Browsing by Author "Mouro, F."
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- Alterações recentes nas razões isotópicas de Pb em sedimentos do Canhão Submarino de Cascais, PortugalPublication . Mil-Homens, Mário; Caetano, M.; Lebreiro, Susana; Costa, A. M.; Richter, T.; Cesário, R.; Brito, Pedro Oliveira; De Stigter, H.; Boer, Wim; Trancoso, Maria Ascensão; Mouro, F.Temporal variations in lead concentrations and stable lead isotopic ratios in two sediment cores from the Cascais Canyon shows changes in sources of Pb during the last two centuries. The increase of total Pb contents wIth the evolution of Pb ratio recorded in both cores reveals the Increase of Pb from industrial sources. Nevertheless, this increase is lower in deeper core location (252-32) due to dilution and mixing with uncontaminated marine materials. An isotopic shift towards lower Pb/Pb in the shallower core (252-35) during the 1970s may reflect the increasing number of vehicles in the Lisboa area during that time.
- Submarine Cascais Canyon as a sediment conduit to the deep sea : comparison with adjacent slopesPublication . Costa, A. M.; Mil-Homens, Mário; Lebreiro, Susana; De Stigter, H.; Richter, T.; Boer, Wim; Trancoso, Maria Ascensão; Melo, Zenaida; Mouro, F.; Mateus, MSubmarine canyons are known to be important conduits that trap, accumulate and deliver both natural and anthropogenic sediments from the shelf to the deep sea. Ten multi-cores from the Cascais Canyon and from the neighbour slopes (off Estremadura and Sines) were dated by 21Opb methodologies and analyzed for texture, major and trace metals to evaluate the role of submarine canyons in the transport of anthropogenic metals to the abyssal plains. Higher accumulation mass rates were determined in the upper Cascais Canyon than in the lower canyon and slopes. Enrichment factors (EF) were used to evaluate the level of metal enrichment in the studied areas. EF values exceeding natural background concentrations were obtained for Pb suggesting an anthropogenic and/or diagenetic source for Pb enrichment in the Cascais Canyon, but also, to a lesser extent, in the Estremadura and Sines slopes. Studies of provenance based on the ratio of different stable Pb isotopes can help to determinethe origin of such metal in the sediments.