Passive air samplers were deployed in 18 rural and urban locations in the densely populated Buenos Aires district to investigate airborne polychlorinated dibenzo-p-dioxin and polychlorinated-dibenzofuran (PCDD/Fs) profiles, sources and spatial patterns. Atmospheric concentrations reported as total toxic equivalents (TEQs), 2378-substituted (Σ17PCDD/F) and 4–8 homologous groups (Σ4–8PCDD/F) were highly variable and significantly correlated to urban scale. The rural average (3.0±2.7 fg TEQm−3)was thirty times less than metropolitan values (90±51 fg TEQm−3),with urban cluster (5.4±4.0 fg TEQm−3) and urbanized area (33±50 fg TEQm−3) in an intermediate position. A rural outlier exhibited the highest TEQ values (295–296 fg TEQ m−3) suggesting a local source. Principal component analyses (PCA) performed for Σ17PCDD/F and Σ4–8PCDD/F to identify source contributions showed more significant results for homologue groups compared to 17 congeners (83 and 45% of total variability explained, respectively) pointing to dominant diesel emissions enriched in TeCDF in rural areas, and open burning and industrial sources characterized by TeCDD, PeCDD contributing most in urbanized and metropolitan areas. Homologue group PCA also performed better clustering samples according to sources and TEQ concentrations. The PCDD/Fs profile of the rural outlier dominated by HxCDF and HpCDD/F showed a typical municipal incineration signature confirming the presence of local source.Facultad de Ciencias Naturales y Muse
