Anaerobic oxidation of methane(AOM) is an important biogeochemical process, which has important scientific significance for global climate change and atmospheric evolution. This research examined the δ^(34)S, terrige...Anaerobic oxidation of methane(AOM) is an important biogeochemical process, which has important scientific significance for global climate change and atmospheric evolution. This research examined the δ^(34)S, terrigenous clastic indices of TiO_(2) and Al_(2)O_(3), and times for formation of the Ba front at site SH1, site SH3 and site 973-4 in the South China Sea. Three different coupling mechanisms of deposition rate and methane flux were discovered. The different coupling mechanisms had different effects on the role of AOM. At site 973-4, a high deposition rate caused a rapid vertical downward migration of the sulphate–methane transition zone(SMTZ), and the higher input resulted in mineral dissolution. At site SH3, the deposition rate and methane flux were basically in balance,so the SMTZ and paleo-SMTZ were the most stable of any site, and these were in a slow process of migration. At site SH1, the methane flux dominated the coupled mode, so the movement of the SMTZ at site SH1 was consistent with the general understanding. Understanding the factors influencing the SMTZ is important for understanding the early diagenesis process.展开更多
Microplastics(MPs)are important exempla of the Anthropocene and are exerting an increasing impact on Earth’s carbon cycle.The huge imbalance between the MPs floating on the marine surface and those that are estimated...Microplastics(MPs)are important exempla of the Anthropocene and are exerting an increasing impact on Earth’s carbon cycle.The huge imbalance between the MPs floating on the marine surface and those that are estimated to have been introduced into the ocean necessitates a detailed assessment of marine MP sinks.Here,we demonstrate that cold seep sediments,which are characterized by methane fluid seepage and a chemosynthetic ecosystem,effectively capture and accommodate small-scale(<100μm)MPs,with 16 types of MPs being detected.The abundance of MPs in the surface of the sediment is higher in methane-seepage locations than in non-seepage areas.Methane seepage is beneficial to the accumulation,fragmentation,increased diversity,and aging of MPs.In turn,the rough surfaces of MPs contribute to the sequestration of the electron acceptor ferric oxide,which is associated with the anaerobic oxidation of methane(AOM).The efficiency of the AOM determines whether the seeping methane(which has a greenhouse effect 83 times greater than that of CO_(2)over a 20-year period)can enter the atmosphere,which is important to the global methane cycle,since the deep-sea environment is regarded as the largest methane reservoir associated with natural gas hydrates.展开更多
Specific management of water regimes, soil and N in China might play an important role in regulating N2O and CH4 emissions in rice fields. Nitrous oxide and methane emissions from alternate non-flooded/flooded paddies...Specific management of water regimes, soil and N in China might play an important role in regulating N2O and CH4 emissions in rice fields. Nitrous oxide and methane emissions from alternate non-flooded/flooded paddies were monitored simultaneously during a 516-day incubation with lysimeter experiments. Two N sources (15N-(NH4)2SO4 and 15N-labeled milk vetch) were applied to two contrasting paddies: one derived from Xiashu loess (Loess) and one from Quaternary red clay (Clay). Both N2O and CH4 emissions were significantly higher in soil Clay than in soil Loess during the flooded period. For both soil, N2O emissions peaked at the transition periods shortly after the beginning of the flooded and non-flooded seasons. Soil type affected N2O emission patterns. In soil Clay, the emission peak during the transition period from non-flooded to flooded conditions was much higher than the peak during the transition period from flooded to non-flooded conditions. In soil Loess, the emission peak during the transition period from flooded to non-flooded conditions was obviously higher than the peak during the transition period from non-flooded to flooded conditions except for milk vetch treatment. Soil type also had a significant effect on CH4 emissions during the flooded season, over which the weighted average flux was 111 mg C m-2 h-1 and 2.2 mg C m-2 h-1 from Clay and Loess, respectively. Results indicated that it was the transition in the water regime that dominated N2O emissions while it was the soil type that dominated CH4 emissions during the flooded season. Anaerobic oxidation of methane possibly existed in soil Loess during the flooded season.展开更多
