Large-scale land consolidation projects(LCPs)have been carried out on the Loess Plateau to increase the area of agriculture land.The newly created land is prone to soil erosion under the effects of water and gravity.T...Large-scale land consolidation projects(LCPs)have been carried out on the Loess Plateau to increase the area of agriculture land.The newly created land is prone to soil erosion under the effects of water and gravity.Taking a typical high-filling body(HFB)formed by LCPs in Yan’an,China as the subject,this study comprehensively investigated the types and causes of soil erosion with multiple methods of field investigation,on-site monitoring and laboratory tests.Results showed that the HFB presented a composite pattern of soil erosion with multiple types mainly including underground erosion,mixed water-gravity erosion,seepage erosion,and scouring erosion.The type of erosion varied spatially in different parts of the HFB depending on the dominant factors,mainly including the groundwater state,rainfall,runoff,gravity action,topography,and soil erodibility.The underground erosion mainly occurred at the positions with higher groundwater level and larger hydraulic gradient,while scouring erosion mainly occurred at the positions with extensive interactions of surface runoff,channel slope gradient and soil properties.And near the leading edge of the top of the slope,a band of mixed watergravity erosion occurred owing to the effects of water and gravity.In addition,nearly saturated soils at the toe of HFB displayed groundwater exfiltration and slope-face slumping.Based on our findings on the causes and variation of soil erosion for the HFB,we proposed the following erosion prevention and control measures to protect the LCPs on the Loess Plateau:to construct drainage ditches and blind ditches to form a complete drainage system,plant alfalfa on the top platform to increase rainfall interception and reduce surface runoff,set seepage ditches and plant deep-rooted plants at the toe of the slope to improve slope toe stability,monitor groundwater level and slope deformation to learn the erosion dynamics and slope stability,and optimize the geometry of HFB such as the slope gradient and slope steps to reduce soil erosion.展开更多
A novel and effective BiOCl0.9I0.1/x%β-Bi2O3 composite catalyst was synthesized through a precipitation method. The structure, morphology, and optical properties of the samples were certified by X-ray diffraction, UV...A novel and effective BiOCl0.9I0.1/x%β-Bi2O3 composite catalyst was synthesized through a precipitation method. The structure, morphology, and optical properties of the samples were certified by X-ray diffraction, UV-Vis diffuse reflectance, scanning electron microscopy, and X-ray photoelectron spectroscopic characterizations. Photocatalytic experiments demonstrated that the synthesized BiOCl0.9I0.1/x%β-Bi2O3 composite catalyst exhibited excellent photocatalytic performance toward the degradation of tetracycline hydrochloride(TCH) under simulated sunlight. Furthermore, the TCH degradation rate of BiOCl0.9I0.1/15%β-Bi2O3 increased by 27.6% and 61.4% compared with those of the pure BiOCl0.9I0.1 and pure β-Bi2O3, respectively. Due to the multiple vacancies and valence states possessed by BiOCl0.9I0.1/x%β-Bi2O3, namely Bi5+, Bi(3-x)+, Bi5+–O, Bi3+–O, I- and I3-, the charge separation in photocatalysis reactions can be effectively promoted. The Mott-Schottky measurements indicate that the conduction band(CB) level of BiOCl0.9I0.1/15%β-Bi2O3 becomes more negative relative to that of BiOCl0.9I0.1, guaranteeing an advantageous effect on the redox ability of the photocatalyst. This study provides a new bright spot for the construction of high-performance photocatalysts.展开更多
This paper focuses on the heavy metal enrichment and heavy metal pollution degree associated with mining activities in some crops and the soils of different parent materials in the Xiaoqinling Gold Belt.According to t...This paper focuses on the heavy metal enrichment and heavy metal pollution degree associated with mining activities in some crops and the soils of different parent materials in the Xiaoqinling Gold Belt.According to the geochemical analysis results of the soils observed in the gold belt,the soils are most highly enriched in Pb,followed by Cr,Cu,and Zn.Furthermore,they are relatively poor in Hg,Cd,and As.It is also shown that the heavy metals in all kinds of soils have the same geochemical characteristics in the gold belt.As for the crops(such as corn and wheat)in the gold belt,Zn and Cu are the most abundant elements,followed by Pb and Cr.Meanwhile,Hg,Cd,and As were found to have relatively low concentrations in the crops.The heavy metals in wheat and corn have the same geochemical characteristics in the gold belt in general.Compared to the aeolian loess soils and the crops therein,heavy metals are more enriched in diluvial and alluvial soils and the crops therein.As shown by relevant studies,the Hg,Pb,Cd,Cu,and Zn pollution are mainly caused by mining activities.Corn and wheat in the gold belt have a high tendency of risk exposure to heavy metal pollution since they are mostly affected by mining activities and feature high background values of heavy metal concentrations.Furthermore,wheat is more liable to be enriched in heavy metals than corn is grown in all types of soils.The Hg pollution in soils leads to Hg accumulation,increasing the risk of Hg uptake in crops,and further affecting human health.This study will provide a scientific basis for the control and management of heavy metals in farmland soils of mining areas.展开更多
Giant landslides are common along the upper Yellow River from Longyang Gorge to Liujia Gorge, and some of them even blocked and dammed the upper Yellow River. Chronology is inevitable in studying the mechanism of gian...Giant landslides are common along the upper Yellow River from Longyang Gorge to Liujia Gorge, and some of them even blocked and dammed the upper Yellow River. Chronology is inevitable in studying the mechanism of giant landslides. Controversy exists about the chronology of those giant landslides, and some have not yet dated. The Dehenglong landslide is the largest one among them. In this study, OSL samples were collected from lacustrine silty sediments and loess directly overlying the landslide sediments, as well as fault sediments related to the landslide. This landslide yielded an age of 89 ±8 ka, which is identical with the fault age of 73 ±5 ka at two sigma errors. The agreement of a topographic analysis and the absolute age of landslides imply that the formation of the Dehenglong landslide is strongly correlated with the tectonic activity.展开更多
To study the current status and causes of the microplastic pollution in surface water of the Qinghai-Tibet Plateau,this paper compared the average microplastic abundance in sediments and surface water of the Qinghai-T...To study the current status and causes of the microplastic pollution in surface water of the Qinghai-Tibet Plateau,this paper compared the average microplastic abundance in sediments and surface water of the Qinghai-Tibet Plateau and the results are as follows.First,the average microplastic abundance in surface water of the independent rivers and the whole area is 247−2686 items/m^(3) and 856 items/m^(3),respectively.The average microplastic abundance in sediments of independent rivers or lakes and the whole area is 0−933 items/m^(2) and 362 items/m^(2),respectively.Meanwhile,the degree of microplastic pollution in river sediments is higher than that in lake sediments,and the rivers suffering from microplastic pollution mainly include the Brahmaputra River,Tongtian River,and Nujiang River.Second,compared with the microplastic pollution in other areas of the world,the levelof microplastic pollution in the lakes and rivers of the Qinghai-Tibet plateau is not lower than that of well-developed areas with more intensive human activities.Finally,this study suggests that relevant government departments of the Qinghai-Tibet Plateau should strengthen waste management strategies while developing tourism and that much attention should be paid to the impacts of microplastics in the water environment.展开更多
