Browsing by Author "Mil-Homens, Mário"
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- Footprint of roman and modern mining activities in a sediment core from the southwestern Iberian Atlantic shelfPublication . Mil-Homens, Mário; Vale, Carlos; Naughton, Filipa; Brito, Pedro; Drago, Teresa; Anes, Bárbara; Raimundo, Joana; Schmidt, Sabine; Caetano, MiguelA 5-m long sediment core (VC2B), retrieved in the Southwestem Iberian Atlantic shelf, at 96 m water depth, was used to assess major changes in climate and human activities during the last 9.7 kyrs. Analytical measurements included sedimentological (mean grain size, and the contents of sand, silt and day), geochemical (major, minor, trace and rare earth elements; REEs) and chronological (Pb-210 and C-14) parameters. Two episodes of increment of fine-grained particles, occurring at 3050 BCE and 1350 CE, suggest the retreat of the coast line to the present level and the beginning of a wetter phase associated with the "Little Ice Age". The North American Shale Composite (NASC)-normalized REE-pattern detected in the shelf is similar to that found in the Guadiana estuarine sediments. The possibility of this estuary as a contributor to the sediment load deposited in the adjacent coastal zone was indicated. Trace elements were significantly correlated with Al until 1850 CE, pointing that grain-size rules its distribution in sediments. The depth variation of As, Cu and Pb enrichment factors relative to background values shows two periods of intense human activity that can be mainly linked to mining: (i) across the Roman Period, marked by low enrichments; and (ii) starting on the second half of the 19th century until nowadays with significantly increased enrichments, especially of Pb and Cu. In addition to As, Cu and Pb, this period is also marked by high enrichments of Hg and Zn. Despite the decrease/closure of sulphide massive deposits mining exploitation (e.g., Sao Domingos, Las Herrerias) during the second half of the 20th century, results showed ongoing input of Pb,Cu, As, Hg and Zn to coastal sediments. Thus, the legacy of contamination by these elements, mainly from leaching of slags and tailings, and remobilization/reworking of contaminated estuarine sediments, is still recorded in marine sediments. (C) 2016 Elsevier B.V. All rights reserved.
- Sources and distribution of organic matter and polycyclic aromatic hydrocarbons in sediments of the southwestern Portuguese shelfPublication . Mil-Homens, Mário; Gonçalves, Sofia; Cortés, Alejandro; van Drooge, Barend L.; Stigter, Henko de; Grimalt, Joan O.; Cordeiro, Lívia; Santos, Miguel M.; Almeida, C. Marisa R.; Caetano, MiguelTotal organic carbon (Corg), total nitrogen (Ntot), Corg/Ntot, δ13Corg, δ15N, calcium carbonate (CaCO3), and grain size were analyzed in 70 surface samples and 19 short cores from the southwestern Portuguese shelf. Perylene and USEPA-16 PAHs were quantified in a subset of these samples. The findings suggest that organic matter derives from a mix of terrestrial and marine sources, outlined by Corg, Ntot, and isotopic signatures. Perylene combined with δ13Corg was used to identify the main PAH sources in these environments. Diagnostic perylene ratios revealed contributions from natural sources in the Tagus region and contaminated materials from the Sado Dredged Disposal Site, with additional perylene in Sines linked to atmospheric deposition of pyrogenic sources. A significant correlation between perylene and USEPA-16 PAHs indicates natural and anthropogenic inputs from the Tagus. This multiproxy approach—combining USEPA-16ΣPAHs, perylene, and δ13Corg—offers insights for assessing environmental risks and guiding marine environmental management according to the MSFD.
- Spatial distribution and temporal trends of butyltin compounds (TBT, DBT & MBT) in short sediment cores of the SW Portuguese Shelf (western Iberian Margin, NE Atlantic)Publication . Mil-Homens, Mário; Almeida, C. Marisa R.; Dias, Sofia; Soares, Warley; van Gaever, Piet; de Stigter, Henko; Santos, Miguel M.; Santana, André; Freitas, Mafalda; Abrantes, Fatima; Caetano, MiguelSpatial patterns and temporal trends of the butyltin compounds tributyltin (TBT), dibutyltin (DBT), and mon-obutyltin (MBT) were investigated in a set of sediment samples collected along the SW Portuguese continental shelf. This region did not reach the Good Environmental Status (GES) in accordance with the Marine Strategy Framework Directive (MSFD) during a first evaluation carried out in 2012. Overall, MBT and DBT were the predominant organotin species detected, but high concentrations of TBT were found in and around disposal sites for dredge sludge derived from the dredging in navigation channels, harbours, and shipyard facilities of the Tagus and Sado estuaries. Although Portuguese regulations for monitoring sediment quality in relation to dredging activities consider only PAH, PCB and HCB, they also dictate that other organic contaminants such as butyltin compounds (BTs) should be monitored if suspicion of high values exists, but no action limits are defined for these (MAOTDR, 2007). Without action limits, the monitoring recommendation given in the regulations is not put into practice. Considering their toxicity, BT derivates should be integrated in the legislation, because they represent an environmental threat in the relocation of dredged material, especially when derived from harbour and shipyards areas. Based on this study, we recommend giving more attention to the amounts and impacts of BTs in sediments at dredged material disposal sites (DMDS) and their surroundings. Or even better, in order to be more efficient, monitoring should be done at the source of the dredged materials and not at the sink. In case it is not done, the monitoring of concentrations of TBT (and other BTs) in sediments and organisms, including imposex studies, at all Portuguese sites for disposal of dredged material receiving slightly to strongly contami-nated dredged material must be developed.