Soil atmosphere gas exchange of NO, NOx and O3

The forest floor NO, NO_x and O₃ flux is measured by three automatic dynamic flow-through chambers (Korhonen et al., 2013). The chamber-system consists of three transparent chambers similar as the automatic CH₄ and N₂O chamber, and fluorinated ethylene-propylene (FEP) film as the transparent material. The operation of the chambers is automated: each chamber is closed for 15 min. Sample air is drawn from the chamber at a rate of 4.1 dm³ min^-1 to a chemiluminescence analyser (TEI 42S, Thermo Environmental Instruments, Philadelphia, PA, USA). At the time of sampling, compensation air from the above canopy atmosphere is directed into the chamber at a rate of 4.5 dm³ min^-1.