Measurement of volatile organic compound (VOC) concentration profiles in the atmosphere of a remote forest region

The immission situation for volatile organic compounds (VOCs) in an alpine forest area at Achenkirch, Tyrol, was assessed by carrying out sampling cam paigns with parallel sampling at the three sampling sites at 1030, 1220 and 1686 m a.s.l., respectively. More than 80 different non-methane hydrocarbo n compounds were identified and quantitatively determined. It was thus poss ible to record temporal and altitude profiles of the individual VOCs which allows first to make a source discrimination between the different compound s and second an assessment of their relevance for the photochemical ozone f ormation in the troposphere. These data is used to assess the potential thr eat of the alpine forest vegetation due to direct (toxic) or indirect effec ts las ozone precursors) by VOCs. Results are presented for the sampling ca mpaign of the 14.06.1996 that illustrate the extraction of information from and the interpretation of the observed VOC mixing ratio patterns. The VOC mixing ratios are comparatively low on a daily average at the two higher lo cated sampling stations (14 and 16 ppbC, respectively), but significantly h igher in the valley (40 ppbC daily average and 71 ppbC peak concentration). Ethene is the most abundant single compound. Although no emission source c ould be identified explicitly, it is very probable that these high peak con centrations are due to long range transport from stronger polluted areas in South Germany as can be deduced from the specific VOC pattern.