PERFLUOROCARBON BACKGROUND CONCENTRATIONS IN EUROPE

Five studies of the background level of several perfluorocarbon compou nds in Europe are here presented together with measurements from the E uropean Tracer Experiment (ETEX). The tracers used during the two ETEX tracer releases were the perfluorocarbons (PFCs); perfluoromethylcycl ohexane (C7F14, PMCH) and perfluoromethylcyclopentane (C6F12, PMCP). T heir background concentrations were detected by using both passive and active sampling techniques, to define the spatial and temporal variat ion of the PFCs over Europe. Also the background Variations of four is omers of the PFC compound perfluorodimethylcyclohexane (C8F16, PDCH) w ere studied. The results were compared to other PFC tracer studies in the U.S.A. and Europe. The mean and median values of the measured PFCs were found to vary slightly and randomly in space and time. They were found to be higher and to have a larger standard deviation than the m easurements from the American studies. The background concentrations w ere still found to be low and stable enough for PFCs to be highly suit able for use in tracer studies. The following concentrations were foun d: PMCP; 4.6 +/- 0.3 fl l(-1), PMCH: 4.6 +/- 0.8 fl l(-1), ocPDCH: 0.9 6 +/- 0.33 fl l(-1), mtPDCH: 9.3 +/- 0.8 fl l(-1), mcPDCH: 8.8 +/- 0.8 fl l(-1), ptPDCH: 6.1 +/- 0.8 fl l(-1). A study of the correlation be tween the measured PFC compounds showed a significant correlation betw een most of the compounds, which indicate that there are no major PFC sources in Europe. (C) 1998 Elsevier Science Ltd. All rights reserved.