Fernando Fraga Rodríguez (Santiago de Compostela, 1922 – Vigo, 2020)

4 pagesPeer reviewe

Trace element patterns in heterogeneous land–sea sediments: a comprehensive study of the Ulla–Arousa system (SW Europe)

In the continuum of the land–sea interface, sediment reservoirs are often considered separately. Therefore, integrative research is necessary. This study focuses on sediments throughout the tributaries–river–estuary–ria pathway of the Ulla–Arousa system, aiming to quantify trace element contents, identify land sources, determine background levels, and assess sediment enrichment and contamination states. The elements Al, As, Cr, Cu, Fe, Ni, Pb, Sb, U, and Zn were determined in 78 sediment stations. Two approaches were considered. First, background functions and enrichment factors were estimated using Al or U as the reference element. Second, a statistical study was conducted using distribution analysis, which helped identify trace element sources and their influences throughout the basin. The results revealed two significant sources of trace elements. One source is the amphibolite massif of the Arinteiro Unit, influencing the Brandelos (Cu) and Lañas (Fe) tributaries. Another source is the Deza tributary (As, Sb). However, these alterations do not reach the estuary, where anthropogenic sources (Cr, Cu, Ni) dominate. In the inner Ria of Arousa, only a light Cr enrichment was observed. The integrated study of the Ulla–Arousa system provides valuable patterns to understand and address heterogeneous land–sea systems.Consejo Superior de Investigaciones Científicas | Ref. 20181970Xunta de Galicia | Ref. IN607A2021/04Xunta de Galicia | Ref. ED481D 2023/006Consejo Superior de Investigaciones Científicas | Ref. JAEICU-20-IIM-0

Background of u and th in sediments of bedrock rivers

The Miño River is a good example of bedrock rivers, where sediment geochemistry is scarcely studied. Its urban reach when passing through the city of Ourense gathers some characteristics that provide interest to its sediments, like scarcity of fine sediments accumulation and the impact of several human activities. Sediments trapped by potholes and other rock cavities were considered. In order to evaluate society-nature interactions through sediment composition it is critical to determine the compositional background (in absence of human alterations), particularly when working with trace elements. This work presents an exploratory assay to determine background in sediments from bedrock rivers by using two uncommon elements, uranium (U) and thorium (Th). To determine their background different statistical techniques were applied in order to set the background composition value and calculate possible enrichments. Background was calculated by simple least squares lineal regression by using Al as independent variable (reference element) resulting in 8.7 mgU kg-1 and 5.6 mgTh kg-1. Enrichments were found in some particular samples and can be attributed to intrinsic microenvironment complexities inside rock cavities

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

Hydrography of the Pontevedra Ria: Intra-annual spatial and temporal variability in a Galician coastal system (NW Spain)

In order to ameliorate the dearth of existing scientific knowledge concerning the hydrography of the Pontevedra Ria, a systematic investigation was carried out between October 1997-98. Salinity variations were closely related to river discharge whereas bottom waters presented oceanic characteristics over the whole year. Current was controlled by tide, river discharge, and wind in the internal ria where the highest velocities were directed along the ria channel with a low transverse component. Favorable atmospheric conditions in spring induced coastal upwelling up the continental shelf. In May the upwelling was sufficiently strong to be detected in the inner ria and intensified in July and August, cooling the ria water to 12 degrees -14 degreesC. Upwelling ceased in September, and from November to March seawater transported by the poleward current (35.9; 15 degreesC) was detected on the shelf. From January until March, unanticipated favorable upwelling conditions provoked an influx of poleward inside the ria. Ria intrusion of poleward water and association with occasional winter upwelling conditions has not been observed previously. Isopycnic three-dimensional (3-D) surface and 2-D isopycnal maps show that with high river runoff or intense upwelling, lower-salinity water leaves the ria near the northern margin in the surface layer. Under negative upwelling conditions, the water is partially dammed inside the ria and exits the ria when the wind speed falls. During upwelling events, ENACW penetrated the ria, especially near the southern shore. Arrival of ENACW at the northern entrance impedes the outward water flow through this mouth