In this work,a covalent organic framework(COF),which is constructed by the building blocks of[5,10,15,20-tetrakis(4-aminophenyl)porphinato]copper(Ⅱ)(CuTAPP)and p-benzaldehyde,is employed to integrate with TiO_(2) for...In this work,a covalent organic framework(COF),which is constructed by the building blocks of[5,10,15,20-tetrakis(4-aminophenyl)porphinato]copper(Ⅱ)(CuTAPP)and p-benzaldehyde,is employed to integrate with TiO_(2) for the purpose of establishing a Z-scheme hybrid.Within the system,isonicotinic acid performs the role of a bridge that connects the two components through a coordination bond.Further photocatalytic application reveals the hybrid framework is able to catalyze CO_(2) conversion under simulated solar light,resulting in CO production rate of 50.5 μmol g^(-1)·h^(-1),about 9.9 and 24.5 times that of COF and pristine TiO_(2),respectively.The ameliorated catalytic performance owes much to the por-phyrin block acting as photosensitizer that augments the light absorbance,and the establishment of Z-scheme system between the inorganic and orga nic comp on ents that enhances the separati on of the carriers.In addition,the chemical bridge also ensures a steady usage and stable charge delivery in the catalysis.Our study sheds light on the development of versatile approaches to covalently in corporate COFs with inorga nic semic on ductors.展开更多
In order to study the migration and transformation mechanism of Hg content and occurrence form in subsurface flow zone of gold mining area in Loess Plateau and its influence on water environment,the field in-situ infi...In order to study the migration and transformation mechanism of Hg content and occurrence form in subsurface flow zone of gold mining area in Loess Plateau and its influence on water environment,the field in-situ infiltration test and laboratory test were carried out in three typical sections of river-side loess,alluvial and proluvial strata in Tongguan gold mining area of Shaanxi Province,and the following results were obtained:(1)The source of Hg in subsurface flow zone is mainly caused by mineral processing activities;(2)the subsurface flow zone in the study area is in alkaline environment,and the residual state,iron and manganese oxidation state,strong organic state and humic acid state of mercury in loess are equally divided in dry and oxidizing environment;mercury in river alluvial or diluvial strata is mainly concentrated in silt,tailings and clayey silt soil layer,and mercury has certain stability,and the form of mercury in loess is easier to transform than the other two media;(3)under the flooding condition,most of mercury is trapped in the silt layer in the undercurrent zone where the sand and silt layers alternate with each other and the river water and groundwater are disjointed,and the migration capacity of mercury is far less than that of loess layer and alluvial layer with close hydraulic connection;(4)infiltration at the flood level accelerates the migration of pollutants to the ground;(5)the soil in the undercurrent zone is overloaded and has seriously exceeded the standard.Although the groundwater monitoring results are safe this time,relevant enterprises or departments should continue to pay attention to improving the gold extraction process,especially vigorously rectify the small workshops for illegal gold extraction and the substandard discharge of the three wastes,and intensify efforts to solve the geological environmental problems of mines left over from history.At present,the occurrence form of mercury in the undercurrent zone is relatively stable,but the water and soil layers have been polluted.The risk of disjointed groundwater pollution can not be ignored while giving priority to the treatment of loess and river alluvial landform areas with close hydraulic links.The research results will provide a scientific basis for water conservancy departments to groundwater prevention and control in water-deficient areas of the Loess Plateau.展开更多
Hydrogel-Ⅰ was fabricated via sodium alginate in situ-embedding with MAL powders and then applied to decontaminating Pb(Ⅱ) from water. Conditions for preparing Hydrogel-Ⅰ and the adsorption of Pb(Ⅱ) over Hydrogel-...Hydrogel-Ⅰ was fabricated via sodium alginate in situ-embedding with MAL powders and then applied to decontaminating Pb(Ⅱ) from water. Conditions for preparing Hydrogel-Ⅰ and the adsorption of Pb(Ⅱ) over Hydrogel-I were optimized through response surface methodology coupled with central composite design. XPS revealed that the groups of —OH, —COO—, —NH, —NHand —CSS— carried by Hydrogel-Ⅰ were responsible for the uptake of Pb(Ⅱ). Ions exchange, surface complexation, electrostatic attraction and pore-filling effect contributed to the adsorption process. Adsorption performances of Pb(Ⅱ) by Hydrogel-Ⅰ and MAL powders were compared. Although they exhibited similar adsorption rate and maximum adsorption capacity(qm), the reusing ability of Hydrogel-Ⅰ was better and it was easier to be separated from aqueous solution after treatment. Even compared with organic hydrogel materials,Hydrogel-Ⅰ presented relatively quick adsorption speed and high adsorption capacity. It can be concluded that Hydrogel-Ⅰ could be an alternative scavenger for the treatment of Pb(Ⅱ) from aqueous solution.展开更多
This study aims to investigate the mechanisms and health risks of fluoride enrichment in groundwater in the Loess Plateau,China.By taking Dali County,Shaanxi Province,China as an example,this study obtains the followi...This study aims to investigate the mechanisms and health risks of fluoride enrichment in groundwater in the Loess Plateau,China.By taking Dali County,Shaanxi Province,China as an example,this study obtains the following results through field investigation and the analyses of water,soil,and crop samples.(1)The groundwater can be divided into two major types,namely the Quaternary pore-fissure water and Karst water.The Karst area and sandy area have high-quality groundwater and serve as the target areas for optional water supply.The groundwater in the study area is slightly alkaline and highly saline.Meanwhile,high-fluoride groundwater is mainly distributed in the loess and river alluvial plains in the depression area of the Guanzhong Basin and the discharge areas of the groundwater,with the highest fluoride concentration exceeding seven times the national standard.(2)Fluoride in groundwater mainly originates from a natural source and human activities.The natural source refers to the fluoride-bearing minerals in rocks and soil,and the fluoride from this source is mainly controlled by natural factors such as climate,geologic setting,pH,specific hydrochemical environment,ion exchange,and mineral saturation.Human activities in modern life can be further divided into industrial and agricultural sources primarily.(3)The health risks of fluoride contamination are very high in the Loess Plateau,especially for children compared to adults.Meanwhile,the risks of fluoride exposure through food intake are higher than those through drinking water intake.The authors suggest selecting target areas to improve water supply and ensure the safety of drinking water in the study area.Besides,it is necessary to plant crops with low fluoride content or cash crops and to conduct groundwater treatment to reduce the fluoride concentration in drinking water.These results will provide a theoretical basis for safe water supply in the faulted basin areas in the Loess Plateau.展开更多
In the process of geothermal exploitation and utilization, the reinjection amount of used geothermal water in super-deep and porous reservoir is small and significantly decreases over time. This has been a worldwide p...In the process of geothermal exploitation and utilization, the reinjection amount of used geothermal water in super-deep and porous reservoir is small and significantly decreases over time. This has been a worldwide problem, which greatly restricts the exploitation and utilization of geothermal resources. Based on a large amount of experiments and researches, the reinjection research on the tail water of Xianyang No.2 well, which is carried out by combining the application of hydrogeochemical simulation, clogging mechanism research and the reinjection experiment, has achieved breakthrough results. The clogging mechanism and indoor simulation experiment results show: Factors affecting the tail water reinjection of Xianyang No.2 well mainly include chemical clogging, suspended solids clogging, gas clogging, microbial clogging and composite clogging, yet the effect of particle migration on clogging has not been found; in the process of reinjection, chemical clogging was mainly caused by carbonates(mainly calcite), silicates(mainly chalcedony), and a small amount of iron minerals, and the clogging aggravated when the temperature rose; suspended solids clogging also aggravated when the temperature rose, which showed that particles formed by chemical reaction had a certain proportion in suspended solids.展开更多
