Gas‐phase chemistry dominates O3 loss to a forest, implying a source of aerosols and hydroxyl radicals to the atmosphere

Abstract

Tropospheric ozone (O3) effectively deposits to forested ecosystems but the fate of O3 within the forest canopy is unresolved. We partitioned total measured ecosystem daytime O3 deposition to a ponderosa pine (Pinus ponderosa) forest into its major loss pathways; stomatal uptake, non‐stomatal surface deposition, and gas‐phase chemistry. Total O3 flux was dominated by gas‐phase chemistry during the summer and by stomatal uptake during winter. O3 loss due to gas‐phase chemistry was exponentially dependent on temperature, with the same functionality as biogenic hydrocarbon emissions, implicating reactions with biogenic hydrocarbons as the likely gas‐phase chemical O3 loss process within the canopy. The reaction of O3 with biogenically‐emitted hydrocarbons leads to both hydroxyl radical formation and secondary aerosol growth with important effects on atmospheric chemistry and climate.