Estudio analítico de la contaminación metálica en aguas afectadas por actividades antropogénicas crónicas. Métodos de control de la biodisponibilidad y toxicidad metálica.

Los principales objetivos perseguidos en estos trabajos de investigación han sido abordados desde dos puntos de vista: el desarrollo de nuevos métodos de análisis químico que sean fiables para evaluar los niveles subtrazas y ultratrazas de metales pesados y la aplicación de éstas y otras metodologías al estudio de la contaminación metálica de origen antropogénico en aguas costeras andaluzas, así como la evaluación de las formas químicas más biodisponibles, que pueden ser relacionadas con la toxicidad ambiental. Así, los estudios descritos en la presente memoria de investigación, se encuentran distribuidos de la siguiente forma: - En primer lugar se presenta el Capítulo I, el cual consta de una introducción general acerca los metales pesados en los ecosistemas acuáticos. En los dos siguientes capítulos se han aplicado ligandos orgánicos con altas propiedades quelatantes, caracterizados por la presencia del grupo imino, en la determinación de trazas metálicas en muestras acuosas. - En el Capítulo II se desarrolla un nuevo método para la preconcentración y análisis de tazas de plomo basado en el empleo de una membrana líquida de volumen, mediante el uso del ligando orgánico 2-hidroxibenzaldehido N-etiltiosemicarbazona (2-HBET) como agente transportador en la membrana. Cabe destacar la aplicación de este método a muestras naturales, especialmente muestras salinas. - El Capítulo III, el cual fue llevado a cabo durante una estancia de investigación en la University of Ulster (Coleraine, UK) bajo la dirección del Profesor D. John Callan, donde se estudiaron dos bases de Schiff como moléculas sensoras fluorescentes para hierro, proponiéndose dichas moléculas como potenciales indicadores para futuros estudios en el campo de los sensores ópticos. - Por último, en el Capítulo IV se muestra el estudio sobre la influencia global de la actividad antropogénica en un medio costero singular caracterizado por un impacto crónico persistente y de gran interés como es la Bahía de Algeciras, donde: Se establecen los niveles de concentración metálica total de Zn, Cd, Pb y Cu, presentes en las aguas y sedimentos tomados de la zona, donde además se evalúa su distribución en función de las distintas fracciones químicas (estudios de especiación) en ambas muestras medioambientales. Se analizan y cuantifican los niveles de concentración metálica total de estos metales en tejidos biológicos de branquias, hígado y músculo en peces de interés comercial. Así se evalúa el nivel de contaminación química por metales pesados que presentan estas especies biomonitoras de contaminantes inorgánicos. Se estudia la correlación de los niveles metálicos en el medio biótico con el medio abiótico, identificando las formas químicas más biodisponibles y, en consecuencia con mayor potencial tóxico

Comprehensive Assessment and Potential Ecological Risk of Trace Element Pollution (As, Ni, Co and Cr) in Aquatic Environmental Samples from an Industrialized Area

A global assessment of arsenic (As), nickel (Ni), cobalt (Co) and chromium (Cr) was performed in environmental samples from an important industrial bay. Different fractions of water, sediments and tissues from four species of fish were analysed. Samples were collected from selected sampling sites during four consecutive samplings in spring and autumn seasons, in order to evaluate concentrations and their possible correlations among the aquatic compartments. While a higher availability of Cr and Ni was found in water, Co and As were the most available elements in sediments. In fish, the liver was the tissue with the highest proportion of As and Co, and gills showed the highest concentrations of Ni and Cr. Significance differences were observed among sites showing the pollution sources. In sediments, high correlations were found between total Co content and the most available fractions. Total Ni content highly correlated with the oxidisable fraction, while Cr total content tightly correlated with the least available fractions. Quality guideline values for sediments were frequently exceeded. In sediments and biota, concentrations were slightly higher than in other ecosystems, indicating that maritime, industrial and urban activities are affecting this type of ecosystem with great anthropogenic influence.This research was funded by "Consejeria de Economia, Conocimiento, Empresas y Universidad", Junta de Andalucia (Spain) (PAI-EXCEL-06-FQM-02075) and by "Fomento e Impulso de la Investigacion y de la Transferencia" Programme, Universidad de Cadiz (Spain) (PR2020-013)

A new use for an old molecule: N-phenyl-2-(2-hydroxynaphthalen-1-ylmethylene)hydrazinecarbothioamide as a ratiometric ‘Off–On’ fluorescent probe for iron

