The gas desorbed from the dielectric surface has a great influence on the characteristics of microwave breakdown on the vacuum side of the dielectric window. In this paper, the dielectric surface breakdown is describe...The gas desorbed from the dielectric surface has a great influence on the characteristics of microwave breakdown on the vacuum side of the dielectric window. In this paper, the dielectric surface breakdown is described by using the electromagnetic particle-in-cell-Monte Carlo collision(PIC-MCC) model. The process of desorption of gas and its influence on the breakdown characteristics are studied. The simulation results show that, due to the accumulation of desorbed gas, the pressure near the dielectric surface increases in time, and the breakdown mechanism transitions from secondary electron multipactor to collision ionization. More and more electrons generated by collision ionization drift to the dielectric surface, so that the amplitude of self-organized normal electric field increases in time and sometimes points to the dielectric surface. Nevertheless, the number of secondary electrons emitted in each microwave cycle is approximately equal to the number of primary electrons. In the early and middle stages of breakdown, the attenuation of the microwave electric field near the dielectric surface is very small. However, the collision ionization causes a sharp increase in the number density of electrons,and the microwave electric field decays rapidly in the later stage of breakdown. Compared with the electromagnetic PIC-MCC simulation results, the mean energy and number of electrons obtained by the electrostatic PIC-MCC model are overestimated in the later stage of breakdown because it does not take into account the attenuation of microwave electric field. The pressure of the desorbed gas predicted by the electromagnetic PIC-MCC model is close to the measured value,when the number of gas atoms desorbed by an incident electron is taken as 0.4.展开更多
Volatile organic compounds(VOCs)are difficult to be eliminated safely and effectively because of their large concentration fluctuations.Thus,maintaining a stable concentration of VOCs is a significant study.In this re...Volatile organic compounds(VOCs)are difficult to be eliminated safely and effectively because of their large concentration fluctuations.Thus,maintaining a stable concentration of VOCs is a significant study.In this research,H2O,Tween-80,[Emim]BF4,[Emim]PF6,and[Hnmp]HSO4 were applied to absorb and desorb simulated VOCs.The ionic liquid[Emim]BF4 demonstrated the best performance and was thus selected for further experiments.As the ionic liquid acted as a buffer,the toluene concentration with a fluctuation of 2000–20000 mg·m-3 was stabilized at 6000–12000 mg·m-3.Heating distillation(90°C)was highly efficient to recover[Emim]BF4 from toluene.The regenerated[Emim]BF4 could retain its initial absorption capacity even after multiple cycles.Moreover,[Emim]BF4 had the same buffer function on various aromatic hydrocarbons.展开更多
The organic-rich shale of the Shanxi and Taiyuan Formation of the Lower Permian deposited in a marinecontinental transitional environment are well developed in the Ordos Basin,NW China,which is considered to contain a...The organic-rich shale of the Shanxi and Taiyuan Formation of the Lower Permian deposited in a marinecontinental transitional environment are well developed in the Ordos Basin,NW China,which is considered to contain a large amount of shale hydrocarbon resources.This study takes the Lower Permian Shanxi and Taiyuan shale collected from well SL~# in the Ordos Basin,NW China as an example to characterize the transitional shale reservoir.Based on organic geochemistry data,X-ray diffraction(XRD)analysis,field-emission scanning electron microscopy(FE-SEM)observations,the desorbed gas contents of this transitional shale were systematically studied and the shale gas potential was investigated.The results indicate that the Lower Permian Shanxi and Taiyuan shale has a relatively high total organic carbon(TOC)(average TOC of 4.9%)and contains type III kerogen with a high mature to over mature status.XRD analyses show that an important characteristic of the shale is that clay and brittle minerals of detrital origin comprise the major mineral composition of the marine-continental transitional shale samples,while the percentages of carbonate minerals,pyrite and siderite are relatively small.FE-SEM observations reveal that the mineral matrix pores are the most abundant in the Lower Permian shale samples,while organic matter(OM)pores are rarely developed.Experimental analysis suggests that the mineral compositions mainly govern the macropore development in the marine-continental transitional shale,and mineral matrix pores and microfractures are considered to provide space for gas storage and migration.In addition,the desorption experiments demonstrated that the marine-continental transitional shale in the Ordos Basin has a significantly potential for shale gas exploration,ranging from 0.53 to 2.86 m^3/t with an average value of 1.25m^3/t,which is in close proximity to those of terrestrial shale(1.29 m^3/t)and marine shale(1.28 m^3/t).In summary,these results demonstrated that the Lower Permian marine-continental transitional shale in the Ordos Basin has a significantly potential for shale gas exploration.展开更多