Anaerobic oxidation of methane(AOM) plays a crucial role in controlling global methane emission. This is a microbial process that relies on the reduction of external electron acceptors such as sulfate, nitrate/nitrite...Anaerobic oxidation of methane(AOM) plays a crucial role in controlling global methane emission. This is a microbial process that relies on the reduction of external electron acceptors such as sulfate, nitrate/nitrite, and transient metal ions. In marine settings, the dominant electron acceptor for AOM is sulfate, while other known electron acceptors are transient metal ions such as iron and manganese oxides. Despite the AOM process coupled with sulfate reduction being relatively well characterized,researches on metal-dependent AOM process are few, and no microorganism has to date been identified as being responsible for this reaction in natural marine environments. In this review, geochemical evidences of metal-dependent AOM from sediment cores in various marine environments are summarized. Studies have showed that iron and manganese are reduced in accordance with methane oxidation in seeps or diffusive profiles below the methanogenesis zone. The potential biochemical basis and mechanisms for metal-dependent AOM processes are here presented and discussed. Future research will shed light on the microbes involved in this process and also on the molecular basis of the electron transfer between these microbes and metals in natural marine environments.展开更多
Anaerobic sludge from a sewage treatment plant was used to acclimatize microbial colonies capable of anaerobic oxidation of methane(AOM) coupled to sulfate reduction. Clone libraries and fluorescence in situ hybridiza...Anaerobic sludge from a sewage treatment plant was used to acclimatize microbial colonies capable of anaerobic oxidation of methane(AOM) coupled to sulfate reduction. Clone libraries and fluorescence in situ hybridization were used to investigate the microbial population.Sulfate-reducing bacteria(SRB)(e.g., Desulfotomaculum arcticum and Desulfobulbus propionicus)and anaerobic methanotrophic archaea(ANME)(e.g., Methanosaeta sp. and Methanolinea sp.)coexisted in the enrichment. The archaeal and bacterial cells were randomly or evenly distributed throughout the consortia. Accompanied by sulfate reduction, methane was oxidized anaerobically by the consortia of methane-oxidizing archaea and SRB. Moreover, CH_4 and SO_4^(2-) were consumed by methanotrophs and sulfate reducers with CO_2 and H_2S as products. The H_3CSH produced by methanotrophy was an intermediate product during the process. The methanotrophic enrichment was inoculated in a down-flow biofilter for the treatment of methane and H_2S from a landfill site. On average, 93.33% of H_2S and 10.71% of methane was successfully reduced in the biofilter. This study tries to provide effective method for the synergistic treatment of waste gas containing sulfur compounds and CH_4.展开更多
The denitrifying anaerobic methane oxidation is an ecologically important process for reducing the potential methane emission into the atmosphere.The responsible bacterium for this process was Candidatus Methylomirabi...The denitrifying anaerobic methane oxidation is an ecologically important process for reducing the potential methane emission into the atmosphere.The responsible bacterium for this process was Candidatus Methylomirabilis oxyfera belonging to the bacterial phylum of NC10.In this study,a new pair of primers targeting all the five groups of NC10 bacteria was designed to amplify NC10 bacteria from different environmental niches.The results showed that the group A was the dominant NC10 phylum bacteria from the sludges and food waste digestate while in paddy soil samples,group A and group B had nearly the same proportion.Our results also indicated that NC10 bacteria could exist in a high p H environment（pH 9.24）from the food waste treatment facility.The Pearson relationship analysis showed that the p H had a significant positive relationship with the NC10 bacterial diversity（p0.05）.The redundancy analysis further revealed that the p H,volatile solid and nitrite nitrogen were the most important factors in shaping the NC10 bacterial structure（p=0.01）based on the variation inflation factors selection and Monte Carlo test（999 times）.Results of this study extended the existing molecular tools for studying the NC10 bacterial community structures and provided new information on the ecological distributions of NC10 bacteria.展开更多
