Time filter

Source Type

Bauza M.C.,National University of Rosario | Ibanez G.A.,National University of Rosario | Tauler R.,Institute Of Diagnosi Ambiental I Estudis Of Laigua Idaea Csic | Olivieri A.C.,National University of Rosario
Analytical Chemistry | Year: 2012

A new equation is derived for estimating the sensitivity when the multivariate curve resolution-alternating leastsquares (MCR-ALS) method is applied to second-order multivariate calibration data. The validity of the expression is substantiated by extensive Monte Carlo noise addition simulations. The multivariate selectivity can be derived from the new sensitivity expression. Other important figures of merit, such as limit of detection, limit of quantitation, and concentration uncertainty of MCR-ALS quantitative estimations can be easily estimated from the proposed sensitivity expression and the instrumental noise. An experimental example involving the determination of an analyte in the presence of uncalibrated interfering agents is described in detail, involving second-order time-decaying sensitized lanthanide luminescence excitation spectra. The estimated figures of merit are reasonably correlated with the analytical features of the analyzed experimental system. © 2012 American Chemical Society. Source

Moreno J.I.L.,CSIC - Pyrenean Institute of Ecology | Latron J.,Institute Of Diagnosi Ambiental I Estudis Of Laigua Idaea Csic | Lehmann A.,University of Geneva
Hydrological Processes | Year: 2010

This work analyses the responses of four regression-based interpolation methods for predicting snowpack distribution to changes in the number of data points (sample size) and resolution of the employed digital elevation model (DEM). For this purpose, we used data obtained from intensive and random sampling of snow depth (991 measurements) in a small catchment (6 km 2) in the Pyrenees, Spain. Linear regression, classification trees, generalized additive models (GAMs), and a recent method based on a correction made by applying tree classification to GAM residuals were used to calculate snow-depth distribution based on terrain characteristics under different combinations of sample size and DEM spatial resolution (grid size). The application of a tree classification to GAM residuals yielded the highest accuracy scores and the most stable models. The other tested methods yielded scores with slightly lower accuracy and varying levels of robustness under different conditions of grid and sample size. The accuracy of the model predictions declined with decreasing resolution of DEMs and sample size; however, the sensitivities of the models to the number of data points showed threshold values, which has implications (when planning fieldwork) for optimizing the relation between the effort expended in gathering data and the quality of the results. Copyright © 2009 John Wiley & Sons, Ltd. Source

Garcia-Roger E.M.,University of Barcelona | del Sanchez-Montoya M.M.,University of Murcia | Gomez R.,University of Murcia | Suarez M.L.,University of Murcia | And 4 more authors.
Aquatic Sciences | Year: 2011

In this study we examined the importance of seasonal changes in habitat features and aquatic macroinvertebrate responses in temporary and perennial streams from two different catchments in the Western Mediterranean region in Spain. Macroinvertebrate sampling was spatially intensive to account for the relative frequency of meso- (i. e., riffles and pools) and micro-habitats (i. e., different mineral and organic-based substrata) at each site. Samples were collected at two distinctly different phases of the hydrograph: (1) during the flowing period, when pool-riffle sequences were well-established, and (2) during the dry phase, when only isolated pools were expected to occur in the temporary streams. During the dry season, both a reduction in the available total habitat and in microhabitat diversity in all sites studied was observed. As a result, taxon richness decreased in all streams, but more dramatically at temporary stream sites and particularly so in the infrequently remaining discontinuous riffles. Macroinvertebrate assemblages differed among catchments (i. e., geographical identity) and sites (perennial vs. temporary). Invertebrate differences were also strong within and among meso- and micro-habitats, particularly mineral and organic microhabitat patches, and differences were due to both loss of taxa from some habitats and some taxa exhibiting certain habitat affinities. © 2011 Springer Basel AG. Source

Koenig S.,CSIC - Institute of Marine Sciences | Koenig S.,Institute Of Diagnosi Ambiental I Estudis Of Laigua Idaea Csic | Huertas D.,Institute Of Diagnosi Ambiental I Estudis Of Laigua Idaea Csic | Fernandez P.,Institute Of Diagnosi Ambiental I Estudis Of Laigua Idaea Csic
Science of the Total Environment | Year: 2013

