Soil respiration(SR) is a major process of carbon loss from dryland soils, and it is closely linked to precipitation which often occurs as a discrete episodic event. However, knowledge on the dynamic patterns of SR of...Soil respiration(SR) is a major process of carbon loss from dryland soils, and it is closely linked to precipitation which often occurs as a discrete episodic event. However, knowledge on the dynamic patterns of SR of biologically-crusted soils in response to precipitation pulses remains limited. In this study, we investigated CO_2 emissions from a moss-crusted soil(MCS) and a cyanobacterialichen-crusted soil(CLCS) after 2, 4, 8, 16, and 32 mm precipitation during the dry season in the Tengger Desert, northern China.Results showed that 2 h after precipitation, the SR rates of both MCS and CLCS increased up to 18-fold compared with those before rewetting, and then gradually declined to background levels; the decrease was faster at lower precipitation amount and slower at higher precipitation amount. The peak and average SR rates over the first 2 h in MCS increased with increasing precipitation amount, but did not vary in CLCS. Total CO_2 emission during the experiment(72 h) ranged from 1.35 to 5.67 g C m-2 in MCS, and from 1.11 to3.19 g Cm^(-2) in CLCS. Peak and average SR rates, as well as total carbon loss, were greater in MCS than in CLCS. Soil respiration rates of both MCS and CLCS were logarithmically correlated with gravimetric soil water content. Comparisons of SR among different precipitation events, together with the analysis of long-term precipitation data, suggest that small-size precipitation events have the potential for large short-term carbon losses, and that biological soil crusts might significantly contribute to soil CO_2 emission in the water-limited desert ecosystem.展开更多
In the semi-arid tropics (SAT),33% areas are occupied by Alfisols and related soils. In SAT these soils have low structural stability and thereby tend to form seal and crusts at the surface. Due to this a large propor...In the semi-arid tropics (SAT),33% areas are occupied by Alfisols and related soils. In SAT these soils have low structural stability and thereby tend to form seal and crusts at the surface. Due to this a large proportion of the rain that falls on Alfisols during the early part of the rainy season,is normally lost as runoff thus causing high soil loss as well as moisture stress to crops. Two tillage studies were conducted first at plot scale (320 m2) during 1991-95 and second at small watershed scale (1.45 ha) during 2007-10,at ICRISAT research station,Hyderabad,India. These studies were conducted to find out whether the problem of excessive runoff and soil loss during the early part of the rainy season can be controlled by various inter-row tillage systems in addition to normal intercultivation by breaking the crust or seal and thereby improving infiltration and soil moisture and reducing runoff and soil loss. The observations on rainfall,runoff,soil moisture,soil loss,soil surface roughness and crop yields were collected from both the studies. Results from these studies have shown that inter-row tillage in addition to normal intercultivation is found effective in controlling early season runoff and soil loss and increasing crop yields. The additional tillage systems are found most effective during low and medium rainfall years and not so much during high rainfall years. The additional tillage with shoe cultivators,which creates rough soil surface (11 mm depression storage),is found most effective in increasing crop yields and reducing runoff and soil loss. The additional tillage with blade harrow which generates smooth soil surface is relatively less effective. In most rainfall conditions,the normal intercultivation with one additional tillage is found adequate for controlling early season runoff and improving soil moisture and crop yields.展开更多
Playas are common in many arid regions and recognized as a major source of hypersaline particles.A better understanding of wind erosion on crusted playas has significant implications for land management and pollution ...Playas are common in many arid regions and recognized as a major source of hypersaline particles.A better understanding of wind erosion on crusted playas has significant implications for land management and pollution control practices.We hypothesized that wind erosion rates of crusted playas were complicated and controlled by the interactions between playa crust and wind-induced saltation conditions.However,comparisons regarding the effects of different playa crusts on wind erosion under no saltation(NS)and with saltation(WS)conditions were lacking.In this study,laboratory wind tunnel experiments were carried out to simulate both NS and WS conditions,to investigate the erosion rates of different crust types(Salt,Takyr,and Puffic crust)at different wind speeds.Results showed that:1)Salt crust had greater crust strengths than did Takyr crust and Puffic crust;2)wind erosion rates under the WS condition were up to 60 times greater than those under the NS condition,suggesting that sand bombardment was the dominant mechanism responsible for removal of fine material from crusted playa surfaces;3)both sand bombardment rate and wind erosion rate of the playa crusts increased with increasing wind speed under the WS conditions;4)Puffic crust exhibited a greater rate of wind erosion compared to both the Takyr and Salt crusts under the Ns condition,yet tended to have a lower rate of wind erosion compared to both the Takyr and Salt crusts under the WS condition.This difference can be attributed to the fact that soft Puffic crusts are pliable and can dissipate the force of impacting grains under the Ws conditions.Our results indicated that wind erosion processes on crusted playas are complicated and are affected by wind-induced saltation and crust type,specifically crust strength and elasticityofthesurface.展开更多
Introduction:Nitrogen fixation by microorganisms within biological soil crust(“biocrust”)communities provides an important pathway for N inputs in cool desert environments where soil nutrients are low and symbiotic ...Introduction:Nitrogen fixation by microorganisms within biological soil crust(“biocrust”)communities provides an important pathway for N inputs in cool desert environments where soil nutrients are low and symbiotic N-fixing plants may be rare.Estimates of N fixation in biocrusts often greatly exceed that of N accretion rates leading to uncertainty regarding N loss pathways.Methods:In this study we examined nitrogen fixation and denitrification rates in biocrust communities that differed in N fixation potential(low N fixation=light cyanobacterial biocrust,high N fixation=dark cyanolichen crust)at four temperature levels(10,20,30,40°C)and four simulated rainfall levels(0.05,0.2,0.6,1 cm rain events)under controlled laboratory conditions.Results:Acetylene reduction rates(AR,an index of N fixation activity)were over six-fold higher in dark crusts relative to light crusts.Dark biocrusts also exhibited eight-fold higher denitrification rates.There was no consistent effect of temperature on denitrification rates,but there was an interactive effect of water addition and crust type.In light crusts,denitrification rates increased with increasing water addition,whereas the highest denitrification rates in dark crusts were observed at the lowest level of water addition.Conclusions:These results suggest that there are no clear and consistent environmental controls on short-term denitrification rates in these biologically crusted soils.Taken together,estimates of denitrification from light and dark biocrusts constituted 3 and 4%of N fixation rates,respectively suggesting that losses as denitrification are not significant relative to N inputs via fixation.This estimate is based on a previously published conversion ratio of ethylene produced to N fixed that is low(0.295),resulting in high estimates of N fixation.If future N fixation studies in biologically crusted soils show that these ratios are closer to the theoretical 3:1 ratio,denitrification may constitute a more significant loss pathway relative to N fixed.展开更多
The Tan-Lu Fault Zone is a large NNE-trending fault zone that has a substantial effect on the development of eastern China and its earthquake disaster prevention efforts. Aiming at the azimuthally anisotropic structur...The Tan-Lu Fault Zone is a large NNE-trending fault zone that has a substantial effect on the development of eastern China and its earthquake disaster prevention efforts. Aiming at the azimuthally anisotropic structure in the upper crust and seismogenic tectonics in the Hefei segment of this fault, we collected phase velocity dispersion data of fundamental mode Rayleigh waves from ambient noise cross-correlation functions of ~400 temporal seismographs in an area of approximately 80 × 70 km along the fault zone. The period band of the dispersion data was ~0.5–10 s. We inverted for the upper crustal three-dimensional(3-D) shear velocity model with azimuthal anisotropy from the surface to 10 km depth by using a 3-D direct azimuthal anisotropy inversion method. The inversion result shows the spatial distribution characteristics of the tectonic units in the upper crust. Additionally, the deformation of the Tan-Lu Fault Zone and its conjugated fault systems could be inferred from the anisotropy model. In particular, the faults that have remained active from the early and middle Pleistocene control the anisotropic characteristics of the upper crustal structure in this area. The direction of fast axes near the fault zone area in the upper crust is consistent with the strike of the faults, whereas for the region far away from the fault zone, the direction of fast axes is consistent with the direction of the regional principal stress caused by plate movement. Combined with the azimuthal anisotropy models in the deep crust and uppermost mantle from the surface wave and Pn wave, the different anisotropic patterns caused by the Tan-Lu Fault Zone and its conjugated fault system nearby are shown in the upper and lower crust. Furthermore,by using the double-difference method, we relocated the Lujiang earthquake series, which contained 32 earthquakes with a depth shallower than 10 km. Both the Vs model and earthquake relocation results indicate that earthquakes mostly occurred in the vicinity of structural boundaries with fractured media, with high-level development of cracks and small-scale faults jammed between more rigid areas.展开更多
