Biogenic VOCs in continental Northern Europe - Concentrations and photochemistry

This work is part of the project Biogenic VOC Emissions and Photochemistry in the Boreal regions of Europe (BIPHOREP). A short overview is first given of the project activities. This paper specifically deals with ambient air VOC and ozone concentrations. Both biogenic emissions and photochemical pro cesses have strong seasonal cycles. The emission of biogenic VOCs (isoprene and terpenes) takes place mainly between May and October. Average ozone co ncentrations have a spring maximum and, in the northern parts of the boreal region, a minimum in late summer. Photochemical ozone production takes pla ce in March-October. Elevated ozone concentrations are observed in spring a nd summer in connection with favourable meteorological situations. Analysis of ozone and total nitrate concentrations together with a factor analysis of C2-C6 VOC concentrations show that the concentrations of anthropogenic c ompounds are elevated when ozone concentrations are above the background le vel. However, also the compounds with biogenic origin show higher concentra tions then, because elevated ozone concentrations are connected with warm c ontinental air masses. Factor analysis suggests that l-butene, propane and ethene have also biogenic sources. (C) 1999 Elsevier Science Ltd. All right s reserved.