Characterization of atmospheric black carbon in particulate matter over the Monterrey metropolitan area, Mexico, using scanning electron microscopy

The Monterrey metropolitan area (MMA) had an estimated population of 3,776,621 inhabitants in 2010, representing 81 % of the population of the northeastern Mexican State of Nuevo León. This heavily urbanized region is characterized not only by its large commercial and industrial activities, but also by its dense suspended particulate matter (SPM) pollution. Black carbon (BC), a significant component of SPM, has been recognized as a relevant health hazard and a crucial contributor for global warming due to the high capability of absorbing sunlight and contributing to the greenhouse effect. The aim of this work was to detect, characterize, and analyze the BC content in the SPM present in the MMA by scanning electron microscopy (SEM). The standardized method may be used to assemble a dataset applicable to the development of simulated climate scenarios for the region in future years. SPM concentrations were estimated to be 96.0 ± 34.8 μg/m 3 . SEM analyses indicated that BC content in SPM was 1.6 ± 0.3 μg/m 3 , with a particle size range of 0.5–10.0 μm. It is concluded that the SPM pollution from the MMA is above the World Health Organization air quality guidelines. SPM and BC levels reported in this work position the MMA as one of the most polluted urban air areas in Latin America.