Groundwater is the main water supply source in the Tarim Basin in China.Endemic disease caused by high iodine(I)groundwater in the Tarim Basin was reported previously.Therefore,it is crucial to systematically identify...Groundwater is the main water supply source in the Tarim Basin in China.Endemic disease caused by high iodine(I)groundwater in the Tarim Basin was reported previously.Therefore,it is crucial to systematically identify the distribution and genesis of groundwater I.Based on hydrochemical analysis of 717 groundwater samples collected in 2015–2018,spatial distribution and hydrogeochemistry characteristic of high I groundwater in different aquifers were analyzed.Results showed that groundwater I ranged between<10.00 and 4000.00μg/L(mean of 53.71μg/L).High I groundwater(I>100.00μg/L)accounted for 7.25%of the total samples.Horizontally,groundwater I significantly increased from recharge zone(RZ)to transition zone(TZ)and to evaporation zone(EZ).Vertically,groundwater in shallow confined aquifer(SCA)had the greatest I concentration,followed by single-structure phreatic aquifer(SSPA),phreatic aquifer in confined groundwater area(PACGA),while groundwater in deep confined aquifer(DCA)generally had low I concentration.Groundwater I enrichment in SSPA was mainly affected by organic matter(OM)decomposition and that in SCA was mainly affected by evaporite mineral dissolution,OM decomposition under alkaline environment.While I enrichment in groundwater of PACGA was restrained under neutral environment.Lacustrine sedimentary environment was crucial for I enrichment in groundwater.Besides,fine-grained lithology of aquifer,smooth topographic slope,shallow buried depth of groundwater,weak alkaline and reducing environment,reductive dissolution of iron oxide/hydroxide minerals and OM decomposition were advantageous to I enrichment in groundwater.展开更多
Tamarix spp. （Saltcedar） is a facultative phreatophyte that can tolerate drought when groundwater is not accessed. In addition to deep water uptake, hydraulic redistribution （HR） is another factor contributing to ...Tamarix spp. （Saltcedar） is a facultative phreatophyte that can tolerate drought when groundwater is not accessed. In addition to deep water uptake, hydraulic redistribution （HR） is another factor contributing to the drought tolerance of Tarnarix spp. In this study, data on soil volumetric moisture content （0）, lateral root sap flow, and relevant climate variables were used to investigate the patterns, magnitude, and controlling factors of HR of soil water by roots of Tamarix ramosissima Ledeb. in an extremely arid land in Northwest China. Results showed evident diurnal fluctuations in 0 at the depths of 30 and 50 cm, indicating ＂hydraulic lift＂ （HL）. 0 increased remarkably at 10 and 140 cm but decreased at 30 and 50 cm and slightly changed at 80 cm after rainfall, suggesting a possible ＂hydraulic descent＂ （HD）. However, no direct evidence was observed in the negative flow of lateral roots, supporting HR （including HL and HD） of T. ramosissima. The HR pathway unlikely occurred via lateral roots; instead, HR possibly occurred through adventitious roots with a diameter of 2-5 mm and a length of 60-100 cm. HR at depths of 20-60 cm ranged from 0.01-1.77 mm/d with an average of 0.43 mm/d, which accounted for an average of 22% of the estimated seasonal total water depletion at 0-160 cm during the growing season. The climate factors, particularly vapor pressure deficit and soil water potential gradient, accounted for at least 33% and 45% of HR variations with depths and years, respectively. In summary, T. ramosissima can be added to the wide list of existing species involved in HR. High levels of HR may represent a considerable fraction of daily soil water depletion and substantially improve plant water status. HR could vary tremendously in terms of years and depths, and this variation could be attributed to climate factors and soil water potential gradient.展开更多
In this study, a magnetic micro-particle conditioning–pressurized vertical electro-osmotic dewatering（MPEOD） process with magnetic micro-particle conditioning–drainage under gravity–mechanical compression–electr...In this study, a magnetic micro-particle conditioning–pressurized vertical electro-osmotic dewatering（MPEOD） process with magnetic micro-particle conditioning–drainage under gravity–mechanical compression–electrical compression（MMPC–DG–MC–EC） stages was established to study the distribution and migration of water, extracellular polymeric substances（EPS）, and other organic matter in the activated sludge（AS） matrix at each stage.Results showed that the MPEOD process could attain 53.52% water content（WC） in dewatered AS with bound water（BW） and free water（FW） reduction rates of 82.97% and 99.67%,respectively. The coagulation and time-delayed magnetic field effects of magnetic microparticles（MMPs） along the MMPC–DG–MC stages initiated the transformation of partial BW to FW in AS. EC had a coupling driving effect of electro-osmosis and pressure on BW, and the changes in pH and temperature at EC stage induced the aggregation of AS flocs and the release of partial BW. Additionally, MMPs dosing further improved the dewatering performance of AS by acting as skeleton builders to provide water passages. Meanwhile, MMPs could disintegrate sludge cells and EPS fractions, thereby reducing tryptophan-like protein and byproduct-like material concentrations in LB-EPS as well as protein/polysaccharide ratio in AS matrix, which could improve AS filterability. At EC stage, the former four Ex/Em regions of fluorescence regional integration analysis for EPS were obviously reduced, especially the protein-like substances in LB-and TB-EPS, which contributed to improvement of AS dewaterability.展开更多
Water and energy are closely linked natural resources - the transportation, treatment, and distribution of water depends on low-cost energy; while power generation requires large volumes of water. Seawater desalinatio...Water and energy are closely linked natural resources - the transportation, treatment, and distribution of water depends on low-cost energy; while power generation requires large volumes of water. Seawater desalination is a mature technology for increasing freshwater supply, but it is essentially a trade of energy for freshwater and is not a viable solution for regions where both water and energy are in short supply. This paper discusses the development and application of a renewable-energy-driven reverse osmosis （RO） system for water desalination and the treatment and reuse of aquaculture wastewater. The system consists of （1） a wind-driven pumping subsystem, （2） a pressure-driven RO membrane desalination subsystem, and （3） a solar-driven feedback control module. The results of the pilot experiments indicated that the system, operated under wind speeds of 3 m s-~ or higher, can be used for brackish water desalination by reducing the salinity of feedwater with total dissolved solids （TDS） of over 3 000 mg L-1 to product water or permeate with a TDS of 200 mg L-~ or less. Results of the pilot experiments also indicated that the system can remove up to 97% of the nitrogenous wastes from the fish pond effluent and can recover and reuse up to 56% of the freshwater supply for fish pond operation.展开更多
Understanding forest ecosystem evapotranspiration（ET） is crucial for water-limited environments,particularly those that lack adequate quantified data such as the lower Heihe River basin of northwest China which is p...Understanding forest ecosystem evapotranspiration（ET） is crucial for water-limited environments,particularly those that lack adequate quantified data such as the lower Heihe River basin of northwest China which is primarily dominated by Tamarix ramosissima Ledeb.and Populus euphratica Oliv.forests.Accordingly,we selected the growing season for 2 years （2012 and 2014） of two such forests under similar meteorological conditions to compare ET using the eddy covariance（EC） technique.During the growing seasons,daily ET of T.ramosissima ranged from 0.3 to 8.0 mm day^（-1） with a mean of 3.6 mm day^（-1）,and daily ET of P.euphratica ranged from 0.9 to 7.9 mm day^（-1） with a mean of 4.6 mm day^（-1） for a total of 548 and 707 mm,respectively.The significantly higher ET of the P.euphratica stand was directly linked to high soil evaporation rates under sufficient water availability from irrigation.When the soil evaporation was disregarded,water use was comparable to two contrasting riparian forests,a P.euphratica forest with a total transpiration of 465 mm and a T.ramosissima forest with 473 mm.Regression analysis demonstrated that climate factors accounted for at least 80% of ET variation in both forest types.In conclusion,water use of the riparian forests was low and comparable in this arid region,that suggest the long-term plant adaptation to the local climate and conditions of water availability.展开更多
