| Summary: | 碩士 === 國立成功大學 === 環境醫學研究所 === 104 === Objectives: Taiwan located off the southeastern coast of mainland China. Its climates are affected by northeasterly wind every winter. The strong wind transport air pollutants included dust particles from China continent to Taiwan, the sources associated with desert sources and industrial emission at coast that namely Asian dust storm (ADS) and frontal pollution case (FP), respectively. Besides, the microbes also are dispersal accompanied with air pollutants through long-range transport in atmosphere, the ambient bacteria might cause influences to Taiwan in relation to climate, ecology agricultural and human health. Hence, it is necessary to understand the information about the ambient bacteria related to long-range transport (LRT) in Taiwan. However, previous studies of LRT events only focus on the ADS, even though the FP case which occurs about once a week during the prevailing northeasterly winds might often affect the bacterial concentration and community diversity in the atmosphere. Thus FP case also is importance in the research of LRT events in Taiwan, but the distribution of ambient bacteria associated with the FP case is still unknown. as well as few information about with bacterial community structure of LRT events in Taiwan. The aims of this study were to investigate abundance, diversity and community composition of ambient bacteria in FP case (before, during and after event period), as well as compared the variation of community composition between ADS and FP case.
Materials and methods: The sampling of FP case was performed from November of 2014 to April of 2015 at National Taiwan University of Taipei city (urban) that for the bacterial abundance and diversity analysis. Moreover, two LRT events and background days collected from 2013 to 2014 at Cap Fukuei of the northernmost of Taiwan (rural) and National Taiwan University (urban) were selected for the bacterial community composition analysis, the LRT events included ADS and FP case. Air pump collected to filter holder (Teflon filter) was sampling at 30 LPM for 24 hours. In addition, the information of Japan Meteorological Agency, Taiwan EPA, Taiwan CWB and Taiwan RCEC are used to evaluate the arrival time of LRT event. The sampling was performed at the two days before LRT to the two days after the end. After sampling, the data of meteorological factors, air pollutants and air mass trajectories of HYSPLIT model are applied to estimate the effect level of LRT event and confirm whether ADS or FL case, and classified to before, during and after event period. Abundance of total and viable bacteria was analyzed using quantitative Polymerase Chain Reaction (qPCR) and the viable bacteria was treated by Propidium Monoazidein (PMA) before the DNA extraction. Total bacterial diversity was analyzed using PCR-based Terminal Restriction Fragment Length Polymorphism (T-RFLP). The total bacterial community composition was analyzed using Next-Generation Sequencing (NGS).
Results: A total of 5 cases were collected in FP occurrences. For the bacterial abundance, the total bacterial concentrations in all five cases increased during the FP case as compared with those seen in the before period, and decreased to levels similar to before period when the FP case ended, except the case in November still kept a relatively high concentration and the one in February saw a small increase. The viable bacterial concentrations in the cases in November and December decreased during the FP case as compared with those in the before period. In contrast, the concentrations in March increased during the FP case.
For the total bacterial diversity, richness, H index and evenness revealed an increase during the FP cases as compared with the before period, and most of those values decreased in the after period although the H index and evenness in November both increased.
For the total bacterial community composition, at phylum level, both of ADS and FP case, the bacterial communities among all samples of CF and NTU location were also dominated by phylum Proteobacteria, and Firmicutes of those were increased during and after event periods. At Proteobacteria-related community of glass level, in generally, both of ADS and FP case, the communities of background day and after period of both locations were dominated by Alphaproteobacteria, the during period of both locations were dominated by Betaproteobacteria. At Firmicutes-related community of glass level, for the ADS, the Clostridia were detected with high abundance in community of during period of CF location, the communities of after period of both locations were dominated by Bacilli; for the FP case, the communities of during period of both locations were dominated by Bacilli and the Clostridia were detected greatly in the community of after period of CF location. At Cyanobacteria-related community of glass level, for the pollution case, the populations of Nostocophycideae were increased highly in the after period of CF location.
At genera level, for the ADS, the community structures of background day between CF and NTU location were similar, those in during period also were observed, the characteristic populations were Roseomonas and Clostridium, respectively; the communities of after period of CF location involved with the populations of Salinicoccus, whereas the after period of NTU location related to Janthinobacterium; the populations of Ralstonia and Delftia were detected greatly in during period of CF location, the Streptococcus were detected with relatively high level in the communities of during and after period of NTU location. For the FP case, the Paracoccus was detected greatly in background day of both locations, as well as Bacillus and Ralstonia in during period of both locations, the communities among after period of CF and NTU locations were grouped and dissimilar to other samples, the typical population in CF location was Faecalibacterium and Calothrix, whereas the NTU location was Flavobacterium. Sphingomoas was the major contributor in all bacterial communities of both locations of ADS and FP case.
Conclusions: The FP case created a significant increase in total bacterial abundance, probably 10-fold higher than in the before period, and fell to a level similar to that seen in the before period following the end of the FP case; whereas the change of viable bacterial abundance was different in various months that may be related to the effect of seasonal atmospheric processes, it is need more cases and detail study in future to obtain thorough results. Moreover, the FP case introduced the bacterial community structure more complex and even.
The members of Clostridium, Bacillus, Ralstonia and Delftia, which thought to have been carried by the pathways of ADS events, were predominant at CF location. The members of Bacillus and Ralstonia, which carry from industrial areas at the coast of eastern China, were detected greatly at CF location. Some of species also would dispersal to NTU location urban areas, and the community was affected by low-degree LRT from industrial contamination of eastern China after ADS. Among these, Bacillus and Ralstonia might became the representative populations in the LRT events of Taiwan.
This study investigating quantification, biodiversity and community composition of ambient bacteria simultaneously, it demonstrated that the increase in bacterial abundance due to species multiplication, and these populations can have adverse effects on human health. As such, people should pay particular attention to the outdoor air quality in winter, and should also avoid outdoor activities during LRT events, and even up to two days after such events in northern Taiwan, regardless of whether being in rural or urban areas.
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