Magnetic Monitoring of Urban Parks Using <em>Tillandsia Recurvata</em> as a Particulate Matter Biocollector

This study assessed the spatial distribution and composition of airborne particulate matter within a 10-km long urban green corridor in Zacatecas, Mexico, using magnetic biomonitoring with Tillandsia recurvata and SEM-EDS particle characterization. A total of 44 samples were collected from distinct urban park contexts (e.g., commercial zones, malls, bus stop), revealing mass-specific magnetic susceptibility χ values ranging from 0.87 to 97.0 × 10−8 m3kg−1. Three compositional groups were identified based on a PCA performed using elemental concentrations from SEM-EDS and magnetic data, which are associated with traffic emissions and industrial inputs. SEM-EDS images confirmed abundant magnetite-like particles (1–8 μm) with hazardous metals including Pb (up to 5.6 wt.%), Ba (up to 67.6 wt.%), and Cr (up to 31.5 wt.%). Wind direction data indicated predominant SSW-NNE transport, correlating with hotspots in central and northeastern park areas. Overall, vegetated zones displayed significantly lower magnetic loads (mean χ = 8.84 × 10−8 m3kg−1, σ = 6.65 × 10−8 m3kg−1) compared to traffic-exposed sites (mean χ = 17.27 × 10−8 m3kg−1, σ = 12.44 × 10−8 m3kg−1), emphasizing the pollution mitigation role of green barriers. This research highlights the applicability of combined magnetic and microscopic techniques for evaluating the dynamics of airborne pollution in urban parks and supports their use as biofunctional filters in cities facing vehicular air pollution.