检索结果-南通市图书馆

Influence of the impounding process of the Three Gorges Reservoir up to water level 172.5m on water eutrophication in the Xiangxi Bay

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2010年第4期53卷 1114-1125页

作者： YANG ZhengJian1,LIU DeFu1,JI DaoBin1,2 & XIAO ShangBin1,3.1 college of Civil & Hydroelectric Engineering,china Three Gorges university,Yichang 443.02,china 2 School of Water resources & Hydropower Engineering,Wuhan university,Wuhan 43.072,china 3.Institute of Earth environment,Chinese Academy of Sciences,Xi’an 710075,china 1. college of Civil & Hydroelectric Engineering China Three Gorges University Yichang 443002 China2. School of Water Resources & Hydropower Engineering Wuhan University Wuhan 430072 China3. Institute of Earth Environment Chinese Academy of Sciences Xi’an 710075 China

The water level of the Three Gorges Reservoir(TGR) rose to 172.5 m in two stages from September to November,*** hydrodynamic parameters and water quality parameters(*** velocity,temperature,turbidity and nutrient content) had been continuously monitored to reveal the influence of the impounding process of the TGR on the water eutrophication in the Xiangxi Bay(XXB).The maximal daily rise of the water level of the TGR was about 2.3. *** water exchange between the mainstream(the Changjiang River) and the XXB of the TGR was enhanced by density current,and its main characteristics were a density-stratified flow in different *** water exchange reduced the differences of the water quality parameters(for example,temperature,turbidity,nutrient level,pH,etc.) between the mainstream and the XXB during the impounding ***,the water stability index in the mainstream remained small but it was lowered in the *** main causes included the dilution by water of lower concentration of the chlorophyll a(Chl.a) entering from the mainstream,the decline of the water stability,and the increase of suspended silt,which induced the Chl.a to decrease in the XXB during the impounding *** grade of the water eutrophication changed from middle eutrophic level to mesotrophic state in the ***,as available nutrients were imported into the XXB from the mainstream during the impounding process the risk of water eutrophication increases in the XXB in the future.

关键词： impounding density current eutrophication the Xiangxi Bay the Three Gorges Reservoir

Effect of Different Irrigation Methods on Dissolved Organic Carbon and Microbial Biomass Carbon in the Greenhouse Soil

在线全文

学校读者我要写书评

暂无评论

agricultural Sciences in china 2010年第8期9卷 1175-1182页

作者： HAN Lin,ZHANG Yu-long,JIN Shuo,WANG Jiao,WEI Yan-yan,CUI Ning and WEI Wei college of Land and environmental Sciences,Shenyang agricultural {3./Liaoning Key Laboratory of agricultural resources and environment,Shenyang 110161,P.R.china [a] college of Land and environmental Sciences Shenyang Agricultural University/Liaoning Key Laboratory of Agricultural Resources and Environment Shenyang 110161 P.R.China

The objective of this study was to investigate the contents and distribution of dissolved organic carbon （DOC） and microbial biomass carbon （MBC） at 0-100 cm soil depth under three irrigation treatments, viz., subsurface, drip and furrow irrigation in the greenhouse soil. The soil samples were collected at different depths （0-100 cm）, and the contents of soil total organic carbon （TOC）, DOC and MBC were analysed. The experiment was conducted for 10 yr, during which period the application of fertilizers and crop management practices were kept identical. The results showed that the contents of TOC, DOC and MBC were significantly affected by different irrigation regimes, decreased with the increase of soil depth. TOC at 0-10 and 80-100 cm soil depths followed the order of furrow irrigation 〉 subsurface irrigation 〉 drip irrigation, whereas at the depth of 10-80 cm followed the order of subsurface irrigation 〉 furrow irrigation 〉 drip irrigation. DOC and MBC contents at 0-100 cm soil depths followed the order of furrow irrigation 〉 drip irrigation 〉 subsurface irrigation, and drip irrigation 〉 furrow irrigation 〉 subsurface irrigation, respectively. The ratios of DOC and MBC to TOC accounted for 4.98-12.87% and 1.48-2.82%, respectively, which were the highest in the drip irrigation treatment, followed were in the furrow irrigation treatment, and the lowest in subsurface irrigation treatment. There were significant positive correlations among the contents of DOC, MBC and TOC in all irrigation treatments. The furrow irrigation facilitated the accumulation of TOC and DOC, while drip irrigation increased the MBC. The content of TOC and the ratios of DOC to TOC were the lowest in subsurface irrigation treatment.

