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Letteratura scientifica selezionata sul tema "Contaminant transfers"

Autore: Grafiati

Pubblicato: 28 settembre 2024

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Articoli di riviste sul tema "Contaminant transfers"

Sterpenich, J., E. C. Gaucher, N. H. Schovsbo, J. G. Lerat, R. Mosser-Ruck e J. Pironon. "Geochemistry of Aquifer in Contact with Alum Shale: Evidence of Limited Contaminant Transfers". Procedia Earth and Planetary Science 17 (2017): 786–89. http://dx.doi.org/10.1016/j.proeps.2017.01.029.

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Rivoira, Luca, Michele Castiglioni, Nicola Nurra, Marco Battuello, Rocco Mussat Sartor, Livio Favaro e Maria Concetta Bruzzoniti. "Polycyclic Aromatic Hydrocarbons and Polychlorinated Biphenyls in Seawater, Sediment and Biota of Neritic Ecosystems: Occurrence and Partition Study in Southern Ligurian Sea". Applied Sciences 12, n. 5 (1 marzo 2022): 2564. http://dx.doi.org/10.3390/app12052564.

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The Mediterranean Sea is subjected to a high anthropic pressure, which determines direct or indirect discharges of persistent organic pollutants deriving from intensive industrial activities. These compounds could easily enter and contaminate the whole marine compartment, with possible transfers (and contamination) among water, sediment and biota. Based on the above-mentioned assumptions, in this work we studied the presence of 16 polycyclic aromatic hydrocarbons (PAHs) and 14 dioxin and non-dioxin-like polychlorinated biphenyls (PCBs) in the neritic protected marine area of the Southern Ligurian Sea, affected by the impact of human activities. The study was focused on the possible partition of micropollutants within seawater, sediment and zooplankton. Results showed that both seasonal and anthropic causes strongly affect contaminant transfer behaviors, with summertime periods more impacted by PAH and PCB contamination. Regarding the PAH contamination, low molecular weight congeners were mainly detected in the target matrices, revealing concentrations up to 1 µg/L in seawater (anthracene), 250 µg/Kg in sediments (benzo[b]fluoranthene) and 2.3 mg/Kg in carnivorous copepods. Concerning PCBs, only few congeners were detected in the matrices studied. To better understand the occurrence of preferential bioaccumulation pathways in zooplankton, partition studies were also performed in several taxa (hyperbenthic Isopoda, holoplanktonic crustacean copepods and ichthyoplankton) through the calculation of BAF values, observing that both living and feeding habits could influence the bioaccumulation process.

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Younsi, Zohir, Lounes Koufi e Hassane Naji. "Numerical study of the effects of ventilated cavities outlet location on thermal comfort and air quality". International Journal of Numerical Methods for Heat & Fluid Flow 29, n. 11 (4 novembre 2019): 4462–83. http://dx.doi.org/10.1108/hff-09-2018-0518.

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Purpose A comprehensive investigation on the outlet air position effects on the thermal comfort and air quality has been achieved. In addition, airflow and temperature distributions in ventilated cavities filled with an air-CO2 mixture with mixed convection are predicted. The airflow enters from the cavity through an opening in the lower side of the left vertical wall and exits through the opening in one wall of the cavity. This paper aims to investigate the outlet location effect, four different placement configurations of output ports are considered. Three of them are placed on the upper side and the fourth on top of the opposite side of the inlet opening. A uniform heat and CO2 contaminant source are applied on the left vertical wall, while the remaining walls are impermeable and adiabatic to heat and solute. The cooling efficiency inside the enclosure and the average fluid temperature are computed for different Reynolds and Rayleigh numbers to find the most suitable fluid outlet position that ensures indoor comfortable conditions while effectively removing heat and the contaminant. This is demonstrated by three relevant indices, namely, the effectiveness for heat removal, the contaminant removal and the index of indoor air quality. Design/methodology/approach The simulations were performed via the finite-volume scSTREAM CFD solver V11. Three different values of CO2 amount are considered, namely, 103, 2 × 103 and 3 × 103 ppm, the Reynolds number being in the range 100 ≤ Re ≤ 800. Findings Based on the findings obtained, it is the configuration whose air outlet is placed near the heat source and the contaminant, which provides a better air distribution and a ventilation efficiency compared to the others ventilation strategies. Originality/value The studies on heat and mass transfers by natural and forced convection in ventilated cavities remain a fruitful research topic. Thereby, such a study deals with different ventilation strategies through cavities containing an air-CO2 mixture subjected to a mixed regime. In particular, the air inlet velocity and contaminant sources’ effects on thermal comfort and air quality have been investigated.

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Laceby, J. P., C. Chartin, O. Evrard, Y. Onda, L. Garcia-Sanchez e O. Cerdan. "Rainfall erosivity in subtropical catchments and implications for erosion and particle-bound contaminant transfer: a case-study of the Fukushima region". Hydrology and Earth System Sciences Discussions 12, n. 7 (30 luglio 2015): 7225–66. http://dx.doi.org/10.5194/hessd-12-7225-2015.

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Abstract. The Fukushima Dai-ichi nuclear power plant (FDNPP) accident in March 2011 resulted in a significant fallout of radiocesium over the Fukushima region. After reaching the soil surface, radiocesium is almost irreversibly bound to fine soil particles. Thereafter, rainfall and snow melt run-off events transfer particle-bound radiocesium downstream. Erosion models, such as the Universal Soil Loss Equation (USLE), depict a proportional relationship between rainfall and soil erosion. As radiocesium is tightly bound to fine soil and sediment particles, characterizing the rainfall regime of the fallout-impacted region is fundamental to modelling and predicting radiocesium migration. Accordingly, monthly and annual rainfall data from ~ 60 meteorological stations within a 100 km radius of the FDNPP were analysed. Monthly rainfall erosivity maps were developed for the Fukushima coastal catchments illustrating the spatial heterogeneity of rainfall erosivity in the region. The mean average rainfall in the Fukushima region was 1387 mm yr−1 (σ 230) with the mean rainfall erosivity being 2785 MJ mm ha−1 yr−1 (σ 1359). The results indicate that the majority of rainfall (60 %) and rainfall erosivity (86 %) occurs between June and October. During the year, rainfall erosivity evolves positively from northwest to southeast in the eastern part of the prefecture, whereas a positive gradient from north to south occurs in July and August, the most erosive months of the year. During the typhoon season, the coastal plain and eastern mountainous areas of the Fukushima prefecture, including a large part of the contamination plume, are most impacted by erosive events. Understanding these rainfall patterns, particularly their spatial and temporal variation, is fundamental to managing soil and particle-bound radiocesium transfers in the Fukushima region. Moreover, understanding the impact of typhoons is important for managing sediment transfers in subtropical regions impacted by cyclonic activity.

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Warmka, Anna, Erin L. Cortus, Kevin A. Janni, Abby Schuft e Sally Noll. "Opportunities and Methods for Using Fluorescent Gel as a Proxy for Pathogen Transfer in Biosecurity Research". Journal of Agricultural Safety and Health 29, n. 1 (2023): 57–70. http://dx.doi.org/10.13031/jash.15253.

