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Marine sediments from the coastal zone of Santa Rosalía are characterized by high contents of heavy metals due to ancient mining and smelting of copper ores. In order to find out the presentday levels of metals and specially due to the soon opening of the new mining and metallurgic company of “El Boleo”, 75 surficial sediment samples were collected in September 2011. The total contents of 50 elements in the sediments were measured by a combination of ICP-AES and ICP-MS instruments after concentrated strong acid digestion and heating at 250°C. “Mobile” metals in the sediments were determined after cold acid leaching. The Principal Component Analysis with Varimax rotation was applied to the obtained dataset, which allowed distinguishing three associations of elements with high positive scores (> 0.5). The association I (Ag, Ba, Be, Bi, Cd, Co, Cu, Fe, In, Li, Mg, Mn, Mo, Ni, lanthanides, Pb, Sr, Tl, U, V, Y and Zn) presumably corresponds to the input of mineralized terrigenous material of ore deposits, naturally formed at first or modified during a smelting of ore minerals afterwards. The association II (Cs, Hf, K, Rb, Re, S, Se, Th and Corg ) probably reflects the contribution of fine natural clayey material, enriched in organic matter. The association III (Al and Sc) is probably due to the supply of the terrigeneous aluminosilicates. The enrichment factors (EFs) of Ag, Ba, Bi, Cd, Co, Cu, Mn, Ni, PB, Sb, U, V and Zn in sediments, calculated using Al as a normalizing crustal element, are higher than unity. With respect to the average EFs for the marine sediments with Cu content higher than the effect rangemedium guideline value (ERM) of 270 mg kg-1, these enriched elements showed the following sequence: Cu (115) > Zn (29) > Co (27) > Mn (23) > Cd (12.6) > U (11) > Bi (10.9) > Pb (6.7) > Sb (5.0) > Ag (4.1) > Ba (4.0) > Ni (3.2 ) > V(2.6). All these elements are supplied to the marine sedimentary environment from sources related to the ore-forming mineralization in this mining district, or as the constituents of smelter slags. The spatial distributions of total and acid leachable Cd, Co, Cu, Mn, Pb and Zn contents in the surface sediments delimit the principal “hot spots”, associated with the dumped smelting wastes. About 50% of the surface sediment samples exceeded the ERM guideline value of 270 mg kg-1 proposed for Cu, the principal pollutant of this specific environment.

Palabras clave: Paralarval assemblages; heavy metals; Santa Rosalía mining region; marine sediments; actual levels

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