Release Characteristics Of Silicon, Iron And Carbon In The Sediments From Lake Wuliangsuhai

As an efficient biogeochemical reactor, lake is a combining site of atmosphere, hydrosphere, lithosphere and biosphere. Sediment plays an important role in lake nutrient accumulation, and is vulnerable to environment conditions change. As a result, the source/sink function of sediment will convert. Silicon and iron are the factors restricting primary productivity of lake. In addition, both silicon cycle and iron cycle are closely related to carbon cycle. This paper was carried out on the Wuliangsuhai Lake (WLSH) based on the exchange fluxes of water-sediment interface simulation experiment. Futhermore, the interface process of Si, Fe and C was analysised, and different environmental factors (pH, microorganism and low molecular weight organic acids) on the sediment of Si and Fe releasing mechanism also deeply discussed, the coupling relationships of DIC and DOC was revealed. Accordingly, the results are described as follows:1. The results showed that within the pH range of WLSH real environment, with pH increased(7.0-9.5), the concentration of Si, Fez+ and Fe3+ in overlying water increases, while the content of BSi, Fe2+ and Fe3+ in sediments decreases, indicating that silicon and iron diffusion direction vector pointing sediments in the water-sediment interface of WLSH weakly-alkaline environment, which reveals the trend of silicon and iron deposite in sediments.2. Silicon and iron concentration was higher in microorganism system than in non-microorganism system both in overlying water and sediments. At the same time, the microbial experiment confirmed the presence of dissimilatory Fe(Ⅲ)-reducting bacteria.3. The study found that oxalic acid and citric acid system is stronger than single citric acid system in silicate minerals dissolution. The main mechanism of iron release in sediments from Acorus calamus area may be acid dissolution in frozen period, while complex dissolution in non-frozen period. Moreover, the main mechanism of iron release in sediments from Phragmites area may be complex dissolution in both frozen period and non-frozen period.4. The estimated results of Wuliangsuhai release experiments indicate submerged plant area sediments act as silicon sink and iron sink, with overlying water deposite about 15.62t Si, 1.00t Fe2+ and 0.88t Fe3+ to sediments the whole year; emergented plant area sediments act as silicon source and iron source for overlying water, sediments release about 15.62t Si,1.OOt Fe2+ and 0.88t Fe3+ to overlying water the whole year.5. The coupling relationships of DIC and DOC mainly influenced by microbial uptake, non-biodegradable, coprecipitation of DOC and CaCO3, lake type and water quality chemistry of lake.6. The sink or source functions of sediments could be considered as the results of synthetic action of lake types, offshore distance, geohydrochemistry and inorganic carbon forms distribution.