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Highlights While fluorescing gel may evaporate from a surface, luminance of the surface does not change. Fluorescing gel exhibits thresholds beyond which additional gel density does not increase luminance. Fluorescing gel only transfers between surfaces when it is wet. There are limits to relating luminance and mass transfer. Fluorescent material is a useful proxy for contamination transfer demonstration and research. Abstract. Glo Germ fluorescing material is a popular tool for teaching and researching contaminant transfer in and out of agriculture. The objectives of this paper were to: (1) quantify relationships between gel area density (mass per unit area) on a surface and its luminance, and (2) identify factors important in measuring Glo Germ gel transfer from one surface to another. Varying densities of Glo Germ gel were applied to paper, plastic, and rubber surfaces; each combination was replicated three times. Digital images collected over one hour were analyzed for luminance (the average gray value per unit area) under ultraviolet light. Changes in mass were also measured. For the gel transfer objective, a fixed weight was placed over varying wet and dried fluorescent material densities on paper and plastic surfaces. Gel masses were weighed, and images of the surface and receptor were taken before and after transfer. Evaporation was significantly faster (p = 0.0019) on the paper surface compared to the plastic surface. The luminance did not change as the gel evaporated from either surface. For each material, luminance initially increased with increasing density until a threshold, after which additional fluorescing gel density did not change luminance. The thresholds for paper, plastic, and rubber surfaces were 0.018, 0.014, and 0.041 g cm-2, respectively. Wet gel transfer test results suggest that transfer is easier to quantify on the receptor than the source. The dried gel did not exhibit measurable transfer. This research found limitations in equating mass transfer and luminance, but luminance threshold values can inform maximum Glo Germ application for imaging purposes. These research results support continued research and outreach with fluorescent material to reduce and prevent the spread of disease or other harmful contaminants in food and animal production. Keywords: Biosecurity, Fluorescence, Luminance, Mass transfer.

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Monaghan, R. M., L. C. Smith e R. W. Muirhead. "Pathways of contaminant transfers to water from an artificially-drained soil under intensive grazing by dairy cows". Agriculture, Ecosystems & Environment 220 (marzo 2016): 76–88. http://dx.doi.org/10.1016/j.agee.2015.12.024.

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Perou, A. L., e J. M. Vergnaud. "Process of contaminant transfers during coextrusion of food packages made from recycled layer and virgin polymer layer". Plastics, Rubber and Composites 28, n. 2 (febbraio 1999): 74–79. http://dx.doi.org/10.1179/146580199101540132.

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Tisseau, M. A., N. Fauchon, J. Cavard e T. Vandevelde. "Pesticide contamination of water resources: a case study - the rivers in the Paris region". Water Science and Technology 34, n. 7-8 (1 ottobre 1996): 147–52. http://dx.doi.org/10.2166/wst.1996.0614.

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For a number of years, the Compagnie Générale des Eaux has been studying pesticide contamination of surface water in order to better understand the origins and the main transfer mechanisms of these pollutants into water resources. Sampling campaigns are being carried out on the three main rivers of the Paris area to monitor a number of products from the triazine and urea families. This monitoring has confirmed the extension of agricultural non-point source pollution. The products being sought are present in the three rivers and, in most cases, in significant concentrations. Atrazine is the most important contaminant. Measured concentrations exceed the value of 100 ng/l most of the time, thus proving that the aquifers drained by the three rivers are contaminated. For a period of several months every year, concentrations approaching 1000 ng/l are observed in all the catchment areas being studied. These are the result of rapid transfers of atrazine in run-off water. This surface run-off transfer mode also seems to be applicable to the ureas found in surface water, especially during the periods when the products are used to treat crops. These works underline the complexity of agricultural non-point source pollution phenomena. They permit the identification of the predominant mechanisms operating in the transfer of the products. This is the first step towards setting up preventive measures and developing pollution forecasting tools.

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Tappin, A. D., P. J. Statham, J. D. Burton e S. Gellers-Barkmann. "Distributions and fluxes of contaminant metals in the North Sea: comparisons between field measurements and model simulations using NOSTRADAMUS". Environmental Chemistry 5, n. 1 (2008): 51. http://dx.doi.org/10.1071/en07033.

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Environmental context. The North Sea, which is of significant ecological, economic and recreational value to NW Europe, has for many years received enhanced inputs of contaminant metals arising from human activity around its shores. Fluxes of copper, nickel, zinc, chromium and other constituents throughout the southern North Sea were estimated using a numerical model in order to identify the main sources and sinks for these metals. Comparison of model output with independent and other data showed good agreement in general. The results indicate that models of the kind developed here can be used to provide useful information on contaminant metal transport in coastal waters. Abstract. The steady-state 2-D vertically integrated numerical transport model NOSTRADAMUS has been used to simulate concentrations, distributions and fluxes of dissolved and particulate Cu, Cr, Ni and Zn in the southern North Sea between 51 and 56°N. The model results for the metals, and also for salinity and suspended sediments, were compared with field measurements from the Natural Environment Research Council (NERC) North Sea Project (NSP). The model generated realistic concentrations of all constituents, and in many cases reproduced the major features of the distributions, i.e. higher concentrations in the coastal zones and lower values in the central region. The sensitivity of the model results to variations in forcing data was extensively tested. In most cases, the default data provided the best results (quantified by residual sums of squares scores) despite no formal model calibration having been undertaken. Simulated fluxes indicated that metal inputs across the open sea boundaries were significant (Cu, 51%; Cr, 36%; Ni, 57%; Zn, 32%), although for Cu, Ni and Zn, river inputs were also important (13–15%). Metal transfers associated with particle settling and resuspension were significant (23–55%), and resuspended sediments were a minor net source, relative to particle settling, of Cu, Ni and Zn to the water column over the simulated year. In contrast, the resuspension of sediment from the seabed appeared to be a major source of Cr to the water column, a feature not explained at present. The major export from the North Sea in the model was through the northern boundary adjacent to the coast of Denmark. The fraction lost was in the range 61%, for Zn, to 90%, for Cr. Model results were compared with available independent data. The comparisons showed that the simulated constituent transfers approximated reasonably well with contemporary understanding of metal, and other constituent, fluxes in this region. These outcomes serve to emphasise the underlying capabilities of the model, and it can be concluded that NOSTRADAMUS provides the basis for heuristic studies of contaminant metals in the southern North Sea.

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Monaghan, RM, DJ Houlbrooke e LC Smith. "The use of low-rate sprinkler application systems for applying farm dairy effluent to land to reduce contaminant transfers". New Zealand Journal of Agricultural Research 53, n. 4 (18 novembre 2010): 389–402. http://dx.doi.org/10.1080/00288233.2010.505943.

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Più fonti

Tesi sul tema "Contaminant transfers"

Bonnière, Antoine. "L'approche par multi-traçage géochimique, isotopique et organique comme outil d'étude de l'origine et du transfert des contaminants dans les eaux souterraines : Application à la nappe de la Vistrenque". Electronic Thesis or Diss., Nîmes, 2024. http://www.theses.fr/2024NIME0004.