Do you know any old wives'tales?You probably heard them from your mom.And she heard them from her mom.Many of these tales aren't true,but we talk about them anyway.For example,don't go outside with wet hai...Do you know any old wives'tales?You probably heard them from your mom.And she heard them from her mom.Many of these tales aren't true,but we talk about them anyway.For example,don't go outside with wet hair,or you'll catch a cold.If you drop food and pick it up in under five seconds,it is safe to eat.You should eat a lot when you have a cold,but only eat a little when you have a fever.And eating bread crusts makes your hair curly.展开更多
The high Ba-Sr rocks can provide significant clues about the evolution of the continent lithosphere,but their petrogenesis remains controversial.Identifying the Late Cretaceous high Ba-Sr granodiorites in the SE Lhasa...The high Ba-Sr rocks can provide significant clues about the evolution of the continent lithosphere,but their petrogenesis remains controversial.Identifying the Late Cretaceous high Ba-Sr granodiorites in the SE Lhasa Block could potentially provide valuable insights into the continent evolution of the Qinghai-Tibet Plateau.Zircon U-Pb ages suggest that the granodiorites were emplaced at 87.32±0.43 Ma.Geochemically,the high Ba-Sr granodiorites are characterized by elevated K_(2)O+Na_(2)O contents(8.18-8.73 wt%)and K_(2)O/Na_(2)O ratios(0.99-1.25,mostly>1),and belong to high-K calc-alkaline to shoshonitic series.The Yonglaga granodiorites show notably high Sr(653-783 ppm)and Ba(1346-1531 ppm)contents,plus high Sr/Y(30.92-38.18)and(La/Yb)_(N)(27.7-34.7)ratios,but low Y(20.0-22.8 ppm)and Yb(1.92-2.19 ppm)contents with absence of negative Eu anomalies(δEu=0.83-0.88),all similar to typical high Ba-Sr granitoids.The variable zirconεHf(t)values of-4.58 to+12.97,elevated initial^(87)Sr/^(86)Sr isotopic ratios of 0.707254 to 0.707322 and lowεNd(t)values of-2.8 to-3.6 with decoupling from the Hf system suggest that a metasomatized mantle source included significant recycled ancient materials.The occurrence of such high Ba-Sr intrusions indicates previous contributions of metasomatized mantle-derived juvenile material to the continents,which imply the growth of continental crust during the Late Cretaceous in the SE Lhasa.Together with regional data,we infer that the underplated mafic magma provides a significant amount of heat,which leads to partial melting of the juvenile crust.The melting of the metasomatized mantle could produce a juvenile mafic lower crust,from which the high Ba-Sr granitoids were derived from reworking of previous mafic crust during the Late Cretaceous(ca.100-80 Ma)in the SE Lhasa.展开更多
The Cretaceous andesites were discovered in the Biluocuo area,and provided key records to understand the late Mesozoic geodynamic evolution and crustal basement for the southern Qiangtang block in the central Xizang.I...The Cretaceous andesites were discovered in the Biluocuo area,and provided key records to understand the late Mesozoic geodynamic evolution and crustal basement for the southern Qiangtang block in the central Xizang.In this study,we present a detailed study of zircon U-Pb dating,major and trace elemental composition,and Sr-Nd-Hf isotopes for the Biluocuo trachy-andesites.The trachy-andesites yielded zircon U-Pb ages at ca.97 Ma,and exhibited SiO_(2)contents ranging from 55.92 to 69.04 wt%,low TiO_(2)contents(0.37 to 0.75 wt%)and low Mg~#values(18.6 to 53.7),suggesting that they belong to high-K calc-alkaline series.They showed adakitic signatures,such as high Sr/Y ratios(almost 24 to 55)and low Y(<20 ppm),implying they were generated at great depths(>15 kbar).The samples have initial Sr isotopic ratios of 0.70963 to 0.70964,εNd(t)values of-4.7 to-4.6,and zirconεHf(t)values of-1.2 to+1.3 with two-stage Hf model ages of 0.95 to 1.09 Ga.Elemental and Sr-Nd-Hf isotopic signatures suggest that the trachy-andesites were derived from the partial melting of the thickened lower crust with involvement of metasomatized mantle components.Combined with coeval highMg andesites,we proposed that underplating of mantle induced melting of the lower crust at ca.97 Ma in the southern Qiangtang block,following by lithospheric delamination.Inherited/xenocrystic zircons from the trachy-andesites revealed magmatic activities at 2562 Ma,1850-1804 Ma,1768-1665 Ma,1043-935 Ma,851-736 Ma and 642-540 Ma.There is a Precambrian crustal basement in the southern Qiangtang block,which may have experienced the assembly and break-up of the Columbia,Rodinia,and Gondwana supercontinents.展开更多
Aluminum is the main impurity of the weathered crust elution-deposited rare earth ore(WCED-REO).Efficient leaching of rare earths and low leaching of aluminum are of great importance for the leaching of the WCED-REO.T...Aluminum is the main impurity of the weathered crust elution-deposited rare earth ore(WCED-REO).Efficient leaching of rare earths and low leaching of aluminum are of great importance for the leaching of the WCED-REO.The effects of pH,MgSO_(4) concentration and Al^(3+)concentration of the leaching agent solution on the column leaching behaviors of WCED-REO using magnesium sulfate were investigated.Experimental data show that controlling the MgSO_(4) concentration to 0.15 mol/L,pH of the leaching agent solution to 2,the leaching amount of aluminum from the rare earth ore gradually decreases with the increase of Al^(3+)concentration in the leaching agent solution,indicating that Al^(3+)in the leaching agent solution may act as leaching agent to participate in the ion exchange of RE3+,but the leaching amounts of rare earths change insignificantly as the Al^(3+)concentration is increased.Increasing the MgSO_(4) concentration is beneficial to the leaching of aluminum,and when the Al^(3+)concentration is 0.04 mol/L(Al accumulation),the amount of Al^(3+)leached from the rare earth ore increased gradually with increasing the MgSO_(4) concentration.The pH of the leaching agent solution has a significant influence on the leaching of aluminum in the rare earth ore,and the leaching amount of aluminum from the rare earth ore increases gradually with decreasing the pH.When the Al^(3+)conce ntration is 0.04 mol/L(Al accumulation)and the pH of the leaching agent solution is above 2.0,the aluminum in the leaching agent solution can be back-adsorbed onto the rare earth ore,and the amount of the back-adsorbed Al^(3+)increases with increasing the pH of the leaching agent solution.The injection rate of the leaching agent solution has slight effect on the leaching behavior of rare earths and aluminum.In summary,leaching of Al^(3+)and consumption of MgSO_(4) can be reduced by regulating the accumulation of aluminum,MgSO_(4) concentration and pH.展开更多
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
To solve the problems of the long development period,low mass transfer efficiency and high impurity conte nt in the in-situ leaching process of weathe red crust elution-deposited rare earth ores(WCE-DREO),cationic hyd...To solve the problems of the long development period,low mass transfer efficiency and high impurity conte nt in the in-situ leaching process of weathe red crust elution-deposited rare earth ores(WCE-DREO),cationic hydroxyethyl cellulose(PQ-10)was composited with conventional leaching agent ammonium sulfate((NH_(4))_(2)SO_(4))to form a novel composite leaching agent.The effects of PQ-10 concentration,leaching temperature and leaching flow rate of the composite leaching agent on the leaching kinetics and mass transfer processes of rare earth(RE)and aluminum(Al)were investigated.Compared to the single leaching agent(NH_(4))_(2)SO_(4),the composite leaching agent(2 wt%(NH_(4))_(2)SO_(4)+0.02 wt%PQ-10)can reduce the RE leaching equilibrium time from 465 to 130 min and increase the RE leaching efficiency and decrease the Al leaching efficiency.It also facilitates the leaching process of WCE-DREO by increasing the peak concentrations of RE and Al,reducing the theoretical tower plate height(HETP)and improving the leaching mass transfer efficiency.It is indicated that PQ-10 can promote the leaching of WCE-DREO.The leaching process of the composite leaching system conforms to the diffusion kinetic control model.When the PQ-10 concentration is in the range of 0.005 wt%-0.020 wt%,the reaction orders of RE and Al are 0.73 and 0.54,respectively,which shows a positive effect on the leaching velocity;when the PQ-10 concentration is in the range of 0.030 wt%-0.060 wt%,the reaction orders of RE and Al are-1.16 and-0.75,respectively,which show a negative effect on the leaching velocity.In the range of 10-50℃,the apparent activation energies of RE and Al are 15.02 and 17.31 kJ/mol,respectively,and the higher the leaching temperature,the smaller the HETP and the higher the leaching velocity and mass transfer efficiency.The increase in leaching flow rate contributes to the increase in the longitudinal diffusion velocity of the leaching agent within WCE-DREO,causing a shorter time for RE and Al to reach leaching equilibrium.In addition,the flow rate and HETP are consistent with the Van Deemter equation.At a flow rate of 0.8 mL/min,HETP was minimized and the optimal mass transfer efficiencies is achieved for RE and Al.展开更多
