【作者】 李辉；

【导师】 武艳；

【作者基本信息】 山东大学 ， 环境工程（专业学位）， 2024， 硕士

【摘要】 空气中的颗粒物对人体和环境具有重要意义。其中,可吸入细颗粒物由于粒径较小、比表面积较大、吸附性较强,能够在大气中长时间的停留,这些颗粒物易成为空气中硫氧化物、氮氧化物、重金属离子等污染物的载体,载有不同污染物的颗粒物如被人呼吸摄入,可引起负面健康效应。例如,可吸入颗粒物中的水溶性成分可以影响肺部细胞的生长,而重金属离子可渗透进血管或其他器官引发健康风险。可吸入颗粒物通过呼吸暴露可引发呼吸系统、神经系统疾病,甚至加重癌症的风险。因此,揭示可吸入颗粒物的来源和生成机制,有助于从源头上防止颗粒物的生成,对保护环境健康和人体健康具有重要的意义。本文基于自行设计固气交换暴露舱,从固-气两相介质界面颗粒释放迁移视角,揭示了枕头形变导致的固体表面源颗粒物和生物气溶胶释放特征,并揭示影响固体表面源颗粒物释放到空气的关键因素。具体来说,本研究开展了四个方面的工作:(1)通过固气交换暴露舱在线监测不同种类枕头释放的颗粒物粒径和浓度的时空变化;(2)通过生物气溶胶采集与培养揭示不同体系释放的可培养细菌的数量浓度特征,利用高通量测序等分子生物学技术揭示枕头表面和环境空气中微生物的群落组成特征;(3)通过二区域物料平衡模型计算颗粒物再悬浮率、排放率、可吸入分数、传输效率等;(4)通过表面粘附力模型和空气动力学方程推算颗粒物从表面的分离机制和在空气中的运动轨迹方程。本研究选取了五种不同的枕头材料,包括羽绒、乳胶、PP棉、记忆海绵、荞麦。研究结果显示,枕头形变会导致大量的颗粒物和生物气溶胶释放到周围环境空气中。其中0.5μm的颗粒物数浓度由106 N/m~3增至108 N/m~3,生物气溶胶浓度增大两个数量级,以枕头为中心的1 m~3空间内均监测到了高浓度的可吸入颗粒物。在本研究选择的五种枕头中,回弹性最高的羽绒枕拥有最强的释放颗粒物的能力,荞麦枕最低。本论文发现枕头回弹性、枕头高度、枕头表面颗粒物负荷、外力强度等均可以影响形变释放的颗粒物浓度和粒径分布。在这些因素中,枕头表面颗粒物负荷量与颗粒物的再悬浮率无关,其余因素均和颗粒物再悬浮率呈正相关。本研究以再悬浮率、可吸入分数、传输效率作为量化颗粒物再悬浮情况的参数,其中粒径较大的颗粒物有较高的再悬浮率和传输效率,这表明粒径较大的颗粒物更容易从固体表面释放。可吸入分数在1-2.5μm处出现了峰值,达到4.5× 10~3 ppm,这表明,此粒径段的颗粒物有更大的被吸入可能性。通过运动方程和粘附力模型的推算,本研究发现外力强度、表面粗糙度、粒子粒径大小等,均可影响固体表面颗粒物的再悬浮行为以及悬浮后的运动轨迹。此外,本论文还发现枕头表面上存在大量的微生物,经枕头形变后可被释放到环境空气中,而且释放的微生物气溶胶仍具有活性和可培养性。从枕头表面释放的微生物在环境空气中可迁移不同距离,其中在水平方向上的扩散呈浓度随距离递减的趋势,而在垂直方向上在9-18 cm处出现浓度峰值。另外,基于高通量测序,本研究发现释放的具有活性的微生物主要以厚壁菌门(Firmicutes)和变形杆菌门(Proteobacteria)为主。本研究检测到的金黄色葡萄球菌、幽门杆菌、大肠杆菌、克雷伯氏菌均是机会致病菌。本研究揭示了固气两相介质界面颗粒物释放迁移情况及特征,揭示了颗粒物的释放机理并解释了影响机制,揭示了颗粒物的运动轨迹和潜在的健康风险。本研究有助于减少固体表面源颗粒物的释放,降低人体呼吸、接触暴露风险。更多还原