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Les masses d'eaux souterraines soutiennent 65% de l’alimentation en eau potable en France. L'accroissement des pressions anthropiques entraîne des pollutions des eaux et la fermeture de captages. La diversité des pollutions existantes et l'apparition de contaminants émergents requièrent une compréhension globale du fonctionnement des masses d’eau souterraine. La mise en place de plan d'actions par les collectivités et gestionnaires de la ressource nécessite d’identifier les origines des contaminants et de définir les zones vulnérables avec précision. L’objectif de ce travail consiste en la mise en place d’une approche multi-traceurs sur la nappe de la Vistrenque (Gard), afin d’étudier l’origine et le transfert des contaminants. Les analyses portent sur les traceurs naturels d’origine de l’eau (les éléments majeurs, mineurs et traces), les isotopes stables de la molécule d’eau (δ18O/δ2H-H2O), les isotopes stables de l’azote des nitrates δ15N/δ18O-NO3-, l’isotope du bore δ11B, le gadolinium (Gd), ainsi que sur un cortège de molécules organiques incluant pesticides et résidus médicamenteux, servant eux-mêmes de traceurs. L'application de cette approche multi-traceurs a permis l'identification de l'origine des nitrates sur des zones de captages prioritaires présentant une superposition de sources de nitrate d'origines agricoles et urbaines. L’analyse de la signature isotopique en δ15N/δ18O-NO3- des nitrates facilement mobilisables des sols s’est montrée être un outil efficace pour caractériser les pollutions azotées en contexte agricole. En comparant les signatures isotopiques des sols et des eaux souterraines, les parcelles à l'origine de la contamination ont été identifiées. En plus d'une contamination agricole, l'infiltration d'un panache d'effluent de station d'épuration dans la nappe a montré l'importance de l'étude des résidus pharmaceutiques et la vulnérabilité des aquifères face aux contaminants émergents. L'ensemble de ces observations a permis de poser les bases pour transposer cette approche à d'autres secteurs d'étude, en se focalisant sur l'opérationnalité de l'approche par multi-traçage géochimique, isotopique et organique
In France, groundwater supports 65% of the drinking water supply. The increasing pressures of human activities lead to water pollution and the closure of water supply wells. The diversity of existing pollutants and the emergence of new contaminants require a comprehensive understanding of the functioning of groundwater bodies. The implementation of action plans by local authorities and resource managers requires identifying the origins of contaminants and defining vulnerable areas with precision. The objective of this work is to establish a multi-tracer approach on the Vistrenque aquifer (France, Gard), to study the origin and transfer of contaminants. Analyses include natural tracers of water origin (major, minor, and trace elements), stable isotopes of water molecules (δ18O/δ2H-H2O), stable nitrogen isotopes of nitrates δ15N/δ18O-NO3-, boron isotope δ11B, gadolinium (Gd), as well as a range of organic molecules including pesticides and pharmaceutical residues, serving as tracers themselves. Using this multi-tracer approach, it was possible to identify the origin of nitrates in water catchment areas where agricultural and urban nitrate sources overlap. Analysis of the isotopic signature in δ15N/δ18O-NO3- of easily mobilized nitrates in soils has proved to be an effective tool for characterizing nitrogen pollution in an agricultural context. The land parcels responsible for contamination were identified, based on the comparison of the isotopic signatures of soils and groundwater. In addition to agricultural contamination, the infiltration of an urban effluent plume from a wastewater treatment plant into the aquifer highlighted the importance of studying the occurrence of pharmaceutical residues and the vulnerability of aquifers to emerging contaminants. All these observations have laid the groundwork for extending this approach to other study areas, focusing on the operability of the geochemical, isotopic, and organic multi-tracer approach

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Froger, Claire. "Sources et dynamiques spatiales et temporelles des contaminations en éléments traces et hydrocarbures aromatiques polycycliques du continuum atmosphère - sol - rivière d'un bassin versant contrasté". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS394/document.

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Le développement des activités humaines, notamment industrielles, depuis le 19ième siècle a engendré une contamination massive de l’atmosphère à la rivière, en passant par la biosphère et les sols. Si les contaminations ont fortement diminué depuis la fin des années 1960, elles persistent notamment en milieu urbain, où se concentrent un grand nombre d’activités humaines. Afin de pouvoir gérer au mieux la pollution, il est nécessaire de comprendre la dynamique de transfert des contaminants, ainsi que leurs sources, à l’échelle du continuum atmosphère – sol – rivière. Cette étude a donc pour objectif d’évaluer les variations temporelles et spatiales de deux types de contaminants historiques, les hydrocarbures aromatiques polycycliques (HAP) et certains éléments traces (ET), à l’échelle du bassin versant de l’Orge (950 km2), présentant une urbanisation croissante d’amont en aval. Plusieurs approches ont été utilisées pour tracer les transferts de particules en rivière (radionucléides ⁷Be, ²¹⁰Pb, ¹³⁷Cs), et déterminer les sources de Pb (isotopes du Pb), et les sources de HAP (rapports de molécules).Les résultats ont mis en évidence un impact important des zones urbaines sur la qualité de la rivière Orge en aval du bassin : contamination importante en métaux (Cu, Zn, Sb, Pb) et en HAP de la phase particulaire, et des niveaux élevés en SO42⁻, Na⁺ et Cl⁻, Cu, Zn et Pb dans la phase dissoute. Le traçage des sédiments par les radionucléides a permis d’observer un apport de particules provenant du ruissellement urbain en aval, et d’identifier les particules de route (ou Road Deposited Sediment) comme source principale. Les signatures isotopiques du Pb ainsi que les signatures en HAP permettent de confirmer que le ruissellement urbain est le principal vecteur de contamination. Les estimations des flux d’ET et HAP annuels et saisonniers entrants (retombées atmosphériques) et sortants (exportés par la rivière) ont mis en évidence une accumulation globale à l’échelle du bassin, qui comporte déjà un stock important de contaminants dans ses sols. Cette étude montre ainsi l’importance d’étudier la Zone Critique dans son ensemble afin d’évaluer la dynamique des contaminations au sein et entre ses différents compartiments, et met en évidence l’efficacité du couplage de plusieurs approches afin de comprendre le système entier. Ces résultats pourraient à terme permettre l’établissement d’un modèle de transfert de contaminations au sein d’un bassin urbain
The development of human societies since the 19th century has led to deleterious impacts on the Critical Zone (from atmosphere to river, including biosphere and soils). Despite the decrease of pollutions since the late 1960’s, contaminations remain especially in urban environment, concentrating human activities. To better manage this pollution, it is necessary to understand the dynamics and pathways of contaminants through the atmosphere – soil – river continuum. The goal of this study in thus to evaluate the temporal and spatial variations of two contaminants (polycyclic aromatic hydrocarbons (PAH) and trace elements (TE)) in the Orge River catchment (900 km2, France) being under increasing urban pressure from up to downstream. Several fingerprinting approaches were used to trace sediment dynamics in the river (radionuclides: ⁷Be, ²¹⁰Pb, ¹³⁷Cs), to identify lead sources (lead isotopes) and PAH sources (PAH molecular ratios). The results demonstrated the strong influence of downstream urban areas on the river quality, with an increasing contamination for Cu, Zn, Sb, Pb and PAH in the particulate phase, and for SO42⁻, Na⁺ et Cl⁻, Cu, Zn and Pb in the dissolved phase. The sediment fingerprinting using radionuclides revealed a significant input of particles originating from urban areas and transferred through urban runoff, and identified road deposited sediments as the major source of contaminated particles downstream. Source tracking of Pb and PAH confirmed urban runoff as the main pathway of river contamination. In addition, annual and seasonal PAH and TE fluxes were estimated respectively for the atmospheric inputs, and riverine exports and revealed a global accumulation of contaminant over the catchment, already containing a significant stock of pollutants in its soils. Finally, this study highlights the need to integrate the Critical Zone and the potential of coupling multiples tracking approaches to properly evaluate the contaminant dynamics. These results may be used to establish a model of contaminants transfer in urban catchments

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Weber, Sofie Aimee. "Contaminant transport and mass transfer to runoff including infiltration". Thesis, The University of Arizona, 1997. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_etd_hy0151_sip1_w.pdf&type=application/pdf.

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Martin, Sébastien. "Mécanismes de sorption et d'oxydoréduction à l'interface oxyde/solution : couplage chimie / transport". Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S157.

