DU Qiqi1, LI Bogeng2, CAI Hongming1 ,DENG Yue3, WANG Yuchun4
(1. School of Earth System science, Tianjin University, Tianjin 300072, China;
2. Yunnan Bureau of Hydrology and Water Resources, Kunming 650106, China；
3. Yunnan Qidi Industrial Development Co. Ltd., Kunming 650228, China;
4. Department of Water Environment, China Institute of Water Resources and Hydropower Research, Beijing 100038, China)
Abstract：Climate change caused by greenhouse gas emissions has recently become one of the most concerned research issues, but only relatively few studies were performed on the impact of cascade reservoirs on the carbon exchange flux between water and air and on the evaluation of the system as a source or a sink of atmospheric CO2. In this study, surface water samples were collected in 6 cascade reservoirs along the Lancangjiang River from May to November 2019, in order to determine the physical and chemical parameters of these water body, and to evaluate the ion source, the CO2 flux (F(CO2)) released from the water body by calculating CO2 partial pressure (p(CO2)), with the aim of clarifying the impact of the cascade reservoirs on the partial pressure and flux of CO2 between water-air interface. Our results showed that the main ions in the water bodies of these cascade reservoirs were mainly derived from the weathering of carbonate, silicate and evaporite in the catchment, while the contribution of atmospheric input was relatively limited. Considering the geochemical characteristics of all water samples, the magnitude of p(CO2) in the investigated reservoirs might be affected by the biological metabolism, hydrodynamic conditions, and the age of the cascade reservoirs as well. The calculation gave a F(CO2) range of -12.99-334.08 mmol/(m2·d) for the Lancangjiang River cascade reservoirs, with an average value of 43.38 mmol/(m2·d), much larger than 0, suggesting that the Lancangjiang River cascade reservoirs are definitely a source of atmospheric CO2, which needs to be taken into account while investigating the global carbon cycling and the relative climate change. The obvious temporal and spatial changes of F(CO2) value in these reservoirs signifies the strong temporal and spatial variability of released CO2, warranteeing further indeep investigation.
Key words：Lancangjiang River; Cascade reservoirs; Hydrochemical characteristics; CO2 partial pressure; air-water CO2 flux
EARTH AND ENVIRONMENT Vol.51, No.1, Tot No.351, 2023, Page 36