The levels and profiles of organochlorine (OC) contaminants, including polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs) and penta- (PeCB) and hexachlorobenzene (HCB), as well as polybrominated diphenyl ethers (PBDEs) were determined in muscle samples of the deep-sea fish Alepocephalus rostratus, Coelorinchus mediterraneus and Lepidion lepidion and the red-shrimp Aristeus antennatus from the NW Mediterranean Sea. Mean PCB and DDT levels ranged from the highest concentrations in the fish A. rostratus (σ7PCBs 6.93±0.71ng/gw.w. and σDDTs 8.43±1.10ng/gw.w.) to the lowest concentrations in the crustacean A. antennatus (σ7PCBs 1.17±0.24ng/gw.w. and σDDTs 2.53±0.26ng/gw.w.). The concentrations of σHCHs and HCB were more than one order of magnitude lower, ranging from 0.07-0.36ng/gw.w. and 0.03-0.15ng/gw.w., respectively, while PeCB was only detected in a few samples. PBDE levels were approximately ten times lower than PCB and DDT concentrations, ranging from 0.47±0.20ng/gw.w. in A. antennatus to 0.92±0.13ng/gw.w. in A. rostratus. The high-molecular-weight PCBs 153, 138 and 180 represented 69-79% of σ7PCBs in fish and 60% in the red shrimp. Moreover, in fish, the main DDT compound detected was the metabolite p,p'-DDE (70-80% of σDDTs), indicative of old DDT residues. In contrast, o,p'-DDE was the main DDT metabolite (49% of σDDTs) in shrimp, while the parent compound p,p'-DDT and its metabolite p,p'-DDE exhibited similar proportions of 16% and 21%, respectively. For PBDEs, the most abundant congeners were BDEs 28, 47, 99, 100 and 154 in fish (>70% σ14PBDEs), while BDEs 153 and 209 were also important in A. antennatus, suggesting different uptake and/or biotransformation rates of PBDEs between fish and crustacea. In this sense, the ratios BDE 99/100, BDE 153/154, and BDE 47/99 were determined as proxies for BDE metabolization capacities and contrasted among species. © 2012 Elsevier B.V. Source

Sanchez-Vidal A.,University of Barcelona | Llorca M.,Institute Of Diagnosi Ambiental I Estudis Of Laigua Idaea Csic | Farre M.,Institute Of Diagnosi Ambiental I Estudis Of Laigua Idaea Csic | Canals M.,University of Barcelona | And 3 more authors.
Science of the Total Environment | Year: 2015

The finding of perfluoroalkyl substances (PFASs) in particles sinking to the deep northwestern Mediterranean Sea confirms the role of the latter as ballast for the transfer of pollutants to the deep sea. The transfer of particulate matter down to the deep is enhanced during atmosphere-driven, high-energy physical oceanographic processes like dense shelf water cascading (DSWC), which is caused by winter surface heat losses and evaporation. Here we present data from samples collected during winter 2012, when dense shelf water formation and subsequent cascading triggered the flushing of large amounts of PFASs through a submarine canyon to depths in excess of 1000. m. The finding of quantifiable concentrations of long-chain PFOA, PFOS and PFNA substances and significantly high concentrations of the short-chain substances PFHxA and PFBA indicates that these compounds, sorbed onto particulate matter, are quickly and directly transferred to the ocean's interior, thus highlighting the role of DSWC in removing those pollutants from the coastal ocean. Eventually, uncertainties about our results arising from the limited number of samples available are counterbalanced by their intrinsic value as intense DSWC events, like the one in 2012, occur only every 5-7. years in the study area, which seriously restricts sampling opportunities. Our results add PFASs to the list of persistent organic pollutants like polychlorinated biphenyls, chlorobenzenes or polycyclic aromatic hydrocarbons known to be conveyed to the deep marine environment. © 2015 Elsevier B.V. Source

Discover hidden collaborations