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Au vu de l'omniprésence des oxydes de fer dans le milieu naturel, et en particulier la goethite et l'hématite qui sont les formes les plus stables, mais aussi de la prolifération des contaminants émergents dans l'environnement, comme les fluoroquinolones, notre objectif a été d'étudier leur réactivité et de définir les mécanismes de sorption et d'oxydoréduction à l'interface oxyde/solution dans des conditions statiques (batch) et hydrodynamiques contrôlées (colonne) en couplant une étude macroscopique (techniques chromatographiques, LC/MS, LC/UV) avec une approche microscopique (spectroscopie vibrationnelle et XPS) et de modélisation mécanistique (TPM et CD-MUSIC). Ces travaux mettent en évidence les principaux mécanismes responsables de la transformation des molécules organiques à la surface d'un oxyde de fer, et donc fournissent des informations nécessaires à la compréhension du devenir des contaminants émergents dans l'environnement
Given the ubiquity of iron oxides in environmental settings, particularly goethite and hematite, the most stable forms, but also the proliferation of emerging contaminants, such as fluoroquinolones, in the environment, our goal was to study their reactivity and describe mechanisms of sorption and redox at oxide /solution interfaces in static batch) and hydrodynamic conditions (column) by coupling a macroscopic study (LC/MS, LC/UV) with a microscopic/molecular approach (vibrational spectroscopy and XPS) and mechanistic modeling (TPM and CD-MUSIC).. These works highlight the main mechanisms responsible of the transformation of organic molecules on iron oxide surfaces and thus provide valuable information necessary for the understanding of the fate of emerging contaminants in the environment

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Rosca, Iosif-Daniel. "Applications du transfert de matière et chaleur : transfert de contaminant entre emballage cylindrique et aliment solide". Saint-Etienne, 1998. http://www.theses.fr/1998STET4027.

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En réponse à un grand nombre de travaux réalisés sur la migration de contaminants des emballages polymères dans l'aliment, ce travail est une approche théorique sur le procédé de diffusion dans l'aliment solide contenu dans de bouteilles cylindriques. Des modèles mathématiques et numériques, prenant en compte les différents paramètres sont développés dans le premier chapitre, pour représenter la diffusion du contaminant situé dans une bouteille faite d'une seule couche de polymère, lorsque l'aliment est solide. Les paramètres nécessaires au transfert sont définis. Le recyclage des emballages polymères dans des nouveaux emballages pose de problèmes aigus. Dans le second chapitre, des bouteilles formées de bi- et tri- couches dans lesquelles une couche de polymère vierge isole la couche recyclée de l'aliment, sont étudiés. Ainsi l'effet de la couche vierge protectrice ou barrière fonctionnelle, sur le transfert de contaminant est bien précisée, en considérant notamment son épaisseur. Les bouteilles sont préparées par extrusion-soufflage à haute température. Ainsi durant une courte période le polymère est fondu, impliquant nécessairement une diffusion très rapide du contaminant. Dans le troisième chapitre, les procédés complexes du transfert thermique lors de l'étape de refroidissement dans l'air et le transfert de contaminant qui en résultent, sont étudiés d'une façon théorique. Les simulations numériques ont permis de définir l'importance de nombreux paramètres intéressant lors du transfert thermique et de matière. Il parait possible déjà d'optimiser ces paramètres pour réduire ce transfert. L'effet de ces transferts durant l'extrusion-soufflage sur le temps de protection de l'aliment est aussi établi. Enfin, pour des raisons pratiques, des relations simples ont été établies, qui permettent d'estimer le temps nécessaire pour atteindre une contamination de l'aliment donnée avec des systèmes bouteilles-aliment solide, en fonction des paramètres définis dans l'étude

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Sime, Kristian John. "Characterisation and surface analysis of polymer interfaces used in dye diffusion thermal transfer printing". Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/10559.

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The research involved determining the processes that occur during dye diffusion thermal transfer printing. Dye diffusion printing is a novel method of printing photo quality graphics from a personal computer. The process involves two polymer films coming into contact, one containing a dye, and the diffusion of the dye from this donor sheet onto the receiving sheet using heating elements to drive the diffusion process. In this high temperature, high pressure, and short time scale regime undesirable adhesion between the two polymer sheets is observed. It is this adhesion and its mechanisms that were investigated. Several types of homopolymers were used in.an attempt to obtain information on the processes involved in the adhesion of the two films during the printing stage. Initially dyes were absent from the polymer films to examine the polymer adhesion alone. It was hoped that the principal factors involved in the unusual joint forming conditions could be explained. The unusual conditions are high heat (250°C) and short time span (10-15 milliseconds). Polystyrene, poly (methyl methacrylate) and poly (vinyl acetate) were chosen to determine the effect of Glass Transition Temperature (T g), surface energies and molecular weight on the polymer adhesion. Initial results showed that the adhesion was a complex system. but it became clear that the t g of the polymers and the presence of small molecules and contaminants· were very important. Work with commercial polymers was undertaken to transfer the knowledge gained from the homopolymers to the more complicated commercial systems using poly (vinyl. chloride) and poly (vinyl butyral). To expand the understanding of the results small molecules and dyes were added to these commercial polymers to examine their effects. The surface of the samples were analysed using X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FTIR). This was used to determine if there was any migration of the small molecules to the surface of the polymer films. It was also useful in indicating the location of the dyes and how much penetration into the polymers is achieved by them. Atomic Force Microscopy (AFM) was implemented to analyse the surface morphology and gave an insight into the mechanism of the small molecule migration. The conclusions drawn were that the presence of small molecules had significant affect on the adhesion of the polymers. Compatible small molecules would act as plasticisers and lower the T g of the polymers giving rise to higher adhesion. Small molecules that were incompatible were found to migrate to the surface in large quantities and would act as weak boundary layers, significantly reducing the adhesion. Work in this area has shown that an autolayering mechanism is occurring that may be useful in producing a release mechanism for the commercial products.

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Gatel, Laura. "Construction et évaluation d'un modèle de transport de contaminants réactif couplé surface-subsurface à l'échelle du versant". Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAU001/document.