【Abstract】 Particulate matter in the air is of great significance to human body and environment.Among them,due to its small particles size,large specific surface area and strong adsorption,inhalable fine particulate matter can stay in the atmosphere for a long time and easily become the carrier of pollutants such as sulfur oxides,nitrogen oxides and heavy metal ions in the air.Meanwhile,inhalable particles containing different pollutants can cause negative health effects if ingested by human respiration.For example,the water-soluble components in inhalable particles can affect the growth of lung cells,while heavy metal ions can penetrate into blood vessels or other organs to cause health risks,and inhalable particles can cause respiratory and neurological diseases through respiratory exposure,and even increase the risk of cancer.Therefore,revealing the source and generation mechanism of inhalable particulate matter is helpful to prevent the generation of particulate matter from the source,which is of great significance to protect environmental health and human health.In this paper,based on the self-designed solid-gas exchange exposure chamber,the release characteristics of solid surface source particles and bioaerosol caused by pillow deformation were revealed from the perspective of particles release and migration at the interface of solid-gas two-phase media,and the key factors affecting the release of solid surface source particles into the air were also revealed.Specifically,this study carried out four aspects of work:(1)The spatial and temporal changes of particles size and concentration released by different kinds of pillows were monitored online by the solid-gas exchange exposure chamber;(2)The quantity and concentration characteristics of culturable bacteria released by different systems were revealed through bioaerosol collection and cultivation,and the community composition characteristics of microorganisms in pillow surface and ambient air were revealed by molecular biology techniques,such as high-throughput sequencing;(3)The particles resuspension rate,emission rate,inhalable fraction and transmission efficiency were calculated by the two-zone material balance model;(4)The separation mechanism of particulate matter from the surface and the motion trajectory equation in the air are calculated by the surface adhesion model and the aerodynamic equation.In this study,five different pillow materials were selected,including down,latex,PP cotton,memory sponge,buckwheat.The results showed that the deformation of the pillow would lead to the release of a large number of particles and bioaerosols into the ambient air,in which the concentration of 0.5 μm particles increased from 106 N/m~3 to 108 N/m~3,and the concentration of bioaerosol increased by two orders of magnitude.Meanwhile,high concentrations of inhalable particles were detected in the 1 m~3 space centered on the pillow.Among the five pillows selected in this study,the down pillow with the highest resilience possesses the strongest ability to release particulate matter,while the buckwheat pillow possesses the lowest ability.In this paper,it is found that pillow resilience,pillow height,pillow surface particles load and external force intensity can affect the particles concentration and particles size distribution.Among these factors.the particles load on the pillow surface has nothing to do with the particles resuspension rate,while the other factors are positively correlated with the particles resuspension rate.In this study,the resuscitation rate,inhalable fraction and transport efficiency were used as parameters to quantify the resuspension of particulate matter.Among them,the particles with larger particles size had higher resuscitation rate and transport efficiency,indicating that the particles with larger particles size were more easily released from the solid surface.The inhalable fraction peaked at 1-2.5 μm,reaching 4.5 × 10~3 ppm,indicating that particles in this particles size range have a greater possibility of human inhalation.Through the calculation of motion equation and adhesion model,it is found that external force intensity,surface roughness,particles size,etc.can affect the resuspension behavior of solid surface particles and the motion trajectory after suspension.In addition,the paper also found that there are a large number of microorganisms on the surface of the pillow and in the ambient air,which can be released into the ambient air after the deformation of the pillow,and the released microbial aerosol is still active and cultivable.The microorganisms released from the pillow surface can migrate different distances in the ambient air,in which the horizontal diffusion shows a trend of decreasing concentration with distance,and in the vertical direction,the concentration peaks at 9-18 cm.In addition,based on high-throughput sequencing,this study found that the active microorganisms released were mainly Firmicutes and Proteobacteria.Among them,Staphylococcus aureus,Helicobacter pylori,Escherichia coli and Klebsiella are opportunistic pathogens.In this study,the emission and migration of particulate matter at the interface of solid and gas two-phase media were revealed,the release mechanism of particulate matter was also revealed,the influencing mechanism was explained,and the movement trajectory and potential health risks of particulate matter were obtained.It is of great significance to reduce the release of particulate matter from solid surface sources,reduce the risk of human respiration and exposure.更多还原