藻华暴发中后期湖泊氮素、碳素循环研究

发布时间：2018-11-11 19:26

【摘要】：近几十年来,蓝藻水华已成为世界范围内一个重点关注的问题。目前,大量的研究工作都集中在营养盐对水华暴发的作用机理、藻华的潜在危害以及藻华的控制方法等方面,而关于藻华对营养盐的反作用机制的研究甚少。因此,本研究在太湖北岸进行蓝藻培养试验,考察藻华暴发体系对外源输入硝氮、氨氮的响应,结合分子生物学方法,对藻类所吸收氮素的最终去向进行探索。实验结果如下:1.添加外源硝氮体系中,含藻水样中的总氮浓度减少了 3.62mgL-1,其中总有机氮占40%,说明围隔中存在一种氮素转化并脱除的机制。硝氮等理化性质的变化表明藻附生菌和游离细菌的耦合矿化作用和硝化反硝化作用是有机氮脱除的主要方式,藻-菌系统减小了氮素在湖泊水体的循环路径。因此,蓝藻水华可以加速脱氮效率,这可能是夏季太湖中氮素浓度较低的原因。2.添加外源氨氮体系中,在藻类生长初期,藻类在与附生菌对铵的竞争中处于优势地位,但是到藻华中后期,附生菌逐渐占据优势。硝酸盐氮在夜间的浓度总是高于当天或次日早晨时的浓度,说明白天铵态氮转化为硝态氮,而夜间硝态氮又逐渐减少。当铵态氮被进一步消耗,围隔内部再矿化作用成为耦合硝化反硝化的氮源,导致前期被同化的氮素被有效去除。实验期间,含藻水样与空白水样中的硝酸盐氮浓度无显著差异(P0.01),这说明夏季在太湖许多蓝藻生物量相对较低的区域中也能发生附生耦合硝化反硝化作用,因此,矿化-硝化-反硝化过程可能是夏季太湖低浓度硝酸盐氮浓度条件下发生强烈反硝化反应的原因。3.未添加外源氮素体系中,含藻水样中溶解性有机碳浓度不断增加并于15日达到峰值72.0 mgL-1,高于太湖原位水背景值12.5倍,而水样荧光光谱所呈现的4个荧光峰中有3个荧光峰的强度均与叶绿素呈显著相关(P0.01),表明藻华暴发中后期蓝藻的生长代谢过程及死亡分解过程所释放的有色可溶性有机质是水体中溶解性有机质的一个重要来源。紫外光谱E3/E4在试验前中期均大于3.5,在试验末期有减小趋势,这说明藻华暴发初期和中期水体水质腐殖化程度较低。
[Abstract]:In recent decades, cyanobacteria Shui Hua has become a worldwide focus of attention. At present, a great deal of research work has focused on the mechanism of the effect of nutrient salts on Shui Hua outbreak, the potential harm of algal blooms and the control methods of algal blooms, but there is little research on the reaction mechanism of algal blooms to nutrient salts. Therefore, the experiment of cyanobacteria culture was carried out on the north shore of Taihu Lake. The response of algal blooming outbreak system to exogenous nitrate and ammonia nitrogen was investigated, and the final fate of nitrogen absorbed by algae was explored in combination with molecular biological methods. The experimental results are as follows: 1. The total nitrogen concentration in algal water decreased by 3.62 mg / L, and the total organic nitrogen accounted for 40%, which indicated that there was a mechanism of nitrogen transformation and removal in the enclosure. The changes of physicochemical properties such as nitrate and nitrogen showed that the coupling mineralization of epiphytic bacteria and free bacteria and nitrification and denitrification were the main ways to remove organic nitrogen. The algal-bacteria system reduced the circulation path of nitrogen in lake water. Therefore, cyanobacteria Shui Hua can accelerate nitrogen removal efficiency, which may be the reason for low nitrogen concentration in Taihu Lake in summer. 2. In the initial stage of algal growth, algae was dominant in the competition for ammonium with epiphytic bacteria, but at the middle and late stage of algal blooming, epiphytic bacteria gradually occupied the dominant position in the addition of exogenous ammonia-nitrogen system. The concentration of nitrate nitrogen in the night was always higher than that in the same day or the next morning, indicating that during the day the ammonium nitrogen was converted into nitrate nitrogen, but the nocturnal nitrate nitrogen gradually decreased. When ammonium nitrogen is consumed further, the internal mineralization of the enclosure becomes the nitrogen source of coupled nitrification and denitrification, which leads to the removal of nitrogen assimilated in the early stage. During the experiment, there was no significant difference in nitrate nitrogen concentration between the algae-containing water sample and the blank water sample (P0.01), which indicated that the epiphytic coupling nitrification and denitrification could also take place in many areas of Taihu Lake where the biomass of cyanobacteria was relatively low in summer. Mineralization-nitrification-denitrification process may be the reason of strong denitrification reaction at low nitrate concentration in Taihu Lake in summer. In the absence of exogenous nitrogen, the concentration of dissolved organic carbon in algae water increased continuously and reached a peak value of 72.0 mgL-1, on the 15th, which was 12. 5 times higher than the background value of in situ water of Taihu Lake. However, the intensity of three of the four fluorescence peaks in water samples was significantly correlated with chlorophyll (P0.01). The results showed that the dissolvable organic matter released from the growth and metabolism of cyanobacteria during the middle and late stage of algal blooming outbreak and the process of death decomposition was an important source of dissolved organic matter in water. UV spectrum E3/E4 was higher than 3.5 in the first and middle stages of the experiment, and decreased at the end of the experiment, which indicated that the water quality humification degree was lower in the early and middle period of algal blooms outbreak.
【学位授予单位】：扬州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X524

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