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METHODOLOGY FOR MEASURING PM 2.5 SEPARATOR CHARACTERISTICS USING AN AEROSIZER
Citation:
Peters, T., R. W. Vanderpool, AND R W. Wiener. METHODOLOGY FOR MEASURING PM 2.5 SEPARATOR CHARACTERISTICS USING AN AEROSIZER. AEROSOL SCIENCE AND TECHNOLOGY 34(5):398-406, (2001).
Impact/Purpose:
The core aerosol research for FY01 includes evaluation of newly developed and developing methods for the chemical analysis and sampling of PM in ambient air, especially state-of-the-art continuous and non-invasive aerosol measurement methods, and the study of the aerosol sampling processes to better assess the true aerosol concentration and size distributions observed in the ambient environment. An additional emphasis is placed on integrated sampling for stable and semi-volatile organic aerosol species. This latter area addresses the state-of-the-art in this measurement area. This program supports Title I of the Clean Air Act in its mandate for performing research to support the NAAQS, GPRA goal 1.1.5, and ORD's main research objective on PM.
Much of this work directly supports OAQPS and may be applied within the Supersites Program managed jointly by OAQPS and ORD. This research also will support many of ORD's long-term research goals by providing more reliable information (decrease uncertainty) on ambient aerosols that can be utilized for characterizing risk.
Finally, an APM, has been established to develop measurement methods for causal factors, due in 2004. Currently, there are a number of causal factor hypotheses, but none have sufficient evidence to support developing one measurement/analytical method over another. The PM methods team will support and work with Joellen Lewtas on methods for the collection and analysis of semi-volatile and aerosol phase organic species to help address this APM. The PM methods team will continue to work within the Supersites program and with OAQPS and their new partners in ORIA to further evaluate continuous species specific methods and aerosol physical property measurement methods.
Description:
A method is presented that enables the measurement of the particle size separation characteristics of an inertial separator in a rapid fashion. Overall penetration is determined for discrete particle sizes using an Aerosizer (Model LD, TSI, Incorporated, Particle Instruments/Amherst, Amherst, MA) time-of-flight measurement device by comparing the number concentration of particles penetrating through a separator to that concentration entering the separator. Critical measurements of separator characteristics are determined using a vibrating orifice aerosol generator to produce the challenge aerosol. Measurements of penetration requiring less precision and accuracy may be determined using nebulized suspensions of polystyrene latex microspheres as the challenge aerosol. The time for measuring a single penetration curve can be reduced from on the order of a week using vibrating orifice aerosol to fewer than two hours using polystyrene latex microsphere aerosol. Validation of the penetration determined with this method was made by comparison to fluorometric techniques. It is estimated that penetration may be measured to an accuracy of plus/minus 4% which is equivalent to an uncertainty of approximately 0.04 um in cutpoint diameter determination for PM2.5 separators. The overall accuracy in determining a cutpoint diameter of a PM2.5 separator (including uncertainty in the creation of test aerosols) is estimated to be better than plus/minus 0.09 um.
This work was conducted by Research Triangle Institute with support provided by the U.S. Environmental Protection Agency through contract no. 68-D5-0040. It has been reviewed in accordance with the Agency's peer and administrative review policies and approved for presentation and publication. Mention of trade names or commercial products does not constitute endorsement or recommendation by RTI or the Agency.