Aircraft-Based AirCore Sampling for Estimates of N₂O and CH₄ Emissions

Airborne measurements offer an effective way to quantify urban emissions of greenhouse gases (GHGs). However, it may be challenging due to the requirement of high measurement precision and sufficiently enhanced signals. We developed a new active AirCore system based on the previous unmanned aerial vehicle (UAV) version, which is capable of sampling atmospheric air for several hours aboard a lightweight aircraft for postflight simultaneous and continuous measurements of N₂O, CH₄, CO₂, and CO. We performed 13 flights over the urban areas of Groningen, Utrecht, and Rotterdam and evaluated the aircraft-based AirCore measurements against in situ continuous CH₄ measurements. One flight was selected for each of the three urban areas to quantify the emissions of N₂O and CH₄. Compared to the Dutch inventory, the estimated N₂O emissions (364 ± 143 kg h^-1) from the Rotterdam area are ∼3 times larger, whereas those for Groningen (95 ± 90 kg h^-1) and Utrecht (32 ± 16 kg h^-1) are not significantly different. The estimated CH₄ emissions for all three urban areas (Groningen: 2534 ± 1774 kg CH₄ hr^-1, Utrecht: 1440 ± 628 kg CH₄ hr^-1, and Rotterdam: 2419 ± 922 kg CH₄ hr^-1) are not significantly different from the Dutch inventory. The innovative aircraft-based active AirCore sampling system provides a robust means of high-precision and continuous measurements of multiple gas species, which is useful for quantifying GHG emissions from urban areas.