In cold regions,rock structures will be weakened by freeze-thaw cycles under various water immersion conditions.Determining how water immersion conditions impact rock deterioration under freeze-thaw cycles is critical...In cold regions,rock structures will be weakened by freeze-thaw cycles under various water immersion conditions.Determining how water immersion conditions impact rock deterioration under freeze-thaw cycles is critical to assess accurately the frost resistance of engineered rock.In this paper,freeze-thaw cycles(temperature range of-20℃-20℃)were performed on the sandstones in different water immersion conditions(fully,partially and non-immersed in water).Then,computed tomography(CT)tests were conducted on the sandstones when the freeze-thaw number reached 0,5,10,15,20 and 30.Next,the effects of water immersion conditions on the microstructure deterioration of sandstone under freezethaw cycles were evaluated using CT spatial imaging,porosity and damage factor.Finally,focusing on the partially immersed condition,the immersion volume rate was defined to understand the effects of immersion degree on the freeze-thaw damage of sandstone and to propose a damage model considering the freeze-thaw number and immersion degree.The results show that with increasing freeze-thaw number,the porosities and damage factors under fully and partially immersed conditions increase continuously,while those under non-immersed condition first increase and then remain approximately constant.The most severe freeze-thaw damage occurs in fully immersed condition,followed by partially immersed condition and finally non-immersed condition.Interestingly,the freeze-thaw number and the immersion volume rate both impact the microstructure deterioration of the partially immersed sandstone.For the same freeze-thaw number,the damage factor increases approximately linearly with increasing immersion volume rate,and the increasing immersion degree exacerbates the microstructure deterioration of sandstone.Moreover,the proposed model can effectively estimate the freeze-thaw damage of partially immersed sandstone with different immersion volume rates.展开更多
Nebkhas,which play a fundamental role in stabilizing ecosystems in arid and semi-arid regions,are currently threatened by global warming and anthropogenic activities.This study focuses on a tamarisk-nebkha profile sit...Nebkhas,which play a fundamental role in stabilizing ecosystems in arid and semi-arid regions,are currently threatened by global warming and anthropogenic activities.This study focuses on a tamarisk-nebkha profile situated in the lower reaches of the Shule River Basin,an arid region in northwestern China.Using radioactive dating and the physicochemical properties of sediments,this study reconstructed changes in the nebkha’s hydro-ecological conditions over the past decades.The results revealed a significant decline in fine particle fraction,carbonate content,and low-frequency magnetic susceptibility,along with a notable increase in the Si_(2)O_(3)/Al_(2)O_(3) ratio,since the 1990s.These findings indicate the intensification of the desertification process and the degradation of hydrological conditions within the nebkha.Primary factors contributing to these transformations include the steadily rising temperature,which leads to an increased evaporation rate,and a substantial rise in human water consumption.These indicate an elevated risk of future nebkha reactivation.This reactivation,in turn,could potentially accelerate the process of regional desertification and lead to an ecological crisis.展开更多
This paper is based on the rainwater collection project in the retrofit of the Dongyi teaching block in Zhejiang University Xixi Campus.The analysis incorporates the local meteorological data, recycling water utilizat...This paper is based on the rainwater collection project in the retrofit of the Dongyi teaching block in Zhejiang University Xixi Campus.The analysis incorporates the local meteorological data, recycling water utilization, and precipitation adjustment.The rainwater collection system in this program also adds the condensation water from the heating, ventilation and air conditioning （ HVAC） system and the concentration from the reverse-osmosis system used for watering greens and supplying waterscapes.By calculating, the quantity of the HVAC condensation water in summer is 3.48 m3/d, and the quantity of the reverse-osmosis concentrated water is 198 to 396 L/d.This method solves the water shortage caused by high evaporation in summer and low precipitation in winter.Supported by empirical monitoring data, the proposed method significantly increases the economic efficiency of the system during the summer period.展开更多
Leaf wetness provides a wide range of benefits not only to leaves,but also to ecosystems and communities.It regulates canopy eco-hydrological processes and drives spatial differences in hydrological flux.In spite of t...Leaf wetness provides a wide range of benefits not only to leaves,but also to ecosystems and communities.It regulates canopy eco-hydrological processes and drives spatial differences in hydrological flux.In spite of these functions,little remains known about the spatial distribution of leaf wetness under different soil water conditions.Leaf wetness measurements at the top(180 cm),middle(135 cm),and bottom(85 cm)of the canopy positions of rainfed jujube(Ziziphus jujuba Mill.)in the Chinese loess hilly region were obtained along with meteorological and soil water conditions during the growing seasons in 2019 and 2020.Under soil water non-deficit condition,the frequency of occurrence of leaf wetness was 5.45%higher at the top than at the middle and bottom of the canopy positions.The frequency of occurrence of leaf wetness at the top,middle and bottom of the canopy positions was over 80%at 17:00‒18:00(LST).However,the occurrence of leaf wetness at the top was earlier than those at the middle and bottom of the canopy positions.Correspondingly,leaf drying at the top was also latter than those at the middle and bottom of the canopy positions.Leaf wetness duration at the middle was similar to that at the bottom of the canopy position,but about 1.46-3.01 h less than that at the top.Under soil water deficit condition,the frequency of occurrence of leaf wetness(4.92%-45.45%)followed the order of top>middle>bottom of the canopy position.As the onset of leaf wetness was delayed,the onset of wet leaf drying was advanced and the leaf wetness duration was shortened.Leaf wetness duration at the top was linearly related(R^(2)>0.70)to those at the middle and bottom of the canopy positions under different soil water conditions.In conclusion,the hydrological processes at canopy surfaces of rainfed jujube depended on the position of leaves,thus adjusting canopy structure to redistribute hydrological process is a way to meet the water need of jujube.展开更多