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

Industrial supply of trace elements during the “Anthropocene”: a record in estuarine sediments from the Ria of Ferrol (NW Iberian Peninsula)

This work addresses the study of a sediment core retrieved in the estuary of the Grande-de-Xubia River (Ria of Ferrol), which is among the first industrialized areas in the Iberian Peninsula and has links to the shipbuilding industry since 1750. The chemical analysis of trace elements (i.e. As, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, V, and Zn) was coupled with 210Pb dating. The results span a period of about 130 years and cover the whole of the 20th century. Trace element anthropogenic fluxes accumulating in the sediments were calculated and show that human inputs are the most important sources for Cu, Cd, Hg and Zn, being, on average, well over the natural loads. The temporal variation in the anthropogenic contaminants allows the identification of four main phases describing the human-natural input interactions, which in chronological order, are: (i) early industrialization, (ii) industrial acceleration or first industrial transition, (iii) industrial collapse, and (iv) an industrial maturity or a second industrial transition.Ministerio de Ciencia e Innovación | Ref. CTM 2011-28792-C02-02Xunta de Galicia | Ref. ED481B-2019-06

Distinctive accumulation patterns of trace elements in sediments of bedrock rivers (Miño river, NW Iberian Peninsula)

Sediment compositions and enrichment patterns are investigated in an urban reach of a bedrock river, the Miño River passing through Ourense City, Spain. This study focuses on the trace element distribution in different fractions to gain insights into trace element enrichment. To assess enrichment, a context-specific approach was employed, based on the mean, the standard deviation of the estimated background, and the empirical rule, avoiding the pitfalls of general and arbitrary thresholds. Notably, the <0.063 mm and <2 mm fractions showed differential accumulation patterns. Both fractions serve to detect enrichments that can be indicative of contamination, but they measure different things, the maturity of sediments and postdepositional processes being key factors in understanding the sediment composition and enrichments. These findings also highlight the role of rock cavities, particularly those hosting permanent deposits, as traps for trace elements and their potential significance in assessing environmental enrichment. This work contributes to understanding sediment compositions and enrichment dynamics in bedrock rivers. It also underscores the significance of considering site-specific approaches for enrichment assessment and the necessity for further research to unravel the mechanisms driving differential accumulation within distinct depositional environments.Universidade de Vigo | Ref. INOU15-02Deputación de Ourense | Ref. INOU15-02Xunta de Galicia | Ref. ED481D-2023/00

Especiación del Pb en aguas de las Rías bajas Gallegas: puesta a punto de un método voltamperométrico y primeros resultados

El Pb no es un elemento esencial desde el punto de vista biológico, pero su estudio es importante debido a sus efectos tóxicos resultado de su entrada en los ecosistemas acuáticos principalmente por actividades antropogénicas, cuyo flujo se ha estimado en 1,38•108 kg a-1. La extensa costa gallega con 1720 km. de litoral y abundantes aportes de pequeños ríos es muy sensible a los efectos contaminantes de metales, que como el Pb, son transportados por vía atmosférico-fluvial. La necesidad de medidas en el medio acuático de las cabeceras de las rías se ha comenzado a abordar en trabajos como el presente que supone el primer estudio de especiación de Pb realizado en aguas de las Rías Bajas Gallegas utilizando la voltamperometría de redisolución anódica de pulso diferencial (DPASV). Esta es una técnica alternativa y complementaria a los métodos espectroscópicos. Ello es por su sensibilidad inherente y bajos límites de detección, por la precisión de los resultados y por su capacidad de abordar la especiación, a la vez que por su bajo coste y simplicidad de manejo. Se presentan a continuación los resultados del estudio de la complejación de Pb por ligandos orgánicos en dichas aguas mediante la aplicación del procedimiento de linealización propuesto por Ruzic y van den Berg