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L'utilisation de pesticides sur les surfaces agricoles conduit à une contamination généralisée des eaux de surface et de subsurface en France. Dans l'attente d'une évolution profonde des pratiques agricoles et d'une baisse durable de l'utilisation des pesticides, il est intéressant de chercher à limiter des transferts des zones agricoles aux zones aquatiques. Pour mieux agir sur les voies de transfert, il est nécessaire d'approfondir les connaissances des processus en jeu et de leurs interactions éventuelles et de tirer au mieux partie des observations du terrain.L'objectif de cette thèse est l'intégration de processus de transferts réactif dans le modèle hydrologique à base physique CATHY (CATchment HYdrology), capable de simuler en 3 dimensions les écoulements de l'eau de façon couplée surface-subsurface et le transport advectif dans des situations variablement saturées. En subsurface, les processus d'adsorption linéaire et de dégradation du premier ordre sont implémentés. Un module de mélange des solutés entre la lame ruisselante et la première couche de sol est ajouté, qui permet de simuler la remobilisation des solutés de la subsurface dans le ruissellement. Le couplage surface-subsurface des écoulement est très efficace dans ce modèle, et le couplage du transport de soluté adoptant la même stratégie a été amélioré pour mieux respecter la conservation de la masse.Le modèle est en premier lieu testé sur des données issues d'expérimentations de transfert de subsurface sur une maquette de laboratoire à petite échelle (2 m de long, o.5 m de large, 1 m de profondeur). Les résultats sont confrontés aux chroniques de flux massiques observées et une analyse de sensibilité de type Morris est menée. Le modèle est capable de reproduire de façon satisfaisante les observations, et très satisfaisante après une légère calibration. Les conductivités à saturation horizontale et verticale, la porosité et le paramètre $n$ de la courbe de rétention influencent de façon non négligeable les résultats hydrodynamiques et de transfert de soluté. Dans un second temps, le modèle est évalué sur les données issus d'un versant viticole réel (0.6 ha) dans un contexte orageux avec de fortes interactions surface-subsurface. Une analyse de sensibilité globale est menée, et met en valeur les mêmes paramètres que la méthode de Morris. Les interactions entre les paramètres influencent fortement la variabilité des sorties hydrodynamiques et de transfert. La conservation de la masse est très correctement assurée malgré la complexité de la simulation.Le modèle auquel on aboutit correspond bien aux objectifs de départ, sa validation est solide, même si elle n'est rigoureusement valable que dans les contextes précis où elle a été réalisée. On a montré que le modèle était robuste et capable de reproduire des données observées. D'autres processus manquent encore pour représenter toutes les voies de transfert à l'échelle du versant, notamment la représentation du transfert préférentiel en subsurface et du transport sédimentaire en surface
Pesticide use on agricultural surfaces leads to a broad surface and subsurface water contamination in France. Awaiting a deep agricultural practices evolution and a sustained fall of the pesticide use, it is of interest to limit transfers form agricultural fields to rivers. In order to constrain those transfers, a deepen knowledge of processes at stake and their potential interactions is necessary, as well as taking full advantages of fields observations.The aim of this PhD is the reactive transfer processes integration in the Hydrological physically-based model CATHY (CATchment HYdrology) which simulates surface-subsurface coupled water flow and advectiv solute transport in three dimensions and in variably saturated situations. Linear adsorption and first order decay are implemented in subsurface. A mixing modules is added, and evens the concentration between surface runoff and subsurface first layer. This module simulates the solute mobilisation from soil to surface runoff. The water flow surface-subsurface coupling procedure is very accurate in CATHY, and the transport coupling procedure is improve in order to respect the mass conservation.The model is first evaluated on subsurface transfer laboratory experimentation data at a small scale (2 m long, o.5 m wide, 1 m deep). Results are compared to mass flux evolution in time and a Morris sensitivity analysis is conducted. The model is able to acceptably reproduce observation, and properly after a slight calibration. Horizontal and vertical saturated conductivities, porosity and the $n$ parameter of retention curve significantly influence hydrodynamics and solute transport. As a second step, the model is evaluated on data from a field wine hillslope on an intense rain event, therefore in a context with a lot of surface-subsurface interactions. A global sensitivity analysis is conducted and highlights same parameters as the Morris method. Interactions between parameters highly influence the variability of hydrodynamic and solute transfer outputs. Mass conservation is accurate despite the complexity of the context.The resulting model meets the objectives, its evaluation is strong even if its theoretically only valid in the precise context in which the evaluations where conducted. The model is robust and able to reproduce observed data. Some complementary processes are still missing in the model to properly represent transfer ways at the hillslope scale, such as subsurface preferential transfers and surface sedimentary transport

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Marchand, Estelle. "Analyse de sensibilité déterministe pour la simulation numérique du transfert de contaminants". Phd thesis, Université Paris Dauphine - Paris IX, 2007. http://tel.archives-ouvertes.fr/tel-00271632.

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Les questions de sûreté et d'incertitudes sont au centre des études de faisabilité pour un site de stockage souterrain de déchets nucléaires, en particulier l'évaluation des incertitudes sur les indicateurs de sûreté qui sont dues aux incertitudes sur les propriétés du sous-sol et des contaminants. L'approche globale par les méthodes probabilistes de type Monte Carlo fournit de bons résultats, mais elle demande un grand nombre de simulations. La méthode déterministe étudiée ici est complémentaire. Reposant sur la décomposition en valeurs singulières de la dérivée du modèle, elle ne donne qu'une information locale, mais elle est beaucoup moins coûteuse en temps de calcul. Le modèle d'écoulement suit la loi de Darcy et le transport des radionucléides autour du site de stockage est modélisé par une équation de diffusion-convection linéaire. Différentiation à la main et différentiation automatique sont comparées sur ces modèles en mode direct et en mode adjoint. Une étude comparée des deux approches probabiliste et déterministe pour l'analyse de la sensibilité des flux de contaminants aux exutoires par rapport aux variations des paramètres d'entrée est menée sur des données réalistes fournies par l'ANDRA. Des outils génériques d'analyse de sensibilité et de couplage de code sont développés en langage Caml. Ils permettent à l'utilisateur de ces plates-formes génériques de ne fournir que la partie spécifique de l'application dans le langage de son choix. Une étude sur les écoulements diphasiques eau/air partiellement saturés en hydrogéologie porte sur les limitations des approximations de Richards et de la formulation en pression globale issue du domaine pétrolier.

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Chen, Hua. "Investigation of Contaminant Transport in Tidally-Influenced Aquifers: Experiment and Analysis". ScholarWorks @ UVM, 2010. http://scholarworks.uvm.edu/graddis/43.

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Tidally-induced head fluctuation is a natural phenomenon in coastal regions. The discharge of groundwater through sediments will occur anywhere that the aquifer is hydraulically connected to a surface water body and the time averaged tidally-influenced water level in the aquifer is higher than sea level, and almost all coastal regions are subject to such flow. With the development of coastal areas, the discharge of groundwater contaminants into tidally affected coastal water bodies has become a significant problem. Biota that live in the benthic region are known to be sensitive to the concentration of discharging anthropogenic chemical compounds. Thus the contaminant concentration entering the benthos is of very significant practical importance and its study is the focus of this dissertation. An investigation of the effect of tides on the concentration of groundwater contaminants discharging to a surface water body is studied using a one-dimensional homogeneous sand column. Results of the experiment are confirmed using a three-dimensional heterogeneous groundwater tank model. A constant water level is imposed upgradient, and the downgradient water level is controlled by a wave generator that controls the hydraulic head to mimic a 12 hour tidal fluctuation. The experimental results demonstrate that the tidal fluctuations in the downgradient reservoir result in a decrease in average contaminant concentration at the point of groundwater discharge to the surface-water body. The further upstream the well is located, the smaller the amplitude of the concentration oscillation. In addition, upstream migration of concentration oscillations is observed in spite of a net downgradient flow. Fourier analysis suggests that the dominant frequency of the peaks of pressure and chemical data at different locations along the length of the column is identically two cycles per day and that the amplitudes of the concentration oscillations increase with time at measurement locations at the upstream responding probes. As the classical groundwater flow and transport model cannot reproduce the phenomena we observed, an innovative multi-mobility model, is proposed with one highly mobile liquid phase, one less mobile liquid phase and a solid phase. Averaging theory is applied to develop the mass conservation equation from the microscale to the macroscale and facilitate the reduction of dimensionality to obtain one-dimensional governing equations with closure relations. A new finite volume method is utilized to solve the resulting equations. The simulation confirms the existence of the enhanced tidally-induced mixing process.

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Oursel, Benjamin. "Transferts et dynamique des contaminants métalliques en zone côtière. : Impact d’une grande agglomération méditerranéenne". Thesis, Toulon, 2013. http://www.theses.fr/2013TOUL0019/document.