Anaerobic digestion is widely used in the treatment of industrial wastewater,excess activated sludge,municipal waste,crop straw and livestock manure,with the functions of environmental protection and energy recovery. ...Anaerobic digestion is widely used in the treatment of industrial wastewater,excess activated sludge,municipal waste,crop straw and livestock manure,with the functions of environmental protection and energy recovery. This review summarizes and evaluates the present knowledge of effects of different states of Fe( ZVI,Fe( II),Fe( III)) on hydrogen and methane production in anaerobic digestion process. The potential promotion effects of iron oxides nanoparticles( IONPs),especially magnetite nanoparticles on anaerobic digestion are also mentioned. Fe plays important role in transporting electron,stimulating bacterial growth and increasing hydrogen and methane production rate by promoting enzyme activity. Adding Fe with different morphologies and valence states in anaerobic digestion to increase biogas( hydrogen and methane) production and enhance organic matter degradation simultaneously,which has attracted many scientists' attention in recent years. Rapid progress in this area has been made over the last few years,since Fe is essential to the fermentative hydrogen and methane production,while few is known about how Fe affects the fermentative biogas production. This review is significant to maintain the stable operation of the biogas project.展开更多
Recent studies have shown that specific geochemical characteristics of sediments can be used to reconstruct past methane seepage events.In this work,the correlation between the Sr/Ca and Mg/Ca ratios of sediment sampl...Recent studies have shown that specific geochemical characteristics of sediments can be used to reconstruct past methane seepage events.In this work,the correlation between the Sr/Ca and Mg/Ca ratios of sediment samples is analyzed and the sulfate concentration profile in Site C14 from cold-seep sediments in the Qiongdongnan Basin in northern South China Sea is obtained.The results confirmed that,sulfate at 0–247 cm below sea floor(Unit I)is mainly consumed by organic matter sulfate reduction(OSR),while sulfate at 247–655 cm(UnitⅡ)is consumed by both the OSR and the anaerobic oxidation of methane(AOM).In addition,the bottom sediment layer is affected by weak methane seepage.The Mo and U enrichment factors also exhibit similar trends in their respective depth profiles.The responses of trace elements,including Co/Al,Ni/Al,Cr/Al and Zn/Al ratios to methane seepage allowed the study of depositional conditions and methane seepage events.Based on the results,it is speculated that the depositional conditions of UnitⅡchanged with depth from moderate conditions of sulfidic and oxic conditions to locally anoxic conditions,and finally to suboxic conditions due to methane fluid leakage.The stable isotope values of chromium-reducible sulfide produced by AOM and those of sulfide formed by OSR in the early diagenetic environment suffered serious depletion of 34S.This was probably due to weak methane leakage,which caused the slower upward diffusion and the effect of early diagenesis on the samples.It is necessary to consider the effects of depositional environments and diagenesis on these geochemical parameters.展开更多
The concentrations of CH4 and SO42? in pore-water and the carbon isotope compositions of total dissolved inorganic (ΣCO2) and CH4 were de- termined for three coastal sedimentary cores col- lected from Qi’ao Island (...The concentrations of CH4 and SO42? in pore-water and the carbon isotope compositions of total dissolved inorganic (ΣCO2) and CH4 were de- termined for three coastal sedimentary cores col- lected from Qi’ao Island (Pearl River Estuary), southern China. Results show that methane concen- tration changes dramatically at the base of the sul- fate-reducing zone and sulfate concentration gradi- ents are linear for all stations. In addition, the carbon isotope of methane becomes heavier at the sul- fate-methane transition (SMT), which causes ΣCO2-δ 13C to become the minimum. The geo- chemical profiles of pore-water render indirect evi- dence for anaerobic oxidation of methane (AOM). Based on numerical modeling of AOM and sul- fate-reducing rates, the portion of total sulfate reduc- tion occurring via AOM is 9.0%, 84% and 45.5%, re- spectively, and the percentage of ΣCO2 added to the pore-water is 4.7%, 72.4% and 29.45% correspond- ingly for three sites. Furthermore, it is found that the methane concentration, methane diffusive flux and the depth of SMT are controlled by the quantity and quality of sedimentary organic matter incorporated into the sediments. The great amount of organic material is favorable for rapid depletion of sulfate via sedimentary organic matter degradation, and on the other hand, causes the increase of the methane flux in the SMT, which results in a portion of sulfate re-duction supported by AOM. Accordingly, the SMT was shifted towards the sediment surface.展开更多
