Isoprene and monoterpene emission from the coniferous species Abies Borisii-regis—implications for regional air chemistry in Greece

Abstract

The emission of isoprene has been studied from a forest of Abies Borisii-regis, a Mediterranean fir species previously thought to emit only monoterpenes. Emission studies from two independent enclosure experiments indicated a standardised isoprene emission rate of (18.4±3.8) μg g dry-weight −1 h −1, similar in magnitude to species such as eucalyptus and oak which are considered to be strong isoprene emitters. Isoprene emission depended strongly on both leaf temperature (2°C–34°C) and photosynthetically active radiation (PAR) below 250 μmol m −2 s −1, becoming saturated with respect to PAR above this value. The annual isoprene emission rate was estimated to be (132±29) kT yr −1 for those trees growing within Greece, comparable to current estimates of the total isoprene budget of Greece as a whole, and contributing significantly to regional ozone and carbon monoxide budgets. Monoterpene emission exhibited exponential temperature dependence, with 1,8-cineole, α-pinene, β-pinene and limonene forming the primary emissions. A standardised total monoterpene emission rate of (2.7±1.1) μg g dry-weight −1 h −1 was calculated, corresponding to an annual monoterpene emission rate of (24±12) kT yr −1. Research was conducted as part of the AEROBIC’97 (AEROsol formation from BIogenic organic Carbon) series of field campaigns.