This paper analyzed regional hydrogeochemical evolution characteristics of groundwater with respect to hydrogeological conditions in the Guanzhong Basin, China. Coefficient variation in the subregion between the Shich...This paper analyzed regional hydrogeochemical evolution characteristics of groundwater with respect to hydrogeological conditions in the Guanzhong Basin, China. Coefficient variation in the subregion between the Shichuan River and Luo River of the Guanzhong Basin is larger than other subregions, reflecting the more complicated hydrogeological conditions of this subregion. The hydrochemical components and hydrodynamic conditions of this area have distinct horizontal zoning characteristics, and hydrodynamic conditions play a controlling role in the groundwater’s hydrochemistry. The relationship between ions, and between ions and TDS（total dissolved solids） can give an indication of many charteristics of grounwater such as evaporation intensity, ion exchange, and the sources of chemical components. Results indicated that for the coefficient of variation（the coefficient of variation is a statistical measure of the distribution or dispersion of data around mean. This measure is used to analyze the difference of spread in the data relative to the mean value. Coefficient of variation is derived by dividing the standard deviation by the mean）, the minimum value of pH parameters is 0.03-0.07, the minimum value of HCO3-parameters is 0.24, while the maximum is the SO42-coefficinet at 1.67. A PHREEQC simulation demonstrated that different simulation paths roughly have the same trend in dissolution and precipitation of minerals. Along the direction of groundwater flow, the predminant precipitation is of calcite and gypsum and the cation exchange of Na+ and Ca2+ in some paths. However, in other paths, the precipitation of calcite and dissolution of gypsum and dolomite are the main actions, as well as the exchange of Mg2+ and Ca2+ in addition to Na+ and Ca2+.展开更多
Geotechnical tests conducted on clayey materials of Missole II, Douala sub-basin of Cameroon showed that these materials present: fines particles (55 to 78 wt.%), sand (22 to 44 wt.%), and plasticity index of 13.8 to ...Geotechnical tests conducted on clayey materials of Missole II, Douala sub-basin of Cameroon showed that these materials present: fines particles (55 to 78 wt.%), sand (22 to 44 wt.%), and plasticity index of 13.8 to 21.6%. The X-ray diffraction (XRD) and the chemical analysis revealed a kaolinite amount of 46 to 56 wt.%, 19 to 27 wt.% of illite, 12 to 19 wt.% of quartz, 3 to 5 wt.% of goethite, 2 to 5 wt.% of hematite, 1.5 to 5 wt.% of anatase, 2 to 3 wt.% of feldspar-K with 52.87 to 63.11 wt.% of SiO2, 18.08 to 24.31 wt.% of Al2O3, 3.28 to 11.45 wt.% of Fe2O3 and a small content of bases (<2 wt.%). The results of geotechnical tests combined to those of the XRD and the chemical analysis showed that the Missole II clayey materials are suitable for the manufacture of bricks, tiles and sandstones.展开更多
In this paper,the aqueous two-phase systems(ATPS)containing n-ethylpyridinium tetrafluoroborate([EPy]BF_(4)),sodium-based salts,and water were studied and the extraction efficiency of 2-chlorophenol was measured to st...In this paper,the aqueous two-phase systems(ATPS)containing n-ethylpyridinium tetrafluoroborate([EPy]BF_(4)),sodium-based salts,and water were studied and the extraction efficiency of 2-chlorophenol was measured to study the ATPS performance in extracting phenolic compounds.The binodal curves of[EPy]BF_(4)+sodium carbonate(Na_(2)CO_(3))ATPS and[EPy]BF_(4)+sodium dihydrogen phosphate(NaH_(2)PO_(4))ATPS have been determined at 308.15 K,318.15 K,and 328.15 K and atmospheric pressure.After getting good correlation with Merchuk equation,the binodal curves together with gravimetric method were used to calculate the tie-lines data.Furthermore,the reliability of tie-lines data was verified using Othmer-Tobias and Bancroft equations.Then,the salt influence and temperature influence on the phase behavior were discussed and the results show the salt-outing ability of Na_(2)CO_(3) is better than NaH_(2)PO_(4).With the aim of studying the ATPS performance in extracting phenolic compounds,extraction efficiency for 2-chlorophenol at different temperatures were studied and the results show that[EPy]BF_(4)+Na_(2)CO_(3) ATPS is preferred than[EPy]BF_(4)+NaH_(2)PO_(4) ATPS in applications.展开更多
22 typical test points and 8 profiles were selected and arranged in the plain of Yili River Valley based on lithological distribution and sedimentary characteristics to study spatial variability of soil infiltration c...22 typical test points and 8 profiles were selected and arranged in the plain of Yili River Valley based on lithological distribution and sedimentary characteristics to study spatial variability of soil infiltration coefficient. The results show that the infiltration coefficient of different geo-morphic units is as follows: the desert area > the pre-mountain alluvial-proluvial plain > river terrace,which is mainly related to the lithology of aeration zone,buried depth of groundwater and underlying surface. For the infiltration coefficient of different aeration zone mediums,the results are consistent with the changing law. The partition of plain of the Yili River Valley is based on geo-morphic units,infiltration coefficient and the lithology of aeration zone. The maximum infiltration coefficient is concentrated in the desert area,and there is zonal distribution of infiltration coefficient in plane.展开更多
In order to explore the spatial and temporal changes of runoff and sediment in the Taohe River and its driving mechanism,Spearman correlation coefficient method,Mann-Kendell mutation test method and ordered clustering...In order to explore the spatial and temporal changes of runoff and sediment in the Taohe River and its driving mechanism,Spearman correlation coefficient method,Mann-Kendell mutation test method and ordered clustering method were used to analyze the changes of runoff and sediment discharge and their driving factors in four hydrological stations along the Taohe River from 1957 to 2016.The results showed that the correlation between runoff and sediment of the four hydrological stations along the Taohe River was significant,and the correlation coefficient was 0.728-0.984.The runoff and sediment transport in the interval showed an increasing and decreasing trend.The decrease rate of runoff was 133.82%-216.17%higher than that of Xiabagou station,and the decrease rate of sediment transport was 250.49%-4766.33%higher than that of Xiabagou station.The mutation year of the Taohe River runoff occurred in 1986,and the maximum decrease was 35%.The water-sediment relationship curves of different periods showed that the sediment discharge of the four stations changed abruptly around 1990,and the maximum reduction before and after the mutation was up to 73%,and the sediment discharge in the river channel decreased significantly.The research showed that human activities were the main driving factors for the change of water-sediment relationship in the Taohe River.展开更多
The Xi'an Depression in the Guanzhong Basin of western China has been suggested to contain geothermal resources that could aid China in achieving carbon neutrality and optimizing energy structure.However,the high ...The Xi'an Depression in the Guanzhong Basin of western China has been suggested to contain geothermal resources that could aid China in achieving carbon neutrality and optimizing energy structure.However,the high concentration of total dissolved solids(TDS)and scale-forming ions in geothermal water from the depression causes severe scaling problems in harvesting geothermal energy.To reduce scale-related problems,accurate identification of scale types and prediction of scaling during geothermal energy utilization are crucial.This study starts with identifying the types and trends of scaling in the study area,using index-based discriminant methods and hydrogeochemical simulation to calculate and analyze the mineral saturation index of water samples from some wellheads and of reconstructed fluid samples of geothermal reservoirs.The results indicate that the scales are mostly calcium carbonate scales rather than sulfate scales as a result of temperature changes.Several portions of the geothermal water systems are found to have distinct mineral scaling components.Quartz and chalcedony are formed in low temperature areas,while carbonate minerals are in high temperature areas.Despite the low iron content of geothermal water samples from the study area,scaling is very common due to scaling-prone iron minerals.The findings can be used to evaluate geothermal drainage systems and guide anti-scaling during geothermal energy utilization in similar settings.展开更多
