The Geochemical Characteristics Of Carbon And Silicon And The Environmental Information In The Daihai Lake

The geochemical behaviors of carbon and silicon in overlying water and sediments of the Daihai lake which is a deep algae-type lake in semi-arid region of China are studied. The distributions of inorganic carbon species are analyzed in detail. The processes on water-sediment interface are interpreted and the fluxes of carbon and silicon from sediment towards water are calculated. Furthermore, the influence of diatom on carbon cycle in the Daihai lake is discussed which is of great importance for the research of carbon cycle in algae-type lake. The conclusions reached in this paper are as follows:1. The water of the Daihai lake is characterized by high concentrations of both organic carbon and inorganic carbon. However, inorganic carbon is the main species. The average concentration of TIC is 119.15mg/L with DIC dominates, while average concentration of TOC is 28.78mg/L with DOC dominates.2. The analysis of inorganic carbon species implies that most parts of the inorganic carbon in sediments are easily extracted by acid, whereas, less of them can be extracted by alkali. Therefore, high alkalinity of the Daihai lake prevents the release of inorganic carbon from sediments.3. The characteristics of inorganic carbon species, contents of organic carbon in sediments and the carbon flux in water-sediment interface reveals that the Daihai lake functions as a carbon "sink".4. The silicon flux in water-sediment interface is calculated based on release experiments and the geochemical behavior of silicon in water-sediment system is analyzed to discuss the function of the Daihai lake in geochemical cycle of silicon. The concentration of SiO₃^2- in overlying water is 1.02mg/L, the contents of BSi in sediment is 7.47mg/g. The sediment of the Daihai lake functions as a silicon "source" in August.5. The ratio between carbon and silicon in suspended particulates implies that the Daihai lake is dominated with carbonate. The variation of ratio between carbon and silicon with core sediments implies the contribution of algae to the carbon cycle in lake system with growing eutrophication level.