青藏高原湖泊表层沉积物粒度和元素地球化学特征研究

发布时间：2018-05-21 10:10

本文选题：可可西里湖泊 + 表层沉积物　；参考：《兰州大学》2015年硕士论文

【摘要】：在古气候演变重建过程中,环境替代指标的认识是其中重要的研究内容之一。目前记录海洋、湖泊、冰川、黄土等环境信息载体的古环境指标主要有地球化学、地球生态、地球物理等,其中沉积物的元素组成特征是应用较广的指标之一。但多年的实践证明,元素作为古环境重建的地球化学指标,在指示环境意义方面仍存在许多亟待解决的问题。青藏高原因其独特的地理位置和地质背景,对东亚季风的形成以及全球气候系统具有特殊的影响作用；其不仅有类型众多的湖泊,而且湖泊沉积物记录了丰富的气候变化信息,对认识东亚季风的形成机理、全球的古气候系统演化具有重要意义。因此,本文以青藏高原北缘可可西里地区现代湖泊(水洼)为研究对象,通过对沉积物中元素和湖泊水介质、类型等综合分析,利用研究区淡水湖、微咸水湖、咸水湖及盐湖中表层沉积物粒度参数特征、矿物组成、元素地球化学特征,探讨金属元素的迁移富集规律,从而深入了解元素指标的环境指示意义,对古环境重建指标提供一些基础背景资料和理论。主要结论如下：1、研究区淡水湖泊主要有取样点kkx1-5和kkx1-13两个湖泊。粒径大于63μm的砂在湖泊中占沉积物总量的70-90%左右,以滚动及跳跃方式迁移,且主要以跳跃迁移方式为主：粉砂(4-64 μm)占表层沉积物总量的20-10%左右,以悬浮迁移为主,部分粒径较大的粉砂表现出以跳跃方式迁移的特性；湖泊中粘土组分含量较少,主要以悬浮方式迁移。粒度组成特征反映了青藏高原湖泊表层沉积物或为多源的特性,研究区流域总体上为水动力强的暂时性水流。2、微咸水湖泊在研究区分布比例较多,按照湖泊表层沉积物粒度参数特征,将研究区微咸水湖泊分为三大类：第一类湖泊主要包括kkx1-4,7,25取样点处的湖泊。粒径大于63μm的粗粒占表层沉积物总量的70%左右,主要以滚动方式迁移；粉砂在湖泊中的迁移以跳跃方式为主,约占表层沉积物总量的25%左右；粘土主要表现为悬浮迁移,在湖泊中含量分布较少。第二类湖泊包括kkx1-2,9,10,12,14,22,24,26取样点处共8个湖泊,粒径大于350μm的组分主要以滚动方式迁移至湖泊,在湖泊表层沉积物中约占10%左右；粒径处于63-350 gm的沉积物约占沉积物总量的40-70%,以跳跃方式迁移；粉砂主要以跳跃和悬浮方式迁移；粘土在此类湖泊中含量较少,约10%左右,主要通过悬浮方式进行迁移。第三类湖泊主要包括取样点kkxl-3,11,15,21,23,27共六个湖泊。其中,粒径大于250μm的组分主要以滚动方式迁移,占表层沉积物总量的10%左右；粒径位于63-250μm的组分主要通过滚动和跳跃的方式进行迁移,在湖泊表层沉积物中占有较大的比例,约20-30%；粉砂主要是以悬浮和跳跃的方式进行迁移,占表层沉积物总量的50%左右；粘土主要以悬浮方式迁移至湖泊,在湖泊环境中占有约20%。3、咸水湖主要包括kkxl-18,19两个湖泊,以滚动方式进入两湖泊的组分较少,占其表层沉积物总量的5%左右,其颗粒物粒径大于250μm；跳跃迁移的组分在kkxl-18湖泊中占其表层沉积物总量的85%左右,在kkxl-19湖泊中约占表层沉积物总量的15%；以悬浮方式迁移的组分,在kkxl-18湖泊中占表层沉积物总量的10%左右,在kkxl-19湖泊表层沉积物中占有80%左右。4、在研究区湖泊表层沉积物中,元素Ca、Mg、Sr的分布受湖泊环境中碳酸盐分布的影响作用明显；元素Si主要受石英颗粒分布的影响,水动力的变化控制了其在湖泊内的分布。常微量元素的分布受沉积物粒径组分的影响较大。5、对各湖泊表层沉积物中常微量元素UCC标准化后,研究区湖泊表层沉积物中As元素在各类湖泊中异常富集,其次Ca、Mg、Cr、Pb、V等元素富集,而K、Na元素在各类湖泊中明显亏损,元素Al和Rb在淡水湖表层沉积物中亏损,而在微咸水-咸水表层沉积物中则保持平衡。说明了青藏高原湖泊的地表径流补给较快、水体较冷,化学风化作用较弱。湖泊水体在演化过程中元素K、Na因溶解性强而长期存在,湖泊向高盐度方向发展。
[Abstract]:In the process of paleoclimate evolution reconstruction, the understanding of environmental alternative indicators is one of the most important research contents. The paleoenvironmental indicators that record marine, lake, glacier, loess and other environmental information carriers are mainly geochemistry, geo ecology and Geophysics, among which the characteristics of the element composition of the sediments are one of the more widely used indicators. Many years of practice have proved that as a geochemical index for the reconstruction of the paleoenvironment, there are still many problems to be solved in the direction of the environmental significance. The unique geographical location and geological background of the Qinghai Tibet Plateau have special effects on the formation of the East Asian monsoon and the global climate system; it not only has many types of lakes. And lake sediments have recorded abundant information on climate change, which is of great significance to the understanding of the formation mechanism of the East Asian monsoon and the evolution of the global paleoclimate system. Therefore, this paper takes the modern Lakes (water pools) in the cocoa Xili area of the northern margin of the Qinghai Tibet Plateau as the research object, through the synthesis of the elements and lakes in the sediments and the types of the lakes. By analyzing the characteristics of the grain size parameters, mineral composition and elemental geochemical characteristics of the surface sediments in the freshwater lake, brackish water lake, saltwater lake and Saline Lake, the migration and enrichment of metal elements is discussed, so as to understand the environmental indicator significance of the element index, and provide some basic background data and theory for the reconstruction of the ancient environment. The main conclusions are as follows: 1, the main freshwater lakes in the study area are two lakes of kkx1-5 and kkx1-13. The sand with a particle size of 63 mu m is about 70-90% of the total amount of sediment in the lake, and is moved by the way of rolling and jumping, and mainly in the way of jumping migration. The silt (4-64 mu m) accounts for about 20-10% of the total amount of the surface sediments, and is suspended in suspension. Mainly, the silt with large part of grain size is characterized by leaping. The content of clay