Problems connected with the analysis of halocarbons and hydrocarbons in the non-urban atmosphere.

The problems connected with the measurement of hydrocarbons outside urban areas are considerable: The atmospheric mixing ratios of most of the hydrocarbons are very low--from a few ppb down to some ppt; the mixture of hydrocarbons is extremely complex, ranging from light n-alkanes to alkyl benzenes and terpenes; for measurements in remote areas the logistic conditions often restrict the instrumentation which can be used for sample collection or in situ measurements (such as lack of electric power supply, weight restrictions etc.). Nevertheless, sensitive and sufficiently reliable measurements of hydrocarbons in the non-urban atmosphere are important. Hydrocarbons are important factors in the tropospheric photochemistry (e.g. ozone formation) and can be used as valuable tracers for man-made atmospheric pollutants etc. Other useful tracers for anthropogenic emission are halocarbons such as dichlormethane, tri- and tetrachloroethen etc. The impact of man-made hydrocarbons on the chemistry of the troposphere can only be understood if the extent of natural (biogenic) contributions is known. From measurements of a large variety of hydrocarbons and halocarbons it is often possible to obtain information about the sources of the most important atmospheric hydrocarbon species, even for trace gases with both significant anthropogenic and biogenic sources. In this presentation some of the problems and their solutions connected with such measurements of atmospheric hydrocarbons and halocarbons are presented and discussed. Some of the results obtained by several series of measurements are described, indicating that man-made as well as biogenic hydrocarbons can be important factors for the chemistry of the atmosphere.