A Study On The Combined Repair Of Fluoranthene-contaminated Plants In The Sediments Of Rivers

Polycyclic aromatic hydrocarbons(PAHs)are known as toxic,mutagenic,carcinogenic,and very dangerous to human health.River sediments polluted by PAHs is a serious problem in China.High molecular weight polycyclic aromatic hydrocarbons(H-PAHs)are more virulent and more difficult to be degraded,so become the focus and difficulty of PAHs pollution control in river sediments.In this paper,we chose fluoranthene as the representative of H-PAHs,because it has high detection frequency and abundance in H-PAHs.The mechanism of the removal of fluoranthene from river sediments by the combined plant-microbial remediation was studied.Calamus,reeds,zizania and lythraceae were planted on the sediments polluted by the fluranthene.The results showed that calamus was the best species to remove fluoranthene,with removal rate of 55.36%after 90 days.Further study showed that fluoranthene was mainly removed by calamus plant degradation because of its large root system and higher root flora.After high-throughput analysis,it was confirmed that the flora structure of calamus was significantly changed.The dominant bacteria changed from Bacillus,Hydro,Candida,etc to Rhodococcus,Mycobacterium,Penicillium,etc.Two fluoranthene-degrading bacteria strains were screened out from the sediments near calamus roots.The two strains were identified as Rhodococcus aetherivorans strain IcdP1 and Penicillium purpurogenum strain DTQ-HK1 through the morphological observation and gene sequence analysis.The best conditions for the growth of the two strains was studied,and found the optimal concentration of fluoranthene was 50mg/L,the optimal temperature was 30?,the optimal pH was 7.Different heavy metal ions on growth were investigated.Results showed the presence of Zn2+ and Cu2+ could inhibit the growth of the two strains,and the inhibiting effect of Cu2+ was stronger than Zn2+.The degradation mechanism of fluoranthene by fluoranthene degrading bacteria was further studied.Glucose,maltose,calamus root exudate,HA and anthracene-phenanthrene mixture were chosen as the external carbon source,and their promotional effect on degradation of fluoranthene was researched.The results showed that glucose was the best external carbon source for Rhodococcus aetherivorans strain IcdP1,and the best adding dose was Cglucose:C fluoranthene=1:1.We also found maltose was the best external carbon source for Penicillium purpurogenum strain DTQ-HK1,and the best adding dose was C maltose:C fluoranthene=3:5.The addition of glucose and maltose could promote the dissolution of fluoranthene and promote the growth of the strain.The degradation of fluoranthene was first-order kinetics degradation before and after adding carbon source,but the degradation rates were obviously different.After 42 days of incubation,the degradation rate of fluoranthene was 37.46%by Rhodococcus aetherivorans strain IcdP1,after adding glucose with the adding dose was C glucose:C fluoranthene=1:1 the degradation rate up to 76.30%,and the degradation rate of fluoranthene was 52.22%by Penicillium purpurogemum strain DTQ-HK1,after adding glucose with the adding dose was C maltose:C fluoranthene=3:5 the degradation rate up to 81.75%.The dosing method of external carbon source was studied and found that sectional dosing method was better than the one-piece dosing method.Then the degradation products of fluoranthene were determined by GC-MS.When the fluoranthene was used as the sole carbon source,the degradation of fluoranthene was not complete,and the products were mostly benzene-containing,heterocyclic or long-chain compounds.After the addition of carbon source,the degradation of fluoranthene was more thorough.Especially after adding Penicillium purpurogenum strain DTQ-HK1 and maltose,the degradation products mainly consist of short chain small molecules.The reinforcement of external carbon source and fluoranthene-degrading bacteria on plant-microbial remediation was studied.Calamus was planted on the sediments polluted by the fluoranthene.After inj ecting Penicillium purpurogenum strain DTQ-HK1(with the concentration was OD600=2.the dosage was40mL)and maltose(C maltose:C fluoranthene=3:5)to the sediments near calamus roots,their removal efficiency of fluoranthene was up to 100%through 90d growth.