Removal of Inorganic Mercury From Aqueous Solutions by Biomass of the Marine Macroalga Cystoseira Baccata

[Abstract] The ability of Cystoseira baccata algal biomass to remove Hg(II) from aqueous solutions is investigated. The mercury biosorption process is studied through batch experiments at 25ºC with regard to the influence of contact time, initial mercury concentration, solution pH, salinity and presence of several divalent cations. The acid-base properties of the alga are also studied, since they are related to the affinity for heavy metals. The studies of the pH effect on the metal uptake evidence a sharp increasing sorption up to a pH value around 7.0, which can be ascribed to changes both in the inorganic Hg(II) speciation and in the dissociation state of the acid algal sites. The sorption isotherms at constant pH show uptake values as high as 178 mg.g-1 (at pH 4.5) and 329 mg.g-1 (at pH 6.0). The studies of the salinity influence on the Hg(II) sorption capacity of the alga exhibit two opposite effects depending on the electrolyte added; an increase in concentration of nitrate salts (NaNO3, KNO3) slightly enhances the metal uptake, on the contrary, the addition of NaCl salt leads to a drop in the sorption. The addition of different divalent cations to the mercury solution, namely Ca2+, Mg2+, Zn2+, Cd2+, Pb2+ and Cu2+, reveals that their effect on the uptake process is negligible. Finally, the equilibrium sorption results are compared with predictions 1 obtained from the application of a simple competitive chemical model, which involves a discrete proton binding constant and three additional constants for the binding of main neutral inorganic Hg(II) complexes, Hg(Cl) HgOHCl and Hg(OH)2, to the algal surface sites

El complejo de Órdenes: subdivisión, descripción y discusión sobre su origen.

[Resumen] El Complejo de Ordenes, el mayor de los macizos alóctonos con rocas máficas y ultramAficas de Galicia y el N de Portugal, se ha subdividido en cinco unidades en base, fundamentalmente, a las asociaciones litológicas: U. de Santiago, U. de Villa de Cruces, U. De la Sierra del Careón-Bazar, U. de SobradoMellid y U. de Betanzos-Arzúa. Todas ellas están separadas entre si por cabalgamientos y superpuestas tectónicamente. Para cada unidad, se realiza una descripción petrológica y se analizan las relaciones de las diferentes rocas entre si. ,Se efectúa, además, una revisión de los datos geoquimicos disponibles y, finalmente, se discute el origen probable de las distintas unidades[Abstract] The Ordenes Complex, the biggest OI the allochthonous massifs with mafic and ultramafic rocks in Galicia and northern Portugal, has been divided into five units according to the lithological associations: Santiago Unit, Villa de Cruces Unít, Sierra del Care6n-Bazar Unit, Sobrado-Mellid Unít and BetanzoS-Arzúa Unít. They are separated from each other by thrust faults and tectonically stacked. For each OI the units, a petrological description is given, explaining the relationships between the different rock types. Moreover, the geochemical data available are reviewed and the probable origin of the units is discusse

A Revision of the characteristics and clasification of the hercynian granitoids of Northern Galicia and Western Asturias (NW Spain)

