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LABORATORY AND FIELD EVALUATION OF CRYSTALLIZED DOW 704 OIL ON THE PERFORMANCE OF THE WINS PM2.5 FRACTIONATOR
Citation:
Vanderpool, R, L. Byrd, R W. Wiener, E. Hunike, M. Labickas, A. Leston, M. Tolocka, F. McElroy, R. Murdoch, S. Natarajan, AND C. A. Noble. LABORATORY AND FIELD EVALUATION OF CRYSTALLIZED DOW 704 OIL ON THE PERFORMANCE OF THE WINS PM2.5 FRACTIONATOR. Presented at Symposium on Air Quality Measurement Methods and Technology - 2004, Research Triangle Park, NC, April 20-22, 2004.
Impact/Purpose:
Develop and evaluate methods for the sampling and analysis of PM in ambient air, with emphasis on FRM/FEM for PMc, measurement of carbonaceous aerosols, measurement of biogenic aerosols, comparisons measurements from the STN and IMPROVE monitoring networks, and continuous methods for PM mass and its chemical components.
Description:
Subsequent to the 1997 promulgation of the Federal Reference Method (FRM) for monitoring PM2.5 in ambient air, the United States Environmental Protection Agency (USEPA) received reports that the Dow 704 diffusion oil used in the method's WINS fractionator would occasionally crystallize during field use - particularly under wintertime conditions. While the USEPA's survey of site operators revealed that the frequency of occurrence on a nationwide basis was low, concerns were raised that crystallization of the Dow 704 oil during a given sampling event may adversely affect the event's data quality due to possible particle bounce from the crystallized impaction surface.
In response to these concerns, the USEPA and the Connecticut Department of Environmental Protection (CT DEP) jointly conducted a series of specialized tests to determine if crystallized oil adversely affected the performance of the WINS fractionator. In the laboratory, an experimental setup used dry ice to artificially induce crystallization of the diffusion oil under controlled conditions. Using primary calibration aerosols, standard size-selective performance tests of the WINS fractionator showed that neither the position nor the shape of the WINS particle size fractionation curve was substantially influenced by the crystallization of the Dow 704 oil. No large particle bounce from the crystallized impaction surface was observed.
Wintertime field tests were then conducted in Windsor, CT using collocated FRMs equipped with both crystallized and non-crystallized oil. As predicted by results of the laboratory tests, crystallization of the Dow 704 oil did not adversely affect measured PM2.5 concentrations. In 32 collocated PM2.5 tests, regression of measurements with crystallized Dow 704 versus liquid dioctyl sebacate (DOS) oil produced slope, intercept, and R2 values of 0.98, 0.1 ug/m3, and 0.997, respectively.
In 45 additional collocated PM2.5 tests conducted at three U.S. cities, regression of liquid DOS versus liquid Dow 704 produced slope, intercept, and R2 values of 0.995, -0.006 ug/m3, and 0.999, respectively. As a result of these laboratory and field tests, DOS oil has been approved by the USEPA as a substitute for Dow 704 oil. Since the field deployment of DOS oil in 2001, users of this alternative oil have not reported any operational problems associated with its use in the PM2.5 FRM.
This paper has been reviewed in accordance with the United States Environmental Protection 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 the Agency.