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生态学杂志 ›› 2020, Vol. 39 ›› Issue (8): 2737-2747.

• 研究报告 • 上一篇    下一篇

峡谷型水库温度分层期关键界面N2O的产生和释放机理

高蝶1,2,陈赛男3,李思亮3,刘小龙1,2*,李军1,2,白莉1,2,杨静2,王中良1,2   

  1. 1天津师范大学天津市水资源与水环境重点实验室, 天津 300387;2天津师范大学地理与环境科学学院, 天津 300387;3天津大学表层地球系统科学研究院, 天津 300072)
  • 出版日期:2020-08-10 发布日期:2021-02-10

Nitrous oxide production and emission mechanisms in key interfaces of canyon-reservoirs during stratification period.

GAO Die1,2, CHEN Sai-nan3, LI Si-liang3, LIU Xiao-long1,2*, LI Jun1,2, BAI Li1,2, YANG Jing2, WANG Zhong-liang1,2   

  1. (1Tianjin Key Laboratory of Water Resources and Environment, Tianjin Normal University, Tianjin 300387, China; 2School of Geography and Environmental Science, Tianjin Normal University, Tianjin 300387, China; 3Institute of Surface-Earth System Science, Tianjin University, Tianjin 300072, China).
  • Online:2020-08-10 Published:2021-02-10

摘要: 温度分层期峡谷型水库不同界面上氮的动态转化过程对准确评价水体N2O产生机理和释放通量具有重要的影响。通过采集乌江中上游梯级开发的洪家渡水库、东风水库和乌江渡水库的温度分层期水体样品,分析了氮形态和N2O的含量。结果发现,洪家渡水库、东风水库和乌江渡水库剖面水体N2O含量分别为14.3~64.4、16.5~35.7与17.0~70.8 nmol·L-1,均表现为大气N2O的释放源。东风水库全剖面和乌江渡水库均温层以上(0~58 m)的ΔN2O与表观氧利用(AOU)之间具有显著相关关系,说明其N2O的产生主要受控于硝化作用。乌江渡水库和洪家渡水库均温层的DO、NO3--N和N2O剖面变化规律表明,乌江渡水库均温层主要为利用原位NO3-进行的反硝化作用,而洪家渡水库均温层反硝化作用则主要利用上层水体传输的NO3-。洪家渡、东风和乌江渡水库的水-气界面N2O释放通量分别为0.4、0.5与0.4 μmol·m-2·h-1,均显著高于10年前同期的释放水平,说明随着水库库龄增大和水库自身蓄水调节方式的改变,水库N2O释放潜能有逐渐增大的趋势。洪家渡、东风和乌江渡水库在7月份以下泄水方式释放的N2O量分别为0.19×104、1.6×104与6.7×104 mol,在梯级开发的河流-水库体系中,下泄水体排放的N2O量受水库间的联合调度和蓄水调节方式的影响。

关键词: 梯级水库, 温室气体, 氮循环, 均温层, 氧化亚氮

Abstract: Nitrogen (N) dynamics at different interfaces in canyon reservoirs during the thermal stratification period substantially influence the authentic quantification of N2O emission in the cascade reservoir system. We examined various N species (NO3--N, NH4+-N), dissolved N2O concentration, and dissolved oxygen (DO) in water samples collected from three reservoirs (Hongjiadu, Dongfeng, and Wujiangdu) during thermal stratification period in the upper reaches of Wujiang River. The results showed that N2O concentrations were 14.3-64.4, 16.5-35.7, and 17.0-70.8 nmol·L-1 in Hongjiadu, Dongfeng and Wujiangdu reservoirs, respectively. Theseresults indicated that all three reservoirs act as N2O source to the atmosphere. There was a significant correlation between ΔN2O and apparent oxygen utilization (AOU) in the whole profile of Dongfeng reservoir as well as above the hypoliminion (0-58 m) of Wujiangdu reservoir. This suggested that N2O production is primarily dominated by nitrification. The vertical distribution of DO, NO3--N, and N2O in hypoliminion of Wujiangdu and Hongjiadu reservoirs showed that N2O production in the hypoliminion of Wujiangdu Reservoir could mostly result from denitrification driven by insitu NO3-, while that of Hongjiadu Reservoir could mainly result from denitrification driven by the exogenous NO3- from upper layer water. N2O emission fluxes in the waterair interfaces in Hongjiadu, Dongfeng and Wujiangdu reservoirs were 0.4, 0.5 and 0.4 μmol·m-2·h-1, respectively. They were significantly higher than former measured values that conducted ten years ago. This implies that the enhanced N2O emission could presumably come from reservoir aging, water regulation of the reservoirs, and enhanced biogeochemical transformation of organic matter under climate changes. The N2O emission fluxes during power generation in July were 0.19×104, 1.6×104 and 6.7×104 mol in the outflow waters of Hongjiadu, Dongfeng and Wujiangdu reservoirs, respectively. The enhanced discharge of N2O from outflow waters may be affected by the joint scheduling and water regulation between the reservoirs in the cascade-developed river-reservoir system.

Key words: cascade reservoir, greenhouse gas, nitrogen cycling, hypoliminion, nitrous oxide.