High-frequency measurements of methane ebullition over a growing season at a temperate peatland site

Abstract

Bubbles can contribute a significant fraction of methane emissions from wetlands; however the range of reported fractions is very large and accurate characterization of this pathway has proven difficult. Here we show that continuous automated flux chambers combined with an integrated cavity output spectroscopy (ICOS) instrument allow us to quantify both CH 4 ebullition rate and magnitude. For a temperate poor fen in 2009, ebullition rate varied on hourly to seasonal time scales. A diel pattern in ebullition was identified with peak release occurring between 20:00 and 06:00 local time, though steady fluxes (i.e., those with a linear increase in chamber headspace CH 4 concentration) did not exhibit diel variability. Seasonal mean ebullition rates peaked at 843.5 384.2 events m -2 d -1 during the summer, with a mean magnitude of 0.19 mg CH 4 released in each event. Copyright 2011 by the American Geophysical Union.