Temporal variation of nitro-polycyclic aromatic hydrocarbons in PM10 and PM2.5 collected in Northern Mexico City

With the aim to determine the presence of individual nitro-PAH contained in particles in the atmosphere of Mexico City, a monitoring campaign for particulate matter (PM(10) and PM(2.5)) was carried out in Northern Mexico City, from April 2006 to February 2007. The PM(10) annual median concentration was 65.2μgm(-3) associated to 7.6μgm(-3) of solvent-extractable organic matter (SEOM) corresponding to 11.4% of the PM(10) concentration and 38.6μgm(-3) with 5.9μgm(-3) SEOM corresponding to 15.2% for PM(2.5). PM concentration and SEOM varied with the season and the particle size. The quantification of nitro-polycyclic aromatic hydrocarbons (nitro-PAH) was developed through the standards addition method under two schemes: reference standard with and without matrix, the former giving the best results. The recovery percentages varied with the extraction method within the 52 to 97% range depending on each nitro-PAH. The determination of the latter was effected with and without sample purification, also termed fractioning, giving similar results. 8 nitro-PAH were quantified, and their sum ranged from 111 to 819pgm(-3) for PM(10) and from 58 to 383pgm(-3) for PM(2.5), depending on the season. The greatest concentration was for 9-Nitroanthracene in PM(10) and PM(2.5), detected during the cold-dry season, with a median (10th-90th percentiles) concentration in 235pgm(-3) (66-449pgm(-3)) for PM(10) and 73pgm(-3) (18-117pgm(-3)) for PM(2.5). The correlation among mass concentrations of the nitro-PAH and criteria pollutants was statistically significant for some nitro-PAH with PM(10), SEOM in PM(10), SEOM in PM(2.5), NO(X), NO(2) and CO, suggesting either sources, primary or secondary origin. The measured concentrations of nitro-PAH were higher than those reported in other countries, but lower than those from Chinese cities. Knowledge of nitro-PAH atmospheric concentrations can aid during the surveillance of diseases (cardiovascular and cancer risk) associated with these exposures.