Current situation of polycyclic aromatic hydrocarbons (PAH) in PM2.5 in a receptor site in Mexico City and estimation of carcinogenic PAH by combining non-real-time and real-time measurement techniques
2020
Amador-Muñoz, O. | Martínez-Domínguez, Y.M. | Gómez-Arroyo, S. | Peralta, O.
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 µm (PM₂.₅) represent a human health risk due to their toxic properties. In this study, PAH in PM₂.₅ 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 PM₂.₅ 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 NO₂, 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 PM₂.₅ 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, NO₂ and wind speed to estimate PAH in PM₂.₅ at low-cost (r² = 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 PM₂.₅, O₃, BC and SO₂ to the sampling site, and local emissions of PAH, NO and CO.
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