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191.
Nikolaos P. Nikolaidis Vicki S. Nikolaidis Jerald L. Schnoor 《Aquatic Sciences - Research Across Boundaries》1991,53(4):330-345
Monte-Carlo simulations were used to assess the extent of shortterm alkalinity depressions occuring in Sierra Nevada lakes due to acidic deposition events. The Episodic Event Model (EEM) was used to simulate spring snowmelt events. Snow course data, precipitation data and lake acidification surveys were used to derive values for the EEM parameters. Spring snowmelt events were shown to have great impacts on the water quality of Sierran lakes. Lakes are likely to be most affected by the early-spring snowmelt event because the epilimnion depth is at a minimum, which indicates minimum dilution. Under annual average loading conditions, no Sierran lake has been reported as acidic although 29% of the lakes have alkalinities less than 40 µeq/L indicating a sensitivity to acidification. In simulations of early-spring snowmelt events, using present-day acidic loading conditions, it was estimated 79% ± 9% of the lakes would experience shortterm lake alkalinity depressions to levels less than 40 µeq/L. The results provided by the model simulations are valuable in establishing upper and lower limits on the extent of possible episodic acidification to lake-resources-at-risk. The most critical parameters controlling the magnitude of lake alkalinity depressions during snowmelt episodic events are a) the lake area to watershed area ratio — a measure of input loading, and b) the epilimnion volume — a measure of dilution and mixing. 相似文献
192.
193.
本文以航空γ能谱测量资料为依据,简述了与找钾有关的部分科研成果,建立了第四纪盐湖型钾盐矿床的找矿模式,进而通过对别勒滩、马海等钾盐矿例剖析,说明航空γ能潜测量在寻找第四纪盐湖型钾盐矿床方面确有明显效果。 相似文献
194.
In a study on the diagenesis of carbohydrates in a recent stromatolitic deposit (Solar Lake, Sinai) monosaccharides are quantitated after mild acid hydrolysis and gas chromatographic analysis as alditol acetates. From the depth profiles of the individual monosaccharides relative to the total organic carbon three categories of carbohydrates can be distinguished. The behaviour of the various categories upon burial is discussed in terms of their potential to become a part of the organic matter that survives geological periods. The distribution patterns of especially the mono-O-methyl monosaccharides at various depths are characteristics for the bacterial communities present in the corresponding parts of the sediment column. 相似文献
195.
西藏扎布耶湖ZK91-2钻孔沉积特征与气候环境演化 总被引:12,自引:1,他引:12
扎布耶盐湖位于西藏高原腹地,1991年在其南部干盐滩中钻取了20m深湖相沉积,以5~10cm/个的密度进行高分辨率取样,详细探讨了沉积标志、矿物组合(尤其Mg、Ca、Li碳酸盐)、干旱与潮湿两种气候类型的元素组合等气候环境指标,推导了晚更新世以来该湖区湖面涨缩、水质咸谈及气温高低变化。 相似文献
196.
滆湖沉积物理化特征及磷释放腄 总被引:4,自引:0,他引:4
对滆湖表层底泥、柱状层祥和间隙水进行理化分析,模拟不同条件下的沉积物磷释放。结果表明,0~20cm深度范围内,各项理化指标变化较大;大于2cm后差异较小。当提高沉积物-水体系温度、降低氧含量(或Eh),提高pH及施以水动力作用时,可促进沉积物磷释放进程。无菌条件对磷释放有抑制作用。采用实验室模拟和间隙水浓度扩散模型计算得到的磷总释放量分别为10.65t/a和9.40t/a,其中湖面网围区释放量占全湖总量的28.2~35.4%。建议适度控制网围养殖规模,以减少内源磷污染。 相似文献
197.