This paper coupled a water-air two-phase hydrodynamic(WATPH)model with the Iverson’s method to analyze the influence of the Lisse effect on the fast groundwater pressure(P_(w))response and the slope stability.Further...This paper coupled a water-air two-phase hydrodynamic(WATPH)model with the Iverson’s method to analyze the influence of the Lisse effect on the fast groundwater pressure(P_(w))response and the slope stability.Furthermore,the sensitivities of the driving force and loess soil parameters were investigated.Results showed that the WATPH model simulated the height and rise of the depth to the water table reasonably well.The depth to water table before rainfall(H0)had a significant impact on the Lisse effect and the slope stability.When the H_(0) was less than approximately 1 m,the rainfall triggered a significant Lisse effect and decreased the slope factor of safety(F_(s)).When the rainfall intensity(R_(i))was higher than the saturated hydraulic conductivity(K_(s)),the Lisse effect and the F_(s) slightly changed with the increase of the R_(i),and the slope tended to be unstable with continuous rainfall.With increasing K_(s),the Lisse effect noticeably increased,and the minimum F_(s) quickly decreases.The analysis of the normalized sensitivity coefficient revealed that H_(0) had a dramatic impact on the Lisse effect and loess slope stability.The different R_(i) and K_(s) values had prominent influences on the Lisse effect and slight impacts on F_(s).展开更多
The cobalt-carbonate(CoCi)/NiFeOOH double-layer co-catalyst was prepared on bismuth vanadate(BiVO_(4)).Compared with the same type of electrode(Co-Pi/NiFeOOH/BiVO_(4) and Co-Sil/NiFeOOH/BiVO_(4)),the photoelectrochemi...The cobalt-carbonate(CoCi)/NiFeOOH double-layer co-catalyst was prepared on bismuth vanadate(BiVO_(4)).Compared with the same type of electrode(Co-Pi/NiFeOOH/BiVO_(4) and Co-Sil/NiFeOOH/BiVO_(4)),the photoelectrochemical(PEC)performance of the composite electrode presents the most excellent performance.The Co-Ci/NiFeOOH/BiVO_(4) electrode prepared by photoelectric deposition(PED)achieves a photocurrent density of 4.1 mA/cm^(2) at 1.23 V vs RHE,and the applied bias photon-current efficiency(ABPE)is up to 0.95%.In addition,with the help of the equivalent circuit fitting in electrochemical impedance spectroscopy(EIS),the charge transfer resistance(R_(ct))of Co-Ci/NiFeOOH/BiVO_(4) is only 108.9Ω,which is 16%that of BiVO_(4).The enhanced PEC performance of Co-Ci/NiFeOOH/BiVO_(4) in the double-layer cocatalyst system is attributed to the outstanding advantages of Co-Ci cocatalyst in oxygen vacancy defects,superior to other cobalt-based catalysts in promoting charge transfer and improving the kinetics of water oxidation.This makes Co-Ci co-catalyst become one of the favorable competitors in the field of photoelectric catalysis.展开更多
Soil nitrogen(N) is critical to ecosystem services and environmental quality. Hotspots of soil N in areas with high soil moisture have been widely studied, however, their spatial distribution and their linkage with so...Soil nitrogen(N) is critical to ecosystem services and environmental quality. Hotspots of soil N in areas with high soil moisture have been widely studied, however, their spatial distribution and their linkage with soil N variation have seldom been examined at a catchment scale in areas with low soil water content. We investigated the spatial variation of soil N and its hotspots in a mixed land cover catchment on the Chinese Loess Plateau and used multiple statistical methods to evaluate the effects of the critical environmental factors on soil N variation and potential hotspots. The results demonstrated that land cover, soil moisture, elevation, plan curvature and flow accumulation were the dominant factors affecting the spatial variation of soil nitrate(NN), while land cover and slope aspect were the most important factors impacting the spatial distribution of soil ammonium(AN) and total nitrogen(TN). In the studied catchment, the forestland, gully land and grassland were found to be the potential hotspots of soil NN, AN and TN accumulation, respectively. We concluded that land cover and slope aspect could be proxies to determine the potential hotspots of soil N at the catchment scale. Overall, land cover was the most important factor that resulted in the spatial variations of soil N. The findings may help us to better understand the environmental factors affecting soil N hotspots and their spatial variation at the catchment scale in terrestrial ecosystems.展开更多
An accurate prediction of peak discharge in watersheds is critical not only for water resource manage-ment,but also for understanding the complex relationships of hydrological processes.In this study,a modified peak d...An accurate prediction of peak discharge in watersheds is critical not only for water resource manage-ment,but also for understanding the complex relationships of hydrological processes.In this study,a modified peak discharge formula based on the Chemicals,Runoff,and Erosion from Agricultural Man-agement Systems(CREAMS)model was developed by introducing rainfall intensity and soil moisture factors.The reliability of the proposed method was tested with data from 1464 storm events in 41 watersheds and was applied to 256 storm events in five remaining typical watersheds using the opti-mized parameters.The results indicate that the proposed method is highly accurate in terms of model efficiency,as determined by Nash-Sutcliffe efficiencies(NSEs)of 88.60%,74.04%,and 90.12%during the calibration,validation,and application cases,respectively.Furthermore,it performed better than the original and modified CREAMS methods.Subsequently,using the parameters derived from the initial 41 watersheds and the runoff estimated using the modified Soil Conservation Service curve number(SCS-CN)method,the proposed method was used to predict the peak discharge from the last five typical watersheds.Large NSE(63.88-80.83%)and low root mean square error(RMSE)values(0.31-35.93 m^(3)s^(-1))were obtained for the five watersheds.Overall,the proposed peak discharge model,combined with the modified SCS-CN method,may accurately predict event-based peak discharge and runoff for general applications under various hydrological and geomorphic conditions in the Loess Plateau region.展开更多
基金the National Natural Science Foundation of China(Grant Nos.41790443,41927806,and 32071586)the Fundamental Research Funds for the Central Universities(Grant Nos.300102212213)Young Talent Fund of Association for Science and Technology in Shaanxi,China(Grant No.20220707)。
文摘Large-scale land consolidation projects(LCPs)have been carried out on the Loess Plateau to increase the area of agriculture land.The newly created land is prone to soil erosion under the effects of water and gravity.Taking a typical high-filling body(HFB)formed by LCPs in Yan’an,China as the subject,this study comprehensively investigated the types and causes of soil erosion with multiple methods of field investigation,on-site monitoring and laboratory tests.Results showed that the HFB presented a composite pattern of soil erosion with multiple types mainly including underground erosion,mixed water-gravity erosion,seepage erosion,and scouring erosion.The type of erosion varied spatially in different parts of the HFB depending on the dominant factors,mainly including the groundwater state,rainfall,runoff,gravity action,topography,and soil erodibility.The underground erosion mainly occurred at the positions with higher groundwater level and larger hydraulic gradient,while scouring erosion mainly occurred at the positions with extensive interactions of surface runoff,channel slope gradient and soil properties.And near the leading edge of the top of the slope,a band of mixed watergravity erosion occurred owing to the effects of water and gravity.In addition,nearly saturated soils at the toe of HFB displayed groundwater exfiltration and slope-face slumping.Based on our findings on the causes and variation of soil erosion for the HFB,we proposed the following erosion prevention and control measures to protect the LCPs on the Loess Plateau:to construct drainage ditches and blind ditches to form a complete drainage system,plant alfalfa on the top platform to increase rainfall interception and reduce surface runoff,set seepage ditches and plant deep-rooted plants at the toe of the slope to improve slope toe stability,monitor groundwater level and slope deformation to learn the erosion dynamics and slope stability,and optimize the geometry of HFB such as the slope gradient and slope steps to reduce soil erosion.
