The middle Paraíba do Sul River region represents Brazil’s most industrialized area, where the largest steel industry in the country, the National Steel Company (Companhia Siderúrgica Nacional - CSN) is located, with an annual steel production of 5.8x106 tons. The Light hydropower complex is located downstream from the CSN. In the present study, four sediment cores samples were collected at the Vigário Reservoir. Following porosity profiling, three were selected for 210Pb dating. A high sediment accumulation rate (SAR) was observed, averaging 2.9 cm y− 1 for the last twenty years, which fits the mean SAR of 2.7 cm y− 1, for the 2001–20017 time interval, obtained based on bathymetric studies. Chromium and zinc, both associated to the CSN activities, presented a trend towards lower values during the last twenty years, attributed to the implementation of the ISO 14001 policy at the CSN. Chromium reached higher concentrations than the probable effect level (PEL), although actual values were close to the threshold effect level (TEL). Mercury concentration variations were attributed to sediment granulometry changes and not to eventual illegal gold mining activities along the middle of the Paraiba do Sul river, although mercury flux pointed out the contrary.

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