The electrochemical performance of double phase Mg Ni alloy was characterized at 25°C and 70°C, in order to evaluate briefly its utility as negative electrode materials in nickel metal hydride batteries. ...The electrochemical performance of double phase Mg Ni alloy was characterized at 25°C and 70°C, in order to evaluate briefly its utility as negative electrode materials in nickel metal hydride batteries. The results show that the electrochemical capacity of double phase Mg Ni alloy is rarely low at 25°C, but increased rapidly when the temperature is enhanced, and the double phase Mg Ni alloy has its maximum capacity at the first discharge cycle, but the capacity degrades rapidly with cycling number.展开更多
To understand the natural gas characteristics of multi-thin coal seam,this study selected the desorbed gas of coal seams in different layers of Well A in the Wujiu depression,Hailar Basin in northeast Inner Mongolia.T...To understand the natural gas characteristics of multi-thin coal seam,this study selected the desorbed gas of coal seams in different layers of Well A in the Wujiu depression,Hailar Basin in northeast Inner Mongolia.The results show that the heavy hydrocarbon content of desorbed gas increases significantly with the increasing depth.Methane carbon(δ13C_(1))and ethane carbon(δ13C_(2))isotope values are vertically become heavier downwards,while the δ13 values did not change significantly.The kerogen is close to the III–II mixed type with the source rocks mainly deposited in a shore/shallow lake or braided-river delta front,and the gas produced has certain characteristics of oil associated gas.However,the characteristics of oil associated gas produced by the organic formed in the shallow-water environment(braided-river delta plain)are not obvious.The sandstone pore and fracture systems interbedded with multi-thin coal seam are well developed.And it is conducive to the migration of methanogenic micro-organisms to coal seams via groundwater,making it easier to produce biogenic gas under this geological condition.During the burial evolution of coal-bearing strata in the study area,when the burial depth reaches the maximum,there are significant differences in the paleotemperature experienced by different vertical coal seams,caused by a high-paleogeothermal gradient,increasing the δ13C_(2) of desorbed gas with increasing depth.The above research indicates that there is less biogenic gas in the multi-thin coal seams with relatively developed mudstone,and the multi-thin coal seams with relatively developed sandstones have obvious biogenic gas characteristics.Therefore,for the exploration and development of biogenic gas in low-rank multi-thin coal seams,it is necessary to give priority to the layer with high sandstone content.展开更多
Mass-transfer studies of catalyst-aided CO_(2) absorption and desorption were performed in a full-cycle,bench-scale pilot plant to improve CO_(2) absorption using 5M MEA,5M MEA-2M MDEA and 2M BEA-2M AMP.A solid-base c...Mass-transfer studies of catalyst-aided CO_(2) absorption and desorption were performed in a full-cycle,bench-scale pilot plant to improve CO_(2) absorption using 5M MEA,5M MEA-2M MDEA and 2M BEA-2M AMP.A solid-base catalyst,K/MgO,and an acid catalyst,HZSM-5,were used to facilitate absorption and desorption,respectively.Absorption and desorption mass-transfer performance was presented in terms of the overall mass-transfer coefficient of the gas side(KGav)and liquid side(K_(L)a_(v)),respectively.For non-catalytic runs,the highest K_(G)a_(V) and K_(L)a_(V) were 0.086 Kmol m^(3).kPa.hr and 0.7851 hr for 2M BEA-2M AMP solvent.The results showed 38.7% KGav and 23.6% K_(L)a_(v) increase for 2M BEA-2M AMP with only HZSM-5 catalyst in desorber and a 95% K_(G)a_(V) and 45% K_(L)a_(V) increase for both K/MgO catalyst and HZSM-5 catalyst.This was attributed to the role of K/MgO in bonding loosely with CO_(2) and making it available for the amine reaction.展开更多
