Nanomineralogical and geochemical signatures of coal-derived particles in playground dust

Urban playgrounds located near coal-fired power plants can act as long-term sinks for nanoparticle-rich atmospheric fallout. This study integrates nanomineralogical characterization with multivariate geochemical analysis to elucidate the origin, speciation, and environmental role of coal-derived iron nanoparticles (Fe-NPs) in playground dust. Elemental datasets reveal a consistent multielemental covariance linking Fe with Pb, Mn, Ni, Mo, Ga, Ge, Nb, and light rare-earth elements (LREEs), indicating a dominant contribution from coal-combustion residues rather than pedogenic sources. Strong internal coherence among LREEs, coupled with stable Th-REE relationships and minimal HREE/LREE fractionation, points to the persistence of coal-derived accessory minerals, particularly monazite-group phosphates, occurring as nano- to submicrometric inclusions within Fe-rich and silica-rich matrices. Poorly crystalline Fe(III) oxyhydroxides, jarosite-group sulfates, and amorphous Fe-O-Si phases act as vectors, enhancing the retention and redox-controlled remobilization of hazardous elements. These are highly persistent and prone to resuspension, increasing the likelihood of inhalation and incidental ingestion. The results provide mineralogical and statistical evidence that playground dust contamination is predominantly derived from coal-ash emissions, with secondary contributions from vehicular sources. The study highlights the need to incorporate nanoparticle-resolved mineralogy into environmental monitoring and health risk assessments in coal-impacted urban environments. Because particle-size distributions and exposure concentrations were not measured systematically, these observations indicate potential inhalation and incidental ingestion pathways rather than a quantified exposure or health risk.