Abstract
Inhalation of aerosol particles and their adverse health effect has been well studies in past decades. However, efficient sampling techniques to allow high temporal resolution sampling are limited to collect and study PM in various occupational and ambient micro–environmental atmospheres. Effective control of PM adverse health effects requires knowledge about aerosol sources through analyzing their chemical composition. Improved particle sampling techniques are needed to counter the disadvantages of traditional filter sampling and the limitations of those currently available.In this study, a Swirling Aerosol Sampler (SAS) was developed initially as a prototype sampler, which later became the collector of Aerosol to Hydrosol Air Sampler (ATHAS). The SAS is a medium flow swirling bioaerosol sampler that collects atmospheric bioaerosols at the flow rate of 167 LPM (10 cubic meters per hour). The collection of bioaerosols is achieved through a combination of impaction and cyclonic centrifugal motion. Aerosol deposition efficiency tests were performed with monodispersive polystyrene latex (PSL) particles ranging from 0.1 to 10μm. Results have shown that the sampler has the cut-off size of 0.7μm and 1.5μm, with and without the assistance of added water vapor, respectively. The bioaerosol collection and viability tests were performed with comparison to the commercially-available BioSampler, and the results show that the collection efficiency of the SAS is 97% at the designed flow rate, while the higher flow of the new system yields more than 13 times of the collection rate compared to the Biosampler.
Aerosol to Hydrosol Air Sampler (ATHAS) consists principally of a steam generator, condenser and collector. It collects particles at the flow rate of 50 liters per minute through condensational growth followed by particle-containing droplets collection of combined impaction and centrifugal flow. Monodisperse polystyrene latex (PSL) particles ranging in size from 0.1 μm to 2 μm were used to test the performance of size dependent collection at the extreme condition of highly hydrophobic aerosols. Results show that the sampler has near 90-100% collection efficiency for supermicron PSL particles, and 65% and 50% for 0.5 and 0.1 μm particles, respectively. NaCl collection efficiency tests showed that the sampler has over 95% collection efficiency for soluble aerosols. The medium size and sampling flow make it suitable for field deployment with high potential for semi-continuous online chemical analysis.
Three types of field experiments have been performed for the application of the Aerosol to Hydrosol Sampler (ATHAS). First is the ambient air sampling in high time resolution and chemical analysis for trace metal concentration. Second is the sampling of nano-sized organic carbon particles and analysis using Transmission Electron Microscopy (TEM). Third is the PM-induced reactive oxygen species and cell toxicity experiment. Results from the first experiment produced 3-hour time integrated metals concentration of ambient aerosols, together with a comparison with results from a recent study carried out in the same area as the reference. A good recovery of the trace metals in ambient particles was demonstrated for the two sets of 3- hour samples from different days. Although the reference data were sampled at different time intervals, a consistent relative abundance of the metals was clear indicating the feasibility of the sampler for high time resolution sampling and metal analysis. Images from Transmission Electron Microscopy showed that the ATHAS collected liquid sample contains nano-sized organic carbon particles with size ranging from 2-3 nm, which is not possible to collect using traditional filter sampling method. PM-induced ROS and cell toxicity experiment results showed that the ATHAS collected PM sample induce much higher ROS activity compared to filter sampling. It indicates that the developed Aerosol to Hydrosol Air Sampler is a better alternative for efficient PM sampling.
| Date of Award | 4 May 2016 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Zhi NING (Supervisor) |