Estuarine wetlands are highly dynamic, transitional environments increasingly recognized for their ecological value which are exposed to strong natural and anthropogenic-related fluctuations, i.e. tides, storm surges, floods, droughts, effluent discharges. The Samborombon Bay in the outer Río de la Plata estuary is an extensive (2240 km2), little urbanized, very shallow, mixohaline depositional environment declared RAMSAR site in 1997 with a high particulate load from the turbidity maximum zone of the estuary [3] and a continuously prograding coast. In addition to the terrestrial discharge of the Río de la Plata, which includes polluted inputs from Buenos Aires metropolitan area, the meandering Salado River drains a vast agricultural and livestock farming region (90000 km2) in the east-central Buenos Aires Province plain. The natural drainage of the Bay has been modified by several hydraulic projects to control major floods, i.e. Channel 15 enlarged in 1997 drains more than 70% of the Salado River discharge. In order to interpret historical PCBs inputs to the basin, in this paper we report a detailed study of a sediment core collected in high sedimentation area at the Salado River embouchure in the Samborombon Bay.Facultad de Ciencias Naturales y MuseoComisión de Investigaciones Científicas de la provincia de Buenos AiresConsejo Nacional de Investigaciones Científicas y Técnicas