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Single-throughput Complementary High-resolution Analytical Techniques for Characterizing Complex Natural Organic Matter Mixtures
Published on: January 7, 2019
Atmospheric oxidation capacity sustained by a tropical forest.
J Lelieveld1, T M Butler, J N Crowley
1Max Planck Institute for Chemistry, 27 Becherweg, 55128 Mainz, Germany. lelieveld@mpch-mainz.mpg.de
Nature
|April 11, 2008
Summary
Tropical forests release volatile organic compounds (VOCs) that surprisingly maintain high atmospheric hydroxyl radical (OH) levels. This suggests a natural mechanism for atmospheric self-cleaning, even in pristine environments.
Area of Science:
- Atmospheric Chemistry
- Biogeochemistry
- Environmental Science
Background:
- Terrestrial vegetation, particularly tropical rainforests, emits substantial volatile organic compounds (VOCs) into the atmosphere.
- Atmospheric oxidation, primarily driven by hydroxyl radicals (OH), removes these VOCs.
- Previously, biogenic VOCs were thought to deplete OH in unpolluted air, reducing atmospheric oxidation capacity.
Purpose of the Study:
- To investigate atmospheric trace gas concentrations over the Amazon rainforest.
- To understand the unexpectedly high hydroxyl radical (OH) concentrations observed.
- To explore the role of biogenic VOC oxidation in maintaining atmospheric oxidation capacity in low-nitrogen oxide (NOx) environments.
Main Methods:
- Aircraft-based measurements of atmospheric trace gases over the Amazon forest.
- Atmospheric chemistry modeling.
- Laboratory experiments investigating isoprene oxidation mechanisms.
Main Results:
- Observed unexpectedly high concentrations of hydroxyl radicals (OH) in the pristine Amazonian atmosphere.
- Proposed that the oxidation of natural VOCs, especially isoprene, efficiently recycles OH in low-NOx conditions.
- Model computations and laboratory results suggest 40-80% OH recycling efficiency in isoprene oxidation explains the observed high OH levels.
Conclusions:
- The biosphere plays a crucial role in maintaining atmospheric oxidation balance through efficient OH recycling.
- Biogenic VOC oxidation is a significant factor in regulating atmospheric chemistry, even in remote, unpolluted regions.
- Further laboratory studies are needed to fully elucidate the chemical mechanisms behind OH recycling in isoprene oxidation.
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