The changes in soil organic carbon(C) mineralization as affected by anthropogenic disturbance directly determine the role of soils as C source or sink in the global C budget. The objectives of this study were to inves...The changes in soil organic carbon(C) mineralization as affected by anthropogenic disturbance directly determine the role of soils as C source or sink in the global C budget. The objectives of this study were to investigate the effects of anthropogenic disturbance(aquaculture pond, pollutant discharge and agricultural activity) on soil organic C mineralization under different water conditions in the Minjiang River estuary wetland, Southeast China. The results showed that the organic C mineralization in the wetland soils was significantly affected by human disturbance and water conditions(P < 0.001), and the interaction between human disturbance activities and water conditions was also significant(P < 0.01). The C mineralization rate and the cumulative mineralized carbon dioxide-carbon(CO_2-C)(at the 49th day) ranked from highest to lowest as follows: Phragmites australis wetland soil > aquaculture pond sediment > soil near the discharge outlet > rice paddy soil. This indicated that human disturbance inhibited the mineralization of C in soils of the Minjiang River estuary wetland, and the inhibition increased with the intensity of human disturbance. The data for cumulative mineralized CO_2-C showed a good fit(R^2 > 0.91) to the first-order kinetic model C_t = C_0(1 – exp(–kt)). The kinetic parameters C_0, k and C_0 k were significantly affected by human disturbance and water conditions. In addition, the total amount of mineralized C(in 49 d) was positively related to C_0, C_0 k and electrical conductivity of soils. These findings indicated that anthropogenic disturbance suppressed the organic C mineralization potential in subtropical coastal wetland soils, and changes of water pattern as affected by human activities in the future would have a strong influence on C cycling in the subtropical estuarine wetlands.展开更多
The operation of cascade reservoirs in a watershed profoundly exerts river watersediment dynamics and topography evolution,and the terminal reservoir is the focus area for river and waterway management.This paper reve...The operation of cascade reservoirs in a watershed profoundly exerts river watersediment dynamics and topography evolution,and the terminal reservoir is the focus area for river and waterway management.This paper reveals the process and underlying factors of topography evolution and water level adjustment in the lower Hanjiang River under the action of cascade reservoirs.This study focused on the 263 km river channel downstream of the Xinglong Hydropower Conservancy Project on the Hanjiang River.Using measured flow,sediment,and topography data from 1977 to 2023,we analyzed the changing characteristics of riverbed scouring and deposition intensity,thalweg,and cross-sections.Additionally,we evaluated the response relationship between riverbed scouring and deposition intensity and factors such as sediment transport,runoff,and human activities.From 1977 to 2023,the low-water channel in the Xinglong-Estuary reaches showed a scouring and cutting tendency,and the riverbed slop initially decreased and then increased.The main cause of the riverbed scouring along the Xinglong-Estuary reaches was the reduced sediment load in the watershed,with waterway engineering having a slightly larger influence than runoff in the Xinglong-Xiantao reaches;by contrast,runoff exerted a more significant effect than both waterway engineering and the Yangtze River water level decline in the Xiantao-Estuary reaches.During the autumn flood season from 1983 to 2023,the water level differences between the Hanjiang and Yangtze Rivers at the same flow rate showed an increasing trend,leading to an increase in water surface slope,which intensified scouring forces and riverbed scouring.This study improves our understanding of the impacts of dam construction on river topographical evolution,water level changes,and deep‐water waterway resources.展开更多
Natural water bodies often contain a significant amount of suspended colloidal particles,which not only reduce water transparency but also have a high adsorption capacity for soluble pollutants.These composite polluta...Natural water bodies often contain a significant amount of suspended colloidal particles,which not only reduce water transparency but also have a high adsorption capacity for soluble pollutants.These composite pollutants can migrate rapidly with water flow,which are usually difficult to degrade and remove by traditional methods.Aiming at suspended contaminated waterbodies,this study introduced a multilevel loading method to prepare carbon nanotube/sulfur doped carbon nitride(CNT/SCN)composite photocatalytic purification beads.The surface of the obtained core-shell structured purification beads is loaded with CNT/SCN photocatalysts which exhibit three-dimensional conductive and porous characteristics.TC–HCl was introduced as the target pollutant,and the removal efficiency of the composite purification beads under different water turbidity and hydrodynamic conditions were investigated.The results showed that during 15 h of degradation process,at the depth of 20 cm,with the flow rate of 0.015 m^(3)/h and water turbidity of 10.3 NTU,the purification beads achieved a removal efficiency of 54.9%for tetracycline hydrochloride(TC–HCl),which was 2.03 times higher than that of SCN purification beads.The three-dimensional porous structure of the surface exhibited excellent adsorption and trapping capabilities for suspended colloidal particles.The introduction of carbon nanotubes enhanced charge transfer ability of the surface layer and reduces the local charge accumulation effect caused by surface adsorption,which effectively enhances the adsorption of suspended colloid,and also significantly improved the degradation efficiency of TC–HCl.This study provides a valuable insight for the engineering application of photocatalytic technology.展开更多
In order to study the mechanism of confined water inrush from coal seam floor,the main influences on permeability in the process of triaxial seepage experiments were analyzed with methods such as laboratory experiment...In order to study the mechanism of confined water inrush from coal seam floor,the main influences on permeability in the process of triaxial seepage experiments were analyzed with methods such as laboratory experiments,theoretical analysis and mechanical model calculation.The crack extension rule and the ultimate destruction form of the rock specimens were obtained.The mechanism of water inrush was explained reasonably from mechanical point of view.The practical criterion of water inrush was put forward.The results show that the rock permeability "mutation" phenomenon reflects the differences of stress state and cracks extension rate when the rock internal crack begins to extend in large-scale.The rock ultimate destruction form is related to the rock lithology and the angle between crack and principal stress.The necessary condition of floor water inrush is that the mining pressure leads to the extension and transfixion of the crack.The sufficient condition of floor water inrush is that the confined water’s expansionary stress in normal direction and shear stress in tangential direction must be larger than the internal stress in the crack.With the two conditions satisfied at the same time,the floor water inrush accident will occur.展开更多
