Seasonal variability of PM2.5-bound metals and their relationship with meteorological conditions in an urban-industrial area of northern Mexico: a PCA-based assessment.

PM2.5 particulate matter and its metallic composition are influenced by meteorological conditions; consequently, its seasonal behavior may differ in semi-arid urban-industrial environments. This study evaluated the seasonal variability of PM2.5 and associated metals, as well as their relationship with meteorological conditions in Saltillo, northern Mexico, during 2023. PM2.5 samples were collected across the four seasons using a low-volume sampler (MiniVol). Ten metals (Al, Cd, Cu, Fe, K, Mn, Na, Ni, Pb, and Zn) were quantified using Flame Atomic Absorption Spectrometry (FAAS), while temperature, relative humidity, wind speed, precipitation, and barometric pressure were recorded simultaneously. Principal Component Analysis (PCA) was used to identify correlations between PM2.5, the metals, and meteorological variables. Mean PM2.5 concentrations showed seasonal variability: 115.3 ± 37.2 μg/m3 in winter, 40.71 ± 6.80 μg/m3 in spring, 46.43 ± 22.88 μg/m3 in summer, and 152.9 ± 23.6 μg/m3 in autumn. The highest PM2.5 levels were recorded during the colder seasons, under conditions that limited atmospheric dispersion and wet deposition. Conversely, several metals exhibited higher concentrations during spring and summer; Cd reached 3.130 ± 1.202 μg/m3 in spring and Zn reached 1.697 ± 1.471 μg/m3 in summer, whereas Na showed its maximum concentration in winter (17.41 ± 10.88 μg/m3). The first three principal components explained 62.7% of the total variance and revealed associations among particulate matter, metal concentrations, and meteorological variables. The results indicate that PM2.5 mass and metal enrichment respond differently to seasonal meteorological conditions and reflect the combined influence of atmospheric processes and local sources-both natural and anthropogenic. These findings underscore the importance of considering both particle mass and chemical composition when assessing seasonal air pollution in urban-industrial environments.