THE DETERMINATION OF TERPENES IN FOREST AIR

Monoterpene emissions are an important source of hydrocarbons in the a tmosphere. An analytical method was developed and validated to determi ne the monoterpene concentrations at different heights above the canop y of a forest. The method focused on alpha- and beta-pinene, 3-carene and limonene. The detection limits for these compounds were ca. 0.05 n g and the repeatability ca. 5% (with the exception of limonene which s howed a repeatability of ca. 15%). The breakthroug volumes for all fou r terpenes were > 3 l. The presence of realistic concentrations of O3, NO2 and H2O during sampling resulted in a decrease of 10-50% of the a mounts of recovered terpenes. The method was used in a pilot experimen t to determine the concentrations of the monoterpenes at different hei ghts above a pine forest. The concentrations of the measured terpenes varied from < 0.05 to 1.6 ng l-1, with alpha- and beta-pinene being th e most prominent. A concentration gradient could be determined for alp ha- and beta-pinene and 3-carene.