Study On The Pollution Characteristics And Microbial Community Structure Of The River Entering Baiyangdian Lake

Fuhe River is one of the main rivers that flows into Baiyangdian Lake.Its water quality has an important influence on the ecological environment of Baiyangdian Lake.Based on the water quality characteristics of Fuhe River using the upstream urban tail water as supplementary water,this paper systematically analyzed the temporal and spatial changes of nutrients,heavy metals,and microorganisms in surface water and sediments in different seasons.The pollution levels of surface water along the river and the ecological risks of sediments were assessed.The functional genes related to C,N and S transforming were quantitatively analyzed.The relationship between the characteristics of microbial community and environmental factors in surface water and sediments was discussed.It provides theoretical reference and scientific basis for the improvement of water quality and ecological restoration of Fuhe River.The main results are as follows:(1)Atmospheric deposition and sediment disturbance caused by summer rainfall lead to a high degree of water pollution,which is severe pollution.The main pollution factors are NH₃-N,TN and TP.In adddition,the water quality at point F2(rainwater runoff discharge outlet)and point F14(accumulated by domestic wastewater and waste)are seriously polluted.There are significant differences in species diversity,composition and the proportion of dominant species in different seasons.The microbial diversity in summer is higher than that in winter.The abundance of the dominant species Bacteroidetes,Actinobacteria and Firmicutes are lower in summer than in winter,and the abundance of Cyanobacteria is higher in summer.In adddition,species involved in the carbon and nitrogen cycle,such as Flavobacterium?Rhodoferax?Limnohabitans?Arenimonas?Hydrogenophaga and hgcl?clade,are widely present in the surface water.Temperature is the main factor that causes differences in microbial communities.Phosphorus is also an important factor in the biological metabolism of water,which is likely to cause eutrophication of urban rivers.PICRUSt metabolic inference analysis shows that the high temperature in summer promotes the activity of metabolic enzymes,leading to an increase in genes related to metabolic functions in the water.(2)The spatial distribution of nitrogen,phosphorus and heavy metals in sediments caused by different pollution sources is greater than the seasonal variation.The pollution degree of sediment nitrogen is higher than that of phosphorus,and heavy metals are at moderate or light pollution levels.The Cd,Cu,Zn and Pb are mainly from industrial pollution,the Ni and As are mainly from geological processes,and the nutrients is mainly from agricultural non-point source pollution.The diversity and structure of microbial communities are spatiotemporal.The low velocity of water has a weak dilution effect on sediments,resulting in a significantly higher sediment species diversity in winter than in summer,and the diversity is also high at the points with high abundance.The abundance of Proteobacteria is higher in summer,while the abundance of Actinomycetes and Planctomycetes are higher in winter.The abundance of Chloroflexi,Acidobacteria,Gemmatimonadetes and Nitrospirae are not detected in the surface water and are relatively high in all sediment samples.Seasonal and spatial changes in environmental conditions alter the structure and function of the bacterial communities in the ecosystem.The heavy metals As and Ni significantly affect the microbial community structure in the sediments,and OM and TN also have a certain effects on the microbial community structure.PICRUSt metabolic inference analysis shows that the higher abundances of metabolic function genes in winter plays an important role in the carbon and nitrogen cycle.(3)The qPCR quantitative analysis shows that the functional genes related to nitrogen transformation AOA-amo A,AOB-amo A,nir K,nir S,nos Z,carbon transformation functional genes mcr A,pmo A,and sulfate-reducing bacteria functional gene dsr B are more abundant in winter.The abundance of AOB is higher than that of AOA,indicating the existence of eutrophication in Fuhe River.The gene nos Z plays a major role in denitrification.The functional genes related to carbon transformation mcr A,pmo A and sulfur transformation functional genes dsr B,are more abundance in the upstream than in the downstream.(4)Comparing the microbial communities in sediments and surface water,it is found that the microbial diversity in sediments that undertake more ecological functions is significantly higher than that in surface water(p<0.05).The response of sediment microbial diversity to pollution degree is consistent with the response of surface water to water quality,that is,the diversity of water is higher in summer when the water quality is poor,and the diversity of sediments is higher in winter when the content of heavy metal is high.There are 55 phyla of microorganisms in the two groups,and Proteobacteria is the dominant bacteria(42.81%).A total of 1217 bacterial genera are identified,and the dominant genus is Flavobacterium(12.12%).In addition,the abundance of Flavobacterium,Arenimonas,Limnohabitans and Hydrogenophaga in the water are significantly higher than that in the sediments(p<0.05),while the abundance of Thiobacillus in the sediments is significantly higher than that in the water(p<0.05).And there are more unknown species in the sediments.