Spatiotemporal variations of nitrous oxide (N2O) emissions from two reservoirs in SW China |
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| Authors: | Xiao-Long Liu Cong-Qiang Liu Si-Liang Li Fu-Shun Wang Bao-Li Wang Zhong-Liang Wang |
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| Institution: | 1. Tianjin Key Laboratory of Water Resources and Environment, Tianjin Normal University, Tianjin 300387, China;2. The State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, No.46, Guanshui Road, Guiyang 550002, China;3. Applied Radiation Institute, School of Environmental and Chemical Engineering, Shanghai University, Shangda Road 99, Baoshan, Shanghai 200444, China;1. State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China;2. College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210008, China;3. College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China;1. Fujian Provincial Key Laboratory for Coastal Ecology and Environmental Studies, College of the Environment and Ecology, Xiamen University, Xiamen, Fujian, China;2. Key Laboratory of the Coastal and Wetland Ecosystems, Xiamen University, Xiamen, Fujian, China;3. Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Beijing, China;1. The Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, PR China;2. Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, PR China;3. University of Chinese Academy of Sciences, Beijing 100049, PR China;1. Fujian Provincial Key Laboratory for Coastal Ecology and Environmental Studies, College of the Environment and Ecology, Xiamen University, Xiamen, China;2. Key Laboratory of the Coastal and Wetland Ecosystems, Ministry of Education, Xiamen University, Xiamen, China;1. Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization, Ecological Restoration Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China;2. Zoige Peatland and Global Change Research Station, Chinese Academy of Sciences, Hongyuan 624400, China;3. University of Chinese Academy of Sciences, Beijing 100049, China;4. Wetland Science Research Center of the Upper Reaches of the Yangtze River, Chongqing Normal University, Chongqing 400047, China;5. College of Geography and Tourism, Chongqing Normal University, Chongqing 400047, China;6. State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400030, China;7. College of Resources and Environmental Science, Chongqing University, Chongqing 400030, China;1. Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China;2. International Centre for Integrated Mountain Development, Kathmandu GPO Box 3226, Nepal;3. Institute of Environment Sciences, University of Quebec at Montreal, Montreal C3H 3P8, Canada;4. Zoige Peatland and Global Change Research Station, Chinese Academy of Sciences, Hongyuan 624400, China;5. College of Forestry, Northwest Agriculture and Forest University, Yanglin 712100, China;6. College of Resources and Environment, Chongqing University, Chongqing, China;7. Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China;8. Sustainable Resource Management, Memorial University of Newfoundland, Corner Brook, A2H 6P9, Canada |
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| Abstract: | Greenhouse gas emissions from hydroelectric dams have recently given rise to controversies about whether hydropower still provides clean energy. China has a large number of dams used for energy supply and irrigation, but few studies have been carried out on aquatic nitrous oxide (N2O) variation and its emissions in Chinese river-reservoir systems. In this study, N2O spatiotemporal variations were investigated monthly in two reservoirs along the Wujiang River, Southwest China, and the emission fluxes of N2O were estimated. N2O production in the reservoirs tended to be dominated by nitrification, according to the correlation between N2O and other parameters. N2O saturation in the surface water of the Wujiangdu reservoir ranged from 214% to 662%, with an average fluctuation of 388%, while in the Hongjiadu reservoir, it ranged from 201% to 484%, with an average fluctuation of 312%. The dissolved N2O in both reservoirs was over-saturated with respect to atmospheric equilibrium levels, suggesting that the reservoirs were net sources of N2O emissions to the atmosphere. The averaged N2O emission flux in the Wujiangdu reservoir was 0.64 μmol m?2 h?1, while it was 0.45 μmol m?2 h?1 in the Hongjiadu reservoir, indicating that these two reservoirs had moderate N2O emission fluxes as compared to other lakes in the world. Downstream water of the dams had quite high levels of N2O saturation, and the estimated annual N2O emissions from hydropower generation were 3.60 × 105 and 2.15 × 105 mol N2O for the Wujiangdu and the Hongjiadu reservoir, respectively. These fluxes were similar to the total N2O emissions from the reservoir surfaces, suggesting that water released from reservoirs would be another important way for N2O to diffuse into the atmosphere. It can be concluded that dam construction significantly changes the water environment, especially in terms of nutrient status and physicochemical conditions, which have obvious influences on the N2O spatiotemporal variations and emissions. |
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