Based on the measured discharge,sediment load,and cross-sectional data from 1986 to 2015 for the lower Yellow River,changes in the morphological parameters(width,depth,and cross-sectional geomorphic coefficient)of the...Based on the measured discharge,sediment load,and cross-sectional data from 1986 to 2015 for the lower Yellow River,changes in the morphological parameters(width,depth,and cross-sectional geomorphic coefficient)of the main channel are analyzed in this paper.The results show that before the operation of the Xiaolangdi Reservoir(XLDR)from 1986 to 1999,the main channel shrunk continually,with decreasing width and depth.The rate of reduction in its width decreased along the river whereas that of depth increased in the downstream direction.Because the rate of decrease in the width of the main channel was greater than that in channel depth,the cross-sectional geomorphic coefficient decreased in the sub-reach above Gaocun.By contrast,for the sub-reach below Gaocun,the rate of decrease in channel width was smaller than that in channel depth,and the cross-sectional geomorphic coefficient increased.Once the XLDR had begun operation,the main channel eroded continually,and both its width and depth increased from 2000 to 2015.The rate of increase in channel width decreased in the longitudinal direction,and the depth of the main channel in all sub-reaches increased by more than 2 m.Because the rate of increase in the depth of the main channel was clearly larger than that of its width,the cross-sectional geomorphic coefficient decreased in all sub-reaches.The cross-sectional geometry of the main-channel of the lower Yellow River exhibited different adjustment patterns before and after the XLDR began operation.Before its operation,the main channel mainly narrowed in the transverse direction and silted in the vertical direction in the sub-reach above Aishan;in the sub-reach below Aishan,it primarily silted in the vertical direction.After the XLDR began operation,the main channel adjusted by widening in the transverse direction and deepening in the vertical direction in the sub-reach above Aishan;in the sub-reach below it,the main channel adjusted mainly by deepening in the vertical direction.Compared with the rates of decrease in the width and depth of the main channel during the siltation period,the rate of increase in channel width during the scouring period was clearly smaller while the rate of increase in channel depth was larger.After continual siltation and scouring from 1986 to 2015,the cross-sectional geometry of the main-channel changed from wide and shallow to relatively narrow and deep.The pattern of adjustment in the main channel was closely related to the water and sediment conditions.For the braided reach,the cross-sectional geomorphic coefficient was negatively correlated with discharge and positively correlated with suspended sediment concentration(SSC)during the siltation period.By contrast,the cross-sectional geomorphic coefficient was positively correlated with discharge and negatively correlated with SSC during the scouring period.For the transitional and meandering reaches,the cross-sectional geomorphic coefficient was negatively correlated with discharge and positively correlated with SSC.展开更多
Greenhouse gas（GHG） emissions from oil and gas systems are an important component of the GHG emission inventory. To assess the carbon emissions from oilfield-produced water under atmospheric conditions correctly, in...Greenhouse gas（GHG） emissions from oil and gas systems are an important component of the GHG emission inventory. To assess the carbon emissions from oilfield-produced water under atmospheric conditions correctly, in situ detection and simulation experiments were developed to study the natural release of GHG into the atmosphere in the Shengli Oilfield,the second largest oilfield in China. The results showed that methane（CH4） and carbon dioxide（CO2） were the primary gases released naturally from the oilfield-produced water.The atmospheric temperature and release time played important roles in determining the CH4 and CO2emissions under atmospheric conditions. Higher temperatures enhanced the carbon emissions. The emissions of both CH4 and CO2from oilfield-produced water were highest at 27°C and lowest at 3°C. The bulk of CH4 and CO2was released from the oilfield-produced water during the first release period, 0–2 hr, for each temperature, with a maximum average emission rate of 0.415 g CH4/（m3·hr） and 3.934 g CO2/（m3·hr）, respectively. Then the carbon emissions at other time periods gradually decreased with the extension of time. The higher solubility of CO2 in water than CH4 results in a higher emission rate of CH4 than CO2over the same release duration. The simulation proved that oilfield-produced water is one of the potential emission sources that should be given great attention in oil and gas systems.展开更多
Sediment cores（containing sediment and overlying water） from Baihua Reservoir（SW China）were cultured under different redox conditions with different microbial activities, to understand the effects of sulfate-reduc...Sediment cores（containing sediment and overlying water） from Baihua Reservoir（SW China）were cultured under different redox conditions with different microbial activities, to understand the effects of sulfate-reducing bacteria（SRB） on mercury（Hg） methylation at sediment–water interfaces. Concentrations of dissolved methyl mercury（DMe Hg） in the overlying water of the control cores with bioactivity maintained（BAC） and cores with only sulfate-reducing bacteria inhibited（SRBI） and bacteria fully inhibited（BACI） were measured at the anaerobic stage followed by the aerobic stage. For the BAC and SRBI cores, DMe Hg concentrations in waters were much higher at the anaerobic stage than those at the aerobic stage, and they were negatively correlated to the dissolved oxygen concentrations（r =- 0.5311 and r =- 0.4977 for BAC and SRBI, respectively）. The water DMe Hg concentrations of the SRBI cores were 50% lower than those of the BAC cores, indicating that the SRB is of great importance in Hg methylation in sediment–water systems, but there should be other microbes such as iron-reducing bacteria and those containing specific gene cluster（hgc AB）, besides SRB,causing Hg methylation in the sediment–water system.展开更多
To explore the variation of permeability and deformation behaviors of a fractured rock mass in high water pressure,a high pressure permeability test（HPPT）,including measuring sensors of pore water pressure and displ...To explore the variation of permeability and deformation behaviors of a fractured rock mass in high water pressure,a high pressure permeability test（HPPT）,including measuring sensors of pore water pressure and displacement of the rock mass,was designed according to the hydrogeological condition of Heimifeng pumped storage power station.With the assumption of radial water flow pattern in the rock mass during the HPPT,a theoretical formula was presented to estimate the coefficient of permeability of the rock mass using water pressures in injection and measuring boreholes.The variation in permeability of the rock mass with the injected water pressure was studied according to the suggested formula.By fitting the relationship between the coefficient of permeability and the injected water pressure,a mathematical expression was obtained and used in the numerical simulations.For a better understanding of the relationship between the pore water pressure and the displacement of the rock mass,a 3D numerical method based on a coupled hydro-mechanical theory was employed to simulate the response of the rock mass during the test.By comparison of the calculated and measured data of pore water pressure and displacement,the deformation behaviors of the rock mass were analyzed.It is shown that the variation of displacement in the fractured rock mass is caused by water flow passing through it under high water pressure,and the rock deformation during the test could be calculated by using the coupled hydro-mechanical model.展开更多