Recreational waters contaminated with human fecal pollution are a public health concern, and ensuring the safety of recreational waters for public use is a priority of both the Environmental Protection Agency(EPA) and...Recreational waters contaminated with human fecal pollution are a public health concern, and ensuring the safety of recreational waters for public use is a priority of both the Environmental Protection Agency(EPA) and the Centers for Disease Control and Prevention(CDC). Current recreational water standards rely on fecal indicator bacteria(FIB) levels as indicators of human disease risk. However present evidence indicates that levels of FIB do not always correspond to the presence of other potentially harmful organisms, such as viruses. Thus, enteric viruses are currently tested as water quality indicators, but have yet to be successfully implemented in routine monitoring of water quality. This study utilized enteric viruses as possible alternative indicators of water quality to examine 18 different fresh and offshore recreational waters on O‘ahu, Hawai‘i, by using newly established laboratory techniques including highly optimized PCR, real time PCR, and viral infectivity assays. All sample sites were detected positive for human enteric viruses by PCR including enterovirus, norovirus genogroups I and II, and male specific FRNA coliphage. A six time-point seasonal study of enteric virus presence indicated significant variation in virus detection between the rainy and dry seasons. Quantitative PCR detected the presence of norovirus genogroup II at levels at which disease risk may occur, and there was no correlation found between enteric virus presence and FIB counts. Under the present laboratory conditions, no infectious viruses were detected from the samples PCR-positive for enteric viruses. These data emphasize both the need for additional indicators for improved monitoring of water quality, and the feasibility of using enteric viruses as these indicators.展开更多
Significant fractions of bromine-substituted disinfection byproducts (DBPs)—particularly trihalomethanes (THMs)— have been observed to form during treatment of water from the Missouri River. THM speciation was also ...Significant fractions of bromine-substituted disinfection byproducts (DBPs)—particularly trihalomethanes (THMs)— have been observed to form during treatment of water from the Missouri River. THM speciation was also noted to follow a seasonal pattern during a 2.5-year period, during which samples were collected multiple times per month. Although some treatment processes were effective at reducing the chloroform formation potential, no treatment used at this utility significantly reduced the formation of the three bromine-substituted THM species. Using chloramination rather than free chlorination for secondary disinfection, however, was effective at limiting increases in the concentration of all four regulated THM species in the distribution system.展开更多
The hydrological study in the upstream of the Huai Khot Wang Man diversion canal in Huai Khun Kaew watershed of the Upper Tha Chin River Basin in Uthai Thani Province, Thailand was studied. The soil and water assessme...The hydrological study in the upstream of the Huai Khot Wang Man diversion canal in Huai Khun Kaew watershed of the Upper Tha Chin River Basin in Uthai Thani Province, Thailand was studied. The soil and water assessment tool (SWAT) and the integrated flood analysis systems (IFAS) applied to the analysis of flow at the outlet. The global weather data provided automatically by the models including land use covers and soil types. The climate forecast system reanalysis (CFSR) and the near real-time precipitation (GSMaP_NRT) used in SWAT and IFAS, respectively. The model sensitivity with Nash and Sutcliffe efficiency (NSE), correlation (R2), and root mean square error (RSME) were applied. The monthly calibrated results from SWAT fitted to the observed data in 2007-2010 with 0.77, 0.88, and 9.08 m3/s, and verified in 2011 with 0.25, 0.61, and 14.30 m3/s, respectively. The daily results from IFAS during a flood period in 2011 fitted to the observed data with 0.21, 0.39, and 34.32 m3/s. Both models showed applicable for efficient gate operation of the diversion canal from this watershed to the Nong Mamong District in Chai Nat Province.展开更多
Anthropogenically induced land use/land cover(LULC)transformations and accelerating climatic variabilities have emerged as pivotal forces reshaping the hydrological equilibrium of fluvial systems,particularly in ecolo...Anthropogenically induced land use/land cover(LULC)transformations and accelerating climatic variabilities have emerged as pivotal forces reshaping the hydrological equilibrium of fluvial systems,particularly in ecologically sensitive basins.This study systematically interrogates the compounded ramifications of LULC dynamics and projected climate change on the hydrological response of the Upper Jemma Watershed an integral sub-catchment of the Upper Blue Nile River system.Employing the advanced QSWAT+hydrological modeling framework within a GIS interface,the analysis integrates bias‐corrected climatic projections under RCP 4.5 and RCP 8.5 scenarios alongside multi-temporal remote sensing‐derived land cover datasets.The findings unveil an unequivocal intensification of surface runoff and streamflow due to expansive agricultural encroachment,juxtaposed with a discernible decline in evapotranspiration and soil water retention.Climatic perturbations,notably temperature elevation and precipitation attenuation,further exacerbate these trends,with pronounced seasonality in hydrological fluxes.Importantly,synergistic interactions between land cover transformation and climatic anomalies manifest in nonlinear hydrological alterations,amplifying peak flows and diminishing baseflows.This underscores the riverine system's heightened vulnerability and the necessity for integrated watershed management strategies that account for multifactorial hydrological stressors.The study provides a robust empirical and modeling basis to inform adaptive water governance within transboundary river basins susceptible to environmental transitions.展开更多
Coastal wetlands are crucial for the‘blue carbon sink’,significantly contributing to regulating climate change.This study util-ized 160 soil samples,35 remote sensing features,and 5 geo-climatic data to accurately e...Coastal wetlands are crucial for the‘blue carbon sink’,significantly contributing to regulating climate change.This study util-ized 160 soil samples,35 remote sensing features,and 5 geo-climatic data to accurately estimate the soil organic carbon stocks(SOCS)in the coastal wetlands of Tianjin and Hebei,China.To reduce data redundancy,simplify model complexity,and improve model inter-pretability,Pearson correlation analysis(PsCA),Boruta,and recursive feature elimination(RFE)were employed to optimize features.Combined with the optimized features,the soil organic carbon density(SOCD)prediction model was constructed by using multivariate adaptive regression splines(MARS),extreme gradient boosting(XGBoost),and random forest(RF)algorithms and applied to predict the spatial distribution of SOCD and estimate the SOCS of different wetland types in 2020.The results show that:1)different feature combinations have a significant influence on the model performance.Better prediction performance was attained by building a model using RFE-based feature combinations.RF has the best prediction accuracy(R^(2)=0.587,RMSE=0.798 kg/m^(2),MAE=0.660 kg/m^(2)).2)Optical features are more important than radar and geo-climatic features in the MARS,XGBoost,and RF algorithms.3)The size of SOCS is related to SOCD and the area of each wetland type,aquaculture pond has the highest SOCS,followed by marsh,salt pan,mud-flat,and sand shore.展开更多
In response to the severe flood control challenges in the Taihu Lake Basin,this study focuses on the coordinated operation of newly constructed projects-such as the Xinmeng River and Xingou River-and the existing wate...In response to the severe flood control challenges in the Taihu Lake Basin,this study focuses on the coordinated operation of newly constructed projects-such as the Xinmeng River and Xingou River-and the existing water conservancy system.Addressing the drainage difficulties in the upstream Huxi Area and the Wucheng-Xixi-Yuxi Area,the research adopts a technical framework of"scenario-driven analysis-scheme simulation-multi-objective decision-making."Through simulation and optimization based on mathematical models and an intelligent decision-support system,an operationally feasible joint operation scheme is proposed.The results demonstrate that optimized joint operation can significantly unleash the flood control potential of water conservancy projects,providing valuable methodological insights and a practical reference for coordinated operation and intelligent decision-making in complex river network regions.展开更多
