西藏自治区洛扎县冰湖溃决危险度评价   总被引：7，自引：1，他引：7  

刘淑珍  李辉霞  鄢燕  柴宗新  杜少平 《山地学报》2003,21(Z1):128-132

西藏自治区湖泊星罗棋布,在高山极高山地区分布大量冰湖,受各种因素的影响,有时会产生冰湖溃决并形成灾害。本文根据最新TM遥感影像对西藏自治区洛扎县283个冰湖进行了初步评价。依据冰湖类型、规模、后方现代冰川与冰湖的距离及冰湖离居民地、公路等设施的距离等,将冰湖溃决分为高危险度、中危险度及低危险度。并针对高危险度的冰湖提出防护对策。  相似文献   

Salt tolerance of Microcoleus vaginatus Gom., a cyanobacterium isolated from desert algal crust, was enhanced by exogenous carbohydrates     

Lanzhou Chen  Dunhai Li  Yongding Liu 《Journal of Arid Environments》2003,55(4):381

Microcoleus vaginatus isolated from a desert algal crust of Shapotou was cultured in BG-11 medium containing 0.2 mol l⁻¹ NaCl or 0.2 mol l⁻¹ NaCl plus 100 mg l⁻¹ sucrose, extracellular polymeric substances (EPS) or hot water-soluble polysaccharides (HWP), respectively. Photosynthetic oxygen evolution rates, photosystem II activity (Fv/Fm) and dark respiration of NaCl-stressed cells were enhanced significantly by the added sucrose or EPS under salt stress conditions (0.2 mol l⁻¹ NaCl). Compared with cells treated with salt alone, sodium contents in cells reduced significantly; the content of cellular total carbohydrate did not change, and intracellular sucrose, water-soluble sugar increased significantly following the addition of exogenous carbohydrates. Sucrose synthase (SS) activity of NaCl-stressed cells increased following the addition of sucrose, and sucrose phosphate synthase (SPS) activity of NaCl-stressed cells increased following the addition of exogenous sucrose, EPS or HWP compared with cells stressed with NaCl only. The results suggested that the extruded EPS might be re-absorbed by cells of M. vaginatus as carbon source, they could increase salt tolerance of M. vaginatus through the changes of carbohydrate metabolism and the selective uptake of sodium ions.  相似文献   

湖泊水下数字高程模型建模方法及应用模型     

邓雪清  张永生  李波  班业胜 《华东地质学院学报》2003,26(2):192-196

介绍了当前湖泊水下地形测量的一般方法和作业过程。针对逐点插入构建不规则三角网算法，本文提出了效率改正算法和格网索引号快速计算算法。基于不规则三角网，给出了湖泊水下数字高程模型的一般应用模型——任意点高程计算、填挖方计算模型及等深线计算模型。  相似文献   

Isotopic Tracing of Trophication Processes over the Last Millennia on Lake Chenghai     

吴敬禄  王苏民  夏威岚 《中国地球化学学报》2003,22(3):271-279

Multi-parameter studies (stable isotopes in carbonate and organic matter, pigment,organic carbon and nitrogen contents) from a 660-yr continuous sediment core from Lake Cheng-hai, a closed, eutropic lake in southern China, provide information on lake historical eutrophi-cation. During the last 660 years, great changes have taken place in productivity and eutrophi-cation of Lake Chenghai in response to human activities. In 1690, the productivity of the lakebegan to increase as Lake Chenghai became closed from agriculture in the lake‘‘ s watershed. In 1942, Lake Chenghai evolved to eutrophic state, marked by an increase in organic carbon, ni-trogen, CaC03, pigment contents and obvious negative values of stable isotopes, which is more or less simultaneous with the large-scale population immigration during the period. In 1984, in-tensive human activities induced modern lacustrine productivity and eutrophic level. Human-in-duced trophic changes during the past few decades have affected the Lake Chenghai ecosystem tosuch an extent that it has never experienced before in the last 660 years.  相似文献   

