248 Abstracts

INTERSAMPLER COMPARISON AND FIELD APPLICATION OF A PM10 PERSONAL ENVIRONMENTAL MONITOR

Man-Ting Cheng. Ying-I Tsai and Ming-Shiunn Chang

Department of Environmental Engineering, National Chung Hsing University, Taichung, Taiwan, 40227, R.O.C.

A personal environmental monitor (PEM) was used to characterize the ambient aerosols at various altitudes. To evaluate the applicability of the personal sampler in the ambient measurement, the sampler was run side by side with an established dichotomous sampler and a microorifice uniform deposit impactor (MOUDI). Four miniature PEM were then used to measure the PM,,, concentration at various altitudes. The elemental analyses of the samples were also conducted by using a microwave digestion technique and an inductively coupled plasma-mass spectrometry. The following results were obtained: (1) All the experiments were conducted outdoor with wind speed less than 3 m s ’ and the PM,o concentration less than 186 ngm-“. The effect of wind direction on the inlet loss of the samplers was found insignificant. By maintaining a constant flor rate of the PEM and avoiding the particle bouncing on the impaction plate of the PEM, the PEM precision was obtained with a coefficient of variation between 1.3% and 5.8%. As the variation in the directions of the sampler inlets was considered, the average coefficient of variation was only 5.8%. (2) The PM,e sampled by the PEM was found to be well correlated with measurements obtained by the dichotomous sampler (7, = 0.983) and the MOUDI (yz = 0.972). The differences between these measurements were less than 13%. (3) On testing the hypothesis. the results indicated that the PMio concentration sampled at 2, 13 and 20 m above the ground decreased with latitude. The confidence level of this result was 95’/u. (4) Pb and Fe concentrations of PM,o also decrease with altitude which would be indicative of ground level sources. The decrease of Mn with altitudes was not significant which may indicate the source from the ambient environment.

RESEARCH ON THE COLLECTION EFFICIENCY OF A PERSONAL RESPIRABLE DUST SAMPLER

Horng-Guang Shiau,” Kuo-Ching Lin ,* Chuen-Jinn Tsai* and Tung-Sheng Shiht

*Institute of Environmental Engineering, National Chiao Tung University, Hsinchu, Taiwan ’ Institute of Occupational Safety and Health. Council of Labor Affairs, Taipei, Taiwan, R.0.C

The IO mm nylon cyclone is commonly used as a respirable dust sampler. Effect of particle mass loading and particle electrostatics on particle collection efficiency is still significant. The cyclone has a short distance between its inlet and the opposite wall of the inlet. The inlet velocity is as high as 580 cm s ’ at the flow rate of 1.7 I min _ ‘. For this reason, the initial collection efficiency of large particles is low due to particle rebound near the opposite wall of the inlet. However. as particles accumulate on the inner wall, the collection efficiency will start to increase. As to the effect of particle electrostatics, the collection efliciency of charged particles is usually higher than uncharged particles because nylon is a non-conductive material. In this study, an aerodynamic particle sizer and aerosol electrometer is used to measure the size and charge of the test aerosol generated by a vibrating orifice mono- disperse aerosol generator.

PERFORMANCE EVALUATION OF AN API AEROSIZER

Chuen Jin Tsai,* Hung Min Chein,+ Shu Ting Chang” and Jong Yoh Kuo:

*Institute of Environmental Engineering, National Chiao Tung University, No. 75, Poai St., Hsin Chu ’ Center for Industrial Safety and Health Technology, Industrial Technology Research Institute. Hsin Chu

r Institute of Aeronautics and Astronautics, National Cheng Kung University, Tainan, Taiwan

A numerical method was developed to simulate the supersonic Bow field and particle trajectory in an API Aerosizer. Experimental particle time-of-flight (TOF) data using monodisperse solid and liquid particles were also obtained. Theoretical particle TOF results were compared with the present experimental data and those of Cheng et al. Good agreement was found for solid particles. The original TOF calibration curve for the API Aerosizer was found to overestimate the experimental data mainly because of incorrect use of the particle drag coefficient in the supersonic flow field. For large particles, significant effects of inlet conditions on TOF was found. Liquid particles were found to have shorter TOF than solid particles of equal aerodynamic diameter. It is speculated that more deformation of liquid particles occurred in the API Aerosizer than in the TSI APS.