Grain-size characteristics of lacustrine sediments in Balkhash Lake, Kazakhstan and its response to regional environmental changes [哈萨克斯坦巴尔喀什湖沉积物粒度特征及其对区域环境变化的响应]

作者：He Z.; Ma L.; Jilili A.; Liu W.; Gulnura I.; Galymzhan S.; Huang K.

来源：Arid Land Geography, 2021, 44(5): 1317-1327.

DOI：10.12118/j.issn.1000-6060.2021.05.13

• Balkhash Lake
• Environmental change
• Grain size
• Kazakhstan
• Lacustrine sediments

Lake sediment grain-size data give a wealth of information regarding watershed environmental change and can provide a reliable method to reconstruct paleoenvironmental changes in areas without instrumental data. Through the analysis of environmental proxies, such as grain size and the magnetic susceptibility of the core sediments of Lake Balkhash, combined with radioactive 137Cs dating and instrumental data including the regional climate and lake water level, characteristics regarding the grain size of the sediments of Lake Balkhash in Kazakhstan and their environmental meanings were established. The results show that the average contents of the clay components (<4 μm), fine silt (4-16 μm), medium silt (16-32 μm), coarse silt (32-64 μm), and sand (>64 μm) in the lake sediment were 20.32%, 40.13%, 22.86%, 10.55%, and 6.13%, respectively. The proportions of the environmentally sensitive components F1 (6.61-10.00 μm) and F2 (45.71-69.18 μm) in the sediment were extracted via the method of standard deviation versus grain size. The present study shows that, due to the increasing influence of human activities, changes in the content of the sensitive components of grain size cannot accurately reflect changes in lake water level, lake runoff, and even regional climate. Changes in sediment composition are instead related to changes in the intensity of human activities as reflected by the magnetic susceptibility of sediments, which shows significant correlation with human activity (r=0.870, P<0.01). It is observed that the increase in the magnetic susceptibility of the lake sediments is due to the increase in human activities in the watershed, which causes the transport of fine-grained detrital materials rich in magnetic materials into the lake. These research findings can provide an important reference for studies regarding paleoenvironment reconstruction on a long-term scale and have a clear scientific significance for understanding of the impact of human activities in the basin on lake environments.

• 单位
  中国科学院大学; 荒漠与绿洲生态国家重点实验室