Variations and trends in extreme climate events are more sensitive to climate change than the mean values,and so have received much attention.In this study,twelve indices of temperature extremes and 11 indices of prec...Variations and trends in extreme climate events are more sensitive to climate change than the mean values,and so have received much attention.In this study,twelve indices of temperature extremes and 11 indices of precipita-tion extremes at 32 meteorological stations in Hengduan Mountains were examined for the period 1961-2008.The re-suits reveal statistically significant increases in the temperature of the warmest and coldest nights and in the frequen-cies of extreme warm days and nights.Decreases of the diurnal temperature range and the numbers of frost days and ice days are statistically significant.Regional averages of growing season length also display the trends consistent and significant with warming.At a large proportion of the stations,patterns of temperature extremes are consistent with warming since 1961:warming trends in minimum temperature indices are greater than those relating to maximum temperature.As the center of the Shaluli Mountain,the warming magnitudes decrease from inner to outer.Changes in precipitation extremes is low:trends are difficult to detect against the larger inter-annual and decadal-scale variability of precipitation,and only the wet day precipitation and the regional trend in consecutive dry days are significant at the 0.05 level.It can be concluded that the variation of extreme precipitation events is not obvious in the Hengduan Mountains,however,the regional trends generally decrease from the south to the north.Overall,the spatial distribution of temporal changes of all extreme climate indices in the Hengduan Mountains illustrated here reflects the climatic complexity in mountainous regions.展开更多
Evapotranspiration (ET) within an ecosystem is crucial for die water-limited environment that currently lacks adequate quantification in the arid region of Northwest China, mainly covered by phreatophytes, such as the...Evapotranspiration (ET) within an ecosystem is crucial for die water-limited environment that currently lacks adequate quantification in the arid region of Northwest China, mainly covered by phreatophytes, such as the Populus euphratica Oliv. tree and the Tamarix ramosissima Ledeb. shrub species. Accordingly. ET was measured for an entire year using eddy covariance (EC) in P. euphratica stands in the lower Heihe River Basin, Northwest China. During the growing season, the total ET was 850 mm, with a mean of 4.0 mm/d, Which is obviously more than that observed at tree-level and stand level scales, which was likely due to the different level of soil evaporation induced by irrigation via water conveyance. Factors associated with ET fall into either environmental or plant eco-physiological categories. Environmental factors account for at least 79% variation of ET and the linear relationship between ET and the voundwater table (GWT) revealed the potential water use of P. euphratica forests under the non-water stress condition with die GWT less than 3 m deep. Plant eco-physiological parameters, specifically die leaf area 'index (LAI), have direct impact on the seasonal pattern of ET which provides a valuable reference to the wide-area estimates of ET for riparian forests by using LAI. In conclusion, P. euphratica forests have high water use after water conveyance, which may be the result of long-term adapting to local climates and limited water availability.展开更多
The sub-cloud evaporation effect refers to the evaporation process for raindrops that fall from the cloud base to the ground, which is usually accompanied by depleted light isotopes and enriched heavy isotopes in the ...The sub-cloud evaporation effect refers to the evaporation process for raindrops that fall from the cloud base to the ground, which is usually accompanied by depleted light isotopes and enriched heavy isotopes in the precipitation. Based on 461 event-based precipitation samples collected from 12 weather stations in the Qilian Mountains and the Hexi Corridor from May to August of 2013, our results indicated that sub-cloud evaporation has a great influence on the δ^18O of precipitation, especially in small-amount precipitation events. In May, June, July, and August the δ18O composition was enriched by 35%, 26%, 39%, and 41%, respectively, from the cloud base to the ground. This influence clearly strengthened with temperature rise, from the Qilian Mountains to the Hexi Corridor. When falling raindrops are evaporated by 1.0% in the Qilian Mountains and the Hexi Corridor, the composition of δ18O would be enriched by 1.2% and 2.6%, respectively. Temperature dominated the sub-cloud evaporation in the Qilian Mountains, whereas relative humidity controlled it in the Hexi Corridor. These results provide new proofs of the evolutional process of stable isotopes in precipitation in arid regions.展开更多
Studying the response to warming of hydrological systems in Chin＇s temperate glacier region is essential in order to provide information required for sustainable develop- ment. The results indicated the warming clima...Studying the response to warming of hydrological systems in Chin＇s temperate glacier region is essential in order to provide information required for sustainable develop- ment. The results indicated the warming climate has had an impact on the hydrological cycle. As the glacier area subject to melting has increased and the ablation seasor has become longer, the contribution of meltwater to annual river discharge has increased. The earlier onset of ablation at higher elevation glaciers has resulted in the period of minimum discharge occurring earlier in the year. Seasonal runoff variations are dominated by snow and glacier melt, and an increase of meltwater has resulted in changes of the annual water cycle in the Lijiang Basin and Hailuogou Basin. The increase amplitude of runoff in the downstream re- gion of the glacial area is much stronger than that of precipitation, resulting from the promi- nent increase of meltwater from glacier region in two basins. Continued observations in the glacierized basins should be undertaken in order to monitor changes, to reveal the relation- ships between climate, glaciers, hydrology and water supplies, and to assist in maintaining sustainable regional development.展开更多
This research was conducted in the upstream watershed of the Mae Yom Irrigation Project, which was located in the Upper Yom River Basin in Phrae Province, Thailand. The most common troublesome in this area is flood an...This research was conducted in the upstream watershed of the Mae Yom Irrigation Project, which was located in the Upper Yom River Basin in Phrae Province, Thailand. The most common troublesome in this area is flood and drought and leads to poor water management by difficult river flow forecasting to an existing large weir without upstream dam. The Soil And Water Assessment Tool (SWAT) model was applied for the simulation of the hydrological system and predicting the daily river flow to the upstream weir during flood season in 2006 and 2011 as for simulating and comparing with observed data. The results were fitted to the observed data with Nash and Sutcliffe efficiency (NSE) of ?0.65, and root mean square error (RSME) of 228.0 whereas the mean inflow discharge during wet season in both years was 173.3 cubic meters per second, respectively.展开更多
