Ozone (O3) is a strong oxidant formed of three oxygen molecules. Majority of the atmospheric ozone (about 90%) is located in the stratosphere at the height of some 10–50 km where it protects from the incoming UV-radiation. Ozone hole is formed when the stratospheric ozone is destroyed. The oxidation of e.g. volatile organic compounds occurs in the troposphere, below 10 km, what we refer to the atmosphere. The tropospheric ozone is harmful to plants where it causes e.g. cell damage and it causes respiratory symptoms to sensitive people e.g. asthmatics.
Ozone is one of the most important oxidants in the atmosphere and the (tropospheric) concentrations are typically highest in the spring and summer. Other major atmospheric oxidants are hydroxyl radical (OH) and nitrate (NO3). The animation shows the reaction of monoterpene (α-pinene) with ozone: The oxidation products can be further oxidized in reactions with ozone or other oxidants.
VOC emissions from the boreal canopy are oxidized into ELVOC (extremely low volatile organic compounds) emissions and these compounds drive the NPF (new particle formation) events in the atmosphere.