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Tinoco P.,Alfonso X El Sabio University | Almendros G.,MNCN CSIC | Gonzalez-Vila F.J.,IRNAS CSIC | Sanz J.,IQOG CSIC | Gonzalez-Perez J.A.,IRNAS CSIC
Journal of Soils and Sediments | Year: 2015

Purpose: Aromaticity of soil organic matter has often been considered an independent index of biogeochemical maturity, recalcitrance, and persistence of C in soils. The structural characteristics of soil humic acids (HAs) from various origins are studied by bi- and multivariate statistical exploratory analyses to select chemical descriptors surrogated to aromaticity. Materials and methods: Structural features of 16 HAs were determined using analytical pyrolysis, wet chemical oxidation, and a variety of spectroscopic analyses. Data management was approached by (a) linear correlations between classical HAs structural descriptors and the concentration of aromatic C as seen by 13C NMR spectra as independent variable and (b) multivariate statistics to define HA aromaticity as an emergent property defined by the shared contribution of a set of variables. Results and discussion: Significant correlations were found between HAs optical density (465 nm; E4) and aromatic C regions (13C NMR). These also paralleled the intensity of the Fourier Transform Infrared Spectroscopy (FT-IR) bands ascribed to aromatic structures. Likewise, significant positive correlations were observed between E4 and aromatic compounds released by wet chemical degradation, with negative correlations with yields of aliphatic and lignin-derived methoxyphenols released by pyrolysis. Conclusions: Multivariate classification of HAs’ analytical descriptors allows the identification of variables, i.e., E4, H/C atomic ratio, intensity of aromatic C in the 13C NMR region between 110–140 and 140–160 ppm, and yield of benezenecarboxylic acids after chemical degradation, as surrogates for HAs’ aromaticity. This HA characteristic is also responsive to the variability between environmental scenarios, mainly the effect of wildfires and soil management (clearing and cultivation). © 2014, Springer-Verlag Berlin Heidelberg. Source


Artiaga G.,Complutense University of Madrid | Ramos K.,Complutense University of Madrid | Ramos L.,IQOG CSIC | Camara C.,Complutense University of Madrid | Gomez-Gomez M.,Complutense University of Madrid
Food Chemistry | Year: 2015

In this work, silver migration from commercial food containers was evaluated according to European Regulation 10/2011. Several experimental parameters affected silver release: food simulant, temperature, exposition time and sampled bag area. Results demonstrated a significant silver nanoparticle (AgNP) migration into aqueous and acidic simulants. The amount of silver migrated increased with storage time and temperature although, in general, silver showed a low tendency to migrate into food simulants (17 ng/g). However, the food simulant did not seem to be a really outstanding variable for long term storage. AF4-ICP MS was used to confirm the presence of AgNPs in the simulants. The low limit of detection achieved (0.4 μg L-1) allowed the identification of AgNPs and their size characterisation (40-60 nm). Finally, scanning electron microscopy/energy-dispersive X-ray analysis suggested a possible transformation of the AgNPs detected in the extracts, due to association with other ligands, such as chlorine and sulphur, present in the original containers. © 2014 Elsevier Ltd. All rights reserved. Source


Pena-Abaurrea M.,IQOG CSIC | Ye F.,Campus Management | Blasco J.,Campus Management | Ramos L.,IQOG CSIC
Journal of Chromatography A | Year: 2012

This study evaluates the feasibility of comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC × GC-ToF MS) for the determination of the 15. +. 1. EU PAHs in sediments. Experimental variables affecting the injection, chromatographic separation and analytical detection of the analytes have systematically been optimised. Under finally proposed conditions, a satisfactory resolution among critical pairs/groups of PAHs, including benz[. a]anthracene, cyclopenta[. cd]pyrene and chrysene, the three benzofluoranthene isomers, indeno[1,2,3. -cd]pyrene from dibenz[. a,. h]anthracene (DahA), and DahA from dibenz[. a,. c]anthracene, has been achieved using DB-5 × BPX-50 as column combination with a run time of 1. h. The feasibility of the method for the analysis of real-life samples has been demonstrated by accurate determination of relevant target PAHs in the certified harbour sediment BCR-535 (deviations among certified concentration values and those calculated using the proposed method lower than 3%); and by successful application to sediments sampled from a relevant protected area located in the South of Spain. The low methodological limits of detection (LODs) obtained for most of the targeted PAHs (in the 5.7-60 μg/kg range, as calculated for real samples) guarantied accurate quantification of the target compounds at the low levels expected in these types of pristine matrices. The strong retention experienced by the heaviest dibenzopyrene isomers included in the study resulted in relatively high LODs for these analytes; nevertheless, these compounds were detected at concentration levels above the corresponding LOD in some of the analysed sediments. In addition, the enhanced identification power provided by GC × GC-ToF MS for the identification of non-target analytes allowed the tentative identification of a group of polynuclear aromatic thiophenes in some of the test samples. Finally, the potential of the use of normalised bubble plots for the fast screening of the potential PAH sources has been demonstrated. © 2012 Elsevier B.V. Source


