Review: Exchanges of O₃, NO, and NO₂ between forest ecosystems and the atmosphere

Abstract

The emission and absorption of trace gases in the biosphere affect atmospheric chemistry and influence the potential indirect effects on the carbon and nitrogen cycles, air pollution, and climate. Ozone (O 3 ) and nitrogen oxides are important for the atmosphere and have adverse effects on plant growth and human health. In this review, the observed fluxes and deposition velocities of O 3 , NO, and NO 2 in various forest ecosystems and the commonly used measurement methodologies were summarized and compared. Canopy O 3 fluxes have been reported in evergreen coniferous and deciduous broadleaf forests. O 3 deposition was observed in the forest ecosystems during daytime and nighttime, because O 3 is absorbed through stomata, deposited on the surface of the plant and the ground, and lost through forest chemical reactions. There were no significant differences in O 3 fluxes and deposition velocities in broadleaf and coniferous forests during the summer. The O 3 flux in the forest at night were 15 ± 8% and 22 ± 7% of those at daytime for broadleaf and coniferous forests, respectively. The observed NO flux was both negative (deposition) and positive (emission), whereas that of NO 2 was only positive during the daytime in summerautumn. NO 2 emissions mechanisms have been discussed in terms of NO emissions from forest soil, NO 2 absorption and emission by plant leaves through stomata, and NO and NO 2 concentration gradients caused by photochemical reactions according to the differences in sunlight intensity inside and outside the forest. Nitrates attached to leaves are possible sources of NO 2 . Simultaneous measurements of O 3 , NO, and NO 2 fluxes are important in different vegetation types for investigating the differences between vegetation types and for developing a global forest inventory of NO and NO 2 fluxes, and O 3 deposition because of their closely related exchange mechanisms.

Measurements of nitrogen dioxide fluxes in the surface layer for the territory of the Fonovaya Observatory

“…The maximum was observed in October, with a value of 0.3 nmol/(m2s). The obtained flux values are consistent with the data presented in other studies, such as [8].…”

Improving model representation of rapid ozone deposition over soil in the central Tibetan Plateau

“…The v d observed here is comparable to typical v d in forests and one of the highest previously reported over bare soils. 33,58,59 Notably, a high nighttime v d of approximately 0.4 cm s −1 is observed, which is among the top values ever reported. 33 Although nighttime v d has larger uncertainty than that of daytime, quite high u * and z / L much less than 1 during nighttime favored high nighttime v d at NMC.…”

“…Parts of reported R c are obtained by 1/v d minus prescribed R a + R b (50 s m −1 during daytime and 200 s m −1 during nighttime). Data from 24,26,[58][59][60][61][62][63][64][65][66][67].…”