[Resumen] Este trabajo resume parte de los resultados obtenidos en el desarrollo del proyecto «Caracterización y correlación petrológica, geoquímica y geocronológica de las rocas graníticas de Galicia (A Coruña-Lugo)>>, realizado por el 1. ~G. M. E. El estudio sistemático de los distintos plutones graníticos de esta región ha puesto de manifiesto que los criterios de clasificación tradicionalmente utilizados en este ámbito geológico, presentan una serie de limitaciones debidas por una parte a la rigidez de los grupos establecidos y por otra, a las características transicionales de algunas unidades plutónicas. Estos hechos permiten suponer que las relaciones entre los «granitoides alcalinos y alumínicos de dos micas» y los «granitoides de tendencia calcoalcalina» no son tan independientes como se ha venido considerando en los modelos preexistentes. En función de la profundidad y etapa de emplazamiento y de las características petrológicas, las distintas unidades se han agrupado en las siguientes familias: - Granitoides sincinemáticos de emplazamiento relativamente profundo. - Granitoides sincinemáticos de emplazamiento somero. - Granitoides postcinemáticos de emplazamiento somero. Asimismo se detectan unidades plutónicas complejas, constituidas por varios granitos, a los cuales les corresponderían génesis diferentes, si se siguiesen los criterios previamente vigentes.[Abstract] This article summarizes part of the results of the project «Petrological, geochemical and geochronological caracterization and correlation of the granitic rocks of Galicia (provinces of A Coruña-Lugo)>>, executed on behalf of the Spanish Institute of Geology and Mining (1. G. M. E.). The Systematic investigation of the different granite plutons of the area evidences that the application of the criteria traditionally used for the classification of the granitic rocks in Galicia meets with serious difficulties. These are due to the rigidity of the established groups on the one hand and the transitional character of a number of plutonic units on the other hand. The study suggests that the relationship among the {<a1caline and aluminous two-mica granites» and the granitoids of the «ca1c-a1caline tendency is less independent than assumed in the hitherto used classification schemes and petrogenetical models. As a function of the depth and time of their emplacement and their petrological features, the different plutonic units are grouped into the following families: - Synkinematic, relatively deep-seated granitoid bodies. - Synkinematic, shallow-level granitoid bodies. - Postkinematic, shallow-level granitoid bodies. Attention is drawn to the occurrence of complex plutonic units whose constituent members would, according to the criteria of the pre-existing classification schemes, be petrogenetically unrelated or poorly related

Use of Waste-Derived Biochar to Remove Copper from Aqueous Solution in a Continuous-Flow System

The discharges from industrial processes constitute the main source of copper contamination in aqueous ecosystems. In this study we investigated the capacity of different types of biochar (derived from chicken manure, eucalyptus, corncob, olive mill and pine sawdust) to remove copper from aqueous solution in a continuous-flow system. The flow rate of the system strongly influenced the amount of copper retained. The adsorption to the corncob biochar varied from 5.51 to 3.48 mg Cu g-1 as the flux decreased from 13 to 2.5 mL min-1. The physicochemical characteristics of biochar determine the copper retention capacity and the underlying immobilization mechanisms. Biochars with high inorganic contents retain the largest amounts of copper and may be suitable for using in water treatment systems to remove heavy metals. The copper retention capacity of the biochars ranged between ~1.3 and 26 mg g-1 and varied in the following order: chicken manure > olive mill >> corncob > eucalyptus > sawdust pine

Atomic scale model and electronic structure of Cu2_2O/CH3_3NH3_3PbI3_3 interfaces in perovskite solar cells

Cuprous oxide has been conceived as a potential alternative to traditional organic hole transport layers in hybrid halide perovskite-based solar cells. Device simulations predict record efficiencies using this semiconductor, but experimental results do not yet show this trend. More detailed knowledge about the Cu$_2$O/perovskite interface is mandatory to improve the photoconversion efficiency. Using density functional theory calculations, here we study the interfaces of CH$_3$NH$_3$PbI$_3$ with Cu$_2$O to assess their influence on device performance. Several atomistic models of these interfaces are provided for the first time, considering different compositions of the interface atomic planes. The interface electronic properties are discussed on the basis of the optimal theoretical situation, but in connection with the experimental realizations and device simulations. It is shown that the formation of vacancies in the Cu$_2$O terminating planes is essential to eliminate dangling bonds and trap states. The four interface models that fulfill this condition present a band alignment favorable for photovoltaic conversion. Energy of adhesion, and charge transfer across the interfaces are also studied. The termination of CH$_3$NH$_3$PbI$_3$ in PbI$_2$ atomic planes seems optimal to maximize the photoconversion efficiency.Comment: 16 pages; 8 figures. Submitted to ACS Applied Materials & Interfaces. Published after changes not included her

Mechanisms of silver nanoparticle toxicity to the coastal marine diatom Chaetoceros curvisetus

