The Geochemical Characterystics Of Silicon In Hulun Lake Sediments And The Contrastive Study On Silicon Fractions In Four Typical Lakes,Inner Mongolia Plateau

Along with the academic research of carbon cycles more lucubrate, the study on silicon cycles becomes increasingly important and has caused widespread concern in the world. Silicon (Si), as an important biogenic element, acts an irreplaceable role on the primary production of larger phytoplankton such as diatoms. Silicon phytoplankton, the main component of primary production in water, is the most dominated source of biogenic silica. Sediments are enormous silicon storage sinks in lacustrine environment, and may play a vital role in the cycle of lake silicon. Silicon in sediments is the most important indicator of the primary production in water ecosystems.The Lake Hulun, located in the eastern of Inner Mongolia Plateau, is one of the highest latitude lake wetlands in China. Although the studied lake is situated in the semi-arid continental climate zone, it still is the Eastern Asia’s largest natural freshwater lake. On the geographic location and the natural environment, the Lake Hulun lies in place of the intersection between rushing torrents zone of west wind and East Asian Monsoon area, consequently, the study on mechanism of eutrophication in the Lake Hulun has special meaning.Based on the studies of silicon forms and biogenic silica and combined the former study results of our groups, systematically carry out the experiments about the geochemical characteristics in the western Inner Mongolia Plateau’s lake. The experiments results revealed the factors that may influence the distribution of silicon in lake sediments, and investigated the correlation between biogenic silica and organic matters in sediments. We also compared the distribution characteristics of biogenic silica in the four typical lakes from Inner Mongolia Plateau, and the real purpose of the study is to accumulate basic data in the biogeochemistry study of lacustrine biogenic elements. The conclusions are as follows:1. The study on the geochemical characteristics of silicon in Hulun lake sediments was firstly carried out, and accumulated a lot of important basic data about the important biogeochemistry process of silicon in high latitude lake.2. The interdependent relationships between biogenic silica and organic matter in Hulun Lake sediment cores were also investigated, and the results illustrated that high level of organic matter could restrain the dissolution of biogenic silica, meanwhile promote the accumulation of biogenic silica in sediments and limit the recycling ability of biogenic silica.3. A sequential chemical extraction procedure proposed by Tessier et al was employed. The research of silicon fractions in the main lakes sediments from Inner Mongolia Plateau was also first carried out, and concluded that IMOF-Si and OSF-Si were the main forms of exacted silica in four lakes.4. Rock weathering and erosion have a significant impact on the spatial distribution of biogenic silica in Hulun Lake surface sediments, and the distribution characteristics of BSi were significantly correlated with particle size distribution of sediments. The geochemistry information of biogenic silica at10cm layer of Hulun Lake sediment cores have a good response relationship with the highest water level and the El Nino at1968in Hulun Lake.5. The mechanism on the different geochemistry characteristics of silicon in Inner Mongolia Plateau lake sediment was firstly explained. The results showed that some important factors including the natural geography condition, the degree of rock weathering and erosion, the type of lacustrine ecosystems and biomass, re-suspension and human disturbance all affected the geochemical characteristics of silicon in lake sediments.