Effect of different diesel treatments on growth of single and mixed plant communities and petroleum hydrocarbon dissipation during rhizoremediation

The use of mixed plant communities has been proposed to address phytotoxicity while improving plant stress tolerance and contaminant degradation. However, there has been conflicting findings on the use of mixed plant community. This study assessed the impact of three diesel treatments on plant growth and TPH dissipation in single and mixed plant communities. This involved greenhouse experiment with Medicago sativa, Festuca arundinacea, and Lolium perenne and Medicago sativa + Lolium perenne with the diesel-spiked soils at 102,000, 151,000 and 320,000 µg kg-1 TPH represented as Treatments 1, 2 and 3 respectively. Plant growth was inhibited with root biomass yield was greater compared to plant shoots especially for F. arundinacea and L. perenne. There was a significant decrease in the root biomass yield of M. sativa, L. perenne, F. arundinacea and M. sativa + L. perenne. The highest TPH dissipation of 81, 69 and 72 % was displayed by L. perenne in the Treatments 1, 2 and 3 respectively. However, TPH dissipation was generally comparable for the vegetated and unvegetated soil and were not significantly different (p>0.05) for the different plants and treatments. The impact of plant communities on the rhizoremediation of TPH-contaminated soils may dependent on factors such as plant species, TPH concentration stress tolerance and benefits of individual plant if mixed plants are to be employed.