Nitropyrenes, atmospheric production

As we have seen, key nitroarenes found in extracts of ambient particulate matter are 1-nitropyrene (1-N02-Py), predominant in primary combustion emissions, and 2-nitrofluoranthene and 2-nitropyrene, major products of gas-phase atmospheric reactions. Here we focus simply on their atmospheric fates as particle-bound species participating in heterogeneous decay processes. Formation of such nitro-PAHs in gas-phase reactions is addressed in Section F. 

Nitropyrene was the sole product formed from the gas-phase reaction of pyrene with OH radicals in a NOx atmosphere (Arey et al, 1986). Pyrene adsorbed on glass fiber filters reacted rapidly with N2O5 to form 1-nitropyrene. When pyrene was exposed to nitrogen dioxide, no reaction occurred. However, in the presence of nitric acid, nitrated compounds were produced (Yokley et al, 1985). Ozonation of water containing pyrene (10-200 pg/L) yielded short-chain aliphatic compounds as the major products (Corless et al, 1990). A monochlorinated pyrene was the major product formed during the chlorination of pyrene in aqueous solutions. At pH 4, the reported half-lives at chlorine concentrations of 0.6 and 10 mg/L were 8.8 and <0.2 h, respectively (Mori et al, 1991). 

FIGURE 10.22 Direct mutagenicity of ambient particles (mutagen density, rev m-3, TA98, —S9) as a function of ambient concentrations of 2-nitropyrene, a directly mutagenic product of a gas-phase atmospheric reaction initiated by OH radical attack on pyrene. Samples collected at six sites in California with different types of emissions ( ) Glendora (O) Yuba City ( ) Concord ( ) Mammoth Lakes ( a ) Oildale ( ) Reseda (see Fig. 10.22) (adapted from Atkinson et al., 1988a). 

In ambient air samples analyzed by GC-MS, different peaks of isomers of nitropyrenes and nitrofluoranthenes can be observed (Fig. 2). Some of these products are combustion-derived, while others primarily originate from atmospheric reactions. Some previously reported extremely high concentrations of 1-NP [31] might be partly explained by poor separation and identification of different isomers of 1-NP in high-performance liquid chromatography (HPLC) analysis equipped with fluorescence detection. 

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