Trace metal distribution in muddy-patch sediments from the northern Portuguese Shelf

Trace metal distribution in muddy-patch sediments from the northern Portuguese Shelf

Three sediment cores were collected in the muddy patches of the northern Portuguese Shelf located offshore the Douro and Minho rivers. Bivalves and worms were found in the upper and sub-surface layers of two cores. Vertical distributions of dissolved manganese and iron, iron oxides and acid volatile...

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Autores principales: Madureira, MJ, Vale, C, Fonseca, N
פורמט: Online
שפה:eng
יצא לאור: Iniversidad Autónoma de Baja California 2003
גישה מקוונת:https://www.cienciasmarinas.com.mx/index.php/cmarinas/article/view/172
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spelling oai:cienciasmarinas.com.mx:article-1722019-04-24T19:17:35Z Trace metal distribution in muddy-patch sediments from the northern Portuguese Shelf Distribución de metales traza en sedimentos de zonas de lodo de la plataforma costera norte de Portugal Madureira, MJ Vale, C Fonseca, N trace metals sulphides early diagenesis northern Portuguese Shelf metales traza sulfuros diagenesis temprana plataforma norte de Portugal Three sediment cores were collected in the muddy patches of the northern Portuguese Shelf located offshore the Douro and Minho rivers. Bivalves and worms were found in the upper and sub-surface layers of two cores. Vertical distributions of dissolved manganese and iron, iron oxides and acid volatile sulphide (AVS) in the bioturbated cores differ dramatically from those in the core where macrofauna was not observed. Also, Fe, Zn, Cu, Pb and Cd simultaneously extracted with AVS (1 M HCl) showed pronounced increases in concentrations deeper in the sediments. Where bioturbation was not visible the profiles of extractable Cu, Pb and Cd are consistent with the precipitation of downward diffusing dissolved metals. However, this redistribution did not affect the metal-total vertical profiles. Reactive metals exhibited multiple peaks in the irrigated sub-surface layers where AVS and dissolved Fe showed successive maxima and minima with the depth. We interpreted these profiles as the net result of dissolved oxygen being pumped into the sediment and the formation of several oxic/anoxic interfaces. At these depths trace metals are mobilized in the oxidized layers, diffused a few millimetres towards the layers where sulphide is present, and precipitated. The consequence of this internal redistribution was the broad maxima of total metal concentrations in irrigated sediment depths. Se muestrearon tres testigos de sedimento en manchas de lodo procedentes de la plataforma continental del norte de Portugal localizadas frente a los ríos Duero y Miño. En las capas superficial y subsuperficial de dos de los testigos se encontraron bibalvos y gusanos. Las distribuciones verticales de hierro y manganeso disueltos, óxidos de hierro y sulfuros volátiles ácidos (AVS) en los testigos bioperturbados son drásticamente diferentes de aquellos en los que no se observó macrofauna alguna. De igual forma, el Fe, Zn, Cu, Pb y Cd extraídos simultáneamente con los AVS (HCl 1M), mostraron incrementos marcados en la concentración en zonas más profundas del sedimento. Donde la bioperturbación no fue visible, los perfiles de Cu, Pb y Cd extraíbles concuerdan con la precipitación y los metales disueltos con difusión descendente. Sin embargo, esta redistribución no afectó los perfiles verticales de metales totales. Los metales reactivos mostraron picos múltiples en capas irrigadas sub-superficiales donde los AVS y el Fe disuelto presentaron máximos y mínimos sucesivos con la profundidad. Interpretamos estos perfiles como el resultado neto del bombeo de oxígeno disuelto hacia el sedimento y la formación de varias interfases óxicas-anóxicas. En estas profundidades, los metales traza son movilizados en las capas oxidadas, y difundidos unos pocos milímetros hacia las capas donde hay sulfuro y éste precipita. La consecuencia de esta redistribución interna determina el máximo de las concentraciones totales de metales en profundidades con sedimentos irrigados. Iniversidad Autónoma de Baja California 2003-03-06 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Peer-reviewed Article Artículo Arbitrado application/pdf https://www.cienciasmarinas.com.mx/index.php/cmarinas/article/view/172 10.7773/cm.v29i4.172 Ciencias Marinas; Vol. 29 No. 4 (2003); 435-445 Ciencias Marinas; Vol. 29 Núm. 4 (2003); 435-445 2395-9053 0185-3880 eng https://www.cienciasmarinas.com.mx/index.php/cmarinas/article/view/172/147
institution Ciencias Marinas
collection OJS
language eng
format Online
author Madureira, MJ
Vale, C
Fonseca, N
spellingShingle Madureira, MJ
Vale, C
Fonseca, N
Trace metal distribution in muddy-patch sediments from the northern Portuguese Shelf
author_facet Madureira, MJ
Vale, C
Fonseca, N
author_sort Madureira, MJ
title Trace metal distribution in muddy-patch sediments from the northern Portuguese Shelf
title_short Trace metal distribution in muddy-patch sediments from the northern Portuguese Shelf
title_full Trace metal distribution in muddy-patch sediments from the northern Portuguese Shelf
title_fullStr Trace metal distribution in muddy-patch sediments from the northern Portuguese Shelf
title_full_unstemmed Trace metal distribution in muddy-patch sediments from the northern Portuguese Shelf
title_sort trace metal distribution in muddy-patch sediments from the northern portuguese shelf
description Three sediment cores were collected in the muddy patches of the northern Portuguese Shelf located offshore the Douro and Minho rivers. Bivalves and worms were found in the upper and sub-surface layers of two cores. Vertical distributions of dissolved manganese and iron, iron oxides and acid volatile sulphide (AVS) in the bioturbated cores differ dramatically from those in the core where macrofauna was not observed. Also, Fe, Zn, Cu, Pb and Cd simultaneously extracted with AVS (1 M HCl) showed pronounced increases in concentrations deeper in the sediments. Where bioturbation was not visible the profiles of extractable Cu, Pb and Cd are consistent with the precipitation of downward diffusing dissolved metals. However, this redistribution did not affect the metal-total vertical profiles. Reactive metals exhibited multiple peaks in the irrigated sub-surface layers where AVS and dissolved Fe showed successive maxima and minima with the depth. We interpreted these profiles as the net result of dissolved oxygen being pumped into the sediment and the formation of several oxic/anoxic interfaces. At these depths trace metals are mobilized in the oxidized layers, diffused a few millimetres towards the layers where sulphide is present, and precipitated. The consequence of this internal redistribution was the broad maxima of total metal concentrations in irrigated sediment depths.
publisher Iniversidad Autónoma de Baja California
publishDate 2003
url https://www.cienciasmarinas.com.mx/index.php/cmarinas/article/view/172
_version_ 1715723938771763200

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