Cold seeps are pervasive along the continental margin worldwide,and are recognized as hotspots for elemental cycling pathway on Earth.In this study,analyses of pore water geochemical compositions of one-400 cm piston ...Cold seeps are pervasive along the continental margin worldwide,and are recognized as hotspots for elemental cycling pathway on Earth.In this study,analyses of pore water geochemical compositions of one-400 cm piston core(S3)and the application of a mass balance model are conducted to assess methane-associated biogeochemical reactions and uncover the relationship of methane in shallow sediment with gas hydrate reservoir at the Makran accretionary wedge off Pakistan.The results revealed that approximately 77%of sulfate is consumed by the predominant biogeochemical process of anaerobic oxidation of methane.However,the estimated sulfate-methane interface depth is-400 cm below sea floor with the methane diffusive flux of 0.039 mol/(m^(2)·a),suggesting the activity of methane seepage.Based on the δ^(13)C_(DIC) mass balance model combined with the contribution proportion of different dissolved inorganic carbon sources,this study calculated the δ^(13)C of the exogenous methane to be-57.9‰,indicating that the exogenous methane may be a mixture source,including thermogenic and biogenic methane.The study of pore water geochemistry at Makran accretionary wedge off Pakistan may have considerable implications for understanding the specific details on the dynamics of methane in cold seeps and provide important evidence for the potential occurrence of subsurface gas hydrate in this area.展开更多
The biological removal of CH4 by methanotrophic(CH4-oxidizing)archaea always occurs at a distinct zone which is known as sulfate-methane transition zone(SMTZ).It is an important indication for high methane flux and ga...The biological removal of CH4 by methanotrophic(CH4-oxidizing)archaea always occurs at a distinct zone which is known as sulfate-methane transition zone(SMTZ).It is an important indication for high methane flux and gas hydrate occurrence.In this study,we collected pore-water data from South China Sea,Carolina Rise and Blake Ridge to analyze the relationship between CH4,SO42−concentration and depth.We found that below the SMTZ,the methane concentration increases continuously with depth and sulfate concentration decrease linearly to zero.In addition,the geochemical data taken from all these sites show that SMTZ is relatively shallow(less than 20 m),which may indicate that these areas have high methane flux.展开更多
Low organic matter content and high heavy metal levels severely inhibit the anaerobic digestion(AD) of sewage sludge. In this study, the effect of added manganese oxidemodified biochar composite(MBC) on methane produc...Low organic matter content and high heavy metal levels severely inhibit the anaerobic digestion(AD) of sewage sludge. In this study, the effect of added manganese oxidemodified biochar composite(MBC) on methane production and heavy metal fractionation during sewage sludge AD was examined. The MBC could increase the buffering capacity,enhance the methane production and degradation of intermediate acids, buffer the pH of the culture, and stabilize the sewage sludge AD process. The application of MBC positively impacted methane production and the cumulative methane yield increased up to 121.97%,as compared with the control. The MBC addition can improve metal stabilization in the digestate. An optimum MBC dose of 2.36 g was recommended, which would produce up to 121.1 L/kg volatile solids of methane. After the AD process, even though most of the metals accumulated in the residual solids, they could be transformation from the bio-available fractions to a more stable fraction. The total organic-and sulfide-bound and residual fraction content at a 3 g dose of MBC that is 0.12 g/g dry matter were 51.06% and 35.11% higher than the control, respectively. The results indicated that the application of MBC could improve the performance of AD and promote stabilization of heavy metals in sewage sludge post the AD process.展开更多
基金The Guangdong Basic and Applied Basic Research Fund Project under contract No.2021A1515011509the Municipal Science and Technology Program of Guangzhou under contract No.201904010311the Special Project for Marine Economy Development of Guangdong Province under contract No.GDME-2018D002。
文摘Anaerobic oxidation of methane(AOM) is an important biogeochemical process, which has important scientific significance for global climate change and atmospheric evolution. This research examined the δ^(34)S, terrigenous clastic indices of TiO_(2) and Al_(2)O_(3), and times for formation of the Ba front at site SH1, site SH3 and site 973-4 in the South China Sea. Three different coupling mechanisms of deposition rate and methane flux were discovered. The different coupling mechanisms had different effects on the role of AOM. At site 973-4, a high deposition rate caused a rapid vertical downward migration of the sulphate–methane transition zone(SMTZ), and the higher input resulted in mineral dissolution. At site SH3, the deposition rate and methane flux were basically in balance,so the SMTZ and paleo-SMTZ were the most stable of any site, and these were in a slow process of migration. At site SH1, the methane flux dominated the coupled mode, so the movement of the SMTZ at site SH1 was consistent with the general understanding. Understanding the factors influencing the SMTZ is important for understanding the early diagenesis process.
