This study evaluates the efficacy of sustainable erosion control using slag-based alkali-activated cement crusts under varying rainfall and wind conditions. The rainfall intensities ranged from 30 mm/h to 120 mm/h, wi...This study evaluates the efficacy of sustainable erosion control using slag-based alkali-activated cement crusts under varying rainfall and wind conditions. The rainfall intensities ranged from 30 mm/h to 120 mm/h, with durations ranging from 15 min to 90 min, and crust slopes of ∼2° (gentle) and 30° (steep). Wind tunnel experiments were conducted at wind velocities of 14 m/s, 21 m/s, and 28 m/s to investigate post-rainfall wind erodibility, along with changes in crust strength and microstructure analysis. The findings show the development of hydrated cementitious phases in alkali-activated material, which form around and between the particles during the alkaline activation process. Alkali-activated cement crusts significantly reduced erosion caused by rainfall and subsequent wind by several orders of magnitude. At the highest rainfall intensity of 120 mm/h, rainfall erosion was measured to be 1654.81 kg/m2 for untreated samples and 0.89 kg/m2 for treated samples, demonstrating a substantial 99.95% reduction in erosion due to the treatment. Similarly, at the highest wind speed tested, wind erosion was 122.75 kg/m2 for untreated samples and 0.095 kg/m2 for treated samples, indicating a significant 99.92% reduction in erosion due to the formation of an alkali-activated cement crust on the soil surface. However, exposure of the samples to 120 mm/h rainfall for 90 min resulted in a 5.2-fold increase in wind erosion compared to pre-rainfall conditions. Similarly, penetrometer results indicated a 37%–54% reduction in post-rainfall surface strength.展开更多
The evolution of continental crust can be directly linked to the first-order supercontinent-superplume cycles.We demonstrate that:(1)a mantle-like oxygen isotopic signature is not a diagnostic feature for distinguishi...The evolution of continental crust can be directly linked to the first-order supercontinent-superplume cycles.We demonstrate that:(1)a mantle-like oxygen isotopic signature is not a diagnostic feature for distinguishing crustal addition from the reworking of pre-existing continental crust;(2)juvenile continental crust shows a wide range of whole-rock Hf isotopic compositions throughout Earth's history;and(3)detrital zircon Hf model ages cannot reliably determine the growth of continental crust.Thus,the wide use of zircon Hf model ages,based on zircon grains with mantle-like oxygen isotopes,is inappropriate for estimating the timing of continental crustal generation.Based on an analysis of global Hf and O isotope and zircon age databases,we argue that the actual U-Pb crystallization ages of juvenile zircon grains provide the best opportunity to unravel crustal growth through time and to test its relationship with supercontinent-superplume cycles.Furthermore,when the Hf isotopes of these juvenile grains plot within the field of juvenile continental crust,they correlate well with times of global mantle depletion as recorded by Os and He isotopes,plume activity as recorded by LIP events,and periods of crustal growth and the breakup of supercontinents.In contrast,zircon grains crystallized from magmas that were produced by partial melting of pre-existing continental crust show U-Pb age peaks that correspond mainly to times of supercontinent assembly and crustal reworking.Detailed analysis shows the key role played by recycling of mafic crustal components in the generation of juvenile continental crust.展开更多
We must persevere to drill through the intact ocean crust to fully address fundamental questions towards completion of the plate tectonics theory.The primary questions include:what is the ocean crust made up of,how th...We must persevere to drill through the intact ocean crust to fully address fundamental questions towards completion of the plate tectonics theory.The primary questions include:what is the ocean crust made up of,how thick is it and what is the petrological nature of the crust-mantle boundary(i.e.,Mohorovičićdiscontinuity or Moho)?These questions may sound naive because they are widely believed to be well-understood facts,but they are not.Correctly,our current knowledge remains incomplete,and some popular misperceptions come from interpretations based on convenient assumptions.One assumption is that the ocean crust inferred from seismic data is of magmatic origin.Testing this assumption is a principal motivation of Project Mohole(1957-1966),attempting to drill intact ocean crust across the Moho into the mantle.Project Mohole failed because of its high cost,engineering challenges and insufficient tries,but the technologies developed made subsequent ocean drilling