Analysis errors can occur in the desorbing process of ginkgo diterpene lactone meglumine injection(GDMI) by a conventional analysis method, due to several factors, such as easily crystallized samples, solvent volatili...Analysis errors can occur in the desorbing process of ginkgo diterpene lactone meglumine injection(GDMI) by a conventional analysis method, due to several factors, such as easily crystallized samples, solvent volatility, time-consuming sample pre-processing, fixed method, and offline analysis. Based on risk management, near-infrared(NIR) and mid-infrared(MIR) spectroscopy techniques were introduced to solve the above problems with the advantage of timely analysis and non-destructive nature towards samples. The objective of the present study was to identify the feasibility of using NIR or MIR spectroscopy techniques to increase the analysis accuracy of samples from the desorbing process of GDMI. Quantitative models of NIR and MIR were established based on partial least square method and the performances were calculated. Compared to NIR model, MIR model showed greater accuracy and applicability for the analysis of the GDMI desorbing solutions. The relative errors of the concentrations of Ginkgolide A(GA) and Ginkgolide B(GB) were 2.40% and 2.89%, respectively, which were less than 5.00%. The research demonstrated the potential of the MIR spectroscopy technique for the rapid and non-destructive quantitative analysis of the concentrations of GA and GB.展开更多
As one of the most widely distributed bacterial predators in the soil, the role of bacterivorous nematodes on the enhanced bioremediation of polycyclic aromatic hydrocarbon-contaminated soils is crucial, but remains t...As one of the most widely distributed bacterial predators in the soil, the role of bacterivorous nematodes on the enhanced bioremediation of polycyclic aromatic hydrocarbon-contaminated soils is crucial, but remains to be investigated.A microcosm-level study was conducted to examine the effects of bacterial-feeding nematode grazing and tea saponin(TS) addition on bioremediation of a pyrene-contaminated soil enhanced by the polycyclic aromatic hydrocarbon(PAH)-degrading bacterial strain Sphingobium sp.PHE9.After 180 d of incubation, the highest pyrene dissipation(71.3%) was achieved through a combination of Sphingobium sp.PHE9 inoculation with nematode and TS addition.Meanwhile, high counts of culturable PAH-degrading bacteria, soil enzyme activity, and biodiversity indices were observed under the combined treatment, implying that the microbiological function of the contaminated soil was significantly restored.Additionally, the results of Tenax~ extraction with the first-order three-compartment model indicated that rate-limiting factors varied among treatments.The lack of degrading microorganisms was the main rate-limiting factor for the treatments involving TS/nematode addition, and inadequate bioaccessible pyrene was the vital rate-limiting factor in the treatments involving Sphingobium sp.PHE9 inoculation.The proposed combined clean-up strategy proved to be a promising bioremediation technology for aged pyrene-contaminated soils.展开更多
Through analysis of components and carbon isotope compositions of gas desorbed from shale cores,the carbon isotope reversal phenomenon in the shale gas from the Silurian Longmaxi Formation of Jiaoshiba area in Sichuan...Through analysis of components and carbon isotope compositions of gas desorbed from shale cores,the carbon isotope reversal phenomenon in the shale gas from the Silurian Longmaxi Formation of Jiaoshiba area in Sichuan Basin were well studied.Results showed that compared with the wellhead gas,the desorbed gas from Longmaxi shale had significantly more wet components and more heavy carbon isotope values;carbon isotope values of each component became heavier with the desorption time,δ^(13)C_(1)values of different samples had maximum positive variations of 12.3-23.9‰,butδ^(13)C_(2)values only had maximum positive variations of 0.8e2.3‰,indicating carbon isotope values of methane changed more obviously than that of heavy hydrocarbon.The above results were consistent with previous results of shale core desorption experiments carried out by other researchers.Shale gas in strata might have no carbon isotope reversal,and the phenomenon thatδ^(13)C_(1)values changed more significantly thanδ^(13)C_(2)values during the core desorption was not caused by diffusion rate differences among different components,but mainly due to different desorption stages of methane and ethane,i.e.,the ethane was in its early desorption stage while the methane was in its later desorption stage;during the production process,phase differences among different components of alkane gas and differences in the desorption stages induced by adsorption,could be the major cause for total reversal of carbon isotopes of shale gas in Longmaxi Formation,but it also could not excluded that mixture of kerogen cracking gas and crude oil cracking gas probably had a partial or more major contribution to the carbon isotope reversal.展开更多
基金supported by the National Key Laboratory Foundation 2021-JCJQ-LB-006,China(No.6142411132116)the Natural Science Basic Research Program of Shaanxi Province,China(Nos.2023-JC-YB-512 and 2023-JC-YB-042)+1 种基金the Fundamental Research Funds for the Central Universities,China(No.ZYTS23075)the China Postdoctoral Science Foundation(No.2019M653545)。
