Evening Methane Emission Pulses from a Boreal Wetland Correspond to Convective Mixing in Hollows

Spatial and temporal heterogeneity of methane flux from boreal wetlands makes prediction and up-scaling challenging, both within and among wetland systems. Drivers of methane production and emissions are also highly variable, making empirical model development difficult and leading to uncertainty in methane emissions estimates from wetlands. Previous studies have examined this problem using point-scale (static chamber method) and ecosystem-scale (flux tower methods) measurements, but few studies have investigated whether different processes are observed at these scales. We analyzed methane emissions from a boreal fen, measured by both techniques, using data from the Boreal Ecosystem-Atmosphere Study. We sought to identify driving processes associated with methane emissions at two scales and explain diurnal patterns in emissions measured by the tower. The mean methane emission rates from flux chambers were greater than the daytime, daily mean rates measured by the tower, but the nighttime, daily mean emissions from the tower were often an order of magnitude greater than emissions recorded during the daytime. Thus, daytime measurements from either the tower or chambers would lead to a biased estimate of total methane emissions from the wetland. We found that the timing of nighttime emission events was coincident with the cooling and convective mixing within hollows, which occurred regularly during the growing season. We propose that diurnal thermal stratification in shallow pools traps methane by limiting turbulent transport. This methane stored during daytime heating is later released during evening cooling due to convective turbulent mixing

Triclosan: An Instructive Tale

The Food and Drug Administration (FDA) recently released a final rule to ban triclosan and 18 other antimicrobial chemicals from soaps. We applaud this rule specifically because of the associated risks that triclosan poses to the spread of antibiotic resistance throughout the environment. This persistent chemical constantly stresses bacteria to adapt, and behavior that promotes antibiotic resistance needs to be stopped immediately when the benefits are null