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OPTIMIZATION OF THE WASH-OFF METHOD FOR MEASURING AEROSOL CONCENTRATIONS
Citation:
Tolocka, M P., P. T. Tseng, AND R W. Wiener. OPTIMIZATION OF THE WASH-OFF METHOD FOR MEASURING AEROSOL CONCENTRATIONS. AEROSOL SCIENCE AND TECHNOLOGY 34(5):416-421, (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:
Using the fluorescence-washing technique, oleic acid particles tagged with uranine were extracted and analyzed fluorometrically. The possible sources of errors in the technique were evaluated in this study. First, the sensitivity of uranine fluorescence in different solutions was compared. The results indicated that uranine in distilled water with pH 10 buffer and in sodium hydroxide have high sensitivity. Second, the interference of oleic acid with uranine quantification in a variety of media was investigated. It was found that there is no interference from oleic acid in distilled water and sodium hydroxide solutions under our operating conditions. However, oleic acid did significantly quench the uranine fluorescence signal in ethanol. Third, the ability of different solutions to extract uranine from glass fiber and TeflonO filters was tested. The results indicated that distilled water and sodium hydroxide solutions have the highest extraction ability of the media evaluated. Based on the results above, distilled water, 0.001
N sodium hydroxide, and 0.01 N sodium hydroxide solutions were the optimal washing solutions in the fluorescence-washing technique. It was also found that, for inlet washes, distilled water would not be reactive and have high extraction efficiency.