Timescale dependence of environmental controls on methane efflux in Poyang Lake, China
Other literature type
(issn: 1726-4189, eissn: 1726-4189)
Lakes are an important natural source of CH<sub>4</sub> to the atmosphere. However, the long-term CH<sub>4</sub> efflux in lakes has been rarely studied. In this study, the CH<sub>4</sub> efflux in Poyang Lake, the largest freshwater lake in China, was measured continuously over a 4-year period by using the floating chamber technique. The mean annual CH<sub>4</sub> efflux throughout the 4 years was 0.54 mmol m<sup>−2</sup> day<sup>−1</sup>, ranging from 0.47 to 0.60 mmol m<sup>−2</sup> day<sup>−1</sup>. The CH<sub>4</sub> efflux had a high seasonal variation with an average summer (June to August) efflux of 1.34 mmol m<sup>−2</sup> day<sup>−1</sup> and winter (December to February) efflux of merely 0.18 mmol m<sup>−2</sup> day<sup>−1</sup>. The efflux showed no apparent diel pattern, although most of the peak effluxes appeared in the late morning, from 10:00 h to 12:00 h. Multivariate stepwise regression on a seasonal scale showed that environmental factors, such as sediment temperature, sediment total nitrogen content, dissolved oxygen, and total phosphorus content in the water, mainly regulated the CH<sub>4</sub> efflux. However, the CH<sub>4</sub> efflux only showed a strong positive linear correlation with wind speed within a day on a bihourly scale in the multivariate regression analyses but almost no correlation with wind speed on diurnal and seasonal scales.