关键词： greenhouse irrigation methods total organic carbon dissolved organic carbon microbial biomass carbon

Adsorption and Insecticidal Activity of Toxin from Bacillus thuringiensis on Rectorite

在线全文

学校读者我要写书评

暂无评论

Pedosphere 2007年第4期17卷 513-521页

作者： ZHOU Xue-Yong HUANG Qiao-Yun CAI Peng YU Zi-Niu Hubei Province Key Laboratory of Refractories and Ceramics Wuhan University of Science and Technology Wuhan 430081 （China）. college of Biotechnology and Chemical Engineering Tianjin University of Technology Tianjin 300191 （China） State Key Laboratory of agricultural Microbiology College of Resources and Environment Huazhong Agricultural Uni- versity Wuhan 430070 （China）

The adsorption and desorption of the toxin from Bacillus thuringiensis strain WG-001 on rectorite were studied at different toxin and/or rectorite concentrations, pH values and temperatures. The insecticidal activity of the adsorbed toxin was evaluated by determining the lethal concentration to kill 50% of the larvae of Heliothis armigera （LC50）. The adsorption of the toxin on rectorite in sodium carbonate buffer （pH 9） reached equilibrium within 0.5-1.0 h and the adsorption isotherm of the toxin followed the Langmuir equation （R^2 〉 0.99）. In the pH range from 9 to 11 （carbonate buffer）, the adsorbed toxin decreased with increasing pH. The adsorption amounts decreased with increasing rectorite：toxin ratio. The adsorption was not significantly affected by the temperature between 10 and 50 ℃. The X- ray diffraction analysis indicated occurrence of the intercalation of the rectorite by the toxin. The infrared absorption spectrum showed that the binding of the toxin did not alter its structure. The LC50 wlues of the adsorbed toxin were smaller than those of the free toxin. The rectorite protected the toxin from ultraviolet irradiation damage. The desorption of the adsorbed toxin in water ranged from 3..5% to 56.4% and from 27.4% to 41.8% in a carbonate buffer. The desorption percentage also decreased with increasing rectorite：toxin ratio.

关键词： Bacillus thuringiensis insecticidul uctivity rectorite toxin udsorption und desorption

Effect of Perched Water Tables on Aluminosilicate Stability and Soil Genesis

在线全文

学校读者我要写书评

暂无评论

Pedosphere 2000年第3期10卷 247-256页

作者： ZHANG MIN , GONG ZITONG and A. D. KARATHANASIS college of resources and environment, Shandong {3. university, Tai’an 271018 (china) Institute of Soil Science, the Chinese Academy of Sciences, Nanjing 210008 (china) college of Agriculture, U asteur.ivic.ve

The mineral stability and solute activities of soil solution extracted from selected horizons of seven studied pedons of Alfisols in Kentucky, USA, and the relationship between distribution of iron-manganese concretions and the restrictive layers were investigated. The results showed that the genesis and development of these soils and mineral weathering trends were strongly influenced by the depth of bedrock and the presence of perched water tables at lithic (limestone) interfaces due to the dissolution and buffering effect of limestone bedrock. The extractable Mg/Ca ratio as depth function and soil depth above bedrock could be used as indices of weathering and degree of soil development. Maximum iron-manganese concretion accumulation was found to occur in the horizon overlying clay horizon (>40% clay) with a sharp increase in clay content (>10%), which suggested that zones of Fe-Mn concretion accumulation in soils of the Inner Bluegrass Region appeared to be a sensitive genetic indicator of argillic horizons with restrictive permeability.

关键词： iron-manganese concretion perched water table soil environment soil genesD

INTERACTIVE STUDY BETWEEN IDENTICAL COHERENT STRUCTURES IN THE WALL REGION OF A TURBULENT BOUNDARY LAYER

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2002年第1期14卷 100-105页

作者： Lu Chang-gen (college of water resources and environment, Hohai {3., Nan jing 210098, china) college of water resources and environment Hohai University Nanjing 210098 China

A theoretical model for identica l coherent structures in the wall region of a turbulent boundary layer was propo sed, using the idea of general resonant triad of the hydrodynamic stability. The evolution of the structures in the wall region of a turbulent boundary layer wa s studied by combining the compact finite differences of high numerical accuracy and the Fourier spectral hybrid method for solving the three dimensional Navier -Stokes equations. In this method, the third order mixed explicit-implicit sch eme was applied for the time integration. The fifth-order upwind compact finite difference schemes for the nonlinear convection terms in the physical space, an d the sixth-order center compact schemes for the derivatives in spectral space were introduced, respectively. The fourth-order compact schemes satisfied by th e velocities and pressure in spectral space was derived. As an application, the method was implemented to the wall region of a turbulent boundary to study the e volution of identical coherent structures. It is found that the numerical result s are satisfactory.

