Emission of Carbon Dioxide and Methane from Duckweed Ponds for Stormwater Treatment

This study determined the greenhouse gas emission from two laboratory-scale duckweed ponds for stormwater treatment. The rate of carbon dioxide (CO2) emission from the two duckweed systems was 1472 ± 721 mg/m2·d and 626 ± 234 mg/m2·d, respectively. After the removal of duckweeds, CO2 emissions decreased to 492 ± 281 mg/m2·d and 395 ± 53 mg/m2·d, respectively. The higher CO2 emissions in the duckweed systems were attributed to duckweed biomass decay on the pond soil surface. A thin-film model was able to predict the increasing CO2 concentrations in the closed static chamber during 2 weeks of sampling. The initial methane fluxes from the duckweed systems were 299 ± 74 mg/m2·d and 180 ± 91 mg/m2·d, respectively. After the removal of duckweeds, the flux increased to 559 ± 215 mg/m2·d and 328 ± 114 mg/m2·d, respectively.