Diffusive CH4 fluxes from aquaculture ponds using floating chambers and thin boundary layer equations. (15th May 2021) - Yang, Ping
Abstract: Static floating chambers ( FCs ) are the conventional method to measure CH4 fluxes across the water-air interface in ponds, while thin boundary layer ( TBL ) modelling is increasingly used to estimate CH4 fluxes. In this study, both FCs measurements and TBL models of gas transfer velocity were used to determine CH4 evasion from aquaculture ponds in southeastern China. The surface water CH4 concentrations ranged from 0.4 to 9.1 μmol L-1 with an average of 4.8 ± 0.8 μmol L-1. CH4 flux was always positive, indicating the ponds as a persistent CH4 source to air. Mean CH4 flux based on different TBL models showed large variations, ranging between 19 and 316 μmol m −2 h −1 . Compared against the direct measurement FCs, three TBL models developed for the open sea, flowing estuarine system and lentic ecosystem ( TBL W92a, TBL RC01, and TBL CL98, respectively) overestimated CH4 emission by 40–200%, while the wind tunnel-based TBL model ( TBL LM86 ) underestimated CH4 emission. Two TBL models developed for lakes ( TBL W92b and TBL CW03 ) gave estimates similar to FCs . H I G H L I G H T S: Aquaculture ponds emit CH4 . Large variations in diffusive CH4 fluxes are estimated by different thin boundary layer (TBL) models. Methane fluxes measured by chambers and match those estimated by only some TBL models.