Research On Key Technologies Of Cyclonic Bioaerosol Collection

Aims:Bioaerosols include small biological particles such as bacteria,viruses,fungi etc.with a size ranging from 0.01 to 100 ?m.These particles can spread through the air and enter the human respiratory system to cause various respiratory diseases and to harm human health.A high-efficiency bioaerosol sampler is a necessary tool to capture these pathogenic microbial particles,and can effectively ensure the biological viability of the microbes for further biological analysis.This thesis mainly focuses on the problems in the application of the cyclonic bioaerosol sampler.The key parameters of the sampler were designed and optimized to improve the sampling efficiency and to evaluate the sampler in an indoor environment.Methods and studies:The research is mainly carried out in the following aspects:(1)A prototype cyclonic bioaerosol sampler was used to collect air samples from seven different functional areas in Beijing,Hangzhou and Wuhan.The result were statistically analyzed for different species types,functional areas,and meteorological factors.In view of the issues of the prototype cyclonic bioaerosol sampler,the optimization of the core components of the sampler should be considered to improve the sampling efficiency.The sampler parameters were not explicit optimized,the sampler had low sampling efficiency,which may lead to poor sample collection quality and low positive detection rate.According to the problems of the prototype,the optimization of the core components of the sampler should be considered in the further research to improve the sampling efficiency.At the same time,the influence of environmental factors on the sampling efficiency should be considered,and the experimental evaluation of sampling efficiency in different application scenarios such as closed cabin and indoor area should be increased.(2)According to the sampling efficiency problem of cyclone sampler prototype,a method of computing fluid dynamic simulation and orthogonal design was proposed to calculate the particle path and capture efficiency,and then optimized the core components of the sampler and improve the sampling efficiency.The core components of the cyclonic bioaerosol sampler included the jet angle of the inlet nozzle,the distance between the air nozzle and the collection liquid surface,the shape of the collection cup,and the aerosol particle size.These performance-parameters were analyzed and optimized.The orthogonal experiment was carried out and showed the best combination of parameters for a bioaerosol sampler according to the orthogonal experimental analysis and the influencing order of factors.(3)Based on the results of computing fluid dynamic simulation,the prototype was optimized,improved,and developed.An optimized and improved cyclonic bioaerosol sampler was developed and tested in an aerosol generating chamber for a comparative study of sampling efficiency.In the bioaerosol chamber,the sampling efficiency comparison test was carried out on five biosamplers including the prototype cyclone,the improved prototype cyclone,the impingers SKC,AGI-30 and the impactor Anderson six-stage sampler.Serratia marcescens was used as the test microorganism to conduct comparative tests with different concentrations and sampling times.The reuslt collected by the Anderson six-stage sampler was used as a control,and bacterial concentration from other samplers was divided by that to obtain the relative sampling efficiency ratio.The statistical results showed that the optimized cyclonic bioaerosol sampler has a better sampling efficiency than the prototype in the aerosol chamber(p <0.05).(4)The optimized prototype cyclonic bioaerosol sampler,SKC impinger and Anderson six-stage impactor were applied at the international departure level of Daxing International Airport once a week in a year.Further study was to evaluate the sampling efficiency of the improved cyclonic bioaerosol sampler in an indoor environment of Daxing International Airport.The results showed that the improved cyclonic sampler with high flow rate has a better relative sampling efficiency compared with SKC sampler(p = 0.008).Moreover,there was a correlation of the variation in microbial concentration between the improved sampler and the SKC sampler(p = 0.018).Analysis of the annual monitoring data showed that there was no correlation between the annual flow of people,temperature and humidity and the microbial concentration collected by each sampler(p > 0.05).Also,the nucleic acid test was performed on samples collected by different bioaerosol samplers to detect influenza A virus,influenza B virus,respiratory syncytial virus,adenovirus,enteric general virus,human metapneumovirus.Innovation and Conclusion:In the aspect of cyclonic bioaerosol collection research,this thesis summarizes the problems existing in the sampling experiment and makes theoretical and practical optimization aiming at improving the collection efficiency.On the basis of prototype,a new cyclonic sampler was developed,and the following innovation points and technical difficulties are summarized:(1)The method of combining orthogonal experimental design with computational fluid dynamic simulation was proposed for the first time to carry out theoretical simulation research on the prototype of cyclonic bioaerosol sampler.The key technical parameters and component structure with the highest sampling efficiency were optimized.Including: geometry: inverted cone,distance: 10 mm,and angle: 45°.(2)The optimized sampler was tested in the laboratory aerosol generating chamber with different concentrations to verify the reliability and scientificity of the design by theoretical simulation analysis.The experimental test conclusion: compared with the prototype,the improved model significantly improved the relative sampling efficiency(p < 0.05).In addition,the relative sampling efficiency of the improved prototype was higher than that of the SKC sampler(p = 0.008),and there was a correlation between the microbial concentration changing trend of the two samplers(p = 0.018),which indicated that the improved cyclonic sampler having a promising application prospect.In the research of bioaerosol collection,the cyclonic bioaerosol sampling is closely related to the major needs of the national biosafety.The sampling efficiency and microbial concentration of the improved cyclonic bioaerosol sampler have been significantly improved compared with the prototype.In the field environment,the improved cyclonic bioaerosol sampler has higher sampling efficiency than other samplers and has a wider application prospect.In further research,it is possible to explore and analyze the influence of various environmental factors in different applied scenarios,to continuously verify the feedback design,and to combine the optimization of the principle and mechanics of the cyclonic bioaerosol sampler to further improve the overall sampling efficiency.