CHARACTERIZATION OF ATMOSPHERIC COARSE PARTICLES IN THE LOS-ANGELES BASIN

Size-selective coarse particle samples were collected during the 1986 Los Angeles Carbonaceous Species Methods Comparison Study (CSMCS) with a rotary inertial impactor. In addition to particle mass distribution information, chemical analysis of sulfate and nitrate were also obtained. Both short-term (approximately 30 minutes) and long-term (12-hour) samples were obtained, from which 24-hour average concentrations were determined. A least square error best-fit method was used to estimate the total coarse particle mass (> 1 μm), mass median diameter (MMD)σg. The results were compared to samples collected by a high-volume sampler with a Sierra-Anderson 321A size-selective PM10 inlet. On the average, 28% of the total particulate mass (fine and coarse) and 16% of the total particulate nitrate was not collected by the PM10 sampler. Only 3% of the particulate sulfate was contributed by particles greater than 10 urn. More total coarse particle and nitrate mass were generated during the day than at night. No diurnal variation was observed for sulfate. Weekday concentrations were higher than weekend concentrations. The coarse particulate MMD increased with friction velocity and ozone concentration. © 1990 Elsevier Science Publishing Co., Inc.