ALIPHATIC, POLYCYCLIC AROMATIC HYDROCARBONS AND NITRATED-POLYCYCLIC AROMATIC HYDROCARBONS IN PM10 IN SOUTHWESTERN MEXICO CITY

A sampling campaign of airborne particles 10 m (PM10) was carried out from February to April of 2004 at the Universidad Nacional Autonoma de Mexico in southwestern Mexico City. The average PM10 mass concentration was 51 14 g m-3. Extracted organic matter was determined, with a mean of 6.5 1.7 g m-3, which represents 12.9% of PM10 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 C24 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 (NO3-) radicals in the presence of nitrogen oxides (NOx).