Bioremediation Of BDE209-Zn Co-containmnated Soil By Pennisetum Americanum And Brevibacillus Brevis

Pot experiments were conducted to investigate the phytoremediation ofdecabromodiphenyl ether (BDE-209) and zinc (Zn), as the model pollutants of polybrominateddiphenyl ethers (PBDEs) and heavy metals in soil by Pennisetum americanum which wasselected by the previous study due to its tolerance and remediation on these two pollutants.Brevibacillus brevis was inoculated to study its enhanced effect on phytoremediation ofBDE-209/Zn co-contamininated soil. Qualitative and quantitative analysis of debrominatedproducts of BDE-209in plants and soils aimed to elucidate the degradation characteristics ofPBDEs in plant-soil system. The research aimed to provide scientific basis onphytoremediation of heavy metals-PBDEs combined pollution in soil.The content of malondialdehyde in P. americanum increased under the stress of pollutants,while the content of soluble protein and the activity of superoxidase dismutase and catalasedecreased beyond the threshold. P. americanum had a certain ability to uptake and accumulatepollutants, and the contents of BDE-209and Zn in roots were significantly higher than thosein shoots. Specially, bioaccumulation factor of Zn in underground plant was up to7.78. Themaximum removal efficiency of BDE-209by P. americanum reached60.73%in BDE-209(5mg kg-1) and Zn (100mg kg-1) co-contaminated soils. And the removal efficiency from high tolow in turn was rhizosphere, nonrhizosphere and no plant, respectively.The accumulation capacity of Zn by P. americanum was significantly increased after B.brevis inoculation, nevertheless, the transportation of Zn was inhibited. And B. brevisinoculation didn’t have significantly positive influence on the uptake and transportation ofBDE-209in P. americanum. The phytoremediation of BDE-209/Zn co-contaminatedpollutants in soil was strengthened by B. brevis, increased by32.46~41.65%than the controlsamples. The combined bioremediation of P. americanum-indigenous microbes contributedmost to the removal of BDE-209in soil, and the most contribution rate was up to35.82%.Although the activity of catalase and urease in soil was strongly inhibited by Zn,combined bioremediation of P. americanum-microbe played a significant role in promotingthem. High concentrations of BDE-209and Zn in soil had negative effect on the content of microbial biomass carbon, soil microbial activity and metabolic capacity of carbon. However,the negative effect could be relieved by planting P. americanum and B. brevis inoculation, andcombined bioremediation of P. americanum-microbe could strongly strengthen theimprovement.About eighteen to twenty lower brominated PBDEs (tri-through nona-BDE) weredetected in soil and plant samples, respectively, with more kinds of the lower brominatedcongeners were detected in the plant tissues than in the soils, indicating the occurrence ofBDE-209debromination in the soil-plant system and further debromination of the lowerdebrominated PBDEs within the plants. Zn also inhibited debromination of PBDEs in theplant-soil system. B. brevis inoculation significantly increased the total amounts of thedebrominated products in P. americanum.