Precipitation chemistry analysis is essential to evaluate the atmospheric environmental quality and identify the sources of atmospheric pollutants. In this study, we collected a total of 480 precipitation samples at 6...Precipitation chemistry analysis is essential to evaluate the atmospheric environmental quality and identify the sources of atmospheric pollutants. In this study, we collected a total of 480 precipitation samples at 6 sampling sites in the northern and southern slopes of Wushaoling Mountain from May 2013 to July 2014 to analyze the chemical characteristics of precipitation and to identify the main sources of ions in precipitation. Furthermore, we also explored the indicative significance for sand dust events in the northern and southern slopes of Wushaoling Mountain based on the precipitation chemistry analysis.During the sampling period（from May 2013 to July 2014）, the p H values, EC（electrical conductivity）values and concentrations of cations（Ca^（2＋）, Mg^（2＋）, Na~＋, K~＋ and NH_4~＋） and anions（SO_4^（2–）, NO_3~–, Cl~–, NO_2~– and F~–） in precipitation were different in the northern and southern slopes at daily and seasonal time scales, with most of the values being higher in the northern slope than in the southern slope. The chemical type of precipitation in the southern and northern slopes was the same, i.e.,SO_4^（2–）-Ca^（2＋）-NO_3~–-Na~＋. The concentrations of ions in precipitation were mainly controlled by terrigenous material and anthropogenic activities（with an exception of Cl~–）. The concentration of Cl~– in precipitation was mainly controlled by the sea salt fraction. The concentrations of Na＋ and Cl~– showed an increasing trend after the occurrence of sand dust events both in the northern and southern slopes. In addition, after the occurrence of sand dust events, the concentrations of K~＋, Mg^（2＋）, SO_4^（2–）, NO_3~– and Ca^（2＋） showed an increasing trend in the southern slope and a decreasing trend in the northern slope. It is our hope that the results may be helpful to further understand the atmospheric pollution caused by sand dust events in the Wushaoling Mountain and can also provide a scientific basis for the effective prevention of atmospheric pollution.展开更多
To increase dynamic stability of the quadrotor unmanned aerial vehicles in varying mechanical structure. The qualitative analysis is considered the main methods for analyzing the dynamic stability, while the index of ...To increase dynamic stability of the quadrotor unmanned aerial vehicles in varying mechanical structure. The qualitative analysis is considered the main methods for analyzing the dynamic stability, while the index of qualitative analysis of the structural stability and the dynamic stability are still hard to establish. Therefore, the process during rolling or pitching is selected for investigating in the present papers, the method of Lyapunov exponent is adopted for establishing the quantification relationship of between structural parameters of quadrotor unmanned aerial vehicles and dynamic stability, and its dynamic stability for guiding the design of the vehicle′s mechanical structure and the optimization of its stability control by using the relationship. As compared to its counterpart of Lyapunov′s second method, the main advantage of the concept of Lyapunov exponents is that the methods for calculating the exponent process are constructive which makes the stability analysis of complex nonlinear systems possible.展开更多
Global climate change has been evident in many places worldwide. This study provxdes a better understanding of the variability and changes in frequency, intensity, and duration of temperature, precipitation, and clima...Global climate change has been evident in many places worldwide. This study provxdes a better understanding of the variability and changes in frequency, intensity, and duration of temperature, precipitation, and climate extremes in the Extensive Hexi Region, based on meteorological data from 26 stations. The analysis of average, maximum, and minimum temperatures revealed that statistically significant warming occurred from 1960 to 2011. All temperature extremes dis- played trends consistent with warming, with the exception of coldest-night temperature （TNn） and coldest-day tempera- ture （TXn）, which were particularly evident in high-altitude areas and at night. Amount of precipitation and number of rainy days slowly increased with no significant regional trends, mainly occurring in the Qilian Mountains and Hexi Cor- ridor. The significance of changes in precipitation extremes during 1960-2011 was high, hut the regional trends of max- imum 5-day precipitation （RX5day）, the average precipitation on wet days （SDII）, and consecutive wet days （CWD） were not significant. The variations in the studied parameters indicate an increase in both the extremity and strength of precip- itation events, particularly in higher-altitude regions. Furthermore, the contribution from very wet precipitation （R95） and extremely wet precipitation （R99） to total precipitation also increased between 1960 and 2011. The assessment of these changes in temperature and precipitation may help in developing better management practices for water resources. Future studies in the region should focus on the impact of these changes on runoffs and glaciers.展开更多
Hydrological circulation,as the most basic material cycle and active natural phenomenon on earth,exerts a significant in fluence on climate change.The mid-Holocene is an important period to better understand modern en...Hydrological circulation,as the most basic material cycle and active natural phenomenon on earth,exerts a significant in fluence on climate change.The mid-Holocene is an important period to better understand modern environmental change;however,little research has focused on its quantitative simulation of paleo-hydrological process.In this research,we first collected chronological evidence and sediment records from six Holocene sedimentary sections in the Shiyang River Ba sin to reconstruct the mid-Holocene environment and terminal paleo-lake area.Secondly,we comprehensively analyzed modern pollen combinations and their propagation characteristics in surface soil,air,river and lacustrine sediments in the Shiyang River Basin,and combined the pollen records,as well as quantitatively reconstructed the millennial-scale vegeta tion zones.Finally,based on the land-cover adjustment results during the mid-Holocene,we successfully used the Soil and Water Assessment Tool(SWAT)model,a modern distributed hydrological watershed model,to simulate mid-Holocene runoff in the basin.Results show that the reconstructed climate in the basin was warmer and moister than that in recent times.Vegetation types in the mid-Holocene mainly consisted of sub-alpine shrub distributed between 2,550 m and 2,750 m,forest at an elevation of 2,550 2,750 m,steppe at an elevation of 1,550 2,150 m and desert steppe below 1,550 m.The up stream,midstream,downstream and average annual runoff of the mid-Holocene in the basin were 16.76×10^8 m^3,22.86×10^8 m^3,9.00×10^8 m^3 and 16.20×10^8 m^3 respectively,compared to 15.61×10^8 m^3 of modern annual runoff.Also,the area of terminal paleo-lake in the mid-Holocene was 628 km^2.Thus,this study provides a new quantitative method for paleo-hy drological simulation.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.42067035 and 42007161)Water Conservancy Engineering Key Discipline Project of Xinjiang Agricultural University(No.SLXK2019-10)the Opening Project of Xinjiang Key Laboratory of Hydraulic Engineering Security and Water Disasters Prevention in 2021(No.ZDSYS-JS-2021-10)。
文摘Groundwater is the main water supply source in the Tarim Basin in China.Endemic disease caused by high iodine(I)groundwater in the Tarim Basin was reported previously.Therefore,it is crucial to systematically identify the distribution and genesis of groundwater I.Based on hydrochemical analysis of 717 groundwater samples collected in 2015–2018,spatial distribution and hydrogeochemistry characteristic of high I groundwater in different aquifers were analyzed.Results showed that groundwater I ranged between<10.00 and 4000.00μg/L(mean of 53.71μg/L).High I groundwater(I>100.00μg/L)accounted for 7.25%of the total samples.Horizontally,groundwater I significantly increased from recharge zone(RZ)to transition zone(TZ)and to evaporation zone(EZ).Vertically,groundwater in shallow confined aquifer(SCA)had the greatest I concentration,followed by single-structure phreatic aquifer(SSPA),phreatic aquifer in confined groundwater area(PACGA),while groundwater in deep confined aquifer(DCA)generally had low I concentration.Groundwater I enrichment in SSPA was mainly affected by organic matter(OM)decomposition and that in SCA was mainly affected by evaporite mineral dissolution,OM decomposition under alkaline environment.While I enrichment in groundwater of PACGA was restrained under neutral environment.Lacustrine sedimentary environment was crucial for I enrichment in groundwater.Besides,fine-grained lithology of aquifer,smooth topographic slope,shallow buried depth of groundwater,weak alkaline and reducing environment,reductive dissolution of iron oxide/hydroxide minerals and OM decomposition were advantageous to I enrichment in groundwater.
