Abstract

湖泊等内陆水体是大气N<sub>2</sub>O潜在的重要排放源,也是全球N<sub>2</sub>O收支估算的重要组成部分。目前全球湖泊普遍面临富营养化和蓝藻暴发等问题,明晰藻型湖泊N<sub>2</sub>O排放强度及其环境影响因子对准确估算湖泊N<sub>2</sub>O排放和预测其未来变化至关重要。本研究选择太湖藻型湖区为研究对象,同时选取人为活动影响较小的湖心区作为对比区域,基于2011年8月至2013年8月为期2年的逐月连续观测,探讨藻型湖区N<sub>2</sub>O排放特征及其影响因素。结果表明,藻型湖区呈现极强的N<sub>2</sub>O排放,其排放通量为(4.88±3.05) mmol/(m<sup>2</sup>·d),是参考区域(湖心: (2.10±4.31) mmol/(m<sup>2</sup>·d))的2倍多。此外,在藻型湖区中不同点位N<sub>2</sub>O排放差异显著,受河流外源输入影响,近岸区是N<sub>2</sub>O的热点排放区,其年均排放通量高达10.93 mmol/(m<sup>2</sup>·d)。连续观测表明N<sub>2</sub>O排放具有显著的季节变化模式,但在不同区域调控N<sub>2</sub>O排放时间变化的因子有所不同。其中,近岸区N<sub>2</sub>O排放主要受氮负荷影响,其他区域N<sub>2</sub>O排放变化受水温和氮负荷等多因子影响。氮素富集是藻型湖区N<sub>2</sub>O高排放的直接原因,水体氮负荷可以作为N<sub>2</sub>O排放热点的重要指示因子。但藻型湖泊N<sub>2</sub>O排放极其显著的时空变异等在未来研究中应得到更多关注。;Inland lakes potential emit large nitrous oxide (N<sub>2</sub>O) to atmosphere and play significant role in global N<sub>2</sub>O budget estimation. Widespread global increase in lake phytoplankton blooms have been found, identifying the N<sub>2</sub>O flux and its influencing factors at the cyanobacteria-dominated lake is essential to being able to accurate estimate the N<sub>2</sub>O emissions from lakes and predict future change. In order to identify N<sub>2</sub>O flux characteristics and its influencing factors in the cyanobacteria-dominated zone of Lake Taihu, the N<sub>2</sub>O emission was observed based on the two-year field measurements. Results showed the annual mean N<sub>2</sub>O flux from the cyanobacteria-dominated zone ((4.88±3.05) mmol/(m<sup>2</sup>·d)) was about twice higher than that in the central zone with less cyanobacteria blooms ((2.10±4.31) mmol/(m<sup>2</sup>·d)). Meanwhile, the N<sub>2</sub>O emissions varies spatially within the cyanobacteria-dominated zone, peak N<sub>2</sub>O emission (10.93 mmol/(m<sup>2</sup>·d)) occurred in littoral zone due to the large external loadings input via river discharge. Continuous filed measurement showed that the N<sub>2</sub>O emission varied seasonally, but the factors influencing the seasonal patterns varied among sub-zones. Generally, the temporal variation of N<sub>2</sub>O emission were regulated by N loadings in littoral zone, and were regulated by multiple environment variables, such as temperature and N loadings, in Meiliang Bay and the central zone. High nitrogen loadings contributed to large N<sub>2</sub>O emission from cyanobacteria-dominated zone, indicating that N loadings can be used as proxy of N<sub>2</sub>O emission from lakes. Considering significant temporal and spatial variation of N<sub>2</sub>O emission from cyanobacteria-dominated zones, more attention should be paid in future research.

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