Short-term landfill methane emissions dependency on wind

• Atmospheric modeling elucidated dynamics of whole-landfill methane emissions.
• Data filtering techniques developed using atmospheric modeling.
• Whole-landfill emissions at test site varied by factor of 2 over 2 h measurements.
• Modeling and field data indicate wind speed variations caused emissions variability.
• Emissions measurements more accurate using airborne versus ground level data.

Short-term (2–10 h) variations of whole-landfill methane emissions have been observed in recent field studies using the tracer dilution method for emissions measurement. To investigate the cause of these variations, the tracer dilution method is applied using 1-min emissions measurements at Sandtown Landfill (Delaware, USA) for a 2-h measurement period. An atmospheric dispersion model is developed for this field test site, which is the first application of such modeling to evaluate atmospheric effects on gas plume transport from landfills. The model is used to examine three possible causes of observed temporal emissions variability: temporal variability of surface wind speed affecting whole landfill emissions, spatial variability of emissions due to local wind speed variations, and misaligned tracer gas release and methane emissions locations. At this site, atmospheric modeling indicates that variation in tracer dilution method emissions measurements may be caused by whole-landfill emissions variation with wind speed. Field data collected over the time period of the atmospheric model simulations corroborate this result: methane emissions are correlated with wind speed on the landfill surface with R2 = 0.51 for data 2.5 m above ground, or R2 = 0.55 using data 85 m above ground, with emissions increasing by up to a factor of 2 for an approximately 30% increase in wind speed. Although the atmospheric modeling and field test are conducted at a single landfill, the results suggest that wind-induced emissions may affect tracer dilution method emissions measurements at other landfills.

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