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

Concentrations of monoterpenes, 1,8-cineol and light hydrocarbons were measured in Pötsönvaara, Ilomantsi, Eastern Finland during two growing seasons in 1997 and 1998. The measuring site was located on the top of a hill, outside a mixed forest. The monthly average summer concentrations of isoprene were 0.3–1.7 ppbC and monoterpenes and 1,8-cineol together 1.6–3.2 ppbC. Isoprene and α-pinene were the most abundant compounds throughout the growing season, but β-pinene, Δ3-carene, camphene, 1,8-cineol, sabinene and limonene were found as well. Isoprene and sabinene concentrations started to increase later than the concentrations of other compounds, and were better correlated with each other than with other compounds. Diurnal variations of monoterpenes show a minimum in the daytime and a maximum at night, except sabinene at midsummer, that has maximum concentrations during the day. The field data support the idea that the effective temperature sum can be used to predict the initiation of emissions of isoprene and also terpene emissions from Betula pendula.