内蒙古布日敦湖湖泊沉积物粒度的风沙活动指示意义

Grain-size distribution in the lake deposits from the Buridun Lake in Inner Mongolia as an indicator of aeolian activity

关键词:  布日敦湖  粒度组成  风沙活动  人类活动  土地沙化

Key words:  Buridun Lake  grain-size composition  aeolian activity  human activity  land desertification

摘要:

本文通过研究位于东亚季风过渡带的布日敦湖湖泊沉积物粒度组成和碳、氧同位素特征,结合²¹⁰Pb/¹³⁷Cs年代数据,建立布日敦湖近50年的粒度变化序列。通过与中国北方100个气象站数据的年平均沙尘暴日数进行对比,建立研究区可靠的风沙活动指标。研究发现,布日敦湖湖泊沉积物粒度特征对研究区风沙活动具有指示意义。其中,细颗粒(4~16μm)含量变化与翁牛特旗沙尘暴日数变化趋势较吻合,可以指示区域风沙活动;而粗颗粒组分(>64μm)含量变化趋势与沙尘暴日数变化差异较大,推测可能受到大规模人类活动导致的湖区附近土地沙化影响,所以不能指示风沙活动。研究区生态环境脆弱,大规模人类活动会导致生态环境恶化和土地沙化,为现代北方沙尘活动提供沙源,并为未来的沙尘活动恶化埋下隐患,因而研究区不适宜进行大规模人类活动。本文的研究成果对保护研究区生态环境和区域防风固沙具有重要意义。

Abstract:

The present paper is concerned with some aspects of the lake deposits in the Buridun Lake in Inner Mongolia. The aims are, firstly, to construct the grain-size sequences for the Buridun Lake during the last 50 years on the basis of grain-size composition, carbon and oxygen isotopes and ²¹⁰Pb/¹³⁷Cs age determinations, and secondly, to clarify the trend of the aeolian activities on the basis of the comparison of annual average sandstorm days (data from 100 meteorological observatories) in the study area and northern China. The coincidence of the variable trends of the fine grains (4 to 16μm) contents in the Buridun Lake deposits and sandstorm days in the Ongniud Banner may indicate the states of regional aeolian activities. The greater differences of variable trends of the coarse grains (> 64μm) contents in the Buridun Lake deposits and sandstorm days in the Ongniud Banner indicate that the lake area may be affected by the land desertification caused by lagre-scale human activities rather than the aeolian activities. Therefore, it is inadvisable to develop the lagre-scale human activities in the Ongniud Banner region. This will be very important to the protection of ecological environments and regional wind protection and sand fixation.