基金financially supported by the National Natural Science Foundation of China(42022046)the National Key Research and Development Program of China(2021YFF0502300)+1 种基金the Key Special Project for Introduced Talent Teams of the Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(GML2019ZD0403 and GML2019ZD0401)Guangdong Natural Resources Foundation(GDNRC[2022]45)。
文摘Microplastics(MPs)are important exempla of the Anthropocene and are exerting an increasing impact on Earth’s carbon cycle.The huge imbalance between the MPs floating on the marine surface and those that are estimated to have been introduced into the ocean necessitates a detailed assessment of marine MP sinks.Here,we demonstrate that cold seep sediments,which are characterized by methane fluid seepage and a chemosynthetic ecosystem,effectively capture and accommodate small-scale(<100μm)MPs,with 16 types of MPs being detected.The abundance of MPs in the surface of the sediment is higher in methane-seepage locations than in non-seepage areas.Methane seepage is beneficial to the accumulation,fragmentation,increased diversity,and aging of MPs.In turn,the rough surfaces of MPs contribute to the sequestration of the electron acceptor ferric oxide,which is associated with the anaerobic oxidation of methane(AOM).The efficiency of the AOM determines whether the seeping methane(which has a greenhouse effect 83 times greater than that of CO_(2)over a 20-year period)can enter the atmosphere,which is important to the global methane cycle,since the deep-sea environment is regarded as the largest methane reservoir associated with natural gas hydrates.
基金Project supported by the National Natural Science Foundation of China (Nos. 30390080 and 30390081).
文摘Specific management of water regimes, soil and N in China might play an important role in regulating N2O and CH4 emissions in rice fields. Nitrous oxide and methane emissions from alternate non-flooded/flooded paddies were monitored simultaneously during a 516-day incubation with lysimeter experiments. Two N sources (15N-(NH4)2SO4 and 15N-labeled milk vetch) were applied to two contrasting paddies: one derived from Xiashu loess (Loess) and one from Quaternary red clay (Clay). Both N2O and CH4 emissions were significantly higher in soil Clay than in soil Loess during the flooded period. For both soil, N2O emissions peaked at the transition periods shortly after the beginning of the flooded and non-flooded seasons. Soil type affected N2O emission patterns. In soil Clay, the emission peak during the transition period from non-flooded to flooded conditions was much higher than the peak during the transition period from flooded to non-flooded conditions. In soil Loess, the emission peak during the transition period from flooded to non-flooded conditions was obviously higher than the peak during the transition period from non-flooded to flooded conditions except for milk vetch treatment. Soil type also had a significant effect on CH4 emissions during the flooded season, over which the weighted average flux was 111 mg C m-2 h-1 and 2.2 mg C m-2 h-1 from Clay and Loess, respectively. Results indicated that it was the transition in the water regime that dominated N2O emissions while it was the soil type that dominated CH4 emissions during the flooded season. Anaerobic oxidation of methane possibly existed in soil Loess during the flooded season.