关键词： coherent structure turbulent bounda ry layer compact finite difference

Land Use of the Three Gorges Reservoir Area and the Effect on Its Landscape Pattern in the Recent 50 Years

在线全文

学校读者我要写书评

暂无评论

Wuhan university Journal of Natural Sciences 2006年第4期11卷 910-914页

作者： HUANG Zhiqin 1,2,3., ZHOU Wancun 1 ,ZHOU Jieming 4 , ZHU Mingcang 3.5 1. Institute of Mountain Hazards and environment, Chinese Academy of Sciences , Chengdu 610041, Sichuan, china 2. Graduate university of Chinese Academy of Sciences, Beijing 100049, china 3. Sichuan Institute of Land Resource Management, Chengdu 610041, Sichuan , china 4. Department of resources and environment Science, Sichuan Normal university , Chengdu 610061, Sichuan, china 5. college of Information Engineering, Chengdu university of Technology, Chengdu 610059, Sichuan, china Institute of Mountain Hazards and environment Chinese Academy of Sciences Chengdu Sichuan China Graduate university of Chinese Academy of Sciences Beijing China Sichuan Institute of Land Resource Management Chengdu Sichuan China Department of resources and environment Science Sichuan Normal University Chengdu Sichuan China college of Information Engineering Chengdu University of Technology Chengdu Sichuan China

The paper makes detailed analysis on the changing processes of the main types of land use in Three Gorges Reservoir Area through the techniques of RS （Remote Sense） and GIS （Geography Information System）. Based on the theory of landscape ecology, many types of landscape pattern indexes are calculated and made correlation analysis. The results indicate that： in 1995 the ecological environment of Three Gorges Reservoir Area was the most vulnerable in the recent 50 years, but resumed in 2002; the landscape pattern diversity index, fractal dimension index and fragmentation index has close correlation with the area of land use/cover change （LUCC）. The research also releases that the increase of the cultivated land, grassland and construction land deteriorates the landscape ecological pattern, while the increase of forest land area will help restore the landscape ecological pattern to its original state. The rapid change of grassland is an important index of the change of landscape pattern, because it has the most effect on change of landscape pattern index.

关键词： the Three Gorges Reservoir Area land use/cover change landscape pattern.

Run off-on-out method and models for soil infiltrability on hill-slope under rainfall conditions

在线全文

学校读者我要写书评

暂无评论

Science china Earth Sciences 2006年第2期49卷 193-201页

作者： LEI Tingwu1,2, LIU Han1, PAN Yinghua3. ZHAO Jun2, ZHAO Shiwei2 & YANG Yonghui2 1. The Key Laboratory of Modern Precision Agriculture System Integration Research, college of Hydraulic and Civil Engineer-ing, china agricultural {3., Beijing 100083. china 2. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Yangling 712100, china 3. Geographic and resources Management college, Yantai Normal {3., Yantai 264025, china 1. The Key Laboratory of Modern Precision Agriculture System Integration Research College of Hydraulic and Civil Engineering China Agricultural University Beijing 100083 China 2. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau Institute of Soil and Water Conservation Yangling 712100 China 3. Geographic and resources Management college Yantai Normal University Yantai 264025 China

