[Comparison of Floating Chamber and Diffusion Model Methods for Measuring Methane Emissions from Inland Fish-Aquaculture Ponds].

Freshwater aquaculture ponds collectively cover a large area in southeast China. They are an important anthropogenic source of CH emissions, however current knowledge of CH emissions from aquaculture ponds is limited. During September 2017 and August 2018, two independent sampling campaigns of CH flux measurements over annual cycles were carried out in a fish-aquaculture pond in southeast China using a floating chamber and diffusion model methods for comparison. The purpose of this study is to investigate the variation of CH fluxes obtained from the fish-aquaculture pond, analyze the emission mechanisms, and amplify the CH emissions inventory. The diffusion model method can further quantify the contribution of diffusion transmission to CH emissions. The seasonal variations of CH fluxes measured by the two methods were similar, with higher CH fluxes appearing in summer and fall and lower CH fluxes appearing in spring and winter. CH fluxes measured by the floating chamber method and diffusion model method ranged from 0.14-3.13 mg·(m·h) and 0.04-1.41 mg·(m·h), respectively, and the respective average values were (0.86±0.30) mg·(m·h)and (0.45±0.08) mg·(m·h). The CH fluxes were positively related to water temperature, dissolved organic carbon (DOC) and chemical oxygen demand (COD), but negatively related to the water dissolved oxygen (DO) concentration in the fish-aquaculture pond. CH fluxes calculated by diffusion model methods were 45% lower than those determined by the floating chamber methods over annual cycles. The result suggested that the floating chamber method is more suitable than the diffusion model method for measurements of CH fluxes in freshwater aquaculture ecosystems.