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FIGURE 10.2 Average ambient concentrations (ng m~3) of gas-and particle-phase PAHs collected at four urban sampling sites across the Los Angeles Air Basin for eight 4-h sampling periods over two hot days, September 8-9, 1993, during a heavy smog episode (peak ozone 290 ppb at Claremont, California). For concentration data and site locations, see Table 10.8 and Fig. 10.23. Naphthalene was collected in a VOC stainless steel canister; 3- to 6-ring PAHs were sampled independently using a quartz fiber filter/PUF plug, Hi-Vol dichotomous virtual impactor system similar to that shown in Fig. 10.4 (adapted from Fraser et al., 1998).

al., 1996). For example, Arey and co-workers (1989a) have used Tenax-GC in "low-flow" (~1 L min-1) and "high-flow" cartridges C —10 L min-1). Naphthalene was sampled with the low-flow cartridge because of its great abundance (e.g., the highest naphthalene concentration in a 12-h sample was 6100 ng m~3 = 1.1 ppb), and the remaining seven PAHs with a high-flow cartridge.

Table 10.10 gives the concentrations of volatile PAHs averaged over a 9-day event in August 1986, with nine 12-h daytime and nine 12-h nighttime sample collection periods. The sampling site was less than 1 km from a major freeway so that these data are characteristic of air parcels heavily impacted by motor vehicles. The nighttime average concentrations for naphthalene were

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