N-Phenyl-2-(2-hydroxynaphthalen-1-ylmethylene)hydrazinecarbothioamide has been investigated as a fluorescent sensor for the determination of Fe(III) in aqueous solutions. The probe was prepared by the facile Schiff base condensation of 2-hydroxy-1-napthaldehyde with N-phenylhydrazinecarbothioamide. The sensor displayed good selectivity for Fe(III) when tested against a range of biologically and environmentally important cations. A concentration dependent increase in the emission of two fluorescent bands at 425 and 495 nm was observed upon increasing Fe(III) addition resulting in a linear ratiometric response in the 17–37 lM range. The binding stoichiometry was confirmed as 1:1 (host/guest) with the binding constant (logb) calculated as 4.56

A New Fluorescent Sensor for the Determination of Iron(III) in Semi-Aqueous Solution

A simple fluorescent sensor 1 has been developed for the recognition of Fe(III) in semi-aqueous solution at pH 7.0. The sensor, containing two Schiff base type receptors directly connected to naphthalene fluorophores, shows a concentration dependent decrease in emission intensity upon Fe(III) addition. The sensor was selective for Fe(III) over other metal ions and can measure Fe(III) ion concentration between 0.05 and 0.12 mM. The binding stoichiometry was established as 1:1 (host: guest) with a binding constant (Logβ) of 4.01. Furthermore, the addition of Fe(III) to a solution of 1 caused a colour change from light yellow to colourless meaning 1 is also capable of detecting Fe(III) by the naked eye

Sherry wine industry by-product as potential biosorbent for the removal of Cr(VI) from aqueous medium

A low-cost biosorbent obtained from the Palomino Fino grape seed, a Sherry wine industry by-product, has been proposed as a way of valorising this material. The biomass was characterised obtaining values of 0.68 +/- 0.05 g mL(-1) for bulk density, 1.02 +/- 0.09 g mL(-1) for apparent density and 33.3% for porosity. The pH(pzc) was 5.2 and the surface negative charge value was 2.4 +/- 0.2 mmol g(-1). The analysis of surface morphology showed differences due to the sorption. The results showed a promising potential for chromium(VI) removal from aqueous solutions. The studies were carried out in batch scale and a 2(3) factorial design was applied for the optimisation of the process. A percentage of 91.7 +/- 0.6% was achieved for the biosorption of Cr(VI) under optimal conditions using pH 5.5, 15 g/L of biosorbent and 8 h of contact time. The biosorption capacity showed a remarkable linearity from 0 to 2 mmol L-1 Cr(VI) and a precision of 0.64% for the removal of 1 mmol L-1 of metal. Langmuir, Freundlich and Temkin isotherm equations and the parameters of six kinetic models were used in the equilibrium modelling and identifying the mechanism of the biosorption. The combination of physical and chemical sorption mechanisms was proposed for the chromium removal with a high maximum sorption capacity (q(max) = 208.3 mg g(-1)). Thermodynamic parameters indicated the spontaneous and endothermic nature of the chromium removal. The successful biosorption was based on the special grape seed components with a relevant content in antioxidant and lignocellulosic compounds.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This work has been supported by "Consejeria de Economia, Conocimiento, Empresas y Universidad", Andalusian Government (Spain) (support for RNM-236 Research group) and the Programme of "Fomento e Impulso de la Investigacion y de la Transferencia" from the University of Cadiz (Spain) (Project PR2020-013)

Sensing Cd(II) Using a Disposable Optical Sensor Based on a Schiff Base Immobilisation on a Polymer-Inclusion Membrane. Applications in Water and Art Paint Samples

A disposable colour-changeable optical sensor based on an interesting polymer inclusion-membrane (PIM) was designed to determine Cd(II) ions in aqueous medium. The Schiff base 2-acetylpyridine benzoylhydrazone (2-APBH) immobilised on the polymer membrane was used as a sensing molecule. The amounts of the PIM components were optimised by a 3(2) fractional factorial design with two central points and two blocks. The best optical sensor composition consisted of 2.5 g of poly(vinylchloride) (PVC) as a base polymer, 3 mL of tributyl phosphate (TBP) as a plasticiser, and 0.02 g of 2-APBH as a reagent. The sensor showed a good linear response in the range from 0.02 mg L-1 (limit of detection) to 1 mg L-1 of Cd(II) under the following experimental conditions: pH 9.5 (adjusted using ammonium chloride buffer solution at 0.337 mol L-1), 60 min of exposure time plus 2 min of sonication (pulses at 2 s intervals), and 10 min of short-term stability. The relative standard deviation of the method was determined to be 4.04% for 0.4 mg L-1 of Cd(II). The optical sensor was successfully applied to the determination of Cd(II) in natural-water and art-paint samples