基金supported by the National Natural Science Foundation of China (91751205, 41525011)the National Key R&D project of China (2018YFC0310800)+1 种基金China Postdoctoral Science Foundation Grant (2018T110390)the joint Israel Science Foundation-National Natural Science Foundation of China (ISF-NSFC) (31661143022 (FW), 2561/16 (OS))
文摘Anaerobic oxidation of methane(AOM) plays a crucial role in controlling global methane emission. This is a microbial process that relies on the reduction of external electron acceptors such as sulfate, nitrate/nitrite, and transient metal ions. In marine settings, the dominant electron acceptor for AOM is sulfate, while other known electron acceptors are transient metal ions such as iron and manganese oxides. Despite the AOM process coupled with sulfate reduction being relatively well characterized,researches on metal-dependent AOM process are few, and no microorganism has to date been identified as being responsible for this reaction in natural marine environments. In this review, geochemical evidences of metal-dependent AOM from sediment cores in various marine environments are summarized. Studies have showed that iron and manganese are reduced in accordance with methane oxidation in seeps or diffusive profiles below the methanogenesis zone. The potential biochemical basis and mechanisms for metal-dependent AOM processes are here presented and discussed. Future research will shed light on the microbes involved in this process and also on the molecular basis of the electron transfer between these microbes and metals in natural marine environments.
基金financially supported by the National Natural Science Foundation of China (Nos.51478456 and 51178451)
文摘Anaerobic sludge from a sewage treatment plant was used to acclimatize microbial colonies capable of anaerobic oxidation of methane(AOM) coupled to sulfate reduction. Clone libraries and fluorescence in situ hybridization were used to investigate the microbial population.Sulfate-reducing bacteria(SRB)(e.g., Desulfotomaculum arcticum and Desulfobulbus propionicus)and anaerobic methanotrophic archaea(ANME)(e.g., Methanosaeta sp. and Methanolinea sp.)coexisted in the enrichment. The archaeal and bacterial cells were randomly or evenly distributed throughout the consortia. Accompanied by sulfate reduction, methane was oxidized anaerobically by the consortia of methane-oxidizing archaea and SRB. Moreover, CH_4 and SO_4^(2-) were consumed by methanotrophs and sulfate reducers with CO_2 and H_2S as products. The H_3CSH produced by methanotrophy was an intermediate product during the process. The methanotrophic enrichment was inoculated in a down-flow biofilter for the treatment of methane and H_2S from a landfill site. On average, 93.33% of H_2S and 10.71% of methane was successfully reduced in the biofilter. This study tries to provide effective method for the synergistic treatment of waste gas containing sulfur compounds and CH_4.
基金supported by the Special Fund of Environmental Protection Research for Public Welfare, Ministry of Environmental Protection of China (No. 201209022)the China Scholarship Council (CSC) for scholarship support
文摘The denitrifying anaerobic methane oxidation is an ecologically important process for reducing the potential methane emission into the atmosphere.The responsible bacterium for this process was Candidatus Methylomirabilis oxyfera belonging to the bacterial phylum of NC10.In this study,a new pair of primers targeting all the five groups of NC10 bacteria was designed to amplify NC10 bacteria from different environmental niches.The results showed that the group A was the dominant NC10 phylum bacteria from the sludges and food waste digestate while in paddy soil samples,group A and group B had nearly the same proportion.Our results also indicated that NC10 bacteria could exist in a high p H environment（pH 9.24）from the food waste treatment facility.The Pearson relationship analysis showed that the p H had a significant positive relationship with the NC10 bacterial diversity（p0.05）.The redundancy analysis further revealed that the p H,volatile solid and nitrite nitrogen were the most important factors in shaping the NC10 bacterial structure（p=0.01）based on the variation inflation factors selection and Monte Carlo test（999 times）.Results of this study extended the existing molecular tools for studying the NC10 bacterial community structures and provided new information on the ecological distributions of NC10 bacteria.