文摘The gas desorbed from the dielectric surface has a great influence on the characteristics of microwave breakdown on the vacuum side of the dielectric window. In this paper, the dielectric surface breakdown is described by using the electromagnetic particle-in-cell-Monte Carlo collision(PIC-MCC) model. The process of desorption of gas and its influence on the breakdown characteristics are studied. The simulation results show that, due to the accumulation of desorbed gas, the pressure near the dielectric surface increases in time, and the breakdown mechanism transitions from secondary electron multipactor to collision ionization. More and more electrons generated by collision ionization drift to the dielectric surface, so that the amplitude of self-organized normal electric field increases in time and sometimes points to the dielectric surface. Nevertheless, the number of secondary electrons emitted in each microwave cycle is approximately equal to the number of primary electrons. In the early and middle stages of breakdown, the attenuation of the microwave electric field near the dielectric surface is very small. However, the collision ionization causes a sharp increase in the number density of electrons,and the microwave electric field decays rapidly in the later stage of breakdown. Compared with the electromagnetic PIC-MCC simulation results, the mean energy and number of electrons obtained by the electrostatic PIC-MCC model are overestimated in the later stage of breakdown because it does not take into account the attenuation of microwave electric field. The pressure of the desorbed gas predicted by the electromagnetic PIC-MCC model is close to the measured value,when the number of gas atoms desorbed by an incident electron is taken as 0.4.
基金Supported by the Zhejiang University Students Science and Technology Innovation Activity Plan Funding(No.2018R403078).
文摘Volatile organic compounds(VOCs)are difficult to be eliminated safely and effectively because of their large concentration fluctuations.Thus,maintaining a stable concentration of VOCs is a significant study.In this research,H2O,Tween-80,[Emim]BF4,[Emim]PF6,and[Hnmp]HSO4 were applied to absorb and desorb simulated VOCs.The ionic liquid[Emim]BF4 demonstrated the best performance and was thus selected for further experiments.As the ionic liquid acted as a buffer,the toluene concentration with a fluctuation of 2000–20000 mg·m-3 was stabilized at 6000–12000 mg·m-3.Heating distillation(90°C)was highly efficient to recover[Emim]BF4 from toluene.The regenerated[Emim]BF4 could retain its initial absorption capacity even after multiple cycles.Moreover,[Emim]BF4 had the same buffer function on various aromatic hydrocarbons.
基金This work was financially supported by the Chinese Academy of Sciences Key Project(Grant No.XDB10030404)the National key R&D Program of China(Grant No.2017YFA0604803)+1 种基金the National Natural Science Foundation of China(Grant Nos.41831176,41572350 and 41503049)the Key Laboratory Project of Gansu(Grant No.1309RTSA041).
文摘The organic-rich shale of the Shanxi and Taiyuan Formation of the Lower Permian deposited in a marinecontinental transitional environment are well developed in the Ordos Basin,NW China,which is considered to contain a large amount of shale hydrocarbon resources.This study takes the Lower Permian Shanxi and Taiyuan shale collected from well SL~# in the Ordos Basin,NW China as an example to characterize the transitional shale reservoir.Based on organic geochemistry data,X-ray diffraction(XRD)analysis,field-emission scanning electron microscopy(FE-SEM)observations,the desorbed gas contents of this transitional shale were systematically studied and the shale gas potential was investigated.The results indicate that the Lower Permian Shanxi and Taiyuan shale has a relatively high total organic carbon(TOC)(average TOC of 4.9%)and contains type III kerogen with a high mature to over mature status.XRD analyses show that an important characteristic of the shale is that clay and brittle minerals of detrital origin comprise the major mineral composition of the marine-continental transitional shale samples,while the percentages of carbonate minerals,pyrite and siderite are relatively small.FE-SEM observations reveal that the mineral matrix pores are the most abundant in the Lower Permian shale samples,while organic matter(OM)pores are rarely developed.Experimental analysis suggests that the mineral compositions mainly govern the macropore development in the marine-continental transitional shale,and mineral matrix pores and microfractures are considered to provide space for gas storage and migration.In addition,the desorption experiments demonstrated that the marine-continental transitional shale in the Ordos Basin has a significantly potential for shale gas exploration,ranging from 0.53 to 2.86 m^3/t with an average value of 1.25m^3/t,which is in close proximity to those of terrestrial shale(1.29 m^3/t)and marine shale(1.28 m^3/t).In summary,these results demonstrated that the Lower Permian marine-continental transitional shale in the Ordos Basin has a significantly potential for shale gas exploration.
