| Atmospheric particulate matter is the direct cause of haze weather.It not only reduces visibility,but also causes deep-seated problems such as health,environment,and ecology.The impact of atmospheric particles on health,environment,and ecology depends on their source,form,particle size,chemical composition and attached microorganisms.Among them,microorganisms are an important part of atmospheric particulate matter,and have a high degree of correlation with particulate matter in morphology,symbiosis,and aerodynamic behavior.Constructed wetlands use the triple synergy of physics,chemistry and biology of substrates,plants,and microorganisms to purify sewage,and are widely used in sewage treatment,pollutant control,and environmental improvement.In this study,a free surface flow constructed wetland sewage treatment system was selected as the research object,and the high throughput sequencing methods were used.Starting from the impact of atmospheric particulates on the structure of microbial communities in air,sewage,substrate,root soil and plant systems,the interaction between atmospheric particulates and microbes in constructed wetland systems was studied.The research results were helpful to clarify the dynamic changes of the air microbial community structure of the constructed wetland sewage treatment system and deepen the research in the field of environmental safety assessment of the constructed wetland.The following conclusions were obtained through study:(1)Air samples were collected through the Andersen type six-stage mesh air microbial sampler to analyze the concentration and particle size distribution of cultivable air bacteria and air fungi.The results showed that the concentration of bacteria varied from 375 to 4890CFU/m3,with the highest bacterial concentration in winter and the lowest in spring.Under the conditions of different capture particle ranges,the proportion of bacterial particles varied from0.87%to 54.72%.The concentration of bacteria with a particle size distribution of 0.65 to 1.1?m was significantly higher than other particle size ranges,and the bacterial concentration with a particle size distribution of 3.3 to 4.7?m was lower than other particle size ranges.The particles that easily entered the lungs accounted for 34.81%to 83.02%of the total particles.The concentration of fungi varied from 587 to 2282 CFU/m3,with the highest concentration in winter and the lowest in spring.Under the conditions of different capturing particle ranges,the proportion of fungal particles varied from 0.63%to 81.46%.The concentration of fungi with a particle size distribution ranging from 1.1 to 2.1?m was significantly higher than other particle size ranges,and the fungal concentration of 0.65 to 1.1?m particles was lower than other particle size ranges.The particles that easily entered the lungs accounted for 57.03%to96.03%of the total particles.(2)The KC-1000 high-flow air samplers were used to collect atmospheric particulate matter TSP,PM10 and PM2.5 samples,and the composition of the bacterial community was analyzed by high-throughput sequencing methods.A total of 80992,32775 and 32175high-quality sequences,2842,1781 and 1713 OTUs were found in bacterial samples in constructed wetland.OTUs came from 21,14 and 14 bacterial phyla,53,42 and 42 bacterial classes,and 687,467 and 471 bacterial genera.The bacterial community diversity of TSP samples was higher than PM10 and PM2.5 samples.Proteobacteria,Actinobacteria,Cyanobacteria,Bacteroidetes and Firmicutes were the dominant phyla,and Alphaproteobacteria and Gammaproteobacteria were the dominant classes in all samples.The relative abundance of Sphingomonas was greater than 1%in all samples.(3)The?diversity analysis of the bacterial community structure in atmospheric particulate matter TSP,PM10 and PM2.5 showed that there were significant differences in the bacterial community composition of atmospheric particulate matter in different seasons.There were also significant differences in bacterial community composition among different components of atmospheric particulate matter(TSP,PM10 and PM2.5).The largest differences were found in genus level clustering,community member similarity and community abundance between November TSP samples and other months samples.The similarity of the sample community structure was highest in December and April.The PM10 sample in winter differed most from PM10 samples in other seasons and all PM2.5 samples,while the similarity of the community structure of the PM10 and PM2.5samples in autumn was the highest.