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L’étude réalisée lors de ce travail de thèse porte sur l’évaluation de l'impact de l’agglomération Marseillaise sur le milieu côtier à travers la quantification des éléments traces métalliques (ETM) et du carbone organique. Sur le littoral méditerranéen français, Marseille représente la plus grande agglomération (~ 1.7M Ha) et possède la station d’épuration (STEP) enterrée la plus grande d’Europe (capacité de 1.62M équivalent-habitants), avec une façade directement ouverte sur la Méditerranée. L’impact de cette zone urbaine et industrialisée (flux brut) sur la zone côtière reste mal compris, de par la multiplicité des sources (apports directs(rivières/effluents) vs. apports diffus (friches industrielles côtières, aérosols, ...)) en partie contrôlée par le climat. Il en est de même des mécanismes de transfert des contaminants conditionnant leur devenir dans le milieu marin (flux nets vers le large). Dans ce contexte, différentes campagnes de prélèvements d’eau et de sédiments ont été mises en oeuvre sous des conditions climatiques contrastées (temps sec vs. pluie) dans les rivières ainsi qu'en mer, le long d’un transect allant de la côte à plus de 2 km au large des rejets. Les objectifs de cette étude visaient à déterminer les sources de contaminants au milieu côtier et à comprendre leurs mécanismes de transfert et leur devenir en mer. Par temps sec, les résultats obtenus ont montré que la dynamique du système est principalement contrôlée par les rejets de la STEP qui, par exemple, est responsable à plus de 75% des apports en Ag, Cu ou Pb au milieu côtier. Une fois en mer, les différents ETM analysés présentent un profil non conservatif, dû à un fractionnement dissous/particulaire hors équilibre dans les émissaires associé à un relargage rapide au début du gradient de salinité. Ces résultats ont été confirmés par une expérience de remobilisation réalisée au laboratoire permettant de mieux comprendre la cinétique de désorption des ETM. Dans ces conditions, il a été démontré qu'il était indispensable de filtrersur le terrain les échantillons pour ne pas sous-estimer la fraction dissoute des ETM. Par temps de pluie, le suivi des apports au cours d'une crue a montré la très grande réactivité du système, typique de rivières côtières. La majorité des ETM, transportés principalement sous forme particulaire, subissent une fois en mer des processus de désorption avec des cinétiques plus lentes et à des salinités plus importantes que par temps sec. Ces différences sont probablement liées à la nature des particules, urbaines et très organiques par temps sec, plutôt terrigène et inorganiques par temps de pluie. Enfin, une expérience de vitesse de chute des particules transitant dans le système par temps sec et de pluie a été développée au laboratoire. Elle a permis de caractériser les particules étudiées par des paramètres physico-chimiques intégrables au modèle hydro-sédimentaire de l'IFREMER, permettant de mieux évaluer le devenir des particules en zone côtière
The aim of this PhD was to evaluate the impact from Marseille agglomeration on thecoastal area, using trace metals and organic carbon quantification. On the French Mediterraneancoast, Marseille is the largest agglomeration (~1.7M inhabitants), located directly on coast andhave the biggest European underground wastewater treatment plan (WWTP, 1.62M eq). Theimpact of this urbanized and industrialized area on the coastal zone (bulk fluxes) remainsmisunderstood, because of the multiplicity of contaminant sources (direct inputs(rivers/effluents) vs. diffusive ones (coastal industrial wasteland, aerosols, …)) partlycontrolled by climatic conditions. Similarly, the transfer mechanisms of contaminants thatcontrol their fate to the open sea (net fluxes) have to be studied. In such context, numerouswater and sediment sampling campaigns were performed during contrasted climatic conditions(baseflow vs. flood) in the tributaries and along a 2km coastal-offshore transect in front of theoutputs. The main objectives of this study were to determine contaminants sources, transfermechanisms and fate in the coastal zone. During baseflow conditions, results have shown thatthe system dynamic is mainly controlled by the WWTP inputs, that are for instance the maincontributor (>75%) of Ag, Cu or Pb inputs to the coastal area. When discharged to the sea, thestudied trace metals presented non-conservative behaviours, consecutive to adissolved/particulate fractionation out of equilibrium in the outlets associated to fastremobilization at the beginning of the salinity gradient. These results were confirmed by labremobilization experiments allowing to better understand the desorption kinetics of tracemetals. Under such conditions, it was demonstrated that on-field filtration is a prerequisite toavoid under-estimation of the dissolved fraction of trace metals. The monitoring of a flood eventduring a rainy period has shown the high reactivity of the studied system, a peculiarity ofMediterraneean coastal rivers. Most of the studied trace metals, mainly brought in theparticulate fraction, suffer desorption processes when discharged to the sea, a processcharacterized by kinetics slower and effective at higher salinity in comparison to baseflowinputs. These differences are most probably linked to the nature of particles being urban andorganic during baseflow, mostly terrigeneous and inorganic during flood. Finally, a settling rateexperiment was designed in the lab in order to evaluate the physical and chemical characteristicsof representative particles. The obtained parameters were integrated in the 3D hydrodynamicand sediment transport model of IFREMER allowing to better evaluate the fate of pollutedparticles in the coastal area

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Libri sul tema "Contaminant transfers"

Dou, Zhi, Zhifang Zhou, Jinguo Wang e Yong Huang. Mass Transfer Dynamics of Contaminants in Fractured Media. Singapore: Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-99-9187-7.

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Napier, B. A. Transfer factors for contaminant uptake by fruit and nut trees. Washington, DC: United States Nuclear Regulatory Commission, Office of Nuclear Regulatory Research, 2014.

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United States. Environmental Protection Agency e United States. Office of Solid Waste, a cura di. Best management practices (bmps) for soil treatment technologies: Suggested operational guidelines to prevent cross-media transfer of contaminants during clean-up activities. [Washington, D.C.]: U.S. Environmental Protection Agency, Solid Waste and Emergency Response, [Office of Solid Waste, 1997.

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United States. Environmental Protection Agency. e United States. Office of Solid Waste., a cura di. Best management practices (bmps) for soil treatment technologies: Suggested operational guidelines to prevent cross-media transfer of contaminants during clean-up activities. [Washington, D.C.]: U.S. Environmental Protection Agency, Solid Waste and Emergency Response, [Office of Solid Waste, 1997.

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Lippmann, Morton, e Richard B. Schlesinger. Characterization of Contaminants and Environments. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780190688622.003.0002.

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This chapter describes the extensive scientific terminology needed to describe the various classes of chemical contaminants as they occur in environmental media (air, water, soil, etc.) and the structural aspects and dynamic mass and energy transfers within and among the atmosphere, hydrosphere, lithosphere, and biosphere. It also introduces: the characteristics of occupational environments; health effects attributable to occupational and environmental exposures; dose response relationships in populations; and how they are affected by anthropogenic (human activity caused) inputs and disruptions.

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Zhou, Zhifang. Mass Transfer Dynamics of Contaminants in Fractured Media. Springer, 2024.

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Reuber, Barbara Suzanne. A fugacity model of organic contaminant transfer at the sediment-water interface. 1987.

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Contaminants Transport in Soils: Principles and Applications. Taylor & Francis Group, 2014.

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Best management practices (bmps) for soil treatment technologies: Suggested operational guidelines to prevent cross-media transfer of contaminants during clean-up activities. [Washington, D.C.]: U.S. Environmental Protection Agency, Solid Waste and Emergency Response, [Office of Solid Waste, 1997.

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Stone, M. Series of Proceedings and Reports: the Role of Erosion and Sediment Transport in Nutrient and Contaminant Transfer: Proceedings of a Symposium Held at Waterloo, Ontario, July 2000 (IAHS Publication). IAHS Press, 2000.

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Capitoli di libri sul tema "Contaminant transfers"

Munholland, Jonah, Derek Rosso, Davinder Randhawa, Craig Divine e Andy Pennington. "Advances in Low-Temperature Thermal Remediation". In Advances in the Characterisation and Remediation of Sites Contaminated with Petroleum Hydrocarbons, 623–53. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-34447-3_18.

