Published July 2024 | Version Published
Journal Article Open

Interactions of peroxy radicals from monoterpene and isoprene oxidation simulated in the radical volatility basis set

Abstract

Isoprene affects new particle formation rates in environments and experiments also containing monoterpenes. For the most part, isoprene reduces particle formation rates, but the reason is debated. It is proposed that due to its fast reaction with OH, isoprene may compete with larger monoterpenes for oxidants. However, by forming a large amount of peroxy-radicals (RO2), isoprene may also interfere with the formation of the nucleating species compared to a purely monoterpene system. We explore the RO2 cross reactions between monoterpene and isoprene oxidation products using the radical Volatility Basis Set (radical-VBS), a simplified reaction mechanism, comparing with observations from the CLOUD experiment at CERN. We find that isoprene interferes with covalently bound C20 dimers formed in the pure monoterpene system and consequently reduces the yields of the lowest volatility (Ultra Low Volatility Organic Carbon, ULVOC) VBS products. This in turn reduces nucleation rates, while having less of an effect on subsequent growth rates.

Copyright and License

This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence.

Acknowledgement

This work is dedicated to the memory of Astrid Kiendler-Scharr. It was supported by: Grant CHE2336463 from the U.S. National Science Foundation; the Vienna Science and Technology Fund (WWF) through project VRG22-003; Grant number PZ00P2_216181 from the Swiss National Science Foundation Ambizone Scheme; Grant number 200021_213071 from the Swiss National Foundation; and the European Research Council project NANODYNAMITE (ERC 616075).

Contributions

MS and NMD conceived the project and designed the overall scope. MS implemented and executed the radical VBS model. MS and NMD wrote the manuscript. FB, LD, SB, JD, IEH, HF, XCH, MH, AK, CK, JK, MK, KL, BL, VM, BM, UM, WN, TP, LQ, DS, RV, AW, MW, PW, CY and QY prepared the CLOUD facility and instruments and engaged in scientific discussion regarding the paper.

Data Availability

The data unique to this work are the rate coefficients and reaction sequence contained in the ESI.

Supplementary information

Supplementary information

Conflict of Interest

The authors declare no conflicts.

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Additional details

Identifiers

Funding

National Science Foundation
CHE-2336463
Vienna Science and Technology Fund
VRG22-003
Swiss National Science Foundation
200021_213071
Swiss National Science Foundation
PZ00P2_216181
European Research Council
616075