Lolium perenne showed resistant to crude oil and good for removal of crude oil (Zhang et al. 2012) as well as metals from contaminated soils.(Jankaitė and Vasarevičius 2007). Jankaitė and Vasarevičius (2007) reported removal of  up to 94% of copper, up to 72% of lead, up to 70% of manganese, up to 90% of zinc, up to 70% of nickel, and up to 80% of chromium from the soil. http://www.lmaleidykla.lt/publ/0235-7224/2007/4/Eko_084_089.pdf

In one experiment ,The physiological and biochemical responses of ryegrass (Lolium multiflorum) to PAH(Polycyclic Aromatic Hydrocarbons) induced stress in soils contaminated with phenanthrene and pyene were investigated, in the presence of PAH-degrading bacteria (Acinetobacteria junii) or arbuscular mycorrhizal fungi (AM fungi, Glomus mossae).

The parameters monitored included chlorophyll content, chlorophyll a/b ratio, soluble-carbohydrate content, soluble-protein, malondialdehyde and electrolyte leakage, and superoxide dismutase (SOD) and peroxidase (POD) activities.

Ryegrass showed good resistance and acclimation to PAH stress in soil, however, PAH contamination resulted in adverse effects such as damage of photosynthetic function and acceleration of shoot senescence. At PAH level of 100 mg kg(-1), chlorophyll contents were 14% lower than control (no PAH). Activities of SOD and POD were more sensitive indicators of PAH stress as compared to other parameters.

However, all parameters showed trends based on either the bioaugmentation of the plants or PAH treatment level. It was concluded that the inoculation of AMF(arbuscular mycorrhizal fungi (AMF) on activities of soil enzymes and carbon sequestration capacity in reclaimed mine soil) and PAH-degrading bacteria, especially the former, have a positive effect on alleviation of PAH toxicity to ryegrass plants. Furthermore, the inoculation of AMF increased the shoot and biomass of ryegrass by 11-19% and 18-78%, respectively. Bioaugmented ryegrass plants show promise as a host plants in the phytoremediation of PAH contaminated soils.

Check this paper:

Phytoremediation efficiency of a PAH-contaminated industrial soil using ryegrass, white clover, and celery as mono-and mixed cultures by 

Meng et al

http://link.springer.com/article/10.1007/s11368-010-0319-y

Likely effect of purposely added PAH or PAH contamination from e.g. sites of coal gasification is merely different from mineral oil contamination from e.g. oil spills is a different matter. Another factor to consider is level and age of contamination.

Thanks Titus, I am interested in an oil spill scenario as well as the significance of level and age of contamination. Could you kindly shed more light on thses please?

Lolium perenne showed resistant to crude oil and good for removal of crude oil (Zhang et al. 2012) as well as metals from contaminated soils.(Jankaitė and Vasarevičius 2007). Jankaitė and Vasarevičius (2007) reported removal of  up to 94% of copper, up to 72% of lead, up to 70% of manganese, up to 90% of zinc, up to 70% of nickel, and up to 80% of chromium from the soil. http://www.lmaleidykla.lt/publ/0235-7224/2007/4/Eko_084_089.pdf

Ryegrass it is a good option as a phytostabilizer plant. For decontamination purposes that depens on: where is located the contamination into the soil profile; time after contamination (aging); topography of the area; soil(s) properties and parameters, etc. For organic compounds contamination the application of assited phytoremediation; combination of ISCO and phyto/bioremediation or the use of selected microorganims / fungi  inoculated in the rizhosphere are good alternatives 

I think you have to choose some plant species which have adventitious root system. Because it could help in two ways; one extended root can reduce soil erosion and secondly, it could spread wide range of area and higher uptake of contaminants.

You can search plant species under Poaceae family, they have adventitious root system.