The most important aspect of every civil engineering project is acquiring reliable information on the ground on which the project will be constructed. This research includes a site investigation, which is seen as a pr...The most important aspect of every civil engineering project is acquiring reliable information on the ground on which the project will be constructed. This research includes a site investigation, which is seen as a primary stage in gathering geological, geotechnical, and other essential engineering data for structures’ safe and cost-effective design. Five boreholes at well-spaced spots were drilled for subsurface investigation at a maximum depth of 15 m to 30 m. The standard penetration tests (SPT) were performed at different depths, soil samples were taken at various intervals, and lithological changes were observed. The friction angle was between 19.6ºand 33.03º, whereas the cohesion ranges between 0.25 kg/cm<sup>2</sup> and 0.42 kg/cm<sup>2</sup>, indicating a strong resistance to shearing and a high capacity to sustain the load. Furthermore, the soil samples’ maximum dry density ranges from 1.63 g/cm<sup>3</sup> to 1.80 g/cm<sup>3</sup>. In addition, water table depths were recorded from 6.0 m to 7.0 m. The net bearing capacity for isolated/pad foundation at a depth of 1.5 m to 2.5 m below the ground level has been calculated as 95.0 to 120.0 kPa and 120.0 to 180.0 kPa for raft foundation. The net allowable pressure settlement limits for isolated/pad and raft foundations are 25 mm (1-inch) and 50 mm (2-inches), respectively. The investigation has found no severe geological flaws on the proposed construction site, and therefore it is appropriate for the construction of an Air Separation Unit (ASU) Oxygen Plant.展开更多
Using NCEP 1° × 1° reanalysis data within 6 h, conventional observational data, data from regional automatic rainfall stations, satellite cloud pictures and Doppler radar data, we compared the physical ...Using NCEP 1° × 1° reanalysis data within 6 h, conventional observational data, data from regional automatic rainfall stations, satellite cloud pictures and Doppler radar data, we compared the physical conditions, dynamic and thermodynamic characteristics of two rainstorms in the southwest of Hunan Province on May 12 and June 15 in 2011. The results showed that the first process was triggered by strong cold air under unstable potential, while the second process was caused by shear line appearing from the east; during the first process, cold air divided into many parts and moved towards south, rainfall was uniform and lasted for a long time, while rainfall was relatively concentrated and strong, and lasted for a short time during the second process; the peak of K index appeared only during the second process; no sign of heavy rainfall was found from satellite cloud pictures and radar echo pictures during the first process, while obvious cloud cluster and echo ribbons could be found from satellite cloud pictures and radar echo pictures during the second process, which were the sign of heavy rainfall; slow movement of echo or little movement resulted in the second rainstorm, and constant echo intensity was the main reason for the occurrence of the second rainstorm. In addition, there was low-level southwest jet during the two processes, which provided favorable conditions for the transportation of water vapor and energy during the two processes. However, there was a great difference between the two rainstorms in the intensity and thickness of low-level jet, that is, the intensity and thickness of low-level jet during the first process were obviously weaker than these during the second process.展开更多
In the present paper,two-and three-dimensional velocity potentials generated by pulsating pressure distributions of infinite extent on the free surface of infinite-depth waters are strictly derived based on special ca...In the present paper,two-and three-dimensional velocity potentials generated by pulsating pressure distributions of infinite extent on the free surface of infinite-depth waters are strictly derived based on special cases of concentrated pulsating pressure.The far-field asymptotic behaviour of the potentials and the radiation conditions to be satisfied by them are discussed. It is proved in a general sense that the potentials should be composed of a forced wave component,a free wave component and a local disturbance component.The radiation condition of the forced wave component should correspond to the far-field asymptotic behaviour of the pressure distribution,Hence,the formulation of radiation conditions for the second-order diffraction potentials has theoretically become clear,The radiation conditions for two-and three-dimensional problems are explicitly given in the paper.展开更多
A Nomex fabric/phenolic composite was prepared,and its tribological properties were evaluated under dry and water‐bathed sliding conditions by a pin‐on‐disk tribometer.The resulting size of the friction coefficient...A Nomex fabric/phenolic composite was prepared,and its tribological properties were evaluated under dry and water‐bathed sliding conditions by a pin‐on‐disk tribometer.The resulting size of the friction coefficient for the Nomex fabric/phenolic composite in the study occurred in the following order:dry sliding condition>distilled water‐bathed sliding condition>sea water‐bathed sliding condition.The fabric composite’s wear rate from high to low was as follows:distilled water‐bathed sliding condition>sea water‐bathed sliding condition>dry sliding condition.Under water‐bathed sliding conditions,penetration of water into the cracks accelerated the composite’s invalidation process,resulting in a higher wear rate.We also found that the extent of corrosion and transfer film formed on the counterpart pin significantly influenced the wear rate of the Nomex fabric composite.Discussion of the Nomex fabric composite’s wear mechanisms under the sliding conditions investigated is provided on the basis of the characterization results.展开更多
Aims Biological soil crusts(BSCs)can affect soil properties including water dynamics and cycling of soil carbon and nitrogen in dryland ecosystems.Previous research has mostly focused on effects of BSCs on soil water ...Aims Biological soil crusts(BSCs)can affect soil properties including water dynamics and cycling of soil carbon and nitrogen in dryland ecosystems.Previous research has mostly focused on effects of BSCs on soil water distribution or carbon and nitrogen fixation in the surface soil layer.Thus,little is known about effects of BSCs on properties throughout the soil profile.In the current study,we assessed the effects of BSCs on the distribution of soil water content(SW),soil organic carbon content(SOC)and soil total nitrogen content(STN)throughout the soil profile as well as the influence of water conditions on the effects of BSCs.Methods In a field investigation in Mu Us Sandland,North China,soil samples were taken from plots with and without BSCs on 13 and 28 September 2006,respectively.On the two sampling dates,average soil gravimetric water content was 3.83%(61.29%)and 5.08%(60.89%),respectively,which were regarded as low and high water conditions.Soil samples were collected every 5 cm to a depth of 60 cm,and SW,SOC and STN were measured in the laboratory.Important Findings(i)BSCs affected profile distribution of SW,SOC and STN.In addition,water conditions within the plots significantly modified BSCs’effects on the profile distribution of SW,but marginally affected the effects on SOC and STN.(ii)Under high water conditions,SW in the surface soil layer(0–10 cm)was higher in soils with BSCs compared to those without BSCs,while the opposite was true in the deep soil layer(30–55 cm).(iii)Under low water conditions,SW was lower with BSCs compared with no BSCs in near-surface(5–20 cm)and deep(25–40 cm)soil layers.(iv)BSCs affected SOC and STN only in the surface soil layer(0–5 cm)and were modified by plot water conditions.展开更多
基金funding support from the National Natural Science Foundation of China(Grant No.12172019).
