Bioformation of polycyclic aromatic hydrocarbons in soil under oxygen deficient conditions

Possible formation of polycyclic aromatic hydrocarbons (PAHs) through biological processes in soil was investigated. Soil, plant material, and a mixture of both were waterlogged and incubated for 2 years, resulting in Iona lasting oxygen deficient conditions. Sample extracts were analysed by HPLC for 15 PAHs. In soil with or without added plant material, the contents of 4-, 5-, and 6-ring PAHs increased significantly to 139-238% of the contents before incubation. Concentrations decreased for several 3-ring PAHs, probably due to anaerobic biodegradation. When only plant material was incubated, the increase was significant for the 4-ring PAHs benzo[a]anthracene and chrysene and all 5- and 6-ring PAHs (250-674%). It was assumed that PAHs are formed from aromatic compounds of plant material and humus precursors. Under oxygen deficient conditions this may lead to natural background levels of PAHs in soils. (C) 2002 Elsevier Science Ltd. All rights reserved.