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31. Incidence of the Winemaking Technique on Metal Content and Phenolic Composition of Red Wines.

Author

Soto Vázquez, Elvira, Rio Segade, Susana, and Fernández Gomez, Esperanza

Subjects
*WINES, *METAL analysis, *PHENOLIC acids, *RED wines, *DISCRIMINANT analysis, *LINEAR free energy relationship, *POTASSIUM, *FLAVANOLS
Abstract

The influence of different winemaking techniques usually used to elaborate red wines (Ganimede, prefermentative maceration, pectolytic enzymes and tannins addition, oak chips addition, delestage, and conventional procedure) on the metal content was evaluated. Linear discriminant analysis was also used to characterize the respective wines based on the metal content. By using iron, manganese, and calcium as chemical descriptors, the six winemaking techniques were perfectly discriminated. As the phenolic composition is an important quality factor in red wines, a correlation study between phenolic compounds and metals was also performed. A good correlation has been found for iron, calcium, and potassium with total polyphenols, tannins, and flavanols reactive. Iron, zinc, calcium, and potassium showed a significant correlation with anthocyanin compounds. Furthermore, higher concentrations of iron and calcium, but lesser ones of potassium, permitted to obtain red wines with a greater chromatic intensity. [ABSTRACT FROM PUBLISHER]

Published
2013
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32. Monomethylmercury behaviour in sediments collected from a mercury-contaminated lagoon.

Author

Ramalhosa, Elsa, Rio Segade, Susana, Pereira, Maria Eduarda, Vale, Carlos, and Duarte, Armando

Subjects
*MERCURY in soils, *MERCURY poisoning, *LAKE sediments, *LAGOONS, *SULFIDES, *ORGANIC compounds, *IRON
Abstract

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 layers, MeHg was also determined, reaching 46.4 ng g-1 (dry weight) and representing less than 0.1% of the total Hg. The higher MeHg percentages were observed near the surface, where Hg seems to be faster methylated as a result of the lower sulphide concencentrations that render bioavailable the inorganic Hg. At depth the low MeHg percentages obtained are due to the formation of HgS and to the adsorption of Hg to iron monosulphides. [ABSTRACT FROM AUTHOR]

Published
2011
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33. Effect of Organic Matter on Determination of Reactive Mercury in Contaminated Waters.

Author

Ramalhosa, Elsa, Rio Segade, Susana, Pereira, Eduarda, Vale, Carlos, and Duarte, Armando

Subjects
*FLOW injection analysis, *FLUORESCENCE spectroscopy, *PROTON transfer reactions
Abstract

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 protonation of mercury organic complexes. [ABSTRACT FROM AUTHOR]

Published
2003
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