Articles | Volume 17, issue 5
Research article
08 Mar 2017
Research article |  | 08 Mar 2017

Terpenoid and carbonyl emissions from Norway spruce in Finland during the growing season

Hannele Hakola, Virpi Tarvainen, Arnaud P. Praplan, Kerneels Jaars, Marja Hemmilä, Markku Kulmala, Jaana Bäck, and Heidi Hellén

Abstract. We present spring and summer volatile organic compound (VOC) emission rate measurements from Norway spruce (Picea abies L. Karst) growing in a boreal forest in southern Finland. The measurements were conducted using in situ gas chromatograph with 1 to 2 h time resolution to reveal quantitative and qualitative short-term and seasonal variability of the emissions. The measurements cover altogether 14 weeks in years 2011, 2014 and 2015. Monoterpene (MT) and sesquiterpene (SQT) emission rates were measured all the time, but isoprene only in 2014 and 2015 and acetone and C4–C10 aldehydes only in 2015. The emission rates of all the compounds were low in spring, but MT, acetone, and C4–C10 aldehyde emission rates increased as summer proceeded, reaching maximum emission rates in July. Late summer mean values (late July and August) were 29, 17, and 33 ng g(dw)−1 h−1 for MTs, acetone, and aldehydes respectively. SQT emission rates increased during the summer and highest emissions were measured in late summer (late summer mean value 84 ng g(dw)−1 h−1) concomitant with highest linalool emissions most likely due to stress effects. The between-tree variability of emission pattern was studied by measuring seven different trees during the same afternoon using adsorbent tubes. Especially the contributions of limonene, terpinolene, and camphene were found to vary between trees, whereas proportions of α-pinene (25 ± 5 %) and β-pinene (7 ± 3 %) were more stable. Our results show that it is important to measure emissions at canopy level due to irregular emission pattern, but reliable SQT emission data can be measured only from enclosures. SQT emissions contributed more than 90 % of the ozone reactivity most of the time, and about 70 % of the OH reactivity during late summer. The contribution of aldehydes to OH reactivity was comparable to that of MT during late summer, 10–30 % most of the time.

Short summary
We present spring and summer VOC emission rate measurements from Norway spruce using an in situ gas chromatograph. Monoterpene and C4–C10 aldehyde emission rates reached maxima in July. SQT emissions increased at the end of July and in August SQT were the most abundant group. The MT emission pattern varied a lot from tree to tree and therefore emission fluxes on canopy level should be conducted for more representative measurements. However, leaf level measurements produce more reliable SQT data.
Final-revised paper