Estimation on dynamic release of phosphorus from wind-induced suspended particulate matter in Lake Taihu   总被引：16，自引：4，他引：12  

FAN Chengxin  ZHANG Lu    QIN Boqiang  WANG Sumin  HU Weiping & ZHANG Chen . Taihu Lake Laboratory for Ecosystem Research  Nanjing Institute of Geography & Limnology  Chinese Academy of Sciences  Nanjing  China  . Graduate School of Chinese Academy of Sciences  Beijing  China 《中国科学D辑(英文版)》2004,47(8):710-719

The internal source, especially resuspension process of the sediments in lakes and its environ- mental effect has been paid shining attention in the West as well as in China[1—6] although the influence of external source is important to water environment[7]. S鴑dergaard et al. compared the releases of soluble reactive phosphorus (SRP) in the surface sediments of Lake Arres before and after disturbance and they found that disturbing can increase the release by 20—30 times[3]. Robarts and ot…  相似文献   

A soil acidification study using the PROFILE model on two contrasting regions in Switzerland   总被引：1，自引：0，他引：1  

Urs Eggenberger  Daniel Kurz   《Chemical Geology》2000,170(1-4):243-257

The steady-state soil chemistry model PROFILE was used to calculate the chemical status of forest soils under present deposition loads for two areas with dissimilar ecosystem properties. Two regions in Switzerland, with contrasting bedrock geology were selected to be investigated in detail: 88 locations in the Jura Mountains, representative for carbonate bedrock and 91 locations in the Ticino Area dominated by metamorphic crystalline host rocks. Weathering rates calculated for the key regions cover the tremendous range between 0.013 and 25 keq ha⁻¹ yr⁻¹. In the Ticino Area, the effect of increased abundance of relatively fast weathering silicates (epidote, hornblende and plagioclase) on the weathering rate is apparently masked by the total effects of the physical conditions applied and by the variation in the deposition load. In the Jura Mountains, generally high weathering rates occur with about 50% of the sites yielding rates above 1 keq ha⁻¹ yr⁻¹. In many of the sites investigated, however, carbonates have already been dissolved completely in the soil horizons of interest resulting in very low weathering rates. The critical load of actual acidity was calculated according to: CL_Acidity=R_Weathering−ANC_Leaching, where alkalinity leaching is estimated by keeping the base cation to aluminum molar ratio at the critical limit of 1 at steady-state. The minimum critical load calculated was 0.2 keq ha⁻¹ yr⁻¹ and the maximum was 6.2 keq ha⁻¹ yr⁻¹. Comparing the cumulative frequency distributions of critical loads of actual acidity for forest soils in the individual areas it can be seen that the differences between the key regions are less substantial than with the weathering rates. Critical loads of acidity for the Ticino Area range from 1 to 3.9 keq ha⁻¹ yr⁻¹. Sites yielding the lowest critical loads of acidity are observed in the Jura Mountains. Among these apparent sensitive soils are soils with intermediate or high weathering rates, although it has depleted topsoil layers. Within the context of this model application, it becomes apparent that the sensitivity of these soils with respect to acidification is also governed by the alkalinity leaching term and not only by the susceptibility of its minerals to weathering.  相似文献   

桩的水平承载力实用非线性计算方法--NL法   总被引：30，自引：5，他引：25  

叶万灵  时蓓玲 《岩土力学》2000,21(2):97-101

以大量的桩基水平静载荷试验实测资料为基础,提出了一种水平土抗力与深度、位移的函数关系以及水平地基反力系数与土质指标的函数关系,并利用相似原理,将非线性有限远的数值计算转化为简单的查表计算,建立了一种新的桩的水平荷载作用下的非线性计算方法－－ＮＬ法,３９根桩的实例计算结果表明,该方法具有可靠的精度和较强的实用性。  相似文献   

An interfacial mechanical model for the analysis of earthquake     

张之立  沈新普  Zenon Mroz 《地震学报(英文版)》2000,13(5):591-596

IntroductionChina is a country suffered frequent earthquake disasters. The investigation on the mechanism of earthquake is of great significance. In the recent decades numerous researchers had carried out a great deal of research works on the theory of seismology and related in-situ observations (DU, SHAO, 1999; JIANG, et al, 1998; JIAO, et al, 1999; ZENG, SONG, 1998). However the mechanism of earthquake and relevant calculations still remain unsolved and problems still exists in pre…  相似文献   

The tempo-spatial evolution characteristics of the load/unload response ratio before strong earthquakes in California of America and its predicting implications   总被引：1，自引：0，他引：1  