Artificial cyanobacteria crusts are formed by inoculating soil with cyanobacteria.These crusts help prevent soil erosion and restore soil functionality in degraded croplands.However,how fast the artificial cyanobacter...Artificial cyanobacteria crusts are formed by inoculating soil with cyanobacteria.These crusts help prevent soil erosion and restore soil functionality in degraded croplands.However,how fast the artificial cyanobacteria crusts can be formed is a key issue before their practical application.In addition,the effects of artificial cyanobacteria crusts on soil nutrients and plant growth are not fully explored.This study analyzed the effect of inoculation of cyanobacteria from local biological soil crusts on soil nutrients and Pak-choi(Brassica campestris L.ssp.Chinensis Makino var.communis Tsen et Lee;Chinese cabbage)growth in a cropland,northern China through field experiments by comparing with no fertilizer.The results showed that artificial cyanobacteria crusts were formed on the 18th d after inoculation with a coverage of 56.13%,a thickness of 3.74 mm,and biomass of 22.21μg chla/cm^(2).Artificial cyanobacteria crusts significantly improved the soil organic matter(SOM),NO_(3)^(-)-N,total nitrogen(TN)contents,and the activities of sucrase,alkaline phosphatase,urease,and catalase enzymes of plants on the 50th d after inoculation.Additionally,artificial cyanobacteria crusts led to an increase in plant biomass,improved root morphology,and raised the phosphorus and potassium contents in the plants.Furthermore,the biomass of plant grown with artificial cyanobacteria crusts was comparable with that of grown with chemical fertilizer.The study suggested that,considering plant biomass and soil nutrients,it is feasible to prevent wind erosion in the cropland of arid and semi-arid areas by inoculating cyanobacteria crusts.This study provides new perspectives for the sustainable development and environmental management of cropland in arid and semi-arid areas.展开更多
Weijia Guyot,located in the western Pacific Ocean,has become a research focus due to its abundant cobalt-rich ferromanganese(Fe-Mn)crusts.While most studies on Fe-Mn crusts on seamounts have focused on the exposed var...Weijia Guyot,located in the western Pacific Ocean,has become a research focus due to its abundant cobalt-rich ferromanganese(Fe-Mn)crusts.While most studies on Fe-Mn crusts on seamounts have focused on the exposed variety,less attention has been paid to potential buried crusts.This study presents a preliminary geochemical and chronological study of buried Fe-Mn crusts at Weijia Guyot.The findings suggest that these buried crusts began to form around 57.5 Ma and ceased growing at approximately 46.3 Ma.Following the formation of Weijia Guyot through volcanic eruption,it did not experience continuous and steady subsidence to its current depth.Instead,an exhumation process took place from deep to shallow depths between 46.3 and 11.6 Ma.This process brought the Fe-Mn crusts into shallow water environments,halting their growth.During this time,Weijia Guyot was located near the equatorial Pacific Ocean and was exposed to an extended period of phosphatization.This exposure led to a depletion of key metallogenic elements,such as Co,Ni and Cu,within the Fe-Mn crusts,while P2O5 and CaO levels increased significantly.Since the Middle Miocene,the crusts have been progressively buried by pelagic sediments.展开更多
Bauxite mining will bring huge economic benefit,but it also faces the risk of environmental pollution.Metal pollution problem has been widely concerned in bauxite tailing areas.Biodiversity indices,metal concentration...Bauxite mining will bring huge economic benefit,but it also faces the risk of environmental pollution.Metal pollution problem has been widely concerned in bauxite tailing areas.Biodiversity indices,metal concentrations of moss crusts,and soil contamination indices in Wachangping bauxite tailing areas in Guizhou Province,China were measured and analyzed.In a total of 40 species belonging to 19 genera and 12 families of moss in the study areas,Ditrichum flexicaule(Schwaegr.)Hamp.(DF),Oxystegus cylindricus(Brid.)Hilp.(OC),and Ditrichum brevidens Nog.(DB)are the dominant moss crusts.Moss species diversity in different habitats has a certain regularity:waste residues area<waste rocks area<ore stockpile area<slope shrub area<shrub area by gutter<slope shrub herbaceous area.Sorenson diversity index(β)of moss species is influenced by microenvironment and substrate.Concentrations of Al,Mg,Ca,Fe,K,and Ti are the largest in DB(2,990 to 73,210 mg kg^(-1)),followed by those in DF(2,900 to 61,890 mg kg^(-1)),and are the smallest in OC(690 to 32,240 mg kg^(-1)),which show that the three moss crusts have different bioaccumulation capacities.Metal contents in underlying soils of moss crusts are higher than the background levels.Bioaccumulation factor(BAF)of Al,Mg,Ca,Fe,and K in three moss crusts are decreased in the following order:DB>DF>OC.Single factor pollution index(Ps)and Nemero comprehensive pollution index(Pc)of six metal are much greater than 3,and the index of geoaccumulation(Igeo)(1geo<5)reveals that the soil environment is at moderately to seriously contaminated levels.Principal components analysis(PCA)shows that there is no significant correlation between p H value,and metal contents(Al,Mg,Fe,K and Ti),soil temperature(ST)and metal contents(Al,Mg,Fe,K and Ti).Soil humidity(SH)is negatively correlated with metal contents(Al,Mg,Fe,K and Ti).These three environmental factors have little effect on the distribution of metal.Result also reflects that DB moss is readily able to both tolerate and accumulate metal,which makes it a suitable bioindicator of multiple metal contamination in Wachangping bauxite tailing areas.展开更多
Biological soil crusts(BSCs)play crucial roles in improving soil fertility and promoting plants settlement and reproduction in arid areas.However,the specific effects of BSCs on growth status and nutrient accumulation...Biological soil crusts(BSCs)play crucial roles in improving soil fertility and promoting plants settlement and reproduction in arid areas.However,the specific effects of BSCs on growth status and nutrient accumulation of plants are still unclear in different arid areas.This study analyzed the effects of three different BSCs treatments(without crust(WC),intact crust(IC),and broken crust(BC))on the growth,inorganic nutrient absorption,and organic solute synthesis of three typical desert plants(Grubovia dasyphylla(Fisch.&C.A.Mey.)Freitag&G.Kadereit,Nitraria tangutorum Bobrov,and Caragana koraiensis Kom.)in the Minqin desert-oasis ecotone of Northwest China.Results showed that the effects of three BSCs treatments on seed emergence and survival of three plants varied with seed types.The IC treatment significantly hindered the emergence and survival of seeds,while the BC treatment was more conducive to seed emergence and survival of plants.BSCs significantly promoted the growth of three plants,but their effects on plant growth varied at different stages of the growth.Briefly,the growth of G.dasyphylla was affected by BSCs in early stage,but the effects on the growth of G.dasyphylla significantly weakened in the middle and late stages.However,the growth of N.tangutorum and C.koraiensis only showed differences at the middle and late stages,with a significant enhancement in growth.Analysis of variance showed that BSCs,plant species,growth period,and their interactions had significant effects on the biomass and root:shoot ratio of three plants.BSC significantly affected the nutrients absorption and organic solute synthesis in plants.Specifically,BSCs significantly promoted nitrogen(N)absorption in plants and increased plant adaptability in N poor desert ecosystems,but had no significant effects on phosphorus(P)absorption.The effects of BSCs on inorganic nutrient absorption and organic solute synthesis in plants varied significantly among different plant species.The results suggest that BSCs have significant effects on the growth and nutrient accumulation of desert plants,which will provide theoretical basis for exploring the effects of BSCs on desert plant diversity,biodiversity conservation,and ecosystem management measures in arid and semi-arid areas.展开更多