文摘The electrochemical performance of double phase Mg Ni alloy was characterized at 25°C and 70°C, in order to evaluate briefly its utility as negative electrode materials in nickel metal hydride batteries. The results show that the electrochemical capacity of double phase Mg Ni alloy is rarely low at 25°C, but increased rapidly when the temperature is enhanced, and the double phase Mg Ni alloy has its maximum capacity at the first discharge cycle, but the capacity degrades rapidly with cycling number.
基金We would like to thank the National Natural Science Foundation of China(Grant Nos.42130802,42002193,and 42002186)researchers Yanqiu Zhang,Wutao Hu,Haitao Lin,and Fengchun Li from Inner Mongolia Coal Geology Bureau for their help in sample acquisition.
文摘To understand the natural gas characteristics of multi-thin coal seam,this study selected the desorbed gas of coal seams in different layers of Well A in the Wujiu depression,Hailar Basin in northeast Inner Mongolia.The results show that the heavy hydrocarbon content of desorbed gas increases significantly with the increasing depth.Methane carbon(δ13C_(1))and ethane carbon(δ13C_(2))isotope values are vertically become heavier downwards,while the δ13 values did not change significantly.The kerogen is close to the III–II mixed type with the source rocks mainly deposited in a shore/shallow lake or braided-river delta front,and the gas produced has certain characteristics of oil associated gas.However,the characteristics of oil associated gas produced by the organic formed in the shallow-water environment(braided-river delta plain)are not obvious.The sandstone pore and fracture systems interbedded with multi-thin coal seam are well developed.And it is conducive to the migration of methanogenic micro-organisms to coal seams via groundwater,making it easier to produce biogenic gas under this geological condition.During the burial evolution of coal-bearing strata in the study area,when the burial depth reaches the maximum,there are significant differences in the paleotemperature experienced by different vertical coal seams,caused by a high-paleogeothermal gradient,increasing the δ13C_(2) of desorbed gas with increasing depth.The above research indicates that there is less biogenic gas in the multi-thin coal seams with relatively developed mudstone,and the multi-thin coal seams with relatively developed sandstones have obvious biogenic gas characteristics.Therefore,for the exploration and development of biogenic gas in low-rank multi-thin coal seams,it is necessary to give priority to the layer with high sandstone content.
文摘Mass-transfer studies of catalyst-aided CO_(2) absorption and desorption were performed in a full-cycle,bench-scale pilot plant to improve CO_(2) absorption using 5M MEA,5M MEA-2M MDEA and 2M BEA-2M AMP.A solid-base catalyst,K/MgO,and an acid catalyst,HZSM-5,were used to facilitate absorption and desorption,respectively.Absorption and desorption mass-transfer performance was presented in terms of the overall mass-transfer coefficient of the gas side(KGav)and liquid side(K_(L)a_(v)),respectively.For non-catalytic runs,the highest K_(G)a_(V) and K_(L)a_(V) were 0.086 Kmol m^(3).kPa.hr and 0.7851 hr for 2M BEA-2M AMP solvent.The results showed 38.7% KGav and 23.6% K_(L)a_(v) increase for 2M BEA-2M AMP with only HZSM-5 catalyst in desorber and a 95% K_(G)a_(V) and 45% K_(L)a_(V) increase for both K/MgO catalyst and HZSM-5 catalyst.This was attributed to the role of K/MgO in bonding loosely with CO_(2) and making it available for the amine reaction.
