Descriptive analysis of PM2.5 and PM10 at regionally representative locations during SJVAQS/AUSPEX

SJVAQS/AUSPEX acquired PM2.5 and PM10 samples at ten sites in Central California for five ozone episodes over 14 intensive sampling days. Four sample sets per day were acquired for 5 and 7 h durations and measured for particle mass; elements; water-soluble chloride, nitrate, sulfate, ammonium, sodium, and potassium ions; and organic and elemental carbon. Gaseous ammonia, nitric acid, and sulfur dioxide concentrations were acquired with absorbent filter material. To guard against contamination of these gases after sampling, the filter packs were sealed and refrigerated prior to analysis. Crustal species such as aluminum, silicon, calcium, titanium, iron, and calcium, were found in coarse particles at most sites. Substantial amounts of sodium and chloride were detected in the coarse particle fraction at the coastal Point Reyes site. Organic carbon and sulfate were the most abundant species in the PM2.5 fraction. Elemental carbon concentrations were low at all sites. Only one 24 h average PM0 concentration exceeded the U.S. PM10 standard of 150 μg m−3 during the study period, and this occurred at the agricultural-oriented Buttonwillow site. The highest concentrations of most chemical species were found at sites in the Southern San Joaquin Valley.