Liu Zhi-Ying, Xu Hai, Zhan Xu, Zhu Guang-Wei, Qin Bo-Qiang, Zhang Yun-Lin
College of Environmental and Civil Engineering, Jiangnan University, Wuxi 214122, China.
Taihu Lake Ecosystem Research Station, State Key Laboratory of Lakes and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
Huan Jing Ke Xue. 2019 Mar 8;40(3):1261-1269. doi: 10.13227/j.hjkx.201808056.
Denitrification is the most important nitrogen removal process in lake waters, and is of great significance for mitigating nitrogen pollution and controlling eutrophication in lakes. The outbreak and decline of cyanobacterial blooms may promote denitrification directly in the water column by changing the nitrogen circulation pathway and microenvironment of the water body, and accelerate the removal of nitrogen. In order to verify this hypothesis, the cyanobacteria with different biomass and the NO-N, PO-P nutrient for 10 days were taken from Taihu Lake water to simulate the effects of cyanobacteria growth and degradation on denitrification. The dynamic changes of algal biomass and various forms of nitrogen concentration were simultaneously determined by N isotope addition culture combined with membrane inlet mass spectrometer (MIMS) for real-time quantitative determination of denitrification rate. The results showed that cyanobacteria absorbed nitrogen into particle nitrogen during the growth period. During the decay period, algae cells released a large amount of NH-N by degrading mineralization, which was then converted into NO-N to provide a substrate for denitrification. That is the key to promoting denitrification in water; the denitrification rate (as N) reaches (1614.52±301.57)μmol·(m·h), which is three times higher than the denitrification rate[ (534.45±242.18)μmol·(m·h)]of the lowest concentration cyanobacterial group at the same time. At the end of the experiment, the highest rate of TN removal was highest in the group with the highest initial biomass of cyanobacteria (40.02%), which was 2.26 times of the TN removal rate (17.72%) in the control, indicating that cyanobacterial accumulation can significantly promote the intensity of denitrification and accelerate the removal of nitrogen in water. The rate of denitrification in the decline of cyanobacteria is significantly affected by the concentration of NH-N, indicating that the coupling of nitrification-denitrification of microorganisms attached to algae is the main route of nitrogen removal. The results study indicate that the cyanobacteria bloom rapidly during the growth period. Nitrogen is converted into particle nitrogen. The degradation of cyanobacteria is accelerated by coupled nitrification-denitrification, which may be one of the reasons for the decrease of nitrogen concentration in Taihu Lake.
反硝化作用是湖泊水体中最重要的脱氮过程，对于减轻湖泊氮污染和控制富营养化具有重要意义。蓝藻水华的爆发和衰退可能通过改变水体的氮循环途径和微环境，直接促进水柱中的反硝化作用，并加速氮的去除。为了验证这一假设，从太湖水体中采集了不同生物量的蓝藻以及NO-N、PO-P营养物质，进行为期10天的实验，以模拟蓝藻生长和降解对反硝化作用的影响。通过N同位素添加培养结合膜进样质谱仪（MIMS）实时定量测定反硝化速率，同时测定藻类生物量和各种形态氮浓度的动态变化。结果表明，蓝藻在生长期间将氮吸收到颗粒氮中。在衰退期，藻细胞通过降解矿化释放出大量的NH-N，然后转化为NO-N，为反硝化作用提供底物。这是促进水体中反硝化作用的关键；反硝化速率（以N计）达到(1614.52±301.57)μmol·(m·h)，是同期最低浓度蓝藻组反硝化速率[(534.45±242.18)μmol·(m·h)]的三倍。实验结束时，初始生物量最高的蓝藻组的总氮去除率最高（40.02%），是对照组总氮去除率（17.72%）的2.26倍，表明蓝藻积累可显著促进反硝化作用强度，加速水体中氮的去除。蓝藻衰退期的反硝化速率受NH-N浓度的显著影响，表明附着在藻类上的微生物的硝化-反硝化耦合是主要的脱氮途径。研究结果表明，蓝藻在生长期间迅速繁殖，氮转化为颗粒氮。通过硝化-反硝化耦合加速蓝藻降解，这可能是太湖氮浓度降低的原因之一。
