Research on temporal and spatial distribution, evolutionary character and mechanism of crustal deformation field before and after the Tangshan earthquake   总被引：2，自引：0，他引：2  

周硕愚  施顺英  帅平 《地震学报(英文版)》1997,10(6):693-701

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苏南典型区土壤基本性质的时空变化——以昆山市为例   总被引：12，自引：0，他引：12  

万红友  周生路  赵其国 《地理研究》2006,25(2):303-310

以昆山市为例对苏南典型区土壤基本性质的时空变化进行了研究。结果表明:(1)与第二次土壤普查相比,该区土壤酸化严重,土壤上层pH值的平均值由7.20下降到6.42,土壤上层pH值小于6.0的样点多达36.51%;土壤有机质含量呈下降趋势,土壤上层有机质含量平均值由31.4 g/kg下降到28.3 g/kg,小于20 g/kg的土壤样品由0.56%上升到11.11%;速效磷含量总体上呈现明显的升高趋势,平均值由6.4mg/kg上升到89.1 mg/kg;阳离子交换量(CEC)由19.3 cmol/kg下降为17.8 cmol/kg。(2)不同功能区、不同地貌区及不同剖面层次的土壤基本性质存在较为明显的空间变化。  相似文献   

Water chemistry and water quality variation in the Danjiangkou Reservoir, as a function of water management for the Middle Route of South to North Water Divert Project, China     

Siyue LI Quanfa ZHANG 《中国地球化学学报》2006,25(B08):274-274

As the diversion dike of the Middle Route of the South to North Water Transfer Project （MRSNWTP）, the water quality and water quantity of Danjiangkou Reservoir is critical to the project. At present, the rates of industrial wastewater treatment and sewage discharge, which belongs to Chinese State Standard in the districts near the reservoir except Shiyan city, are less than 60% and 40% respectively. The point source pollutants will be controlled because of the project after some time, but the non-point source pollutants caused by vegetation degradation and water-soil erosion will not be controlled effectively in a long time. Water samples were collected from the Danjiangkou Reservoir during 2004 and 2005 and analyzed for trace metals, i.e., silver （Ag）, aluminum （Al）, arsenic （As）, barium （Ba）, bismuth （Bi）, calcium （Ca）, cadmium （Cd）, cobalt （Co）, chromium （Cr）, copper （Cu）, iron （Fe）, mercury （Hg）, potassium （K）, lithium （Li）, magnesium （Mg）, manganese （Mn）, molybdenum （Mo）, sodium （Na）, nickel （Ni）, lead （Pb）, antimony （Sb）, selenium （Se）, silicon （Si）, strontium （Sr）, vanadium （V）, zinc （Zn）, chemicophysical parameters and nutrients, i.e., temperature （T）, pH, dissolved oxygen （DO）, turbidity, total suspended solid （TSS）, nitrate/ammonia/ammonium-nitrogen （NO3^-/NH3/NH4^＋-N）, total nitrogen （TN）, dissolved inorganic nitrogen （DIN）, total phosphorus （TP）, potassium permanganate index （IMn）, biochemical oxygen demand （BOD）, dissolved inorganic carbon （HCO3^-）. Our results are water quality belongs to Chinese standard level II, trace metals are low, but they are accumulating, and many of which, i.e., As, Pb, will endanger reservoir water security.  相似文献   

东北夏季(6-8月)气温异常的时空特征分析   总被引：5，自引：0，他引：5  

李兰  王盘兴  陈长胜  李丽平 《南京气象学院学报》2005,28(6):801-807

利用夏季（6—8月）中国东北地区91站44a气温资料，采用谐波分析方法将该区夏季气温异常变化的年代际、年际尺度分量分离，研究时空特征，然后应用REOF进行气温异常的区划，研究局域异常变化的年代际、年际分量的变化特征。结果发现：1）东北各站夏季异常方差中，东北大部分地区的气温异常的年代际变化分量均明显大于年际变化分量。2）区域气温异常的年代际变化主要特征为线性上升趋势。大范围夏季异常高温（低温）常出现在年代际、年际异常同时为正（负）的年份。3）气温异常可划分为南部型、北部型、东部型、西部型4个型，其中南部型和西部型的年代际变化相对重要，而东部型和北部型的年际变化相对重要。  相似文献   

云南省冰雹的时空分布特征   总被引：13，自引：6，他引：13       下载免费PDF全文

杨家康  杞明辉 《气象科技》2005,33(1):41-44

利用近40年的云南省冰雹资料，统计分析了云南省冰雹的时空分布特征，进一步揭示了其活动规律及主要影响因素。研究结果表明：冰雹的季节分布比较复杂，呈现出春季和夏季两个峰值的特点；冰雹的季节分布还与海拔高度有关，低海拔地区为春季多雹型，高海拔地区为夏季多雹型；滇西地区冰雹日数的年际变化特征较滇东地区显著而年代际变化特征没有东部地区站点明显；滇东地区表现出了明显的年代际变化特征，目前处于冰雹相对较少时期。从区域来看，年冰雹日数山区较坝区高，高海拔地区较低海拔地区高。  相似文献   

