Bioremediation Of Polychlorinated Bipheny1 Contaminated Soil

Polychlorinated Biphenyls (PCBs), as persistent organic pollutants, have been extensively studied because of their long-range transport capability, bioaccumulation, persistence and endocrine disrupting toxic effects. Dismantling and improper storage of electric power capacitors and transformers which contain PCBs in Wentai region of Zhejiang province had lead to the surrounding soil pollution. Human health, agricultural safety and ecosystem are seriously threatened. Bioremediation of PCBs contaminated soil needs to be carried out urgently. Bioremediation is a promising alternative approach to soil remediation due to its cost effectiveness, convenience and envi ronmental acceptability. In this study, a range of organic substances were selected to stimulate the indigenous microorganism, in order to find the suitable additive and the most effective concentration. The rhizosphere effects of two plant species grown alone and their combination on the removal of PCBs were also studied. The soil microbial community structure and diversity, the abundance of BphAl genus were also analyzed by using PCR-DGGE and Real time-PCR technology. The main results were as follows:(1) Amendments with biphenyl, glucose, secondary plant metabolites (salicylic acid, carvone, naringin) and non-ionic surfactant Trinton X-100 could significantly improve PCBs removal. The most effective additive was salicylic acid. These organic substances could significantly enhance the dissipation of PCBs in ryegrass rhizosphere, but higher degradation rates of PCBs were observed in those without ryegrass. PCBs removal increased at first and then declined with the increased concentrations of salicylic acid. The most effective concentration was 10mmol/kg. PCBs removal was no significantly correlated with soil dehydrogenase activity and catalase activity. Some bacterium related with degradation of organic pollutants in DGGE band sequencing included:Sphingobacteriales, Rhodanobacter sp., Sphingomonas sp., Burkholderia sp. Xanthomonadaceae and so on. The relative abundance of BphAl gene in treatments of fertilization and certain concentration of salicylic acid was significantly increased. The relative abundance of Gram-negative bacteria was significantly higher than that of Gram-positive bacteria.(2) Significantly higher PCBs removal in rhizosphere of different plants and mixed species were observed compared to the unplanted treatment (tall fescue> the combination> alfalfa). The abundance of bacteria in rhizosphere soil was significantly increased (the combination> tall fescue> alfalfa). PCBs removal in soil was no significantly correlated with dehydrogenase activity and catalase activity. A number of different bands in DGGE profiles were sequenced which included some bacterium related with degradation of organic pollutants:Acidobacteriaceae, Benzo[a]pyrene-degrading bacterium., Streptomyces sp., uncultured Pseudomonas sp., Thermomonas sp. and so on. The relative abundance of others three groups of BphA1 gene in the planted treatments was significantly increased except for Bph3 gene. The relative abundance of Gram-negative bacteria in rhizosphere was significantly higher than that of Gram-positive bacteria.