Abstract
The study investigated the degradation of the polycyclic aromatic hydrocarbons (PAH) benzo(a)anthracene, benzo(a) fluoranthene, benzo(a) pyrene, chrysene and phenanthrene in a soil that was sterilized and inoculated with the nonligninolytic fungi, Fusarium flocciferum and Trichoderma spp. and the ligninolytic fungi,Trametes versicolor and Pleurotus ostreatus in the presence of cadmium (Cd) and nickel (Ni) during a ten week incubation period. The soil pH was initially 5.3 and after amendment increased to 7.0. The fungi degraded the tested PAHs between 21 and 93% by the end of the tenth week. The fungi degraded the less-soluble PAHs containing five or six aromatic rings more slowly than those containing fewer aromatic rings. Although the presence of cadmium and nickel in the soil affected the activity of the enzymes produced by the fungi, no significant decrease in PAH degradation was found in the contaminated soil containing 50 or 100 mg kg-1 of Cd and Ni. However, at 300 and 500 mg kg-1, degradation of the PAHs by the fungi was impaired and the severity of the impairments increased with the increase in the concentrations of Cd and Ni. This was probably due to the lack of the activities of some enzymes such as Mn-dependent peroxidase, which could have resulted from the poor colonization of the fungi at these concentrations. Key words: Bioremediation, fungi, heavy metals, PAHs, soil.
Highlights
Polycyclic aromatic hydrocarbons (PAHs), produced by incomplete combustion of fossil fuels, and manufactured for use in the pesticide, pharmaceutical and dyemaking industry are ubiquitous and persistent in the environment (Mueller et al, 1996; Clemente et al, 2001; Garon et al, 2004)
The aim of this study was to investigate the effects of the heavy metals cadmium (Cd) and nickel (Ni) on the biodegradation of selected PAHs by non-ligninolytic and ligninolytic fungi
The soil was amended with 7 g kg-1 of agricultural lime and 1g kg-1 mono ammonium phosphate (MAP) fertilizer before being amended with 250 mg kg-1 phenanthrene, 150 mg kg-1 chrysene, 220 mg kg-1 benzo(a)anthracene, 200 mg kg-1 benzo(a)pyrene and 100 mg kg-1 benzo(a)fluoranthene
Summary
Polycyclic aromatic hydrocarbons (PAHs), produced by incomplete combustion of fossil fuels, and manufactured for use in the pesticide, pharmaceutical and dyemaking industry are ubiquitous and persistent in the environment (Mueller et al, 1996; Clemente et al, 2001; Garon et al, 2004). They are hydrophobic and can readily bio-accumulate in the environment. The number of benzene rings present in the structure of a PAH affects its physical and chemical properties such as solubility, which is very important for bioavailability. The larger the number of rings, the more recalcitrant the compound becomes
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