莱州湾南岸平原古湖泊消亡原因初探          下载免费PDF全文

张维英  韩美  李艳红 《古地理学报》2003,5(2):224-231

莱州湾南岸平原是指西起小清河口，东至胶莱河口的广大沿岸地区，这一地区近年来是我国工农业发展较快的地区，也是我国地下咸水入侵较为严重的地区。历史上，莱州湾南岸平原地区曾有一些湖泊存在，如巨淀湖、黑冢泊、别画湖，但现在早已荡然无存了。研究这些古湖泊的消亡原因对于恢复该区古地理环境以及确立湖迹区今后的发展方向具有十分重要的意义。本文运用查阅历史文献、地层剖面分析、地名考证、遥感解译等多种方法，对莱州湾南岸古湖泊的消亡原因进行了研究与分析，并指出该区古湖泊消亡的原因是气候变干、河流变迁、人类活动影响等，其中气候变化是古湖泊消亡的根本原因，河流变迁是古湖泊消亡的直接原因，而人类活动则加速了古湖泊消亡的进程。  相似文献   

湖泊纹层状沉积物的同生期变化研究述评     

王冠民  钟建华  马在平 《世界地质》2003,22(3):231-236

湖泊纹层状沉积物是在湖水分层的条件下缓慢沉积的。这些沉积物在沉积以后可能会发生一些同生期的改造作用，如季节性湖流的微弱冲刷、湖水中溶解氧对有机质的氧化、硫酸盐还原作用对有机质的氧化和硫化物的形成、有机质分解形成的偏酸性底层湖水对碳酸盐的溶解和磷的迁移造成的藻类勃发等，使纹层在成分、结构和构造方面发生一些变化。在对纹层进行古气候、古环境恢复的时候，这些同生期的变化不能被忽视。对这些变化的研究有助于对古气候、古湖水沉积环境的正确认识。  相似文献   

呵叻盆地钾镁盐矿沉积特征及成因探讨   总被引：11，自引：1，他引：11  

钟维敷  李志伟  单卫国 《云南地质》2003,22(2):142-151

充分收集已有地质成果基础上，分析呵叻盆地沉积特征和成钾条件。详细论述呵叻盆地钾盐矿的赋存条件和产出特征，初步探讨钾盐矿的形成机理。  相似文献   

A review of the physics and ecological implications of the thermal bar circulation     

Paul R. Holland  Anthony Kay 《Limnologica》2003,33(3):153-162

Following recent applications of numerical modelling and remote sensing to the thermal bar phenomenon, this paper seeks to review the current state of knowledge on the effect of its circulation on lacustrine plankton ecosystems. After summarising the literature on thermal bar hydrodynamics, a thorough review is made of all plankton observations taken in the presence of a thermal bar. Two distinct plankton growth regimes are found, one with production favoured throughout the inshore region and another with a maximum in plankton biomass near the position of the thermal bar. Possible explanations for the observed distributions are then discussed, with reference to numerical modelling studies, and the scope for future study of this interdisciplinary topic is outlined.  相似文献   

Hydrologic and geomorphic effects of temporary ice‐dammed lake formation during jökulhlaups     

Matthew J. Roberts  Fiona S. Tweed  Andrew J. Russell   skar Knudsen  Timothy D. Harris 《地球表面变化过程与地形》2003,28(7):723-737

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西藏纳木错晚更新世以来湖面变化和藏北高原古大湖的演化     

朱大岗  赵希涛  孟宪刚  吴中海  邵兆刚  马志邦  杨朝斌  王建平 《地质通报》2003,(Z1)

根据西藏纳木错及邻区发现的多处湖岸阶地和高位湖相沉积,确定了藏北高原古大湖的存在。水准测量表明,在纳木错沿岸发育了6级湖岸阶地,以及拔湖48～139.2m的高位湖相沉积;在拔湖26m以下,发育有8～30条湖岸堤;一条明显的湖蚀凹槽则集中出现在拔湖17.5～19.8m的高度上,与纳木错和仁错的分水垭口的高度相当。纳木错沿岸和邻区湖相或湖滨相沉积物的铀系年龄测定表明,高位湖相沉积形成于115.9～71.8kaB.P.的晚更新世早期;第6至第2级阶地形成于53.7～28.2kaB.P.的晚更新世中晚期;与湖蚀凹槽相当的湖滨相沉积则稍早于29.3kaB.P.;第2至第1级阶地,14C测定结果为2350～10390aB.P.。  相似文献