| Nearly one year field observations (From February to December in 2010) in Qingnian Lake and Wetland Qilihai had been carried out. Total nitrogen (TN), exchangeable nitrogen (EN), fixed ammonium (F-NH4+-N), dissolved organic nitrogen (DON), total hydrolyzable amino acids (THAA-N) and hexosamine (HA-N) were detected. It also monitored environmental parameters such as redox potential, microbial activities and temperature. With laboratory simulation experiments, static release of nitrogen species and organic nitrogen degradation in surface sediment as well as the algae growth and their metabolites toxins oxidative degradation have been studied.The average concentrations of TN in Qingnian Lake and Wetland Qilihai revealed a high nitrogen pollution levels. DON, accounting for 97% of TN, was the main form of nitrogen in surface sediment. Meanwhile, THAA-N occupies the largest proportion (38%) of DON. EN accounts for a lower proportion of TN and NH4+-N is the major components (95%) of EN. According to the Fick's First Law, it revealed that NH4+-N is the main form of endogenous nitrogen releasing. In the experiment for the strength of nitrogen release in surface sediment, T, pH, DO and hydrodynamics are considered as environmental parameters. It showed that the rising temperature benefit the nitrogen release in sediments, but an excessively high temperature will inhibit the ammonium release. Meanwhile, increased dissolved oxygen content is not conducive to nitrogen release and a weak acid condition can promote the organic matter degradation in sediment. However, sediment in an alkaline environment is favorable to the NH4+-N solution toward the water from sediment. For hydrodynamic conditions, it proved that the process of short-term nitrogen release would be impacted by it but the long-term was not.According to amino acids degradation and principal component analysis (PCA), an index of DI'was introduced to reflect the freshness of sediments. The DI'index revealed that organic matter in sediment is complete degraded in summer and autumn while more fresh in winter and spring. Meanwhile, DI'has negatively correlations with environmental parameters such as T, Eh and microbial activities. It confirmed that a reducing environment may lead to a high level of organic matter degradation. Based on nitrogen mineralization experiments in surface sediments, anaerobic degradation rate is faster than that in aerobic conditions. THAA-N was the mainly form in DON decomposition while hexosamine was less biodegradable. Added N and C source can significant promote the process of DON degradation. However, it does not fit for the hexosamine biodegradation. The aeration was conducive to HA-N degradation and detrimental for DON degradation in sediments. According to the bioavailability of pramlintide acetate, it has a similar promotion with leucine in THAA-N biodegradation.In aeruginosa simulation experiments, an elevated nutrient of nitrogen can significant promotes the algae growth and the toxins releasing. However, excessively nutrients are not obvious for algae reproduction and inappropriate for TN removing. A rising temperature is conducive to the degradation of MCs which 20℃is optimal for algae absorption. Appropriate hydraulic conditions always fit for the algae prosperity and nitrogen elimination. Meanwhile, dissolved oxygen had no effect on algae growth. It confirmed that more oxygen and stronger hydro-disturbance can inhibit the production and release of MCs.The microcystin degradation is confirmed as a first order kinetic reaction. These processes can be greatly accelerated by UV/Fenton and Ultrasonic/Fenton system. Meanwhile, an appropriate initial concentration of the H2O2 and Fe2+ as well as MCs in reaction solution would cause a more efficient MCs degradation. These degradation processes also can be promoted by an excited UV or suitable pH (3~4) conditions. However, added anions such as CO32- and NO3- are not conducive to MCs oxidation.
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