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| Ramalhosa, Elsa; Río-Segade, Susana; Pereira, Eduarda; Vale, Carlos; Duarte, Armando. |
| Dissolved reactive mercury was determined in water samples from Ria da Aveiro, a coastal lagoon contaminated by mercury. Concentrations increased with acid dilution to a maximum of 193% in samples containing organic matter with high aromaticity, as inferred from absorbances at 250, 280 and 365 nm. Laboratory experiments with potassium hydrogenoftalate and humic acids solutions proved the influence of aromaticity in complexing mercury, how acid dilution protonates the aromatic Hg-complexes and consequent release of labile forms of mercury to solution. On the basis of these results it is proposed that natural waters from mercury contaminated ecosystems should be analysed without dilutions, otherwise additional studies should be performed to access the... |
| Tipo: Article |
Palavras-chave: Reactive mercury; Organic matter; Flow injection; Cold vapour atomic Fluorescence Spectrometry; Natural waters. |
| Ano: 2003 |
URL: http://hdl.handle.net/10198/3954 |
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| Ramalhosa, Elsa; Pereira, Eduarda; Duarte, Armando. |
| As mercury presents high toxicity and is of great concern when dealing with protection of human health, mercury pollution related issues are the main subject of this work. At first, two general themes are discussed, namely: I) Mercury: highlights of physicochemical and biogeochemical properties of interest and of the main natural and anthropogenic metal sources; and II) Biogeochemical cycling of mercury in the water column of natural waters. Secondly, a case study performed in Ria de Aveiro (Portugal) during the last 10 years will be presented, focusing on water column processes. Ria de Aveiro is a coastal lagoon, located along the Atlantic Ocean on the north-western coast of Portugal, which was subjected to a discharge of an effluent rich in mercury from... |
| Tipo: BookPart |
Palavras-chave: Mercury; Water column; Coastal lagoon. |
| Ano: 2008 |
URL: http://hdl.handle.net/10198/3646 |
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| Ramalhosa, Elsa; Río-Segade, Susana; Pereira, Eduarda; Vale, Carlos; Duarte, Armando. |
| Mercury cycling in the water column and upper sediments of a contaminated area, the Largo do Laranjo, Aveiro (Portugal), was evaluated after determination of reactive and non-reactive mercury concentrations in the water column and pore waters of sediments, collected in several places of this bay. In the water column, reactive mercury concentrations varied between 10 and 37 pmol dm−3, the highest values being observed near the mercury anthropogenic source. However, reactive mercury was a narrowly constrained fraction of the total mercury, making up only 4–16% of the total, showing evidence of the importance of dissolved organic matter on mercury transport. In sediments, higher concentrations of mercury were also determined near industrial discharges.... |
| Tipo: Article |
Palavras-chave: Reactive mercury; Non-reactive mercury; Sediments; Pore waters; Diffusion; Largo do Laranjo. |
| Ano: 2006 |
URL: http://hdl.handle.net/10198/1123 |
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| Ramalhosa, Elsa; Río-Segade, Susana; Pereira, Eduarda; Vale, Carlos; Duarte, Armando. |
| A simple and rapid microwave-assisted alkaline digestion procedure was developed in combination with high performance liquid chromatography-ultraviolet post-column oxidation-cold vapour atomic fluorescence spectrometric detection for methylmercury determination in biological tissues. Since the stability of methylmercury in methanolic potassium hydroxide solution under microwave irradiation was verified, the microwave-assisted extraction procedure was optimized in terms of quantitative recovery of methylmercury and minimum time required. The alkaline extracts were subjected to clean-up steps with dichloromethane and hydrochloric acid in order to reduce matrix interferences in methylmercury determination. The effects of matrix interferences were checked by... |
| Tipo: Article |
Palavras-chave: Methylmercury; Microwave treatment; Biological samples; HPLC-CV-AFS. |
| Ano: 2001 |
URL: http://hdl.handle.net/10198/3950 |
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| Ramalhosa, Elsa; Río-Segade, Susana; Pereira, Eduarda; Vale, Carlos; Duarte, Armando. |
| A simple and rapid procedure for methylmercury extraction from sediments based on microwave-assisted alkaline digestion with methanolic potassium hydroxide was optimized on parameters such as microwave power, extraction time and sample size. Organomercury species were extracted with dichloromethane in hydrochloric acid medium and back-extracted into ultra-pure water. The sediment extracts were injected into an analytical system composed of high-performance liquid chromatography-ultraviolet-post-column oxidation-cold vapour-atomic fluorescence spectrometry (HPLC-UV-PCO-CV-AFS) for methylmercury determination. Quantitative methylmercury recoveries were obtained when 0.15 g of sediment were suspended into 6 mi of 25% m/v methanolic potassium hydroxide and the... |
| Tipo: Article |
Palavras-chave: Methylmercury; Microwave-assisted extraction; HPLC-CV-AFS. |
| Ano: 2001 |
URL: http://hdl.handle.net/10198/3941 |
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| Ramalhosa, Elsa; Río-Segade, Susana; Pereira, Eduarda; Vale, Carlos; Duarte, Armando. |
| Surface sediments and sediment cores were collected in a mercury (Hg)- contaminated lagoon, namely Largo do Laranjo – Ria de Aveiro, Portugal and analysed in order to establish the monomethylmercury (MeHg) behaviour in this kind of environment. In surface sediments, this compound was only detected in one place (13.2 ng g-1 (dry weight)). In this site, it was determined one of the lowest redox potentials (22 mV), indicative of oxic/anoxic conditions, which favours Hg methylation by enhancing the sulphate-reducing bacteria activity. However, the MeHg percentage obtained was low, namely less than 0.1% of the total Hg. This is probably due to Hg deposition with organic matter and iron oxyhydroxides, decreasing Hg availability to methylation. At the deeper... |
| Tipo: Article |
Palavras-chave: Monomethylmercury; Total mercury; Acid volatile sulphides; Organic matter; Iron species; Portugal. |
| Ano: 2011 |
URL: http://hdl.handle.net/10198/3653 |
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| Ramalhosa, Elsa; Monterroso, Paulo; Abreu, Sizenando; Pereira, Eduarda; Vale, Carlos; Duarte, Armando. |
| Mercury has been determined in water, suspended particulate matter (SPM) and sediments (solid fraction and pore water) collected in a heavily contaminated confined area (Largo do Laranjo) of the Ria de Aveiro. Mercury has been analysed in seabass (Dicentrarchus labrax) captured in several locations of the lagoon. The levels of mercury in water and SPM in the contaminated sampled places fluctuated daily with the tide (from 10 to 53 ng.dm-3 and 3.5 to 26 ug.g-1, respectively), indicating the export at the tidal rhythm. Bottom sediments exhibited higher concentrations, the maximum (48 ug.g-1) occurring near the anthropogenic source at depths corresponding to the periods of higher industrial discharges. Mercury concentrations in pore waters (max. 80 ng.dm-3)... |
| Tipo: Article |
Palavras-chave: Fishes; Mercury; Pore water; Salt marshes; Sediments. |
| Ano: 2001 |
URL: http://hdl.handle.net/10198/3899 |
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