BIODEGRADATION OF PAHS IN LONG-TERM CONTAMINATED SOIL CULTIVATED WITH EUROPEAN WHITE BIRCH (BETULA PENDULA) AND RED MULBERRY (MORUS RUBRA) TREE

The ability of birch (Betula pendula) and mulberry (Morus rubra), cultivated either separately or together with perennial ryegrass (Lolium perenne), to enhance the biodegradation of 15 selected polycyclic aromatic hydrocarbons (PAHs) in long-term contaminated soil was studied in a greenhouse experiment. The microecosystems (MESs) were cultivated for either 12 or 18 months at a natural photoperiod. The fact that the soil chosen for cultivation had been contaminated for over 50 years was expected to be the main factor limiting biodegradation. Extracts of both planted and unplanted soil were analyzed using HPLC. After 1 year of cultivation, the overall content of the investigated compounds had declined to 50%. The concentrations of fluoranthene and pyrene, the PAHs originally present in the soil in the highest concentrations (103.5 and 83.3 mg/kg, respectively), had decreased to 28.0 and 18.0 mg/kg, respectively. In addition, other compounds were successfully degraded, including even benzo[a]pyrene. Benzo[ghi]perylene and indeno[1,2,3-cd]pyrene were the only PAHs remaining and were almost entirely undegraded. Because few significant differences were found between the various types of MESs studied, degradation can primarily be attributed to the presence of degrading microorganisms in the soil.