Bioremediation Of BDE209-Cu Co-contaminated Soil By Bacillus Thuringiensis And Ryegrass

Decabromodiphenyl ether (BDE209) and heavy metals Cu were chosen as the targetpollutants, and the effects of ryegrass (Lolium multiflorum Lam) on the remediation ofBDE209-Cu combined contamination by adding Bacillus thuringiensis were investigated. Themain research incuded: comparing the ryegrass and alfalfa (Medicago sativa L.) tolerance anddegradation of BDE209in soil separately with the seed germination and pot experiment and thenfind the host plant; conducting research on the ryegrass's seeding growth, physiological indexunder the single pollution of BDE209, Cu and the co-contamination of these two if inoculated B.thuringiensis or not and the change of catalase activity in soil; investigating the absorption andaccumulation of Cu and BDE209in the ryegrass; At the same time, the morphology of the rootand leaves were observed with scanning electron microscope (SEM).The results indicated that ryegrass and alfalfa had tolerance against the BDE209pollutionand in soil. The BDE209concetration had significant negative correlation with theryegrass'seeding germination and fresh weight, promoted the root and shoot length on thecontrary. The alfalfa was also had negative correlation with the concentration of BDE209.Biomass and degradation capacity of ryegrass were greater than alfalfa, and the remove rate ofBDE209in1mg/kg could up to73.60%after growing90days. What'more,the ryegrass couldalso tolerate the BDE209-Cu co-contamination in soil.B.thuringiensis could increase the concentrations of malonydialdehyde (MDA) andsuperoxide dismutase activity(SOD) in ryegrass's leaves.The addition of B.thuringiensis affecteddeeply the growth of ryegrass in autocaved soil, which could accelerate the increase of biomass,chlorophyll and SP obviously, and decrease the content of MDA. The activity of SOD wasenhanced by B.thuringiens in the situation of single pollutant, and it was inhibited when thereexisted the combined pollutants of Cu and BDE209. Ryegrass turned out to be shorter rootlength, less biomass and chlorophyll in presence of combined pollutants. When the soil was notautocaved, the content of MDA was less if B.thuringiensis was added, and it showed adverseresults in autocaved soil. The viriation of soluble protein (SP) didn't appear any regular pattern.The pollutants(BDE209and BDE209-Cu) decreased the soil catalase activity,and to some extentthe activity was recovered by B.thuringiensis. Ryegrass could acculmulate some Cu and BDE209. And the accumulation ability of theunderground part was greater than the overground part. The contents of Cu saved byunderground part of ryegrass were up to3309.98mg/kg in unautocaved soil and hadaccumulated10.44mg/kg BDE209when growing at10mg/kg BDE209after addingB.thuringiens.The accumulation of BDE209by the undergroud parts could be accelereted by B.thuringiensis when single pollutant as well as combined pollutants existed. In the unautocavedsoil, B. thuringiensis could inhance the accumulation of BDE209by overground parts, while inthe combined contamination, it had the adverse effects. When the soil was autocaved, theaccumulation of BDE209by plant could be accelerated by adding of B. thuringiensis.Plant uptake contributed to0.02%~0.31%of the loss of BDE209in the soil.The plant andrhizosphere microorganism were the main factors contributed to the removal of BDE209in soil.B.thuringiensis enhanced the ryegrass repairing capability of BDE209in soil. The remove ratewas up to48.02%after45days greenhouse experiment when the BDE209concentration was1mg/kg in soil.The effects of rhizosphere soil were superior to nonrhizosphere soil under all thetreatments.The hairy root in the ryegrass root system was much with adding B.thuringiensis. Theco-contamination had destroy on the morphology of ryegrass, which decreased the amount ofhairy root and made the surface of root system rough. At the single BDE209pollution and theBDE209-Cu combined contamination, there were many white flocculated globule.There werealso a lot of flocculent materials adhered to the leaf when BDE209was added, many mesh thingscould be seen if Cu existed together, which showed that the structure of the leaf was destroied bythe pollutants.