| Airborne microorganisms are one of the most important components of urban ecosystem.Though they have a lot of beneficial effects to humans,they also cause a lot of harms to human health and well being,and their quantity is one of the important indicators to evaluate environmental quality.In recent years,due to the continuous deterioration of urban environmental air quality and the frequent appearance of fog and haze,the studying on urban airborne microbes has attracted a lot of attention.The purpose of this research on Lanzhou air microbial concentration,distribution and diversity is to accurately understand the city air microbial community and ecological function and to lay the foundation of providing scientific basis for the evaluation of air microbial quality in the environment as well as its affects on human's health.In this study,the air samples collected from different functional regions of Lanzhou comprising of Scenic Area(SA),Main Traffic Line(MTL),Public Service Area(PSA),Culture and Education Area(CEA)were used as the research materials,mean while the culture-dependent and the Biolog method were use to study the air microbial concentration,particle size,spatial distribution,characteristics of airborne microbial community and functional diversities in relation their carbon metabolism rate and also,to clarify the correlation between the concentration of airborne microbial community functional diversities and environmental factors.Using molecular biology techniques,composition of pathogenic inhalable airborne bacterial during spring in Lanzhou was analyzed.The major findings are as follows:(1)The concentration of airborne microbes,bacteria and fungi in Lanzhou had obvious spatial,seasonal and diurnal variations,and there was a good correlation between the changes in airborne microbial biomass and environmental factors.In Lanzhou City,the air microbial concentration was in the range of 196 ~ 3752 CFU/m3,the air bacterial concentration was in the range of 83 ~ 3344 CFU/m3,while the concentration of airborne fungi was in the range of 102 ~ 1315 CFU/m3,in average,the concentration of airborne bacteria in Lanzhou city was 916 CFU/m3,while that of airborne fungi was 322 CFU/m3,the airborne bacteria had a larger concentration of 66.5% compared with airborne fungi.Microbial concentration and airborne bacteria concentration in the four functional areas were consistent and the same: MTL > PSA > CEA > SA,the concentration of airborne fungi in order of size was: SA > PSA > CEA > MTL.The assessment of airborne microbial contamination of each functional area in Lanzhou city shows that the MTL and PSA airborne bacterial contamination level was relatively high compare to that of the contamination level of the total airborne microbes and airborne fungi.Air microbial concentration was higher in spring,summer;while in autumn and winter it was relatively low.The concentration of airborne bacteria reached its lowest level in autumn because of the presence of haze in the atmospheric weather,in winter;there was an increased in the concentration of bacterial.Seasonal difference in airborne fungi concentration among the different functional areas was small.The concentration of microorganisms in the air at SA was high at 13:00 and low at 17:00,The variation of total airborne microbes and bacterial concentration in the air at MTL and PSA was as follows: 9:00>17:00>13:00,the variation in airborne fungi concentration was of the following sequence: 13:00>9:00>17:00,airborne concentration in the air at CEA was as following variation: 9:00 > 17:00 > 13:00.The concentration of bacteria was positively correlated with temperature and negatively correlated with wind speed and humidity.In Lanzhou,the total microbial biomass and bacterial concentration had a positive correlation with temperature,but negatively correlated with wind speed and humidity.Also,the correlation between airborne fungal concentration and temperature,humidity and wind was weak.(2)In reference to the spatial distribution characteristics of airborne microbes in Lanzhou.The bacterial particles were mainly distributed between level one to three(> 3.3 ?m),this form of distribution was skewed,however the particle size distribution of airborne fungi was normal which was mostly in the size range of 2.1 ?m-7 ?m.In the four functional areas,inhalable lungs bacterial particles accounted for 23.1% ~ 28.9%,while inhalable lungs fungal particles accounted for 33.7% ~ 40.7%.Within the four seasons of one year,the concentration of inhaled lungs bacterial particles is high in autumn and winter,while concentration of fungal particles inhaled into the lungs are high in spring and autumn.On a daily basis,the bacterial concentration of inhaled lungs bacterial particles was high at 9:00 and 13:00,while the concentration of inhaled fungal particles was high at 9:00 and 17:00.In Lanzhou city,the median diameter of airborne bacteria was about 3.68 ?m,the airborne fungal median diameter was about 3.15 ?m.The median diameter of airborne bacteria was greater than the median diameter of airborne fungi.The variation of airborne bacteria in different seasons was in the range of 3.06 ?m~4.11 ?m,spring and summer had a comparatively larg variation.The seasonal variation in the median diameter of airborne fungi was between 2.74?m ~ 3.59?m,during the summer season,the median diameter value was great.The median diameter value of airborne bacteria was great at 9:00,while the median diameter of airborne fungi was great at 13:00.(3)There were significant differences in the overall utilization of carbon source in the four functional areas during each season,in spring and autumn,the microbial carbon sources utilization rate at SA and PSA were higher than that of other two functional areas,in summer,the sample from SA has the highest carbon sources metabolism rate compared with othes,while in winter,the microbial carbon sources metabolism rate was comparatively high in samples from CEA,PSA and SA.There was no significant difference in Shannon index and Simpson index among the airborne microbes in the four functional areas during the four different seasons.This shows that the microbial community richness and dominance were similar in the four functional areas,however,the difference in McIntosh index shows that the difference among the microbes was comparatively large and also shows that the microbial communities in different functional areas were affected by different environmental factor and weather conditions,the influence of weather conditions was comparatively larger.There were regional differences in the carbon metabolic function of microbial communities in different seasons,and these differences led to the main differentiation of carbon source that was utilized.Amino acids were the main types of carbon sources responsible for the regional differences in carbon metabolism process among airborne microbial communities in Lanzhou during spring and autumn.The major types of carbon sources that were use by airborne microbes for their microbial carbon metabolism function at the different functional areas in summer were carbohydrates,while that of winter were alcohols.There were also differences in the carbon metabolism rate by airborne microbes at the four functional areas.The airborne microbial carbon metabolism rate at SA is high in spring and summer,while the airborne microbial carbon metabolism rate at MTL and PSA are high in autumn and winter,the airborne microbial carbon metabolism rate at CEA is high in winter,with little differences in summer and autumn.There was no significant difference between the Shannon index and Simpson index in different seasons,indicating that the richness and dominance of microbial community in the same functional area did not change much with the seasonal variation,however,the difference in McIntosh index shows that there was a seasonal variation among airborne microbes,indicating that that the microbial communities in different functional areas were affected by different environmental factors and weather conditions.Also,the airborne microbial community carbon metabolism rate and functions at the four functional areas indicates seasonal differences.Carbohydrates were the main types of carbon sources responsible for seasonal differences in microbial community's carbon metabolism rate in SA and PSA.(4)There were significant differences in the composition of lungs inhalable airborne bacterial at the different functional areas in Lanzhou,48 species,divided into six phylums,namely;Actinobacteria,Cyanobacteria,Deinococcus Thermus,Firmicutes,Proteobacteria,Saccharibacteria were detected.CEA and SA had high similarities between their bacterial communities,MTL and PSA had different and independent evolutionary process.The size of lungs inhalable airborne particles was less than 3.3 ?m,the longer of the airborne microbes stay in the air,the greater of the length of distribution.This increases the spread of diseases as well as human risk to infections.Among the inhalable airborne bacterial found in Lanzhou,9 kinds of pathogenic bacteria were detected.The distribution of these pathogenic bacteria also had spatial differences,and the detection rate was high in densely populated areas. |
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