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Registros recuperados: 13
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Accumulation versus remobilization of mercury in sediments of a contaminated lagoon IPB - Escola Superior Agrária
Ramalhosa, Elsa; Pato, P.; Monterroso, Paulo; Pereira, Eduarda; Vale, C.; Duarte, A.C..
This work discusses the extent of sediment mercury retention in the most contaminated sites in the lagoon, and its exportation to the water column as well as transfer to biogenic suspended particles and to sea bass (Dicentrarchus labrax). Therefore,the main question, with important environmental management implications, was to assess if mercury is effectively retained in the sediments or is progressively released to the water column in considerable amounts.
Tipo: Article Palavras-chave: Mercury; Sediments; Accumulation; Remobilization.
Ano: 2006 URL: http://hdl.handle.net/10198/3956
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Distribution of mercury in the upper sediments from a polluted area (Ria de Aveiro, Portugal) IPB - Escola Superior Agrária
Ramalhosa, Elsa; Pereira, Eduarda; Vale, C.; Válega, M.; Duarte, A.C..
This work reports levels of Hg, Fe and Mn and sulphides in the upper sediments of the Laranjo Basin, and examines the influence of these elements on the distribution of mercury.
Tipo: Article Palavras-chave: Mercury; Sediments.
Ano: 2005 URL: http://hdl.handle.net/10198/3360
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Effect of organic matter on determination of reactive mercury in contaminated waters IPB - Escola Superior Agrária
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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Mercury behaviour in the water column of an impacted coastal lagoon: Ria de Aveiro (Portugal) as a case study IPB - Escola Superior Agrária
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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Mercury cycling between the water column and surface sediments in a contaminated area IPB - Escola Superior Agrária
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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Mercury cycling between water column and upper sediments in a contaminated area (Largo do Laranjo, Aveiro, Portugal) IPB - Escola Superior Agrária
Ramalhosa, Elsa; Río-Segade, Susana; Pereira, Eduarda; Vale, Carlos; Armando, Duarte.
The fate and reactivity of anthropogenic mercury in aquatic environment is of major concern owing to its toxicity to most organisms and man. In Ria de Aveiro, a chloralkali plant has been discharging mercury during decades into one of the remotest branches. Most of the discharged mercury settles down in Largo do Laranjo, an inner bay of 1.5 km'. Since 80's, several works have identified high mercury concentrations in sediments, suspended particulate matter and water [I, 2, 3]. The highest concentrations of mercury (max. 35 Og g") were found in sediments at 40 cm depth, corresponding to the period of maximum industrial production [2]. However, there is an escape of particulate mercury when surface sediments are resuspended and transported by the tide to the...
Tipo: ConferenceObject Palavras-chave: Mercury; Water column; Sediments; Cycling.
Ano: 2004 URL: http://hdl.handle.net/10198/3655
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Mercury distribution in Douro estuary (Portugal) IPB - Escola Superior Agrária
Ramalhosa, Elsa; Pereira, Eduarda; Vale, C.; Válega, M.; Monterroso, Paulo; Duarte, A.C..
Determinations ofdissolved reactive and total dissolved mercury, particulate and sedimentary mercury, dissolved organic carbon (DOC), particulate organic carbon (POC) and suspended particulate matter (SPM) have been made in the estuary ofriver Douro, in northern Portugal. The estuary was stratified by salinity along most ofits length, it had low concentrations of SPM, typically <20 mg dm-3, and concentrations of DOC in the range <1.0–1.8 mg dm-3. The surface waters had a maximum dissolved concentration of reactive mercury of about 10 ng dm-3, whereas for the more saline bottom waters it was about 65 ng dm-3. The surface waters had maximum concentrations oftotal suspended particulate mercury of ~7 ug g-1 and the bottom waters were always < l ug...
Tipo: Article Palavras-chave: Mercury; Estuaries; Partitioning; Dissolved Organic Carbon; SPM.
Ano: 2005 URL: http://hdl.handle.net/10198/3372
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Microwave treatment of biological samples for methylmercury determination by high-performance liquid chromatografy – cold vapour - atomic fluorescence spectrometry IPB - Escola Superior Agrária
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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Microwave-assisted extraction for methylmercury determination in sediments by high performance liquid chromatography-cold vapour-atomic fluorescence spectrometry IPB - Escola Superior Agrária
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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Mobility of contaminants in relation to dredging operations in a mesotidal estuary (Tagus Estuary, Portugal) IPB - Escola Superior Agrária
Vale, Carlos; Ferreira, Ana; Micaelo, Cristina; Caetano, Miguel; Pereira, Eduarda; Madureira, Maria; Ramalhosa, Elsa.
During the construction of a New Bridge over the Tagus estuary 2.5 million tons of sediments were dredged, part of this quantity being contaminated material. The extension and intensity of the water turbidity associated with dredging operating varied with the tidal conditions but the resuspended material collected near the bucket dredger did not present a concentration increment in metals and PCB, when compared to the estuarine suspended sediments. The calculated distribution coefficients suggest that some contaminants in solids near the dredger were not in equilibrium with the water. A 24-hour laboratory experiment demonstrated the complexity and quickness of anoxic sediments oxidation. In such a short period of time metals in the solids change their...
Tipo: Article Palavras-chave: Dredging operations; Mesotidal estuary; Metals; PCB congeners; Suspended sediments; Turbidity.
Ano: 1998 URL: http://hdl.handle.net/10198/3940
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Monomethylmercury behaviour in sediments collected from a mercury-contaminated lagoon IPB - Escola Superior Agrária
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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Simple methodology for methylmercury and inorganic mercury determination by high performance liquid chromatography-cold vapour atomic fluorescence spectrometry IPB - Escola Superior Agrária
Ramalhosa, Elsa; Río-Segade, Susana; Pereira, Eduarda; Vale, Carlos; Armando, Duarte.
An analytical methodology was developed to separate and quantify methylmercury (MeHg) and inorganic mercury by high-performance liquid chromatography (HPLC)-cold vapour atomic fluorescence spectrometry (CV-AFS). The use of UV oxidation of the organic forms of mercury, the tin(II) chloride reduction in acidic medium of mercury and the introduction of a water vapour trap based on H2SO4/CaCl2 resulted in a low detection limit (DL) (10 +/- 2 pg, mean value +/- S.D.). The apparatus was operationally optimised through the modified simplex method leading to an increase of the signal by a factor of 2. The method performance has been tested by determining the MeHg concentration in a sediment certified reference material (CRM) and the results were statistically...
Tipo: Article Palavras-chave: Methylmercury; Cold vapour atomic fluorescence spectromety; Liquid chromatography; UV radiation; Simplex optimisation.
Ano: 2001 URL: http://hdl.handle.net/10198/3946
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Storage and export of mercury from a contaminated bay (Ria de Aveiro, Portugal) IPB - Escola Superior Agrária
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
Registros recuperados: 13
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