Bacteria-assisted phytoremediation of fuel oil and lead co-contaminated soil in the salt-stressed condition by chromolaena odorata and Micrococcus luteus.

Bioremediation of lead-petroleum co-contaminated soil under salt-stressed condition has been investigated. In this study, the co-contaminated soil (780 mg kg^-1 Pb and 27,000 mg kg^-1 TPHs) under the high salinity (EC 7.79 ds m^-1) was used as a model soil to be remediated by Chromolaena odorata inoculated with Micrococcus luteus. The results showed that salt stress caused a marked reduction in dry biomass and stem height, and high accumulation of proline. The presence of salt did not affect the total amount of chlorophyll in plant tissues. No toxicity symptoms were evident from plant morphology after three months of exposure. Drastic differences in the accumulation patterns of Pb in C. odorata grown on saline and non-saline soils were observed and indicated that salinity negatively affected Pb uptake and accumulation. A high rate of degradation of TPHs was observed in non-saline soils with or without bacterial inoculation. Salinity stress showed no significant different in the proportion of TPH degradation with added or non-added M. luteus. The tolerance of C. odorata and M. luteus to moderate concentrations of Pb and fuel oil made them very good candidates for the use in bacteria-assisted phytoremediation of lead-fuel oil co-contaminated soils under the mild saline soils.