高浑浊内河悬沙浓度的遥感估测:以中国云南金沙江下游支流为例

山区土地利用和土地覆盖变化对水文过程的影响是人们关注的热点,因为它与洪水或干旱等严重的自然灾害有密切关系。一般认为,森林的清除会引起一个地区水沙量的明显增加。但是,要通过在地面进行观测来测算大河流域泥沙流量是十分困难的,特别在山区和人烟稀少地区更是如此。遥感手段为在这些地区收集相关资料和数据提供了一个有效的途径。在这个研究项目中,我们开发出了基于测量在可见光、近红外光波段的遥感反射系数的高浑浊内陆河流悬沙浓度(SSC)预测方法,并采用了中国云南金沙江下游河流SSC的地面观测值和河水反射光谱的数据进行了校准和检验。 我们在2002年6月龙川江的流量和输沙量比较高的时候开展了野外调查,使用了GER—1500手持光谱仪测量河水的反射光谱。SSC的地面观测值采用标准水样过滤法获取。结果表明,地面观测得到的SSC的变化范围为16～13 000g/m~3,其中间     

MORPHOLOGY, SEDIMENTARY BEDFORMS AND SAND TRANSPORT ACROSS A RIDGE-AND-RUNNEL BEACH UNDER THE ACTION OF SUMMER WAVES

As part of a collaborative study between the 3rd Institute of Oceanography, Xiamen, and the U-K. Universities of East Anglia and St. Andrews, a 4-day experiment was conducted on a ridge- and -runnel beach of north Norfolk on the North Sea coast- Detailed surveys were made of every low water of an area 10m by 30m and electromagnetic current meters were used to measure wave- induced currents over the ridge and in the runnel- The locations of bedform fields were noted, fluorescent sand was used to follow the sand movement and, at the end of the experiment, lacquer peels were taken of the top 0-2 m of a vertical section through the ridge- and- runnel-During the 4 days 0-75 m3 of sand per metre width of beach accreted in the runnel and a similar volume was eroded from the upper foreshore. The dominant shoreward transport, identified qualitatively by the movement of the fluorescent sand, suggests the ridge- and- runnel system migrated shorewards up the general beach slope of 1 by 2 - 3 m. The wave orbital cur     

重新评估新马德里地震带

以新马德里地震带(以下简称NMSZ，图1)而知名的美国大陆中部地区，尽管远离板块边界，但却频繁发生特大地震，其发震机制一直是个未解之谜。NMSZ地区并没有大多数活动形变地区构造运动特征的显著地形起伏，但当面对该整个地区地震危险性在某些概率水平上可以与旧金山湾地区相比的证据时，我们多数人感到需要“拧自已一下以看看我们是否在做梦”。尽管在很多方面，评估NMSZ地区的危险性比评价美国西部地区更具挑战性，不确定性更大，但经过细致地科学研究，已经在地震危险性评估的最关键问题上达成了共识。[这里给出的一致性看法反映了美国地质调查局和美国中部地震中心(一个由国家科学基金会资助的大学协会组织)2000年1月主办的一次讨论会上与会的二十几位科学家在会上及会后在国际互联网和专业会议上公开发表的一些看法。]     

秘鲁祖尔卡尼矿区金属比值的研究

前言通过对一系列矿脉中的金属含量或矿物含量的水平变化或垂直变化的研究,对硫化矿床的分带现象早就有所认识,把金属的实际含量标绘在矿脉的剖面图上或矿区的横剖面图上,就成为一种定量的工作方法,往往可以用它来摸清矿床的分带模式,对指示富矿的分布比研究化学成份的变化更为有效.金属含量高的地区,矿脉特别宽,或者是该区基岩受到强烈的破碎,因而有大量硫化物沉淀.由于金属含量变化受矿物沉淀的物理化学作用或构造作用的控制,单靠金属含量变     

根据长期树木年轮记录再现美国大平原的干旱

1、引言近百年内,美国大平原普遍发生的几次干旱造成农业崩溃,引起经济危机。其中十九世纪90年代、二十世纪30年代和50年代的干旱最引人注目。严重干旱重现的经验概率对研究水资源和农业生产规划很有意义。但目前的降水资料不能描绘十九世纪以前的干旱史。近来的研究证明了利用树木年轮资料延长区域干旱历史的实用性。这些研究仅是个别州的干旱,范围较小。     

THE DISTRIBUTION PATTERNS OF BACTERIA,ATP AND THE RELATIONS WITH RESPIRATION RATES AND PHYTOPLANKTON IN THE CHANGJIANG ESTUARY AND ITS ADJACENT EAST CHINA SEA

Two cruises were conducted in January and July 1986 in the Changjiang (Yangtse River) Estuary and its adjacent East China Sea (30°45′ -32°00′N,121°00′-124°00′E). Direct epifluorescence counts of planktonic bacteria and determinations of ATP concentrations were made. Subsamples were taken for measurement of oxygen consumption rates and chlorophyll concentrations.Bacteria and ATP concentrations were higher in summer than in winter, highest in the river and the river mouth, and gradually lower offshore. The bacteria number was correlated positively with suspended matter, nitrates and oxygen consumption rates, and negatively with salinity.In winter bacteria were the main contributors of ATP and the main consumers of dissolved oxygen in the whole studied area. In summer two maxima of ATP were found along the salinity gradient. The first one which coincided with the peak of turbidity near the river mouth was attributed to bacte -ria, and the second which occurred in the waters with a salinity range be