【作者】 张越；

【导师】 向荣彪；

【作者基本信息】 华中农业大学 ， 环境工程， 2017， 硕士

【摘要】 生物气溶胶指由生物来源产生并悬浮于空气中的颗粒物,对生物气溶胶的接触和吸入会导致多种多样的健康问题。生物气溶胶在室内及室外环境均有广泛的分布,不同环境中的生物气溶胶种类不同,对人造成的影响也不同。除此以外,生物气溶胶可以作为云凝结核以及冰核等,对全球气候变化造成影响。对于生物气溶胶的监测是了解其变化及分布规律的重要手段,有助于理解其对空气质量以及气候变化的影响方式。监测的基础是高效的生物气溶胶采样器。目前常用的生物气溶胶采样器包括过滤式、撞击式、液体冲击式以及静电式等,但这些采样器都有一定的适用范围。开展效率稳定且对微生物伤害较小的生物气溶胶采样器的研究在目前仍然具有重要现实意义。因此,本研究构建了生物气溶胶采样器实验室测试系统,利用该测试系统考察了设计参数对虚旋风生物气溶胶采样器物理效率的影响,并进行了再悬浮性能测试、生物效率测试、野外采样测试等,最后与市售采样器Biosampler进行了比较,主要结论如下:(1)改变生物气溶胶发生器中菌液的浓度及发生压强会产生具有不同粒径分布的生物气溶胶,多数大肠杆菌气溶胶处于粒径0.5-1.0μm的范围之间,多数枯草芽孢杆菌营养细胞处于粒径0.7-1.3μm的范围之间,多数黑曲霉孢子处于粒径2.6-3.2μm的范围之间。(2)进口尺寸的减小、曲率半径的增大有利于提高采样器物理效率,但均不如流量的影响显著;在虚旋风生物气溶胶采样器的空腔中加入一定体积的采样液作为捕集介质不会影响采样器的物理效率,且长时间采样后采样液的挥发率仍然比较低;已经捕集到液体中的颗粒物再次悬浮较为困难,可在一定程度上避免颗粒物再悬浮的现象。(3)对于压力敏感性细菌大肠杆菌(ATCC 8739),虚旋风生物气溶胶采样器的生物效率略高于市售采样器Biosampler。(4)实地测试中,虚旋风生物气溶胶采样器与Biosampler在多数情况下的结果均较为相近,没有显著差异,且虚旋风生物气溶胶采样器在多次平行测试之间的差异较小,采样结果较为稳定,然而在某些情况下虚旋风生物气溶胶采样器测得的细菌浓度显著低于Biosampler。(5)在不同的采样时间下,虚旋风生物气溶胶采样器和Biosampler所得的细菌和真菌浓度均值均较为接近,但都会随着采样时间的变化而变化。更多还原

【Abstract】 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.更多还原