The soil infiltrability of hill-slope is important to such studies andpractices as hydrological process, crop water supply, irrigation practices, and soil erosion. A newmethod for measuring soil infiltrability on hill-slope under rainfall condition with run off-on-outwas advanced. Based on water (mass) balance, the mathematic models for soil infiltrability estimatedfrom the advances of runoff on soil surface and the water running out of the slope were *** of 2 cases were conducted. Case Ⅰ was done under a rainfall intensity of 20 mm/h, at aslope gradient of about 0° with a runoff/on length (area) ratio of 1 : 1. Case Ⅱ was under arainfall intensity of 60 mm/h and a slope of 20° with a runoff/on length (area) ratio of 1 : *** ring method was also used to measure the infiltrability for comparison purposes. Theexperiments were done with soil moisture of 10%. Required data were collected from laboratoryexperiments. The infiltrability curves were computed from the experimental data. The resultsindicate that the method can well conceptually represent the transient infiltrability process, withcapability to simulate the very high initial soil infiltrability. The rationalities of the methodand the models were validated. The errors of the method for the two cases were 1.82%/1.3.% and4.49%/3.529% (Experimental/Model) respectively, as estimated by comparing the rainfall amount withthe infiltrated volume, to demonstrate the accuracy of the method. The transient and steadyinfiltrability measured with double ring was much lower than those with this new method, due towater supply limit and soil aggregates breaking down at initial infiltration stage. The method canovercome the short backs of the traditional sprinkler method and double ring method for soilinfil-traility. It can be used to measure the infiltrability of sloped surface underrainfall-runoff-erosion conditions, in the related studies.

关键词： Infiltrability, runoff-on-out, rainfall, sloped surface, model.

Sequential Extraction of Natural Surface Coatings: Comparison with Single Stage Extraction and Its Application in Investigating Adsorption Characteristics of Surface Coating Components for Metals

在线全文

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2012年第1期28卷 41-46页

作者： HUA Xiu-yi, LIU Xiao-xue, DONG De-ming, LI Ming and LI Yao-rui Key Laboratory of Groundwater resources and environment, Ministry of Education, Key Lab of Water resources and Aquatic environment of Jilin Province, college of environment and resources, Jilin university, Changchun 13.012, P. R. china Jilin Univ Key Lab Groundwater Resources & Environm Key Lab Water Resources & Aquat Environm Jilin Pr Minist EducColl Environm & Resources Changchun 130012 Peoples R China

Multistage sequential extraction with different sequences was applied to extracting natural surface coa tings（NSCs）, and the results were compared with those by single stage extraction technique. The optimal sequential extraction scheme with the best performance was selected and incorporated into the method of selective extraction followed by adsorption and statistic analyses to study the adsorption parameters of Fe oxides, Mn oxides and organic matters in NSCs for Pb and Cd, to validate the applicability of the sequential extraction scheme. The Langmuir ad sorption parameters of each component of surface coating estimated according to the adsorption data of single stage extraction of NSCs were all similar to those of sequential extraction of NSCs, and the maximum difference between the metal adsorption abilities of the components estimated via the two extraction techniques was only about 20%, in dicating that either extraction techniques could be used. The optimal sequential extraction scheme obtained was first extracted with NH2OH·HCl, then with Na2S2O4, and finally with oxalic acid.

关键词： Natural surface coating(NSC) Sequential extraction Single stage extraction Adsorption Component

几种有机物对紫色土镉的溶出效应与吸附-解吸行为影响的研究

在线全文

学校读者我要写书评

暂无评论

土壤学报 2003年第1期40卷 110-117页

作者：魏世强木志坚青长乐西南农业大学资源与环境学院重庆400716

研究了天然有机物胡敏酸和富里酸 ,螯合剂EDTA和DTPA和四种简单有机酸对紫色土镉的溶出效应和吸附解吸行为的影响。结果表明 ,供试八种有机物均能显著促进镉从紫色土中的溶出。作用大小顺序为 :EDTA≥DTPA >柠檬酸 >胡敏酸 >草酸 >富里... 详细信息

研究了天然有机物胡敏酸和富里酸 ,螯合剂EDTA和DTPA和四种简单有机酸对紫色土镉的溶出效应和吸附解吸行为的影响。结果表明 ,供试八种有机物均能显著促进镉从紫色土中的溶出。作用大小顺序为 :EDTA≥DTPA >柠檬酸 >胡敏酸 >草酸 >富里酸 >酒石酸≥水杨酸。有机物对土壤镉溶出和迁移的影响是其对土壤镉吸附和解吸综合作用的结果。有机物显著降低了紫色土对镉的吸附 ,其作用大小顺序与其对镉的溶出能力的相对大小顺序一致 ,同时也改变了吸附镉的解吸特性。有机物影响下 ,紫色土镉的吸附动力学模型以双常数方程拟合最佳。而吸附等温曲线以Freundlich方程拟合最好 ,吸附常数n与有机物对土壤镉的溶出率之间存在良好的相关性。

关键词：有机物紫色土溶出效应吸附-解吸行为土壤镉重金属离子