OCCURRENCE AND DISTRIBUTION OF POLYCYCLIC AROMATIC-HYDROCARBONS (PAHS) IN AN AGRICULTURAL ECOSYSTEM

The concentration and distribution of PAHs were determined in soil, su rface water, sediments, and groundwater of the experimental farm of th e research network ''Forschungsverbund Agrarokosysteme Munchen'' (FAM) , part of a rural region in Bavaria, Germany. Analytical procedures in clude ultrasonication, solid phase extraction, liquid-liquid extractio n, HPLC and fluorescence detection. Fifteen common PAHs were usually f ound in low concentrations in the examined compartments. The distribut ion of total PAHs in surface soils of 15 sampling sites in the area wa s not uniform. It could be demonstrated that there were high concentra tions in valleys and low concentrations on top of the hills, due to lo ng-term transport of PAHs to the valleys by surface run-off. Subsurfac e soil was found to contain lower amounts. Tetra-to hexacyclic PAHs sh owed similar profiles in the subsurface soil and in the top soil, whil e profiles of bi-and tricyclic PAHs deviated significantly. Additional ly, tetra-to hexacyclic PAHs were enriched in distinct zones in the su bsurface soil and exhibited similar patterns in groundwater and aquife r material. These results indicate a transport of bi- and tricyclic PA Hs mainly in the dissolved or gaseous state and a predominant particle -associated transport of tetra-to hexacyclic PAHs. This particle-bound transport increases the migration velocity of hydrophobic pollutants through the vadose zone and enhances the mobility in groundwater.