Analysis of organic trace compounds in the atmosphere and the correlation between meteorological situation and concentration of reference substances

A research project is described, which is being carried out systematically with the objective of qualitative and quantitative assessment of organic substances occurring in the air at forest sites considering seasonal and meteorological variations. To begin with, a collecting and analytical system with diverse additional modules had to be developed and assembled for this purpose. With the aid of an adsorptive enrichment system this enables the determination of the entire palette of organic substances present in the air at the site.Hitherto, about 160 of the major organic substances occurring in the air at the site have been determined. These occur at concentrations between several ng to several g per m³ air and belong to different classes of compounds. So-called reference substances have been selected as representatives of particular classes of substances. The alterations of concentrations in air at the site of these reference substances have been investigated as a function of meteorological conditions. The evaluation of the data led to the following conclusions:

–	The influence of wind direction, i.e. the long-distance transport of emission, is particularly significant with respect to presence and concentration of organic substances in air at the site.
–	The humidity prevailing during sampling at the site has a significant influence on the concentration of airborne organic compounds of natural origin, e. g. acetophenone.
–	There are indications that the wind velocity also plays a significant role on the concentration of organic substances in air at the site during uniform wind direction.