successful.However,answers to the original questions remain unsatisfactory.For example,seismic crust interpreted to be of magmatic origin is shown to have globally uniform thickness of 6.0±1.0 km,but crust with such thickness at many slow-spreading ridge segments is dominated by serpentinized mantle peridotites exposed on seafloors.Therefore,the popular view on ocean ridge magmatism must be re-examined,which needs intact ocean crust drilling into the mantle.Drilling at geologically simple sites in the fast-spreading Pacific seafloor is most promising.The US-led D/V JOIDES Resolution that has well served the scientific ocean drilling since 1985 is to retire by the end of 2024,but timely the Chinese geoscience community wishes to continue this international endeavor using the purpose-built D/V Meng Xiang to be in service in 2025.The international community is to gather in November 24-27,2024,Guangzhou,China,to discuss strategies on where and how to successfully drill intact ocean crust across the Moho in coming years.展开更多
Physical soil crust(PSC),a key component of surface soil structure,exists extensively in loess areas.PSC is considered to have a significant effect on soil detachment processes.However,the long-term effects and the co...Physical soil crust(PSC),a key component of surface soil structure,exists extensively in loess areas.PSC is considered to have a significant effect on soil detachment processes.However,the long-term effects and the corresponding mechanisms of PSC on soil detachment by overland flow are still not well understood,especially in natural environments.To investigate temporal variation in soil erosion resistance and the underlying factors during PSC formation,an 8×8-m soil plot was exposed to natural conditions in the Loess Plateau over a 524-day period spanning two rainy seasons and a winter between them.A flume test was conducted to determine soil detachment capacity(Dc)under six designed flow shear stress levels(5.66-22.11 Pa)using crusted(SC)and non-crusted(NSC)soil samples at different PSC development stages.Subsequently,two soil erosion resistance parameters,rill erodibility(K_(r))and critical shear stress(τ_(c)),were calculated.Over time,in the SC and NSC treatments,K_(r)decreased from 0.516 to 0.120 s m^(-1)and 0.521 to 0.223 s m^(-1),respectively,whileτ_(c)increased from 0.49 to 4.42 Pa and 0.26-2.46 Pa,respectively.Variation in soil erosion resistance was rapid in the first one to two months,and then slowed down,with slight fluctuations afterwards.In the SC treatment,K_(r)was 42%lower andτ_(c)was 67%greater than those in the NSC treatment.Soil properties changed greatly for both treatments.SCT increased from 0 to 7.09 mm in the SC treatment.Coh increased from 2.91 to 9.04 kPa and 3.01-4.78 kPa in SC and NSC treatments,respectively.Both soil erosion resistance parameters could be well predicted by SCT and Coh in the SC treatment(R^(2)≥0.82),while their best predictor was Coh in the NSC treatment(R^(2)≥0.90).The results demonstrate that PSC formation enhances soil erosion resistance in the soil detachment process in the loess region under natural conditions.Our study revealed the important role and complexity of PSC in the process of soil erosion,and provided theoretical and data support for accurate understanding and prediction of soil erosion.展开更多
IGCP-Project#592(2012-2015)“Continental construction in Central Asia”,funded by UNESCOIUGS,was launched in April 2012.The Project focuses on tectonic and magmatic aspects of formation of continental crust in the Cen...IGCP-Project#592(2012-2015)“Continental construction in Central Asia”,funded by UNESCOIUGS,was launched in April 2012.The Project focuses on tectonic and magmatic aspects of formation of continental crust in the Central Asian Orogenic Belt and their comparison with actualistic examples from the western Pacific.This report summarizes related scientific results and meetings.In total,in 2012 the Project organized,and/or participated in the organization of,six international conferences and workshops,three of which were accompanied by training schools for young scientists and special training courses.At the present time,more than 250 scientists from 27 countries expressed their interest to collaborate in the frame of our Project,of which more than one third are women and young scientists.Participants come from Australia,Bangladesh,Belgium,Canada,China,Czech Republic,Fiji,Finland,France,Germany,India,Indonesia,Iran,Japan,Kazakhstan,Kyrgyzstan,Mongolia,New Zealand,Poland,Philippines,Republic of Korea,Russia,Tajikistan,Turkey,United Kingdom,USA,and Uzbekistan.In order to carry out research and to secure meeting activities,project participants received funding from national and international sources and mining companies.Below we also present a short overview of meetings scheduled for 2013.展开更多
