Oil Saline Soil - Heavy Metals Contamination In Biological Processes Behavior Of Heavy Metals In Environmental Remediation

In recent years, as oil production and consumption increased, the soil is inevitably polluted by oil pollution.The conclusion that petroleum-heavy metals contaminated soil is easy to find is obtained through analysis on soil in the Yellow River Delta. Besides, Bioremediation technology is widely used in the remediation of contaminated soil because of its low cost、without any secondary pollution and good treatment effect. As a complex compound, the intermediates of oil during its biodegradation can influence the existing speciation, bioavailability and migration regularity of heavy metals by completing or chelating,thus causing the secondary pollution in soil. Therefore, the change of environmental behavior of heavy metals during microbial remediation in petroleum-heavy metals contaminated soil should be investigated urgently.As soil cultivation and pot experiment is designed in the lab, the objective of this study was to investigate the change of soil pH and availability and forms of heavy metals during microbial remediation in petroleum-heavy metals contaminated saline alkali soil. In addition, the effect on the change of availability of heavy metals during microbial remediation with amendment in soil is also studied. And ryegrass is planted to verify the improvement effect. The major objective of the present study is to provide some theoretical proofs of the development of practical and effective remediation technology of petroleum-heavy metals contaminated soils.The main results are as follows:The study indicated that the availability of soil Cd and Ni both had a tendency of alternately fluctuating change with the elapsing of time. Besides, their change law was proved significantly different. The oxidizable soil Cd decreased while the reducible soil Cd increased after60days of cultivation. At low concentrations of Cd2+, the acetic acid extractable soil Cd decreased while the residual soil Cd increased. It showed a contrary tendency when at high concentrations of Cd2+.The total amount of the acetic acid extractable, oxidizable and reducible soil Ni decreased while the residual soil Ni increased after being cultured for60days. As a result, the speciation distribution of Ni tended from stable to unstable state with the reduction of active Ni.It showed that soil pH decreased the most obviously when phyto-microbial remediation was experimented in the2%o petroleum-heavy metals contaminated soil. However, the biomass of plant seepweed was less than the single phytoremediation. Besides, the seepweed was more tolerant to Cd than to Ni, and it also had more enrichment effect for Cd than for Ni. The availability of soil Cd and Ni decreased under the phyto-microbial remediation. The concentration of DTPA-extracted Cd was decreased significantly when in the petroleum-10mg·kg-1Cd contaminated soil. While the soil is under the phyto-microbial remediation, the concentration of the acetic acid extractable soil Cd and Ni were the lowest. But oxidizable and reducible soil Cd and Ni increased. So more attention should be paid on the problem of secondary pollution in soil.The amendment decreased the soil pH and alkali-salinity in the2%o petroleum-heavy metals contaminated soil. And the more amendment added, the smaller decreased degree showed. But the difference was not significant. The influence of degrading bacteria on soil pH and salinity changes showed little difference from the control treatment. The amendment played a more important role in the reducing of availability of soil Cd, while the combined effect of amendment and degrading bacteria was more significant to the reducing of availability of soil Ni. Besides, the amendment significantly increased biomass of ryegrass aerial part, and the more amendment added, the better ryegrass growed However, the persistence of the amendment should be improved.The petroleum degrading bacteria had certain degradation ability in petroleum-heavy metals contaminated soil. In addition, the degradation rate of petroleum. hydrocarbons in petroleum-Cd contaminated soil was higher than in petroleum-Ni contaminated soil. The availability of soil Cd is higher in single Cd contaminated soil than in petroleum-Cd contaminated soil, while it is different from Ni. Compared with single heavy metals contaminated soil, the acetic acid extractable soil Cd increased significantly and the acetic acid extractable soil Ni decreased during the remediation in petroleum-heavy metals contaminated soil. The low molecule organic matter produced from the petroleum degradation process can improve the bioavailability of soil Cd while the inactivation of Ni was obvious. It has a great significance for further study of the intermediates of petroleum during its biodegradation on influencing bioavailability of heavy metals.It also can make great value for the remediation in the combined polluted soil.