Diurnal and seasonal variations of CO2 flux across water-air interface in artificial wetland in the boreal zone of China

Using the static chamber method, CO2 flux across the water-air interface of Nihe reservoir was measured for 24 hours over a one-year cycle in China. Gas ebullition and gas emission in winter was not considered in this study. According to our results, Nihe reservoir was a total carbon source (690.42 ± 15.18 mg m⁻² d⁻¹) during the year. The maximum and minimum CO2 flux were 50.52 (mg m⁻² h⁻¹) and 17.87 (mg m⁻² h⁻¹), respectively. The diurnal and seasonal variation of CO2 flux was obvious: the CO2 emission during the daytime was lower than night; the CO2 flux was highest in summer (31.52±2.27 mg m⁻² h⁻¹), and lowest in fall (25.03 ± 3.21 mg m⁻² h⁻¹). CO2 emission was negatively correlated with temperature, wind speed, and chlorophyll, while positively correlated with alkalinity. Ultimately, no single environmental factor can solely responsible for CO2 flux.