Whilst caking occurs via several different mechanisms,absorption and migration of moisture is frequently the most dominant mechanism within the food and pharmaceutical industry.Fully understanding the propensity to ca...Whilst caking occurs via several different mechanisms,absorption and migration of moisture is frequently the most dominant mechanism within the food and pharmaceutical industry.Fully understanding the propensity to cake is important for minimising down-stream process issues,however most characterisation techniques assume that moisture induced caking occurs homogenously through the sample resulting in a uniformly caked powder bed.In this study,the effect of moisture induced caking on powder flowability was investigated using powder rheology.Several materials,including skimmed milk powder(SMP)and sulphated methyl ester(SME)were stored for several days under controlled humidity conditions.The flow energies,a measure of the resistance to flow,were measured at 24 h intervals using an FT4 Powder Rheometer.As the energy is measured as a function of the bed height,variations in the powder bed are also captured.The results demonstrated that caking does not always occur uniformly,instead a caked region(or crust)forms at the air-powder interface and then progresses through the powder bed.Furthermore,the strength of this caked region was shown to increase over several days before stabilising.展开更多
文摘This study evaluates the efficacy of sustainable erosion control using slag-based alkali-activated cement crusts under varying rainfall and wind conditions. The rainfall intensities ranged from 30 mm/h to 120 mm/h, with durations ranging from 15 min to 90 min, and crust slopes of ∼2° (gentle) and 30° (steep). Wind tunnel experiments were conducted at wind velocities of 14 m/s, 21 m/s, and 28 m/s to investigate post-rainfall wind erodibility, along with changes in crust strength and microstructure analysis. The findings show the development of hydrated cementitious phases in alkali-activated material, which form around and between the particles during the alkaline activation process. Alkali-activated cement crusts significantly reduced erosion caused by rainfall and subsequent wind by several orders of magnitude. At the highest rainfall intensity of 120 mm/h, rainfall erosion was measured to be 1654.81 kg/m2 for untreated samples and 0.89 kg/m2 for treated samples, demonstrating a substantial 99.95% reduction in erosion due to the treatment. Similarly, at the highest wind speed tested, wind erosion was 122.75 kg/m2 for untreated samples and 0.095 kg/m2 for treated samples, indicating a significant 99.92% reduction in erosion due to the formation of an alkali-activated cement crust on the soil surface. However, exposure of the samples to 120 mm/h rainfall for 90 min resulted in a 5.2-fold increase in wind erosion compared to pre-rainfall conditions. Similarly, penetrometer results indicated a 37%–54% reduction in post-rainfall surface strength.
基金the National Key R&D Program of China(No.2017YFC0601302)the Research Start-up Project for Introduced Talent of Yunnan University(No.20190043)the Australian Research Council to Zheng-Xiang Li(Nos.DP0770228,FL150100133)。
文摘The evolution of continental crust can be directly linked to the first-order supercontinent-superplume cycles.We demonstrate that:(1)a mantle-like oxygen isotopic signature is not a diagnostic feature for distinguishing crustal addition from the reworking of pre-existing continental crust;(2)juvenile continental crust shows a wide range of whole-rock Hf isotopic compositions throughout Earth's history;and(3)detrital zircon Hf model ages cannot reliably determine the growth of continental crust.Thus,the wide use of zircon Hf model ages,based on zircon grains with mantle-like oxygen isotopes,is inappropriate for estimating the timing of continental crustal generation.Based on an analysis of global Hf and O isotope and zircon age databases,we argue that the actual U-Pb crystallization ages of juvenile zircon grains provide the best opportunity to unravel crustal growth through time and to test its relationship with supercontinent-superplume cycles.Furthermore,when the Hf isotopes of these juvenile grains plot within the field of juvenile continental crust,they correlate well with times of global mantle depletion as recorded by Os and He isotopes,plume activity as recorded by LIP events,and periods of crustal growth and the breakup of supercontinents.In contrast,zircon grains crystallized from magmas that were produced by partial melting of pre-existing continental crust show U-Pb age peaks that correspond mainly to times of supercontinent assembly and crustal reworking.Detailed analysis shows the key role played by recycling of mafic crustal components in the generation of juvenile continental crust.
