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艾比湖干涸湖床风扬粉尘的发生及其潜在扩散特征研究
葛拥哓
学位类型博士
导师吉力力·阿不都外力
2016
学位授予单位中国科学院大学
学位授予地点北京
学位专业自然地理学
关键词风蚀 干涸湖床 风尘系统 尾闾湖 艾比湖
摘要干旱区湖泊是干旱区生态系统重要组成部分,对气候与环境变化具有高度敏感性。气候变化背景下,不断增强的人类活动强烈干扰干旱区自然生态系统,出现了超出了生态安全阈值导致的环境退化,致使下游河道断流、湿地消失、湖泊不断萎缩,加速消亡。干旱区尾闾湖的萎缩甚至干涸,导致干涸湖床风扬粉尘(浮尘、扬沙、沙尘暴)事件频发,造成区域环境恶化。 本研究针对深入理解干旱区尾闾湖干涸湖床风扬粉尘发生机理及扩散特征的科学目标,围绕影响干涸湖床风扬粉尘发生的关键参数、控制粉尘释放的关键过程和粉尘扩散的关键特征三个问题,选择新疆艾比湖干涸湖床为重点研究区,通过数值分析、定位观测和模型模拟,开展了地气界面地表参数和空气动力学参数变化特征、近地表层风扬粉尘发生过程的空间差异、大气边界层粉尘扩散路径和范围的定量研究,分析了风扬粉尘发生的主要影响因素,深入揭示了风扬粉尘发生的区域差异,明确了粉尘潜在扩散范围和主要路径,科学阐释了干旱区湖泊演变过程中现代风扬粉尘发生特征,提高了对干涸湖床这一重要粉尘源区的理解和认识。获得的主要结论如下: (1)晚更新世以来的湖岸线内不同地表覆盖类型的微团粒分布、空气动力学粗糙度、起动摩阻风速和摩阻风速表现出显著的区域差异。刚毛柽柳荒漠、白梭梭荒漠、多枝柽柳荒漠、无植被区域分别由极细砂和中砂群体2个群体组成,其余由极细砂群体、中砂群体和粗砂群体3个群体组成。东北部的白梭梭荒漠和红砂荒漠的空气动力学粗糙度可达5.15 cm和5.45cm,耕地和无植被覆盖地区的空气动力学粗糙度分别为0.003 cm和0.001 cm。西北部的琐琐砾漠、东南部芦苇草甸的起动摩阻风速值最大,分别为127.53 cm/s和167.47 cm/s,是10种地表覆盖类型中较大的。红砂荒漠的摩阻风速为71.4 cm/s,为10种地表覆盖类型中摩阻风速的最大值。 (2)DPM模型模拟结果表明,位于艾比湖干涸湖床西北部的琐琐砾漠和北部的红砂荒漠由于较粗的粒径组成和较大的起动摩阻风速导致很难释放粉尘。在没有水分和植被的影响下,无植被覆盖区域的粉尘释放通量则达到了153 g/(km2·s),耕地在无作物种植的时期的粉尘释放通量达到了83.8 g/(km2·s),艾比湖干涸湖床开荒的耕地已经成为该地区一个重要的粉尘源区。 (3)艾比湖干涸湖床的粉尘潜在扩散具有显著的季节分异:春季和夏季的潜在扩散范围最大,秋季和冬季1000 m以下扩散范围较小,1000 m高度以上低密度气团轨迹扩散范围较大;艾比湖干涸湖床不同季节的粉尘潜在扩散表现出明显的方向性:风扬粉尘主要有两个扩散通道,即东南方向和东北方向。春季和夏季的主要扩散方向为东南方向,主要影响近源区,可潜在影响中国大部分地区以及俄罗斯部分地区,然而,秋季和冬季的主要扩散方向在较低层为东北方向,500 m以上时方向转向东,主要影响中亚和俄罗斯部分地区。艾比湖干涸湖床的大量的含盐粉尘主要影响区域为近源区,包括精河县、博乐市等人口聚集区。 (4)通过与艾比湖处于同一纬度带的咸海、柴窝堡湖等亚洲干旱区典型尾闾湖泊MODIS和MISR气溶胶光学厚度特征及扩散特征的比较分析表明,亚洲中部干旱区干涸湖床有潜力释放大量的粉尘。作为气溶胶长期悬浮于大气中,除造成近源区空气污染,增加大气浮尘和大气气溶胶之外,含盐粉尘在天山山区沉降,与气候变化效应叠加会显著的加速雪冰消融。适宜的气象条件下,亚洲中部干旱区干涸湖床释放的大量的含盐粉尘在气流携带下可以长时间远距离输送,潜在影响范围远超想象。作为干旱区典型的下垫面,亚洲中部干旱区干涸湖床是亚洲中部干旱区风尘系统的重要源区和重要组成部分,是全球变化背景下风尘系统研究忽视的重大问题。作为亚洲风尘系统研究的重要内容之一,对干涸湖床的粉尘释放的研究无疑会对亚洲风尘系统研究提供一定的借鉴意义。
其他摘要Lake in arid land, which plays an incredible role in maintaining of the regional ecosystem balance, is an important part of the arid ecosystem and is highly sensitive to climate change and environment evolution. In the context of climate change, intense human activity leaded lakes in arid land to shrink and even dry up, which caused to the unpredictable negative dynamics of lakes beyond safety thresholds, and resulted in serious environmental degradation effect. In present time, some ecological security issues became actual, including drying of rivers, declining of natural oases, disappearance of wetlands, shrinkage of lakes, followed by environmental degradation and serious desertification. As a result, frequent dust storms (floating dust, blowing sand and dust storm) occurred. This study is aimed to understand the mechanism of eolian dust from the playa of Ebinur lake and its diffusion characteristics in the atmosphere boundary layer, three key questions are urgent to be answered, i.e., how do the key parameters that affect the eolian dust change? What is the spatial pattern of key processes that control the dust emission from the playa? In addition, what are the main features of dust spread in the atmosphere? Within the selected Ebinur lake playa, quantitative studies were implemented through statistical analysis, positioning observations and model simulations to gain the land surface parameters and aerodynamic parameters and their variation, to understand spatial differences of the process that control the dust generation near the surface, and to define the pathways and range of dust suspended in the atmospheric boundary layer. This study identified the main factors influencing the occurrence of eolian dust, revealed regional differences of eolian dust generation in complex underlying surface thoroughly, interpreted dust emission characteristics and its tranport characteristics scientifically, and increased the understanding and awareness of the important dust source in the evolution process of lakes in arid land. Meanwhile, results of this project could provide a reference for tail-end lake area to take effective measures to defense eolian dust, as well as provide a scientific basis for construction and management of ecosystems in the tail-end lake area. Main conclusions drawn are listed below: (1) Dry aggregates, aerodynamic roughness length, threshold friction velocity and friction velocity of different