| Abstrakt: |
New particle formation (NPF) has been observed at various locations, but NPF does not occur in isoprene‐dominant forests. Recent laboratory studies were conducted to understand the role of isoprene in biogenic NPF, and these studies show that isoprene can suppress biogenic NPF, with contradicting theories. To reconcile these discrepancies, we conducted flow tube experiments of biogenic nucleation under a wide range of isoprene over monoterpene carbon ratios (R) and oxidant conditions (OH vs. ozone). Our results show isoprene either suppresses or enhances biogenic NPF, depending on R and oxidation regimes, demonstrating the synergetic effects of isoprene and HOx (OH and HO2) on biogenic NPF. Whereas the suppression of NPF by isoprene is due to the product suppression effects of monoterpene dimers (C20), RO2 + HO2 termination reactions also play important roles in suppressing the dimer formation, another likely process to suppress NPF in the atmosphere. Plain Language Summary: Isoprene, emitted mainly from broad‐leaf trees, is the most important volatile organic compound at the global scale. Yet, the role of isoprene in new particle formation (NPF) is still unclear and studies often show contradicting results. In this study, using the state‐of‐the art mass spectrometer analysis, we show how oxidation reactions of isoprene can suppress or enhance biogenic NPF under different oxidation conditions. We believe our results help to reconcile the discrepancies that exist in the previous biogenic NPF studies. Key Points: Isoprene can suppress or enhance biogenic new particle formation (NPF) depending on the oxidation regime (OH vs. ozone oxidation)Biogenic NPF is affected by both biogenic volatile organic compounds (VOCs) composition and HOx conditionsPrevious laboratory studies showed seemingly contradicting theories because of the vastly different VOCs and HOx conditions [ABSTRACT FROM AUTHOR] |
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