EJVES vol 34, issue 2 (August 2007) - Spanish Translated Abstracts

Chronic exposure to arsenic (As) through the consumption of contaminated groundwaters is a major threat to public health in South and Southeast Asia. The source of As-affected groundwaters is important to the fundamental understanding of the controls on As mobilization and subsequent transport throughout shallow aquifers. Using the stable isotopes of hydrogen and oxygen, the source of groundwater and the interactions between various water bodies were investigated in Cambodia’s Kandal Province, an area which is heavily affected by As and typical of many circum-Himalayan shallow aquifers. Two-point mixing models based on δD and δ18O allowed the relative extent of evaporation of groundwater sources to be estimated and allowed various water bodies to be broadly distinguished within the aquifer system. Model limitations are discussed, including the spatial and temporal variation in end member compositions. The conservative tracer Cl/Br is used to further discriminate between groundwater bodies. The stable isotopic signatures of groundwaters containing high As and/or high dissolved organic carbon plot both near the local meteoric water line and near more evaporative lines. The varying degrees of evaporation of high As groundwater sources are indicative of differing recharge contributions (and thus indirectly inferred associated organic matter contributions). The presence of high As groundwaters with recharge derived from both local precipitation and relatively evaporated surface water sources, such as ponds or flooded wetlands, are consistent with (but do not provide direct evidence for) models of a potential dual role of surface-derived and sedimentary organic matter in As mobilization

Contrasting Sorption Behaviours Affecting Groundwater Arsenic Concentration in Kandal Province, Cambodia

Natural arsenic (As) contamination of groundwater which provides drinking water and/or irrigation supplies remains a major public health issue, particularly in South and Southeast Asia. A number of studies have evaluated various aspects of the biogeochemical controls on As mobilization in aquifers typical to this region, however many are predicated on the assumption that key biogeochemical processes may be deduced by sampled water chemistry. The validity of this assumption has not been clearly established even though the role of sorption/desorption of As and other heavy metals onto Fe/Mn (hydr)oxides is an important control in As mobilization. Here, selective chemical extractions of sand-rich and clay-rich sediments from an As-affected aquifer in Kandal Province, Cambodia, were undertaken to explore the potential role of partial re-equilibrium through sorption/desorption reactions of As and related solutes (Fe, Mn and P) between groundwater and the associated solid aquifer matrix. In general, groundwater As is strongly affected by both pH and Eh throughout the study area. However, contrasting sorption behaviour is observed in two distinct sand-dominated (T-Sand) and clay dominated (T-Clay) transects, and plausibly attributed to differing dominant lithologies, biogeochemical and/or hydrogeological conditions. Sorption/desorption processes appear to be re-setting groundwater As concentrations in both transects, but to varying extents and in different ways. In T-Sand, which is typically highly reducing, correlations suggest that dissolved As may be sequestered by sorption/re-adsorption to Fe-bearing mineral phases and/or sedimentary organic matter; in T-Clay Eh is a major control on As mobilization although binding/occlusion of Fe-bearing minerals to sedimentary organic matter may also occur. Multiple linear regression analysis was conducted with groups categorised by transect and by Eh, and the output correlations support the contrasting sorption behaviours encountered in this study area. Irrespective of transect, however, the key biogeochemical processes which initially control As mobilization in such aquifers, may be “masked” by the re-setting of As concentrations through in-aquifer sorption/desorption processes

Química analítica cualitativa. Test de autoevaluación sobre identificación de cationes. I.

Ejercicio fácil de autoevaluación que sirve para reforzar conocimientos sobre las propiedades analíticas de los cationes y los ensayos de identificación en disolución

Curso de análisis cualitativo. Reaccionabilidad de los cationes metálicos en disolución. Ejercicio interactivo.

Ejercicio de asociación cuya finalidad es la de profundizar en el conocimiento de las propiedades de las especies iónicas en disolución y su comportamiento frente a reactivos generales y especiales