The ambient concentrations of biogenic hydrocarbons at a northern European, boreal site

Concentrations of monoterpenes, 1,8-cineol and light hydrocarbons were meas ured in Potsonvaara, Ilomantsi, Eastern Finland during two growing seasons in 1997 and 1998. The measuring site was located on the top of a hill, outs ide a mixed forest. The monthly average summer concentrations of isoprene w ere 0.3-1.7 ppbC and monoterpenes and 1,8-cineol together 1.6-3.2 ppbC. Iso prene and alpha -pinene were the most abundant compounds throughout the gro wing season, but beta -pinene, Delta (3)-carene, camphene, 1,8-cineol, sabi nene and limonene were Found as well. Isoprene and sabinene concentrations started to increase later than the concentrations of other compounds, and w ere better correlated with each other than with other compounds. Diurnal va riations of monoterpenes show a minimum in the daytime and a maximum at nig ht, except sabinene at midsummer, that has maximum concentrations during th e day. The field data support the idea that the effective temperature sum c an be used to predict the initiation of emissions of isoprene and also terp ene emissions from Betula pendula. (C) 2000 Elsevier Science Ltd. All right s reserved.