50 research outputs found
Variación temporal de las concentraciones de PCBs en tejido de mejillón de dos zonas de la Bahía de Santander (España)
Se presenta la variación temporal de bifenilos policlorados (PCBs) en mejillón silvestre Mytilus galloprovincialis de dos
zonas de la Bahía de Santander (norte de España) de 1991 a 2003, así como la posible influencia en sus concentraciones de los
diferentes aportes externos a que están sometidas ambas zonas. Las concentraciones de SCB7 (suma de los CBs Nos. IUPAC:
28, 52, 101, 118, 138, 153 y 180) de la zona de Pantalán, oscilan entre los 21 μg kg–1 en peso húmedo (ph) y los 38 μg kg–1 ph
Mientras que en la zona de Pedreña, con menor influencia antropogénica, varían entre un mínimo de 8 μg kg–1 ph y un máximo
de 15 μg kg–1 ph Para conocer la evolución temporal, se usa el coeficiente de correlación Tau-b de Kendall y se comprueba la
existencia de una tendencia decreciente significativa en los niveles de PCBs en ambas zonas.An analysis was made of the temporal variation of polychlorinated biphenyls (PCBs) in wild mussel, Mytilus
galloprovincialis, from two areas of Santander Bay (northern Spain) during 1991–2003, as well as of the posible influence of
different external contributions on their concentrations. The concentrations of the sum of seven PCBs (IUPAC numbers 28, 52,
101, 118, 138, 153 and 180) from the Pantalán area ranged from 21 to 38 μg kg–1 wet weight, whereas those from the Pedreña
area, subject to less anthropogenic influence, ranged from 8 to 15 μg kg–1 wet weight. To determine the temporal evolution, the
Kendall Tau-b correlation coefficient was used and a decreasing trend in PCB levels was verified for both areas.Publicado
Impact of regulated and emerging pollutants and microplastics in marine ecosystems (IMPACTA project)
Marine ecosystems are nowadays subjected to a massive input of synthetic chemicals from everywhere. Unfortunately only a small portion of them is being monitored, and it is necessary to identify which pollutants can produce adverse impacts in the marine environment. IMPACTA project (CTM2013-48194-C3) is characterizing the distribution of regulated and emerging contaminants and microplastics in marine sediments, and evaluating the biological effects that they can cause (sing sublethal embryotoxicity tests, endocrine disruption and biomarkers). Sensitive and selective analytical methods are being developed and validated for pharmaceuticals, perfluorinated compounds, organophosphorus pesticides, triazines, personal care products, nonylphenols and alkylated PAHs in sediments. Thus, relevant pollutants present in coastal and offshore areas will be identified. Furthermore potential toxic effects of the contaminants present in coastal sediments are being assessed through embryotoxicity bioassays and also the biological effects on different marine species as a consequence of their exposition to specific compounds.
Another relevant contribution of this project will be the assessment of the impact of micro-plastics, first time in the Spanish coastal areas. Their potential toxic effects and their role in the transference of pollutants in the marine environment are being assessed. The concentration and composition of microplastics in sediments and demersal fish stomachs are being characterized, and their potential biological effects on marine invertebrates are also being investigated
Electronic structure and lattice dynamics of 1T-VSe: origin of the 3D-CDW
In order to characterize in detail the charge density wave (CDW) transition
of 1-VSe, its electronic structure and lattice dynamics are
comprehensively studied by means of x-ray diffraction, angle resolved
photoemission (ARPES), diffuse and inelastic x-ray scattering (IXS), and
state-of-the-art first principles density functional theory calculations.
Resonant elastic x-ray scattering (REXS) does not show any resonant enhancement
at either V or Se K-edges, indicating that the CDW peak describes a purely
structural modulation of the electronic ordering. ARPES identifies (i) a
pseudogap at TT, which leads to a depletion of the density of states
in the plane at TT, and (ii) anomalies in the electronic
dispersion reflecting a sizable impact of phonons on it. A diffuse scattering
precursor, characteristic of soft phonons, is observed at room temperature (RT)
and leads to the full collapse of the low-energy phonon () with
propagation vector (0.25 0 -0.3) r.l.u. We show that the frequency and
linewidth of this mode are anisotropic in momentum space, reflecting the
momentum dependence of the electron-phonon interaction (EPI), hence
demonstrating that the origin of the CDW is, to a much larger extent, due to
the momentum dependence EPI with a small contribution from nesting. The
pressure dependence of the soft mode remains nearly constant up to
13 GPa at RT, with only a modest softening before the transition to the
high-pressure monoclinic phase. The wide set of experimental data are
well captured by our state-of-the art first-principles anharmonic calculations
with the inclusion of van der Waals (vdW) corrections in the
exchange-correlation functional. The description of the electronics and
dynamics of VSe reported here adds important pieces of information to the
understanding of the electronic modulations of TMDs