Kinetic effects on the interactions of Rh(III) with humic acids as determined using size exclusion chromatography (SEC)

10 páginas, 6 figuras.-- The original publication is available at www.springerlink.comThe anthropogenic inputs of Rh in the environment— together with other platinum group elements— have increased considerably during the last 20–30 years. However, thermodynamics and kinetics on the interaction of Rh with natural organic and inorganic ligands are still poorly characterized. Here, we report the time-dependent speciation of rhodium chlorides spiked to model freshwater with and without the presence of humic substances. Rhodium species were determined using size-exclusion chromatography-inductively coupled plasma mass spectrometry (SEC-ICP-MS). Results indicate that organic matter can effectively bind rhodium, but the extremely slow reaction kinetics of Rh plays a significant role on its speciation in natural waters. Accordingly, formation of Rh-organic complexes from spiked rhodiumchlorides required around 15 days to reach equilibrium; this should be taken into account in those laboratory experiments where the biological interactions of Rh, using spiked samples, are studied. Regarding Rh inorganic speciation in freshwater, the available thermodynamic constants predict the dominance of the neutral trihydroxo and negatively charged tetrahydroxo rhodium complexes over typical pHs (6–8); our results, however, indicate only the presence of negatively charged hydroxocomplexes at pH 7. Reexamination of the Rh stability constants suggest that these hydroxylated rhodium complexes may also dominate its inorganic speciation in seawater.We gratefully acknowledge the financial support by the European Union under the Marie Curie fellowship scheme (contract no. MEIF-CT-2005-009152) and the P.I. project (ref. 2008830I150) from the CSIC (Consejo Superior de Investigaciones Científicas) granted to A.C.G.Peer reviewe

Improvement of the ultra-trace voltammetric determination of Rh in environmental samples using signal transformation

En prensa3,498

Obtención de la capacidad de carga en cimentaciones para un suelo parcialmente saturado empleando métodos analíticos

The study of the behavior of unsaturated soils has been the subject ofseveral studies in recent years. The objective of this paper is to summarizethe main aspects and different theories established by reference authors,used to estimate bearing capacity of unsaturated soils. The variationin the bearing capacity of a square shaped foundation surface: sides B= L 1.5 m is obtained, using the approach proposed by Brinch-Hansenconsidering the formulations offered by Fredlund and Vanapalli toestimate the unsaturated soil strength parameters (c and φ). Each ofthe reviewed formulations suggests a law of variation of cohesionvalues depending on the unsaturated suction function. A comparisonof the behavior between the unsaturated and the saturated phases, isperformed, using different values of matric suction obtained by meansof the soil retention curve of Formation Capdevila.El estudio del comportamiento de los suelos parcialmente saturadosha sido motivo de diversos estudios en los últimos años. La presenteinvestigación se encarga de resumir los principales aspectos y diferentesteorías enunciadas por varios autores para estimar capacidadde carga de los suelos parcialmente saturados. Se obtiene la variaciónde la capacidad de carga de una cimentación superficial cuadrada delado B y L de 1.5 m, empleándose la formulación propuesta por Brinch-Hansen, y tomando en consideración las formulaciones propuestas porFredlund y Vanapalli, para estimar los parámetros de resistencia delsuelo parcialmente saturado (c y φ). Estas formulaciones proponen unaley de variación de los valores de cohesión de un suelo parcialmentesaturado en función de la succión que este pueda experimentar. Serealiza la comparación entre el comportamiento en la fase saturada yla fase parcialmente saturada, empleando diferentes valores de succiónmatricial obtenidos por medio de la curva de retención del suelo de laFormación Capdevila

Platinum in salt marsh sediments: Behavior and plant uptake

En prensa2,751

Two opposite cases of metal accumulation in ria sediments: Ferrol and Corme-Laxe (Galicia, NW Iberian Peninsula)

The accumulation of heavy metals (Cd, Cu, Pb and Zn) in surface sediments (<63 µm) of the Ferrol and Corme-Laxe rias was studied. These two rias have opposite characteristics from the point of view of both the morphology and the anthropogenic impact. Low metal concentrations were found in the Corme-Laxe Ria, with the highest values observed in the Anllóns River estuary, probably due to a higher lithogenic composition of the sediments. Concentrations in the Corme-Laxe Ria (Cd, 0.10 ± 0.03 µg g–1; Cu, 5 ± 2 µg g–1; Pb, 12 ± 4 µg g–1; and Zn, 49 ± 17 µg g–1) can be used as a good reference for metal background values for sediments from the 18 Galician rias. Although these background values are lower than those previously reported for the Galician coast, they are similar to those found in other uncontaminated coastal and marine systems. The highest concentrations for Ferrol were generally found in the middle part of the ria, which receives the most important urban and industrial impact. The values obtained show evident metal contamination in the middle and inner parts of the Ferrol Ria, with enrichment factors of 4–10 for Cd, 5 for Cu, 2–3 for Pb and 4–5 for Zn