基金supported by the Key Project of the Chinese Academy of Sciences (KZZD-EW-04-05)the National Natural Science Foundation of China (91025024)the Western Light Project of the Chinese Academy of Sciences
文摘Tamarix spp. （Saltcedar） is a facultative phreatophyte that can tolerate drought when groundwater is not accessed. In addition to deep water uptake, hydraulic redistribution （HR） is another factor contributing to the drought tolerance of Tarnarix spp. In this study, data on soil volumetric moisture content （0）, lateral root sap flow, and relevant climate variables were used to investigate the patterns, magnitude, and controlling factors of HR of soil water by roots of Tamarix ramosissima Ledeb. in an extremely arid land in Northwest China. Results showed evident diurnal fluctuations in 0 at the depths of 30 and 50 cm, indicating ＂hydraulic lift＂ （HL）. 0 increased remarkably at 10 and 140 cm but decreased at 30 and 50 cm and slightly changed at 80 cm after rainfall, suggesting a possible ＂hydraulic descent＂ （HD）. However, no direct evidence was observed in the negative flow of lateral roots, supporting HR （including HL and HD） of T. ramosissima. The HR pathway unlikely occurred via lateral roots; instead, HR possibly occurred through adventitious roots with a diameter of 2-5 mm and a length of 60-100 cm. HR at depths of 20-60 cm ranged from 0.01-1.77 mm/d with an average of 0.43 mm/d, which accounted for an average of 22% of the estimated seasonal total water depletion at 0-160 cm during the growing season. The climate factors, particularly vapor pressure deficit and soil water potential gradient, accounted for at least 33% and 45% of HR variations with depths and years, respectively. In summary, T. ramosissima can be added to the wide list of existing species involved in HR. High levels of HR may represent a considerable fraction of daily soil water depletion and substantially improve plant water status. HR could vary tremendously in terms of years and depths, and this variation could be attributed to climate factors and soil water potential gradient.
基金supported by the National Natural Science Foundation of China(Nos.51478041,51678053)Major Projects on Control and Rectification of Water Body Pollution(Nos.2012ZX07105-002-03,2013ZX07202-010)
文摘In this study, a magnetic micro-particle conditioning–pressurized vertical electro-osmotic dewatering（MPEOD） process with magnetic micro-particle conditioning–drainage under gravity–mechanical compression–electrical compression（MMPC–DG–MC–EC） stages was established to study the distribution and migration of water, extracellular polymeric substances（EPS）, and other organic matter in the activated sludge（AS） matrix at each stage.Results showed that the MPEOD process could attain 53.52% water content（WC） in dewatered AS with bound water（BW） and free water（FW） reduction rates of 82.97% and 99.67%,respectively. The coagulation and time-delayed magnetic field effects of magnetic microparticles（MMPs） along the MMPC–DG–MC stages initiated the transformation of partial BW to FW in AS. EC had a coupling driving effect of electro-osmosis and pressure on BW, and the changes in pH and temperature at EC stage induced the aggregation of AS flocs and the release of partial BW. Additionally, MMPs dosing further improved the dewatering performance of AS by acting as skeleton builders to provide water passages. Meanwhile, MMPs could disintegrate sludge cells and EPS fractions, thereby reducing tryptophan-like protein and byproduct-like material concentrations in LB-EPS as well as protein/polysaccharide ratio in AS matrix, which could improve AS filterability. At EC stage, the former four Ex/Em regions of fluorescence regional integration analysis for EPS were obviously reduced, especially the protein-like substances in LB-and TB-EPS, which contributed to improvement of AS dewaterability.
基金supported in part by the U.S.Department of the Interior Bureau of Reclamation(USBR)through a research grant(04-FG-81-1062)
文摘Water and energy are closely linked natural resources - the transportation, treatment, and distribution of water depends on low-cost energy; while power generation requires large volumes of water. Seawater desalination is a mature technology for increasing freshwater supply, but it is essentially a trade of energy for freshwater and is not a viable solution for regions where both water and energy are in short supply. This paper discusses the development and application of a renewable-energy-driven reverse osmosis （RO） system for water desalination and the treatment and reuse of aquaculture wastewater. The system consists of （1） a wind-driven pumping subsystem, （2） a pressure-driven RO membrane desalination subsystem, and （3） a solar-driven feedback control module. The results of the pilot experiments indicated that the system, operated under wind speeds of 3 m s-~ or higher, can be used for brackish water desalination by reducing the salinity of feedwater with total dissolved solids （TDS） of over 3 000 mg L-1 to product water or permeate with a TDS of 200 mg L-~ or less. Results of the pilot experiments also indicated that the system can remove up to 97% of the nitrogenous wastes from the fish pond effluent and can recover and reuse up to 56% of the freshwater supply for fish pond operation.
基金supported by the National Natural Science Foundation of China(41401033,31370466,and 41271037)the China Postdoctoral Science Foundation(2014M560819)the National Key Research and Development Program of China(2016YFC0501002)
文摘Understanding forest ecosystem evapotranspiration（ET） is crucial for water-limited environments,particularly those that lack adequate quantified data such as the lower Heihe River basin of northwest China which is primarily dominated by Tamarix ramosissima Ledeb.and Populus euphratica Oliv.forests.Accordingly,we selected the growing season for 2 years （2012 and 2014） of two such forests under similar meteorological conditions to compare ET using the eddy covariance（EC） technique.During the growing seasons,daily ET of T.ramosissima ranged from 0.3 to 8.0 mm day^（-1） with a mean of 3.6 mm day^（-1）,and daily ET of P.euphratica ranged from 0.9 to 7.9 mm day^（-1） with a mean of 4.6 mm day^（-1） for a total of 548 and 707 mm,respectively.The significantly higher ET of the P.euphratica stand was directly linked to high soil evaporation rates under sufficient water availability from irrigation.When the soil evaporation was disregarded,water use was comparable to two contrasting riparian forests,a P.euphratica forest with a total transpiration of 465 mm and a T.ramosissima forest with 473 mm.Regression analysis demonstrated that climate factors accounted for at least 80% of ET variation in both forest types.In conclusion,water use of the riparian forests was low and comparable in this arid region,that suggest the long-term plant adaptation to the local climate and conditions of water availability.
