Effect of copper on the degradation of phenanthrene by soil micro-organisms

Aims: The effect of copper on the degradation by soil micro-organisms of ph enanthrene, a polycyclic aromatic hydrocarbon, was investigated. Methods and Results: Inert nylon filters were incubated in the soil for 28 days at 25 degreesC. Each filter was inoculated with a soil suspension, phe nanthrene (400 ppm), copper (0, 70, 700 or 7000 ppm) and nitrogen/phosphoru s sources. The filters were assessed for phenanthrene degradation, microbia l respiration and colonization. Phenanthrene degradation proceeded even at toxic copper levels (700/7000 ppm), indicating the presence of phenanthrene -degrading, copper-resistant and/or -tolerant microbes. However, copper at these high levels reduced microbial activity (CO2 evolution). Conclusions: High levels of copper caused an incomplete mineralization of p henanthrene and possible accumulation of its metabolites. Significance and Impact of the Study: The presence of heavy metals in soils could seriously affect the bioremediation of PAH-polluted environments.