地理学报 ›› 2019, Vol. 74 ›› Issue (1): 162-177.doi: 10.11821/dlxb201901012

• 气候变化与地表过程 • 上一篇    下一篇

伊犁盆地北部山麓黄土粒度端元指示的粉尘堆积过程

李越1,2(),宋友桂1,宗秀兰1,2,张治平3,程良清1,2   

  1. 1. 中国科学院地球环境研究所 黄土与第四纪地质国家重点实验室,西安 710061
    2. 中国科学院大学,北京 100049
    3. 新疆伊犁哈萨克自治州环境监测站,伊宁 835000
  • 收稿日期:2017-11-17 出版日期:2019-01-18 发布日期:2019-01-18
  • 基金资助:
    国家重点研发计划全球变化专项(2016YFA0601902);国家自然科学基金项目(41572162);中国科学院国际合作局对外合作重点项目(132B61KYS20160002)

Dust accumulation processes of piedmont loess indicated by grain-size end members in northern Ili Basin

LI Yue1,2(),SONG Yougui1,ZONG Xiulan1,2,ZHANG Zhiping3,CHENG Liangqing1,2   

  1. 1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, CAS, Xi'an 710061, China
    2. University of Chinese Academy of Sciences, Beijing 100049, China
    3. Environmental Monitoring Station of Ili Kazakh Autonomous Prefecture, Yining 835000, Xinjiang, China
  • Received:2017-11-17 Online:2019-01-18 Published:2019-01-18
  • Supported by:
    National Key Research and Development Program of China, No.2016YFA0601902;National Natural Science Foundation of China, No.41572162;International Partnership Program of the Chinese Academy of Sciences, No.132B61KYS20160002

摘要:

中亚干旱区是全球重要的粉尘源区,是全球变化与区域响应研究的关键区域之一。中亚粉尘形成搬运沉积过程一直是全球变化研究的热点科学问题。本文选取位于伊犁盆地北部、北天山南麓不同地形和气候条件下的两处黄土剖面,对其沉积速率最高的层段进行了粒度测试分析,结合聚类分析和粒度分布曲线拟合两种方法,重建了黄土粉尘的堆积过程。伊犁盆地黄土主要由远源和近源物质组成,分别由高空西风和中尺度的区域风搬运而来。高空西风所携带的远源粘粒级矿物颗粒对盆地东部降雨较高地区有一定的贡献,而在盆地西部不容易沉降下来。中尺度区域风所搬运的近源物质组成了黄土沉积物的主体,而近源区沉积物的可用性在黄土的形成过程中扮演着重要角色。另外,非风暴过程中(沙尘暴过后)出现的浮尘在沙尘暴天气频率减少的时期对黄土的发育有重要贡献,而在沙尘暴天气频发的时期,较差的植被覆盖度能够使得已经沉降下来的浮尘组分重新被扬起至大气中。由此建立了一个粉尘堆积的概念模型。认识黄土粉尘的堆积过程对现代沙尘天气的治理和人类生存环境的改善具有重要作用。

关键词: 伊犁盆地, 黄土, 粒度端元分析, 粉尘堆积, 沙尘天气治理

Abstract:

Central Asia, consisting of extended arid and semiarid areas, is one of the major sources of global dust and aerosol in the Northern Hemisphere. Dust emission, transportation and deposition over the region have received an increasing interest. Loess deposits, as a geologic record of dust, enable the possibility of archiving dust variabilities over the past, and give insights into the underlying mechanisms of dust activities. Here, we examined the grain size data of two late Pleistocene loess-paleosol sequences, named Nilka (NLK) and Qingshuihe (QSH), in the Ili Basin, eastern Central Asia, with focus on intervals with the highest sedimentation rates in both loess sections. Both sites are located on the south slope of the northern Tianshan Mountains, but represent different topographies and climate conditions. Parametric curve-fitting and hierarchical cluster analysis techniques were applied to partition the whole spectrum of the measured grain size distributions and provided a more reliable and more representative statistical descriptors. The end members unmixed under distant eolian dynamics were used to reveal the dust accumulation processes in the Ili Basin in detail. The results suggest that the Ili loess mainly consists of distal and proximal sediments, with the high-level westerlies and the meso-scale regional winds as the transport agents respectively. Distal clayed mineral particles transported by the high-level westerlies can contribute to the loess sediments from the eastern basin due to the wet deposition, where precipitation is high. Nevertheless, this is not true for the western part of the basin where the clay fractions are difficult to deposit. Proximal sediments dominate the Ili loess, and the grain-size composition and formation process of the Ili loess can be dependent on the availability of the local particulate materials with different sizes. Additionally, the floating dust derived from "non-dust storm processes" (after sand and dust storms) has significant impacts on the loess formation during periods of decreasing dust storm frequency. Whereas sparse vegetation is likely to create favorable conditions to the resuspension of the floating dust components when dust storms occur frequently. A conceptual model about dust accumulation in the Ili Basin is proposed based on the above results.

Key words: Ili Basin, loess sediments, end-member modeling analysis of grain-size distributions, dust accumulation, control of sand-dust weather