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AbstractRemediation through traditional high-temperature thermal techniques (over 100 °C) are designed to remove contaminants like petroleum hydrocarbons via enhanced mobilization and volatilization. However, remedies of this nature can require significant infrastructure, capital, operational and maintenance costs, along with high energy demands and carbon footprints. Conversely, low-temperature thermal approaches (in the mesophilic range of ~15–40 °C) are an inexpensive and more sustainable method that can enhance the physical, biological, and chemical processes to remove contaminants. Heat transfer properties of subsurface sediments and other geological materials do not vary considerably and are relatively independent of grain size, unlike hydraulic properties that can vary several orders of magnitude within a site and often limit the pace of remediation of many in-situ technologies. Therefore, low-temperature thermal remediation is a promising alternative that can remediate contaminant mass present in both high- and low-permeability settings, including fractured rock. Emergence of risk-based non-aqueous phase liquid management approaches and sustainable best management practices further offer a platform for low-temperature thermal remedies to advance petroleum hydrocarbon remediation with lower capital and operational costs. Case studies demonstrating this approach along with preliminary sustainability comparisons of the associated reduced energy use and carbon footprint are described in this chapter.

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Menefee, Dorothy S., e Ganga M. Hettiarachchi. "Contaminants in Urban Soils: Bioavailability and Transfer". In Urban Soils, 175–98. Boca Raton : Taylor & Francis, 2017. | Series: Advances in soil science: CRC Press, 2017. http://dx.doi.org/10.1201/9781315154251-8.

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Mackay, Donald, e Kathryn E. Clark. "Predicting the Environmental Partitioning of Organic Contaminants and their Transfer to Biota". In Organic Contaminants in the Environment, 159–88. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-009-4329-2_5.

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Wild, S. R., e K. C. Jones. "Organic Contaminants in Wastewaters and Sewage Sludges: Transfer to the Environment Following Disposal". In Organic Contaminants in the Environment, 133–58. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-009-4329-2_4.

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Toran, Laura. "Carbon Isotope Mass Transfer as Evidence for Contaminant Dilution". In ACS Symposium Series, 190–201. Washington, DC: American Chemical Society, 1990. http://dx.doi.org/10.1021/bk-1990-0416.ch014.

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Dou, Zhi, Zhifang Zhou, Jinguo Wang e Yong Huang. "Lattice Boltzmann Simulation of Solute Transport in Fractures". In Mass Transfer Dynamics of Contaminants in Fractured Media, 197–204. Singapore: Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-99-9187-7_11.

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Dou, Zhi, Zhifang Zhou, Jinguo Wang e Yong Huang. "Influence of Wettability on Interfacial Area for Immiscible Liquid Invasion". In Mass Transfer Dynamics of Contaminants in Fractured Media, 153–65. Singapore: Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-99-9187-7_8.

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Dou, Zhi, Zhifang Zhou, Jinguo Wang e Yong Huang. "Introduction". In Mass Transfer Dynamics of Contaminants in Fractured Media, 1–17. Singapore: Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-99-9187-7_1.

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Dou, Zhi, Zhifang Zhou, Jinguo Wang e Yong Huang. "Numerical Methods of Mass Transfer Process in Fractured Media". In Mass Transfer Dynamics of Contaminants in Fractured Media, 117–36. Singapore: Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-99-9187-7_6.

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Dou, Zhi, Zhifang Zhou, Jinguo Wang e Yong Huang. "Mathematical Model of Mass Transfer in Fractured Media". In Mass Transfer Dynamics of Contaminants in Fractured Media, 95–115. Singapore: Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-99-9187-7_5.

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Atti di convegni sul tema "Contaminant transfers"

Kasai, Paul H., e Vedantham Raman. "Hydrocarbon Transfer in Disk Drives". In ASME 2014 Conference on Information Storage and Processing Systems. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/isps2014-6903.

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In hard disk drives, oils used in the spindle motor or the actuator assembly are likely to be potential sources of hydrocarbon contaminants. Transfer to, and accumulation of such contaminants on the head would adversely affect its flyability. It was reported earlier that such transfer occurs more readily, the lower the vapor pressure of the contaminant is, and the lower the temperature of the ambiance is. The present study confirmed these findings. It is shown that the transfer is mediated by the disk surface area of high surface energy (openings of the carbon overcoat). Via an airflow transport process, droplets of the contaminant hydrocarbon are formed at such sites, and evolve in size till they are collected by the slider of the head.

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Musser, Amy, Wladyslaw Kowalski e William Bahnfleth. "Stack and Mechanical System Effects on Dispersion of Biological Agents in a Tall Building". In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-33862.

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Multizone network airflow analysis is used to analyze stack and mechanical system effects on the distribution of three representative biological agents in a prototype 40 story building. This approach relies on mass balances to compute airflow and contaminant transfer between the building zones. The analysis considers stack effects caused by cold outdoor temperatures, unintended positive and negative pressurization of the floor on which the release of the agent occurs, and three levels of contaminant removal using a combination filter/UVGI system. The results show that vertical shafts, such as stairwells and elevator shafts provide significant routes for contaminant transfer between floors, even when these floors are served by different air handling systems. Because the air moving through these pathways does not pass through an air handling system, this type of transport is not as easily reduced by filtering. However, commercially available filters were able to reduce contaminant concentrations substantially in zones that receive contaminants primarily due to recirculation through the air handling system.

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Karaismail, Ertan, Ismail Celik, Steven E. Guffey e William H. Dodrill. "Numerical and Experimental Investigations on Hood Capture and Protection Efficiencies". In ASME 2008 Fluids Engineering Division Summer Meeting collocated with the Heat Transfer, Energy Sustainability, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/fedsm2008-55277.

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Effective hoods are critical for the protection of workers from airborne contaminants. The aim of this study is to determine the effects of cross-draft and presence of a worker on the effectiveness of the bench-top enclosing hoods, which, unlike laboratory fume hoods have no sash and have a constant cross-sectional area. The computational fluid dynamics (CFD) software, FLUENT, with shear-stress transport (SST) k-ω turbulence model was used to investigate the effect of orientation of the manikin and hood with respect to cross-draft on the flow and contaminant concentration field. Experiments were conducted using a manikin and a fume hood in a wind tunnel and the flow around the manikin and inside the hood was investigated via particle image velocimetry (PIV) measurements. The correlation of contaminant leakage with the turbulent intensity and recirculating vortices at the hood face were observed. The hood and manikin orientation was found to change the exposure level significantly. Maximum contaminant leakage from the hood to the working environment has been found when the hood and manikin were placed 30 degrees to the cross draft. Maximum containment was observed when the manikin and hood were oriented in the same direction as the cross draft and perpendicular to the cross draft.

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Haupt, Sue Ellen, Robert F. Kunz, L. Joel Peltier, James J. Dreyer e Howard J. Gibeling. "Impact of Heat Transfer on Contaminant Dispersion in a Public Building". In ASME 2006 2nd Joint U.S.-European Fluids Engineering Summer Meeting Collocated With the 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/fedsm2006-98484.

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Computational fluid dynamics (CFD) models are effective at predicting dispersion of contaminants in or near a building. It is well known that thermal effects impact the flow around and within structures. This study assesses the importance of time of day, building materials, sky cover, etc. on the local thermal heating of a building. All these features affect the buoyancy, and thus, the resulting flow and dispersion about and inside a building. This study examines that impact through including full thermal coupling with flow calculations for an environmentally friendly building, including thermal radiation, conduction, and convection effects with a CFD model for both the interior and exterior of a building. The emphasis here is on simulating the impact of heating on contaminant dispersion.