基金Sponsored by the National Natural Science Foundation for Youth of China(Grant No.51308149)Major Science and Technology Program for Water Pollution Control Treatment(Grant No.2014ZX07201-012+1 种基金2013ZX07201007-001)State Key Laboratory of Urban Water Resource and Environment(Harbin Institute of Technology)(Grant No.2014TS08)
文摘Anaerobic digestion is widely used in the treatment of industrial wastewater,excess activated sludge,municipal waste,crop straw and livestock manure,with the functions of environmental protection and energy recovery. This review summarizes and evaluates the present knowledge of effects of different states of Fe( ZVI,Fe( II),Fe( III)) on hydrogen and methane production in anaerobic digestion process. The potential promotion effects of iron oxides nanoparticles( IONPs),especially magnetite nanoparticles on anaerobic digestion are also mentioned. Fe plays important role in transporting electron,stimulating bacterial growth and increasing hydrogen and methane production rate by promoting enzyme activity. Adding Fe with different morphologies and valence states in anaerobic digestion to increase biogas( hydrogen and methane) production and enhance organic matter degradation simultaneously,which has attracted many scientists' attention in recent years. Rapid progress in this area has been made over the last few years,since Fe is essential to the fermentative hydrogen and methane production,while few is known about how Fe affects the fermentative biogas production. This review is significant to maintain the stable operation of the biogas project.
基金The Program of Institution of South China Sea Ecology and Environmental Engineering,Chinese Academy of Sciences under contract No.ISEE2018YB03the Special Project for Marine Economy Development of Guangdong Province under contract No.GDME-2018D002+1 种基金the Evaluation and Detection Technology Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology under contract No.KC201703the Youth Innovation Promotion Association CAS under contract No.201432
文摘Recent studies have shown that specific geochemical characteristics of sediments can be used to reconstruct past methane seepage events.In this work,the correlation between the Sr/Ca and Mg/Ca ratios of sediment samples is analyzed and the sulfate concentration profile in Site C14 from cold-seep sediments in the Qiongdongnan Basin in northern South China Sea is obtained.The results confirmed that,sulfate at 0–247 cm below sea floor(Unit I)is mainly consumed by organic matter sulfate reduction(OSR),while sulfate at 247–655 cm(UnitⅡ)is consumed by both the OSR and the anaerobic oxidation of methane(AOM).In addition,the bottom sediment layer is affected by weak methane seepage.The Mo and U enrichment factors also exhibit similar trends in their respective depth profiles.The responses of trace elements,including Co/Al,Ni/Al,Cr/Al and Zn/Al ratios to methane seepage allowed the study of depositional conditions and methane seepage events.Based on the results,it is speculated that the depositional conditions of UnitⅡchanged with depth from moderate conditions of sulfidic and oxic conditions to locally anoxic conditions,and finally to suboxic conditions due to methane fluid leakage.The stable isotope values of chromium-reducible sulfide produced by AOM and those of sulfide formed by OSR in the early diagenetic environment suffered serious depletion of 34S.This was probably due to weak methane leakage,which caused the slower upward diffusion and the effect of early diagenesis on the samples.It is necessary to consider the effects of depositional environments and diagenesis on these geochemical parameters.
文摘The concentrations of CH4 and SO42? in pore-water and the carbon isotope compositions of total dissolved inorganic (ΣCO2) and CH4 were de- termined for three coastal sedimentary cores col- lected from Qi’ao Island (Pearl River Estuary), southern China. Results show that methane concen- tration changes dramatically at the base of the sul- fate-reducing zone and sulfate concentration gradi- ents are linear for all stations. In addition, the carbon isotope of methane becomes heavier at the sul- fate-methane transition (SMT), which causes ΣCO2-δ 13C to become the minimum. The geo- chemical profiles of pore-water render indirect evi- dence for anaerobic oxidation of methane (AOM). Based on numerical modeling of AOM and sul- fate-reducing rates, the portion of total sulfate reduc- tion occurring via AOM is 9.0%, 84% and 45.5%, re- spectively, and the percentage of ΣCO2 added to the pore-water is 4.7%, 72.4% and 29.45% correspond- ingly for three sites. Furthermore, it is found that the methane concentration, methane diffusive flux and the depth of SMT are controlled by the quantity and quality of sedimentary organic matter incorporated into the sediments. The great amount of organic material is favorable for rapid depletion of sulfate via sedimentary organic matter degradation, and on the other hand, causes the increase of the methane flux in the SMT, which results in a portion of sulfate re-duction supported by AOM. Accordingly, the SMT was shifted towards the sediment surface.
