Sesquiterpenes and oxygenated sesquiterpenes dominate the VOC (C5–C20) emissions of downy birches
| Autor: | Arnaud P. Praplan, Pauliina Schiestl-Aalto, Heidi Hellén, Simon Schallhart, Aku Helin, Hannele Hakola, Toni Tykkä, Jaana Bäck |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
0106 biological sciences
Atmospheric Science 010504 meteorology & atmospheric sciences biology Farnesene Chemistry Monoterpene Caryophyllene Green leaf volatiles Growing season Betula pubescens 15. Life on land biology.organism_classification 01 natural sciences Terpene chemistry.chemical_compound 13. Climate action Environmental chemistry Isoprene 010606 plant biology & botany 0105 earth and related environmental sciences |
| Zdroj: | Atmospheric Chemistry and Physics. 21:8045-8066 |
| ISSN: | 1680-7324 |
| Popis: | Biogenic volatile organic compounds (BVOCs) emitted by the forests are known to have strong impacts in the atmosphere. However, lots of missing reactivity is found, especially in the forest air. Therefore better characterization of sources and identification/quantification of unknown reactive compounds is needed. While isoprene and monoterpene (MT) emissions of boreal needle trees have been studied quite intensively, there is much less knowledge on the emissions of boreal deciduous trees and emissions of larger terpenes and oxygenated volatile organic compounds (OVOCs). Here we quantified the downy birch (Betula pubescens) leaf emissions of terpenes, oxygenated terpenes and green leaf volatiles (GLVs) at the SMEAR II boreal forest site using in situ gas chromatographs with mass spectrometers. Sesquiterpenes (SQTs) and oxygenated sesquiterpenes (OSQTs) were the main emitted compounds. Mean emission rates of SQTs and OSQTs were significantly higher in the early growing season (510 and 650 ng g dw - 1 h −1 , respectively) compared to in the main (40 and 130 ng g dw - 1 h −1 , respectively) and late (14 and 46 ng g dw - 1 h −1 , respectively) periods, indicating that early leaf growth is a strong source of these compounds. The emissions had a very clear diurnal variation with afternoon maxima being on average 4 to 8 times higher than seasonal means for SQTs and OSQTs, respectively. β -Caryophyllene and β -farnesene were the main SQTs emitted. The main emitted OSQTs were tentatively identified as 14-hydroxy- β -caryophyllene acetate ( M=262 g mol −1 ) and 6-hydroxy- β -caryophyllene ( M=220 g mol −1 ). Over the whole growing season, the total MT emissions were only 24 % and 17 % of the total SQT and OSQT emissions, respectively. A stressed tree growing in a pot was also studied, and high emissions of α -farnesene and an unidentified SQT were detected together with high emissions of GLVs. Due to the relatively low volatility and the high reactivity of SQTs and OSQTs, downy birch emissions are expected to have strong impacts on atmospheric chemistry, especially on secondary organic aerosol (SOA) production. |
| Databáze: | OpenAIRE |
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