Atmospheric Polychlorinated Biphenyls (PCBs:Σ42 congeners) collected by polyurethane passive samplers (PAS-PUFs) in 29 stations from July 2010 to February 2014 (n = 141) in the most productive and populated Southern Rio de la Plata area in Argentina were evaluated to assess concentration gradients, potential sources and compositional profiles related to different land use and urbanization. On a global scale, total airborne PCBs concentrations are low/very low (below detection limit to 937 pg m⁻³) and show a significant potential correlation with urban scale increasing 2.5 times each 10 times increase of population reflecting the primary role of urbanization controlling PCB emissions. Compositional patterns evaluated by principal component analysis (PCA) of individual congeners indicated that highly populated atmospheres are enriched in lighter, more volatile tri, tetra and penta chlorine congeners of lighter Aroclor mixtures (from 1242 to 1254) suggesting actual emission of fresh PCBs signatures from sealants, combustion and/or electrical equipment. Sub urban and rural sites show a gradual transition to heavier Aroclor mixtures (from 1254 to 1260) with predominance of more persistent hexa and hepta PCBs indicating an aged background signal resulting from long range transport and/or reemission from historic reservoirs such as soils.Facultad de Ciencias Naturales y Museo