Daniel Rey

Assessment of the health quality of Ria de Aveiro (Portugal): Heavy metals and benthic foraminifera

This work analyses the distribution of heavy metals in the sediments of Ria de Aveiro (Portugal) assessed by total digestion and sequential chemical extraction of the sediments. The influence of environmental parameters on the living benthic foraminiferal assemblages was studied. The most polluted parts in the Ria de Aveiro are areas where the residence time is high and cohesive sediments are deposited. Organic matter, which is an excellent scavenger for a number of metals, is in general more abundant in the finer deposits of this lagoon, which act as sinks of anthropogenic pollutants. This condition is observed in Aveiro canals and Murtosa channel where sediments with the highest concentrations of Zn, Pb, Cu, and Cr are found. The sediments of Murtosa channel are also enriched in As, Co and Hg. In Aveiro canals the enrichment of heavy metals is mostly related to the past industrial production at their margins (ceramic and metallurgy), whereas in Murtosa channel with effluent discharges of the Chemical Complex of Estarreja. Foraminiferal density and diversity reach higher values near the lagoon mouth under higher marine influence and decline in general under very low-oxygen conditions. Some species seems to be indifferent to the increasing of TOC (e.g. Haynesina germanica and Ammonia tepida) and some have an opportunistic behaviour in areas with very depressed levels of oxygen (e.g. A. tepida and Quinqueloculina seminulum) whereas other species can better tolerate sulphide/reducing conditions (e.g. H. germanica, Bolivina ordinaria, Buliminella elegantissima, Bulimina elongata/gibba and Nonionella stella) a widespread condition in this lagoon. Foraminiferal density and some species are negatively correlated with concentrations of heavy metals. A most sensitive group of species to higher concentrations of heavy metals is identified (such as B. ordinaria, B. pseudoplicata and B. elongata/gibba) and another one of more tolerant species (such as H. germanica A. tepida and Q. seminulum). Foraminifera are more tolerate higher available concentrations (AC) of Zn in any phase than higher AC of Cu adsorbed do clay minerals (F1) and associated with Fe and Mn oxides (F2) and of Pb in F2; the phase F2, probably the most mobile phase, and even phase F1 seems to be more toxic than the increasing of metals in organic matter (F3).

Recurrent arrival of oil to Galician coast: the final step of the Prestige deep oil spill.

Yearly monitoring in one of the most affected coastal zones by the Prestige oil spill, namely Nemiña and O Rostro beaches (NW Spain), has been carried out since 2004. Topographic data of beaches revealed seasonal altimetric changes up to 4m that would prevent the on shore persistence of oil. However, surficial and subsurficial oil was detected in the intertidal area of both beaches in all campaigns. The hydrocarbon analysis confirmed that this oil corresponded to the Prestige oil, even nine years after the accident. Tar balls were highly biodegraded suggesting that the oil was accumulated on the subtidal sediments for a long time and transported to the coast by the action of waves. The present work provides new evidence of the long term persistence of deep oil spills from wrecks in marine areas where the hydrodynamic conditions play a twofold key role, in determining the exposed coastal area to recurrent contamination and in burying and resurfacing the oil in the intertidal zone.

Discrimination of biogenic and detrital magnetite through a double Verwey transition temperature

Magnetite occurs widely in natural environments in both inorganic and biogenic forms. Discrimination of the origin of magnetite has important implications, from searching for past microbial activity to interpreting paleomagnetic and environmental magnetic records in a wide range of settings. In this study, we present rock magnetic and electron microscopic analyses of marine sediments from the continental margin of Oman. Low-temperature magnetic data reveal two distinct Verwey transition (Tv) temperatures that are associated with the presence of biogenic and inorganic magnetite. This interpretation is consistent with room temperature magnetic properties and is confirmed by electron microscopic analyses. Our study justifies the use of two distinct Tv temperatures as a diagnostic signature for discriminating inorganic and biogenic magnetite. Simple low-temperature magnetic measurements, therefore, provide a tool to recognize rapidly the origin of magnetite within natural samples. In addition, our analyses reveal progressive down-core dissolution of detrital and biogenic magnetite, but with preservation of significant amounts of fine-grained magnetite within sediments that have been subjected to severe diagenetic alteration. We demonstrate that preservation of magnetite in such environments is due to protection of fine-grained magnetite inclusions within silicate hosts. Our results, therefore, also provide new insights into diagenetic processes in marine sediments.

The influence of weather and climate on the reliability of magnetic properties of tree leaves as proxies for air pollution monitoring

Monthly monitoring of magnetic properties of Platanus hispanica tree leaves was used to assess atmospheric pollution in Madrid (Spain) and its suburban town of Pozuelo de Alarcón. Magnetic susceptibility, isothermal remanent magnetisation and metal concentrations were analysed to study the sources of atmospheric pollutants and their spatial and temporal evolution. In addition to urban dust, our results indicated that lithogenic dust and incorporation of trace metals in the leaf tissue also control the magnetic susceptibility of tree leaves. Global comparisons with cities of different climatic regimes suggest that air humidity is the key factor controlling the relative influence of pollutants, lithogenic dust and biological effects on the magnetic properties of tree leaves. Interaction of the atmosphere and tree leaves depends not only on local meteorology but also on climate. Climate, especially air humidity, and meteorology need to be considered when interpreting the magnetic properties of tree leaves as an atmospheric pollution tool.

