Nitrate Artifacts during PM 25 Sampling in the South Coast Air Basin of California

• Published in: Journal of the Air & Waste Management Association (1995) 1999-09, Vol.49 (9), p.142-153
• Main Authors: Kim, Bong Mann, Lester, Julia, Tisopulos, Laki, Zeldin, Melvin D
• Format: Article
• Language: English
• ISSN: 1096-2247; 2162-2906
• DOI: 10.1080/10473289.1999.10463905

In February 1993, the South Coast Air Basin (SCAB) was redesignated as a "serious" nonattainment area for PM10. To improve the understanding and characterization of fine particulate matter in the SCAB, the South Coast Air Quality Management District (SCAQMD) initiated a comprehensive PM Technical Enhancement Program (PTEP). Using enhanced PTEP monitors (specially designed multichannel/multifilter samplers), a one-year fine particulate matter (PM) monitoring program was initiated in January 1995. As part of the special monitoring program, nitric acid, ammonia, and speciated PM and PM concentrations were measured at five locations in the SCAB (downtown Los Angeles, Anaheim, Diamond Bar, Fontana, and Rubidoux) and at one background station (San Nicolas Island). The PM2.5 data are the first spatially resolved speciated data collected in the SCAB on an annual basis. Within the SCAB, where nitrate is a major component of PM nitrate losses have been documented. The spatial and temporal variations of the nitrate losses during PM sampling and the uncertainties of the nitrate losses are discussed. Significant losses occur at a low mass range, between 10 and 50 ìg/m . Significant gains occur at an even lower mass range of less than 30 ìg/m . On an annual average basis, nitrate losses vary between 1.25 and 2.32 ìg/m and the SCAB-wide average value of nitrate loss is 1.8 ìg/m based on five PTEP stations in the SCAB. The maximum nitrate losses for each station vary from 6.4 ìg/m to 22.5 ìg/m . Theoretical prediction of the sampling efficiency of the nitrate during PM sam - pling was compared with the PTEP data. In general, theoretical prediction was in good agreement with measured values.