Community Structure Of Microorganisms In Urban Rivers Of Pearl River Estuary And The Structure Evolution During Photocatalyic Treatment

There are abundant microbial resources in the urban rivers in the Pearl River Delta region.However,in the process of rapid urbanization,the urban rivers have become an important gathering place for domestic sewage,industrial wastewater,agricultural wastewater and rainwater runoff.The continuous pollution has caused significant changes in the physical and chemical properties of the water bodies.As a result,the microbial community structure and diversity in the urban rivers will be affected.Meanwhile,the enrichment of a large number of pathogenic microorganisms will pose a threat to human health.In this study,microbial communities in typical urban rivers of Nansha District,Guangzhou City were investigated,and were attention to the community structure and diversity of bacteria and fungi in urban rivers under the influence of human activities.The composition and distribution characteristics of pathogenic bacteria were further defined,and their distribution rules were discussed in combination with physical and chemical properties of water bodies.It provides an important data basis for the development and research of microbial resources and the distribution and control of pathogenic microorganisms in the river ecosystem.In terms of the pathogenic microorganisms inactivated,photocatalytic technology was widely studied for its green and efficient advantages,a number of studies are limited in the laboratory simulation of single bacteria sterilization,and the real environment to the influence of complex microbial community in water is rarely involved,restricted its application in the pathogenic microorganisms in situ control.This study uses nano-Ti O2 as the photocatalyst to explore the response of bacterial and fungal communities in natural water to photocatalysis,and to study the inactivation energy of natural water pathogenic microorganisms under photocatalysis and the succession of community structure.Solar energy photocatalysis controls pathogenic microorganisms in water body in situ,thereby reducing their health risks,laying a theoretical and experimental foundation.The primary research contents and summings-up of this thesis are list as follows:(1)Firstly,the physicochemical properties of Nansha Urban River(NUR)had been analysised,including temperature(T),p H,dissolved oxygen(DO),chemical oxygen demand(COD),total phosphorus(TP),absorbance at 254nm(UV₂₅₄),total organic carbon(TOC),nitrate nitrogen(NO3-N)and nitrite nitrogen(NO2-N).The result shows that the NUR suffered serious phosphorus pollution and organic pollution under the influence of human activities.The results of three-dimensional fluorescence and parallel factor analysis(EEM-PARAFAC)showed that the dissolved organic matter in the NUR can be divided into six three-dimensional fluorescent components,of which humus-like substances account for81±3%,and protein-like substances account for 19±3%.The large amount of terrestrial-derived humus substances further proves the serious organic pollution in the water body.(2)The sequence information of bacteria and fungi in the NUR was performed by high-throughput sequencing,and the total effective sequence numbers of bacteria and fungi were 397621 and 602143,respectively.Alpha diversity analysis shows that the abundance and diversity indexes of bacterial communities are greater than fungal communities,such as Ace,Chao and Shannon index.Rivers under intensive human activities(Urban river 4 and 8)contain more microbes and higher diversity indexes.The analysis of microbial community composition showed that the bacterial community was divided into 35 phyla in the NUR,including dominant bacteria phyla Actinobacteria(23.62%?39.24%),Proteobacteria(16.40%?38.80%),Cyanobacteria(8.63%?34.68%),Bacteroidetes(7.34%?13.79%);and dominant bacteria classes Actinobacteria(23.62%?39.24%),Oxyphotobacteria(8.59%?34.52%),Gammaproteobacteria(10.98%?25.86%).The fungal community was divided into 9 phyla,while Ascomycota(26.61%?70.36%)was the dominant fungal phylum in all water samples;Pezizomycotina?cls?Incertae?sedis(9.08%?69.80%)and unclassified?Ascomycota(0.30%?17.26%)were the main fungal classes.Moreover,the pathogenic bacteria community was divided into 8 phyla and 35genera,while Mycobacterium(27.42%?42.01%)belonging to Actinobacteria was the most dominant bacteria in all water samples.(3)Redundancy analysis and Heatmap correlation analysis showed that the influence of the community structure of microorganisms and pathogenic bacteria in the NUR is the result of a variety of environmental factors,of which TP is the most important factor that can promote the growth and reproduction of a variety of microorganisms.TP had a significant positive correlation with ten bacterial class,eg.Nitrospira(r=0.76,p<0.01),Subgroup?6(r=0.75,p<0.01),thirteen fungal class,eg.Agaricomycetes(r=0.78,p<0.01),Chytridiomycetes(r=0.75,p<0.01),Acinetobacter(r=0.65,p<0.05),and nine pathogenic bacteria genera including Burkholderia-Paraburkholderia(r=0.70,p<0.05).(4)In order to study the effect of photocatalysis on the structure of microbial community,two natural water samples with obvious differences in microbial structure were selected for further research.The results showed that microorganisms in different water bodies have different sensitivity to photocatalysis.In the water where the bacterial concentration dropped by 1.21 log cfu/m L after 12 hours of photocatalysis,the relative abundance of Bacteroidia,Anaerolineae,Dothideomycetes,Saccharomycetes,Sordariomycetes,Eurotiomycetes,and pathogenic bacteria Mycobacterium,Legionella,Mycoplasma,and Bacteroides were all significantly reduced.