文摘In cold regions,rock structures will be weakened by freeze-thaw cycles under various water immersion conditions.Determining how water immersion conditions impact rock deterioration under freeze-thaw cycles is critical to assess accurately the frost resistance of engineered rock.In this paper,freeze-thaw cycles(temperature range of-20℃-20℃)were performed on the sandstones in different water immersion conditions(fully,partially and non-immersed in water).Then,computed tomography(CT)tests were conducted on the sandstones when the freeze-thaw number reached 0,5,10,15,20 and 30.Next,the effects of water immersion conditions on the microstructure deterioration of sandstone under freezethaw cycles were evaluated using CT spatial imaging,porosity and damage factor.Finally,focusing on the partially immersed condition,the immersion volume rate was defined to understand the effects of immersion degree on the freeze-thaw damage of sandstone and to propose a damage model considering the freeze-thaw number and immersion degree.The results show that with increasing freeze-thaw number,the porosities and damage factors under fully and partially immersed conditions increase continuously,while those under non-immersed condition first increase and then remain approximately constant.The most severe freeze-thaw damage occurs in fully immersed condition,followed by partially immersed condition and finally non-immersed condition.Interestingly,the freeze-thaw number and the immersion volume rate both impact the microstructure deterioration of the partially immersed sandstone.For the same freeze-thaw number,the damage factor increases approximately linearly with increasing immersion volume rate,and the increasing immersion degree exacerbates the microstructure deterioration of sandstone.Moreover,the proposed model can effectively estimate the freeze-thaw damage of partially immersed sandstone with different immersion volume rates.
基金National Natural Science Foundation of ChinaNo.41401005,No.42307555+3 种基金Chinese Academy of Geological Sciences Basal Research FundNo.JKYQN202418,No.YK202405Project of the China Geological SurveyNo.DD20230459。
文摘Nebkhas,which play a fundamental role in stabilizing ecosystems in arid and semi-arid regions,are currently threatened by global warming and anthropogenic activities.This study focuses on a tamarisk-nebkha profile situated in the lower reaches of the Shule River Basin,an arid region in northwestern China.Using radioactive dating and the physicochemical properties of sediments,this study reconstructed changes in the nebkha’s hydro-ecological conditions over the past decades.The results revealed a significant decline in fine particle fraction,carbonate content,and low-frequency magnetic susceptibility,along with a notable increase in the Si_(2)O_(3)/Al_(2)O_(3) ratio,since the 1990s.These findings indicate the intensification of the desertification process and the degradation of hydrological conditions within the nebkha.Primary factors contributing to these transformations include the steadily rising temperature,which leads to an increased evaporation rate,and a substantial rise in human water consumption.These indicate an elevated risk of future nebkha reactivation.This reactivation,in turn,could potentially accelerate the process of regional desertification and lead to an ecological crisis.
文摘This paper is based on the rainwater collection project in the retrofit of the Dongyi teaching block in Zhejiang University Xixi Campus.The analysis incorporates the local meteorological data, recycling water utilization, and precipitation adjustment.The rainwater collection system in this program also adds the condensation water from the heating, ventilation and air conditioning （ HVAC） system and the concentration from the reverse-osmosis system used for watering greens and supplying waterscapes.By calculating, the quantity of the HVAC condensation water in summer is 3.48 m3/d, and the quantity of the reverse-osmosis concentrated water is 198 to 396 L/d.This method solves the water shortage caused by high evaporation in summer and low precipitation in winter.Supported by empirical monitoring data, the proposed method significantly increases the economic efficiency of the system during the summer period.
基金funded by the National Natural Science Foundation of China(32060301).
文摘Leaf wetness provides a wide range of benefits not only to leaves,but also to ecosystems and communities.It regulates canopy eco-hydrological processes and drives spatial differences in hydrological flux.In spite of these functions,little remains known about the spatial distribution of leaf wetness under different soil water conditions.Leaf wetness measurements at the top(180 cm),middle(135 cm),and bottom(85 cm)of the canopy positions of rainfed jujube(Ziziphus jujuba Mill.)in the Chinese loess hilly region were obtained along with meteorological and soil water conditions during the growing seasons in 2019 and 2020.Under soil water non-deficit condition,the frequency of occurrence of leaf wetness was 5.45%higher at the top than at the middle and bottom of the canopy positions.The frequency of occurrence of leaf wetness at the top,middle and bottom of the canopy positions was over 80%at 17:00‒18:00(LST).However,the occurrence of leaf wetness at the top was earlier than those at the middle and bottom of the canopy positions.Correspondingly,leaf drying at the top was also latter than those at the middle and bottom of the canopy positions.Leaf wetness duration at the middle was similar to that at the bottom of the canopy position,but about 1.46-3.01 h less than that at the top.Under soil water deficit condition,the frequency of occurrence of leaf wetness(4.92%-45.45%)followed the order of top>middle>bottom of the canopy position.As the onset of leaf wetness was delayed,the onset of wet leaf drying was advanced and the leaf wetness duration was shortened.Leaf wetness duration at the top was linearly related(R^(2)>0.70)to those at the middle and bottom of the canopy positions under different soil water conditions.In conclusion,the hydrological processes at canopy surfaces of rainfed jujube depended on the position of leaves,thus adjusting canopy structure to redistribute hydrological process is a way to meet the water need of jujube.
