The magnitude and spatial variability of CO_(2)surface emissions and processes involving CO_(2)released to the atmosphere from the soils are relevant issues in the context of climate change.This work evaluated CO_(2)f...The magnitude and spatial variability of CO_(2)surface emissions and processes involving CO_(2)released to the atmosphere from the soils are relevant issues in the context of climate change.This work evaluated CO_(2)fluxes and^(13)C/^(12)C ratio of vegetation,organic matter,and soil gases from no disturbed soils of Chaco Pampean Plain(Argentina)with different soil properties and environmental conditions(PL and PA units).Soil organic decomposition from individual layers was accompanied byδ^(13)C of total organic carbon(δ^(13)C-TOC)values more enriched to depth.δ^(13)C-TOC values in the upper soil profile~ca.0–15 cm were like the plant community of this area(~−33 to−29‰)whileδ^(13)CTOC varied stronger bellow horizon A,till~−24‰.Bothδ^(13)C-TOC and soilδ^(13)C-CO_(2)were similar(~−24 to 26‰)at deeper horizons(~50–60 cm).Toward the superficial layers,δ^(13)C-TOC andδ^(13)C-CO_(2)showed more differences(till~4‰),due influence of the diffusion process.Horizon A layer(~0–20 cm)from both PL and PA units contained the most enrichedδ^(13)C-CO_(2)values(~−15–17‰)because atmospheric CO_(2)permeated the soil air.A simple two-component mixing model between sources(atmosphericδ^(13)C-CO_(2)and soil CO_(2))confirmed that process.Isotopically,CO_(2)fluxes reflected the biodegradation of C3 plants(source),diffusive transport,and CO_(2)exchange(atmosphere/soil).Soil moisture content appeared as a determining factor in the diffusion process and the magnitude of CO_(2)surface emissions(12–60 g·m^(−2)·d^(−1)).That condition was confirmed by CO_(2)diffusion coefficients estimated by air-filled porosity parameters and soil radon gradient model.展开更多
In recent years,there has been growing interest in developing methods for mitigating greenhouse effect,as greenhouse gas emissions continue to contribute to global temperature rise.On the other hand,investigating geop...In recent years,there has been growing interest in developing methods for mitigating greenhouse effect,as greenhouse gas emissions continue to contribute to global temperature rise.On the other hand,investigating geopolymers as environmentally friendly binders to mitigate the greenhouse effect using soil stabilization has been widely conducted.However,the effect of CO_(2)exposure on the mechanical properties of geopolymer-stabilized soils is rarely reported.In this context,the effect of CO_(2)exposure on the mechanical and microstructural features of sandy soil stabilized with volcanic ash-based geopolymer was investigated.Several factors were concerned,for example the binder content,relative density,CO_(2)pressure,curing condition,curing time,and carbonate content.The results showed that the compressive strength of the stabilized sandy soil specimens with 20%volcanic ash increased from 3 MPa to 11 MPa.It was also observed that 100 kPa CO_(2)pressure was the optimal pressure for strength development among the other pressures.The mechanical strength showed a direct relationship with binder content and carbonate content.Additionally,in the ambient curing(AC)condition,the mechanical strength and carbonate content increased with the curing time.However,the required water for carbonation evaporated after 7 d of oven curing(OC)condition and as a result,the 14-d cured samples showed lower mechanical strength and carbonate content in comparison with 7-d cured samples.Moreover,the rate of strength development was higher in OC cured samples than AC cured samples until 7 d due to higher geopolymerization and carbonation rate.展开更多
