Characteristics of methane emissions in the Living Water Garden in Chengdu City from 2012 to 2017

CH 4 flux measured by a portable chamber using an infrared analyzer was compared with the flux by static chamber measurement for CW at 13 different sites from May 2012 to May 2017 in the Living Water Garden (LWG) in Chengdu, Sichuan Province, China, over 4 timescales (daily, monthly, seasonal, and annual). During the measurement period, a total of 1443 data were collected. CH 4 fluxes were measured using the portable chamber method and the results showed that the annual mean and median CH 4 flux values in the LWG were 17.4 mg m −2 h −1 and 6.2 mg m −2 h −1 , respectively, ranging from − 19.7 to 98.0 mg m −2 h −1 . Cumulative CH 4 emissions for LWG ranged from − 0.17 to 0.86 kg m −2 year −1 . Global warming potential (GWP, 25.7 kg CO 2eq m −2 year −1 ) was at a high level, which means that the LWG was a source of CH 4 emissions. Significant temporal variations on the 4 timescales were observed. And the asymmetry of measurement uncertainty of CH 4 flux increases with the timescale. Although the total mean CH 4 flux measured by the portable chamber method was 42.1% lower than that of the static chamber method, the temporal variation trends of CH 4 flux were similar. The uncertainty of CH 4 flux measured in portable chamber was more symmetrical than that in static chamber. These results suggest that the portable chamber method has considerable value as a long-term measurement method for CH 4 flux temporal variations.