基金Under the auspices of National Basic Research Program of China(No.2012CB956100)National Natural Science Foundation of China(No.41301085)the Key Foundation of Science and Technology Department of Fujian Province(No.2016R1032-1)
文摘The changes in soil organic carbon(C) mineralization as affected by anthropogenic disturbance directly determine the role of soils as C source or sink in the global C budget. The objectives of this study were to investigate the effects of anthropogenic disturbance(aquaculture pond, pollutant discharge and agricultural activity) on soil organic C mineralization under different water conditions in the Minjiang River estuary wetland, Southeast China. The results showed that the organic C mineralization in the wetland soils was significantly affected by human disturbance and water conditions(P < 0.001), and the interaction between human disturbance activities and water conditions was also significant(P < 0.01). The C mineralization rate and the cumulative mineralized carbon dioxide-carbon(CO_2-C)(at the 49th day) ranked from highest to lowest as follows: Phragmites australis wetland soil > aquaculture pond sediment > soil near the discharge outlet > rice paddy soil. This indicated that human disturbance inhibited the mineralization of C in soils of the Minjiang River estuary wetland, and the inhibition increased with the intensity of human disturbance. The data for cumulative mineralized CO_2-C showed a good fit(R^2 > 0.91) to the first-order kinetic model C_t = C_0(1 – exp(–kt)). The kinetic parameters C_0, k and C_0 k were significantly affected by human disturbance and water conditions. In addition, the total amount of mineralized C(in 49 d) was positively related to C_0, C_0 k and electrical conductivity of soils. These findings indicated that anthropogenic disturbance suppressed the organic C mineralization potential in subtropical coastal wetland soils, and changes of water pattern as affected by human activities in the future would have a strong influence on C cycling in the subtropical estuarine wetlands.
基金National Natural Science Foundation of China,Grant/Award Numbers:52279066,U2340217Fundamental Research Funds for Central Welfare Research Institutes,Grant/Award Number:TKS20240402National Key Research and Development Program of China,Grant/Award Number:2023YFC3209500。
文摘The operation of cascade reservoirs in a watershed profoundly exerts river watersediment dynamics and topography evolution,and the terminal reservoir is the focus area for river and waterway management.This paper reveals the process and underlying factors of topography evolution and water level adjustment in the lower Hanjiang River under the action of cascade reservoirs.This study focused on the 263 km river channel downstream of the Xinglong Hydropower Conservancy Project on the Hanjiang River.Using measured flow,sediment,and topography data from 1977 to 2023,we analyzed the changing characteristics of riverbed scouring and deposition intensity,thalweg,and cross-sections.Additionally,we evaluated the response relationship between riverbed scouring and deposition intensity and factors such as sediment transport,runoff,and human activities.From 1977 to 2023,the low-water channel in the Xinglong-Estuary reaches showed a scouring and cutting tendency,and the riverbed slop initially decreased and then increased.The main cause of the riverbed scouring along the Xinglong-Estuary reaches was the reduced sediment load in the watershed,with waterway engineering having a slightly larger influence than runoff in the Xinglong-Xiantao reaches;by contrast,runoff exerted a more significant effect than both waterway engineering and the Yangtze River water level decline in the Xiantao-Estuary reaches.During the autumn flood season from 1983 to 2023,the water level differences between the Hanjiang and Yangtze Rivers at the same flow rate showed an increasing trend,leading to an increase in water surface slope,which intensified scouring forces and riverbed scouring.This study improves our understanding of the impacts of dam construction on river topographical evolution,water level changes,and deep‐water waterway resources.
基金supported by the Key Programof National Nat-ural Science Foundation of China(No.92047201)the National Natural Science Foundation of China(No.92047303)the Na-tional Science Funds for Creative Research Groups of China(No.51421006).
文摘Natural water bodies often contain a significant amount of suspended colloidal particles,which not only reduce water transparency but also have a high adsorption capacity for soluble pollutants.These composite pollutants can migrate rapidly with water flow,which are usually difficult to degrade and remove by traditional methods.Aiming at suspended contaminated waterbodies,this study introduced a multilevel loading method to prepare carbon nanotube/sulfur doped carbon nitride(CNT/SCN)composite photocatalytic purification beads.The surface of the obtained core-shell structured purification beads is loaded with CNT/SCN photocatalysts which exhibit three-dimensional conductive and porous characteristics.TC–HCl was introduced as the target pollutant,and the removal efficiency of the composite purification beads under different water turbidity and hydrodynamic conditions were investigated.The results showed that during 15 h of degradation process,at the depth of 20 cm,with the flow rate of 0.015 m^(3)/h and water turbidity of 10.3 NTU,the purification beads achieved a removal efficiency of 54.9%for tetracycline hydrochloride(TC–HCl),which was 2.03 times higher than that of SCN purification beads.The three-dimensional porous structure of the surface exhibited excellent adsorption and trapping capabilities for suspended colloidal particles.The introduction of carbon nanotubes enhanced charge transfer ability of the surface layer and reduces the local charge accumulation effect caused by surface adsorption,which effectively enhances the adsorption of suspended colloid,and also significantly improved the degradation efficiency of TC–HCl.This study provides a valuable insight for the engineering application of photocatalytic technology.
基金supported by the Youth Innovation Fund of China(KJ-2013-TDKC-15)the Fostering and Doctor Startup Initial Fund Program of Xi’an University of Science and Technology(201350,2014QDJ033).
文摘In order to study the mechanism of confined water inrush from coal seam floor,the main influences on permeability in the process of triaxial seepage experiments were analyzed with methods such as laboratory experiments,theoretical analysis and mechanical model calculation.The crack extension rule and the ultimate destruction form of the rock specimens were obtained.The mechanism of water inrush was explained reasonably from mechanical point of view.The practical criterion of water inrush was put forward.The results show that the rock permeability "mutation" phenomenon reflects the differences of stress state and cracks extension rate when the rock internal crack begins to extend in large-scale.The rock ultimate destruction form is related to the rock lithology and the angle between crack and principal stress.The necessary condition of floor water inrush is that the mining pressure leads to the extension and transfixion of the crack.The sufficient condition of floor water inrush is that the confined water’s expansionary stress in normal direction and shear stress in tangential direction must be larger than the internal stress in the crack.With the two conditions satisfied at the same time,the floor water inrush accident will occur.
