MEASURING AIRBORNE TRACE ORGANIC-COMPOUNDS - COMPARISON OF DIFFERENT METHODS TO DETERMINE VAPOR PARTICLE RATIOS

Artifact formation during the sampling of atmospheric vapor and partic les was investigated for polycyclic aromatic hydrocarbons (PAHs) and o rganochlorines (OCLs). Three different systems of particle separation were operated in parallel: an electrostatic precipitator (ESP), an imp actor and a glass fibre filter (GFF), each followed by an adsorbent tr ap. Secondary reactions of PAHs and some OCLs in the ESP were observed , disqualifying this method. Both the impactor and GFF results showed that chlorobenzenes, pentachloroanisol and HCH were present almost exc lusively (greater-than-or-equal-to 99 %) in the vapor phase. The vapor /particle ratios of the PAHs, with the exception of benzo(a)pyrene, we re consistent for both systems, whereas DDT, DDE and some PCBs showed lower particle-bound amounts in the GFF/adsorbent system. This could b e due to temperature mediated desorption of OCLs from the particles se parated on GFFs. We believe that particles collected in the impactor a re better protected from desorption due to their aggregation to cones of high density and comparatively small surface. The comparison shows that, in most cases, artifact formation in GFF/adsorbent systems is no t as significant as has been hypothetisized in the literature.