| The black and odorous sediment of urban river is commonly massive,which contents a large amount of organic matter with low redox potential.In such a special habitat,the microorganism which causes black odorous is mass propagation,including sulfur reducing bacteria and part of actinomycetes.They can produce low olfactory threshold compounds such as geosmin,volatile organic sulfur compounds,and 2-Methylisoborneol,etc.through incomplete oxidation of organic compounds in anaerobic environment.The other group includes black and odorous reducing bacteria,e.g.denitrifying bacteria,sulfur oxidizing bacteria and so on.Therefore,microbial community structure variation is vital for the removal of black and odorous conditions from sediments.Adding calcium nitrate and biostimulants,as well as planting submerged macrophytes are effective means of sediment remediation.Previous studies of these methods are more focused on the physical and chemical properties of sediment and overlying water with limited reports on the changes of microbial community structure they brought.We assumed within sediment remediation process,bacteria community composition,especially the functional groups will be varied.In order to verify the hypothesis,we collected black and odorous sediment of urban river,applicated of artificial simulation system to study the effect calcium nitrate(group CN),bio-energizer(group BE)adding in sediment,and planting submerged plants(Vallisneria natanson,group Mac)on the variation of bacteria abundance,diversity and community structure in black and odorous sediment.Meanwhile,the physicochemical properties of overlying water and sediment were measured,to find out the relationship between bacteria community composition and environmental variables.By making a comparasion of bacteria variations through the three commonly used black and odorous reducing treatments,we intend to understand the role of different bacteria in the process of repairing black and odorous sediment and provide theoretical basis for applying bacteria directly or indirectly for sediment remediation.Main results of this study are as follows:(1)After treatments,redox potential in sediment can be improved effectively,while redox potential in group of injection calcium nitrate and biostimulants were significantly higher(p<0.05),and 9.29 and 9.49 times higher than the control group,respectively.The Ignition loss in sediment,which were injected of calcium nitrate,significantly decreased(p<0.05),the reduction was 58.67%.(2)The abundance of bacteria in the sediment of different experimental groups were between 6.18×105~2.97×106 copies/g.The bacterial abundance in group Mac and group CN is less than the control group.The bacterial abundance in group BE has slightly increased than the control group.The Shannon diversity index of experimental groups are between 6.37~6.84,the evenness index are between 0.62~0.65,the group CN is the lowest,while the group BE is the highest.(3)High throughput sequencing revealed a total of 55 phyla,130 classes and 802 genuses of bacteria.The results showed that the dominant bacteria at the level of phyla in different experimental groups are composed of Proteobacteria,Chloroflexi,Firmicutes,Bacteroidetes,Acidobacteria and Deinococcus-Thermus.There are great differences for the abundance of each phyla in different experimental groups,Among them,Deinococcus-Thermus in the treatment group was significantly less than the control group(p<0.05),in the group Mac,group CN and group BE were reduced by 70.20%,79.68% and 73.52%,respectively.SIMPER analysis was carried out on the genus level;the results showed that Ferribacterium,Clostridium,Anaerolineaceae sp.,Xanthomonadales sp.are the bacteria causing bacteria community dissimilarities.Compared with the control group,the abundance of these bacteria in three treatment groups are significantly decreased(p<0.05).The bacterial community structure in group BE is significantly different from that in control group by means of multidimensional scaling analysis.Redundancy analysis(RDA)indicated that the redox potential and pH might be the main environmental factors affecting the bacterial community structure(p<0.05).(4)Based on the analysis of potential special functional bacteria in different experimental groups.Compared with the control group,potential bacteria which causes black and odorous include some sulfate reducing bacteria,iron reducing bacteria,acid producing bacteria and actinomycetes in which treat group are reduced.In group Mac the potential bacteria which causes black odorous: sulfate reducing bacteria,iron reducing bacteria,acid producing bacteria and actinomycetes are decreased by 81.95%,79.64%,71.78% and 68.30%,respectively,lower than that of the control group.In group CN,the potential bacteria which causes black and odorous are decreased by 71.32%,64.20%,65.46%,41.73%,respectively.In the BE group,the reduction bacteria,acid producing bacteria and actinomycetes were reduced by 32.21%,40.61%,and 50.22%,respectively.The abundance of potential reduction bacteria in group Mac was 2.36×104,which is less than that in the control group,but no significant difference(p>0.05);But in group CN and group BE are higher than that of the control group,7.23×104 and 1.36×105,respectively.Redundancy analysis(RDA analysis)showed that the redox potential and pH of the sediment might be the main environmental factors affecting the potential special functional bacteria groups.In summary,after treated by adding calcium nitrate,biostimulants and planting submerged plants,benthic bacteria community composition changed significantly with significantly varied abundances of functional groups.Redox potential might be the main factor accounting for these variations.These findings would help to understand bacteria variations during sediment remediation process and provide useful hints for bacterial application in sediment remediation. |
PDF Full Text Request