Background,aim,and scope The tectonic uplift of the Cenozoic Tibetan Plateau has produced a chain effect,which is an excellent location for Earth system science research,and its uplift process,mechanism and environmen...Background,aim,and scope The tectonic uplift of the Cenozoic Tibetan Plateau has produced a chain effect,which is an excellent location for Earth system science research,and its uplift process,mechanism and environmental effects are the hot spot and frontier of the current research.The“Tibetan Plateau uplift-weathering-CO_(2) concentration-global climate change”model was put forward by Raymo and Ruddiman to interpret the Late Cenozoic climate change.However,there are still some questions suspended,such as does the weathering of the Tibetan Plateau have the ability to control the global climate?How to explain the modern-like global CO_(2) concentration starting at about 24 Ma?Here,a short space was taken to present a brainstorm about the above questions on account of existing geological pieces of evidence.Materials and methods In this paper,we integrate the formation and evolution of the Yangtze River and Pearl River,the origin and development of the Asian inland aridification-monsoon system,the Cenozoic tectonic uplift process of the Tibetan Plateau,and the westerly winds to discuss and analyze the relationship between the Cenozoic CO_(2) concentration changes and the uplift of the Tibetan Plateau and why the CO_(2) concentration similar to the present was formed at about 24 Ma.Results Similar correspondence of the surface uplift history of Xizang,other global mountains,and the declining CO_(2) concentration could support the theory Tibetan Plateau weathering inf luences CO_(2) concentration.Starting from 24 Ma,the most important character was the uplift and erosion of Xizang and Himalaya,collaborating with Ocean Iron Fertilization(OIF)together as an entity to control the atmospheric CO_(2) concentration because the great Asian rivers,Asian monsoons,and westerlies connected Xizang and surrounded seas together through materials transportation.Discussion Paleogeographic reconstructions from 40 Ma to 20 Ma illustrate that the main topographic change occurred in the Andes,Cordillera orogenic belt,and Xizang.We comprise a comprehensive set of evidence from independent data,which correspond temporally with the tipping point(about 24 Ma)of the atmospheric CO_(2) and we noticed that modern-like Asia monsoon,inland aridity,Asian great rivers,and climate zone formed at about 24 Ma and also there are tectonic activities for the Andes and Rockies.We raised the possibility that the modern-like atmospheric CO_(2) concentration at about 24 Ma was caused by the above geological factors.Here the rivers,monsoon,and westerlies are termed as“connectors”.In addition,these Asian rivers originated from Xizang,the monsoon,and inner Asian aridification are strongly a function of the uplift and growth of Xizang,thus,Xizang here is named as“trigger”.The distinct character of“trigger-connectors”model is that this not only takes the monsoon,westerlies,and the global great rivers into consideration but also expands the range which inf luences atmospheric CO_(2) concentration,from local points to a vast area since about 24 Ma,such as from Tibetan Plateau to Asia,including surrounded seas,after about 24 Ma.However,because the opening of the Late Oligocene-Early Miocene Antarctic periphery straits is highly coincident with the onset of modern-like global atmospheric CO_(2) concentration,we are forced to consider that they also had a significant impact on the reduction of atmospheric CO_(2) concentrations at this time.Conclusions“Trigger-connectors”was put forward to explain the Cenozoic CO_(2) variation,especially modern-like global CO_(2) concentration since about 24 Ma.Recommendations and perspectives Here we use the“trigger-connectors”model to explain the formation of modern-like CO_(2) concentrations starting at about 