Autores: Elizabeth Vega*, Diego López-Veneroni, Omar Ramírez, Judith C. Chow, John G. Watson

* Departamento de Ciencias Ambientales | Contaminación Ambiental

Abstract

M_2.5 monitoring campaigns were conducted in 2006, 2010, and 2011 in Tula, Hidalgo, Mexico, a highly industrialized area which includes a refinery, a thermoelectric power plant, five cement plants, limestone mining, and industrial waste combustion. These data establish baselines and trends against which later concentrations can be compared as emission reduction plans are implemented. PM_2.5 mass, chemical composition, and 15 particle-bound polycyclic aromatic hydrocarbons (PAHs) were measured at two sites. PM_2.5 masses ranged from 26 to 31 µg m^–3. Carbonaceous aerosols were the largest PM_2.5 component, accounting for 47–57% of the mass. Approximately 40–51% of the carbonaceous aerosol was attributed to secondary organic carbon. Ionic species accounted for 40–44% of PM_2.5, with sulfate being the dominant ion. The sum of particle-bound PAH concentrations ranged from 14–31 ng m^–3. Six factors derived from Principal Component Analysis (PCA) explained ~85% of the PM_2.5 variance. The derived factors were associated with sources based on marker species resulting in heavy-oil combustion (22% of variance), vehicle engine exhaust (13–19% of variance), fugitive dust (18% of variance), biomass burning (9–13% of variance), secondary aerosols (14% of variance), and industrial emissions (6–10% of variance). Combustion of solid waste (e.g., tires and industrial waste) of the recycling cement kilns and incinerators resulted in elevated toxic species such as, Cd, and Sb in the range of 0.02–0.3 µg m^–3. A health risk assessment of carcinogenic trace elements was performed showing that the total cancer risk decreased for both children and adults in 2010/2011 (ranging from 3.5 × 10^–6 to 6.0 × 10^–5) as compared to 2006 (ranging from 8.6 × 10^–7 to 5.7 × 10^–6). The inhalation life-time cancer risk (ILCR) for particle-bound PAHs ranged from 8.6 × 10^–5 to 1.2 × 10^–4. Air quality can be improved by switching to cleaner fuels and benefit from the use of natural gas instead of fuel oil in the power plant.