Factors pyrene concentration

The physical effect of dilution of the aerosols due to increased mixing depths during transport of the air parcel inland is factored out by taking the ratios of the concentrations at Claremont to those at central Los Angeles. As seen in Table 10.32, the ratios are 0.21 and 0.20 for the low-reactivity PAHs benzo[k](luoranthene and i nde no[ 1,2,3-cd ]pyrene (Class V, Table 10.30), reflecting dilution, whereas the ratios are 0.10 and 0.03 for reactive BaP and cyclopenta[cd ]pyrene (Class II), respectively, indicative of reactions in addition to dilution. 

Enhanced excimer emission was also observed from PBAC bound to a-ZrP [20], Excimer formation from pyrene is well known in aqueous solutions [54], As in the case with AMAC, excimer formation is increased with PBAC concentration (Fig. 16) due to increased local concentrations but with two significant differences. Hydrophobic interactions between the pyrene molecules favor the aggregation of PBAC even at moderate coverages and the PBAC singlet excited state is much longer lived ( 200 nsec) than that of AMAC ( 10 nsec) these factors, in turn, promote excimer formation even at low loadings. The broad, red-shifted fluorescence band with a peak centered around 470 nm, characteristic of the pyrene excimer emission, is evident in Fig. 16. Rapid formation of the excimer at low coverages is also evident from the plot of the ratio of emission intensities at... 

Because the concentrations of fluorene and pyrene are considerably higher than the others (by approximately a factor of 5), these two features were divided by 5. Then the data were normalized to a constant sum for each sample. This normalization was caused by the fact that we are rather interested in relative concentrations than in absolute values. 

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