Monoterpene emissions from Beech (Fagus sylvatica) in a French forest and impact on secondary pollutants formation at regional scale

Biogenic emissions from forest, crops, and grasslands are now considered major compounds in photochemical processes. Air quality analyses require more and more accurate input data, particularly emissions. Unfortunately, depending on the type of vegetation, these emissions are not always reliably defined. For example, Fagus sylvatica, which is a very abundant deciduous tree in France and in Europe, is a weak monoterpene emitter in the European inventory developed by Simpson et al. [1999. Journal of Geophysical Research 104, 8113–8152], but is a strong monoterpene emitter in Luchetta [1999. Caractérisation et quantification dans la basse atmosphère de composés organiques volatils biogéniques et anthropiques contribuant à la pollution de l’air. Ph.D. thesis, INPT Toulouse]. Beech (F. sylvatica) emission potential has never been measured in France.This study investigates the isoprene and monoterpenes emission measurements from F. sylvatica   in France during a research program INTERREG III in Fossé Rhénan, during May and June 2003. A dynamic cuvette method was used. Sabinene is the main monoterpene emitted, composing more than 90% of biogenic emissions. The remaining is composed of αα-pinene, ββ-pinene and limonene. No isoprene emissions were detected. The monoterpene emissions from F. sylvatica are affected by temperature and photosynthetic active radiation (PAR). In order to describe monoterpene emissions, the “isoprene algorithm” developed by Guenther et al. [1991. Journal of Geophysical Research 26A, 10799–10808; 1993. Journal of Geophysical Research 98D, 12609–12617] has been used. With this algorithm, simulation results and observations agree fairly well.The standard emission rate (T=303K and PAR=1000 μmol m−2 s−1) for total monoterpenes is 43.5 μg gdw−1 h−1. This classifies F. sylvatica as a strong monoterpene emitter.The European inventory [Simpson, et al., 1999. Journal of Geophysical Research 104, 8113–8152], which is the standard inventory of the model CHIMERE, is adjusted using this value. This induces an annual increase of 30% in simulated monoterpene emissions in France.These two inventories are used to simulate a regional pollution event during spring 2003. No significant differences are observed for ozone concentrations. Peroxy Acyl Nitrate (PANs) and formaldehyde concentrations increase by up to 10% in the adjusted inventory.