Urban land use influences on platinum group element (PGE) distribution in Alcalá de Henares

Introduction
Platinum group elements (PGEs), including platinum (Pt), rhodium (Rh), and palladium (Pd), are increasingly detected in urban soils, largely due to vehicular emissions and industrial activities. Understanding how land use influences their spatial distribution is essential for exposure risk assessment and urban planning.

Methods
A total of 137 surface soil samples were collected from urban parks (n=97), gardens (n=18), and industrial zones (n=22) in Alcalá de Henares, Spain. Samples were digested using microwave-assisted acid protocols and analysed by ICP-MS. Data were statistically evaluated by Kruskal–Wallis tests and post hoc pairwise comparisons to assess inter-group differences.

Results
Pt and Rh concentrations were significantly higher in industrial soils compared to urban parks and gardens (p < 0.05), while Pd showed no significant difference across land use categories. These patterns likely reflect the proximity of industrial zones to point sources and suggest higher vehicular density in adjacent areas. Enrichment factor (EF) analysis indicated moderate to significant anthropogenic input for Pt and Rh, with industrial areas exhibiting the highest EF values for both elements.

Conclusions
Land use type plays a key role in PGE distribution. Industrial zones act as hotspots for Pt and Rh accumulation, emphasising the need for targeted environmental monitoring and potential remediation strategies. Future studies should explore temporal changes and linkages with human biomonitoring data to assess health implications.