چكيده به لاتين
Polycyclic aromatic hydrocarbons (PAHs) including phenanthrene, are among the most important environmental contamination factors that due to the complexity of the process in the solid phase of soil, they are often investigated in the slurry phase. Among the methods of soil remediation, biological treatment with white rot fungi is one of the most effective methods. White rot fungi have been applied for the clean up of pollutants depending on a group of extracellular ligninolytic enzymes secreted by them. In this research, four selected fungi of indigenous species of Iran, which were able to degrade phenanthrene as the only source of carbon in the liquid medium, entered the soil test. For this purpose, the soil was contaminated at three different concentrations of 100, 200 and 300ppm of phenanthrene and the biological removal rate was investigated by four different fungi within five weeks in the Erlen scale. By increasing the pollutant concentration, the percentage of removal was not reduced and the highest percentage of decomposition for two species of fungi was obtained at the highest concentration of phenanthrene and neutral pH. The two species were able to remove about 70% of phenanthrene in a concentration of 300ppm over a period of 21 days. Finally, the selected microorganisms were immobilized on rice hulls and sawdust as a cosubstrates (with substrate ratios of 1:10 and 1:30) entered to test tube assuming an increase in the height relative to the diameter of the soil and solving problems such as failure of the hyphae due to mixing during sampling and setting of moisture and the ratio of soil C/N. At the end of the 40-day period, the fungi named 4 which immobilized on rice hulls was able to remove 89.16% of the pollutant and obtain the best result. In general, the ratio of substrate to the soil 1:10 was more efficient than 1:30 in the long run. In the ratio of 1:10 fungi used rice hulls and sawdust as a source of energy and then begin to remove phenanthrene (a 3-ring pollutant which its structure is similar to lignin). Considering the significant amount of phenantherene removal efficiency without forced aeration and not losing enzymatic ability of microorganisms in the short term of the removal process, it seems that these indigenous species have a high potential for biodegradation of phenanthrene and other polycyclic aromatic hydrocarbons in higher concentrations in the soild phase.
Keywords: Polycyclic aromatic hydrocarbons, bioremediation, phenanthrene, solid phase, white rot fungi
