Performance Test Of Virtual Cyclone Bioaerosol Sampler

Bioaerosol refers to particles produced by biological sources and suspended in the air.Exposures to bioaerosols can lead to a wide variety of health problems.Bioaerosols are widely distributed in both indoor and outdoor environments.Different kinds of bioaerosols in different environments have different effects on human beings.Besides,biological particles can affect the climate as cloud condensation nuclei or ice core.Monitoring is an important way to understand changes and distributions of those biological particles.It can help us to understand how the air quality and climate affected by it.Highly effective bioaerosol sampler is the key to bioaerosol monitoring.Currently,bioaerosol samplers can be divided into four categories,which are filters,impactors(cyclones),liquid impingers and electrostatic samplers.None of these samplers can be used for all circumstances.It is still of practical significance to develop new efficient samplers which can improve the culturability of collected microorganisms.Therefore,in this study,we established a bioaerosol sampler test system to evaluate the performance of virtual cyclone with different designs.Both physical collection efficiency and biological efficiency of virtual cyclone bioaerosol sampler were tested.In addition,efforts were made to observe the resuspension phenomenon.Finally,virtual cyclone was compared with a commercial bioaerosol sampler in field sampling.The major findings include:(1)Bioaerosols with different size distribution could be generated with bacterial fluid of different concentrations and at various generation pressures.In this study,most Escherichia.coli aerosols were between 0.5-1.0μm in diameter,and 0.7-1.3μm,2.6-3.2μm for Bacillus.subtilis vegetative cells and Aspergillus.niger Spores.(2)Decrease in inlet size and increase in radius of curvature could lead to higher physical collection efficiency,but effect of flow rate was more significant.Liquid in the chamber of virtual cyclone bioaerosol sampler did not affect its physical collection efficiency.After sampling for a relatively long time,no obvious loss of sampling fluid was observed,suggesting that virtual cyclone bioaerosol sampler might be suitable for long time sampling.It was difficult for particles in the liquid to resuspend,which suggests virtual cyclone sampler can avoid the resuspension effect of particles to a certain degree.(3)Biological efficiency of virtual cyclone bioaerosol sampler towards Escherichia.coli(ATCC 8739)aerosols was slightly higher than that of biosampler.(4)In most cases of field tests,there were no significant differences between the results obtained by the two samplers.The results of virtual cyclone were similar to each other in parallel tests.But in some cases,the concentration of bacteria obtained by virtual cyclone bioaerosol sampler is significantly lower than that of biosampler.(5)In tests with different sampling time,the bacteria and fungi concentration measured by virtual cyclone bioaerosol sampler and biosampler,are similar.Variation in sampling time could result in different concentrations.