Spatiotemporal distribution of nitrous oxide (N2O) emissions from cascade reservoirs in Lancang‐Mekong River Yunnan section, Southwestern China. (22nd September 2020)

• Record Type: Journal Article
• Authors: Wu, Wei; Wang, Jiawei; Zhou, Xiaode; Yuan, Bo; Guo, Mengjing; Ren, Lei
• Other Names: Yin Xinan guestEditor.; Mao Xufeng guestEditor.
• Is Part Of: River research and applications. Volume 37:Number 8(2021)
• Page Start: 1055
• Page End: 1069
• Publication Date: 2020-09-22
• Subjects: cascade reservoirs -- damming -- Lancang River -- N2O emission; Rivers -- Regulation -- Periodicals; Rivers -- Periodicals; 551.483
• DOI: 10.1002/rra.3726
• Languages: English
• ISSNs: 1535-1459

Abstract

Abstract: The current issue of river damming causing the release of greenhouse gas nitrous oxide (N2 O) from reservoirs has led to a debate over whether hydropower can still provide clean energy. In January (dry season) and August 2019 (wet season), we detected the N2 O concentrations from cascade reservoirs in Lancang‐Mekong River Yunnan section by using static headspace gas chromatography and estimated the emission flux by the boundary layer approach to explore the influencing factors, especially the impact of cascade reservoirs development and operation. In the Lancang River (Yunnan section), the longitudinal distribution of N2 O concentration along the cascade reservoirs showed seasonal differences. The average concentrations of N2 O during the dry season and the wet season were 13.50 ± 2.00 nmol/L and 16.40 ± 4.10 nmol/L, respectively. The reservoirs with thermal stratification in both seasons were the Xiaowan (XW), Nuozhadu (NZD), and Jinghong (JH) reservoirs. The vertical distribution of N2 O concentration was depth dependent (i.e., the deeper the location, the higher the concentration) in reservoirs with thermal stratification and uniform in reservoirs without thermal stratification. Dissolved oxygen (DO), water temperature, and other biogenic elements were the main factors affecting N2 O distribution. The average N2 O emission flux in the cascade reservoirs was 12.80 ± 2.60 μmol m 2 ·day −1 during the dry season and 16.10 ± 4.75 μmol m 2 ·day −1 during the wet season. The annual average N2 O emission fluxes of all reservoirs were in an order of JH > XW > Dachaoshan (DCS) > NZD > Miaowei (MW) > Gongguoqiao (GGQ) > Manwan (Man W). In 2019, a total of 3.37 × 10 6 mol year −1 (94.39 ton N2 O‐N year −1 ) was released from the water surface of the cascade reservoirs, which accounted for approximately 0.31% of the total N2 O emissions from reservoirs worldwide. This study shows the cascade reservoirs development and operations have made the Lancang River (Yunnan section) a major area for N2 O emissions.