Timescale dependence of environmental controls on methane efflux in Poyang Lake, China

Other literature type English OPEN
Liu, Lixiang ; Xu, Ming ; Shao, Rui (2016)

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&thinsp;mmol&thinsp;m<sup>&minus;2</sup>&thinsp;day<sup>&minus;1</sup>, ranging from 0.47 to 0.60&thinsp;mmol&thinsp;m<sup>&minus;2</sup>&thinsp;day<sup>&minus;1</sup>. The CH<sub>4</sub> efflux had a high seasonal variation with an average summer (June to August) efflux of 1.34&thinsp;mmol&thinsp;m<sup>&minus;2</sup>&thinsp;day<sup>&minus;1</sup> and winter (December to February) efflux of merely 0.18&thinsp;mmol&thinsp;m<sup>&minus;2</sup>&thinsp;day<sup>&minus;1</sup>. The efflux showed no apparent diel pattern, although most of the peak effluxes appeared in the late morning, from 10:00&thinsp;h to 12:00&thinsp;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.
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