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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
451

The effects of farm management practices on cadmium concentration in wheat grain

Oliver, Danielle P. (Danielle Peta) January 1994 (has links) (PDF)
Bibliography: leaves 202-223.
452

Les élements présents a l'état de traces et les Hydrocarbures Aromatiques Polycycliques dans la neige et la glace prélevées au Col Gnifetti, massif du Mont Rose (4450m): implications environnementales et climatiques

Gabrieli, Jacopo 28 November 2008 (has links) (PDF)
Nous avons conçu, construit et testé un nouveau système pour la décontamination en ligne et l'analyse en continu de carottes de neige ou de glace des Alpes. L'eau de fusion obtenue à partir de la partie centrale des carottes est directement introduite dans un spectromètre de masse à quadrupole (ICP-QMS) et un conductimètre, pour la détermination en continu de différents éléments présents à l'état de traces et de la conductivité. Des échantillons sont également prélevés en discontinu pour la détermination de divers éléments présents à l'état de traces, des isotopes du Plomb et du Plutonium par spectrométrie de masse à secteur magnétique (ICP-SFMS) et par ICP-OES. L'eau de fusion obtenue à partir de la partie externe des carottes est quant à elle utilisée pour la détermination en semi-continu des Hydrocarbures Aromatiques Polycycliques (HAPs), avec extraction en ligne à l'aide de cartouches en phase solide.<br />D'importantes variations saisonnières des concentrations sont observées pour tous les éléments, aussi bien les éléments qui proviennent de manière prédominante de la croûte terrestre (Mg, Al) que les éléments enrichis par suite d'apports anthropiques (Pb). Pour comprendre ces variations à court terme, il est important de se référer aux rétro-trajectoires des masses d'air. D'autres paramètres importants sont la dynamique des inversions de températures et les caractéristiques de la couche limite. Ils jouent en effet un rôle majeur dans le transport et la dispersion des aérosols et des gaz à partir des sources d'émissions situées à basse altitude.<br />Les émissions les plus importantes de Plomb au cours de l'histoire ont eu lieu pendant les 19e et 20e siècles, et plus particulièrement des années 1950 aux années 1970. Pour déterminer si les variations observées dans la carotte du Colle Gnifetti reflètent fidèlement les variations des émissions dans les pays européens voisins, nous avons comparé les données obtenues pour la neige et la glace avec les données d'émission disponibles. De 1800 jusqu'à la première décennie du 20e siècle, les concentrations de Plomb ont augmenté de manière très marquée, atteignant un maximum dans les années 1920. Pendant les années 1920, les concentrations de Plomb décroissent rapidement d'un facteur deux, et restent à ce niveau pendant les deux décennies suivantes. Après la fin de la 2e guerre mondiale, les flux de retombées de Plomb augmentent de manière très importante par suite de l'utilisation des additifs au Plomb dans l'essence, et atteignent un maximum au milieu des années 1970. A partir de 1975, les concentrations de Plomb mesurées dans la neige et la glace du Colle Gnifetti commencent à décroître par suite des règlementations adoptées en Europe pour limiter les émissions de polluants.<br />Avant 1875, les concentrations de HAP étaient très basses: les concentrations observées dans la glace datant d'avant les années 1750 représentent très probablement le niveau de bruit de fond de ces composés. Les concentrations cumulées des HAP au cours de la décennie 1945-1955 sont supérieures d'un facteur dix aux valeurs de bruit de fond, alors que les concentrations cumulées de HAP* sont environ 40 à 50 fois plus élevées. A partir des années 1900, les concentrations de HAP augmentent de façon très importante, atteignant un maximum vers 1920. Pendant les années 1920, après la première guerre mondiale, la récession économique en Europe conduit à une chute des activités industrielles. A partir du milieu des années 1930, les concentrations de HAP doublent rapidement, atteignant un maximum pendant les années 1940. La concentration cumulée des HAP* les plus lourds décroit ensuite d'un facteur cinq de 1950 à 1975 alors que la concentration cumulée des HAP décroit d'un facteur deux. De 1975 à 2003, la concentration totale des HAP augmente à nouveau, approchant les valeurs des années 1910. De manière globale, les variations temporelles observées pour les HAP sont fortement corrélées aux variations des émissions anthropiques. Cependant, les variations détaillées sont difficiles à interpréter et pourraient être influencées par divers paramètres.<br />Le Plutonium est présent dans l'environnement par suite des essais nucléaires atmosphériques des années 1960, de la production des armes nucléaires et des rejets par l'industrie nucléaire au cours des 50 dernières années. Le profil de variations du Plutonium dans la neige et la glace du Colle Gnifetti met en évidence les trois périodes principales d'essais nucléaires atmosphériques.<br />Le rapport isotopique 206Pb/207Pb est compris entre 1.18 et 1.20 pour la glace datant d'avant 1700, en accord avec la composition des roches locale. Bien que les retombées de Plomb au Colle Gnifetti après les années 1900 soient presque entièrement dues à des apports anthropiques, on n'observe pas de variations importantes du rapport isotopique jusqu'en 1975. Ceci est lié au fait que la composition isotopique moyenne du Plomb dans l'essence et le pétrole utilisés était très semblable à la composition isotopique des roches et des sols locaux. Après 1975, on observe une décroissance brutale et forte du rapport isotopique 206Pb/207Pb, jusqu'à des valeurs proches de 1.11 en 1979-1980. Cette décroissance brutale est liée à une expérience réalisée entre 1975 et 1980 dans la région du Piémont au Nord-Ouest de l'Italie (Isotopic Lead Experiment).
453

