PAK-Abnahmen in Bodenproben verschiedener Altlaststandorte bei Aktivierung der autochthonen Mikroflora

PAH decrease in soil samples from different polluted industrial sites by activating the autochthonous microflora In pot experiments under field conditions the PAH decrease in ten different soil samples from former industrial sites with differing PAH load were investigated over a period of 74 and 168 weeks. 15 out of 16 PAH according to US EPA (without acenaphthylene) were determined. Easily degradable organic matter, mineral fertilizers, synthetic surfactants and in some experiments also lime were added to the soil samples in varying amounts. Depending on the nature and quantity of the amendments, the biological activity and (co-)metabolic decomposition of PAH by soil microorganisms could considerably be increased. In the different soil samples a decrease of the initial PAH contents between 12 and 90% was achieved within 74 weeks. Even from 74 up to 168 weeks for some soil samples a remarkable further decrease of the PAH contents could be observed. The decrease of the extractable PAH with time is mainly caused by microbial decomposition and formation of nonextractable residues. This behavior can be fitted by two coupled exponential functions, one for an initial phase of rapid decomposition and the other for a subsequent phase of slow decomposition. Therefore, two different processes (I, II) determine the decrease of PAH. In the first week of the experiment the decomposition rates for process I amount to 4.2–88.3 and for process II to 0.06–5.3 mg PAH ? kg^?1 soil ? week^?1; in the 168th week they are no longer determinable for process I and amount to 0.05–2.3 mg ? kg^?1 ? week' for process II. Higher initial PAH contents often led to higher relative PAH decreases, but also to absolute higher contents of residues. The persistence of PAH is mainly determined by their bioavailability. PAH degradation is increased by the soil treatments. The addition of easily degradable organic matter (C/N ratio < 20) in a quantity of 30g ? kg^?1 (w/w) combined with the addition of nitrate and a surfactant most effectively increased the degradation of PAH. Raising the pH of a very strongly acidic soil sample revealed a maximum PAH decomposition at a pH of 6.