新疆大风的时空统计特征   总被引：16，自引：2，他引：16  

王旭  马禹 《沙漠与绿洲气象(新疆气象)》2002,25(1):1-3

统计了1961－1999年39a新疆90个气象观测站的气表－1资料，给出新疆大风的时空分布特征，结果表明：（1）年平均大风日数的高值区在北疆西北部，东疆和南疆西部，阿拉山口，达坂城大风最多，准噶尔盆地中心，塔里木盆地南缘最少。（2）大风年总日数的变化有明显的波动性，大部分地区80年代起大风日数有减少的趋势。（3）春，夏季大风最多，以5，6月最为频敏，大风主要出现在上年10时到午夜23时，半数以上的大风持续时间在1h以上，以0.5h以内最多。  相似文献   

Spatial and temporal variability of pore‐water pressures in residual soil slopes in a tropical climate     

R. B. Rezaur  H. Rahardjo  E. C. Leong 《地球表面变化过程与地形》2002,27(3):317-338

It is critical to understand and quantify the temporal and spatial variability in hillslope hydrological data in order to advance hillslope hydrological studies, evaluate distributed parameter hydrological models, analyse variability in hydrological response of slopes and design efficient field data sampling networks. The spatial and temporal variability of field‐measured pore‐water pressures in three residual soil slopes in Singapore was investigated using geostatistical methods. Parameters of the semivariograms, namely the range, sill and nugget effect, revealed interesting insights into the spatial structure of the temporal situation of pore‐water pressures in the slopes. While informative, mean estimates have been shown to be inadequate for modelling purposes, indicator semivariograms together with mean prediction by kriging provide a better form of model input. Results also indicate that significant temporal and spatial variability in pore‐water pressures exists in the slope profile and thereby induces variability in hydrological response of the slope. Spatial and temporal variability in pore‐water pressure decreases with increasing soil depth. The variability decreases during wet conditions as the slope approaches near saturation and the variability increases with high matric suction development following rainfall periods. Variability in pore‐water pressures is greatest at shallow depths and near the slope crest and is strongly influenced by the combined action of microclimate, vegetation and soil properties. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

干旱区水土资源时空变化的定量研究   总被引：11，自引：9，他引：11  

马兴旺  李保国  程远 《干旱区地理》2002,25(2):109-114

水资源是制约干旱区土地资源开发利用的主要自然因素，水、土资源利用在时间和空间上平衡与否的矛盾影响着干旱区生态环境与社会发展。用定量化的数学模型表示二者的互相影响，能描述、解释和预测二者关系并能为制定对策提供依据。本文首先分析了干旱区土地利用与水资源的相互影响，然后对水土资源相互影响下时空变化的模拟方法和理论进行了综述。一方面从蒸散的计算、模拟地下水补给、模拟区域尺度上土地利用影响、模拟土地管理措施影响、模拟抽取地下水影响、以系统方法模拟土地利用影响等几方面对土地利用影响下水资源的时空变化模拟进行了综述。同时对水资源影响下土地利用变化的模拟从主要考虑水文作用的水文－植被模型的建立应用及引入人为因素为驱动力的土地利用变化模拟两方面做了综述。文章最后进一步概括了干旱区水土资源时空变化模拟的趋势并就此方面的研究提出了三点展望意见。  相似文献   

京、津、冀区域群发性强沙尘暴分析   总被引：1，自引：2，他引：1  

刘学锋  安月改  田国强 《地理与地理信息科学》2003,19(6):74-76

利用1954—2002年82个站的气象观测资料，探讨京、津、冀区域群发性强沙尘暴的认定标准，构建较完整的群发性强沙尘暴序列，并分析该地区群发性强沙尘暴的时空分布特征和气候变化趋势。近50a京、津、冀区域共出现了39例群发性强沙尘暴，河北省的冀西北高原区和石家庄、保定、衡水、沧州四市交接处饶阳一带是京、津、冀区域强沙尘暴天气的多发区。多发季节为3—5月，占全年总数的76．9％，其中4月份最多，占全年总数的51．3％。群发性强沙尘暴年代际变化呈现总体减少趋势，其发生次数、覆盖面积均是以20世纪90年代为最低值．  相似文献   

(Re)surveying the uses of Geographical Information Systems in Health Authorities 1991–2001     

Darren P Smith  Myles I Gould  Gary Higgs† 《Area》2003,35(1):74-83

This paper provides a comparative analysis of two separate national surveys of the uptake and use of Geographical Information Systems (GIS) by Health Authorities (HAs) in England and Wales. The surveys were undertaken at two different time points (1991 and 2001), and the intervening period has been characterized by major (and continuing) health sector restructuring. The substantial number of HA mergers between 1991 and 2001 provide a methodological challenge in attempting to make comparisons. A pragmatic approach is adopted and the presentation of results has to be restricted solely to English and Welsh HA data. Our findings show that there has been a considerable increase in the use of GIS since the early 1990s, and there is some evidence of more sophisticated uses for a wider range of policy-related and application tasks. However, we conclude that there is still considerable scope for the wider uptake and use of GIS within the NHS. In addition, our findings provide a baseline with which to monitor the impacts of future organizational restructuring on the uses of GIS within the NHS. We suggest that this is important given the replacement of 95 English HAs with 28 new Strategic HAs (StHAs) from April 2002, and the repercussions of the anticipated shift in GIS responsibility to Primary Care Trusts.  相似文献