Browsing by Author "Caetano, M."
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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.
- Influence of diagenetic processes and terrestrial/anthropogenic sources in the REE contents of the Cascais submarine canyon (Iberian western coast)Publication . Mil-Homens, Mário; Brito, Pedro Oliveira; Caetano, M.; Costa, A. M.; Lebreiro, Susana; Trancoso, Maria Ascensão; De Stigter, H.ABSTRACT: Temporal variations of rare earth elements (REE) and their fractionation patterns, major elements, Pb and Hg were determined in two multicores collected at 445 and 2100 m water depth (mwd) in the Cascais submarine canyon (CSC). The PAAS-normalized REE patterns suggest mixing of Tagus estuarine and marine sediments, marked by MREE (Nd‐Dy series) enrichment and by positive Eu-anomaly, with marine sediments. The positive Eu/Eu* implies incorporation of detrital feldspar minerals derived from the estuary. Ce/Ce*, (La/Yb)PAAS and (Nd/Yb)PAAS show differences between the two cores. Core 252-35 from the shallower site is enriched in HREE (Ho‐Lu series) over LREE (La‐Pr series), a pattern also found in the Tagus estuary in the vicinity of an abandoned chemical complex, where the environment is affected by the legacy of massive-sulfide ores processing. There seems to be only limited down-canyon sediment transport to the deeper reaches where core 252-32 was collected. This deeper site shows Ce/Ce* peaks coinciding with low (La/Yb)PAAS values suggesting preferential diagenetic remobilization of LREE relative to HREE. Upcore Pb/Al and Hg/Corg trends observed in both cores indicate dispersion of the anthropogenic component from the estuary through the CSC, which is less obvious from the ∑REE/Al trends particularly in the deeper site. This may suggest the influence of diagenetic processes in the REE signal, associated with relatively low sediment accumulation rates.
- Recent changes in lead isotopic signature in sediments of the Cascais Canyon (Portugal)Publication . Mil-Homens, Mário; Caetano, M.; Lebreiro, Susana; Costa, A.; Richter, T.; Cesário, R.; Brito, Pedro Oliveira; Stigter, H. de; Boer, Wim; Trancoso, Maria Ascensão; Mouro, Filomena C.
- Recent changes in lead isotopic signature of the Cascais Canyon (Portugal)Publication . Mil-Homens, Mário; Caetano, M.; Costa, A. M.; Lebreiro, S. M.; Stigter, H. de; Richter, T.; Cesário, R.; Brito, Pedro Oliveira; Boer, Wim; Trancoso, Maria Ascensão; Mouro, Filomena C.
- Temporal evolution of stable lead isotope ratios in sediments of the Central Portuguese Margin : a fingerprint of human activitiesPublication . Mil-Homens, Mário; Caetano, M.; Costa, Ana Novo; Lebreiro, Susana; Richter, Thomas; Stigter, Henko C. de; Trancoso, Maria Ascensão; Boer, Wim
- Temporal variations in the stable isotopic composition of Hg in sediments of the Central Portuguese MarginPublication . Mil-Homens, Mário; Blum, J. D.; Canário, João; Caetano, M.; Costa, A.; Lebreiro, Susana; Branco, Vasco; Johnson, M. W.; Trancoso, Maria Ascensão; De Stigter, Henko; Richter, Thomas; Boer, Win