A Study of the Environmental Conditions in Lake Nakuru, Kenya, Using Isotope Dating and Heavy Metal Analysis of Sediments

Svengren, Henrik January 2002 (has links)
No description available.
454

Riskbedömning vid Saltvikens kopparverk

Hellqvist, Daniel January 2009 (has links)
<h1>Abstract</h1><p>At Saltvikens copperindustry, which is located in the municipality of Oskarshamn, copper was refined from sulphiteore some hundred years ago. The ore underwent several steps in the process before the final product was received. These steps all had an influence on the environment through discharge of heavy metals. The area where the copper industry was located is today considered to be of specific national interest due to its valuable nature and cultural values, as well as its value for recreational outdoor activities. Therefore, it is important to determine the present level of contamination and if any transport of contaminants have occurred, and to identify the risks that are associated with the site both at present and in a longer time perspective.</p><p>Thirtynine soil samples and 16 sediment samples have been analyzed. All samples have undergone two different leaching procedures before the analyis; one with nitric acid for determination of total concentration and one with acidic acid to analyze the plant available part. The analysis was perfomed through Atomicabsorptionsspectrofotometry. In addition, pH and loss on ignition have been measured on all samples. The chemical values were then compared to reference values in order to establish the level of contamination. Within the risk assessment framework where then also a exposure modelling conducted. This was made both for an average exposure situation, and for a reasonable maximum exposure. For both these scenarios, one calculation was made based on the soil use of today and one was made based on an assumed future usage of the area for establishment of residential buildings.</p><p>The results show that both the land area and sediment have been affected by the copper industry. From 48 sediment samples, 46 generated concentrations above the assumed effect level levels given by the Swedish Environmental Protection Agency. The results also indicated that a significant contaminant transport has occurred, and is still occurring. This is supported by high metal concentrations in deep soil layers and by high concentrations in the sediment. The condition is considered to be very much serious in the case of copper and zinc and serious to less serious for lead, depending on the ground use. Some of the metals are very easy to leach and can thus contaminate adjacent areas for a long time.</p><p>Already at the present ground use, there is a risk for children to become exposed to  zinc and lead in doses that can generate negative health effects. At the potential future ground use the TDI for both copper, zinc and lead will be exceeded if a child is exposed. For adults, however, the TDI value for zinc and lead is exceeded only in the scenario with the potential future ground use.</p>
455

Predictive Modelling of Heavy Metals in Urban Lakes

Lindström, Martin January 2000 (has links)
<p>Heavy metals are well-known environmental pollutants. In this thesis predictive models for heavy metals in urban lakes are discussed and new models presented. The base of predictive modelling is empirical data from field investigations of many ecosystems covering a wide range of ecosystem characteristics. Predictive models focus on the variabilities among lakes and processes controlling the major metal fluxes. </p><p>Sediment and water data for this study were collected from ten small lakes in the Stockholm area, the Eastern parts of Lake Mälaren, the innermost areas of the Stockholm archipelago and from literature studies. By correlating calculated metal loads to the land use of the catchment areas (describing urban and natural land use), the influences of the local urban status on the metal load could be evaluated. Copper was most influenced by the urban status and less by the regional background. The opposite pattern was shown for cadmium, nickel and zinc (and mercury). Lead and chromium were in-between these groups. </p><p>It was shown that the metal load from the City of Stockholm is considerable. There is a 5-fold increase in sediment deposition of cadmium, copper, mercury and lead in the central areas of Stockholm compared to surrounding areas. </p><p>The results also include a model for the lake characteristic concentration of suspended particulate matter (SPM), and new methods for empirical model testing. The results indicate that the traditional distribution (or partition) coefficient K<sub>d</sub> (L kg<sup>-1</sup>) is unsuitable to use in modelling of the particle association of metals. Instead the particulate fraction, PF (-), defined as the ratio of the particulate associated concentration to the total concentration, is recommended. K<sub>d</sub> is affected by spurious correlations due to the definition of K<sub>d</sub> as a ratio including SPM and also secondary spurious correlations with many variables correlated to SPM. It was also shown that K<sub>d</sub> has a larger inherent within-system variability than PF. This is important in modelling. </p>
456

