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

Abstract

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 C 4 -C 10 aldehydes only in 2015. The emission rates of all the compounds were low in spring, but MT, acetone, and C 4 -C 10 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.

Sesquiterpenes identified as key species for atmospheric chemistry in boreal forest by terpenoid and OVOC measurements

“…Temperature sensitivity of SQTs was even higher than for MTs. SQT emissions from Norway spruce (Hakola et al, 2017) and Scots pine (Tarvainen et al, 2005) (Duhl et al 2008). Especially daily mean β-caryophyllene concentrations had very high exponential correlation with temperature (R 2 Jun-Aug=0.96) supporting only temperature dependent emissions.…”

“…The reaction rate coefficients for OH reactions are the same as used by Praplan et al (2018), for O3 reactions by Hakola et al (2017) Since hydroxyl radical concentrations were not measured directly, proxies were calculated from UVB radiation intensity, which is known to correlate strongly with OH radicals as described by Petäjä et al (2009). NO3 concentrations were calculated 15 by assuming steady-state by its production from O3 and NO2 and removal by photolysis and oxidation reactions as decribed by Peräkylä et al (2014).…”

“…Laboratory studies have shown stress related emissions of β-farnesene (Blande et al 2009, Petterson 2007, and it has been detected as well in 10 local spruce emissions by Hakola et al (2017).…”

“…nonanal can be produced when ozone attacks the fatty acids on leaf or needle surfaces (Bowman et al, 2003). Hakola et al (2017) measured also C4-C10 aldehyde emissions from Norway spruce and found out that they were about the same magnitude as MT emissions during late summer.…”

“…in spruce emissions (Hakola et al 2017), but it has also anthropogenic sources . Linalool is known to be emitted by trees as a result of biotic stress (Petterson, 2007, Blande et al 2009 …”