You are here:
EAST VERSUS WEST IN THE US: CHEMICAL CHARACTERISTICS OF PM 2.5 DURING THE WINTER OF 1999
Citation:
Tolocka, M P., P A. Solomon, W J. Mitchell, G A. Norris, D B. Gemmill, R W. Wiener, R. W. Vanderpool, J. P. Homolya, AND J. Rice. EAST VERSUS WEST IN THE US: CHEMICAL CHARACTERISTICS OF PM 2.5 DURING THE WINTER OF 1999. AEROSOL SCIENCE AND TECHNOLOGY 34(1):88-96, (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:
The chemical composition of PM2.5 was investigated at four sites (Rubidoux, CA, Phoenix, AZ, Philadelphia, PA, and RTP, NC) in January and February of 1999. Three samplers were used to determine both the overall mass and the chemical composition of the aerosol. Teflon filters were weighed for total mass. Ions were analyzed using ion chromatography. Elements were determined using X-Ray fluorescence. Organic and elemental carbon were measured using a thermo-optical method. At all of the sites, reconstructed mass was observed to be greater than or equal to the measured mass. Good ionic balance was found for ammonium, nitrate and sulfate at each of the sites. Overall, the chemical composition of the aerosol for each site was in good agreement with the expected composition based upon previous studies, with the exception of relatively high nitrate contribution to the total mass at Philadelphia. Good agreement was found between the predicted amount of sulfate by XRF analysis of sulfur and the sulfate measured by ion chromatography. As expected, sulfate was a more important contributor to the total mass at the East Coast sites. Nitrate contributed more to the total mass at the west coast sites and was an important factor in the highest observed mass concentration at Rubidoux. Teflon filters appear to lose nitrate to a greater extent than heat-treated quartz fiber filters. Organic carbon was also found to be the largest part of the aerosol mass on minimum days for all sites and a significant portion of the mass on other days with 25-50% of the total mass at all of the sites. At three of the sites, OC collected on denuded filters was less than that found on non-denuded samples, indicating an absorptive artifact on the quartz fiber filters. It was also found that the crustal component to PM2.5 was highest at Phoenix. PM2.5 was also found to contribute significantly to the PM10 particle mass at all the sites.
This work has been funded wholly or in part by the United States Environmental Protection Agency. Portions of the work were performed under contract no. 68-D5-0040 by Research Triangle Institute. It has been subjected to Agency review and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.