Martin Wessels Angela Lenhard Federico Giovanoli Andreas Bollhöfer 《Aquatic Sciences - Research Across Boundaries》1995,57(4):291-304
Sediments in Lake Constance have been dated by radiometric methods and lamination counting. Investigations into the concentrations of lead and zinc in the sediments were carried out to get detailed information about environmental history. Maximum concentrations were found at the beginning of the 1960's. The lead maximum contamination occurred 3 years before the zinc maximum and has an unidentified source. The use of coal, leaded gasoline or the remobilization within the sediment could be excluded to result in the lead maximum. The fluctuations in zinc contamination could be explained with increasing and decreasing pollution (industry, coal burning, building of sewage plants). The greatest fluctuations of both metals occur during periods of great change in the economic history of Germany. 相似文献
198.
青藏高原北缘哈拉湖近800年来 湖泊沉积及其环境意义* 总被引:5,自引:5,他引:5
文章以青藏高原北缘高山祁连山湖泊——哈拉湖作为研究对象,利用放射性核素210 Pb和137 Cs测年资料,通过对此高海拔湖泊沉积碳酸盐氧碳同位素、碳酸盐含量、总有机碳含量、磁化率等环境代用指标的分析,揭示了这一地区近800年来的气候环境变化过程。分析表明哈拉湖记录的气候环境变化经历了3个阶段:1206~1700A.D.环境较为寒冷、湿润,并有持续变湿的趋势;1700~1920A.D.环境由冷湿的状况趋向温暖干旱,1771年之后,环境保持相对稳定;1920~2002A.D.是自1206年以来最为温暖干旱的阶段。 相似文献
199.
岱海14 C测年的现代碳库效应研究* 总被引:2,自引:0,他引:2
碳库效应的复杂性是影响建立湖泊沉积物高精度年代序列的一大障碍。本项研究通过我国内蒙古半干旱区封闭湖泊表层沉积物、湖水、现生沉水植物狐尾藻、现生鲤鱼鱼骨和湖岸表层土壤等一系列样品的14 C年代测定,表明现代岱海确实存在碳库效应。碳库效应年龄因湖水盐度在湖区的不均而有所变化,岱海西部湖区弓坝河径流补给量大,湖水盐度较东部稍低,碳库效应年龄也略小于东部湖区。表层沉积物中有机质包含浮游生物和沉水植物的混合信息,因而其碳库效应年龄较沉水植物年龄轻,岱海湖心表层沉积物碳库效应年龄在2000a左右。这一碳库效应年龄较通过沉积钻孔14 C年龄线性回归获得的年龄偏大,可能的原因是在时间序列上碳库效应并非恒定。 相似文献
200.
Detailed study of two dry depressions in the Baikal rift system: the E–W Khoito Ghol-Tunka-Bistraya depression and the SW–NE Gusinoje–Ivolga depression, aims to provide a better understanding of tectonic control on the intershoulder relief evolution after the rift opened. Both depressions are grabens and both feature a suite of 10–20 km-wide basins alternating with more or less massive highs. Field and laboratory analysis shows that this pattern is of recent tectonic origin and that local breaking-up and subsidence followed the general sinking which originally formed the grabens. The subsidence belts seem to have gradually shifted north and northeastwards. Geomorphological analysis reveals that in both depressions the highs are remnants of a former pediment which was broken up. The young basins display numerous relevant hydrographic anomalies of the secondary channels and a general water-logging. They also suggest that the subsidence belts have gradually shifted north-and northeastwards. In the Gusinoje–Ivolga depression evidence was found of a Plio-Pleistocene river course, parallel to the Selenga river, which was later dismantled by the breaking-up. This depression, parallel to the Baikal rift and belonging to the Mesozoic system of grabens in the Caledonian fold belt, seems to have been included into the general system of rifts during the Pliocene tectonic phase. As for the main hydrographic axes, the Selenga river was set on a Palaeogene-age planation surface before the first tectonic phase and kept its original course. The Irkut river flowed in the Khoito Gol–Tunka–Bistraya depression after the first tectonic phase and was not affected by the later breaking-up. In contrast, the secondary drainage network is largely discordant. Despite their different geotectonic contexts, the two depressions show a similar development of relief pattern,which poses the question of the style of rift dynamics after the main Pliocene tectonic phase. 相似文献