基金supported by grants from NSFC(91958215)Shandong Basic Research Office(WSR2023018)the Ministry of Education 111 Project(B18048).
文摘We must persevere to drill through the intact ocean crust to fully address fundamental questions towards completion of the plate tectonics theory.The primary questions include:what is the ocean crust made up of,how thick is it and what is the petrological nature of the crust-mantle boundary(i.e.,Mohorovičićdiscontinuity or Moho)?These questions may sound naive because they are widely believed to be well-understood facts,but they are not.Correctly,our current knowledge remains incomplete,and some popular misperceptions come from interpretations based on convenient assumptions.One assumption is that the ocean crust inferred from seismic data is of magmatic origin.Testing this assumption is a principal motivation of Project Mohole(1957-1966),attempting to drill intact ocean crust across the Moho into the mantle.Project Mohole failed because of its high cost,engineering challenges and insufficient tries,but the technologies developed made subsequent ocean drilling successful.However,answers to the original questions remain unsatisfactory.For example,seismic crust interpreted to be of magmatic origin is shown to have globally uniform thickness of 6.0±1.0 km,but crust with such thickness at many slow-spreading ridge segments is dominated by serpentinized mantle peridotites exposed on seafloors.Therefore,the popular view on ocean ridge magmatism must be re-examined,which needs intact ocean crust drilling into the mantle.Drilling at geologically simple sites in the fast-spreading Pacific seafloor is most promising.The US-led D/V JOIDES Resolution that has well served the scientific ocean drilling since 1985 is to retire by the end of 2024,but timely the Chinese geoscience community wishes to continue this international endeavor using the purpose-built D/V Meng Xiang to be in service in 2025.The international community is to gather in November 24-27,2024,Guangzhou,China,to discuss strategies on where and how to successfully drill intact ocean crust across the Moho in coming years.
基金National Natural Science Foundation of China,Grant Number:42107077Young Scholar Development Project of the Ecological Society of China,Grant Number:2020Talent Introduction Project of Yunnan University,Grant Number:CZ22623101.
文摘Physical soil crust(PSC),a key component of surface soil structure,exists extensively in loess areas.PSC is considered to have a significant effect on soil detachment processes.However,the long-term effects and the corresponding mechanisms of PSC on soil detachment by overland flow are still not well understood,especially in natural environments.To investigate temporal variation in soil erosion resistance and the underlying factors during PSC formation,an 8×8-m soil plot was exposed to natural conditions in the Loess Plateau over a 524-day period spanning two rainy seasons and a winter between them.A flume test was conducted to determine soil detachment capacity(Dc)under six designed flow shear stress levels(5.66-22.11 Pa)using crusted(SC)and non-crusted(NSC)soil samples at different PSC development stages.Subsequently,two soil erosion resistance parameters,rill erodibility(K_(r))and critical shear stress(τ_(c)),were calculated.Over time,in the SC and NSC treatments,K_(r)decreased from 0.516 to 0.120 s m^(-1)and 0.521 to 0.223 s m^(-1),respectively,whileτ_(c)increased from 0.49 to 4.42 Pa and 0.26-2.46 Pa,respectively.Variation in soil erosion resistance was rapid in the first one to two months,and then slowed down,with slight fluctuations afterwards.In the SC treatment,K_(r)was 42%lower andτ_(c)was 67%greater than those in the NSC treatment.Soil properties changed greatly for both treatments.SCT increased from 0 to 7.09 mm in the SC treatment.Coh increased from 2.91 to 9.04 kPa and 3.01-4.78 kPa in SC and NSC treatments,respectively.Both soil erosion resistance parameters could be well predicted by SCT and Coh in the SC treatment(R^(2)≥0.82),while their best predictor was Coh in the NSC treatment(R^(2)≥0.90).The results demonstrate that PSC formation enhances soil erosion resistance in the soil detachment process in the loess region under natural conditions.Our study revealed the important role and complexity of PSC in the process of soil erosion,and provided theoretical and data support for accurate understanding and prediction of soil erosion.