文摘A novel and effective BiOCl0.9I0.1/x%β-Bi2O3 composite catalyst was synthesized through a precipitation method. The structure, morphology, and optical properties of the samples were certified by X-ray diffraction, UV-Vis diffuse reflectance, scanning electron microscopy, and X-ray photoelectron spectroscopic characterizations. Photocatalytic experiments demonstrated that the synthesized BiOCl0.9I0.1/x%β-Bi2O3 composite catalyst exhibited excellent photocatalytic performance toward the degradation of tetracycline hydrochloride(TCH) under simulated sunlight. Furthermore, the TCH degradation rate of BiOCl0.9I0.1/15%β-Bi2O3 increased by 27.6% and 61.4% compared with those of the pure BiOCl0.9I0.1 and pure β-Bi2O3, respectively. Due to the multiple vacancies and valence states possessed by BiOCl0.9I0.1/x%β-Bi2O3, namely Bi5+, Bi(3-x)+, Bi5+–O, Bi3+–O, I- and I3-, the charge separation in photocatalysis reactions can be effectively promoted. The Mott-Schottky measurements indicate that the conduction band(CB) level of BiOCl0.9I0.1/15%β-Bi2O3 becomes more negative relative to that of BiOCl0.9I0.1, guaranteeing an advantageous effect on the redox ability of the photocatalyst. This study provides a new bright spot for the construction of high-performance photocatalysts.
基金funded by the survey projects initiated by the Ministry of Natural and Resources of the People’s Republic of China(DD20189220,1212010741003,1212011220224,and 121201011000150022)the Public Welfare Scientific Research Project launched by the Ministry of Natural and Resources of the People’s Republic of China(201111020)+1 种基金the project of 2015 Natural Science Basic Research Program of Shaanxi(2015JM4129)the project of 2016 Fundamental Research Funds for the Central Universities(open fund)(310829161128).
文摘This paper focuses on the heavy metal enrichment and heavy metal pollution degree associated with mining activities in some crops and the soils of different parent materials in the Xiaoqinling Gold Belt.According to the geochemical analysis results of the soils observed in the gold belt,the soils are most highly enriched in Pb,followed by Cr,Cu,and Zn.Furthermore,they are relatively poor in Hg,Cd,and As.It is also shown that the heavy metals in all kinds of soils have the same geochemical characteristics in the gold belt.As for the crops(such as corn and wheat)in the gold belt,Zn and Cu are the most abundant elements,followed by Pb and Cr.Meanwhile,Hg,Cd,and As were found to have relatively low concentrations in the crops.The heavy metals in wheat and corn have the same geochemical characteristics in the gold belt in general.Compared to the aeolian loess soils and the crops therein,heavy metals are more enriched in diluvial and alluvial soils and the crops therein.As shown by relevant studies,the Hg,Pb,Cd,Cu,and Zn pollution are mainly caused by mining activities.Corn and wheat in the gold belt have a high tendency of risk exposure to heavy metal pollution since they are mostly affected by mining activities and feature high background values of heavy metal concentrations.Furthermore,wheat is more liable to be enriched in heavy metals than corn is grown in all types of soils.The Hg pollution in soils leads to Hg accumulation,increasing the risk of Hg uptake in crops,and further affecting human health.This study will provide a scientific basis for the control and management of heavy metals in farmland soils of mining areas.
基金supported by China NSF(grant No.41172168)Mechanism of giant landslides from Longyang Gorge to Liujia Gorge along upper Yellow River(Grant No.1212010818083)
文摘Giant landslides are common along the upper Yellow River from Longyang Gorge to Liujia Gorge, and some of them even blocked and dammed the upper Yellow River. Chronology is inevitable in studying the mechanism of giant landslides. Controversy exists about the chronology of those giant landslides, and some have not yet dated. The Dehenglong landslide is the largest one among them. In this study, OSL samples were collected from lacustrine silty sediments and loess directly overlying the landslide sediments, as well as fault sediments related to the landslide. This landslide yielded an age of 89 ±8 ka, which is identical with the fault age of 73 ±5 ka at two sigma errors. The agreement of a topographic analysis and the absolute age of landslides imply that the formation of the Dehenglong landslide is strongly correlated with the tectonic activity.
基金funded by the survey projects initiated by the Ministry of Natural Resources of the People’s Republic of China(DD20189220,1212010741003,1212011220224,and 121201011000150022)the Public Welfare Scientific Research Project launched by the Ministry of Natural Resources of the People’s Republic of China(201111020)+3 种基金the project of 2015 Natural Science Basic Research Plan of Shaanxi Province(2015JM4129)the project of 2016 Fundamental Research Funds for the Central Universities(open fund310829161128)the project of 2021 Fundamental Research Funds for the Central Universities(open fund).
文摘To study the current status and causes of the microplastic pollution in surface water of the Qinghai-Tibet Plateau,this paper compared the average microplastic abundance in sediments and surface water of the Qinghai-Tibet Plateau and the results are as follows.First,the average microplastic abundance in surface water of the independent rivers and the whole area is 247−2686 items/m^(3) and 856 items/m^(3),respectively.The average microplastic abundance in sediments of independent rivers or lakes and the whole area is 0−933 items/m^(2) and 362 items/m^(2),respectively.Meanwhile,the degree of microplastic pollution in river sediments is higher than that in lake sediments,and the rivers suffering from microplastic pollution mainly include the Brahmaputra River,Tongtian River,and Nujiang River.Second,compared with the microplastic pollution in other areas of the world,the levelof microplastic pollution in the lakes and rivers of the Qinghai-Tibet plateau is not lower than that of well-developed areas with more intensive human activities.Finally,this study suggests that relevant government departments of the Qinghai-Tibet Plateau should strengthen waste management strategies while developing tourism and that much attention should be paid to the impacts of microplastics in the water environment.
基金financially supported by the National Natural Science Foundation of China (21663027 and 21808189)the Key Science and Technology Foundation of Gansu Province (20YF3GA021)+2 种基金the Innovation funding program of Universities of Gansu province (2020B-091)the Opening Project of Key Laboratory of Green Chemistry of Sichuan Institutes of Higher Education (LYJ18205)the Promotion Project of Young-Teacher Researchcapacity of Northwest Normal University (NWNU-LKQN-18-5).
