Current situation of polycyclic aromatic hydrocarbons (PAH) in PM_(2.5) in a receptor site in Mexico City and estimation of carcinogenic PAH by combining non-real-time and real-time measurement techniques

摘要

Air pollution is a public health concern. Polycyclic aromatic hydrocarbons (PAH) are ubiquitous atmospheric pollutants contained in the atmospheric aerosol. PAH in particulate matter with diameters ≤2.5 urn (PM_(2.5)) represent a human health risk due to their toxic properties. In this study, PAH in PM_(2.5) at a receptor site of Mexico City during the dry cold season were determined. The most abundant PAH (median, 10-90th percentile, pg m~(-3)) were benzo[ghi]perylene (467, 291-697), followed by pyrene (427, 218-642). A decrease around 40% in the carcinogenic PAH onto PM_(2.5) was calculated with respect to the same PAH measured a decade ago, at the same receptor site, despite of increase in vehicle fleet. The PAH decrease trend agrees with the decrease trend of CO, NO and NO_2, released into the air by similar emission sources than PAH. Control emissions strategies implemented by local and federal authorities are discussed. PAH analyses were carried out by non-real-time and real-time methods. The PAH non-real-time method involved PM_(2.5) sampling, sample treatment and gas chromatography-mass spectrometry analysis. The PAH real-time method involved the use of a photoelectric aerosol sensor (PAS). The PAH determination by non-real time method was selective and efficient, with recoveries between 75 + 14% and 98 ± 26%. By combining non-real-time and real-time methodologies, multivariate regression models were obtained based on PAS response, NO_2 and wind speed to estimate PAH in PM_(2.5) at low-cost (r~2 = 0.59 to r2 = 0.89). Fossil fuel combustion from vehicles was the major source around the sampling site. Diagnostic ratios (DR) based on retene, chrysene, and triphenylene, suggested biomass burning emission sources. Photo-oxidation in sunny months was observed based on benzo[a]pyrene, benzo[ghi]perylene, benz[a]anthracene, indeno[ 1,2,3-cd]pyrene and black carbon. The correlation analyses suggested transport of PM_(2.5), O_3, BC and SO_2 to the sampling site, and local emissions of PAH, NO and CO.