Journal Article

Dynamics of dissolved greenhouse gas response to seasonal water mixing in subtropical reservoirs

Yangyang Cai, Zhenglun Yang, Xing Li, Changyuan Tang, Han Zhang

2019

Overview

Although indispensable, significant uncertainty still exists in the underlying processes of the formation, dynamics, and emission of greenhouse gases (GHGs), the critical elements needed for the accurate estimation of greenhouse gas fluxes in inland lakes and reservoirs. Seasonal changes in water thermal stratification and turbulence strongly influence the concentration and emission of dissolved GHGs in water columns. Here, we studied the stratification and overturn processes of water column in the subtropical Lianhe Reservoir during different seasons and determined the dynamics of dissolved CO 2 , CH 4 , and N 2 O in the reservoir. Observation of temperature and analysis of chlorofluorocarbons (CFCs) clearly suggested that stratification of water column occurred in summer, but not in winter. The results showed that while dissolved oxygen (DO) was high in the top 5-m layer (the upper epilimnion layer), it dropped considerably especially below 10 m, resulting in an increase in concentration of CO 2 and CH 4 . The high concentrations of dissolved N 2 O and CH 4 were related to the decomposition of organic matter in the hypolimnion layer under anaerobic conditions after stratification. In winter overturn period, vertical circulants of water not only homogenized the concentration of DO in the water column, but also potentially moved CO 2 , CH 4 , and N 2 O from the bottom to the surface of the reservoir. The estimated GHG flux from the reservoir was − 7.13 mmol m −2 day −1 in summer and 2.14 mmol m −2 day −1 in winter. There was the potential that CO 2 fluxes from subtropical lakes and reservoirs are overestimated by traditional geochemical models.

• Publisher: Springer Science and Business Media LLC,Springer International Publishing,Springer Nature B.V
• Subject: Anaerobic conditions / Anoxic conditions / Aquaculture / Aquatic ecosystems / Atmospheric Protection/Air Quality Control/Air Pollution / Biogeochemistry / Carbon Dioxide / Carbon dioxide concentration / Carbon dioxide flux / Chlorofluorocarbons / Climate change / Dissolved oxygen / Earth and Environmental Science / Ecology / Ecotoxicology / Emission / Environment / Environmental Management / Environmental Monitoring / Epilimnion / Fluxes / greenhouse gas emissions / Greenhouse Gases / Hydrology / Hypolimnion / Lakes / Methane / mixing / Monitoring/Environmental Analysis / Nitrates / Nitrous oxide / Organic matter / Overturn / Oxygen / Photosynthesis / Reservoirs / Respiration / Seasonal variation / Seasonal variations / Seasons / Summer / temperature profiles / Thermal stratification / Turbulence / turbulent flow / uncertainty / Water / Water circulation / Water column / Water mixing / Water quality / Water stratification / Water temperature / Winter