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Published January 2016 | Supplemental Material + Published
Journal Article Open

Unexpected seasonality in quantity and composition of Amazon rainforest air reactivity

Abstract

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 (10 s^(−1)) and high during dry season (62 s^(−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.

Additional Information

© 2016 Nature Publishing Group. This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ Received 31 July 2015; Accepted 04 December 2015; Published 22 January 2016. We thank the Max Planck Society and the Instituto Nacional de Pesquisas da Amazonia for continuous support. We acknowledge the support by the German Federal Ministry of Education and Research (BMBF contract 01LB1001A) and the Brazilian Ministério da Ciência, Tecnologia e Inovação (MCTI/FINEP contract 01.11.01248.00) as well as the Amazon State University (UEA), FAPEAM, LBA/INPA and SDS/CEUC/RDS-Uatumã. Particularly acknowledged are the contributions for technical and logistical support (Reiner Ditz, Hermes Braga Xavier, Nina Maria Knothe). Thanks to Guenther Schebeske for the GC-FID analysis, to Thomas Klüpfel for PTR-MS related help, and to Jan Winderlich and Leonardo Ramos de Oliveira for contributing to CO measurements. We greatly appreciate helpful discussions with J.N. Crowley. Contributions: A.C.N. conducted the total OH reactivity measurements, analysis and wrote the manuscript. A.M.Y.S. was in charge of the VOC PTR-MS observations and analysis. All the work was achieved under the supervision of J.W. and J.K. who helped in the scientific analysis and the manuscript writing process. S.W. provided the gradient system and NOx and Ozone data. J.V.L. provided CO data and A.C.A. was in charge of the micrometeorological observations. The authors declare no competing financial interests.

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Published - ncomms10383.pdf

Supplemental Material - ncomms10383-s1.pdf

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Additional details

Created:
August 20, 2023
Modified:
October 17, 2023