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Butler, Emily C., Francesco P. Conto, Merlin A. Etzold, Stuart B. Dalziel, Joel Daou e Julien R. Landel. "DECONTAMINATION-INDUCED CONTAMINANT REDISTRIBUTION IN POROUS MEDIA". In International Heat Transfer Conference 17. Connecticut: Begellhouse, 2023. http://dx.doi.org/10.1615/ihtc17.370-70.

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Wood, B., D. Hall, J. Lesho, M. Boies, D. Silver, O. Uy, R. Benson et al. "MSX satellite - Flight measurements of contaminant films". In 7th AIAA/ASME Joint Thermophysics and Heat Transfer Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1998. http://dx.doi.org/10.2514/6.1998-2592.

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Soni, Sankalp, Bakhtier Farouk e Charles N. Haas. "Simulation of Contaminant Dispersal in an Apartment Building". In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56379.

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Bio-terrorism events (like the 2001 anthrax attacks) accentuate the importance of countering these incidents. In order to develop reliable countermeasures for these events, it is essential to understand the associated transport processes. The transport processes involved pose challenges as they occur over wide ranges of spatial and temporal scales. CONTAMW, a multi zone indoor air quality and ventilation analysis program is used to predict the contaminant dispersal in an apartment building. Detailed simulation results and analysis of controlled release of propylene within a generic apartment building is presented. A zonal analysis is carried out for the entire apartment building (using CONTAMW) to obtain time histories of propylene concentration in different zones. The simulations provide the dispersion, transport and contaminant concentration within each zone of the apartment. This study also considers the effect of flow obstructions and ventilation rates on contaminant dispersal. The results are validated with the experimental results reported in Cybyk et al. (1999). We have also simulated propylene transport in the apartment with FDS, a large eddy simulation model.

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Martynov, Pavel, e Oleg Matvienko. "Mathematical modeling of contaminant transfer in the atmosphere". In 28th International Symposium on Atmospheric and Ocean Optics: Atmospheric Physics, a cura di Oleg A. Romanovskii e Gennadii G. Matvienko. SPIE, 2022. http://dx.doi.org/10.1117/12.2644838.

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Brouwer,, D., R. Huijbers, H. Marquart e J. van Hemmen. "64. Transfer of Contaminants from Surfaces to Hands: Pressure as Determinant for Skin Adherence of a Sticky Contaminant during Repeated Hand-Press Contacts". In AIHce 2001. AIHA, 2001. http://dx.doi.org/10.3320/1.2765974.

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Lu, Yuanwei, Chongfang Ma, Wencai Li, Jianping Sheng e Wei Wang. "The Study of Photocatalytic Degradation of Formaldehyde Under the Action of Mass Transfer". In 2007 First International Conference on Integration and Commercialization of Micro and Nanosystems. ASMEDC, 2007. http://dx.doi.org/10.1115/mnc2007-21025.

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Photocatalysis is an emerging and promising technology for indoor air purification, which has the higher reaction rate at the higher pollutant concentration and vice versa, and the toxic intermediate products were produced meantime. However, the concentration of indoor pollutant is usually very low. So how to improve the photocatalytic reaction rates in indoor contaminant levels in building and to eliminate the intermediate toxic products are the keys of commercialization of this technology. This paper immobilized the TiO2 on the active carbon and analyzed the effect of mass transfer due to the absorption of AC on the photocatalytic reaction rate. The experimental results shown that the photocatalytic reaction rate was improved for the local concentration of contaminants on the surface photocatalyst TiO2 was enhanced by adsorbent activated carbon. With the increase of air stream velocity, the photocatalytic reaction switched from mass transfer control process to photocatalytic reaction control process. The switch point was advanced for the absorption of AC comparing with TiO2 immobilized on the surface of glass. The indoor formaldehyde with low level concentration can be decomposed to the range of indoor air quality standards by the TiO2/AC filter.

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Rapporti di organizzazioni sul tema "Contaminant transfers"

Napier, Bruce, Robert Fellows e Leah Minc. Transfer Factors for Contaminant Uptake by Fruit and Nut Trees. Office of Scientific and Technical Information (OSTI), novembre 2013. http://dx.doi.org/10.2172/1149245.

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Korte, N. E., C. A. Muhr e D. W. Greene. Potential soil contaminant levels of polychlorinated dibenzodioxins and dibenzofurans at industrial facilities employing heat transfer operations. Office of Scientific and Technical Information (OSTI), aprile 1992. http://dx.doi.org/10.2172/10140743.

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Wilkins, Justin, Andrew McQueen, Joshua LeMonte e Burton Suedel. Initial survey of microplastics in bottom sediments from United States waterways. Engineer Research and Development Center (U.S.), settembre 2021. http://dx.doi.org/10.21079/11681/42021.

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Given the reported extent of microplastics in the aquatic environment, environmentally relevant exposure information for sediments dredged by the US Army Corps of Engineers will lend context to the risks posed by this contaminant during dredging. We measured the occurrence, abundance, and polymer composition of microplastics in sediments collected from nine dredged waterways and two non-dredged reference areas. The number of particles in sediment samples ranged from 162 to 6110 particles/kg dry wt., with a mean of 1636 particles/kg dry wt. Fragments were the most prevalent shape observed among the 11 study sites (100% frequency of occurrence), followed by fibers (81%), spheres (75%), foams (38%) and films (34%). Based on analyses of chemical composition of the particles using Fourier transform infrared spectroscopy, polyethylene:propylene was the most common polymer type observed. Consistent with results presented by other investigators microplastic concentrations and polymer types in bottom sediments in this study were also aligned with the most widely used plastics worldwide.

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Butman, Cheryl A., e Robert A. Wheatcroft. Transfer of Contaminants between the Water Column and Bottom Sediments: The Role of Deposit-and Suspension-Feeding Benthic Invertebrates. Fort Belvoir, VA: Defense Technical Information Center, dicembre 1998. http://dx.doi.org/10.21236/ada360866.

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Butman, Cheryl A., e Robert A. Wheatcroft. Transfer of Contaminants Between the Water Column and Bottom Sediments: The Role of Deposit- and Suspension-feeding Benthic Invertebrates. Fort Belvoir, VA: Defense Technical Information Center, settembre 1997. http://dx.doi.org/10.21236/ada628697.

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Kopte, Robert. OSADCP Toolbox. GEOMAR, 2024. http://dx.doi.org/10.3289/sw_2_2024.

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Vessel-mounted Acoustic Doppler Current Profilers (ADCPs) provide velocity profiles of the upper ocean along the ship track. They are a key tool in oceanographic research to study the oceanic circulation and the associated distribution of mass, heat, contaminants and other tracers. In order to obtain high-quality ocean current data from vessel-mounted ADCP measurements, a number of requirements must be met, from system installation and data acquisition measures to certain essential processing steps. Here, we collect key points on ADCP data acquisition in general and on the characteristics and requirements of vessel-mounted deployments. We summarize general post-processing guidelines and present an open-source Python toolbox called OSADCP for scientists to convert, clean, calibrate and organize binary raw vessel-mounted ADCP data for scientific use. The toolbox is designed to process ADCP measurements in deep water by Teledyne RDI Ocean Surveyor ADCPs and the data acquisition software VMDAS. An extended version of OSADCP is continuously developed as part of a data management project for the German oceanographic research fleet. The corresponding workflow was designed to ensure a standardized and reliable ADCP data transfer from the sensor to the repository. It is described here as one example for scientific data management that follows FAIR data guidelines.

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