Temporal clustering of metals in a short sediment core of the Cascais Canyon (Portuguese Margin)

Autor: Mário Mil-Homens, Ana M. Costa, Susana M. Lebreiro, João Canário, Cristina Lopes, Filomena Mouro, Manuela Mateus, Henko de Stigter, Thomas Richter, Vasco Branco, M. Ascensão Trancoso, Zenaida Melo, Wim Boer
Jazyk: angličtina
Rok vydání: 2010
Předmět:
Zdroj: Scientia Marina, Vol 74, Iss S1, Pp 89-98 (2010)
Druh dokumentu: article
ISSN: 0214-8358
1886-8134
DOI: 10.3989/scimar.2010.74s1089
Popis: The Cascais Canyon delivers contaminated sediments from the shelf to the deep marine environment. Multi-core PE252-32, located at 2100 m water depth in the canyon, records the latest 300 years of sedimentation. It was dated by 210Pb and analyzed texturally and geochemically for major elements and selected trace metals (Cu, Cr, Hg, Li, Ni, Pb and Zn). Cluster analysis performed on the down-core geochemical data identified four groups of variables related by grain-size, geochemical source and composition. Mercury, Pb and Zn were grouped in a cluster representing the anthropogenic component. Cluster analysis was applied again particularly to the latter cluster relatively to depth, in order to constrain the onset and temporal evolution of anthropogenic contamination. A second clustering, made on the basis of Hg, Pb and Zn, grouped samples by age and degree of anthropogenic contamination. One cluster contained relatively uncontaminated samples older than 1900 AD, and another cluster samples younger than 1900 AD with distinct metal enrichment. Maximum enrichments occurred during the early 1980s, followed by a slight recovery from the mid-1980s to the present. Mercury was the element with the highest enrichment factor (EFHg=5). Despite relatively low accumulation rates at this core location, our results show the importance of the Cascais Canyon as a transport route for contaminated sediments from the Tagus prodelta into the deep regions of the Portuguese Margin.
Databáze: Directory of Open Access Journals
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