Characteristics And Microbial Population Structure Of Railway Station Tail Water Treated By Natural Wetland In Frigid And Anoxic Area

In recent years,the frigid and hypoxic region of the Qinghai-Tibet Plateau is an ecologically sensitive area,and it is difficult to find suitable water body for the tailwater of the Qinghai-Tibet railway station section.Dispersed water bodies in some areas are discharged nearby,which has become a major challenge for water environment governance in alpine and hypoxic regions.There are relatively few studies on the impact of tail water on the ecological functions of receiving water bodies.These issues deserve widespread attention.This research takes the natural wetland that has been operating stably near the Chahanno Wastewater Treatment Station from 2006 to the present as the research object,and monitors the pollution status of the wetland to the tail water of the Chahanno Wastewater Treatment Station along the railway line.High-throughput sequencing technology is used to study the composition and diversity of the free-type and attached microbial populations in the wetland system,and to analyze the correlation between the microbial community and environmental factors in the wetland.The main research results are as follows:(1)After the tail water of the sewage treatment station flows into the Chahannuo Wetland,the pollution cleaning effect of the wetland is analyzed,and the study found that the COD concentration at the end of the wetland is 34.62mg/L.The concentration of NH₄⁺-N and TN are0.03mg/L and 0.42mg/L,respectively,and the concentration of TP is 0.36mg/L.The water quality reaches the"Surface Water Environmental Quality Standard"(GB3838-2002)Class V water.The p H of the sediment gradually decreases along the direction of the water flow,and the content of total nitrogen and total phosphorus in the sediment is relatively high.And there are significant differences(P<0.05)and extremely significant differences(P<0.01)in total nitrogen and total phosphorus between the initial position of the wetland and the end of the wetland,respectively.It can be seen that the natural wetland has a good purification effect on the tail water of the sewage treatment station.After the wetland treatment,the carbon,nitrogen,phosphorus and other biogenic substances in the sediments at different locations in the wetland system have different degrees of difference.(2)The main dominant bacteria phyla in the Chahanuo wetland system are Proteobacteria,Bacteroidetes,Actinobacteria,Chloroflexi and Firmicutes.The main dominant genera of free microorganisms are Flavobacterium(9.17%?30.01%),Limnohabitans(5.33%?29.89%),Hydrogenophaga(5.05%?13.43%)and Rhodoluna(2.40%?15.10%)etc.,The main predominant genera of the attached microorganisms are Anaerolineaceae(f)(4.05%-9.57%),Thiobacillus(0.95%?3.77%)and Bacteroidetes?vadin HA17(f)(1.65%?2.92%)etc.The microbes in the Chahanno wetland system are complex and diverse,and there are still a large number of microbes that cannot be identified at the genus level.These potential new species need to be studied later.(3)Microorganisms are a key participant in the purification process of wetland tail water.Proteobacteria and Bacteroidetes are widely distributed in water bodies and sediments,and participate in the cycle of carbon,nitrogen and phosphorus in the whole process.Actinobacteria can decompose dead bacteria and fungi in the water in the middle of the wetland.Firmicutes are mainly involved in carbon and nitrogen cycles in sediments.Chloroflexi plays an important role in the decomposition process of litter.Compared with free microorganisms,Chloroflexi is more abundant in attached microorganisms.Flavobacterium plays an important role in the cycle of carbon,nitrogen and phosphorus in the wetland by using the product of degrading organic matter as the carbon source of the denitrification process.Anaerolineaceae(f)is a dominant species closely related to the formation of biofilms among attached microorganisms.(4)Correlation analysis shows that total phosphorus,total nitrogen and ammonia nitrogen have a greater impact on the population structure of free-type microorganisms,while total phosphorus,total nitrogen,p H and water content have a greater impact on the population structure of attached microorganisms.Studies have found that among the attached microorganisms,Thiobacillus,f??Steroidobacteraceae,Rhodoferax,and f??Rhodocyclaceae have a negative correlation with temperature.Among the free microorganisms,Rhodoferax and Hydrogenophaga are cold-tolerant microorganisms with denitrification function,indicating that there are a large number of bacteria in the wetland system that participate in the cycle of carbon,nitrogen and phosphorus and adapt to the extreme conditions of the alpine hypoxic area.