向海尖底泡沼泽沉积物磁化率特征及其环境意义

Characteristics and Environmental Significance of Magnetic Susceptibility of Sediment in Jiandi Wetland in Xianghai

以吉林省向海自然保护区尖底泡沼泽湿地为研究对象,通过210Pb,137Cs建立高分辨率年代序列,并结合沉积物粒度指标,分析沉积物粒度与磁化率变化的相关性,对向海近几百年的环境变化进行探讨。结果表明:历史时期内陆沼泽沉积物频率磁化率反映的向海气候变化可划分3个阶段,并与粒度的分析结果基本一致。沼泽沉积物磁化率可以作为恢复历史时期环境变化的指标之一。

Currently, the research on the magnetic susceptibility of swamp sediment is relatively feeble. The study area, Jiandi Wetland （45°00. 078＇N, 122°20. 148＇E, 175 m a. s. 1. ）, is located in a farming-pasturing ecotone, a semiarid region in west jilin Province, China, where the annual temperature, precipitation and evaporation are 5.1℃, 408.2 mm and 1945 mm respectively, and the response of natural environment to climate change is sensitive. In this paper, the content of different grain sizes from 0.2 μm to 2 000 μm and the magnetic susceptibility are measured to study the correlation between the granularity and magnetic susceptibility of sediment, and a case study on the characteristics and environmental significance of magnetic susceptibility in Jiandi Wetland is carried out. The correlation between the granularity and the magnetic susceptibility of sediment in Jiandi Wetland is analyzed based on measuring the radionuclide dating and the magnetic susceptibility of sediment, and the environment change in Jiandi Wetland since recent several hundred years is researched. The results show that the climate change revealed by the magnetic susceptibility of swamp sediment can be divided into three stages, which accord basically with the analyzed results of granularity of sediment; there is a negative correlation between the magnetic susceptibility and the granularity of sediment; the value of magnetic susceptibility of sediment was high when precipitation was increased; the magnetic susceptibility of swamp sediment can be regarded as one of the main indexes in revealing the environment change in historical periods.