Predictive Modelling of Heavy Metals in Urban Lakes

Lindström, Martin January 2000 (has links)
Heavy metals are well-known environmental pollutants. In this thesis predictive models for heavy metals in urban lakes are discussed and new models presented. The base of predictive modelling is empirical data from field investigations of many ecosystems covering a wide range of ecosystem characteristics. Predictive models focus on the variabilities among lakes and processes controlling the major metal fluxes. Sediment and water data for this study were collected from ten small lakes in the Stockholm area, the Eastern parts of Lake Mälaren, the innermost areas of the Stockholm archipelago and from literature studies. By correlating calculated metal loads to the land use of the catchment areas (describing urban and natural land use), the influences of the local urban status on the metal load could be evaluated. Copper was most influenced by the urban status and less by the regional background. The opposite pattern was shown for cadmium, nickel and zinc (and mercury). Lead and chromium were in-between these groups. It was shown that the metal load from the City of Stockholm is considerable. There is a 5-fold increase in sediment deposition of cadmium, copper, mercury and lead in the central areas of Stockholm compared to surrounding areas. The results also include a model for the lake characteristic concentration of suspended particulate matter (SPM), and new methods for empirical model testing. The results indicate that the traditional distribution (or partition) coefficient Kd (L kg-1) is unsuitable to use in modelling of the particle association of metals. Instead the particulate fraction, PF (-), defined as the ratio of the particulate associated concentration to the total concentration, is recommended. Kd is affected by spurious correlations due to the definition of Kd as a ratio including SPM and also secondary spurious correlations with many variables correlated to SPM. It was also shown that Kd has a larger inherent within-system variability than PF. This is important in modelling.
457

Road traffic metals : sources and emissions

Hjortenkrans, David January 2008 (has links)
As the environmental regulations and technical progress have forced the factories’ old “end of pipe” solutions to improve, the metal emissions from point sources have decreased. Instead, the diffuse consumption emissions from goods in use now are in focus. The increased awareness of traffic as a major diffuse metal emission source emphasizes the need for more detailed information on the various traffic related sources. The main scope of this thesis is to study specific parts of metal emissions from some road traffic related sub sources such as brake lining and tyres. The metals in focus are antimony (Sb), cadmium (Cd), copper (Cu), chromium (Cr), lead (Pb), nickel(Ni) and zinc (Zn), and the research quantifies emissions from the different sub sources, trace changes over time as well as dispersal patterns and metal mobility in the roadside environment. The results show that even if the road traffic associated metal stocks are small compared to total in use stocks, their emissions are of major importance. The updated figures show that despite material developments during the last 10 years, tyres still are one of the main sources of Zn and Cd, while it can be excluded as a source of concern for the other metals studied. Brake linings are shown to be an especially pronounced source for Cu and Sb. The Pb and Cd emissions from brake linings and tyres have decreased as a result of decreasing material concentrations in these sources, most likely a result of EU regulations. Further the results reveals galvanized goods to be a major road traffic related source for Zn. The results show that the total metal concentrations in roadside soils have increased 3-16 times compared to regional background during the last decades. Each metal has a limited dispersal distance from the roads as well as down in the soil profile. Most metals are found within 10 m from the road in the uppermost 10 cm of the topsoil. However, the sequential extractions show that a large part of the metals found in the soil are rather easily mobilized and can be redistributed if the roadside soils become disturbed. Metals emitted due to decelerating activities are not correlated to elevated concentrations near road junctions. Instead the metals appear to be more evenly spread along the whole driven distance. The study points out Sb as an element that might be problematic to analyse. For Sb, which is sparsely studied as a roadside contaminant, there is a need of more general knowledge as it has a high accumulation rate in roadside soils. / I takt med ökade regleringar inom miljöområdet och en snabb teknikutveckling har fabrikerna allt mer spelat ut sin roll som emissionskällor till miljön. Istället har den diffusa emissionen som kommer från produktanvändning fått en större betydelse. En ökad medvetenhet om transporter och trafikens betydelse för samhällets konsumtionsemissioner understryker det ökade kunskapsbehovet för de trafikrelaterade emissionskällorna. Avhandlingens huvudsyfte är att studera specifika delar av metallemissionen från vissa trafikrelaterade källor så som bromsbelägg och däck. Metallerna som är i fokus är antimon (Sb), bly (Pb), kadmium (Cd), koppar (Cu), krom (Cr), nickel (Ni) och zink (Zn) och forskningen strävar efter att kvantifiera emissionerna från de olika källorna, spåra förändringar i emissioner över tid, kartlägga utsläppsmönster och metallrörlighet i vägnära jord. Resultaten pekar på att även om de trafikrelaterade källorna kvantitativt är små i jämförelse med de totala källorna så är deras emissioner av stor betydelse. De nya siffrorna visar att trots en materialutveckling inom området under det senaste årtiondet så är fortfarande däck en av de största källorna för Cd och Zn i stadsmiljö, medan de kan avfärdas som källa för de övriga studerade metallerna. Studien visar att bromsbelägg fortfarande är en viktig källa för Cu och Sb. Bly- och Cd-emissionerna från däck och bromsbelägg har däremot minskat drastiskt under samma period. Denna minskning beror troligen på en reglering på EU-nivå. Dessutom visar resultaten att galvaniserade ytor är den viktigaste källan till Zn i stadsmiljö. Metallkoncentrationerna i vägnära jord har ökat med 3 – 16 ggr jämfört med bakgrundshalterna i de undersökta områdena. Metallerna uppvisar endast en begränsad spridning från vägen och ner i jordprofilen. Den största metallpåverkan återfinns inom 10 m från vägen och i de översta 10 cm av jorden. Trots den begränsade spridningen så uppvisar de flesta metallerna en förhållandevis hög rörlighet, vilket innebär att de kan bli mobila vid störning av jorden. De bromsrelaterade metallerna uppvisar ingen korrelation till förhöjda halter nära korsningar utan är mer jämnt spridda över hela körsträckan. Studien pekar ut Sb som ett element som kan vara problematiskt att analysera på grund av dess flyktighet. Trots att Sb för närvarande har en snabb ackumulationstakt i trafikmiljö så är den endast sparsamt studerad. Mer generell kunskap om Sb är därför önskvärd.
458