The Yarlung Zangbo Suture Zone(YZSZ)on the southern margin of the Lhasa block and the Tangjia-Sumdo ultrahigh-pressure metamorphic belt(TSMB)within the block represent natural laboratories for the study of plate tecto...The Yarlung Zangbo Suture Zone(YZSZ)on the southern margin of the Lhasa block and the Tangjia-Sumdo ultrahigh-pressure metamorphic belt(TSMB)within the block represent natural laboratories for the study of plate tectonics and oceanic slab subduction.It is generally believed that these two zones represent the remnants of the ancient oceanic crust and upper mantle of the Yarlung Zangbo Neo-Tethys(YZNT)and the Tangjia-Sumdo Paleo-Tethys(TSPT).However,the evolutionary patterns and spatiotemporal relationships of the TSPT and the YZNT have been debated.展开更多
In this paper,a multi-stage leaching process for the weathered crust elution-deposited rare earth ore was proposed using MgSO_(4)as a leaching agent.The results indicate that with increasing the concentration of MgSO_...In this paper,a multi-stage leaching process for the weathered crust elution-deposited rare earth ore was proposed using MgSO_(4)as a leaching agent.The results indicate that with increasing the concentration of MgSO_(4)from 0.5 wt%-1.0 wt%to 2.0 wt%-4.0 wt%,the peak concentrations of rare earths increase from 1.87 to 3.59 to 5.49-10.21 g/L,and the collection periods of leach solution are sho rtened from 0.85 to 1.54 to 0.31-0.47(liquid-to-ore ratio).When the rare earth ore is leached with leaching agent solution with high initial pH(3.0-5.0),the rare earths and aluminum are predominantly leached by Mg^(2+)instead of H+.However,H+participate in the leaching process of rare earths and aluminum at lower initial pH(1.5-3.0)of the leaching agent solution.Especially,when the initial pH of leaching agent solution is 2.0,a large amount of aluminum is leached when the liquid-to-ore ratio is greater than 1.2.Based on the above insights,increasing the initial pH(3.0-5.0)of leaching agent solution in the injection stage using high-concentration MgSO_(4)(>1.0 wt%)can increase the peak concentration of rare earths in the leach solution and shorten the collection period.However,in the injection stage using low MgSO_(4)concentration(<1.0 wt%),an initial pH of leaching agent solution of 2.0 is selected to reduce the leaching amount of aluminum and the consumption of MgSO_(4).Comparing to the Leaching process using constant MgSO_(4)concentration(2.0 wt%,initial pH of 5.0),the leaching efficiency of rare earths using a multi-stage leaching process is approximately equal(about 94.6%)under optimal conditions.The leaching amount of aluminum is reduced by 16.9%.The consumption of MgSO_(4)is reduced by 67.1%.展开更多
Weathered crust elution-deposited rare earth ores(WREOs)are rich in medium and heavy rare earth.In order to improve the in-situ leaching process,which is prone to landslides and poor permeability,cationic hydroxyethyl...Weathered crust elution-deposited rare earth ores(WREOs)are rich in medium and heavy rare earth.In order to improve the in-situ leaching process,which is prone to landslides and poor permeability,cationic hydroxyethyl cellulose(PQ-10)was used as a novel green swelling inhibitor and percolation promoter and was mixed with conventional leaching agent ammonium sulfate((NH_(4))_(2)SO_(4))to form a composite leaching agent to study the performance and mechanism of swelling inhibition and percolation promotion.Adding PQ-10 can inhibit the hydration swelling of WREOs,promote the percolation effect of the leaching agent,improve the rare earth(RE)leaching efficiency,and reduce the im purity aluminum(Al)leaching efficiency.Compared with the conventional leaching agent 2 wt%(NH_(4))_(2)SO_(4),the percolation time is reduced by 50%by using the composite leaching agent(0.02 wt%PQ-10+2 wt%(NH_(4))_(2)SO_(4)).PQ-10 has positively charged quaternary ammonium groups and hydrophilic group hydroxyl groups,which makes it easy to adsorb on WREOs multiple sites through electrostatic interaction and hydrogen bonding,weakening the electrostatic repulsion between mineral particles,reducing the WREOs interlayer spacing,compressing the double electric layer thickness at the solid-liquid interface,weakening the mineral hydration swelling and increasing the percolation rate.The long carbon chains of the polymer entangle and link the fine mineral particles to agglomerate them,increasing their particle size and reduc ing their hydration dispersion,and preventing blockage of the pe rcolation pores caused by migration of the fine particles through the ore body with the solution.PQ-10 molecules also insert the mine ral interlayer and expulsion of the internal water,further inhibiting the swelling of WREOs.Adding PQ-10 reduces the surface tension of(NH_(4))_(2)SO_(4)solution,improving the spreading and spreading ability of the solution,reducing the adhesion work between molecules in the solid-liquid phase and the adhesion work reduction factor.It proves that PQ-10 promotes the percolation effect of the leaching process of WREOs.In addition,PQ-10 expands the leaching pore size and seepage channels,further improving the percolation rate.展开更多
The Anninghe–Zemuhe Fault and the Xiaojiang Fault are critical active faults along the middle-eastern boundary of the South Chuan–Dian Block. Many researchers have identified these faults as potential strong-earthqu...The Anninghe–Zemuhe Fault and the Xiaojiang Fault are critical active faults along the middle-eastern boundary of the South Chuan–Dian Block. Many researchers have identified these faults as potential strong-earthquake risk zones. In this study, we leveraged a dense seismic array to investigate the high-resolution shallow crust shear wave velocity(Vs) structure beneath the junction of the Zemuhe Fault Zone and the Xiaojiang Fault Zone, one of the most complex parts of the eastern boundary of the South Chuan–Dian Block. We analyzed the distribution of microseismic events detected between November 2022 and February 2023 based on the fine-scale Vs model obtained. The microseismicity in the study region was clustered into three groups, all spatially related to major faults in this region. These microseismic events indicate near-vertical fault planes, consistent with the fault geometry revealed by other researchers.Moreover, these microseismic events are influenced by the impoundment of the downstream Baihetan Reservoir and the complex tectonic stress near the junction of the Zemuhe Fault Zone and the Xiaojiang Fault Zone. The depths of these microseismic events are shallower in the junction zone, whereas moving south along the Xiaojiang Fault Zone, the microseismic events become deeper.Additionally, we compared our fine-scale local Vs model with velocity models obtained by other researchers and found that our model offers greater detail in characterizing subsurface heterogeneity while demonstrating improved reliability in delineating fault systems.展开更多
The Middle to Late Jurassic,high-pressure metamorphic ophiolites of Inzecca Unit are well exposed in the Noceta-Vezzani area of Alpine Corsica.These metaophiolites were studied by using a multidisciplinary approach to...The Middle to Late Jurassic,high-pressure metamorphic ophiolites of Inzecca Unit are well exposed in the Noceta-Vezzani area of Alpine Corsica.These metaophiolites were studied by using a multidisciplinary approach to reconstruct the architecture of the oceanic sector from which they derived.The collected data indicate that this oceanic crust consists of a mantle metaperidotites and metaophicalcites,both covered by massive or pillow metabasalts with or without a layer of ophiolite-bearing metabreccias.展开更多
基金financially supported by the National Natural Science Foundation of China (No. 41171078)the Main Direction Program of Knowledge Innovation of Chinese Academy of Sciences (No. KZCX2-EW-301-2)
文摘Soil respiration(SR) is a major process of carbon loss from dryland soils, and it is closely linked to precipitation which often occurs as a discrete episodic event. However, knowledge on the dynamic patterns of SR of biologically-crusted soils in response to precipitation pulses remains limited. In this study, we investigated CO_2 emissions from a moss-crusted soil(MCS) and a cyanobacterialichen-crusted soil(CLCS) after 2, 4, 8, 16, and 32 mm precipitation during the dry season in the Tengger Desert, northern China.Results showed that 2 h after precipitation, the SR rates of both MCS and CLCS increased up to 18-fold compared with those before rewetting, and then gradually declined to background levels; the decrease was faster at lower precipitation amount and slower at higher precipitation amount. The peak and average SR rates over the first 2 h in MCS increased with increasing precipitation amount, but did not vary in CLCS. Total CO_2 emission during the experiment(72 h) ranged from 1.35 to 5.67 g C m-2 in MCS, and from 1.11 to3.19 g Cm^(-2) in CLCS. Peak and average SR rates, as well as total carbon loss, were greater in MCS than in CLCS. Soil respiration rates of both MCS and CLCS were logarithmically correlated with gravimetric soil water content. Comparisons of SR among different precipitation events, together with the analysis of long-term precipitation data, suggest that small-size precipitation events have the potential for large short-term carbon losses, and that biological soil crusts might significantly contribute to soil CO_2 emission in the water-limited desert ecosystem.
