Dentz M.,IDAEA |
Tartakovsky D.M.,University of California at San Diego
Geophysical Research Letters | Year: 2010
Spatial and temporal heterogeneity of ambient natural environments play a significant role in large scale transport phenomena. Uncertainty about spatio-temporal fluctuations in system parameters (e.g., flow velocity) make deterministic predictions of macroscopic system states (e.g., solute concentration) elusive. Distributions of system states generally exhibit highly non-Gaussian behavior, which cannot be captured solely by the corresponding mean and variance. Instead, these features of transport are described by the probability density function (PDF) of a system state, e.g., the PDF of concentration at a certain point in space and time. We study the PDF of a passive scalar that disperses in a random velocity field. We derive an explicit map between the velocity distribution and the scalar PDF, and obtain approximate solutions for the PDF of the normalized scalar. These solutions enable one to quantify explicitly the impact of dispersion on the evolution of the passive scalar PDF without recurrence to classical closure approximations used in mixing models. Copyright 2010 by the American Geophysical Union.
Lana A.,CSIC - Institute of Marine Sciences |
Simo R.,CSIC - Institute of Marine Sciences |
Vallina S.M.,Massachusetts Institute of Technology |
Atmospheric Chemistry and Physics | Year: 2012
Aerosols have a large potential to influence climate through their effects on the microphysics and optical properties of clouds and, hence, on the Earth's radiation budget. Aerosol-cloud interactions have been intensively studied in polluted air, but the possibility that the marine biosphere plays an important role in regulating cloud brightness in the pristine oceanic atmosphere remains largely unexplored. We used 9 yr of global satellite data and ocean climatologies to derive parameterizations of the temporal variability of (a) production fluxes of sulfur aerosols formed by the oxidation of the biogenic gas dimethylsulfide emitted from the sea surface; (b) production fluxes of secondary organic aerosols from biogenic organic volatiles; (c) emission fluxes of biogenic primary organic aerosols ejected by wind action on sea surface; and (d) emission fluxes of sea salt also lifted by the wind upon bubble bursting. Series of global monthly estimates of these fluxes were correlated to series of potential cloud condensation nuclei (CCN) numbers derived from satellite (MODIS). More detailed comparisons among weekly series of estimated fluxes and satellite-derived cloud droplet effective radius (r e) data were conducted at locations spread among polluted and clean regions of the oceanic atmosphere. The outcome of the statistical analysis was that positive correlation to CCN numbers and negative correlation to r e were common at mid and high latitude for sulfur and organic secondary aerosols, indicating both might be important in seeding cloud droplet activation. Conversely, primary aerosols (organic and sea salt) showed widespread positive correlations to CCN only at low latitudes. Correlations to r e were more variable, non-significant or positive, suggesting that, despite contributing to large shares of the marine aerosol mass, primary aerosols are not widespread major drivers of the variability of cloud microphysics. Validation against ground measurements pointed out that the parameterizations used captured fairly well the variability of aerosol production fluxes in most cases, yet some caution is warranted because there is room for further improvement, particularly for primary organic aerosol. Uncertainties and synergies are discussed, and recommendations of research needs are given. © 2012 Author(s).
Sanchez-Trujillo M.A.,CSIC - Institute of Natural Resources and Agriculture Biology of Seville |
Morillo E.,CSIC - Institute of Natural Resources and Agriculture Biology of Seville |
Villaverde J.,CSIC - Institute of Natural Resources and Agriculture Biology of Seville |
Environmental Pollution | Year: 2013
The objective of the present study was to characterise the polycyclic aromatic hydrocarbons (PAHs) content of an aged contaminated soil and to propose remediation techniques using cyclodextrins (CDs). Four CDs solutions were tested as soil decontamination tool and proved more efficient in extracting PAHs than when an aqueous solution was used; especially two chemically modified CDs resulted in higher extraction percentages than natural β-CD. The highest extraction percentages were obtained for 3-ring PAHs, because of the appropriate size and shape of these compounds relative to those of the hydrophobic cavities of the CDs studied. A detailed mechanistic interpretation of the chemical modification of CDs on the extraction of the different PAHs has been performed, and connected with the role that the different hydrophobicities of the PAHs play in the extraction behaviour observed for the 16 PAHs, limiting their accessibility and the remaining risk of those PAHs not extractable by CDs. © 2013 Elsevier Ltd. All rights reserved.
Calderon-Preciado D.,IDAEA |
Matamoros V.,University of Girona |
Science of the Total Environment | Year: 2011
Emerging contaminants have received much attention in recent years due to their presence in surface waters, but little attention has been paid to their occurrence in agricultural irrigation waters. This study investigated the occurrence of these compounds in an agricultural irrigation network in northeastern Spain and, for the first time, using two plant uptake models, estimated the concentration of selected micropollutants in crops. The concentration of micropollutants in agricultural irrigation waters ranged from 10 to 5130ngL -1 and exhibited some attenuation over the course of the irrigation network. Bromoform, chloroform, diclofenac, caffeine, ibuprofen, naproxen, methyl dihydrojasmonate, galaxolide, butylated hydroxytoluene, and butylated hydroxyanisole were the most abundant contaminants (>200ngL -1, on average). The estimated concentration of micropollutants in crops ranged from <1 to 7677ngkg -1, with the neutral compounds being the most abundant. Moreover, the predicted data obtained by fate models generally agreed with experimental data. Finally, human exposure to micropollutants through fruit and vegetable consumption was estimated to be 9.8μg per person and week (σ 27 contaminants detected). Further studies are needed to determine the health implications that the presence of these compounds in fruit and vegetables may have for consumers. © 2011 Elsevier B.V.
Feo M.L.,IDAEA |
Eljarrat E.,IDAEA |
Barcelo D.,IDAEA |
Barcelo D.,Catalan Institute for Water Research
Journal of Chromatography A | Year: 2010
A simple, efficient and environmentally friendly analytical methodology is proposed for extracting and preconcentrating pyrethroids from water samples prior to gas chromatography-negative ion chemical ionization mass spectrometry (GC-NCI-MS) analysis. Fourteen pyrethroids were selected for this work: bifenthrin, cyfluthrin, λ-cyhalothrin, cypermethrin, deltamethrin, esfenvalerate, fenvalerate, fenpropathrin, τ-fluvalinate, permethrin, phenothrin, resmethrin, tetramethrin and tralomethrin. The method is based on ultrasound-assisted emulsification-extraction (UAEE) of a water-immiscible solvent in an aqueous medium. Chloroform was used as extraction solvent in the UAEE technique. Target analytes were quantitatively extracted achieving an enrichment factor of 200 when 20mL aliquot of pure water spiked with pyrethroid standards was extracted. The method was also evaluated with tap water and river water samples. Method detection limits (MDLs) ranged from 0.03 to 35.8ngL-1 with RSDs values ≤3-25% (n=5). The coefficients of estimation of the calibration curves obtained following the proposed methodology were ≥0.998. Recovery values were in the range of 45-106%, showing satisfactory robustness of the method for analyzing pyrethroids in water samples. The proposed methodology was applied for the analysis of river water samples. Cypermethrin was detected at concentration levels ranging from 4.94 to 30.5ngL-1. © 2010 Elsevier B.V.