This study employed molecular dynamics(MD)simulations to investigate water-mediated nonlinear isotope transport in 3 nm hydrophilic silica nanopores,highlighting gas-liquid-solid interfacial effects on fractionation mechanisms.Simulations of different water saturation(0%-44.66%)showed a critical hydration threshold of 30.44%at a pressure gradient of 20 MPa.Below this threshold,continuous water film formed on pore walls,which transformed the gas transport from surface diffusion to viscous flow through gas-liquid interactions,while hydrogen bonds in the water film weakened gas-solid slip effects.However,when water saturation exceeded 30.44%,the formation of water bridges blocked the mobility of isotopic gases.The water film reduced the depth of solid-gas potential wells,leading to diminished adsorption capacity for isotopic gases,and lowered the surface roughness of pore walls(as characterized by potential energy surface,PES).Additionally,the water film enhanced the Knudsen diffusion effect of isotope gases due to the decrease in effective pore size.As a result,the formation of water film intensified methane isotopic fractionation,which was manifested as a decrease in the^(13)CH_(4)/^(12)CH_(4)diffusion coefficient ratio(D∗/D)from 0.975 to 0.942 and an increase in isotopic enthalpy differences(Δh_(^(12)C)_^(13)C) from 0.105 to 1.139 J/m^(3).Furthermore,in the gas-liquid-solid interfacial system,an elevated pressure differential modified the relative motion velocities among the methane-water-pore surface,resulting a non-monotonic isotopic fractionation trend(initial increase followed by decrease).These findings provided molecular-level insights into the complex isotopic fractionation in shale gas systems.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Youth Fund of National Natural Science Foundation of China(42302170)CNPC Scientific and Technological Innovation Fund(2022DQ02-0104)RIPED Open Project Fund(2024-KFKT-31).
文摘Taking deep coal-rock gas in the Yulin and Daning-Jixian areas of the Ordos Basin,NW China,as the research object,full-diameter coal rock samples with different cleat/fracture development degrees from the Carboniferous Benxi Formation were selected to conduct physical simulation and isotope monitoring experiments of the full-life-cycle depletion development of coal-rock gas.Based on the experimental results,a dual-medium carbon isotope fractionation(CIF)model coupling cleats/fractures and matrix pores was constructed,and an evaluation method for free gas production patterns was established to elucidate the carbon isotope fractionation mechanism and adsorbed/free gas production characteristics during deep coal-rock gas development.The results show that the deep coal-rock gas development process exhibits a three-stage carbon isotope fractionation pattern:“Stable(Ⅰ)→Decrease(Ⅱ)→Increase(Ⅲ)”.A rapid decline in boundary pressure in stageⅢleads to fluctuations in isotope value,characterized by a“rapid decrease followed by continued increase”,with free gas being produced first and long-term supply of adsorbed gas.The CIF model can effectively match measured gas pressure,cumulative gas production,and δ^(13)C_(1) value of produced gas.During the first two stages of isotope fractionation,free gas dominated cumulative production.During the mid-late stages of slow depletion production,the staged pressure control development method can effectively increase the gas recovery.The production of adsorbed gas is primarily controlled by the rock's adsorption capacity and the presence of secondary flow channels.Effectively enhancing the recovery of adsorbed gas during the late stage remains crucial for maintaining stable production and improving the ultimate recovery factor of deep coal-rock gas.
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support from the National Natural Science Foundation of China,China(Grant 51776132)the Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process of the Ministry of Education(China University of Mining and Technology)(No.2024-007).
文摘Carbon isotope fractionation served as a key geochemical indicator for understanding shale gas storage and migration.However,the detailed mechanism of the fractionation behaviors of methane isotopes(^(12)CH_(4)/^(13)CH_(4))was still limited,especially under two-phase flow.This study employed molecular dynamics(MD)simulations to investigate water-mediated nonlinear isotope transport in 3 nm hydrophilic silica nanopores,highlighting gas-liquid-solid interfacial effects on fractionation mechanisms.Simulations of different water saturation(0%-44.66%)showed a critical hydration threshold of 30.44%at a pressure gradient of 20 MPa.Below this threshold,continuous water film formed on pore walls,which transformed the gas transport from surface diffusion to viscous flow through gas-liquid interactions,while hydrogen bonds in the water film weakened gas-solid slip effects.However,when water saturation exceeded 30.44%,the formation of water bridges blocked the mobility of isotopic gases.The water film reduced the depth of solid-gas potential wells,leading to diminished adsorption capacity for isotopic gases,and lowered the surface roughness of pore walls(as characterized by potential energy surface,PES).Additionally,the water film enhanced the Knudsen diffusion effect of isotope gases due to the decrease in effective pore size.As a result,the formation of water film intensified methane isotopic fractionation,which was manifested as a decrease in the^(13)CH_(4)/^(12)CH_(4)diffusion coefficient ratio(D∗/D)from 0.975 to 0.942 and an increase in isotopic enthalpy differences(Δh_(^(12)C)_^(13)C) from 0.105 to 1.139 J/m^(3).Furthermore,in the gas-liquid-solid interfacial system,an elevated pressure differential modified the relative motion velocities among the methane-water-pore surface,resulting a non-monotonic isotopic fractionation trend(initial increase followed by decrease).These findings provided molecular-level insights into the complex isotopic fractionation in shale gas systems.
