The effect of environmental wind orientations on aerosol sampling results - from the aspect of aspiration efficiencies of aerosol samplers

• Main Authors: Wu Yi Hsuan, 吳怡萱
• Other Authors: Tsai Perng Jy
• Format: Others
• Language: en_US
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/31610035809247013394

碩士 === 國立成功大學 === 環境醫學研究所 === 87 === In this study, the sampling results obtained from the mixing area of a refractory brick manufacturing plant are used to explain the effects of aspiration efficiencies of samplers on the aerosol sampling results and the size distribution sampling. In the first part of this study, aspiration efficiency predictive models were used to estimate the aspiration efficiencies of human heads theoretically, and examine the performances of IOM personal inhalable sampler and 37-mm cassette personal sampler. The results show that under no circumstance the 37-mm sampler could be regarded as inhalable aerosol samplers. Under low wind speed situations (￡ 2m/s), the performance of IOM personal sampler falls within the tolerance bands of the aspiration efficiencies of human heads at the orientation-averaged situation. However, for wind speed at 4m/s, the performance of IOM sampler can not be the representative sampler to collect inhalable aerosol at the orientation-averaged situation. And the Andersen-collected aerosol size distributions obtained from the workplace are found to be non-significant different in term of MMAD and σg as tested by using the multisample median test and Bartlett's test, respectively. The obtained Andersen-collected size distribution, is theoretically further transferred into the size distributions of "true total aerosol" of the workplace atmosphere, IOM inhalable sampler collected, and 37-mm filter cassette collected aerosols via the uses of the aspiration efficiency predictive models. The result shows that the Andersen-collected size distribution is not suitable to be representative to the environmental size distribution. The second part of this study suggests that the ratio of collected amounts for 37-mm sampler versus IOM cassette would be 0.72 as estimated by using theoretical computations, instead of 0.37 which was directly obtained from the 17 pairs sampling data. The discrepancy as shown above is considered due to the orientations of sampled workers with respect to the wind might not be orientation-averaged as assumed in the theoretical computations, and also the wall-loss of 37-mm sampler. Obviously, the collected aerosols by different samplers are not only affected by the existing aerosol size distribution, but also by wind speed and orientation of aerosol samplers. It is concluded that inhalable aerosol sampling criterion should not only consider orientation-averaged condition, but also should take sampler's orientations and wind speeds into account in the future. In addition, the prevention of wall-loss needs to be taken into consideration on the future sampler developments.