components in the lake is less, mainly by suspension mode. The characteristics of the grain size composition reflect the characteristics of the surface sediments of the Qinghai Tibet plateau lake or the characteristics of multi source. The basin in the study area is a temporary water.2 with a strong hydrodynamic force, and the brackish water lakes are in the lake in the study area. The distribution ratio of the study area is more. According to the characteristics of the grain size parameters of the surface sediments of the lake, the brackish water lakes in the study area are divided into three major categories: the first kind of lake mainly includes the lake at the kkx1-4,7,25 sampling point. The coarse grains with the grain size of 63 Mu account for about 70% of the total amount of the surface sediments, mainly by rolling mode, and the migration of silt in the lake There is about 25% of the total amount of surface sediments in the way of jumping. Clay mainly shows suspended migration, and the content distribution is less in the lake. The second kinds of lakes include 8 lakes at kkx1-2,9,10,12,14,22,24,26 sampling point, and the components of the grain size greater than 350 Mu are mainly migrated to the lakes by the rolling square, and about the surface sediments of the lake. About 10%, the sediment with a diameter of 63-350 GM, which accounts for about 40-70% of the total amount of sediment, is migrated in a hopping way, and the silt is mainly transported by leaping and leaping, and clay is less in this kind of lake, about 10%, mainly by suspension mode. The third types of Lakes mainly include a total of six sampling points of kkxl-3,11,15,21,23,27. Among them, the components of the particle size greater than 250 u m are mainly migrated by rolling, accounting for about 10% of the total amount of the surface sediments, and the components with a diameter of 63-250 mu m are mainly migrated by rolling and jumping, which occupies a large proportion in the surface sediments of the lake, about 20-30%, and the silt is mainly moved by levitating and jumping. Shifting, accounting for about 50% of the total surface sediment total, clay mainly migrated to lakes in a suspension mode, occupied about 20%.3 in the lake environment, mainly including two lakes in the saltwater lake, and less in the two lakes in the rolling way, accounting for 5% left right of the total surface sediments, and the particle size of its particles was more than 250 mu m; the jump migration group was more than 250. The kkxl-18 Lake accounts for about 85% of the total surface sediments in the lake and about 15% of the total surface sediments in the kkxl-19 lake. The component of the suspended mode is about 10% of the total surface sediments in the kkxl-18 lake, and about 80%.4 in the surface sediments of the kkxl-19 lake. In the surface sediments of the study area, the elements of the lake surface sediments are in the study area. The distribution of Ca, Mg and Sr is influenced by the distribution of carbonate in the lake environment; element Si is mainly influenced by the distribution of quartz particles. The variation of hydrodynamic forces control its distribution in the lake. The distribution of the trace elements is greatly influenced by the grain size of the sediments, and the normal trace elements UCC in the surface sediments of each lake are standardized after.5. The As elements in the lake surface sediments of the study area are enriched in various lakes, followed by the enrichment of Ca, Mg, Cr, Pb, V and other elements, while K, Na elements are obviously lost in all kinds of lakes, and the elements Al and Rb are lost in the surface sediments of fresh water lake, while the balance in the salt water and salt water surface sediments shows the surface runoff of the Qinghai Tibet plateau lake. The recharge is faster, the water body is cold and the chemical weathering is weak. In the evolution process of the lake water, the elements K and Na exist for a long time because of the strong solubility, and the lake develops to the high salinity direction.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P595;P343.3

【参考文献】