Uso di agenti mobilizzanti nel micorisanamento di suoli sottoposti a contaminazione recente e storicamente contaminati da idrocarburi policiclici aromatici
Author(s)
Leonardi, Vanessa
Date Issued
November 5, 2008
Type
Doctoral Thesis
Abstract
Bioavailability of pollutants in contaminated soils represents an important factor governing the efficacy of a bioremediation process. The present study was aimed at comparatively assessing the impact of several mobilizing agents, (MA, i.e. Tween 20, Tween 80, soybean oil, olive-mill wastewater and randomly methylated cyclodextrines) on the degradation performances of the fungi Irpex lacteus (FR.:FR.) FR., 617/93, Pleurotus ostreatus (JACQ.:FR.) KUMM., 300, Allescheriella sp. DABAC 2B e Phlebia sp. (DABAC 9) in a soil spiked with a mixture of polyaromatic hydrocarbons (PAHs), in order to simulate a recent contamination. Soybean oil, added to the soil at the rate of 2,5% (w/w) led to a significant increase in the depletion levels of high molecular weight PAHs. Among the fungi investigated, P. ostreatus and I. lacteus showed the best degradative performances and the degradation capability of both species took significant advantages from the presence of the mobilizing agents.
For this reason, these two strains were selected for further studies conducted on an artificially spiked soil with PAHs that underwent an ageing process. These tests confirmed the positive impact of soybean oil on the decontamination levels exerted by both fungi. Subsequently, the degradation performances of the same strains were investigated in two historically contaminated soils. These soils differed each one another in both overall PAHs concentrations (2320 vs. 612 mg PAHs kg-1) and in the relative amount of the non-bioavailable fraction (4,0 vs. 32%, respectively). The addition of MAs to the soil with a negligible amount of the non-bioavailable fraction, had a limited impact on PAH degradation. By contrast, in the other soil, characterized by a larger non-bioavailable fraction, the addition of soybean oil significantly enhanced the degradation performances of both fungi. The stimulatory effect of this MA was evident in particular for the least bioavailable compounds, such as benzo[a]pyrene, dibenzo[a,h]anthracene, benzo[g,h,i]perylene and indeno[1,2,3-cd]pyrene.
This study suggests that mobilizing agents might exert a positive impact on mycoremediation of PAH-contaminated soils but a preventive study is required to establish proper fungus/MA combinations. In addition, a preliminary determination of the relative amount of the non-bioavailable fraction might of great help in both predicting bioremediation performances and in order to evaluate the technical opportunity of adding MAs.
Additional information
Dottorato di ricerca in Scienze ambientali
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