24 Ma,but there are still some problems.The most important premise for the“trigger-connectors”model is the constructed Cenozoic CO_(2) concentration record is reliable,which is the foundation of our hypothesis.In the future,potential improvements should focus on topographic reconstructions of Xizang and the global mountains.Here we have concentrated on Xizang in the considered timeslices but still,pay less attention to other global orogenic belts.Collaborations with geologist experts in those regions could provide valuable feedback to evaluate their potential role of them in CO_(2) evolution.What is more,considerable progress may be achieved with the addition and consideration of more and new geological data.展开更多
全球变暖已经成为不争的事实,陆地生态系统碳循环的研究受到了各界广泛关注,是当前全球变化研究中的重点。土壤CO_(2)排放是陆地生态系统与大气间二氧化碳交换的最大通量之一,当前陆地生态系统中土壤CO_(2)排放如何响应全球气候变暖及...全球变暖已经成为不争的事实,陆地生态系统碳循环的研究受到了各界广泛关注,是当前全球变化研究中的重点。土壤CO_(2)排放是陆地生态系统与大气间二氧化碳交换的最大通量之一,当前陆地生态系统中土壤CO_(2)排放如何响应全球气候变暖及其影响因素仍不清楚,限制了对土壤碳循环过程及影响机制的深入认识。旨在明确全球变暖背景下陆地生态系统中土壤CO_(2)排放格局及影响因素。基于Web of Science、PubMed和中国知网等中英文期刊数据库,充分收集全球范围内的相关野外试验文献81篇,提取出65个研究位置和213组相关研究数据,采用Meta分析方法探讨陆地生态系统土壤CO_(2)排放对增温的响应特征,分析其与海拔、气候、土壤含水量、容重(BD)、pH、全氮(TN)和土壤有机碳(SOC)的相关关系。结果表明:陆地生态系统中土壤CO_(2)排放对增温整体有显著的正向响应,在农、林、草生态系统中,增温使土壤CO_(2)排放分别显著增加13.1%、18.0%、5.9%(P<0.05),森林生态系统对增温响应的正效应最强烈;增温能在短时期内促进土壤呼吸,但随着增温持续时间增加,土壤呼吸对温度的敏感性会降低,对温度变化产生适应性,从而使其对增温的响应能力减弱;响应特征受到环境因子、土壤特性以及其他试验条件等的影响,绝大多数条件下对增温表现出显著的正响应特征,不同影响因子之间共同作用、相互影响。增温通常能够改变植物生物量、土壤养分含量及微生物数量和活性,从而影响到植被根际呼吸和土壤呼吸速率。相关分析表明,海拔对土壤CO_(2)排放有显著负向影响,而年均气温、年均降水量、土壤含水量和仪器嵌入土壤深度则对土壤CO_(2)排放产生显著正向影响。这些结果对于理解全球土壤CO_(2)排放的时空变化格局有重要意义,也为准确评价全球变暖背景下土壤碳汇功能及其持续性提供理论依据。展开更多
基金Financial support was provided through the Instituto de Geociencias Básicas,Aplicadas y Ambientales de Buenos Aires(IGEBA)and the Instituto de Geocronología y Geología Isotópica(INGEIS),both dependent of the Consejo Nacional de Investigaciones Científi cas y Técnicas(National Council for Scientific and Technological Research),and the Universidad de Buenos Aires(Buenos Aires University)of Argentinasupported by the Agencia Nacional de Promoción Científi ca y Tecnológica(National Agency for Scientific and Technological Promotion)projects PICT2010-0035 and PICT2010-2749。
文摘The magnitude and spatial variability of CO_(2)surface emissions and processes involving CO_(2)released to the atmosphere from the soils are relevant issues in the context of climate change.This work evaluated CO_(2)fluxes and^(13)C/^(12)C ratio of vegetation,organic matter,and soil gases from no disturbed soils of Chaco Pampean Plain(Argentina)with different soil properties and environmental conditions(PL and PA units).Soil organic decomposition from individual layers was accompanied byδ^(13)C of total organic carbon(δ^(13)C-TOC)values more enriched to depth.δ^(13)C-TOC values in the upper soil profile~ca.0–15 cm were like the plant community of this area(~−33 to−29‰)whileδ^(13)CTOC varied stronger bellow horizon A,till~−24‰.Bothδ^(13)C-TOC and soilδ^(13)C-CO_(2)were similar(~−24 to 26‰)at deeper horizons(~50–60 cm).Toward the superficial layers,δ^(13)C-TOC andδ^(13)C-CO_(2)showed more differences(till~4‰),due influence of the diffusion process.Horizon A layer(~0–20 cm)from both PL and PA units contained the most enrichedδ^(13)C-CO_(2)values(~−15–17‰)because atmospheric CO_(2)permeated the soil air.A simple two-component mixing model between sources(atmosphericδ^(13)C-CO_(2)and soil CO_(2))confirmed that process.Isotopically,CO_(2)fluxes reflected the biodegradation of C3 plants(source),diffusive transport,and CO_(2)exchange(atmosphere/soil).Soil moisture content appeared as a determining factor in the diffusion process and the magnitude of CO_(2)surface emissions(12–60 g·m^(−2)·d^(−1)).That condition was confirmed by CO_(2)diffusion coefficients estimated by air-filled porosity parameters and soil radon gradient model.
