Sediment-related impacts due to upstream reservoir trapping, the Lower Mekong River   总被引：8，自引：0，他引：8  

Matti Kummu  Olli Varis 《Geomorphology》2007,85(3-4):275

A sharp decrease in total suspended solids (TSS) concentration has occurred in the Mekong River after the closure of the Manwan Dam in China in 1993, the first of a planned cascade of eight dams. This paper describes the upstream developments on the Mekong River, concentrating on the effects of hydropower dams and reservoirs. The reservoir-related changes in total suspended solids, suspended sediment concentration (SSC), and hydrology have been analyzed, and the impacts of such possible changes on the Lower Mekong Basin discussed. The theoretical trapping efficiency of the proposed dams has been computed and the amount of sediment to be trapped in the reservoirs estimated. The reservoir trapping of sediments and the changing of natural flow patterns will impact the countries downstream in this international river basin. Both positive and negative possible effects of such impacts have been reviewed, based on the available data from the Mekong and studies on other basins.  相似文献   

福建沿海盆地第四纪构造运动模式与动力学环境   总被引：2，自引：0，他引：2  

张路曲国胜  朱金芳李亦纲 黄宗林 《地质通报》2007,26(3):275-288

对福建省福州、泉州、漳州、厦门等城市所在盆地沉积和断裂的研究表明,自漳州地区向北东和向南西各盆地起始沉积、沉积间断和全新世海侵等事件是时间上依次发生的序列沉积事件,漳州及其以北各第四纪盆地构成向南西掀斜的箕状盆地。基于上述规律性,提出了自漳州向北东和向南西依次扩展的第四纪以来地壳隆张的运动模型。分析了菲律宾板块与欧亚板块的接触关系和相互作用,认为菲律宾板块的作用是该区第四纪构造运动的主要驱动力,巴士系构造是该区地壳运动的触发构造。  相似文献   

鄂西震旦系灯影组白鸡河锌矿床地质特征及成因探讨     

雷义均  伍齐学  刘圣德  雷天赐 《华南地质与矿产》2007,(3):37-42

在鄂西震旦系白云岩地层中,新发现了白鸡河锌矿床、凹子岗铅锌矿床、冰洞山铅锌矿床。白鸡河锌矿床矿石成分简单,富锌贫铅;矿石结构主要为细晶结构、交代结构;矿石构造变化大,存在角砾状、浸染状、纹层状、条带状及"雪顶"构造;成矿温度低,白云石化交代角砾岩作用普遍;矿石硫同位素为重硫,值域很宽,闪锌矿与方铅矿在相对封闭环境沉淀。矿床地质特征可与MVT型铅锌矿床相类比,成因为碳酸盐岩容矿的后生沉积铅锌矿床。  相似文献   

航摄底片扫描数字化生产的质量控制     

任俊芳 《测绘科学与工程》2007,27(3):38-41

高精度高质量地完成航摄底片扫描数字化生产，确保数字化影像数据准确可靠，是保证全数字摄影测量成图成果质量的一个基础环节。本文在总结扫描数字化生产实践经验的基础上，论述了扫描数字化生产过程及成果的质量控制与检查问题，主要内容包括扫描仪参数的选择与状态维护、扫描过程中的自主质量控制及扫描结果的质量检查方法等。  相似文献   

胶州湾沉积速率:多种分析方法的对比^*   总被引：5，自引：0，他引：5  

汪亚平  高抒 《第四纪研究》2007,27(5):787-796

根据胶州湾内外海域采集的柱状岩芯样品的 ²¹⁰ Pb测试,结合物源分析方法,计算了1952年以来胶州湾的沉积物收支状况和胶州湾区域的平均沉积速率。结果表明,胶州湾百年尺度的沉积速率较高,达到了10⁰mm/a量级(7.43mm/a),沉积通量为10^-3g/mm²a量级(7.39×10^-3g/mm²a),而胶州湾外邻近海区沉积速率略低(4.46mm/a)。这与其他学者获得的海图地形对比法的结果大致相当。与胶州湾内钻孔岩芯的¹⁴ C测年对比表明,万年尺度的沉积速率为10^-1mm/a量级(0.25~0.92mm/a),比百年尺度的沉积速率约小一个数量级。分析结果表明,沉积体系的演化过程使沉积速率随时空尺度的不同而产生差异,这是导致不同分析方法所获结果之间存在复杂关系的主要因素。  相似文献   

