Aliphatic, Polycyclic Aromatic Hydrocarbons and Nitrated-Polycyclic Aromatic Hydrocarbons in Pm10in Southwestern Mexico City

A sampling campaign of airborne particles ≤ 10 μ m (PM 10 ) was carried out from February to April of 2004 at the Universidad Nacional Autónoma de México in southwestern Mexico City. The average PM 10 mass concentration was 51 ± 14 μ g m−3. Extracted organic matter was determined, with a mean of 6.5 ± 1.7 μ g m−3, which represents 12.9% of PM 10 mass concentration. The standard additions method was used on real samples at four concentration levels for 13 n-alkanes, 14 PAHs and 5 nitro-PAHs. The average concentration for the sum was 99.04 ng m− 3 for n-alkanes, 4.9 ng m−3 for PAHs and 710 pg m− 3 for nitro-PAHs. Higher concentrations of n-alkanes > C 24 were found, indicating biogenic emissions as the dominant source. Coronene, benzo[ghi]perylene, benzo[b+j+k]fluoranthenes and indeno[1,2,3-cd]pyrene were the most abundant PAHs, suggesting a strong contribution from incomplete combustion of gasoline. The PAHs considered for calculating BaPE represented 52% of the total PAHs analyzed. The presence of 9-nitroanthracene indicates direct emission from diesel combustion and heterogeneous nitrating reactions on sorbed particles, while 2-nitrofluoranthene, indicates gas-phase reactions with fluoranthene, hydroxyl (OH−) and/or nitrate (NO 3 −) radicals in the presence of nitrogen oxides (NOx).