El-Amrani S.,Complutense University of Madrid | Pena-Abaurrea M.,IQOG CSIC | Sanz-Landaluze J.,Complutense University of Madrid | Ramos L.,IQOG CSIC | And 2 more authors.
Science of the Total Environment | Year: 2012

The feasibility of a bioaccumulation test based on the use of zebrafish eleutheroembryos as an alternative to adult-individual-based approaches for REACH application has been evaluated for three test compounds, chlorpyrifos, dicofol and atrazine. Following the OECD 305 guidelines, zebrafish eleutheroembryos (72h after hatching, hpf) were separately exposed to the investigated pesticides at two nominal concentrations below 1% of its corresponding LC50. The uptake experiments lasted for 48h. Then, the exposure medium was replaced by a non-contaminated medium for depuration experiments (up to 72h). Zebrafish eleutheroembryos (larvae 144 hpf, i.e. at the end of the depuration step) and their corresponding exposure media was sampled at ten different times during each experiment and the concentration of the investigated pesticide determined in both the organisms and in the exposure medium. The experimentally determined pesticide accumulation profiles in the eleutheroembryos demonstrated that atrazine has a very fast accumulation kinetic, reaching steady sate (SS) within 24h. Chlorpyrifos and dicofol did not reach the SS within the 48-h uptake experiments although they exhibit higher accumulations than the former pesticide. Two toxicokinetic models were used to calculate the bioconcentration factor (BCF) of the studied pesticide in zebrafish eleutheroembryos. In the former, the BCF was calculated under SS conditions (BCFSS). The second was used when the compounds did not reach the SS during the uptake experiment (BCFk). Log BCF values of 3.55 and 3.84 for chlorpyrifos; 0.6 and 1.17 for atrazine, and 3.90 for dicofol were experimentally calculated at selected exposure concentrations. These values have been compared with those reported in related bioaccumulation studies and official databases. © 2012 Elsevier B.V. Source


Pena-Abaurrea M.,IQOG CSIC | Covaci A.,University of Antwerp | Ramos L.,IQOG CSIC
Journal of Chromatography A | Year: 2011

This study evaluates comprehensive two-dimensional gas chromatography (GC × GC) coupled to time-of-flight mass spectrometry (GC × GC-ToF MS) for the simultaneous analysis of several classes of organobromines (OBs), including polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs), methoxylated PBDEs (MeO-PBDEs), several halogenated naturally produced compounds (HNPs) and eight novel brominated flame retardants (NBFRs), polybrominated hexahydroxanthene derivates (PBHDs), 2,4,6-tribromoanisole and a mixed halogenated compound (MHC-1), in bluefin tuna muscles. The proposed methodology maximised separation of both within and among OB families, and among these and other halogenated micropollutants detected in these samples and co-extracted matrix components. Special attention has been paid to solve co-elution problems observed during the analysis of OBs with one-dimensional GC-based techniques. Satisfactory separation among several relevant PBDEs and MeO-PBDEs has been obtained allowing their unambiguous determination in a single run. Additional studies were conducted to identify selected NBFRs and HNPs. 2,4-Dibromoanisole, a dibromophenol isomer and hexabromobenzene were identified in the investigated samples. Several new tri- and tetra-BHD derivates were also identified, indicating that these compounds could apparently exist as structured families in nature. In addition, a tetrabrominated diMeO-biphenyl and two tetrabrominated diMeO-BDEs were also tentatively identified. © 2011 Elsevier B.V. Source

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