The formation of PAH oxidation products in soils and soil/compost mixtures

The degradation of coal tar polycyclic aromatic hydrocarbons (PAHs) including N-containing analogues (N-PAHs) was investigated in three soil systems which had been artificially contaminated. Studies were carried out with soil material from an AhAl horizon fortified with a) a coal tar oil, formerly used as a wood-preservative, or with b) a PAH/N-PAH mixture consisting of 18 compounds and with c) a soil/compost mixture fortified with the PAH/N-PAH mixture. Whereas in unamended soil only aromatics with up to three fused benzene rings were considerably degraded during the first 15 weeks experimental time, soil supplementation with compost helped to enhance elimination of all compounds monitored. Substantial residues after 15 weeks were only found for benz[a]anthracene, chrysene, and benzo[a]pyrene, with 11, 19, and 54% respectively. Accumulation of ketonic and quinonic degradation products such as 9-fluorenone, anthracene-9,10-dione, 2-methylanthracene-9,10-dione, and benz[a]anthracene-7,12-dione was observed in unamended soil material. In mixtures with compost, short-term concentration maxima of such products correlated well with phases of enhanced contaminant elimination.