文摘In the semi-arid tropics (SAT),33% areas are occupied by Alfisols and related soils. In SAT these soils have low structural stability and thereby tend to form seal and crusts at the surface. Due to this a large proportion of the rain that falls on Alfisols during the early part of the rainy season,is normally lost as runoff thus causing high soil loss as well as moisture stress to crops. Two tillage studies were conducted first at plot scale (320 m2) during 1991-95 and second at small watershed scale (1.45 ha) during 2007-10,at ICRISAT research station,Hyderabad,India. These studies were conducted to find out whether the problem of excessive runoff and soil loss during the early part of the rainy season can be controlled by various inter-row tillage systems in addition to normal intercultivation by breaking the crust or seal and thereby improving infiltration and soil moisture and reducing runoff and soil loss. The observations on rainfall,runoff,soil moisture,soil loss,soil surface roughness and crop yields were collected from both the studies. Results from these studies have shown that inter-row tillage in addition to normal intercultivation is found effective in controlling early season runoff and soil loss and increasing crop yields. The additional tillage systems are found most effective during low and medium rainfall years and not so much during high rainfall years. The additional tillage with shoe cultivators,which creates rough soil surface (11 mm depression storage),is found most effective in increasing crop yields and reducing runoff and soil loss. The additional tillage with blade harrow which generates smooth soil surface is relatively less effective. In most rainfall conditions,the normal intercultivation with one additional tillage is found adequate for controlling early season runoff and improving soil moisture and crop yields.
基金supported by the National Natural Science Foundation of China(Grant Nos.41971120,41730639,42107353)。
文摘Playas are common in many arid regions and recognized as a major source of hypersaline particles.A better understanding of wind erosion on crusted playas has significant implications for land management and pollution control practices.We hypothesized that wind erosion rates of crusted playas were complicated and controlled by the interactions between playa crust and wind-induced saltation conditions.However,comparisons regarding the effects of different playa crusts on wind erosion under no saltation(NS)and with saltation(WS)conditions were lacking.In this study,laboratory wind tunnel experiments were carried out to simulate both NS and WS conditions,to investigate the erosion rates of different crust types(Salt,Takyr,and Puffic crust)at different wind speeds.Results showed that:1)Salt crust had greater crust strengths than did Takyr crust and Puffic crust;2)wind erosion rates under the WS condition were up to 60 times greater than those under the NS condition,suggesting that sand bombardment was the dominant mechanism responsible for removal of fine material from crusted playa surfaces;3)both sand bombardment rate and wind erosion rate of the playa crusts increased with increasing wind speed under the WS conditions;4)Puffic crust exhibited a greater rate of wind erosion compared to both the Takyr and Salt crusts under the Ns condition,yet tended to have a lower rate of wind erosion compared to both the Takyr and Salt crusts under the WS condition.This difference can be attributed to the fact that soft Puffic crusts are pliable and can dissipate the force of impacting grains under the Ws conditions.Our results indicated that wind erosion processes on crusted playas are complicated and are affected by wind-induced saltation and crust type,specifically crust strength and elasticityofthesurface.
基金We would like to thank Heidi Guenther,Matt Ross,and Conor Morrison,who all helped conduct the laboratory experiment.In addition,we would like to thank Will Wieder and the Townsend Lab at the University of Colorado for assistance analyzing gas samples and Dr.William Adams for providing use of laboratory equipment.Finally,we would like to acknowledge the two anonymous reviewers and Dr.Bettina Weber for reviewing the manuscript.
文摘Introduction:Nitrogen fixation by microorganisms within biological soil crust(“biocrust”)communities provides an important pathway for N inputs in cool desert environments where soil nutrients are low and symbiotic N-fixing plants may be rare.Estimates of N fixation in biocrusts often greatly exceed that of N accretion rates leading to uncertainty regarding N loss pathways.Methods:In this study we examined nitrogen fixation and denitrification rates in biocrust communities that differed in N fixation potential(low N fixation=light cyanobacterial biocrust,high N fixation=dark cyanolichen crust)at four temperature levels(10,20,30,40°C)and four simulated rainfall levels(0.05,0.2,0.6,1 cm rain events)under controlled laboratory conditions.Results:Acetylene reduction rates(AR,an index of N fixation activity)were over six-fold higher in dark crusts relative to light crusts.Dark biocrusts also exhibited eight-fold higher denitrification rates.There was no consistent effect of temperature on denitrification rates,but there was an interactive effect of water addition and crust type.In light crusts,denitrification rates increased with increasing water addition,whereas the highest denitrification rates in dark crusts were observed at the lowest level of water addition.Conclusions:These results suggest that there are no clear and consistent environmental controls on short-term denitrification rates in these biologically crusted soils.Taken together,estimates of denitrification from light and dark biocrusts constituted 3 and 4%of N fixation rates,respectively suggesting that losses as denitrification are not significant relative to N inputs via fixation.This estimate is based on a previously published conversion ratio of ethylene produced to N fixed that is low(0.295),resulting in high estimates of N fixation.If future N fixation studies in biologically crusted soils show that these ratios are closer to the theoretical 3:1 ratio,denitrification may constitute a more significant loss pathway relative to N fixed.
基金financially supported by the National Key Research and Development Program of China (2022YFC3005600)the Foundation of the Anhui Educational Commission (2023AH051198)+1 种基金the National Natural Science Foundation of China (42125401 and 42104063)the Joint Open Fund of Mengcheng National Geophysical Observatory (MENGO-202201)。
文摘The Tan-Lu Fault Zone is a large NNE-trending fault zone that has a substantial effect on the development of eastern China and its earthquake disaster prevention efforts. Aiming at the azimuthally anisotropic structure in the upper crust and seismogenic tectonics in the Hefei segment of this fault, we collected phase velocity dispersion data of fundamental mode Rayleigh waves from ambient noise cross-correlation functions of ~400 temporal seismographs in an area of approximately 80 × 70 km along the fault zone. The period band of the dispersion data was ~0.5–10 s. We inverted for the upper crustal three-dimensional(3-D) shear velocity model with azimuthal anisotropy from the surface to 10 km depth by using a 3-D direct azimuthal anisotropy inversion method. The inversion result shows the spatial distribution characteristics of the tectonic units in the upper crust. Additionally, the deformation of the Tan-Lu Fault Zone and its conjugated fault systems could be inferred from the anisotropy model. In particular, the faults that have remained active from the early and middle Pleistocene control the anisotropic characteristics of the upper crustal structure in this area. The direction of fast axes near the fault zone area in the upper crust is consistent with the strike of the faults, whereas for the region far away from the fault zone, the direction of fast axes is consistent with the direction of the regional principal stress caused by plate movement. Combined with the azimuthal anisotropy models in the deep crust and uppermost mantle from the surface wave and Pn wave, the different anisotropic patterns caused by the Tan-Lu Fault Zone and its conjugated fault system nearby are shown in the upper and lower crust. Furthermore,by using the double-difference method, we relocated the Lujiang earthquake series, which contained 32 earthquakes with a depth shallower than 10 km. Both the Vs model and earthquake relocation results indicate that earthquakes mostly occurred in the vicinity of structural boundaries with fractured media, with high-level development of cracks and small-scale faults jammed between more rigid areas.