基金This study was supported by MatSoil Company(Grant No.04G/2022)This research was funded by the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie(Grant No.778120).
文摘In recent years,there has been growing interest in developing methods for mitigating greenhouse effect,as greenhouse gas emissions continue to contribute to global temperature rise.On the other hand,investigating geopolymers as environmentally friendly binders to mitigate the greenhouse effect using soil stabilization has been widely conducted.However,the effect of CO_(2)exposure on the mechanical properties of geopolymer-stabilized soils is rarely reported.In this context,the effect of CO_(2)exposure on the mechanical and microstructural features of sandy soil stabilized with volcanic ash-based geopolymer was investigated.Several factors were concerned,for example the binder content,relative density,CO_(2)pressure,curing condition,curing time,and carbonate content.The results showed that the compressive strength of the stabilized sandy soil specimens with 20%volcanic ash increased from 3 MPa to 11 MPa.It was also observed that 100 kPa CO_(2)pressure was the optimal pressure for strength development among the other pressures.The mechanical strength showed a direct relationship with binder content and carbonate content.Additionally,in the ambient curing(AC)condition,the mechanical strength and carbonate content increased with the curing time.However,the required water for carbonation evaporated after 7 d of oven curing(OC)condition and as a result,the 14-d cured samples showed lower mechanical strength and carbonate content in comparison with 7-d cured samples.Moreover,the rate of strength development was higher in OC cured samples than AC cured samples until 7 d due to higher geopolymerization and carbonation rate.
文摘Background,aim,and scope The tectonic uplift of the Cenozoic Tibetan Plateau has produced a chain effect,which is an excellent location for Earth system science research,and its uplift process,mechanism and environmental effects are the hot spot and frontier of the current research.The“Tibetan Plateau uplift-weathering-CO_(2) concentration-global climate change”model was put forward by Raymo and Ruddiman to interpret the Late Cenozoic climate change.However,there are still some questions suspended,such as does the weathering of the Tibetan Plateau have the ability to control the global climate?How to explain the modern-like global CO_(2) concentration starting at about 24 Ma?Here,a short space was taken to present a brainstorm about the above questions on account of existing geological pieces of evidence.Materials and methods In this paper,we integrate the formation and evolution of the Yangtze River and Pearl River,the origin and development of the Asian inland aridification-monsoon system,the Cenozoic tectonic uplift process of the Tibetan Plateau,and the westerly winds to discuss and analyze the relationship between the Cenozoic CO_(2) concentration changes and the uplift of the Tibetan Plateau and why the CO_(2) concentration similar to the present was formed at about 24 Ma.Results Similar correspondence of the surface uplift history of Xizang,other global mountains,and the declining CO_(2) concentration could support the theory Tibetan Plateau weathering inf luences CO_(2) concentration.Starting from 24 Ma,the most important character was the uplift and erosion of Xizang and Himalaya,collaborating with Ocean Iron Fertilization(OIF)together as an entity to control the atmospheric CO_(2) concentration