land cover types exhibit notifying different characteristics within shoreline since the late Pleistocene. Tamarix hispida desert, Haloxylon persicum desert, Tamarix ramosissima desert, and bareland compose by very fine sand and medium sand populaions; others compose by very fine sand, medium sand and coarse sand populaions. Aerodynamic roughness length of Haloxylon Persicum desert and Reaumuria songarica desert in the northeast of playa of Ebinur Lake reach up to 5.15 cm and 5.45 cm, while the smallest is distributed in the areas dominored by farmland and bareland with aerodynamic roughness 0.003 cm and 0.001 cm, respectively. Therefore, bareland and farmland has the potential to release large amounts of dust in the absence of moisture and vegetation effects. Threshold friction velocity of Haloxylon gravel desert in northwest and Phragmites communis meadow in southeast are 127.53 cm/s and 167.47 cm/s, respectively. This is greater than that of other surface types. The largest friction velocity is found in Reaumuria songarica desert with a value of 71.4 cm/s. (2) Dust production model (DPM) model was used to simulate the dust fluxes from different land covers within the dry lakebed of Ebinur Lake. Those results shown that Haloxylon gravel desert located in the northwest and Reaumuria songarica desert in the north with the coarse particle size composition and a larger threshold friction velocity makes it difficult to release dust. Dust fluxes of bareland in the northwest can reach 153g/(km2·s) in the absence of moisture and vegetation. Farmland gains a dust emission flux reaching 83.8 g/(km2·s), which indicates that farmland has become an important source of dust in this region. (3) Potential transport of dust from the playa has significant seasonal differentiation. Potential transport get maximum distance in spring and summer, while distance in autumn and winter is less lower 1000 meter above ground level, and low-density air mass trajectory can be transport for wide range above 1000 meter. Potential transport of dust exhibits clear direction in different seasons. There are two main transport pathways for the dust from the playa, namely the southeast and north-northeast. The main transport direction is southeast in spring and summer, mainly affecting the source region; it could potentially affect most parts of China and parts of Russia. However, the main transport direction in autumn and winter in the lower layer is to the northeast, and steering to east direction above 500 m, mainly affects Central Asia and parts of Russia. The main affected area is near the source region, including Jinghe and Bole. (4) This study takes comparative analysis on changes characteristics of aerosol optical depth derived from MODIS and MISR and transport characteristics of dust from the playa of Ebinur Lake, Aral Sea, and Chaiwopu Lake in the arid central Asia within the same latitude band. The results show the dry lakebed in arid Central Asia has the potential to release large amounts of dust and salt dust with a extremely high content of fine particle sulfate, chloride and heavy metal elements, which is more poisonous than dust and will cause air pollution and increase atmospheric aerosols for long-term suspension in the atmosphere. In addition, salt dust settling in the Tianshan Mountains, coupling with climate change will be significantly accelerates the melting of snow and ice. Under suitable weather conditions, a lot of dust from the dried lakebed of tail-end lakes in the arid Central Asia can be transported for long-distance, which is far beyond imagination. It is suggested that dry lakebed, as a typical land surface in the arid Central Asia, is an important source and important part of eolian dust and sediments. As one of the elements of eolian dust and sediments in arid central Asia, the study of the release of dust from dry lakebed will undoubtedly provide some references for the dust system in arid central Asia.
学科领域自然地理学
语种中文
文献类型学位论文
条目标识符http://ir.xjlas.org/handle/365004/14689
专题研究系统_荒漠环境研究室
作者单位中科院新疆生态与地理研究所
推荐引用方式
GB/T 7714
葛拥哓. 艾比湖干涸湖床风扬粉尘的发生及其潜在扩散特征研究[D]. 北京. 中国科学院大学,2016.
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