文摘Do you know any old wives'tales?You probably heard them from your mom.And she heard them from her mom.Many of these tales aren't true,but we talk about them anyway.For example,don't go outside with wet hair,or you'll catch a cold.If you drop food and pick it up in under five seconds,it is safe to eat.You should eat a lot when you have a cold,but only eat a little when you have a fever.And eating bread crusts makes your hair curly.
基金supported by the National Natural Science Foundation of China[Grants.41802054]supported by a Royal Society SinoBritish Fellowship Trust International Exchanges Award[Grant No.IESR3213093]。
文摘The high Ba-Sr rocks can provide significant clues about the evolution of the continent lithosphere,but their petrogenesis remains controversial.Identifying the Late Cretaceous high Ba-Sr granodiorites in the SE Lhasa Block could potentially provide valuable insights into the continent evolution of the Qinghai-Tibet Plateau.Zircon U-Pb ages suggest that the granodiorites were emplaced at 87.32±0.43 Ma.Geochemically,the high Ba-Sr granodiorites are characterized by elevated K_(2)O+Na_(2)O contents(8.18-8.73 wt%)and K_(2)O/Na_(2)O ratios(0.99-1.25,mostly>1),and belong to high-K calc-alkaline to shoshonitic series.The Yonglaga granodiorites show notably high Sr(653-783 ppm)and Ba(1346-1531 ppm)contents,plus high Sr/Y(30.92-38.18)and(La/Yb)_(N)(27.7-34.7)ratios,but low Y(20.0-22.8 ppm)and Yb(1.92-2.19 ppm)contents with absence of negative Eu anomalies(δEu=0.83-0.88),all similar to typical high Ba-Sr granitoids.The variable zirconεHf(t)values of-4.58 to+12.97,elevated initial^(87)Sr/^(86)Sr isotopic ratios of 0.707254 to 0.707322 and lowεNd(t)values of-2.8 to-3.6 with decoupling from the Hf system suggest that a metasomatized mantle source included significant recycled ancient materials.The occurrence of such high Ba-Sr intrusions indicates previous contributions of metasomatized mantle-derived juvenile material to the continents,which imply the growth of continental crust during the Late Cretaceous in the SE Lhasa.Together with regional data,we infer that the underplated mafic magma provides a significant amount of heat,which leads to partial melting of the juvenile crust.The melting of the metasomatized mantle could produce a juvenile mafic lower crust,from which the high Ba-Sr granitoids were derived from reworking of previous mafic crust during the Late Cretaceous(ca.100-80 Ma)in the SE Lhasa.
基金supported by Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project(Grant No.2024ZD1001005)The Central Government Guided Local Scientific and Technological Development Funding Project(Grant No.XZ202401YD0006)+5 种基金Key Research and Development Program(Grant No.XZ202403ZY0040)National Natural Science Foundation of China(Grant No.U24A20597)China Geological Survey(Grant Nos.DD20230024,DD20230315)the Basic Scientific Research Project of Chinese Academy of Geological Sciences(Grant No.JKY202209)Hubei Provincial Natural Science Foundation of China(Grant Nos.2023AFD206,2023AFD230,2024AFD401)the Research Fund Program of Hubei Key Laboratory of Resources and Eco-Environment Geology(Grant No.HBREGKFJJ202302)。
文摘The Cretaceous andesites were discovered in the Biluocuo area,and provided key records to understand the late Mesozoic geodynamic evolution and crustal basement for the southern Qiangtang block in the central Xizang.In this study,we present a detailed study of zircon U-Pb dating,major and trace elemental composition,and Sr-Nd-Hf isotopes for the Biluocuo trachy-andesites.The trachy-andesites yielded zircon U-Pb ages at ca.97 Ma,and exhibited SiO_(2)contents ranging from 55.92 to 69.04 wt%,low TiO_(2)contents(0.37 to 0.75 wt%)and low Mg~#values(18.6 to 53.7),suggesting that they belong to high-K calc-alkaline series.They showed adakitic signatures,such as high Sr/Y ratios(almost 24 to 55)and low Y(<20 ppm),implying they were generated at great depths(>15 kbar).The samples have initial Sr isotopic ratios of 0.70963 to 0.70964,εNd(t)values of-4.7 to-4.6,and zirconεHf(t)values of-1.2 to+1.3 with two-stage Hf model ages of 0.95 to 1.09 Ga.Elemental and Sr-Nd-Hf isotopic signatures suggest that the trachy-andesites were derived from the partial melting of the thickened lower crust with involvement of metasomatized mantle components.Combined with coeval highMg andesites,we proposed that underplating of mantle induced melting of the lower crust at ca.97 Ma in the southern Qiangtang block,following by lithospheric delamination.Inherited/xenocrystic zircons from the trachy-andesites revealed magmatic activities at 2562 Ma,1850-1804 Ma,1768-1665 Ma,1043-935 Ma,851-736 Ma and 642-540 Ma.There is a Precambrian crustal basement in the southern Qiangtang block,which may have experienced the assembly and break-up of the Columbia,Rodinia,and Gondwana supercontinents.
基金Project supported by the Major Research Plan of the National Natural Science Foundation of China(91962211)the National Key Research and Development Program of China(2021YFC2902202)the Key Research and Development Program of Guangxi Province(Guike-AB22080056)。
文摘Aluminum is the main impurity of the weathered crust elution-deposited rare earth ore(WCED-REO).Efficient leaching of rare earths and low leaching of aluminum are of great importance for the leaching of the WCED-REO.The effects of pH,MgSO_(4) concentration and Al^(3+)concentration of the leaching agent solution on the column leaching behaviors of WCED-REO using magnesium sulfate were investigated.Experimental data show that controlling the MgSO_(4) concentration to 0.15 mol/L,pH of the leaching agent solution to 2,the leaching amount of aluminum from the rare earth ore gradually decreases with the increase of Al^(3+)concentration in the leaching agent solution,indicating that Al^(3+)in the leaching agent solution may act as leaching agent to participate in the ion exchange of RE3+,but the leaching amounts of rare earths change insignificantly as the Al^(3+)concentration is increased.Increasing the MgSO_(4) concentration is beneficial to the leaching of aluminum,and when the Al^(3+)concentration is 0.04 mol/L(Al accumulation),the amount of Al^(3+)leached from the rare earth ore increased gradually with increasing the MgSO_(4) concentration.The pH of the leaching agent solution has a significant influence on the leaching of aluminum in the rare earth ore,and the leaching amount of aluminum from the rare earth ore increases gradually with decreasing the pH.When the Al^(3+)conce ntration is 0.04 mol/L(Al accumulation)and the pH of the leaching agent solution is above 2.0,the aluminum in the leaching agent solution can be back-adsorbed onto the rare earth ore,and the amount of the back-adsorbed Al^(3+)increases with increasing the pH of the leaching agent solution.The injection rate of the leaching agent solution has slight effect on the leaching behavior of rare earths and aluminum.In summary,leaching of Al^(3+)and consumption of MgSO_(4) can be reduced by regulating the accumulation of aluminum,MgSO_(4) concentration and pH.