基金GP-2012-004 of Korea Institute of Geoscience and Mineral Resources(Republic of Korea)Beijing SHRIMP Center(China)+16 种基金Brain Pool Program of the Korea Foundation for Science and Technology(Republic of Korea)Centre for Russian and Central EurAsian Mineral Studies(CERCAMS)of the Natural History Museum of London(UK)China Geological Survey ProjectsChinese National Basic Research 973 ProgramHong Kong Research Grant Council,Hong Kong UniversityGerman Science Foundation(DFG)Institute of Geology and Mineralogy SB RAS(Novosibirsk,Russia)research projectsInstitute of Precambrian Geology and Geochronology RAS(St.-Petersburg,Russia)International Union of Geosciences(IUGS)KASKAD Industrial-Technological Centre(Russia)Ministry of Education,Culture,Sports,ScienceTechnology of Japan,National 305 Project of ChinaNational Natural Science Foundation of ChinaNovosibirsk State University(Russia)Siberian and Far-East Branches of the Russian Academy of Sciences,Russian Foundation for Basic Research(RFBR)Science Research GeoTechnology Center of Vladivostok(Russia)UNESCO.
文摘IGCP-Project#592(2012-2015)“Continental construction in Central Asia”,funded by UNESCOIUGS,was launched in April 2012.The Project focuses on tectonic and magmatic aspects of formation of continental crust in the Central Asian Orogenic Belt and their comparison with actualistic examples from the western Pacific.This report summarizes related scientific results and meetings.In total,in 2012 the Project organized,and/or participated in the organization of,six international conferences and workshops,three of which were accompanied by training schools for young scientists and special training courses.At the present time,more than 250 scientists from 27 countries expressed their interest to collaborate in the frame of our Project,of which more than one third are women and young scientists.Participants come from Australia,Bangladesh,Belgium,Canada,China,Czech Republic,Fiji,Finland,France,Germany,India,Indonesia,Iran,Japan,Kazakhstan,Kyrgyzstan,Mongolia,New Zealand,Poland,Philippines,Republic of Korea,Russia,Tajikistan,Turkey,United Kingdom,USA,and Uzbekistan.In order to carry out research and to secure meeting activities,project participants received funding from national and international sources and mining companies.Below we also present a short overview of meetings scheduled for 2013.
文摘Whilst caking occurs via several different mechanisms,absorption and migration of moisture is frequently the most dominant mechanism within the food and pharmaceutical industry.Fully understanding the propensity to cake is important for minimising down-stream process issues,however most characterisation techniques assume that moisture induced caking occurs homogenously through the sample resulting in a uniformly caked powder bed.In this study,the effect of moisture induced caking on powder flowability was investigated using powder rheology.Several materials,including skimmed milk powder(SMP)and sulphated methyl ester(SME)were stored for several days under controlled humidity conditions.The flow energies,a measure of the resistance to flow,were measured at 24 h intervals using an FT4 Powder Rheometer.As the energy is measured as a function of the bed height,variations in the powder bed are also captured.The results demonstrated that caking does not always occur uniformly,instead a caked region(or crust)forms at the air-powder interface and then progresses through the powder bed.Furthermore,the strength of this caked region was shown to increase over several days before stabilising.
