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

Abstract

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).

Keywords:

• n-alkanes
• PAHs
• nitro-PAHs
• air pollution
• equivalent carcinogenic potency

The present work was supported partially through SEMARNAT-CONACyT project 2002-C01-0252/A1 and FOSEMARNAT-2004-01-409. A special thanks to the General Direction of Graduate Studies of Universidad Nacional Autónoma de México for the scholarship given to doctorate student Hugo Saldarriaga, to Wilfrido Gutiérrez, Mario Murillo Tovar and Martha Elena Díaz Murillo for their technical assitance, to the personnel of the Red Automática de Monitoreo Atmosférico del Gobierno del Distrito Federal for the data on atmospheric pollutants, and for Dana E. Erickson and Adam C. Grenier of Peace Corps Mexico for the revision of this manuscript.

Notes

⁵⁴- Liwan, China: Mean of eleven samples, 12–18 April and 12–14 July, 2001, urban area.

⁵⁵-Naples, Italy: Central part of the city, mean of twenty one samples, 24–30 September, 1996; 26 February–4 March, 1997; 25 June–1 July, 1997.

⁵⁶-Santiago, Chile: Downtown, Mean of four samples, 12 August–26 September, 1993.

⁵⁷-Seoul, Korea: Urban site, particulate phase, 29 October–07 November, 1998; 20 February–1 March, 1999; 31 May–9 June, 1999; 11–17 September, 1999; 27 November–9 December, 1999, number of samples not given.

^a Copenhagen,

^b Riso,

^c Baltimore_winter,

^d Baltimore_summer,

^e Fort Meade_winter,

^f Fort Meade_summer, n.a. not available or not measured.