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
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
The argument over fiscal decentralization and carbon dioxide emission(CO_(2))reduction has received much attention.However,evidence to back this claim is limited.Economic theory predicts that fiscal decentralization a...The argument over fiscal decentralization and carbon dioxide emission(CO_(2))reduction has received much attention.However,evidence to back this claim is limited.Economic theory predicts that fiscal decentralization affects environmental quality,but the specifics of this relationship are still up for debate.Some scholars noted that fiscal decentralization might lead to a race to the top,whereas others contended that it would result in a race to the bottom.In light of the current debates in environmental and development economics,this study aims to provide insight into how this relationship may function in South Africa from 1960 to 2020.In contrast to the existing research,the present study uses a novel dynamic autoregressive distributed lag simulation approach to assess the positive and negative changes in fiscal decentralization,scale effect,technique effect,technological innovation,foreign direct investment,energy consumption,industrial growth,and trade openness on CO_(2)emissions.The following are the main findings:(i)Fiscal decentralization had a CO_(2)emission reduction impact in the short and long run,highlighting the presence of the race to the top approach.(ii)Economic growth(as represented by the scale effect)eroded ecological integrity.However,its square(as expressed by technique effect)aided in strengthening ecological protection,validating the environmental Kuznets curve hypothesis.(iii)CO_(2)emissions were driven by energy utilization,trade openness,industrial value-added,and foreign direct investment,whereas technological innovation boosted ecological integrity.Findings suggest that further fiscal decentralization should be undertaken through further devolution of power to local entities,particularly regarding environmental policy issues,to maintain South Africa’s ecological sustainability.South Africa should also establish policies to improve environmental sustainability by strengthening a lower layer of government and clarifying responsibilities at the national and local levels to fulfill the energy-saving functions of fiscal expenditures.展开更多
CO_(2)capture and storage(CCS)has the risk of CO_(2)leakage,and this leakage always increases soil CO_(2)concentration,and the long-term CO_(2)stress damages crop production in farmland.Using maize,the growth characte...CO_(2)capture and storage(CCS)has the risk of CO_(2)leakage,and this leakage always increases soil CO_(2)concentration,and the long-term CO_(2)stress damages crop production in farmland.Using maize,the growth characteristics,such as plant height and yield,and physiological indexes(osmoregulation substances and antioxidant enzymes)were explored under different simulative CO_(2)leakage conditions.Further,the relationship between maize physiological indexes and soil CO_(2)concentration was analyzed,showing that soil CO_(2)stress inhibited maize growth to a certain extent,resulting in shorter plants,thinner stems and lower kernel yield.With an increase in soil CO_(2)concentration,the contents of malondialdehyde,soluble sugar and soluble protein in maize leaves increased;with continuing stress,the increase rate of malondialdehyde was greatly augmented,whereas the increase rates of soluble sugar and soluble protein decreased.With extended CO_(2)stress,the activity of the enzyme superoxide dismutase(SOD)increased continuously,while the activities of catalase and peroxidase first increased and then decreased.Superoxide dismutase activity was closely correlated with soil CO_(2)concentration(r=0.762),and responded quickly to the change of soil CO_(2)concentration(R~2=0.9951).Therefore,SOD plays an important role in maize resistance to soil CO_(2)stress.This study will help further understanding of the mechanism of maize tolerance to soil CO_(2)stress,providing a theoretical basis for agricultural production in CCS project areas.展开更多
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。
文摘The argument over fiscal decentralization and carbon dioxide emission(CO_(2))reduction has received much attention.However,evidence to back this claim is limited.Economic theory predicts that fiscal decentralization affects environmental quality,but the specifics of this relationship are still up for debate.Some scholars noted that fiscal decentralization might lead to a race to the top,whereas others contended that it would result in a race to the bottom.In light of the current debates in environmental and development economics,this study aims to provide insight into how this relationship may function in South Africa from 1960 to 2020.In contrast to the existing research,the present study uses a novel dynamic autoregressive distributed lag simulation approach to assess the positive and negative changes in fiscal decentralization,scale effect,technique effect,technological innovation,foreign direct investment,energy consumption,industrial growth,and trade openness on CO_(2)emissions.The following are the main findings:(i)Fiscal decentralization had a CO_(2)emission reduction impact in the short and long run,highlighting the presence of the race to the top approach.(ii)Economic growth(as represented by the scale effect)eroded ecological integrity.However,its square(as expressed by technique effect)aided in strengthening ecological protection,validating the environmental Kuznets curve hypothesis.(iii)CO_(2)emissions were driven by energy utilization,trade openness,industrial value-added,and foreign direct investment,whereas technological innovation boosted ecological integrity.Findings suggest that further fiscal decentralization should be undertaken through further devolution of power to local entities,particularly regarding environmental policy issues,to maintain South Africa’s ecological sustainability.South Africa should also establish policies to improve environmental sustainability by strengthening a lower layer of government and clarifying responsibilities at the national and local levels to fulfill the energy-saving functions of fiscal expenditures.
基金supported by the 863 Program Grant of the Ministry of Science and Technology of China(Grant No.2012AA050103)the High-level Talents Scientific Research Start-up Fund Project of Yulin University(Grant No.2023GK13)+5 种基金the Key Industry Innovation Chain Group Project of Shaanxi Province(Grant No.2023-ZDLSF-64)the“New Star of Science and Technology”Talent Program of Yulin(Grant No.CXY-2022-137)the Natural Science Research Project of the Education Department in Shaanxi Province of China(Grant No.22JK0636)the Natural Science Basic Research Program of Shaanxi Province(Grant No.2021JCW-04)Young Talent Fund of Association for Science and Technology in Yulinthe Natural Science Sesearch Program of the Yulin High-tech Zone Science and Technology Bureau。
文摘CO_(2)capture and storage(CCS)has the risk of CO_(2)leakage,and this leakage always increases soil CO_(2)concentration,and the long-term CO_(2)stress damages crop production in farmland.Using maize,the growth characteristics,such as plant height and yield,and physiological indexes(osmoregulation substances and antioxidant enzymes)were explored under different simulative CO_(2)leakage conditions.Further,the relationship between maize physiological indexes and soil CO_(2)concentration was analyzed,showing that soil CO_(2)stress inhibited maize growth to a certain extent,resulting in shorter plants,thinner stems and lower kernel yield.With an increase in soil CO_(2)concentration,the contents of malondialdehyde,soluble sugar and soluble protein in maize leaves increased;with continuing stress,the increase rate of malondialdehyde was greatly augmented,whereas the increase rates of soluble sugar and soluble protein decreased.With extended CO_(2)stress,the activity of the enzyme superoxide dismutase(SOD)increased continuously,while the activities of catalase and peroxidase first increased and then decreased.Superoxide dismutase activity was closely correlated with soil CO_(2)concentration(r=0.762),and responded quickly to the change of soil CO_(2)concentration(R~2=0.9951).Therefore,SOD plays an important role in maize resistance to soil CO_(2)stress.This study will help further understanding of the mechanism of maize tolerance to soil CO_(2)stress,providing a theoretical basis for agricultural production in CCS project areas.
