A study of elemental composition of PM2.5 samples collected at the main campus of the Universidad Nacional Autónoma de México, comprising data from 2015, 2016, and 2019, is described. X-ray fluorescence analysis was employed to measure concentrations of up to 19 elements, complemented with ion chromatography for eight ionic species (for samples of 2015 and 2016), and thermo-optical analysis for organic and elemental carbon (for samples of 2015). Positive matrix factorization (PMF) was applied to develop receptor models for each year, to identify polluting sources and their contributions to total mass. Five sources were identified in every case. With the aid of PMF, the influence of biomass burning on a major episode in May, 2019, was recognized. Comparisons with previous studies in this or nearby sites are also presented. It should be noted that only limited compositional data in this site are available since 2005 for the aerosol fine fraction.

The rapid increase in global plastic production has accelerated the dissemination of microplastics (MP), impacting urban and coastal environments. This study quantifies and categorizes MP in two major Mexican ports: Veracruz (Gulf of Mexico) and Manzanillo (Pacific Ocean). Nine polymer types were identified through micro-Fourier Transform Infrared Spectroscopy (micro-FTIR) analysis of air and seawater samples. Polyester (PES) was the most prevalent polymer, followed by acrylic polymers (ACR) and polyethylene (PE). At Veracruz, the airborne MP concentrations were 3.9 (1.9) MP m^-3 in the morning and 2.2 (1.4) MP m^-3 in the afternoon. In Manzanillo, morning and afternoon concentrations were 3.2 (1.8) MP m^-3 and 2.6 (1.6) MP m^-3, respectively. Surface concentrations of marine MP were elevated near the coast, averaging approximately 14.4 (1.4) MP m^-3. Additionally, artificial non-plastic particles (ANPP) were identified and were even more abundant than MP in both matrices. In all locations and matrices, fibers constituted at least 70 % of detected MP, while fragments comprised the remainder. Identified MP ranged in size (equivalent diameter) from 82 μm to 160 μm. The observed variations in MP composition and concentrations across sites, depths, and sampling times underscore the significant influence of proximity to port activities and local meteorological conditions. Furthermore, these findings provide compelling evidence supporting the transfer of MP from the ocean to the atmosphere via ocean-atmosphere interactions. These baseline data will inform targeted management and risk-assessment frameworks for Mexican coastal regions.

Samples of airborne particles with aerodynamic diameters smaller than 10 µm (PM₁₀) were collected in 2021 at two households in the Metropolitan Area of Mexico City. Both sites are in areas with different characteristics (residential or industrial zones). Simultaneous sampling indoors and outdoors was carried out at the two locations, using low-volume samplers. The study aimed to determine the indoor and outdoor gravimetric mass and elemental concentrations, identify emitting sources and possible penetration towards the households enhanced by natural ventilation, and assess risks to human health due to inhalation, ingestion, and dermal absorption, through hazard quotients. Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, Se, and Pb concentrations were measured with X-ray fluorescence. Mass concentrations were higher indoors than outdoors, and most elemental concentrations had similar values in both environments. Cluster analysis was applied to identify possible emitting sources. The results showed a strong penetration of geogenic and industrial emissions at the Iztapalapa site, while only particles of industrial origin entered the interior of the Tlalnepantla dwelling, in both cases caused by the natural ventilation of the households. Health risks due to exposure to particles containing Fe, Ni, Cu, Zn, and Mn are not significant, and Pb and Cr only pose a risk via ingestion for men and women, although for children, there is a risk due to ingestion of all these elements.