(4)A total of 47,158,47,317,and 47,206 high-quality fungal sequences,1,388,1,373and 1,126 OTUs were found in the atmospheric particulate matter TSP,PM10 and PM2.5 fungal samples of constructed wetlands,respectively.OTUs came from 5,5 and 5 fungal phyla,25?25 and 22 fungal classes,302,317 and 242 fungal genera.Unidentified OTUs were found,and the relative abundance was 0.79%-47.06%.Except for the summer samples,Ascomycota was the first dominant phylum in other seasons.In summer,Mucoromycota was the first dominant phylum in the TSP and PM10,while the relative abundance of Streptophyta was the highest in PM2.5.In spring,autumn and winter,the relative abundance of Dothideomycetes was16.05%?91.29%,but it was not detected in summer samples.The relative abundance of Mucoromycetes in summer was as high as 25.92%?40.53%,but it was not detected in other seasons.Only Penicillium was detected in all samples.(5)The?diversity analysis of atmospheric particulate matter TSP,PM10 and PM2.5 fungal communities in constructed wetlands showed that there were significant differences in the composition of atmospheric particulate matter fungal communities in different seasons.There was no significant difference in fungal community composition among different components of atmospheric particulate matter(TSP,PM10 and PM2.5).The communities of atmospheric particulate matter samples were similar in spring and autumn.The fungal community member abundance and community structure composition of TSP,PM10 and PM2.5 samples were similar in summer,but they were quite different from samples in other season.(6)The RDA analysis was used to determine the relationship between the bacterial community structure of atmospheric particulate matter in constructed wetlands and environmental factors.The results showed that the contribution of axis 1 and axis 2 were 45.0%and 27.6%,respectively.Temperature and humidity were significant positively correlated,NO2,SO2and PM10 were significant positively correlated,while temperature and humidity were negatively correlated with NO2,SO2 and PM10.Hydrogenophaga,Leucobacter and Erythrobacter etc.were positively correlated with temperature and humidity,and negatively correlated with NO2,SO2 and PM10,while Pseudomonas,Rhizobium and Methylobacterium etc.were positively correlated with NO2,SO2 and PM10,but negatively correlated with temperature and humidity.The CCA analysis of fungal community structure and environmental factors showed that the contribution of axis 1 and axis 2 were 63.2%and 19.5%,respectively.Temperature and humidity were significantly positively correlated,NO2,SO2 and PM10 were significantly positively correlated,while temperature and humidity were negatively correlated with NO2,SO2 and PM10.Oryza,Clavaria and Rhizopus etc.were positively correlated with temperature and humidity,but negatively correlated with NO2,SO2,and PM10,while Colletotrichum,Talaromyces and Aspergillus etc.were positively correlated with NO2,SO2,and PM10,and negatively correlated with temperature and humidity.(7)The?diversity analysis results of the bacterial community structure composition in atmospheric particulate matter,sewage,substrate and root soil showed that there were significant differences in the bacterial community structure of sewage,substrate and root soil samples,and different types of samples had clear divisions.The substrate and root soil samples had high similarity,which was different from the sewage samples.Except for the PM10 samples in winter,the level of atmospheric particulate matter was more homologous to the substrate and root soil.The community composition and abundance gradient of community members in atmospheric particulate matter were more similar to sewage and had higher homology.(8)The indoor simulation test methods were used to analyze the effects of atmospheric particulates from different sources(constructed wetlands and urban streets)on the physiological indicators and the microbial community structure on the leaf surface of Haplocladium microphyllum and Hypnum plumaeforme.The results showed that as the concentration of sprayed atmospheric particulate matter increased,the total chloroplast content in bryophytes gradually decreased,and the content of soluble sugar,soluble protein,free proline and peroxidase gradually increased.Hypnum plumaeforme was more sensitive to atmospheric particles than Haplocladium microphyllum.Spraying atmospheric particulate matter would cause differences in the relative abundance of bacteria on the leaf surface of the same bryophyte.The results of PCA analysis,NMDS analysis and UPGMA cluster analysis showed that the samples of Haplocladium microphyllum that were not treated with particulate matter were quite different from other samples. |
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