Macroelements and Trace Elements Content in Brine-Canned Mackerel (Scomber colias) Subjected to High-Pressure Processing and Frozen Storage

This study analysed the effect of prior high-pressure processing (HPP; 200–600 MPa, 2 min), freezing (−30 °C, 48 h), and frozen storage (−18 °C, 6 months) on the macroelement and trace element content in brine-canned mackerel (Scomber colias). Most elements (Na, Ca, Ba, Mn, Fe, Cu, Cd, Sn, As, S, and Se) showed an increased (p < 0.05) presence in mackerel muscle canned after freezing. A content increase (p < 0.05) was also observed for Na and Sn if prior frozen storage was also applied; on the contrary, Ca, Ba, Mn, Fe, Cd, S, and Se showed a content decrease (p < 0.05) as a result of such storage. Freezing, frozen storage, and canning led to lower values (p < 0.05) in canned fish for K, Mg, Pb, and P. Prior HPP led to relevant content decreases (p < 0.05) for K, Mg, Ca, Ba, Mn, Fe, Pb, and P contents in fish canned after the freezing step; HPP provoked additional decreases (p < 0.05) in Ca, Ba, and Mn levels in samples corresponding to 6-month frozen storage. On the contrary, prior HPP led to marked increases (p < 0.05) for Cd, S, and Se contents in all canned samples. Content changes are explained on the basis of modifications of other constituents and liquor losses from muscleThis study was supported by the Spanish “Consejo Superior de Investigaciones Científicas (CSIC)” (Research Project 2017-70E032)S

Intercambio estuario-ría de elementos traza en el sistema costero de la ría de Vigo (NO Península Ibérica)

[EN] Little research has been done on the land-sea exchange of trace elements, which is particularly applicable to ria coasts. In particular, trace metal enrichment in the inner part of the Ria of Vigo (the San Simon Inlet) has been observed from sediment studies but there is no information about Cd, Pb and Zn fluxes through the Rande Strait, which is the natural boundary of the estuary-ria water exchange. In order to assess metal exchanges in a ria-type system, six sampling cruises on board the R/V Mytilus (IIM-CSIC) were carried out. Water column profiles of salinity, temperature and tidal currents were obtained every 30 min. The water column for dissolved and particulate metals was sampled every two hours over a complete tidal cycle. Dissolved metal concentrations were 0.01–0.18 nM for Cd, 0.5-1.9 nM for Pb and 4-44 nM for Zn. Compared with Zn (16±12%) and especially with Cd (5.4±5.0%), particulate metal represented a significant fraction of the total concentration for Pb (41±21%). Net fluxes of dissolved Cd and Zn are higher than in the particulate phase, whereas for Pb an inverse situation was observed. The net metal exchange in the Vigo estuary-ria environment was not seasonally controlled. Dissolved Cd and Pb were driven by tidal ranges and particulate Pb by the Oitavén River flow. On the other hand, Zn did not show a defined trend. The budgets obtained for the Ria of Vigo, with the exception of Pb, were one or two orders of magnitude lower than those measured in other large European estuaries[ES] Intercambio estuario-ría de elementos traza en el sistema costero de la ría de Vigo (NO península Ibérica). – Existen pocos estudios sobre los elementos traza en el intercambio tierra-océano, lo que es especialmente aplicable a las zonas costeras de las rías. En particular, respecto a la ría de Vigo se ha observado un enriquecimiento de metales traza en sedimentos pero se carece de información acerca de los flujos de Cd, Pb y Zn a través del estrecho de Rande, que es la frontera natural para el intercambio estuario-ría. A fin de evaluar este tipo de intercambios se realizaron seis campañas oceanográficas a bordo del B/I Mytilus (IIM-CSIC) para cuantificar los flujos de Cd, Pb y Zn en diferentes estaciones del año. Se obtuvieron perfiles verticales de salinidad, temperatura y corrientes cada 30 min en el centro del estrecho de Rande durante un ciclo de marea. Además, se recogieron muestras de agua en cuatro niveles cada 2h. Las concentraciones de metales disueltos oscilaron entre 0.01 y 0.18 nM para Cd, 0.5 y 1.9 nM para Pb y 4 y 44 nM para Zn. Los metales particulados supusieron una fracción pequeña respecto del contenido total de metal (5.4±5.0% para Cd y 16±12% para zinc) salvo para el plomo (41±21%). Los flujos netos de Cd y Zn disuelto fueron superiores a los del particulado mientras que para Pb ocurrió lo contrario. El intercambio de metales en el entorno estuario-ría no parece depender de las estaciones del año sino de la altura de la marea en el caso de Cd y Pb disuelto y del caudal fluvial para Pb particulado mientras que Zn no presentó una tendencia definida. Excepto para Pb, los balances obtenidos son de uno a dos órdenes de magnitud inferiores a los de otros estuarios europeos.Peer reviewe

Evidence of increased anthropogenic emissions of platinum: time-series analysis of mussels (1991-2011) of an urban beach

En prensa3,258