| Polybrominated diphenyl ethers (PBDEs), a new type of persistent organic pollutants (POPs), have the characteristics of environmental stability, high biological accumulation and high toxicity. Deca-BDEs (BDE-209) was mass detected in soil ecosystem among all PBDEs, therefore it has became a research hotspot. In order to explore the bioaccumulation of PBDEs by Sedum alfredii and the migration and transformation of PBDEs in the plant-soil system, an addition of 0,2.5,5,10,15,20 mg kg-1 of BDE-209 was added into the soil. The influence of BDE-209 on the soil enzymes and microbial signal molecular secretion as well as the interaction effect between signal molecular and enzyme activities was investigated. On the basis of pot experiment, an AHL-QS regulation experiment was set to accelerate the degradation of BDE-209 and study the action mechanism of AHL-QS regulation, thus provide new approach for the BDE-209 phytoremediation. The results were as follows:(1) Among all the BDE-209 treatments (0,2.5,5,10,15,20 mg kg-1), the growth of Sedum alfredii was influenced in the treatment of 20 mg kg-1. Sedum alfredii appeared accumulation ability (with the tendency: stem>root>leaf) on BDE-209, and the bioconcentration factor decreased with increasing BDE-209 treatment. BDE-207, BDE-196 and BDE-183 were the main lower brominated PBDEs in the plant. BDE-99 and BDE-28 were only accumulated in leaf, while BDE-47 was mainly detected in root and stem. The degradation and transformation of BDE-209 was strengthened in the rhizosphere of Sedum alfredii.7-9 borminated PBDEs were the main lower brominated PBDEs in the non-rhizosphere soil, while there were more 3～6 borminated PBDEs in rhizosphere soils, which indicated that the rhizosphere of Sedum alfredii could improve the transformation of BDE-209 to lower brominated PBDEs.(2) The microbial biomass was not influenced by BDE-209 under the concentration of 2.5-5 mg kg-1. In the 15 mg kg-1 and 20 mg kg-1 BDE-209 treatment, the microbial biomass was improved by BDE-209 first (first harvest) and then inhibited (second harvest) with increasing times. The activities of dehydrogenase, phosphatase, FDA hydrose and urease were improved by BDE-209, while glucosidase, nitrate reductase and sulphatase were inhibited. Signal molecules (N-acyl-homoserine lactones, AHLs) were detected in all BDE-209 treatment soil, and C4-HSL was dominant. The secretion of microbial signal molecular was improved by BDE-209 in the treatments of 2.5～10 mg kg-1 BDE-209, while significantly inhibited in the treatments of 15～20 mg kg-1 BDE-209. The variation trends of nitrate reductase, glucosidase and FDA hydrose were highly consistent with the variation trend of signal molecular (C4-HSL).(3) The growth of Sedum alfredii was not significantly influenced with addition of Pseudomonas aeruginosa in BDE-209 contaminated soil. AHLs-QS regulation could improve the microbial biomass in the soil, and the microbial biomass increased with increasing of AHLs addition. The soil enzyme activities were increased (the increase rate:Sulphatase>nitrate reductase>glucosidase>phosphatase>urease>FDA hydrose) under AHL-QS regulation, however dehydrogenase activity was not influenced by AHLs signal moleculars. The Sedum alfredii accumulation ability of PBDEs as well as the degradation of BDE-209 in soil was improved under AHLs-QS regulation. The degradation rate was not significantly influenced by Pseudomonas aeruginosa. However, the bioaccumulation ablity of PBDEs by Sedum alfredii as well as the lower bromated PBDEs content in soil decreased when added Pseudomonas aeruginosa. |
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