Hydrogeochemistry of seasonal variation of Urmia Salt Lake     

《中国地球化学学报》2006,25(B08):193-194

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The Record of an Extreme Flood in the Sediments of Montane Lillooet Lake, British Columbia: Implications for Paleoenvironmental Assessment     

Robert Gilbert  Sarah Crookshanks  Kyle R. Hodder  John Spagnol  Roland B. Stull 《Journal of Paleolimnology》2006,35(4):737-745

Severe rainfall in mid October, 2003 produced the largest floods in almost a century of record on rivers in the Cordillera of southwestern British Columbia. Sediment deposited in Lillooet Lake as a result of this event is clearly distinguished by stratigraphy, colour, texture, magnetic properties, and organic content. Each of these physical properties is related to the lacustrine processes, especially turbid underflow, that distributed the sediment through the lake. The flood, which lasted less than a week, delivered 8–12 times the amount of sediment that accumulates in most entire years in the deepest, central parts of the lake. Recognition of events of this type in the stratigraphic record offers a means of assessing the changing nature of extreme hydroclimatic events, and their relation to more ubiquitous, lower-energy processes.  相似文献   

Physiography and tectonic setting of the subglacial lake district between Vostok and Belgica subglacial highlands (Antarctica)     

I. E. Tabacco  P. Cianfarra  A. Forieri  F. Salvini  A. Zirizotti 《Geophysical Journal International》2006,165(3):1029-1040

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强水动力湖泊夏季分层期氮的生物地球化学循环初步研究:以贵州红枫湖南湖为例   总被引：9，自引：1，他引：9  

肖化云  刘丛强  李思亮  王仕禄 《地球化学》2002,31(6):571-576

湖泊在夏季由于藻类生长而消耗大量硝酸盐,水体硝酸盐含量一般要低于春季。而红枫湖南湖水体硝酸盐含量却高于春季(比平均含量高0.83mg/L),说明尚有其他重要的硝酸盐来源。据估算,南湖水体硝酸盐含量升高0.83mg/L约需要1.66×105kg硝酸盐,另外有约10.1×105kg硝酸盐随下泻水输出南湖,再加上夏季藻类生长(生产的chla量约为640kg)所消耗的硝酸盐3.52×105kg,共消耗硝酸盐15.28×105kg。扣除河流输入的4.42×105kg硝酸盐,南湖尚存在约10.86×105kg硝酸盐的亏空。利用氮稳定同位素示踪技术,结合硝酸盐及叶绿素a(chla)含量、溶解氧(DO)等的变化,认为这部分硝酸盐来自湖泊中下部(斜温层)有机质的大量矿化(硝化),是水动力驱动高DO的上部水体下沉从而引起下部有机质(硝化)的结果。南湖这种强水动力湖泊整个夏季分层期氮的生物地球化学循环是斜温层有机质矿化(硝化)释放硝酸盐和变温层藻类生长同化硝酸盐为有机质同时发生的特殊类型。  相似文献   

灌淤土壤可溶性盐分空间变异性与棉花生长关系研究   总被引：8，自引：3，他引：8  

杨玉玲  田长彦  盛建东  文启凯 《干旱区地理》2002,25(4):329-335

运用地统计学方法，在灌淤土壤上进行了棉田土壤可溶性盐分的空间变异规律与棉花生长关系系统研究。传统统计学分析表明土壤盐分测试数据基本符合正态分布；在一定取样间距下，土壤可溶性盐分的田间合理取样数目为27。半方差分析显示：土壤可溶性盐分具中等的水平变异性，但随着聚样深度的增加未表现出明显的垂直变异特性；随着棉花的生长发育，土壤可溶性盐分呈现出逐渐减弱的时间变异规律，采用直线或曲线拟合方程估计了可溶性盐分的半方差图及其参数，并绘制了其相应的等值线图。土壤可溶性盐分与棉花产量之间的相关分析表明：可溶性盐分含量与棉花产量之间呈显著负相关关系，且花铃期的相关性较播前显著。研究结果为提高田间试验有效性以及盐渍化土壤改良提供了科学依据与基础资料。  相似文献   

青海省盐湖钾、镁、锂盐资源开发利用探讨   总被引：4，自引：4，他引：4       下载免费PDF全文

严军  黄小良 《盐湖研究》2002,10(4):63-69

论述了青海省盐湖资源中钾、镁、锂盐工业的资源状况、生产现状以及开发利用的迫切性 ,并对钾、镁、锂盐资源的综合利用进行了探讨  相似文献   

腾格里沙漠地区盐湖钾盐资源特征   总被引：2，自引：2，他引：2       下载免费PDF全文

李博昀  刘振敏  徐少康  刘国庆 《盐湖研究》2002,10(1):18-23

腾格里沙漠地区盐湖众多 ,以沉积石盐和芒硝为主 ,并赋存有丰富的晶间卤水 ,卤水中K+含量较高 ,在调查的 1 7个盐湖中有 1 2个盐湖KCl含量达到综合利用品位或工业边界品位。通过地质调查、遥感及航空γ能谱测量资料解译 ,本区多数盐湖具有相似的成钾条件 ,形成 4个成钾远景区 ,具有一定的找钾前景  相似文献   