Simulating the influence of physicochemical parameters on subsurface oil on beaches: preliminary results.

Monitoring of sandy beaches after the Prestige oil spill revealed thick subsurface layers (up to 1m thick) of grey-coloured sand. These horizons were sometimes found under more than 3m of clean sand. Examination of the sand by electron microscopy confirmed that the colouring was due to oil-coated sand grains, and revealed a sequence of degradation of buried oil. Further analysis of the sand revealed high concentrations of hydrocarbon in the oil-coated sand and that the main biomarkers were indicative of biodegradation, even though the oil was buried. A set of experiments was designed to analyze the evolution of oil from tar balls to coatings. The results revealed that biodegradation is a secondary process in the changes that take place in the buried oil, and that water flow slows down the appearance of grey sand and that low salinity may hinder the oil degradation process.

Propiedades magnéticas de los sedimentos de tipo estuarino. El caso de las Rías Baixas.

Este trabajo establece la utilidad de la susceptibilidad magnetica como indicador de la influencia marina y evolucion diagenetica en sedimentos costeros de las Rias Baixas. Para ello se investigo la variabilidad geografica de la susceptibilidad en 200 muestras de sedimentos marinos superficiales en las Rias de Vigo y Pontevedra. Su variabilidad vertical se estudio en 80 muestras de tres testigos de entre 60 y 90 cm de longitud extraidos en la Ria de Pontevedra. La susceptibilidad de las muestras superficiales aumenta progresivamente hacia mar abierto, y a medida que nos alejamos de las zonas de mayor influencia continental, estando relacionada con la textura y composicion del sedimento, y por tanto, con su procedencia. Los testigos, mas homogeneos litologicamente, mostraron una disminucion muy importante de la susceptibilidad con la profundidad, estando esta asociada a la evolucion diagenetica del sedimento. Para estudiar mejor estos procesos, se determino la composicion elemental y mineralogica, y ademas se midieron otras propiedades magneticas de muestras representativas. Estos resultados se analizaron conjuntamente con los datos sedimentologicos disponibles, lo que permitio establecer que la variabilidad de 151 D. Rey et al. Propiedades magneticas de los sedimentos de tipo estuarino... la susceptibilidad dependia de tres factores principales: (a) procedencia y origen de los sedimentos, (b) regimen hidrodinamico de la zona y (c) presencia de particulas contaminantes discretas de origen antropogenico. Tambien puede concluirse que la evolucion de las fases magnetomineralogicas durante la diagenesis temprana esta controlada por el contenido en materia organica, lo que a su vez determina el potencial de oxidacion-reduccion.

The ITRAX core scanner, a useful tool to distinguish anthropic vs. climatic influences in lagoon of Aveiro (N Portugal)

ABSTRACT Martins, V. A., Dias, J. A., Bernardes, C., Rubio, B., Bernabeu, A., , Rey, D., Soares, A.M., Sobrinho, F., Laut, L.M., Frontalini, F., Terroso, D., Miranda, P., Fernández-Fernández. S., Rodrigues, M.A., Figueira, R., Sousa, S.M., Amaral, P. Mahiques, M. and Rocha, F., 2013. The ITRAX core scanner, an useful tool to distinguish anthropic vs climatic influences in lagoon of Aveiro (N Portugal). The main goal of this work is to distinguish anthropic and climatic influences in sediments from the lagoon of Aveiro (Portugal). This study is based on a core (240-cm long) collected in Murtosa Channel. Optical and X-radiographic images and high-resolution elemental profiles were acquired with ITRAX micro-X-ray fluorescence (XRF) core scanner. Samples collected at each ≈3 cm along the core were analysed for grain size and total organic carbon. Furthermore, the fine fraction of selected layers was subjected to geochemical analysis by ICP-MS, after total acid digestion of the sediments, and mineralogical analysis, by XRD techniques. A radiocarbon age was determined by AMS, using molluscs shells collected at a depth of 90 cm. Sediments along the core are composed by fine and medium sand, with several mud layers. Sediments composing the first 100-cm may have been deposited after 1950, as it is indicated by the radiocarbon data, the increasing trend of Zn/Al, Pb/Al and Cu/Al and total concentrations of Zn, Pb, Cu, V, Cr, As and Ni in this interval that therefore might be linked with industrial activities of Chemical Complex of Estarreja. The progressive increase of Si/Al, Cl/Al, Rb/Al, K/Al and Br/Al and reduced Al concentrations, from the base to the top of this core, are interpreted as being related to higher marine influence and greater differences in tidal currents with longer exposition to air of the sediments with the consequent formation of brines favouring minerals precipitation in the area (e.g. anhydrite). These results seem to be a consequence of several works developed over time like: i) dredging to improve the navigation access to the harbour, located in the external sector of the lagoon; ii) the control of the course of some rivers influencing the supply of sediments. The tendency of sea level rise may have also emphasized the gradual increase of marine influence in this area. Fine-grained sections, related to an increase in Al, phyllosilicates, organic matter, pyrite and siderite contents would be attributed to phases of greater supply of fine-sediments during heavy rainfall events by the nearby Antuã river and other streams during negative phases of North Atlantic Oscillation. Higher deposition of organic matter enhanced diagenetic changes with pyrite and siderite formation. In the bottom of the core another record of pollution was unveiled to mining activities at the beginning of 20th century.