基金supported in part by grants from the Centers for Oceans and Human Health (COHH) programthe National Institutes of Environmental Health Sciences (P50ES012740)+1 种基金the National Science Foundation (OCE04-32479 and OCE09-11000)the Hawai‘i Community Foundation (11ADVC-49702)
文摘Recreational waters contaminated with human fecal pollution are a public health concern, and ensuring the safety of recreational waters for public use is a priority of both the Environmental Protection Agency(EPA) and the Centers for Disease Control and Prevention(CDC). Current recreational water standards rely on fecal indicator bacteria(FIB) levels as indicators of human disease risk. However present evidence indicates that levels of FIB do not always correspond to the presence of other potentially harmful organisms, such as viruses. Thus, enteric viruses are currently tested as water quality indicators, but have yet to be successfully implemented in routine monitoring of water quality. This study utilized enteric viruses as possible alternative indicators of water quality to examine 18 different fresh and offshore recreational waters on O‘ahu, Hawai‘i, by using newly established laboratory techniques including highly optimized PCR, real time PCR, and viral infectivity assays. All sample sites were detected positive for human enteric viruses by PCR including enterovirus, norovirus genogroups I and II, and male specific FRNA coliphage. A six time-point seasonal study of enteric virus presence indicated significant variation in virus detection between the rainy and dry seasons. Quantitative PCR detected the presence of norovirus genogroup II at levels at which disease risk may occur, and there was no correlation found between enteric virus presence and FIB counts. Under the present laboratory conditions, no infectious viruses were detected from the samples PCR-positive for enteric viruses. These data emphasize both the need for additional indicators for improved monitoring of water quality, and the feasibility of using enteric viruses as these indicators.
文摘Significant fractions of bromine-substituted disinfection byproducts (DBPs)—particularly trihalomethanes (THMs)— have been observed to form during treatment of water from the Missouri River. THM speciation was also noted to follow a seasonal pattern during a 2.5-year period, during which samples were collected multiple times per month. Although some treatment processes were effective at reducing the chloroform formation potential, no treatment used at this utility significantly reduced the formation of the three bromine-substituted THM species. Using chloramination rather than free chlorination for secondary disinfection, however, was effective at limiting increases in the concentration of all four regulated THM species in the distribution system.
文摘The hydrological study in the upstream of the Huai Khot Wang Man diversion canal in Huai Khun Kaew watershed of the Upper Tha Chin River Basin in Uthai Thani Province, Thailand was studied. The soil and water assessment tool (SWAT) and the integrated flood analysis systems (IFAS) applied to the analysis of flow at the outlet. The global weather data provided automatically by the models including land use covers and soil types. The climate forecast system reanalysis (CFSR) and the near real-time precipitation (GSMaP_NRT) used in SWAT and IFAS, respectively. The model sensitivity with Nash and Sutcliffe efficiency (NSE), correlation (R2), and root mean square error (RSME) were applied. The monthly calibrated results from SWAT fitted to the observed data in 2007-2010 with 0.77, 0.88, and 9.08 m3/s, and verified in 2011 with 0.25, 0.61, and 14.30 m3/s, respectively. The daily results from IFAS during a flood period in 2011 fitted to the observed data with 0.21, 0.39, and 34.32 m3/s. Both models showed applicable for efficient gate operation of the diversion canal from this watershed to the Nong Mamong District in Chai Nat Province.
文摘Anthropogenically induced land use/land cover(LULC)transformations and accelerating climatic variabilities have emerged as pivotal forces reshaping the hydrological equilibrium of fluvial systems,particularly in ecologically sensitive basins.This study systematically interrogates the compounded ramifications of LULC dynamics and projected climate change on the hydrological response of the Upper Jemma Watershed an integral sub-catchment of the Upper Blue Nile River system.Employing the advanced QSWAT+hydrological modeling framework within a GIS interface,the analysis integrates bias‐corrected climatic projections under RCP 4.5 and RCP 8.5 scenarios alongside multi-temporal remote sensing‐derived land cover datasets.The findings unveil an unequivocal intensification of surface runoff and streamflow due to expansive agricultural encroachment,juxtaposed with a discernible decline in evapotranspiration and soil water retention.Climatic perturbations,notably temperature elevation and precipitation attenuation,further exacerbate these trends,with pronounced seasonality in hydrological fluxes.Importantly,synergistic interactions between land cover transformation and climatic anomalies manifest in nonlinear hydrological alterations,amplifying peak flows and diminishing baseflows.This underscores the riverine system's heightened vulnerability and the necessity for integrated watershed management strategies that account for multifactorial hydrological stressors.The study provides a robust empirical and modeling basis to inform adaptive water governance within transboundary river basins susceptible to environmental transitions.
基金Under the auspices of National Natural Science Foundation of China(No.42101393,41901375,52274166)Hebei Natural Science Foundation(No.D2022209005,D2023209008)Central Guided Local Science and Technology Development Fund Project of Hebei Province(No.236Z3305G,246Z4201G)Key Research and Development Program of Science and Technology Plan of Tangshan,China(No.22150221J)。
文摘Coastal wetlands are crucial for the‘blue carbon sink’,significantly contributing to regulating climate change.This study util-ized 160 soil samples,35 remote sensing features,and 5 geo-climatic data to accurately estimate the soil organic carbon stocks(SOCS)in the coastal wetlands of Tianjin and Hebei,China.To reduce data redundancy,simplify model complexity,and improve model inter-pretability,Pearson correlation analysis(PsCA),Boruta,and recursive feature elimination(RFE)were employed to optimize features.Combined with the optimized features,the soil organic carbon density(SOCD)prediction model was constructed by using multivariate adaptive regression splines(MARS),extreme gradient boosting(XGBoost),and random forest(RF)algorithms and applied to predict the spatial distribution of SOCD and estimate the SOCS of different wetland types in 2020.The results show that:1)different feature combinations have a significant influence on the model performance.Better prediction performance was attained by building a model using RFE-based feature combinations.RF has the best prediction accuracy(R^(2)=0.587,RMSE=0.798 kg/m^(2),MAE=0.660 kg/m^(2)).2)Optical features are more important than radar and geo-climatic features in the MARS,XGBoost,and RF algorithms.3)The size of SOCS is related to SOCD and the area of each wetland type,aquaculture pond has the highest SOCS,followed by marsh,salt pan,mud-flat,and sand shore.