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Project supported by the National Natural Science Foundation of China(U2002215)。
文摘To solve the problems of the long development period,low mass transfer efficiency and high impurity conte nt in the in-situ leaching process of weathe red crust elution-deposited rare earth ores(WCE-DREO),cationic hydroxyethyl cellulose(PQ-10)was composited with conventional leaching agent ammonium sulfate((NH_(4))_(2)SO_(4))to form a novel composite leaching agent.The effects of PQ-10 concentration,leaching temperature and leaching flow rate of the composite leaching agent on the leaching kinetics and mass transfer processes of rare earth(RE)and aluminum(Al)were investigated.Compared to the single leaching agent(NH_(4))_(2)SO_(4),the composite leaching agent(2 wt%(NH_(4))_(2)SO_(4)+0.02 wt%PQ-10)can reduce the RE leaching equilibrium time from 465 to 130 min and increase the RE leaching efficiency and decrease the Al leaching efficiency.It also facilitates the leaching process of WCE-DREO by increasing the peak concentrations of RE and Al,reducing the theoretical tower plate height(HETP)and improving the leaching mass transfer efficiency.It is indicated that PQ-10 can promote the leaching of WCE-DREO.The leaching process of the composite leaching system conforms to the diffusion kinetic control model.When the PQ-10 concentration is in the range of 0.005 wt%-0.020 wt%,the reaction orders of RE and Al are 0.73 and 0.54,respectively,which shows a positive effect on the leaching velocity;when the PQ-10 concentration is in the range of 0.030 wt%-0.060 wt%,the reaction orders of RE and Al are-1.16 and-0.75,respectively,which show a negative effect on the leaching velocity.In the range of 10-50℃,the apparent activation energies of RE and Al are 15.02 and 17.31 kJ/mol,respectively,and the higher the leaching temperature,the smaller the HETP and the higher the leaching velocity and mass transfer efficiency.The increase in leaching flow rate contributes to the increase in the longitudinal diffusion velocity of the leaching agent within WCE-DREO,causing a shorter time for RE and Al to reach leaching equilibrium.In addition,the flow rate and HETP are consistent with the Van Deemter equation.At a flow rate of 0.8 mL/min,HETP was minimized and the optimal mass transfer efficiencies is achieved for RE and Al.
基金supported by the National Key Research and Development Program of China(2022YFF1300802)the National Natural Science Foundation of China(42377357).
文摘Artificial cyanobacteria crusts are formed by inoculating soil with cyanobacteria.These crusts help prevent soil erosion and restore soil functionality in degraded croplands.However,how fast the artificial cyanobacteria crusts can be formed is a key issue before their practical application.In addition,the effects of artificial cyanobacteria crusts on soil nutrients and plant growth are not fully explored.This study analyzed the effect of inoculation of cyanobacteria from local biological soil crusts on soil nutrients and Pak-choi(Brassica campestris L.ssp.Chinensis Makino var.communis Tsen et Lee;Chinese cabbage)growth in a cropland,northern China through field experiments by comparing with no fertilizer.The results showed that artificial cyanobacteria crusts were formed on the 18th d after inoculation with a coverage of 56.13%,a thickness of 3.74 mm,and biomass of 22.21μg chla/cm^(2).Artificial cyanobacteria crusts significantly improved the soil organic matter(SOM),NO_(3)^(-)-N,total nitrogen(TN)contents,and the activities of sucrase,alkaline phosphatase,urease,and catalase enzymes of plants on the 50th d after inoculation.Additionally,artificial cyanobacteria crusts led to an increase in plant biomass,improved root morphology,and raised the phosphorus and potassium contents in the plants.Furthermore,the biomass of plant grown with artificial cyanobacteria crusts was comparable with that of grown with chemical fertilizer.The study suggested that,considering plant biomass and soil nutrients,it is feasible to prevent wind erosion in the cropland of arid and semi-arid areas by inoculating cyanobacteria crusts.This study provides new perspectives for the sustainable development and environmental management of cropland in arid and semi-arid areas.
基金financial support from the National Natural Science Foundation of China(Grant No.U2244222,42576244,42072324,42442603)the Guangzhou Basic and Applied Basic Research Foundation(Grant No.202201011367,202201011487).
文摘Weijia Guyot,located in the western Pacific Ocean,has become a research focus due to its abundant cobalt-rich ferromanganese(Fe-Mn)crusts.While most studies on Fe-Mn crusts on seamounts have focused on the exposed variety,less attention has been paid to potential buried crusts.This study presents a preliminary geochemical and chronological study of buried Fe-Mn crusts at Weijia Guyot.The findings suggest that these buried crusts began to form around 57.5 Ma and ceased growing at approximately 46.3 Ma.Following the formation of Weijia Guyot through volcanic eruption,it did not experience continuous and steady subsidence to its current depth.Instead,an exhumation process took place from deep to shallow depths between 46.3 and 11.6 Ma.This process brought the Fe-Mn crusts into shallow water environments,halting their growth.During this time,Weijia Guyot was located near the equatorial Pacific Ocean and was exposed to an extended period of phosphatization.This exposure led to a depletion of key metallogenic elements,such as Co,Ni and Cu,within the Fe-Mn crusts,while P2O5 and CaO levels increased significantly.Since the Middle Miocene,the crusts have been progressively buried by pelagic sediments.
基金the National Natural Science Foundation of China(NSFC No.32360309)。
文摘Bauxite mining will bring huge economic benefit,but it also faces the risk of environmental pollution.Metal pollution problem has been widely concerned in bauxite tailing areas.Biodiversity indices,metal concentrations of moss crusts,and soil contamination indices in Wachangping bauxite tailing areas in Guizhou Province,China were measured and analyzed.In a total of 40 species belonging to 19 genera and 12 families of moss in the study areas,Ditrichum flexicaule(Schwaegr.)Hamp.(DF),Oxystegus cylindricus(Brid.)Hilp.(OC),and Ditrichum brevidens Nog.(DB)are the dominant moss crusts.Moss species diversity in different habitats has a certain regularity:waste residues area<waste rocks area<ore stockpile area<slope shrub area<shrub area by gutter<slope shrub herbaceous area.Sorenson diversity index(β)of moss species is influenced by microenvironment and substrate.Concentrations of Al,Mg,Ca,Fe,K,and Ti are the largest in DB(2,990 to 73,210 mg kg^(-1)),followed by those in DF(2,900 to 61,890 mg kg^(-1)),and are the smallest in OC(690 to 32,240 mg kg^(-1)),which show that the three moss crusts have different bioaccumulation capacities.Metal contents in underlying soils of moss crusts are higher than the background levels.Bioaccumulation factor(BAF)of Al,Mg,Ca,Fe,and K in three moss crusts are decreased in the following order:DB>DF>OC.Single factor pollution index(Ps)and Nemero comprehensive pollution index(Pc)of six metal are much greater than 3,and the index of geoaccumulation(Igeo)(1geo<5)reveals that the soil environment is at moderately to seriously contaminated levels.Principal components analysis(PCA)shows that there is no significant correlation between p H value,and metal contents(Al,Mg,Fe,K and Ti),soil temperature(ST)and metal contents(Al,Mg,Fe,K and Ti).Soil humidity(SH)is negatively correlated with metal contents(Al,Mg,Fe,K and Ti).These three environmental factors have little effect on the distribution of metal.Result also reflects that DB moss is readily able to both tolerate and accumulate metal,which makes it a suitable bioindicator of multiple metal contamination in Wachangping bauxite tailing areas.
基金supported by the Natural Science Foundation of Gansu Province,China(24JRRA733,23JRRA589)the National Natural Science Foundation of China(42377470,42207539)the Light of Western Light Program of Talent Cultivation of Chinese Academy of Sciences(22JR9KA028).
文摘Biological soil crusts(BSCs)play crucial roles in improving soil fertility and promoting plants settlement and reproduction in arid areas.However,the specific effects of BSCs on growth status and nutrient accumulation of plants are still unclear in different arid areas.This study analyzed the effects of three different BSCs treatments(without crust(WC),intact crust(IC),and broken crust(BC))on the growth,inorganic nutrient absorption,and organic solute synthesis of three typical desert plants(Grubovia dasyphylla(Fisch.&C.A.Mey.)Freitag&G.Kadereit,Nitraria tangutorum Bobrov,and Caragana koraiensis Kom.)in the Minqin desert-oasis ecotone of Northwest China.Results showed that the effects of three BSCs treatments on seed emergence and survival of three plants varied with seed types.The IC treatment significantly hindered the emergence and survival of seeds,while the BC treatment was more conducive to seed emergence and survival of plants.BSCs significantly promoted the growth of three plants,but their effects on plant growth varied at different stages of the growth.Briefly,the growth of G.dasyphylla was affected by BSCs in early stage,but the effects on the growth of G.dasyphylla significantly weakened in the middle and late stages.However,the growth of N.tangutorum and C.koraiensis only showed differences at the middle and late stages,with a significant enhancement in growth.Analysis of variance showed that BSCs,plant species,growth period,and their interactions had significant effects on the biomass and root:shoot ratio of three plants.BSC significantly affected the nutrients absorption and organic solute synthesis in plants.Specifically,BSCs significantly promoted nitrogen(N)absorption in plants and increased plant adaptability in N poor desert ecosystems,but had no significant effects on phosphorus(P)absorption.The effects of BSCs on inorganic nutrient absorption and organic solute synthesis in plants varied significantly among different plant species.The results suggest that BSCs have significant effects on the growth and nutrient accumulation of desert plants,which will provide theoretical basis for exploring the effects of BSCs on desert plant diversity,biodiversity conservation,and ecosystem management measures in arid and semi-arid areas.