基金Key Program of National Natural Science Foundation of China,No.51639005National Key R&D Program of China,No.2017YFC0405202,No.2016YFC0402406。
文摘Based on the measured discharge,sediment load,and cross-sectional data from 1986 to 2015 for the lower Yellow River,changes in the morphological parameters(width,depth,and cross-sectional geomorphic coefficient)of the main channel are analyzed in this paper.The results show that before the operation of the Xiaolangdi Reservoir(XLDR)from 1986 to 1999,the main channel shrunk continually,with decreasing width and depth.The rate of reduction in its width decreased along the river whereas that of depth increased in the downstream direction.Because the rate of decrease in the width of the main channel was greater than that in channel depth,the cross-sectional geomorphic coefficient decreased in the sub-reach above Gaocun.By contrast,for the sub-reach below Gaocun,the rate of decrease in channel width was smaller than that in channel depth,and the cross-sectional geomorphic coefficient increased.Once the XLDR had begun operation,the main channel eroded continually,and both its width and depth increased from 2000 to 2015.The rate of increase in channel width decreased in the longitudinal direction,and the depth of the main channel in all sub-reaches increased by more than 2 m.Because the rate of increase in the depth of the main channel was clearly larger than that of its width,the cross-sectional geomorphic coefficient decreased in all sub-reaches.The cross-sectional geometry of the main-channel of the lower Yellow River exhibited different adjustment patterns before and after the XLDR began operation.Before its operation,the main channel mainly narrowed in the transverse direction and silted in the vertical direction in the sub-reach above Aishan;in the sub-reach below Aishan,it primarily silted in the vertical direction.After the XLDR began operation,the main channel adjusted by widening in the transverse direction and deepening in the vertical direction in the sub-reach above Aishan;in the sub-reach below it,the main channel adjusted mainly by deepening in the vertical direction.Compared with the rates of decrease in the width and depth of the main channel during the siltation period,the rate of increase in channel width during the scouring period was clearly smaller while the rate of increase in channel depth was larger.After continual siltation and scouring from 1986 to 2015,the cross-sectional geometry of the main-channel changed from wide and shallow to relatively narrow and deep.The pattern of adjustment in the main channel was closely related to the water and sediment conditions.For the braided reach,the cross-sectional geomorphic coefficient was negatively correlated with discharge and positively correlated with suspended sediment concentration(SSC)during the siltation period.By contrast,the cross-sectional geomorphic coefficient was positively correlated with discharge and negatively correlated with SSC during the scouring period.For the transitional and meandering reaches,the cross-sectional geomorphic coefficient was negatively correlated with discharge and positively correlated with SSC.
基金supported by the Strategic Priority Research Program-Climate Change:Carbon Budget and Relevant Issues of the Chinese Academy of Sciences(No.XDA05030300)
文摘Greenhouse gas（GHG） emissions from oil and gas systems are an important component of the GHG emission inventory. To assess the carbon emissions from oilfield-produced water under atmospheric conditions correctly, in situ detection and simulation experiments were developed to study the natural release of GHG into the atmosphere in the Shengli Oilfield,the second largest oilfield in China. The results showed that methane（CH4） and carbon dioxide（CO2） were the primary gases released naturally from the oilfield-produced water.The atmospheric temperature and release time played important roles in determining the CH4 and CO2emissions under atmospheric conditions. Higher temperatures enhanced the carbon emissions. The emissions of both CH4 and CO2from oilfield-produced water were highest at 27°C and lowest at 3°C. The bulk of CH4 and CO2was released from the oilfield-produced water during the first release period, 0–2 hr, for each temperature, with a maximum average emission rate of 0.415 g CH4/（m3·hr） and 3.934 g CO2/（m3·hr）, respectively. Then the carbon emissions at other time periods gradually decreased with the extension of time. The higher solubility of CO2 in water than CH4 results in a higher emission rate of CH4 than CO2over the same release duration. The simulation proved that oilfield-produced water is one of the potential emission sources that should be given great attention in oil and gas systems.
基金supported by the National Natural Science Foundation of China(nos.41063006,41363007,and 41273099)the Science and Technology Fund of Guizhou Province(no.[2013]2296)
文摘Sediment cores（containing sediment and overlying water） from Baihua Reservoir（SW China）were cultured under different redox conditions with different microbial activities, to understand the effects of sulfate-reducing bacteria（SRB） on mercury（Hg） methylation at sediment–water interfaces. Concentrations of dissolved methyl mercury（DMe Hg） in the overlying water of the control cores with bioactivity maintained（BAC） and cores with only sulfate-reducing bacteria inhibited（SRBI） and bacteria fully inhibited（BACI） were measured at the anaerobic stage followed by the aerobic stage. For the BAC and SRBI cores, DMe Hg concentrations in waters were much higher at the anaerobic stage than those at the aerobic stage, and they were negatively correlated to the dissolved oxygen concentrations（r =- 0.5311 and r =- 0.4977 for BAC and SRBI, respectively）. The water DMe Hg concentrations of the SRBI cores were 50% lower than those of the BAC cores, indicating that the SRB is of great importance in Hg methylation in sediment–water systems, but there should be other microbes such as iron-reducing bacteria and those containing specific gene cluster（hgc AB）, besides SRB,causing Hg methylation in the sediment–water system.
文摘To explore the variation of permeability and deformation behaviors of a fractured rock mass in high water pressure,a high pressure permeability test（HPPT）,including measuring sensors of pore water pressure and displacement of the rock mass,was designed according to the hydrogeological condition of Heimifeng pumped storage power station.With the assumption of radial water flow pattern in the rock mass during the HPPT,a theoretical formula was presented to estimate the coefficient of permeability of the rock mass using water pressures in injection and measuring boreholes.The variation in permeability of the rock mass with the injected water pressure was studied according to the suggested formula.By fitting the relationship between the coefficient of permeability and the injected water pressure,a mathematical expression was obtained and used in the numerical simulations.For a better understanding of the relationship between the pore water pressure and the displacement of the rock mass,a 3D numerical method based on a coupled hydro-mechanical theory was employed to simulate the response of the rock mass during the test.By comparison of the calculated and measured data of pore water pressure and displacement,the deformation behaviors of the rock mass were analyzed.It is shown that the variation of displacement in the fractured rock mass is caused by water flow passing through it under high water pressure,and the rock deformation during the test could be calculated by using the coupled hydro-mechanical model.