文摘In response to the severe flood control challenges in the Taihu Lake Basin,this study focuses on the coordinated operation of newly constructed projects-such as the Xinmeng River and Xingou River-and the existing water conservancy system.Addressing the drainage difficulties in the upstream Huxi Area and the Wucheng-Xixi-Yuxi Area,the research adopts a technical framework of"scenario-driven analysis-scheme simulation-multi-objective decision-making."Through simulation and optimization based on mathematical models and an intelligent decision-support system,an operationally feasible joint operation scheme is proposed.The results demonstrate that optimized joint operation can significantly unleash the flood control potential of water conservancy projects,providing valuable methodological insights and a practical reference for coordinated operation and intelligent decision-making in complex river network regions.
基金Under the auspices of West Light Foundation of Chinese Academy of Sciences(No.Y000141001)Key Program ofNational Natural Science Foundation of China(No.91025002)+1 种基金Program for Incubation of Specialists in Glaciology and Geocryology of National Natural Science Foundation of China(No.11J0930003)National Natural Science Foundation of China(No.40725001,30970492)
文摘Variations and trends in extreme climate events are more sensitive to climate change than the mean values,and so have received much attention.In this study,twelve indices of temperature extremes and 11 indices of precipita-tion extremes at 32 meteorological stations in Hengduan Mountains were examined for the period 1961-2008.The re-suits reveal statistically significant increases in the temperature of the warmest and coldest nights and in the frequen-cies of extreme warm days and nights.Decreases of the diurnal temperature range and the numbers of frost days and ice days are statistically significant.Regional averages of growing season length also display the trends consistent and significant with warming.At a large proportion of the stations,patterns of temperature extremes are consistent with warming since 1961:warming trends in minimum temperature indices are greater than those relating to maximum temperature.As the center of the Shaluli Mountain,the warming magnitudes decrease from inner to outer.Changes in precipitation extremes is low:trends are difficult to detect against the larger inter-annual and decadal-scale variability of precipitation,and only the wet day precipitation and the regional trend in consecutive dry days are significant at the 0.05 level.It can be concluded that the variation of extreme precipitation events is not obvious in the Hengduan Mountains,however,the regional trends generally decrease from the south to the north.Overall,the spatial distribution of temporal changes of all extreme climate indices in the Hengduan Mountains illustrated here reflects the climatic complexity in mountainous regions.
基金supported by the Youth Foundation of the National Natural Science Foundation of China (41401033)the Chinese Postdoctoral Science Foundation (2014M560819)+1 种基金the General Program of the National Natural Science Fund of China (Nos. 31370466, 41271037)the Natural Science Foundation of Gansu Province (No. 145RJZA141)
文摘Evapotranspiration (ET) within an ecosystem is crucial for die water-limited environment that currently lacks adequate quantification in the arid region of Northwest China, mainly covered by phreatophytes, such as the Populus euphratica Oliv. tree and the Tamarix ramosissima Ledeb. shrub species. Accordingly. ET was measured for an entire year using eddy covariance (EC) in P. euphratica stands in the lower Heihe River Basin, Northwest China. During the growing season, the total ET was 850 mm, with a mean of 4.0 mm/d, Which is obviously more than that observed at tree-level and stand level scales, which was likely due to the different level of soil evaporation induced by irrigation via water conveyance. Factors associated with ET fall into either environmental or plant eco-physiological categories. Environmental factors account for at least 79% variation of ET and the linear relationship between ET and the voundwater table (GWT) revealed the potential water use of P. euphratica forests under the non-water stress condition with die GWT less than 3 m deep. Plant eco-physiological parameters, specifically die leaf area 'index (LAI), have direct impact on the seasonal pattern of ET which provides a valuable reference to the wide-area estimates of ET for riparian forests by using LAI. In conclusion, P. euphratica forests have high water use after water conveyance, which may be the result of long-term adapting to local climates and limited water availability.
基金supported by a West Light Program for Talent Cultivation of the Chinese Academy of SciencesGansu Province Science Foundation for Distinguished Young Scholars (No. 1506RJDA282)+3 种基金the National Natural Science Foundation (No. 91547102)the CAS/SAFEA International Partnership Program for Creative Research Teamsa postdoctoral fellowship of ZongXing Li in the International Exchange Plans from the China Postdoctoral Association (No. 20140043)the Youth Innovation Promotion Association, CAS (No. 2013274)
文摘The sub-cloud evaporation effect refers to the evaporation process for raindrops that fall from the cloud base to the ground, which is usually accompanied by depleted light isotopes and enriched heavy isotopes in the precipitation. Based on 461 event-based precipitation samples collected from 12 weather stations in the Qilian Mountains and the Hexi Corridor from May to August of 2013, our results indicated that sub-cloud evaporation has a great influence on the δ^18O of precipitation, especially in small-amount precipitation events. In May, June, July, and August the δ18O composition was enriched by 35%, 26%, 39%, and 41%, respectively, from the cloud base to the ground. This influence clearly strengthened with temperature rise, from the Qilian Mountains to the Hexi Corridor. When falling raindrops are evaporated by 1.0% in the Qilian Mountains and the Hexi Corridor, the composition of δ18O would be enriched by 1.2% and 2.6%, respectively. Temperature dominated the sub-cloud evaporation in the Qilian Mountains, whereas relative humidity controlled it in the Hexi Corridor. These results provide new proofs of the evolutional process of stable isotopes in precipitation in arid regions.
基金CAS Western Light Program, No.O828Al1001 China Postdoctoral Science Foundation, No.2012M510219+6 种基金 National Natural Science Foundation of China, No.91025002 No.30970492 No.KZZD-EW-04-05 National Natural Science Foundation of China, No.llJ0930003 The CAS Special Grant for Postgraduate Research, Innovation and Practice The Foundation from the State Key Laboratory of Cryosphere Science The Founda- tion from Lijiang City Government
文摘Studying the response to warming of hydrological systems in Chin＇s temperate glacier region is essential in order to provide information required for sustainable develop- ment. The results indicated the warming climate has had an impact on the hydrological cycle. As the glacier area subject to melting has increased and the ablation seasor has become longer, the contribution of meltwater to annual river discharge has increased. The earlier onset of ablation at higher elevation glaciers has resulted in the period of minimum discharge occurring earlier in the year. Seasonal runoff variations are dominated by snow and glacier melt, and an increase of meltwater has resulted in changes of the annual water cycle in the Lijiang Basin and Hailuogou Basin. The increase amplitude of runoff in the downstream re- gion of the glacial area is much stronger than that of precipitation, resulting from the promi- nent increase of meltwater from glacier region in two basins. Continued observations in the glacierized basins should be undertaken in order to monitor changes, to reveal the relation- ships between climate, glaciers, hydrology and water supplies, and to assist in maintaining sustainable regional development.
