Influences of polycyclic aromatic hydrocarbons (PAHs) on soil microbial community composition with or without Vegetation

Uptake of three polycyclic aromatic hydrocarbons (PAHs), naphthalene (NAP), phenanthrene (PHN), and pyrene (PYR), from soils by ryegrass, white clover and soybean were investigated in an 8-week pot experiment. The microbial phospholipid-fatty-acid (PLFA) patterns in PAHs-contaminated soil were analyzed. Contamination with PAHs inhibited the soil microbial activity. In non-vegetated soils, the total PLFA showed 87% reduction on the addition of PAHs after an 8-week incubation compared to the PAH-free soil; the concentrations of NAP, PHN, and PYR in soils showed 19.4%, 25.5% and 24.3% reduction, respectively, due mainly to the evaporative loss and microbial degradation. In vegetated soils, the reduction of added NAP and PHN levels was not related to the plant biomass nor to the total PLFA. However, the reduction in PYR concentrations in soil mediated by soybean growth was much pronounced than those by ryegrass or white clover growth, but thisis not related to the total microbial biomass as revealed by PLFAs. The principal-component analysis (PCA) of the PLFA signatures revealed significant changes in the PLFA pattern in PAH-spiked soils when different vegetations were planted. Using the PLFA as a biomarker, it was found that the Gram-negative bacteria were more sensitive to PAHs than Gram-positive bacteria and fungi.

Keywords:

• Phospholipid fatty acid
• PAHs
• Soil contamination
• Microbial community
• Plant uptake

Acknowledgments

We appreciate the critical reading of the manuscript by Dr. Petra Marschner, The University of Adelaide. This research was financially supported by the Ministry of Science and Technology (2002CB410808), the Chinese Academy of Sciences (KZCX3-SW-431).

Notes

*PAH-treated soils after 6-week ageing.

**PAH-free soil without vegetation.

***PAH-treated soil without vegetation.

**Degradation 2: the enhancement of PYR degradation with plant stimulation.