文摘In this work,a covalent organic framework(COF),which is constructed by the building blocks of[5,10,15,20-tetrakis(4-aminophenyl)porphinato]copper(Ⅱ)(CuTAPP)and p-benzaldehyde,is employed to integrate with TiO_(2) for the purpose of establishing a Z-scheme hybrid.Within the system,isonicotinic acid performs the role of a bridge that connects the two components through a coordination bond.Further photocatalytic application reveals the hybrid framework is able to catalyze CO_(2) conversion under simulated solar light,resulting in CO production rate of 50.5 μmol g^(-1)·h^(-1),about 9.9 and 24.5 times that of COF and pristine TiO_(2),respectively.The ameliorated catalytic performance owes much to the por-phyrin block acting as photosensitizer that augments the light absorbance,and the establishment of Z-scheme system between the inorganic and orga nic comp on ents that enhances the separati on of the carriers.In addition,the chemical bridge also ensures a steady usage and stable charge delivery in the catalysis.Our study sheds light on the development of versatile approaches to covalently in corporate COFs with inorga nic semic on ductors.
基金This study was funded by the survey projects initiated by the Ministry of Natural Resources of the People’s Republic of China(1212010741003,1212011220224,and 121201011000150022)China Geological Survey(DD20189220,DD20211317)+2 种基金the public welfare scientific research project launched by the Ministry of Natural Resources of the People’s Republic of China(201111020)the project of 2015 Natural Science Basic Research Plan of Shaanxi Province of China(2015JM4129)the project of 2016 Fundamental Research Funds for the Central Universities of China(an open-end fund)(310829161128).
文摘In order to study the migration and transformation mechanism of Hg content and occurrence form in subsurface flow zone of gold mining area in Loess Plateau and its influence on water environment,the field in-situ infiltration test and laboratory test were carried out in three typical sections of river-side loess,alluvial and proluvial strata in Tongguan gold mining area of Shaanxi Province,and the following results were obtained:(1)The source of Hg in subsurface flow zone is mainly caused by mineral processing activities;(2)the subsurface flow zone in the study area is in alkaline environment,and the residual state,iron and manganese oxidation state,strong organic state and humic acid state of mercury in loess are equally divided in dry and oxidizing environment;mercury in river alluvial or diluvial strata is mainly concentrated in silt,tailings and clayey silt soil layer,and mercury has certain stability,and the form of mercury in loess is easier to transform than the other two media;(3)under the flooding condition,most of mercury is trapped in the silt layer in the undercurrent zone where the sand and silt layers alternate with each other and the river water and groundwater are disjointed,and the migration capacity of mercury is far less than that of loess layer and alluvial layer with close hydraulic connection;(4)infiltration at the flood level accelerates the migration of pollutants to the ground;(5)the soil in the undercurrent zone is overloaded and has seriously exceeded the standard.Although the groundwater monitoring results are safe this time,relevant enterprises or departments should continue to pay attention to improving the gold extraction process,especially vigorously rectify the small workshops for illegal gold extraction and the substandard discharge of the three wastes,and intensify efforts to solve the geological environmental problems of mines left over from history.At present,the occurrence form of mercury in the undercurrent zone is relatively stable,but the water and soil layers have been polluted.The risk of disjointed groundwater pollution can not be ignored while giving priority to the treatment of loess and river alluvial landform areas with close hydraulic links.The research results will provide a scientific basis for water conservancy departments to groundwater prevention and control in water-deficient areas of the Loess Plateau.
基金funded by the National Key Research and Development Project (No.2019YFC1804800)Key R&D Program of Shaanxi Province,China (No.2019SF-253)+3 种基金the Fundamental Research Funds for the Central Universities,China (No.300102291504)the Pearl River S&T Nova Program of Guangzhou,China (No.201710010065)the Science and Technology Program of Guangdong Forestry Administration,China (No.2020-KYXM-08)the Key Laboratory of Resource Chemistry,Ministry of Education,China (No.KLRC_ME2102)。
文摘Hydrogel-Ⅰ was fabricated via sodium alginate in situ-embedding with MAL powders and then applied to decontaminating Pb(Ⅱ) from water. Conditions for preparing Hydrogel-Ⅰ and the adsorption of Pb(Ⅱ) over Hydrogel-I were optimized through response surface methodology coupled with central composite design. XPS revealed that the groups of —OH, —COO—, —NH, —NHand —CSS— carried by Hydrogel-Ⅰ were responsible for the uptake of Pb(Ⅱ). Ions exchange, surface complexation, electrostatic attraction and pore-filling effect contributed to the adsorption process. Adsorption performances of Pb(Ⅱ) by Hydrogel-Ⅰ and MAL powders were compared. Although they exhibited similar adsorption rate and maximum adsorption capacity(qm), the reusing ability of Hydrogel-Ⅰ was better and it was easier to be separated from aqueous solution after treatment. Even compared with organic hydrogel materials,Hydrogel-Ⅰ presented relatively quick adsorption speed and high adsorption capacity. It can be concluded that Hydrogel-Ⅰ could be an alternative scavenger for the treatment of Pb(Ⅱ) from aqueous solution.
基金This study was funded by the survey projects initiated by the China Geological Survey(DD20189220,DD20211317,and 1212010634713).
文摘This study aims to investigate the mechanisms and health risks of fluoride enrichment in groundwater in the Loess Plateau,China.By taking Dali County,Shaanxi Province,China as an example,this study obtains the following results through field investigation and the analyses of water,soil,and crop samples.(1)The groundwater can be divided into two major types,namely the Quaternary pore-fissure water and Karst water.The Karst area and sandy area have high-quality groundwater and serve as the target areas for optional water supply.The groundwater in the study area is slightly alkaline and highly saline.Meanwhile,high-fluoride groundwater is mainly distributed in the loess and river alluvial plains in the depression area of the Guanzhong Basin and the discharge areas of the groundwater,with the highest fluoride concentration exceeding seven times the national standard.(2)Fluoride in groundwater mainly originates from a natural source and human activities.The natural source refers to the fluoride-bearing minerals in rocks and soil,and the fluoride from this source is mainly controlled by natural factors such as climate,geologic setting,pH,specific hydrochemical environment,ion exchange,and mineral saturation.Human activities in modern life can be further divided into industrial and agricultural sources primarily.(3)The health risks of fluoride contamination are very high in the Loess Plateau,especially for children compared to adults.Meanwhile,the risks of fluoride exposure through food intake are higher than those through drinking water intake.The authors suggest selecting target areas to improve water supply and ensure the safety of drinking water in the study area.Besides,it is necessary to plant crops with low fluoride content or cash crops and to conduct groundwater treatment to reduce the fluoride concentration in drinking water.These results will provide a theoretical basis for safe water supply in the faulted basin areas in the Loess Plateau.
基金funded by National Science Foundation Project in 2015 (No.41472221)
文摘In the process of geothermal exploitation and utilization, the reinjection amount of used geothermal water in super-deep and porous reservoir is small and significantly decreases over time. This has been a worldwide problem, which greatly restricts the exploitation and utilization of geothermal resources. Based on a large amount of experiments and researches, the reinjection research on the tail water of Xianyang No.2 well, which is carried out by combining the application of hydrogeochemical simulation, clogging mechanism research and the reinjection experiment, has achieved breakthrough results. The clogging mechanism and indoor simulation experiment results show: Factors affecting the tail water reinjection of Xianyang No.2 well mainly include chemical clogging, suspended solids clogging, gas clogging, microbial clogging and composite clogging, yet the effect of particle migration on clogging has not been found; in the process of reinjection, chemical clogging was mainly caused by carbonates(mainly calcite), silicates(mainly chalcedony), and a small amount of iron minerals, and the clogging aggravated when the temperature rose; suspended solids clogging also aggravated when the temperature rose, which showed that particles formed by chemical reaction had a certain proportion in suspended solids.
