Mitigation of N 2 O Emission from Aquaponics by Optimizing the Nitrogen Transformation Process: Aeration Management and Exogenous Carbon (PLA) Addition.

N2 O production in aquaponics is an inevitable concern when aquaponics is developed as a future production system. In the present study, two attempts were applied to mitigate N2 O emission from aquaponics, i.e., aeration in hydroponic bed (HA) and addition of polylactic acid (PLA) into fillers (PA). Results showed that N2 O emission from HA and PA was decreased by 47.1-58.1% and 43.2-74.9% respectively compared with that in control. Denitrification was proved to be the main emission pathway in all treatments, representing 62.4%, 86.4%, and 75.8% of the total N2 O emission in HA, PA, and control, respectively. However, production of plants in HA was severely impaired, which was only 3.04 ± 0.39 kg/m2 , while in PA and control, plants yields were 4.87 ± 0.56 kg/m2 and 4.33 ± 0.58 kg/m2 . Combining the environmental and economic benefits, adding PLA in aquaponics may have a better future when developing and applying aquaponics systems.