Plant-assisted degradation of phenanthrene as assessed by solid-phase microextraction (SPME)

The soil bacterium Sphingomonas yanoikuyae was isolated from a petroleum-contaminated soil and grown on mineral salts agar overlaid with the polycyclic aromatic hydrocarbon phenanthrene. The effect of white mustard, Sinapis alba, on phenanthrene degradation by S. yanoikuyae in artificially contaminated Redi-earth-sand was examined. Solid-phase-microextraction (SPME) gas chromatography-flame ionization detection (GC-FID) was used to quantify the concentration of phenanthrene in the gas phase of Magenta jars containing S. alba and S. yanoikuyae, each alone and with no additions. Gas chromatography-mass spectrometry (GC-MS) of Soxhlet extracts was used to determine the concentration of phenanthrene remaining in Redi-earth-sand. The gas phase concentration of phenanthrene in nonsterile Redi-earth-sand decreased by 99.7% in treatments with S. alba plus S. yanoikuyae, by 98.6% with S. alba, by 96.7% with S. yanoikuyae, and by 95.8% with no additions. Under gnotobiotic conditions, the gas phase concentration of phenanthrene in Redi-earth-sand decreased by 94% in treatments with S. alba plus S. yanoikuyae, by 77% with S. yanoikuyae, by 26% with S. alba, and 0% with no additions. The concentration of phenanthrene in Redi-earth-sand under gnotobiotic conditions decreased in treatments with S. alba plus S. yanoikuyae by 88%, by 67% with S. yanoikuyae, by 13% with S. alba, and 0% with no additions as measured in Soxhlet extracts. These results suggest that SPME-GC can be used to rapidly assess the potential of plants and microorganisms to reduce the level of unaged polyaromatic hydrocarbons such as phenanthrene in soil. This method provided results that were consistent with the more costly Soxhlet extraction method and was less time consuming.