呼伦湖沉积物粒度特征及其环境指示意义

通过对呼伦湖湖心沉积岩芯粒度机械组成和频率分布曲线的分析,辅以²¹⁰Pb年代测定,重建了1865~2016年粒度演变特征并揭示其环境指示意义。研究表明：湖心沉积物主要为粉砂和黏土,中值粒径同粗粉砂和砂组分显著正相关,在垂直剖面上表现为减小、波动变化和增大的变化趋势。应用对数正态分布函数对粒度频率曲线进行拟合,提取出大气粉尘源、湖心相标志组分和风沙尘暴组分3个环境敏感组分。粒度机械组成与环境敏感组分的垂向特征变化同历史时期的湖泊水位变化、降水量强度变化,及沙尘暴事件较为一致,能够较好的重建150 a来湖区气候干湿变化和风沙活动特征,可用于恢复区域环境变化历史。

Grain-size Characteristics and Their Environmental Significance of Hulun Lake Sediments

Grain-size evolution characteristics and their environmental significance of Hulun Lake sediments were investigated since 1865 to 2016. The sediment core with a length of 78 cm was collected in the center of the lake in August 2016. Mechanical compositions of grain-size and frequency distribution curves were measured by the grain-size analyzer “Mastersizer 2000”. Based on accurate dating by ²¹⁰Pb, the regional environment and climate changes of the Hulun Lake according to the vertical profile of sediment grain sizes, which provides a new effective way for recovering the century-scale climatic changes. The results indicate that: sediments were mainly composed of silt and clay, and significant positive correlation were found between the contents of median grain-size and coarse silt and sand. Contents of median grain-size showed the changes of decrease, fluctuation and increase from the bottom to top of the sediment core. Three environmental sensitive components of atmospheric dust, eulimnetic facies, dust storm were identified by the method of log-normal distribution. Good agreements were found among the changes of grain-size, sensitive components, lake water levels, precipitations, and dust events. The results indicated that the current study well reconstructed the history of dry and wet climatic changes and wind-sand activities characteristics.