基金supported by a grant from the National Ministry of Science and Technology(No.2013ZX09402203)
文摘Analysis errors can occur in the desorbing process of ginkgo diterpene lactone meglumine injection(GDMI) by a conventional analysis method, due to several factors, such as easily crystallized samples, solvent volatility, time-consuming sample pre-processing, fixed method, and offline analysis. Based on risk management, near-infrared(NIR) and mid-infrared(MIR) spectroscopy techniques were introduced to solve the above problems with the advantage of timely analysis and non-destructive nature towards samples. The objective of the present study was to identify the feasibility of using NIR or MIR spectroscopy techniques to increase the analysis accuracy of samples from the desorbing process of GDMI. Quantitative models of NIR and MIR were established based on partial least square method and the performances were calculated. Compared to NIR model, MIR model showed greater accuracy and applicability for the analysis of the GDMI desorbing solutions. The relative errors of the concentrations of Ginkgolide A(GA) and Ginkgolide B(GB) were 2.40% and 2.89%, respectively, which were less than 5.00%. The research demonstrated the potential of the MIR spectroscopy technique for the rapid and non-destructive quantitative analysis of the concentrations of GA and GB.
基金financially supported by the National Natural Science Foundation of China(Nos.41371263 and 41771350)the Fundamental Research Funds for the Central Universities of China(Nos.KYTZ201404 and Y0201700160)+3 种基金the Agricultural Science and Technology Innovation Fund of Jiangsu Province,China(No.CX(17)3047)the Agro-scientific Research in the Public Interest of China(No.201503121)the Environmental Protection Research Project in Jiangsu Province,China(No.2017005)the National Key Research and Development Program of China(Nos.2016YFD0200106 and 2016YFD0300908)
文摘As one of the most widely distributed bacterial predators in the soil, the role of bacterivorous nematodes on the enhanced bioremediation of polycyclic aromatic hydrocarbon-contaminated soils is crucial, but remains to be investigated.A microcosm-level study was conducted to examine the effects of bacterial-feeding nematode grazing and tea saponin(TS) addition on bioremediation of a pyrene-contaminated soil enhanced by the polycyclic aromatic hydrocarbon(PAH)-degrading bacterial strain Sphingobium sp.PHE9.After 180 d of incubation, the highest pyrene dissipation(71.3%) was achieved through a combination of Sphingobium sp.PHE9 inoculation with nematode and TS addition.Meanwhile, high counts of culturable PAH-degrading bacteria, soil enzyme activity, and biodiversity indices were observed under the combined treatment, implying that the microbiological function of the contaminated soil was significantly restored.Additionally, the results of Tenax~ extraction with the first-order three-compartment model indicated that rate-limiting factors varied among treatments.The lack of degrading microorganisms was the main rate-limiting factor for the treatments involving TS/nematode addition, and inadequate bioaccessible pyrene was the vital rate-limiting factor in the treatments involving Sphingobium sp.PHE9 inoculation.The proposed combined clean-up strategy proved to be a promising bioremediation technology for aged pyrene-contaminated soils.
基金This study was supported by the project of"Formation conditions and favorable zone evaluation of shale gas in the Lower Paleozoic of Sichuan Basin and its peripheral blocks"of Sinopec Science and Technology Division(No.P13129).
文摘Through analysis of components and carbon isotope compositions of gas desorbed from shale cores,the carbon isotope reversal phenomenon in the shale gas from the Silurian Longmaxi Formation of Jiaoshiba area in Sichuan Basin were well studied.Results showed that compared with the wellhead gas,the desorbed gas from Longmaxi shale had significantly more wet components and more heavy carbon isotope values;carbon isotope values of each component became heavier with the desorption time,δ^(13)C_(1)values of different samples had maximum positive variations of 12.3-23.9‰,butδ^(13)C_(2)values only had maximum positive variations of 0.8e2.3‰,indicating carbon isotope values of methane changed more obviously than that of heavy hydrocarbon.The above results were consistent with previous results of shale core desorption experiments carried out by other researchers.Shale gas in strata might have no carbon isotope reversal,and the phenomenon thatδ^(13)C_(1)values changed more significantly thanδ^(13)C_(2)values during the core desorption was not caused by diffusion rate differences among different components,but mainly due to different desorption stages of methane and ethane,i.e.,the ethane was in its early desorption stage while the methane was in its later desorption stage;during the production process,phase differences among different components of alkane gas and differences in the desorption stages induced by adsorption,could be the major cause for total reversal of carbon isotopes of shale gas in Longmaxi Formation,but it also could not excluded that mixture of kerogen cracking gas and crude oil cracking gas probably had a partial or more major contribution to the carbon isotope reversal.