【作者】 李鑫；

【导师】 赵林；

【作者基本信息】 天津大学 ， 环境科学， 2012， 博士

【摘要】 通过对天津市青年湖、七里海为期一年(2010年2月~12月)的野外观测,监测其表层沉积物中总氮、可交换态氮、固定态铵、溶解态有机氮以及可水解态氨基酸、氨基糖态氮等各形态氮的含量以及氧化还原电位、微生物活性、温度等环境参数,并结合实验室模拟实验,研究了若干生境因子对表层沉积物氮营养盐的静态释放、有机氮的降解以及藻类生长和代谢产毒的影响,同时探讨了藻毒素的降解机理。青年湖和七里海表层沉积物中总氮赋存含量偏高,溶解态有机氮是沉积物中氮的主要形态;氨基酸态氮是有机氮的主要形态;铵态氮是采样点沉积物内源释放的主要形式。温度升高有利于沉积物中氮的释放,但是过高的温度又会抑制铵态氮的释放;溶解氧升高不利于沉积物中氮的释放;弱酸性环境有利于沉积物中有机质的降解,碱性环境有利沉积物中铵态氮从水体溶出;水动力条件对氮营养盐短期释放强度有重要影响,而对长期释放强度影响不显著。根据氨基酸的选择性降解和主成份分析法引入降解指数DI’,三个采样点均呈现夏、秋季节DI’指数较低而春、冬季节较高的季节变化特征。DI’指数与环境参数温度、沉积物含氧状况和微生物活性负相关。沉积物中有机氮的厌氧降解速率大于好氧降解速率,氨基酸态氮是沉积物中有机氮降解的主要形态,氨基糖不易降解。氮源、碳源的加入能显著提高有机氮的降解速率而对氨基糖的降解速率无明显影响;曝气有利于沉积物中氨基糖的降解而不利于有机氮的降解;加入醋酸普兰林肽和亮氨酸后对氨基酸态氮的降解速率有一定的促进作用。铜绿微囊藻培养实验表明营养盐浓度的升高有利于藻类的生长及代谢产藻毒素,但过高的营养盐浓度对藻类生长的促进作用不明显且不利于沉积物中总氮的去除;温度升高有利有藻类代谢产毒;溶解氧含量对藻类的生长无明显影响,而适宜的水体扰动条件有利于藻类的生长。藻毒素类物质降解反应模型为一级动力学模型,紫外光助降解/Fenton联用体系、超声降解/Fenton联用体系均能加速藻毒素的降解。在芬顿体系中,适中含量的初始H2O2浓度、初始MCs浓度和初始Fe2+浓度能够快速降解藻毒素;芬顿体系在pH值为3~4的范围内能获得较高的降解速率,而体系中加入CO32-、NO3-等阴离子会降低反应速率,同时UV照辐光强的提升亦可提高其降解效率。更多还原

【Abstract】 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.更多还原