Evaluation of anthropic influences in an estuarine system of Southeastern Brazilian Coast by applying enrichment factors in cores from Bertioga Channel, Sao Paulo state

Santos estuary, located in Southeastern Brazilian Coast, is impacted by several anthropic activities. The largest commercial harbor in South America and the main petrochemical and metallurgical industrial centre in the country, with approximately 1100 industries, are also in this estuary. The estuarine system has an important channel, called Bertioga Channel, which connects the upper Santos estuary to the ocean. In this channel are located the main mangroves of the estuarine complex that have a great potential of heavy metals retention. This behavior is related to sedimentary dynamics of system, where contaminated sediments from upper estuary are filtrated by channel before reaching the ocean. In this context, the main goal of this work was to carry out a study on toxic elements in cores from Bertioga Channel. Enrichment Factor (EF) was determined and it was related to geochronological data, allowing the evaluation of anthropic activities impact in this region. Thus, in February 2010, were collected five cores along the channel using a vibrocorer. The cores (150 - 220 cm) were sliced at every 2 cm, the samples were frozen and freeze-drying. Elemental preparation and analysis (As, Cd, Cr, Cu, Ni, Pb, Sc and Zn) followed SW-846 methodologies applying ICP-OES technique. Geocronology was determined via gamma spectrometry, by 210Pbxs and 137Cs methods. In order to assess the degree of sediment contamination, enrichment factors (EF) were calculated using Sc as normalization element Background values correspondeded to the element concentration in the bottom sediment core as determined by 210Pb chronology. EFs obtained in all analyzed cores were lower than 2, indicating a minimal pollution for the region. However, in core Bertioga 5 (the closest one to Santos harbor), it can be seen As, Cr, Pb and Zn enrichment from the bottom to the top, mainly from 70's, when harbor activities expanded. Despite of the low levels found for the studied elements, Bertioga channel area has suffered environmental impact due to domestic sewer releasing and the presence of marina in the region.