河流碳输移与陆地侵蚀-沉积过程关系的研究进展   总被引：5，自引：0，他引：5       下载免费PDF全文

姚冠荣  高全洲 《水科学进展》2007,18(1):133-139

河流碳输移与陆地侵蚀-沉积过程紧密相关。首先就机械和化学风化两种不同的陆地侵蚀机制在提供河流碳源方面所发挥的不同作用作了详细论述,并比较了季风流域和非季风流域间河流碳输移在通量及性质上的差异。之后对陆地碳沉积机制进行了归纳,指出了包括大坝截留,河漫滩、河口-近岸带沉积及陆地碳沉降等几种可能的陆源碳踪迹。陆地环境的截留效应相对于侵蚀尚不太清楚,今后应加强对陆地碳沉积的研究,进一步明确各种碳沉积的作用机制及其对全球陆地碳汇的贡献量。此外,人类活动对陆地侵蚀-沉积过程及河流碳循环所产生的直接或间接的影响也有待于今后继续深入探索。  相似文献   

Deep water bottom current deposition in the northern South China Sea   总被引：8，自引：0，他引：8  

SHAO Lei  LI XueJie  GENG JianHua  PANG Xiong  LEI YongChang  QIAO PeiJun  WANG LiaoLiang & WANG HongBin State Key Laboratory of Marine Geology  Tongji University  Shanghai  China  Guangzhou Marine Geological Survey  Ministry of Land  Resources  Guangzhou  China  CNOOC Ltd. Shenzhen  Shenzhen  China 《中国科学D辑(英文版)》2007,50(7):1060-1066

There are some active bottom currents on the northern continental slope of the South China Sea (SCS). Reflection seismic profiles show that the bottom current channels occur in the water depth range of 1000 to 2700 m,extending from the NE to the SW,leading to accumulation of discontinuous drifts with higher sedimentation rates on the eastern side of the channel. The stacking pattern of the layers sug-gests that these drifts propagated southwestward,following the direction of the bottom currents. One sedimentary drift to the southeast of the Dongsha Islands has the highest sedimentation rate of 97cm/ka in the last 12 ka. The sedimentary characteristics of the sediment layers indicate that these bottom currents are most likley caused by the water movement of a branch of the West Pacific Ocean Current,which enters the northern SCS via the Bashi Strait. Once formed,the bottom currents trans-port sediments along the northern slope of SCS southwestward and finally disappear into the central basin of the SCS. Due to the bottom current activity,the deep-sea sedimentary process in the northern SCS is complex.  相似文献   

聚合物钻井液防塌机理的试验研究   总被引：1，自引：0，他引：1       下载免费PDF全文

张红红  徐会文冯哲 《探矿工程》2007,34(1):44-46,61

在试验研究的基础上对比了无机聚合物硅酸盐和有机聚合物——聚乙烯醇（PVA）、部分水解聚丙烯酰胺（PHPA）、非水解聚丙烯酰胺（PAM）和聚丙烯酸钾防塌能力的大小；由试验得出吸附成膜速度的快慢和保护膜的致密程度是决定钻井液体系防塌能力的关键因素；钻井液体系的防塌能力是无机聚合物和有机物质协同作用的结果；部分水解聚丙烯酰胺钻井液体系的防塌能力较非水解聚丙烯酰胺钻井液体系的防塌能力强；Na-CMC和PHP的加入可提高吸附膜的致密性及体系的防塌能力。  相似文献   

奎屯垦区4月地膜增温效应分析   总被引：3，自引：0，他引：3  

康巍  姜智  王飞  徐玲  加那尔别克 《沙漠与绿洲气象(新疆气象)》2007,1(5):51-53

地膜基本效应是增温、增湿,提高棉花出苗期的积温,对增加棉花单产具有重要作用。4月地膜内外最高地温差值很大,而最低地温则差别很小,平均地温的差值相对稳定,膜内、膜外地温差的形成,除与地膜本身的物理特性和当日的气象条件有关,还与土壤热通量有关。  相似文献   

Summer rain events in south-east Asia: Spatial and temporal variations     

Ming Chee Yeung  Sze Chung Lee  Bit Hon Lun  Peter A. Tanner   《Atmospheric Research》2007,86(3-4):241-248

During the summer monsoon period in south-east Asia marine airstreams normally prevail at the south China coast. However, when tropical cyclones approach then polluted airmasses from south-eastern China can impart high ionic concentrations and high acidity to rainwater. This is illustrated by two examples and the small-scale horizontal variations in rainwater composition are minor during these episodes. Since long-term quality-assured studies of the composition of rainwater in south-east Asia are scarce, the results at three sampling sites in Hong Kong during summer monsoon periods are compared with previous data from the same season. The results for the mid- to end-1990's show a similar trend to those for the ambient concentrations of sulphate and nitrate in aerosol in Hong Kong, which show flattened trends from 1995 to 1999. A marked increase in acidity is found in the summer monsoon period of 2004 which is attributed to the greater proportion of approaching cyclone weather systems in the dataset, reflecting both the increased local emission sources and the burgeoning economic growth of the Pearl River Delta Region. Comparison of the rainwater composition with that at other south-east Asian cities during the summer monsoon period shows that it is most acidic in Hong Kong.  相似文献