Author(s):
Nölscher, Anke C. ; Yáñez-Serrano, Ana Maria ; Wolff, Stefan ; Araüjo, Alessandro Carioca de ; Lavric, J. V. ; Kesselmeier, Jürgen ; Williams, Jonathan C.
Date: 2020
Origin: Oasisbr
Subject(s): Isoprene; Air Quality; Atmospheric Pollution; Concentration (composition); Hydroxyl Radical; Isoprene; Photochemistry; Pollutant Removal; Pristine Environment; Quantitative Analysis; Rainforest; Reaction Kinetics; Seasonality; Trace Gas; Turbulent Mixing; Dry Season; Environmental Parameters; Environmental Temperature; Gas; Photochemistry; Rainforest; Rainforest Air Reactivity; Season; Seasonal Variation; Wet Season; Amazonas; Brasil
Description
The hydroxyl radical (OH) removes most atmospheric pollutants from air. The loss frequency of OH radicals due to the combined effect of all gas-phase OH reactive species is a measureable quantity termed total OH reactivity. Here we present total OH reactivity observations in pristine Amazon rainforest air, as a function of season, time-of-day and height (0-80 m). Total OH reactivity is low during wet (10s-1) and high during dry season (62s-1). Comparison to individually measured trace gases reveals strong variation in unaccounted for OH reactivity, from 5 to 15% missing in wet-season afternoons to mostly unknown (average 79%) during dry season. During dry-season afternoons isoprene, considered the dominant reagent with OH in rainforests, only accounts for ∼20% of the total OH reactivity. Vertical profiles of OH reactivity are shaped by biogenic emissions, photochemistry and turbulent mixing. The rainforest floor was identified as a significant but poorly characterized source of OH reactivity.
