VOC measurements within a boreal forest during spring 2005: on the occurrence of elevated monoterpene concentrations during night time intense particle concentration events

Abstract

Abstract. In this study we present measurements of selected trace gases and aerosols made in a boreal forest during the BACCI-QUEST IV intensive field campaign in Hyytiälä, Finland in April 2005. Springtime diel and vertical variations of VOCs are discussed in connection with the variations in other trace gases and with the prevailing meteorological conditions. A daytime and a nighttime event have been analysed in detail. The nighttime particle event occurred synchronously with huge increases in monoterpenes, while the second event type involved nucleation and was anti-correlated with sulphuric acid. Here we discuss the possible origins of these two distinct forms of aerosol production at the Hyytiälä site using the measurement data, air mass back trajectories and the optical stereoisomery of monoterpenes. Optical stereoisomery is used in source identification to distinguish between unnatural and natural monoterpene emissions.

Organic Constituents on the Surfaces of Aerosol Particles from Southern Finland, Amazonia, and California Studied by Vibrational Sum Frequency Generation

“…Figure 7B shows that psp-polarized SFG spectra of particles collected in the PM1 size fraction during the early spring at the same field site yield little to no signal above the noise. Work by Eerdekens et al 186 shows generally smaller monoterpene concentrations in the 0.06−0.18 ppbv during the colder period of their early April 2005 study than in this present work (Table 1). A similar study by Liao et al 187 carried out during several periods including early March 2007 shows monoterpene concentrations between 0.01 and 0.1 ppbv, with episodic (hourlong) concentration spikes rising as high as 1 to 2 ppbv.…”

Direct measurement of NO<sub>3</sub> reactivity in a boreal forest

“…High mixing ratios of terpenoids in airmasses that have passed over the sawmill have been documented frequently (Eerdekens et al, 2009;Sinha et al, 2010;Hakola et al, 2012;Nölscher et al, 2012 on the 14 th of September from 06:30 to 08:00 UTC, HYSPLIT back-trajectories (GDAS global, 0.5°), indicating that the air mass passed over Korkeakoski ≈ 0.5 hours prior to reaching the SMEAR II site.…”

“…The NO 3 gradient is the result of lower production rates close to the ground, where O 3 levels are depleted due to deposition and also lower loss rates aloft as the concentration of 5 reactive traces gases from ground level emissions decreases with altitude. High resolution data (Brown et al, 2007b) indicate that the largest gradient in NO 3 concentration is often found in the lowermost 50 m. Night-time monoterpene mixing ratios in forested, boreal regions have been found to display a vertical gradient, with highest mixing ratios at lower levels (Holzinger et al, 2005;Rinne et al, 2005;Eerdekens et al, 2009). This is a result of direct emissions of e.g.…”

“…Air masses from the northern sector were generally associated with lower reactivity (<0.2 s -1 ) whereas all incidents of reactivity larger than 0.3 s -1 were associated with air masses from the SE sector. Enhanced reactivity from the SE may be caused by emissions from the sawmill at Korkeakoski (Eerdekens et al, 2009), or a local wood-shed storing freshly cut timber about 100 m distant from the containers.…”

“…Recent estimates (Guenther et al, 2012) suggest that about 1000 Tg of biogenic volatile organic compounds (BVOC), are emitted annually by vegetation. The boreal forest covers an area of ≈ 15 million km 2 worldwide, which is of comparable size to that of the tropical rainforest (Eerdekens et al, 2009). Forests emit large amounts of unsaturated hydrocarbons in the form of the terpenoids such as, isoprene (2-methylbuta-1,3-diene, C 5 H 8 ), monoterpenes (C 10 H 16 ) and sesquiterpenes (C 15 H 24 ) that have a 5 significant impact on HOx (HO + HO 2 ) and NO X (NO+NO 2 ) budgets (Hakola et al, 2003;Tarvainen et al, 2005;Holzke et al, 2006;Lappalainen et al, 2009) and formation of secondary organic particle (Hallquist et al, 2009).…”