Seasonal and size-resolved elemental composition and source apportionment of atmospheric particulate matter in a coastal urban–industrial region of Zonguldak, Türkiye

The present study examines the seasonal and size-resolved elemental composition of fine (PM2.5) and coarse (PM2.5–10) particulate matter in a coastal urban–industrial region influenced by multiple sources, including coal mining, coal combustion for heating and power generation, iron–steel with coke production, maritime fuel-oil use, traffic emissions, and natural marine and crustal sources. Seasonal contrasts were marked, with the heating period PM2.5 characterized by elevated concentrations of toxic elements (As, Sb, Cd, Pb, Se, V, Ni, and Cr) associated with combustion and industrial activities, reflecting intensified heating and industrial activities. Conversely, the composition of non-heating period PM2.5–10 was dominated by crustal, marine, and resuspended dust components, with persistent industrial influence. Enrichment factor (EF) analysis using Ti as a reference element indicated substantial anthropogenic enrichment for combustion and metallurgy, while crustal and marine elements remained near natural levels. Principal Component Analysis (PCA) was utilized to identify distinct seasonal and size-dependent source factors, including coal combustion, iron–steel production, fuel-oil and shipping emissions, traffic non-exhaust sources, crustal dust, marine aerosol, and resuspended coal fly ash. Discriminant Analysis (DA) confirmed clear separation between seasons and particle-size fractions, supporting the internal consistency of the EF–PCA–DA approach without serving as independent validation of source assignments.