Inputs of silver nanoparticles (AgNPs) to marine waters continue to increase yet mechanisms of AgNPs toxicity to marine phytoplankton are still not well resolved. This study reports a series of toxicity experiments on a representative coastal marine diatom species Chaetoceros curvisetus using the reference AgNP, NM-300K. Exposure to AgNPs resulted in photosynthetic impairment and loss of diatom biomass in proportion to the supplied AgNP dose. The underlying mechanism of toxicity was explored via comparing biological responses in parallel experiments. Diatom responses to AgNP, free Ag(I) species, and dialysis bag-retained AgNP treatments showed marked similarity, pointing towards a dominant role of Ag(I) species uptake, rather than NPs themselves, in inducing the toxic response. In marked contrast to previous studies, addition of the organic complexing agent cysteine (Cys) alongside Ag only marginally moderated toxicity, implying AgCys− complexes were bioavailable to this diatom species. A preliminary field experiment with a natural phytoplankton community in the southeast Atlantic Ocean showed no significant toxic response at a NM-300 K concentration that resulted in ~40% biomass loss in the culture studies, suggesting a modulating effect of natural seawaters on Ag toxicity

Competition effects in cation binding to humic acid: Conditional affinity spectra for fixed total metal concentration conditions

Information on the Pb and Cd binding to a purified Aldrich Humic Acid (HA) is obtained from the influence of different fixed total metal concentrations on the acid- base titrations of this ligand. NICA (Non-Ideal Competitive Adsorption) isotherm has been used for a global quantitative description of the binding, which has then been interpreted by plotting the Conditional Affinity Spectra of the H+ binding at fixed total metal concentrations (CAScTM). This new physicochemical tool, here introduced, allows the interpretation of binding results in terms of distributions of proton binding energies. A large increase in the acidity of the phenolic sites as the total metal concentration increases, especially in presence of Pb, is revealed from the shift of the CAScTM towards lower affinities. The variance of the CAScTM distribution, which can be used as a direct measure of the heterogeneity, also shows a significant dependence on the total metal concentration. A discussion of the factors that influence the heterogeneity of the HA under the conditions of each experiment is provided, so that the smoothed pattern exhibited by the titration curves can be justified

The influence of Arctic Fe and Atlantic fixed N on summertime primary production in Fram Strait, North Greenland Sea

Climate change has led to a ~ 40% reduction in summer Arctic sea-ice cover extent since the 1970s. Resultant increases in light availability may enhance phytoplankton production. Direct evidence for factors currently constraining summertime phytoplankton growth in the Arctic region is however lacking. GEOTRACES cruise GN05 conducted a Fram Strait transect from Svalbard to the NE Greenland Shelf in summer 2016, sampling for bioessential trace metals (Fe, Co, Zn, Mn) and macronutrients (N, Si, P) at ~ 79°N. Five bioassay experiments were conducted to establish phytoplankton responses to additions of Fe, N, Fe + N and volcanic dust. Ambient nutrient concentrations suggested N and Fe were deficient in surface seawater relative to typical phytoplankton requirements. A west-to-east trend in the relative deficiency of N and Fe was apparent, with N becoming more deficient towards Greenland and Fe more deficient towards Svalbard. This aligned with phytoplankton responses in bioassay experiments, which showed greatest chlorophyll-a increases in + N treatment near Greenland and + N + Fe near Svalbard. Collectively these results suggest primary N limitation of phytoplankton growth throughout the study region, with conditions potentially approaching secondary Fe limitation in the eastern Fram Strait. We suggest that the supply of Atlantic-derived N and Arctic-derived Fe exerts a strong control on summertime nutrient stoichiometry and resultant limitation patterns across the Fram Strait region.S.K. was financed by GEOMAR and the German Research Foundation (DFG Award Number AC 217/1-1 to E.P.A). T.J.B. acknowledges funding from a Marie Skłodowska-Curie Postdoctoral European Fellowship (OceanLiNES; Project ID 658035). Open Access funding provided by Projekt DEAL