文摘This research was conducted in the upstream watershed of the Mae Yom Irrigation Project, which was located in the Upper Yom River Basin in Phrae Province, Thailand. The most common troublesome in this area is flood and drought and leads to poor water management by difficult river flow forecasting to an existing large weir without upstream dam. The Soil And Water Assessment Tool (SWAT) model was applied for the simulation of the hydrological system and predicting the daily river flow to the upstream weir during flood season in 2006 and 2011 as for simulating and comparing with observed data. The results were fitted to the observed data with Nash and Sutcliffe efficiency (NSE) of ?0.65, and root mean square error (RSME) of 228.0 whereas the mean inflow discharge during wet season in both years was 173.3 cubic meters per second, respectively.
基金supported by the Gansu Province Science Fund for Distinguished Young Scholars (1506RJDA282)the National Natural Science Foundation of China (41271039, 91547102)+2 种基金the Open Foundation of MOE Key Laboratory of Western China’s Environmental System of Lanzhou Universitythe Open Foundation from State Key Laboratory (SKLFSE201403)the West Light Program for Talent Cultivation of Chinese Academy of Sciences
文摘Precipitation chemistry analysis is essential to evaluate the atmospheric environmental quality and identify the sources of atmospheric pollutants. In this study, we collected a total of 480 precipitation samples at 6 sampling sites in the northern and southern slopes of Wushaoling Mountain from May 2013 to July 2014 to analyze the chemical characteristics of precipitation and to identify the main sources of ions in precipitation. Furthermore, we also explored the indicative significance for sand dust events in the northern and southern slopes of Wushaoling Mountain based on the precipitation chemistry analysis.During the sampling period（from May 2013 to July 2014）, the p H values, EC（electrical conductivity）values and concentrations of cations（Ca^（2＋）, Mg^（2＋）, Na~＋, K~＋ and NH_4~＋） and anions（SO_4^（2–）, NO_3~–, Cl~–, NO_2~– and F~–） in precipitation were different in the northern and southern slopes at daily and seasonal time scales, with most of the values being higher in the northern slope than in the southern slope. The chemical type of precipitation in the southern and northern slopes was the same, i.e.,SO_4^（2–）-Ca^（2＋）-NO_3~–-Na~＋. The concentrations of ions in precipitation were mainly controlled by terrigenous material and anthropogenic activities（with an exception of Cl~–）. The concentration of Cl~– in precipitation was mainly controlled by the sea salt fraction. The concentrations of Na＋ and Cl~– showed an increasing trend after the occurrence of sand dust events both in the northern and southern slopes. In addition, after the occurrence of sand dust events, the concentrations of K~＋, Mg^（2＋）, SO_4^（2–）, NO_3~– and Ca^（2＋） showed an increasing trend in the southern slope and a decreasing trend in the northern slope. It is our hope that the results may be helpful to further understand the atmospheric pollution caused by sand dust events in the Wushaoling Mountain and can also provide a scientific basis for the effective prevention of atmospheric pollution.
基金supported by the Basic ScientificResearch Operation Expenses of Central Public Welfare Research Institutes(Y917006,Y917008)
文摘To increase dynamic stability of the quadrotor unmanned aerial vehicles in varying mechanical structure. The qualitative analysis is considered the main methods for analyzing the dynamic stability, while the index of qualitative analysis of the structural stability and the dynamic stability are still hard to establish. Therefore, the process during rolling or pitching is selected for investigating in the present papers, the method of Lyapunov exponent is adopted for establishing the quantification relationship of between structural parameters of quadrotor unmanned aerial vehicles and dynamic stability, and its dynamic stability for guiding the design of the vehicle′s mechanical structure and the optimization of its stability control by using the relationship. As compared to its counterpart of Lyapunov′s second method, the main advantage of the concept of Lyapunov exponents is that the methods for calculating the exponent process are constructive which makes the stability analysis of complex nonlinear systems possible.
基金supported by the Key Project of the Chinese Academy of Sciences(KZZD-EW-04-05)a Key Project of the National Natural Science Foundation of China(30970492,31270489,31270482)a Project for Incubation of Specialists in Glaciology and Geocryology of the National Natural Science Foundation of China(11J0930003)
文摘Global climate change has been evident in many places worldwide. This study provxdes a better understanding of the variability and changes in frequency, intensity, and duration of temperature, precipitation, and climate extremes in the Extensive Hexi Region, based on meteorological data from 26 stations. The analysis of average, maximum, and minimum temperatures revealed that statistically significant warming occurred from 1960 to 2011. All temperature extremes dis- played trends consistent with warming, with the exception of coldest-night temperature （TNn） and coldest-day tempera- ture （TXn）, which were particularly evident in high-altitude areas and at night. Amount of precipitation and number of rainy days slowly increased with no significant regional trends, mainly occurring in the Qilian Mountains and Hexi Cor- ridor. The significance of changes in precipitation extremes during 1960-2011 was high, hut the regional trends of max- imum 5-day precipitation （RX5day）, the average precipitation on wet days （SDII）, and consecutive wet days （CWD） were not significant. The variations in the studied parameters indicate an increase in both the extremity and strength of precip- itation events, particularly in higher-altitude regions. Furthermore, the contribution from very wet precipitation （R95） and extremely wet precipitation （R99） to total precipitation also increased between 1960 and 2011. The assessment of these changes in temperature and precipitation may help in developing better management practices for water resources. Future studies in the region should focus on the impact of these changes on runoffs and glaciers.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41822708 and 41571178)the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDA20100102)+1 种基金the Fundamental Research Funds for the Central Universities (Grant No. lzujbky-2018k15)the Second Tibetan Plateau Scientific Expedition (STEP) program (Grant No. XDA20060700)
文摘Hydrological circulation,as the most basic material cycle and active natural phenomenon on earth,exerts a significant in fluence on climate change.The mid-Holocene is an important period to better understand modern environmental change;however,little research has focused on its quantitative simulation of paleo-hydrological process.In this research,we first collected chronological evidence and sediment records from six Holocene sedimentary sections in the Shiyang River Ba sin to reconstruct the mid-Holocene environment and terminal paleo-lake area.Secondly,we comprehensively analyzed modern pollen combinations and their propagation characteristics in surface soil,air,river and lacustrine sediments in the Shiyang River Basin,and combined the pollen records,as well as quantitatively reconstructed the millennial-scale vegeta tion zones.Finally,based on the land-cover adjustment results during the mid-Holocene,we successfully used the Soil and Water Assessment Tool(SWAT)model,a modern distributed hydrological watershed model,to simulate mid-Holocene runoff in the basin.Results show that the reconstructed climate in the basin was warmer and moister than that in recent times.Vegetation types in the mid-Holocene mainly consisted of sub-alpine shrub distributed between 2,550 m and 2,750 m,forest at an elevation of 2,550 2,750 m,steppe at an elevation of 1,550 2,150 m and desert steppe below 1,550 m.The up stream,midstream,downstream and average annual runoff of the mid-Holocene in the basin were 16.76×10^8 m^3,22.86×10^8 m^3,9.00×10^8 m^3 and 16.20×10^8 m^3 respectively,compared to 15.61×10^8 m^3 of modern annual runoff.Also,the area of terminal paleo-lake in the mid-Holocene was 628 km^2.Thus,this study provides a new quantitative method for paleo-hy drological simulation.