基金supported by the China Geological Survey(No.1212010634700)through groundwater exploration to ensure the water supply security of endemic disease areas
文摘This paper analyzed regional hydrogeochemical evolution characteristics of groundwater with respect to hydrogeological conditions in the Guanzhong Basin, China. Coefficient variation in the subregion between the Shichuan River and Luo River of the Guanzhong Basin is larger than other subregions, reflecting the more complicated hydrogeological conditions of this subregion. The hydrochemical components and hydrodynamic conditions of this area have distinct horizontal zoning characteristics, and hydrodynamic conditions play a controlling role in the groundwater’s hydrochemistry. The relationship between ions, and between ions and TDS（total dissolved solids） can give an indication of many charteristics of grounwater such as evaporation intensity, ion exchange, and the sources of chemical components. Results indicated that for the coefficient of variation（the coefficient of variation is a statistical measure of the distribution or dispersion of data around mean. This measure is used to analyze the difference of spread in the data relative to the mean value. Coefficient of variation is derived by dividing the standard deviation by the mean）, the minimum value of pH parameters is 0.03-0.07, the minimum value of HCO3-parameters is 0.24, while the maximum is the SO42-coefficinet at 1.67. A PHREEQC simulation demonstrated that different simulation paths roughly have the same trend in dissolution and precipitation of minerals. Along the direction of groundwater flow, the predminant precipitation is of calcite and gypsum and the cation exchange of Na+ and Ca2+ in some paths. However, in other paths, the precipitation of calcite and dissolution of gypsum and dolomite are the main actions, as well as the exchange of Mg2+ and Ca2+ in addition to Na+ and Ca2+.
文摘Geotechnical tests conducted on clayey materials of Missole II, Douala sub-basin of Cameroon showed that these materials present: fines particles (55 to 78 wt.%), sand (22 to 44 wt.%), and plasticity index of 13.8 to 21.6%. The X-ray diffraction (XRD) and the chemical analysis revealed a kaolinite amount of 46 to 56 wt.%, 19 to 27 wt.% of illite, 12 to 19 wt.% of quartz, 3 to 5 wt.% of goethite, 2 to 5 wt.% of hematite, 1.5 to 5 wt.% of anatase, 2 to 3 wt.% of feldspar-K with 52.87 to 63.11 wt.% of SiO2, 18.08 to 24.31 wt.% of Al2O3, 3.28 to 11.45 wt.% of Fe2O3 and a small content of bases (<2 wt.%). The results of geotechnical tests combined to those of the XRD and the chemical analysis showed that the Missole II clayey materials are suitable for the manufacture of bricks, tiles and sandstones.
基金sponsored by the Natural Science Foundation for Distinguished Young Scholars of Guangdong Provence (2019B151502038)the National Natural Science Foundation of China (21706038, 21808042, 21808039)+2 种基金the Fundamental Research Funds for the Central Universities (300102299202)the National Training Projects of the University Students’ Innovation and Entrepreneurship program (201910710125)the Scientific Innovation Practice Project of Postgraduates of Chang’an University (300103703058, 300103703016)
文摘In this paper,the aqueous two-phase systems(ATPS)containing n-ethylpyridinium tetrafluoroborate([EPy]BF_(4)),sodium-based salts,and water were studied and the extraction efficiency of 2-chlorophenol was measured to study the ATPS performance in extracting phenolic compounds.The binodal curves of[EPy]BF_(4)+sodium carbonate(Na_(2)CO_(3))ATPS and[EPy]BF_(4)+sodium dihydrogen phosphate(NaH_(2)PO_(4))ATPS have been determined at 308.15 K,318.15 K,and 328.15 K and atmospheric pressure.After getting good correlation with Merchuk equation,the binodal curves together with gravimetric method were used to calculate the tie-lines data.Furthermore,the reliability of tie-lines data was verified using Othmer-Tobias and Bancroft equations.Then,the salt influence and temperature influence on the phase behavior were discussed and the results show the salt-outing ability of Na_(2)CO_(3) is better than NaH_(2)PO_(4).With the aim of studying the ATPS performance in extracting phenolic compounds,extraction efficiency for 2-chlorophenol at different temperatures were studied and the results show that[EPy]BF_(4)+Na_(2)CO_(3) ATPS is preferred than[EPy]BF_(4)+NaH_(2)PO_(4) ATPS in applications.
基金Supported by National Natural Science Foundation of China(41202178,41372260,41472220)Open Foundation for Key Laboratories of Ministry of Education of China(2014G1502024)+1 种基金Project of China Geological Survey(1212011014024)Innovation Capability Support Program of Shaanxi(2019TD-040)。
文摘22 typical test points and 8 profiles were selected and arranged in the plain of Yili River Valley based on lithological distribution and sedimentary characteristics to study spatial variability of soil infiltration coefficient. The results show that the infiltration coefficient of different geo-morphic units is as follows: the desert area > the pre-mountain alluvial-proluvial plain > river terrace,which is mainly related to the lithology of aeration zone,buried depth of groundwater and underlying surface. For the infiltration coefficient of different aeration zone mediums,the results are consistent with the changing law. The partition of plain of the Yili River Valley is based on geo-morphic units,infiltration coefficient and the lithology of aeration zone. The maximum infiltration coefficient is concentrated in the desert area,and there is zonal distribution of infiltration coefficient in plane.
基金Supported by Gansu Youth Science and Technology Fund Program(21JR7RA778)Innovation Fund Project of Gansu Provincial Universities(2020A-186)。
文摘In order to explore the spatial and temporal changes of runoff and sediment in the Taohe River and its driving mechanism,Spearman correlation coefficient method,Mann-Kendell mutation test method and ordered clustering method were used to analyze the changes of runoff and sediment discharge and their driving factors in four hydrological stations along the Taohe River from 1957 to 2016.The results showed that the correlation between runoff and sediment of the four hydrological stations along the Taohe River was significant,and the correlation coefficient was 0.728-0.984.The runoff and sediment transport in the interval showed an increasing and decreasing trend.The decrease rate of runoff was 133.82%-216.17%higher than that of Xiabagou station,and the decrease rate of sediment transport was 250.49%-4766.33%higher than that of Xiabagou station.The mutation year of the Taohe River runoff occurred in 1986,and the maximum decrease was 35%.The water-sediment relationship curves of different periods showed that the sediment discharge of the four stations changed abruptly around 1990,and the maximum reduction before and after the mutation was up to 73%,and the sediment discharge in the river channel decreased significantly.The research showed that human activities were the main driving factors for the change of water-sediment relationship in the Taohe River.
基金supported by the Research Project on Middle and Deep Geothermal Energy Utilization in Guanzhong Area of Shaanxi ProvincedSpecial Study on Sandstone Thermal Storage Recharge(No.21152920349)the Special Fund for Basic Scientific Research Operating Expenses of Central Universities of Chang'an University(Grant No.300102292903)+1 种基金the Basic Research Plan of Natural Sciences of Shaanxi Province General Project“Study on Loess Landslide Chronology Based on OSL Dating Technology”(Grant No.2017JM4018)the Open Fund of State Key Laboratory of Loess and Quaternary Geology(Grant No.SKLLQG1933).