基金supported by the Science and Technology Research Program of Chongqing Municipal Education Commission(Grant No.KJQN202404310,KJQN202304302)National Natural Science Foundation of China(41972118).
文摘The Yarlung Zangbo Suture Zone(YZSZ)on the southern margin of the Lhasa block and the Tangjia-Sumdo ultrahigh-pressure metamorphic belt(TSMB)within the block represent natural laboratories for the study of plate tectonics and oceanic slab subduction.It is generally believed that these two zones represent the remnants of the ancient oceanic crust and upper mantle of the Yarlung Zangbo Neo-Tethys(YZNT)and the Tangjia-Sumdo Paleo-Tethys(TSPT).However,the evolutionary patterns and spatiotemporal relationships of the TSPT and the YZNT have been debated.
基金Project supported by the Major Research Plan of the National Natural Science Foundation of China(91962211)the National Key Research and Development Program of China(2021YFC2902202)+2 种基金the Science and Technology Innovation Fund of GRINM(2022PD0102)the Major Program of Qingyuan Innovation Laboratory(00122004)the Beijing Nova Program(20230484379)。
文摘In this paper,a multi-stage leaching process for the weathered crust elution-deposited rare earth ore was proposed using MgSO_(4)as a leaching agent.The results indicate that with increasing the concentration of MgSO_(4)from 0.5 wt%-1.0 wt%to 2.0 wt%-4.0 wt%,the peak concentrations of rare earths increase from 1.87 to 3.59 to 5.49-10.21 g/L,and the collection periods of leach solution are sho rtened from 0.85 to 1.54 to 0.31-0.47(liquid-to-ore ratio).When the rare earth ore is leached with leaching agent solution with high initial pH(3.0-5.0),the rare earths and aluminum are predominantly leached by Mg^(2+)instead of H+.However,H+participate in the leaching process of rare earths and aluminum at lower initial pH(1.5-3.0)of the leaching agent solution.Especially,when the initial pH of leaching agent solution is 2.0,a large amount of aluminum is leached when the liquid-to-ore ratio is greater than 1.2.Based on the above insights,increasing the initial pH(3.0-5.0)of leaching agent solution in the injection stage using high-concentration MgSO_(4)(>1.0 wt%)can increase the peak concentration of rare earths in the leach solution and shorten the collection period.However,in the injection stage using low MgSO_(4)concentration(<1.0 wt%),an initial pH of leaching agent solution of 2.0 is selected to reduce the leaching amount of aluminum and the consumption of MgSO_(4).Comparing to the Leaching process using constant MgSO_(4)concentration(2.0 wt%,initial pH of 5.0),the leaching efficiency of rare earths using a multi-stage leaching process is approximately equal(about 94.6%)under optimal conditions.The leaching amount of aluminum is reduced by 16.9%.The consumption of MgSO_(4)is reduced by 67.1%.
基金Project supported by the National Natural Science Foundation of China(U2002215)。
文摘Weathered crust elution-deposited rare earth ores(WREOs)are rich in medium and heavy rare earth.In order to improve the in-situ leaching process,which is prone to landslides and poor permeability,cationic hydroxyethyl cellulose(PQ-10)was used as a novel green swelling inhibitor and percolation promoter and was mixed with conventional leaching agent ammonium sulfate((NH_(4))_(2)SO_(4))to form a composite leaching agent to study the performance and mechanism of swelling inhibition and percolation promotion.Adding PQ-10 can inhibit the hydration swelling of WREOs,promote the percolation effect of the leaching agent,improve the rare earth(RE)leaching efficiency,and reduce the im purity aluminum(Al)leaching efficiency.Compared with the conventional leaching agent 2 wt%(NH_(4))_(2)SO_(4),the percolation time is reduced by 50%by using the composite leaching agent(0.02 wt%PQ-10+2 wt%(NH_(4))_(2)SO_(4)).PQ-10 has positively charged quaternary ammonium groups and hydrophilic group hydroxyl groups,which makes it easy to adsorb on WREOs multiple sites through electrostatic interaction and hydrogen bonding,weakening the electrostatic repulsion between mineral particles,reducing the WREOs interlayer spacing,compressing the double electric layer thickness at the solid-liquid interface,weakening the mineral hydration swelling and increasing the percolation rate.The long carbon chains of the polymer entangle and link the fine mineral particles to agglomerate them,increasing their particle size and reduc ing their hydration dispersion,and preventing blockage of the pe rcolation pores caused by migration of the fine particles through the ore body with the solution.PQ-10 molecules also insert the mine ral interlayer and expulsion of the internal water,further inhibiting the swelling of WREOs.Adding PQ-10 reduces the surface tension of(NH_(4))_(2)SO_(4)solution,improving the spreading and spreading ability of the solution,reducing the adhesion work between molecules in the solid-liquid phase and the adhesion work reduction factor.It proves that PQ-10 promotes the percolation effect of the leaching process of WREOs.In addition,PQ-10 expands the leaching pore size and seepage channels,further improving the percolation rate.
基金funded by the National Key R&D Program of China (Grant No. 2021YFC3000704)the National Natural Science Foundation of China (Grant No. 42125401)the Central Public-interest Scientific Institution Basal Research Fund (Grant No. CEAIEF20240401)。
文摘The Anninghe–Zemuhe Fault and the Xiaojiang Fault are critical active faults along the middle-eastern boundary of the South Chuan–Dian Block. Many researchers have identified these faults as potential strong-earthquake risk zones. In this study, we leveraged a dense seismic array to investigate the high-resolution shallow crust shear wave velocity(Vs) structure beneath the junction of the Zemuhe Fault Zone and the Xiaojiang Fault Zone, one of the most complex parts of the eastern boundary of the South Chuan–Dian Block. We analyzed the distribution of microseismic events detected between November 2022 and February 2023 based on the fine-scale Vs model obtained. The microseismicity in the study region was clustered into three groups, all spatially related to major faults in this region. These microseismic events indicate near-vertical fault planes, consistent with the fault geometry revealed by other researchers.Moreover, these microseismic events are influenced by the impoundment of the downstream Baihetan Reservoir and the complex tectonic stress near the junction of the Zemuhe Fault Zone and the Xiaojiang Fault Zone. The depths of these microseismic events are shallower in the junction zone, whereas moving south along the Xiaojiang Fault Zone, the microseismic events become deeper.Additionally, we compared our fine-scale local Vs model with velocity models obtained by other researchers and found that our model offers greater detail in characterizing subsurface heterogeneity while demonstrating improved reliability in delineating fault systems.
基金supported by PRIN 2020 project(Resp.Michele Marroni)Claudia D’Oriano(INGV)Matteo Masotta and Danis Filimon(Earth Science Dept)are also thanked for analytical support in the laboratoriesThis work benefited from the PRA 2022 project handled by Francesca Meneghini.
文摘The Middle to Late Jurassic,high-pressure metamorphic ophiolites of Inzecca Unit are well exposed in the Noceta-Vezzani area of Alpine Corsica.These metaophiolites were studied by using a multidisciplinary approach to reconstruct the architecture of the oceanic sector from which they derived.The collected data indicate that this oceanic crust consists of a mantle metaperidotites and metaophicalcites,both covered by massive or pillow metabasalts with or without a layer of ophiolite-bearing metabreccias.