Optimization of Itrax Core Scanner Measurement Conditions for Sediments from Submarine Mud Volcanoes

XRF scanners allow fast, high-resolution delivery of geochemical and physical property data from sediment cores. However, lack of standardized protocols for measuring parameter settings can lead to results of inferior quality to the instrument’s real potential, particularly regarding light elements. In this study, a sediment core from a mud volcano in the Alboran Sea (off SE Spain) with very heterogeneous sedimentological character was analyzed using an Itrax™ Core Scanner (ITRAX). This study assesses some of the factors that influence measurements: type of anode used, X-ray exposure time, and effects resulting from the sample’s exposure to room temperature during analysis as well as those caused by refrigerated storage. Quality and accuracy of the ITRAX data was evaluated by comparison with quantitative measurements obtained by conventional XRF and ICP-OES on discrete samples. The results obtained suggest 20 s is an optimal exposure time as this gives good quality results for the majority of elements analyzed, including light elements and trace elements (e.g. Al (1.9–6.6 %), Cr (84–161 µg g−1), Ni (35–62.5 µg g−1)). Additionally, this analysis time is not significantly detrimental to core condition. The ITRAX capacity to identify diagenetic and authigenic processes in this type of geochemical environment is also demonstrated.

XRF scanners as a quick screening tool for detecting toxic pollutant elements in sediments from Marín harbour in the Ría de Pontevedra (NW Spain)

X-ray fluorescence scanners, such as the Itrax™ Core Scanner (Itrax) (Cox Analytical Systems, Mölndal, Sweden), provide high-resolution geochemical data within several hours. However, the semi-quantitative nature of these analysers has hampered their use to study pollution. This study explores Itraxs capabilities to detect trace metals, such as Hg and Cd, in the Ría de Pontevedra harbour (NW Spain). A set of Itrax detection levels were proposed for each metal after comparison with quantitative measurements obtained from Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Vapour Atomic Absorption Spectrometry (CVAAS) analyses. These quantitative data obtained after a sequential extraction were used to evaluate pollutant bioavailability and to determine metal pollution levels exhibiting Hg pollution. The reliability of inc/coh and Br/Cl ratios to assess the total organic matter variability was also evaluated. The results indicated that the Itrax is an efficient and fast option to monitor contamination, thereby avoiding laborious discrete analyses and reducing analytical cost and time.

Factors Controlling the Incorporation of Trace Metals to Coastal Marine Sediments: Cases of Study in the Galician Rías Baixas (NW Spain)

Transitional coastal environments such as the Galician Rias in the Atlantic coast of NW Spain are densely populated areas. Their environmental problems are highlighted by the conflicting interests of different economic sectors: extensive mariculture activities are located in its waters and intertidal zone; shipbuilding, carbuilding, canning and other industries compete with tourism on their shores; and dairy farming is the main agricultural activity in its surrounding hills and hinterland (Vilas et al., 2008). As a result, the management of the coastal zone is highly complex and it is difficult to balance quality of coastal waters with economic activities. For instance, in the Ria de Vigo, the southernmost of the Rias Baixas, wastewater treatment plants were not installed until the 1990s, and in spite of regional environmental legislation (Lei 8/2001), their capacity was still insufficient in 2005 when the European Court of Justice found Spain guilty of failure to fulfill its obligations under the Article 5 of the Council Directive 79/923/EEC on the quality required for shellfish waters (Case C-26/04 ECJ). This case was closed following Spains submission of a pollution-reducing programme specifically pertinent to shellfish waters; success of this plan will depend critically on the behaviour of the sediments on the ria bottom. Galician Rias experience seasonal upwelling, which increases marine productivity. This promotes the deposition of high organic matter contents in the bottom sediments and contributes to the observed intense sedimentation rates of 1-6 mm yr-1 (Alvarez-Iglesias et al., 2007; Rubio et al., 2001). Current levels of trace metals (Prego & Cobelo, 2003) in sediments of these Rias have caused a significant concern by local and European authorities in the last ten years, especially in relation to the application of the Water Framework Directive (WFD), aimed to ensure that all waters reach “good status” by 2015. Some of these studies (Alvarez-Iglesias et al., 2003; Belzunce-Segarra et al., 2008; Rubio et al., 2000a) showed that the highest concentration of trace metals occurs in the muddiest surficial