Nitrogen Forms Characteristic In The Sediments From The Shallow Lakes And Functions In Biogeochemical Cycling

The content of different nitrogen fractions and their functions in recycling from the studied 14 sediments from the shallow lakes in the middle and lower reaches of Yangtze River area before and after nitrogen release experiment were investigated, and the content of different nitrogen fractions, the contributions of different nitrogen fractions to the nitrogen released from sediment also was studied. Influences of nitrogen and phosphor menace on physiological activities and ecological restoration of submerged aquatic plants were investigated. Major conclusions were described as follows:1. The content of total translate nitrogen, mineralizable nitrogen, exchangeable nitrogen and fixation ammonia on sediments are increased while the content of total nitrogen increased, but their ratio account for total nitrogen is depressed.2. The inter-correlations between NH4-N, NO3-N, NO2-N, FN and MN are positive and all significantly correlated with total nitrogen. There are important meaning of ecology and environment of their functions in biogeochemical cycling on sediments from the shallow lakes.3. The content of different translate nitrogen fractions is SOEF-N>IEF-N>SAEF-N> WAEF-N, and contribution of different translate nitrogen fractions to the nitrogen released from sediment is IEF-N>SOEF-N>SAEF-N>WAEF-N. In different grain size fraction from different sediments, the absolute content of total transferable nitrogen and different transferable nitrogen forms are the highest in fine grain size fraction and the lowest in coarse grain size fraction. The relative contribution of fine grain size fraction to nitrogen cycling is the absolute main fraction, which is several times to 10 times of that in coarse grain size fraction.4. The process of ammonium adsorption, fixation and release onto sediments of various lakes are accord with kinetic models, which measured of two parts including fast and slow reaction as a whole.The fast reaction mainly occurred within 0~5 and 0~10 minutes, But after 2, 2 and 12 hours, they reached equilibrium respectively.5. The nitrogen released from sediment was restrained by submerged aquatic plants absorption, but transference and translation of different nitrogen forms was strengthened, and specially mineralizable nitrogen released remarkably. 6. Endurance of submerged aquatic plants on nitrogen menace is far-under phosphor's, and harm of plants on ammonia was restrained under the function of phosphor.Submerged aquatic plants will be contabescence after 7~14 days if it was in high ammonia concentration solution.