A System for Measuring Methane Fluxes from Inland and Coastal Wetland Environments

Abstract

AbstractA technique for field measurements of methane fluxes at a water‐atmosphere interface as a function of air velocity has been developed and tested. The method uses a partitioned chamber placed over the water surface where the air velocity along the surface can be controlled. CH4 fluxes as low as 2 × 10−3 (± 0.05) g m−2 day−1 were measured in this way, and additional CH4‐flux data were determined as functions of air velocity from 0.9 (± 0.1) m sec−1 to 4.4 (± 0.37) m sec−1. Emission rates of gas across an air‐water interface is controlled by shear stress of winds in the overlying gas. Our objective was to develop a relatively simple field system which had the capability of quantitatively controlling air velocity over the water surface within the chamber sampling area. This technique has the important advantage of including a continuous monitoring system so that data can be observed on site. Measurements obtained in a coastal wetland creek demonstrate that the CH4 flux passing through a water‐atmosphere interface can be quantified as a function of air velocity over the water surface.