State Key Laboratory of Lake and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; School of Environmental and Civil Engineering, Jiangnan University, Wuxi 214122, China.
School of Environmental and Civil Engineering, Jiangnan University, Wuxi 214122, China.
J Environ Sci (China). 2022 Jan;111:229-239. doi: 10.1016/j.jes.2021.02.033. Epub 2021 Apr 10.
Eutrophication and harmful cyanobacterial blooms threaten water resources all over the world. There is a great controversy about controlling only phosphorus or controlling both nitrogen and phosphorus in the management of lake eutrophication. The primary argument against the dual nutrients control of eutrophication is that nitrogen fixation can compensate the nitrogen deficits. Thus, it is of great necessary to study the factors that can significantly affect the nitrogen fixation. Due to the difference of climate and human influence, the water quality of different lakes (such as water temperature, N:P ratio and water residence time) is also quite different. Numerous studies have reported that the low N:P ratio can intensify the nitrogen fixation capacities. However, the effects of temperature and water residence time on the nitrogen fixation remain unclear. Thus, 30 shallows freshwater lakes in the eastern plain of China were selected to measure dissolved N and Ar concentrations through N: Ar method using a membrane inlet mass spectrometer to quantify the nitrogen fixation capacities and investigate whether the temperature and water residence time have a great impact on nitrogen fixation. The results have shown that the short lake water residence time can severely inhibit the nitrogen fixation capacities through inhibiting the growth of nitrogen-fixing cyanobacteria, changing the N:P ratio and resuspending the solids from sediments. Similarly, lakes with low water temperature also have a low nitrogen fixation capacity, suggesting that controlling nitrogen in such lakes is feasible if the growth of cyanobacteria is limited by nitrogen.
富营养化和有害蓝藻水华威胁着全世界的水资源。在湖泊富营养化管理中，只控制磷还是同时控制氮和磷存在很大争议。反对富营养化双重营养物控制的主要论点是，固氮可以弥补氮的不足。因此，研究能显著影响固氮的因素是非常必要的。由于气候和人为影响的差异，不同湖泊的水质（如水温、N:P 比和水停留时间）也有很大差异。许多研究报告称，低 N:P 比可以增强固氮能力。然而，温度和水停留时间对固氮的影响仍不清楚。因此，选择了中国东部平原的 30 个浅水淡水湖泊，通过使用膜进样质谱仪通过 N:Ar 方法测量溶解 N 和 Ar 浓度，以量化固氮能力，并研究温度和水停留时间是否对固氮有重大影响。结果表明，短的湖水停留时间通过抑制固氮蓝藻的生长、改变 N:P 比和从沉积物中再悬浮固体来严重抑制固氮能力。同样，水温低的湖泊固氮能力也较低，这表明如果氮限制了蓝藻的生长，那么控制此类湖泊中的氮是可行的。
