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Soils that are contaminated with the most recalcitrant organic contaminants, such as high molecular weight polyaromatic hydrocarbons (HMW PAH) and polychlorinated dibenzo-pdioxins and dibenzofurans (PCDD/F), cannot be degraded efficiently by conventional composting. The only available treatment method for these soils, which destroys the contaminants, is combustion at high temperature. This thesis examines three alternative fungal methods to treat these soils: 1) treatment with fungal enzymes, 2) treatment with fungal inoculum, and 3) fungal treatment used as a pre-treatment to improve the energy efficacy in combustion. Manganese peroxidase (MnP), which belongs to lignin-modifying enzymes (LME), was produced and used to treat PCDD/F-contaminated soil in the laboratory scale. Nevertheless, no degradation with a MnP preparation was observed, although a substantial amount of MnP activity was found in the soil still after 10 days of incubation. Both PAH-and PCDD/Fcontaminated soils were treated with fungal inoculum in the laboratory scale. HMW PAHs were degraded significantly more by the fungi than by the indigenous microbes alone in the laboratory experiments, where the PAH concentration of soil was 3500 mg kg -1 (sum of 16 PAH). Treatment with Phanerochaete velutina (inoculum) resulted to degradation of 96 % of 4-ring PAHs and 39 % of 5-and 6-ring PAHs in three months. With PCDD/F-contaminated soil, no degradation was observed in the control, but the degradation of PCDD/Fs with fungal treatments was significant (P. velutina: 62 %, Stropharia rugosoannulata: 64 % of WHO-TEQ value). Fungal treatment of PAH-contaminated soil was also applied in the field scale (2 t). However, both P. velutina (inoculum) and control treatment resulted in equal degradation in soil with lower PAH concentration (1400 mg kg -1 , sum of 16 PAH): 94 % of the 16 PAHs were degraded in three months. Fungal treatment was even applied as a pre-treatment for contaminated soil with high organic matter content, and which will be later combusted. In the pilot-scale (300 kg), 13 % degradation of the original organic matter content was obtained in 6 months. To conclude, fungal treatment is reasonable to apply for soils with organic contaminants that cannot be bioremediated by composting. With soils contaminated by chlorinated dioxins, this is always the case, but also PAH-contaminated soils with high total concentration or high proportion of HMW-PAHs. In addition, with fungal treatment the amount of organic matter in the soil can be reduced and the efficacy of the combustion process is improved. Tiivistelmä Kaikkein vaikeimmin hajoavilla orgaanisilla yhdisteillä kuten monirenkaisilla polyaromaattisilla hiilivedyillä (PAH) sekä polyklooratuilla dibenzo-p-dioksiineilla ja -furaaneilla (PCDD/F) pilaantuneita maita ei pystytä tehokkaasti kunnostamaan perinteisellä kompostoinnilla. Ainoa käytössä oleva puhdistusmenetelmä, joka hajottaa pilaavat yhdisteet, on maan poltto korkeassa lämpötilassa. Tämä väitöskirja esittelee kolme vaihtoehtoista valkolah...

The use of biochar (BC) has been suggested for remediation of contaminated soils. This study aims to investigate the role of microorganisms in sorption of PAH to BC-amended soils. Fungi, especially the wood and litter-degrading fungi, have shown the ability for humification and to degrade recalcitrant molecules, and are thus suitable model organisms. Haplic Arenosol with high organic matter content was chosen to highlight the importance of soil organic matter (SOM) in PAH sorption, possibly to form non-extractable residue. Basidiomycetous fungi Agrocybe praecox and Phanerochaete velutina grown on pine bark were inoculated in organic matter (OM) rich Haplic Arenosol and OM poor sandy loam with either BC or chemically activated BC (ABC) and 14 C-labelled pyrene for 60 days. Fungi did not mineralize pyrene, but increased sorption up to 47-56% in BC-amended Haplic Arenosol in comparison with controls (13-25%) without a fungus irrespective of the presence of an adsorbent. In OM poor sandy loam only 9-12% of pyrene was sorbed to amended soil in the presence of fungus and adsorbent. Combining BC and fungi is an effective method for sorbing pyrene especially in high SOM soils.