宋治平  尹祥础  王裕仓  徐平  薛艳 《地震学报(英文版)》2000,13(6):628-635

IntroductionThetheoryoftheload/unloadresponseratio(LURR)hasbeenproposedabouttenyears(YIN,YIN,1991).Thetheoreticalstudieshavebeendevelopedfromtheoreticalanalysistorockexperimentandnumericalsimulation(SHI,etal,1994;WANG,etal,1999).IncharacteristicsoftheLURRanomalies,atfirst,weonlyanalyzedthevariationoftheload/unloadresponseratio(LURR)versustimeinthefixedregions(YIN,etal,1994;YIN,etal,1995).Thenwestudiedthetempo-spatialevolutionfeaturesoftheLURRintheseismogenicprocessanddevelopedthe…  相似文献   

第四系土层大直径超长桩的承载特性   总被引：2，自引：0，他引：2  

胡立明 《华东地质学院学报》2000,23(1):35-38

在没有良好的持力层 (基岩或砂、卵石层 )和成熟经验可借鉴的情况下 ,对第四系土层大直径超长桩 (钻孔灌注桩 )的承载特性进行了分析。并以分析结果为依据 ,预估单桩承载力 ,结果与静力试桩结论相吻合。  相似文献   

美国加州地区地震前加卸载响应比的时空演化特征及预测意义.   总被引：3，自引：2，他引：1       下载免费PDF全文

宋治平  尹祥础  王裕仓  徐平  薛艳 《地震学报》2000,22(6):588-595

对美国加州地区1976～1994年6级以上强震的加卸载响应比的时空演化过程进行了系统分析,指出该地区强震前响应比在震前3～4年开始大范围出现与该地区的区域构造走向一致的高犢区,高犢区以每年数十公里的速率向震中附近地区收缩．震中附近地区的响应比异常主要呈升——降型特征,多数地震在震前１年内响应比才升高,并且上升曲线较陡．该区内正地震一般形成丛集区,主震发生在正地震丛集区内或边缘．在分析美国加州地区地震与中国大陆地区地震特征异同的基础上,讨论了如何应用响应比的时空演变特征,对美国加州地区强地震三要素（地点、时间、强度）的中期预测进行估计的步骤与方法．   相似文献   

国际集装箱枢纽港的形成演化机理与发展模式研究   总被引：15，自引：2，他引：13  

安筱鹏  韩增林  杨荫凯 《地理研究》2000,19(4):383-390

集装箱运输作为对世界杂货运输的一场革命,实现了运输的全球化、信息化、高效化和门对门。港口作为联接集装箱海向腹地和陆向腹地的重要节点,在整个集装箱运输体系中有着非常重要的地位,集装箱运输自身的发展规律决定了集装箱港口功能的分异,即枢纽港与支线港的分离。本文在论述了世界集装箱港口发展现状及趋势的基础上,分析了集装箱枢纽港的形成演化机理与世界集装箱枢纽港的成长模式,并探讨了中国集装箱枢纽港的发展战略。  相似文献   

ROCESSES OF EPHEMERAL GULLY EROSION   总被引：2，自引：0，他引：2  

Javier Casali 《国际泥沙研究》2000,(1)

IINTRoDUCTIONEphemeralgulliesaresmallerosionalchannelsonagriculturalIandscapescausedbytheconcentrationofoverlandflowtypicallybetweentwoopposingslopes(ahollow),oftenformedduringasingIerainfaIlevent.Sincethescouredsoilvolumeisnotverylargewithinthesegullies,farmerscaneasilyrefillthem.Ingeneral,ephemeralgulliescanreappearatornearthesamelocationonayearlybasisbecausethesurfacetopograPhyofthefielddoesnotchangeappreciably.Mostephemeralgulliesoccuroncultivatedfieldswithhighlyerodiblesoils,withlit…  相似文献   

SEDIMENT TRANSPORT PROCESSES IN AGRICULTURAL WATERSHEDS     

Roger A. Kuhnle  Sean J. Bennett  Carlos V. Alonso  Ronald L. Bingner  Eddy Langendoen 《国际泥沙研究》2000,(2)

lINTR0DUCTI0NTheerosion,transportanddep0siti0nofsedimentinawatershedarepallofthenaturalsystemofwatershedprocesses.InanundistUrbedwatershed,s0ilsinuplandareasaregraduallyeroded,transportCdforsomedistanceandeventuallydepositedatlowereIevations.WhenwatershedsaredistUrbedbyhumanactivitiessuchasclearingofvegetation,urbaniZati0n,orotherchangesthataffectthelandscaPe,unstablechannelswithlocallyhighratesoferosion,transport,0rdepositionofsedimentoftenaretheresult.Theimpact0fer0sionisespeciallyhigh…  相似文献