Micro-scale Spatial Patterns of PM2.5 in an Arid City: Evidence from Mobile Monitoring Across Urban Green and Non-green Areas.

Fine particulate matter (PM2.5) is a major urban air contaminant associated with adverse human health effects. Urban green spaces have been proposed as nature-based solution for mitigating particulate pollution, but evidence of their effectiveness at micro-scale in arid cities remains limited. We evaluated whether small urban green spaces are associated with local reductions in PM2.5 concentrations in an arid South American city. PM2.5 was measured during six mobile monitoring campaigns in winter 2026 along a 4.3 km urban transect comprising 75 georeferenced sampling locations. Sampling sites were classified as urban green spaces or non-green urban areas based on surrounding vegetation cover. The effects of site type were evaluated using Generalized Linear Mixed Models, accounting for traffic intensity, distance to the nearest road, and repeated measurements across sampling days and locations. PM2.5 concentrations were significantly lower in urban green spaces than in non-green areas, with adjusted concentrations approximately 31% lower after controlling traffic-related variables. Spatial interpolation identified areas with lower PM2.5 concentrations around small plazas and parks distributed along the monitoring transect. These findings indicate that even relatively small urban green spaces can provide measurable local air-quality benefits in arid cities and highlight the usefulness of mobile monitoring for detecting fine-scale spatial variability in particulate pollution.