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中国沙漠 ›› 1999, Vol. 19 ›› Issue (4): 399-402.

• 论文 • 上一篇    下一篇

黄土孢粉分析的新途径——筛滤分析法

李小强1, 周杰1, A. R. Ashraf2, EvaWacker2   

  1. 1. 中国科学院黄土与第四纪地质国家重点实验室, 陕西西安 710054;
    2. Institute & Museum of Geology & Paleontology, Tuebingen University, Germany
  • 收稿日期:1999-03-31 修回日期:1999-05-19 出版日期:1999-12-20 发布日期:1999-12-20
  • 作者简介:李小强(1965-),男(汉族),四川成都人,理学博士,助理研究员,从事第四纪地质及第四纪花粉研究。
  • 基金资助:
    中国科学院资源环境重大项目(KZ951-A1-402);科技部攀登项目(95-预-40)

A New Way of Spore pollen Analysis in Loess Deposits: Sieving-analysis Method

LI Xiao qiang1, ZHOU Jie1, A. R. Ashraf2, Eva Wacker2   

  1. 1. The State Key Lab of Loess and Quaternary Geology, Chinese Academy of Sciences, Xi'an 710054, China;
    2. Institute & Museum of Geology & Paleontology, Tuebingen University, Germany
  • Received:1999-03-31 Revised:1999-05-19 Online:1999-12-20 Published:1999-12-20

摘要: 黄土-古土壤序列在全球古气候、古环境研究中占有不可替代的重要地位,而其中的孢粉是黄土高原生态环境演化过程中保存的直接生物学证据,它对建立黄土高原降水或湿度状况的时空变化特征,认识季风变迁的过程、规律以及未来发展趋势等具有重要的意义。随着黄土研究工作的不断深入,作为直接生物学证据的孢粉研究相对薄弱。其中最困扰的因素是从黄土中提取孢粉极其困难,分析技术上始终未能找到一个突破口,因此需要一种分析效果好、快捷、成本低的分析方法以获得大量高精度的孢粉数据。筛滤分析法正是为了适应黄土研究的需要而设计的一种新型的黄土孢粉分析方法。筛滤分析法利用真空状态下的气压差使样品在水中完全悬浮跳动,样品得到充分的冲洗并促使孢粉与其它无机质与有机质分离。相对真空的状态减少了微细颗粒对极为细小的网眼的阻塞,重力作用促使水及各类颗粒不断冲击筛网,使粒径小于10μm的物质较容易被过滤到聚水容器中,而孢粉与较少的大颗粒物质则被隔离在筛网之上,这使我们很容易用重液浮选出干净、清晰的孢粉底样。筛滤分析法与常规的黄土孢粉分析相比,具有以下特点:①大大降低了分析样品的重量及药品的消耗,一般仅需样品30 g左右,是常规分析法用量的1/6~1/8。②整个分析流程短, 12个样品一个流程仅需3~4 d。③筛滤分析法使孢粉几乎全部被隔离在筛网上而丢失极少,提高了黄土孢粉研究精度。④筛滤分析法几乎不破坏孢粉的结构,孢粉底样干净、清晰。使用筛滤分析法共分析耀县全新世黄土剖面69块孢粉样品,均发现数量不等的孢粉。孢粉底样干净、杂质少,结构清楚。共统计孢粉14978粒,分属27个科属,这些科属包括了黄土高原主要的孢粉类型。从孢粉结果可以初步确定,在全新世时期,位于黄土高原南缘的耀县地区,草本植物占全部孢粉总量的93.6%,而乔木植物仅占孢粉总量的4.7%。在整个剖面中没有出现乔木植物含量超过30%,可以认为在黄土高原的全新世时期是以草原植被为主,并无森林生长。

关键词: 黄土, 孢粉分析, 筛滤分析法

Abstract: Loess paleosol sequence occupies an important position in the studies of the global paleoclimate and paleoenvironments. The spore pollen in loess paleosol is regarded as the direct biological evidence for the ecological and environmental changes of loess plateau, which plays an important role for reconstructing the spatial and temporal charcteristic of precipitation on the loess plateau, and for understanding the process, regulation, and developmental trend of monsoon change in the future. With the development of loess study, it is necessary to find an analysis method of high effect, short process, and lower cost in order to get a great deal of high precision pollen data. The sieving analysis method, a new way of pollen analysis, is designed to fit the study needs of loess pollen. Sieving analysis method makes use of the difference of barometric pressure of vacuum to make the sample suspend and jump in water wholly. The sample is washed fully and the pollen is departed from the organic and inorganic materials. The relative condition of vacuum decreases the block of the tiny material against the very fine sieve. The gravitational force makes the water and various pellets lash at the sieve continuously. The material less than 10 μ is easy to be filtrated out into container. The pollen and a little amount of bigger fine material is isolated on the sieve. It is easy for us to float out the clean and clear pollen sample using heavy liquid. Compared with the conventional method, the advantages of sieving analysis method are as fellows: ① Less weight of sample and the drain of chemical reagents consumption, generally, about 30g sample which is only 1 sixth to 1 eighth of conventional method's need. ② Shorter process, a process of 12 samples needs about 3 days. ③ The sieving analysis makes nearly all pollen on the sieve and loses few pollen, which increases the study precision. ④ The new method nearly doesn't destroy the pollen structure; the pollen is clean and clear. We have analyzed 69 pieces of pollen samples using sieving analysis method from Yaoxian section of Holocene and found different amount pollens in all samples. Pollen sample has little impurity. Author has counted all of 14978 pollen grains which belong to 27 families and genus. All of these families and genus include the main pollen types in loess plateau. We can initially decide from the results of pollen analysis that the grass plants make up about 93.6% and the tree plants only make up 4.7% of the total pollen amount. The pollen peak of tree plants doesn't arise over 30% in whole section. We seem to think that the grass plants dominated the whole loess plateau and there were not forest in Holocene.

Key words: loess, spore pollen analysis, sieving analysis method

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