Mixing and Deposition in a Jack Pine Forest Canopy

To study how aerosols mix and deposit to forests, a tower was erected in a jack pine forest as part of the York Athabasca Jack Pine project. The tower is surrounded by anthropogenic pollution sources from the Alberta Oil Sands operations.

From previous studies, we expected that canopies inhibit mixing and deposition. During the study, the air within the forest was often decoupled from the air above. Mixing at the study site took up to 40 minutes during periods where the canopy was decoupled, compared to less than 2 minutes when the canopy was coupled.

At different times during the campaign, the forest was either a sink or a source of aerosols. The mean aerosol deposition velocity, an important parameter used by deposition models, was measured in this boreal forest. A local minimum of v_d (with respect to particle diameter) of 0.16 cm/s was observed at D = 150 nm.