because the great Asian rivers,Asian monsoons,and westerlies connected Xizang and surrounded seas together through materials transportation.Discussion Paleogeographic reconstructions from 40 Ma to 20 Ma illustrate that the main topographic change occurred in the Andes,Cordillera orogenic belt,and Xizang.We comprise a comprehensive set of evidence from independent data,which correspond temporally with the tipping point(about 24 Ma)of the atmospheric CO_(2) and we noticed that modern-like Asia monsoon,inland aridity,Asian great rivers,and climate zone formed at about 24 Ma and also there are tectonic activities for the Andes and Rockies.We raised the possibility that the modern-like atmospheric CO_(2) concentration at about 24 Ma was caused by the above geological factors.Here the rivers,monsoon,and westerlies are termed as“connectors”.In addition,these Asian rivers originated from Xizang,the monsoon,and inner Asian aridification are strongly a function of the uplift and growth of Xizang,thus,Xizang here is named as“trigger”.The distinct character of“trigger-connectors”model is that this not only takes the monsoon,westerlies,and the global great rivers into consideration but also expands the range which inf luences atmospheric CO_(2) concentration,from local points to a vast area since about 24 Ma,such as from Tibetan Plateau to Asia,including surrounded seas,after about 24 Ma.However,because the opening of the Late Oligocene-Early Miocene Antarctic periphery straits is highly coincident with the onset of modern-like global atmospheric CO_(2) concentration,we are forced to consider that they also had a significant impact on the reduction of atmospheric CO_(2) concentrations at this time.Conclusions“Trigger-connectors”was put forward to explain the Cenozoic CO_(2) variation,especially modern-like global CO_(2) concentration since about 24 Ma.Recommendations and perspectives Here we use the“trigger-connectors”model to explain the formation of modern-like CO_(2) concentrations starting at about 24 Ma,but there are still some problems.The most important premise for the“trigger-connectors”model is the constructed Cenozoic CO_(2) concentration record is reliable,which is the foundation of our hypothesis.In the future,potential improvements should focus on topographic reconstructions of Xizang and the global mountains.Here we have concentrated on Xizang in the considered timeslices but still,pay less attention to other global orogenic belts.Collaborations with geologist experts in those regions could provide valuable feedback to evaluate their potential role of them in CO_(2) evolution.What is more,considerable progress may be achieved with the addition and consideration of more and new geological data.
文摘全球变暖已经成为不争的事实,陆地生态系统碳循环的研究受到了各界广泛关注,是当前全球变化研究中的重点。土壤CO_(2)排放是陆地生态系统与大气间二氧化碳交换的最大通量之一,当前陆地生态系统中土壤CO_(2)排放如何响应全球气候变暖及其影响因素仍不清楚,限制了对土壤碳循环过程及影响机制的深入认识。旨在明确全球变暖背景下陆地生态系统中土壤CO_(2)排放格局及影响因素。基于Web of Science、PubMed和中国知网等中英文期刊数据库,充分收集全球范围内的相关野外试验文献81篇,提取出65个研究位置和213组相关研究数据,采用Meta分析方法探讨陆地生态系统土壤CO_(2)排放对增温的响应特征,分析其与海拔、气候、土壤含水量、容重(BD)、pH、全氮(TN)和土壤有机碳(SOC)的相关关系。结果表明:陆地生态系统中土壤CO_(2)排放对增温整体有显著的正向响应,在农、林、草生态系统中,增温使土壤CO_(2)排放分别显著增加13.1%、18.0%、5.9%(P<0.05),森林生态系统对增温响应的正效应最强烈;增温能在短时期内促进土壤呼吸,但随着增温持续时间增加,土壤呼吸对温度的敏感性会降低,对温度变化产生适应性,从而使其对增温的响应能力减弱;响应特征受到环境因子、土壤特性以及其他试验条件等的影响,绝大多数条件下对增温表现出显著的正响应特征,不同影响因子之间共同作用、相互影响。增温通常能够改变植物生物量、土壤养分含量及微生物数量和活性,从而影响到植被根际呼吸和土壤呼吸速率。相关分析表明,海拔对土壤CO_(2)排放有显著负向影响,而年均气温、年均降水量、土壤含水量和仪器嵌入土壤深度则对土壤CO_(2)排放产生显著正向影响。这些结果对于理解全球土壤CO_(2)排放的时空变化格局有重要意义,也为准确评价全球变暖背景下土壤碳汇功能及其持续性提供理论依据。
