A characterization of the principal PM-10 species in Claremont (summer) and Long Beach (fall) during SCAQS

Abstract

Abstract As part of the Southern California Air Quality Study (SCAQS), General Motors Research Laboratories made comprehensive air quality measurements during the summer of 1987 in Claremont, CA, and during the fall of 1987 in Long Beach, CA. These locations are typically in the areas of highest pollution for the respective seasons. Claremont's air quality during the summer was characterized by high concentrations of photochemically produced pollutants including ozone (O3), nitric acid (HNO3), particulate nitrate (NO3−) and particulate organic carbon (OC). The highest concentrations of these species were experienced during the daytime sampling period (0600–1800 h) and were associated with transport from the western part of the basin. Long Beach's air quality during the fall was characterized by frequent periods of air stagnation that resulted in high concentrations of primary pollutants including PM-10, OC and elemental carbon (EC) as well as particulate NO3−. Night-time levels of most constituents exceeded daytime levels due to poorer night-time dispersion conditions. At Claremont, OC and NO3− compounds account for 52% of the PM-10 while at Long Beach they account for 67% of the PM-10. On the average, there appears to be sufficient particulate ammonium (NH4+) to completely neutralize the nitrate and acidic sulfates. Significant artifact OC was detected and corrected for at both sites. At Claremont the artifact accounted for 21% of the uncorrected OC mass and 13% at Long Beach. Because of NO3− and NH4+ losses on Teflon filters, the measured PM-10 and fine particulate mass (FPM) had to be corrected. This correction amounted to increasing the average measured FPM and PM-10 by 17 and 12%, respectively, at Claremont, and 8 and 6%, respectively, at Long Beach.