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

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.