文摘The Xi'an Depression in the Guanzhong Basin of western China has been suggested to contain geothermal resources that could aid China in achieving carbon neutrality and optimizing energy structure.However,the high concentration of total dissolved solids(TDS)and scale-forming ions in geothermal water from the depression causes severe scaling problems in harvesting geothermal energy.To reduce scale-related problems,accurate identification of scale types and prediction of scaling during geothermal energy utilization are crucial.This study starts with identifying the types and trends of scaling in the study area,using index-based discriminant methods and hydrogeochemical simulation to calculate and analyze the mineral saturation index of water samples from some wellheads and of reconstructed fluid samples of geothermal reservoirs.The results indicate that the scales are mostly calcium carbonate scales rather than sulfate scales as a result of temperature changes.Several portions of the geothermal water systems are found to have distinct mineral scaling components.Quartz and chalcedony are formed in low temperature areas,while carbonate minerals are in high temperature areas.Despite the low iron content of geothermal water samples from the study area,scaling is very common due to scaling-prone iron minerals.The findings can be used to evaluate geothermal drainage systems and guide anti-scaling during geothermal energy utilization in similar settings.
基金supported by the National Natural Science Foundation of China(No.41972248)the Natural Science Basic Research Plan in Shaanxi Province of China(Nos.2019JM-146,2024JC-YBQN-0274)the Fundamental Research Funds for the Central Universities,CHD(No.300102293103).
文摘This paper coupled a water-air two-phase hydrodynamic(WATPH)model with the Iverson’s method to analyze the influence of the Lisse effect on the fast groundwater pressure(P_(w))response and the slope stability.Furthermore,the sensitivities of the driving force and loess soil parameters were investigated.Results showed that the WATPH model simulated the height and rise of the depth to the water table reasonably well.The depth to water table before rainfall(H0)had a significant impact on the Lisse effect and the slope stability.When the H_(0) was less than approximately 1 m,the rainfall triggered a significant Lisse effect and decreased the slope factor of safety(F_(s)).When the rainfall intensity(R_(i))was higher than the saturated hydraulic conductivity(K_(s)),the Lisse effect and the F_(s) slightly changed with the increase of the R_(i),and the slope tended to be unstable with continuous rainfall.With increasing K_(s),the Lisse effect noticeably increased,and the minimum F_(s) quickly decreases.The analysis of the normalized sensitivity coefficient revealed that H_(0) had a dramatic impact on the Lisse effect and loess slope stability.The different R_(i) and K_(s) values had prominent influences on the Lisse effect and slight impacts on F_(s).
基金financially supported by the National Natural Science Foundation of China(Nos.52173277 and 21808189)the Key Science and Technology Foundation of Gansu Province,China(No.20YF3GA021)the Natural Science Foundation of Gansu Province,China(No.20JR5RA523).
文摘The cobalt-carbonate(CoCi)/NiFeOOH double-layer co-catalyst was prepared on bismuth vanadate(BiVO_(4)).Compared with the same type of electrode(Co-Pi/NiFeOOH/BiVO_(4) and Co-Sil/NiFeOOH/BiVO_(4)),the photoelectrochemical(PEC)performance of the composite electrode presents the most excellent performance.The Co-Ci/NiFeOOH/BiVO_(4) electrode prepared by photoelectric deposition(PED)achieves a photocurrent density of 4.1 mA/cm^(2) at 1.23 V vs RHE,and the applied bias photon-current efficiency(ABPE)is up to 0.95%.In addition,with the help of the equivalent circuit fitting in electrochemical impedance spectroscopy(EIS),the charge transfer resistance(R_(ct))of Co-Ci/NiFeOOH/BiVO_(4) is only 108.9Ω,which is 16%that of BiVO_(4).The enhanced PEC performance of Co-Ci/NiFeOOH/BiVO_(4) in the double-layer cocatalyst system is attributed to the outstanding advantages of Co-Ci cocatalyst in oxygen vacancy defects,superior to other cobalt-based catalysts in promoting charge transfer and improving the kinetics of water oxidation.This makes Co-Ci co-catalyst become one of the favorable competitors in the field of photoelectric catalysis.
基金financially supported by the National key research and development program (2017YFD0800502)the National Natural Science Foundation of China (Grant Nos. 41573067, 41790444, 41471189, 31700414)
文摘Soil nitrogen(N) is critical to ecosystem services and environmental quality. Hotspots of soil N in areas with high soil moisture have been widely studied, however, their spatial distribution and their linkage with soil N variation have seldom been examined at a catchment scale in areas with low soil water content. We investigated the spatial variation of soil N and its hotspots in a mixed land cover catchment on the Chinese Loess Plateau and used multiple statistical methods to evaluate the effects of the critical environmental factors on soil N variation and potential hotspots. The results demonstrated that land cover, soil moisture, elevation, plan curvature and flow accumulation were the dominant factors affecting the spatial variation of soil nitrate(NN), while land cover and slope aspect were the most important factors impacting the spatial distribution of soil ammonium(AN) and total nitrogen(TN). In the studied catchment, the forestland, gully land and grassland were found to be the potential hotspots of soil NN, AN and TN accumulation, respectively. We concluded that land cover and slope aspect could be proxies to determine the potential hotspots of soil N at the catchment scale. Overall, land cover was the most important factor that resulted in the spatial variations of soil N. The findings may help us to better understand the environmental factors affecting soil N hotspots and their spatial variation at the catchment scale in terrestrial ecosystems.
基金supported by the National Natural Science Foundation of China(42107351)China Postdoctoral Science Foundation(2019M663917XB)+2 种基金Natural Science Fund of Shaanxi Province(2021JQ-227)Fundamental Research Funds for the Central Universities,CHD(300102291104 and 300102291507)Programme of Introducing Talents of Discipline to Universities(B08039).
文摘An accurate prediction of peak discharge in watersheds is critical not only for water resource manage-ment,but also for understanding the complex relationships of hydrological processes.In this study,a modified peak discharge formula based on the Chemicals,Runoff,and Erosion from Agricultural Man-agement Systems(CREAMS)model was developed by introducing rainfall intensity and soil moisture factors.The reliability of the proposed method was tested with data from 1464 storm events in 41 watersheds and was applied to 256 storm events in five remaining typical watersheds using the opti-mized parameters.The results indicate that the proposed method is highly accurate in terms of model efficiency,as determined by Nash-Sutcliffe efficiencies(NSEs)of 88.60%,74.04%,and 90.12%during the calibration,validation,and application cases,respectively.Furthermore,it performed better than the original and modified CREAMS methods.Subsequently,using the parameters derived from the initial 41 watersheds and the runoff estimated using the modified Soil Conservation Service curve number(SCS-CN)method,the proposed method was used to predict the peak discharge from the last five typical watersheds.Large NSE(63.88-80.83%)and low root mean square error(RMSE)values(0.31-35.93 m^(3)s^(-1))were obtained for the five watersheds.Overall,the proposed peak discharge model,combined with the modified SCS-CN method,may accurately predict event-based peak discharge and runoff for general applications under various hydrological and geomorphic conditions in the Loess Plateau region.
