Abstract
Methane flux from the air-water interface of freshwater-covered wetland ponds is shown to increase approximately as the square of the air velocity over the water surface. CH4 fluxes were measured using a partitioned chamber placed over the water surface where the air velocity along the surface can be controlled. Correlating measurements of CH4 fluxes and surface water dissolved CH4 concentrations to air velocities provide a means to evaluate the liquid phase exchange coefficient (k1) for a two-layer model of the gas-liquid interface. The liquid phase exchange coefficient for CH4 is calculated as k1 = 1.7 cm-1 for air velocities of zero and as kt = 1.1 + 1.2 v1.96 cm h-1 for air velocities from 1.4 to 3.5 m s-1 and water temperatures of 2O°C. Surface water dissolved CH4 concentrations of the wetland ponds used in this study varied from 10 to 780μg I-1, resulting in CH4 flux measurements from 0.01 to 1.22 g m-2day-1.