10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Improving the Accuracy of PM2.5 Sampling with Chilled Teflon Filter
Krishna Kumar Shukla, Sneha Gautum, Te-Hsien Hsieh, Ziyi Li, Pei-Yun Shih, THI-CUC LE, Chuen-Jinn Tsai, National Chiao Tung University, Taiwan
Abstract Number: 314 Working Group: Control and Mitigation
Abstract Most of the ambient aerosol sampling and monitoring devices use filter media to capture particles (such as PM2.5) after the size-selective pre-separators (such as well impactor ninety-six (WINS), or very sharp cut cyclone (VSCC)). Smart heaters are further used to condition the inlet aerosol temperature to avoid water vapor condensation in the aerosol monitors. Previous studies from our group (Liu et al., 2014) showed that the aerosol evaporation loss was occurred which reduced the aerosol mass concentration. An increment in the deviation was also observed with decreasing loaded particle mass and increasing ambient or conditioning temperature (Liu et al., 2015). The aim of the present study is to use a chilled filter sampler in which the aerosol stream before the filter holder was chilled to 4 0C after the aerosol was dried to a relative humidity (RH) of 24.5 ± 5.1% to improve the accuracy of PM2.5 sampling. The observed test results from the chilled filter sampler showed that the evaporation loss of volatile species was effectively suppressed. However, the gravimetric weights of chilled filter samples were slightly heavier than the normal filter samples, which were quantified by using hydrophobic test particles, due to slight increase in the remained water content in the former. A thin layer of condensed water coated on the sampling particles was the key to reduce the evaporation loss. After correcting the mass concentration of PM2.5 for the excess remained water content, the accuracy of PM2.5 sampling was greatly improved with the average positive bias reduced substantially from 15.2% to 2.6% for PM2.5 ranging from 10.6 to 44.5 µg/m3.
Liu, C.-N., Lin, S.-F., Tsai, C.-J., 2014. Sampling and Conditioning Artifacts of PM2.5 in Filter-based Samplers, Atmos. Environ., Vol. 85:48-63.
Liu, C.-N., Lin, S.-F., Tsai, C.-J., Wu, Y.-C., Chen, C.-F., 2015. Theoretical Model for the Evaporation Loss of PM2.5 during Filter Sampling, Atmos. Environ., Vol. 109:79-86.