基金The National Natural Science Foundation of China under contract Nos 41606087,91858208,and 42076069the Taishan Scholar Special Experts Project under contract No.TS201712079+1 种基金the National Key Basic Research and Development Program of China under contract No.2017YFC0307704the Marine Geological Survey Program of China Geological Survey under contract Nos DD20190518 and DD20190819。
文摘Cold seeps are pervasive along the continental margin worldwide,and are recognized as hotspots for elemental cycling pathway on Earth.In this study,analyses of pore water geochemical compositions of one-400 cm piston core(S3)and the application of a mass balance model are conducted to assess methane-associated biogeochemical reactions and uncover the relationship of methane in shallow sediment with gas hydrate reservoir at the Makran accretionary wedge off Pakistan.The results revealed that approximately 77%of sulfate is consumed by the predominant biogeochemical process of anaerobic oxidation of methane.However,the estimated sulfate-methane interface depth is-400 cm below sea floor with the methane diffusive flux of 0.039 mol/(m^(2)·a),suggesting the activity of methane seepage.Based on the δ^(13)C_(DIC) mass balance model combined with the contribution proportion of different dissolved inorganic carbon sources,this study calculated the δ^(13)C of the exogenous methane to be-57.9‰,indicating that the exogenous methane may be a mixture source,including thermogenic and biogenic methane.The study of pore water geochemistry at Makran accretionary wedge off Pakistan may have considerable implications for understanding the specific details on the dynamics of methane in cold seeps and provide important evidence for the potential occurrence of subsurface gas hydrate in this area.
基金the Key Geological Issues in China Sea,the China Geological Survey(Nos.DD20160147 and GZH201100202)the Taishan Scholar Project Grant to Guangxue Li.
文摘The biological removal of CH4 by methanotrophic(CH4-oxidizing)archaea always occurs at a distinct zone which is known as sulfate-methane transition zone(SMTZ).It is an important indication for high methane flux and gas hydrate occurrence.In this study,we collected pore-water data from South China Sea,Carolina Rise and Blake Ridge to analyze the relationship between CH4,SO42−concentration and depth.We found that below the SMTZ,the methane concentration increases continuously with depth and sulfate concentration decrease linearly to zero.In addition,the geochemical data taken from all these sites show that SMTZ is relatively shallow(less than 20 m),which may indicate that these areas have high methane flux.
基金supported by the Foundation of National Special Item on Water Resource and Environment (No.2014ZX07303003 and 2017ZX07603003)
文摘Low organic matter content and high heavy metal levels severely inhibit the anaerobic digestion(AD) of sewage sludge. In this study, the effect of added manganese oxidemodified biochar composite(MBC) on methane production and heavy metal fractionation during sewage sludge AD was examined. The MBC could increase the buffering capacity,enhance the methane production and degradation of intermediate acids, buffer the pH of the culture, and stabilize the sewage sludge AD process. The application of MBC positively impacted methane production and the cumulative methane yield increased up to 121.97%,as compared with the control. The MBC addition can improve metal stabilization in the digestate. An optimum MBC dose of 2.36 g was recommended, which would produce up to 121.1 L/kg volatile solids of methane. After the AD process, even though most of the metals accumulated in the residual solids, they could be transformation from the bio-available fractions to a more stable fraction. The total organic-and sulfide-bound and residual fraction content at a 3 g dose of MBC that is 0.12 g/g dry matter were 51.06% and 35.11% higher than the control, respectively. The results indicated that the application of MBC could improve the performance of AD and promote stabilization of heavy metals in sewage sludge post the AD process.