文摘The most important aspect of every civil engineering project is acquiring reliable information on the ground on which the project will be constructed. This research includes a site investigation, which is seen as a primary stage in gathering geological, geotechnical, and other essential engineering data for structures’ safe and cost-effective design. Five boreholes at well-spaced spots were drilled for subsurface investigation at a maximum depth of 15 m to 30 m. The standard penetration tests (SPT) were performed at different depths, soil samples were taken at various intervals, and lithological changes were observed. The friction angle was between 19.6ºand 33.03º, whereas the cohesion ranges between 0.25 kg/cm<sup>2</sup> and 0.42 kg/cm<sup>2</sup>, indicating a strong resistance to shearing and a high capacity to sustain the load. Furthermore, the soil samples’ maximum dry density ranges from 1.63 g/cm<sup>3</sup> to 1.80 g/cm<sup>3</sup>. In addition, water table depths were recorded from 6.0 m to 7.0 m. The net bearing capacity for isolated/pad foundation at a depth of 1.5 m to 2.5 m below the ground level has been calculated as 95.0 to 120.0 kPa and 120.0 to 180.0 kPa for raft foundation. The net allowable pressure settlement limits for isolated/pad and raft foundations are 25 mm (1-inch) and 50 mm (2-inches), respectively. The investigation has found no severe geological flaws on the proposed construction site, and therefore it is appropriate for the construction of an Air Separation Unit (ASU) Oxygen Plant.
文摘Using NCEP 1° × 1° reanalysis data within 6 h, conventional observational data, data from regional automatic rainfall stations, satellite cloud pictures and Doppler radar data, we compared the physical conditions, dynamic and thermodynamic characteristics of two rainstorms in the southwest of Hunan Province on May 12 and June 15 in 2011. The results showed that the first process was triggered by strong cold air under unstable potential, while the second process was caused by shear line appearing from the east; during the first process, cold air divided into many parts and moved towards south, rainfall was uniform and lasted for a long time, while rainfall was relatively concentrated and strong, and lasted for a short time during the second process; the peak of K index appeared only during the second process; no sign of heavy rainfall was found from satellite cloud pictures and radar echo pictures during the first process, while obvious cloud cluster and echo ribbons could be found from satellite cloud pictures and radar echo pictures during the second process, which were the sign of heavy rainfall; slow movement of echo or little movement resulted in the second rainstorm, and constant echo intensity was the main reason for the occurrence of the second rainstorm. In addition, there was low-level southwest jet during the two processes, which provided favorable conditions for the transportation of water vapor and energy during the two processes. However, there was a great difference between the two rainstorms in the intensity and thickness of low-level jet, that is, the intensity and thickness of low-level jet during the first process were obviously weaker than these during the second process.
基金The present study is supported by the grant from the Natural Science Foundation of China.
文摘In the present paper,two-and three-dimensional velocity potentials generated by pulsating pressure distributions of infinite extent on the free surface of infinite-depth waters are strictly derived based on special cases of concentrated pulsating pressure.The far-field asymptotic behaviour of the potentials and the radiation conditions to be satisfied by them are discussed. It is proved in a general sense that the potentials should be composed of a forced wave component,a free wave component and a local disturbance component.The radiation condition of the forced wave component should correspond to the far-field asymptotic behaviour of the pressure distribution,Hence,the formulation of radiation conditions for the second-order diffraction potentials has theoretically become clear,The radiation conditions for two-and three-dimensional problems are explicitly given in the paper.
基金The authors acknowledge the financial support of the National Science Foundation of China grant Nos.51375472 and 51305429.
文摘A Nomex fabric/phenolic composite was prepared,and its tribological properties were evaluated under dry and water‐bathed sliding conditions by a pin‐on‐disk tribometer.The resulting size of the friction coefficient for the Nomex fabric/phenolic composite in the study occurred in the following order:dry sliding condition>distilled water‐bathed sliding condition>sea water‐bathed sliding condition.The fabric composite’s wear rate from high to low was as follows:distilled water‐bathed sliding condition>sea water‐bathed sliding condition>dry sliding condition.Under water‐bathed sliding conditions,penetration of water into the cracks accelerated the composite’s invalidation process,resulting in a higher wear rate.We also found that the extent of corrosion and transfer film formed on the counterpart pin significantly influenced the wear rate of the Nomex fabric composite.Discussion of the Nomex fabric composite’s wear mechanisms under the sliding conditions investigated is provided on the basis of the characterization results.
基金Chinese Academy of Sciences grant(KZCX2-YW-431)State Key Laboratory of Vegetation and Environmental Change(VEWALNE-project).
文摘Aims Biological soil crusts(BSCs)can affect soil properties including water dynamics and cycling of soil carbon and nitrogen in dryland ecosystems.Previous research has mostly focused on effects of BSCs on soil water distribution or carbon and nitrogen fixation in the surface soil layer.Thus,little is known about effects of BSCs on properties throughout the soil profile.In the current study,we assessed the effects of BSCs on the distribution of soil water content(SW),soil organic carbon content(SOC)and soil total nitrogen content(STN)throughout the soil profile as well as the influence of water conditions on the effects of BSCs.Methods In a field investigation in Mu Us Sandland,North China,soil samples were taken from plots with and without BSCs on 13 and 28 September 2006,respectively.On the two sampling dates,average soil gravimetric water content was 3.83%(61.29%)and 5.08%(60.89%),respectively,which were regarded as low and high water conditions.Soil samples were collected every 5 cm to a depth of 60 cm,and SW,SOC and STN were measured in the laboratory.Important Findings(i)BSCs affected profile distribution of SW,SOC and STN.In addition,water conditions within the plots significantly modified BSCs’effects on the profile distribution of SW,but marginally affected the effects on SOC and STN.(ii)Under high water conditions,SW in the surface soil layer(0–10 cm)was higher in soils with BSCs compared to those without BSCs,while the opposite was true in the deep soil layer(30–55 cm).(iii)Under low water conditions,SW was lower with BSCs compared with no BSCs in near-surface(5–20 cm)and deep(25–40 cm)soil layers.(iv)BSCs affected SOC and STN only in the surface soil layer(0–5 cm)and were modified by plot water conditions.