A high-resolution diatom reconstruction between 21,000 and 17,4000 14C yr BP from the southern Bolivian Altiplano (18–23°S)     

Florence Sylvestre 《Journal of Paleolimnology》2002,27(1):45-57

A diatom study of lacustrine sediments in the southern part of the Bolivian Altiplano (Salar of Coipasa) provides a continuous record of the period 21,000–17,500 ¹⁴C yr BP. Constrained by seven AMS ¹⁴C dates, this record provides evidence that the Coipasa basin was filled by a shallow body of water during this time. Diatom/salinity and diatom/ionic composition transfer functions indicate that the lake was saline, dominated by sodium-chloride throughout all the period.A comparison with regional data shows that Lake Titicaca could not have overflowed towards the southern Bolivian Altiplano at that time. As this dry phase was not registered in Lake Coipasa, this lake was probably supplied by winter precipitation originating from the Pacific. But, recent data from the deep basin of Lake Titicaca show that the lake-level was higher during this time interval, and the question arises whether precipitation from Atlantic and Amazonia sources could have played an important role on the Altiplano during the Last Glacial Maximum (LGM). This hypothesis needs to match other available paleoclimatic data from the lowlands of tropical South America, where there is evidence that during the LGM, conditions were drier than today. Global climate simulations suggest a positive P-E on the Altiplano, due to a strong cooling, reducing evaporative demand more than any increase in precipitations. An increase of winter precipitation from the Pacific is in agreement with data from the Chilean coast showing a northward locations of the Westerlies during the LGM. This paleoclimatic hypothesis is also in agreement with a coupled ocean-atmosphere model, which indicates weaker summer precipitation and stronger winter precipitation in the tropical areas.  相似文献   

Human Modification of the Geomorphically Unstable Salt River in Metropolitan Phoenix     

Martin Roberge 《The Professional geographer》2002,54(2):175-189

In‐stream gravel mining, massive bridge piers, and channelization have all contributed to the geomorphic instability of the Lower Salt River channel in Arizona. Dam closure, changing dam operating rules, and the frequent modification of the channel bed have decreased our ability to predict the Salt River hydrology. Engineering practice has adapted to this situation and to a public that is increasingly intolerant of service disruptions by constructing larger bridges and extending levees. Building these larger structures may be counterproductive; future construction should not constrict the channel and should re‐establish a braided river to decrease the energy available to the system.  相似文献   

Representation of fish communities by scale sub-fossils in shallow lakes: implications for inferring percid–cyprinid shifts     

T.A. Davidson  C.D. Sayer  M.R. Perrow  M.L. Tomlinson 《Journal of Paleolimnology》2003,30(4):441-449

The palaeoecological potential of fish scales was assessed by comparing contemporary population data with scale remains obtained from littoral (n = 10) and open water (n = 10) surface sediment samples in two English shallow lakes, Selbrigg Pond and Cockshoot Broad. Scales and/or scale fragments were present, in low numbers (<20 per 100 cm³ wet sediment) in 34 of 40 sediment samples. In accordance with fish population data, higher densities of scale remains were found in Selbrigg compared to Cockshoot, and in littoral compared to open water samples. Taxonomic difficulties, exacerbated by scale fragmentation, made it impossible to assign the majority of remains to individual species. Most remains could, however, be placed into one of two groups: (i) percids – represented by both scales and scale fragments; and (ii) cyprinids – largely represented by scale fragments. To allow comparison of fish population and sedimentary scale data, both were converted to percentages of the aggregate percid–cyprinid total. Whole scales recovered were almost exclusively percid (45 of 48), thus bore little resemblance to the contemporary fish data. Nevertheless, percentages of scale fragments (Selbrigg: 34 and 66%; Cockshoot: 13 and 87% percid and cyprinid, respectively) and of whole scales and fragments combined (Selbrigg: 54 and 46%; Cockshoot: 46 and 54% percid and cyprinid, respectively) reflected the presence of the numerically dominant fish groups and the broad inter-site differences in their relative abundance (Selbrigg: 36 and 64%; Cockshoot: 10 and 90% percid and cyprinid, respectively). A running mean of scales per sediment volume indicated that some 400 cm³ of sediment was required to accurately characterise the remains present. This study suggests that, with the appropriate methodological considerations (e.g., collection of large sediment samples), fish scale remains may be used to determine the past presence–absence and relative abundance of percid and cyprinid species. As such, this technique may be a valuable supplementary tool for establishing longer-term changes in the fish communities of shallow lakes.  相似文献