On-site wastewater treatment : Polonite and other filter materials for removal of metals, nitrogen and phosphorus

Renman, Agnieszka January 2008 (has links)
Bed filters using reactive materials are an emerging technology for on-site wastewater treatment. Chemical reactions transfer contaminants from the aqueous to the solid phase. Phosphorus is removed from domestic wastewater by sorption to filter materials, which can then be recycled to agriculture as fertilisers and soil amendments. This thesis presents long-term column and field-scale studies of nine filter materials, particularly the novel product Polonite®. Phosphorus, nitro-gen and metals were removed by the mineral-based materials to varying degrees. Polonite and Nordkalk Filtra P demonstrated the largest phosphorus removal capacity, maintaining a PO4-P removal efficiency of &gt;95%. Analysis of filter bed layers in columns with downward wastewater flow, showed that phosphorus, carbon and nitrogen content was vertically distributed, with de-creasing values from surface to base layer. Polonite and Filtra P accumulated 1.9-19 g P kg-1. Nitrogen in wastewater was scarcely removed by the alkaline filter materials, but transformation from NH4-N to NO3-N was &gt;90%. Pot experiments with barley (Hordeum vulgare L.) revealed that after wastewater treatment, slags and Polonite could increase plant production. Batch experi-ments and ATR-FTIR investigations indicated that amorphous tricalcium phosphate (ATCP) was formed in the materials, so some of the accumulated PO4-P was readily available to plants. Low heavy metal contents occurred in the materials, showing that they can be applied as soil amend-ments in agriculture without contamination risks. A full-scale treatment system using Polonite as filter material showed an average PO4-P removal efficiency of 89% for a 92-week period, indicat-ing the robustness of the filter bed technology. / QC 20100907
459

Long term heavy metal contamination from leakage water sediments

Brodd, Patrick January 2004 (has links)
No description available.
460

XRF-analys av förorenad mark : undersökning av felkällor och lämplig provbearbetning / XRF-analysis of contaminated soil : a study of error sources and suitable sample preparation

Kjellin, Johan January 2004 (has links)
X-ray fluorescence (XRF) detection of heavy metals is a cost- and time-effective method for investigation of polluted areas. Compared to laboratory analysis, XRF analysis is limited by high detection limits and uncertainties in some situations. Preparation of samples is known to affect the results of measurements. The purpose of this thesis is to bring a deeper understanding of how different factors affect the results of XRF-analysis. A large number of measurements have been made with the instruments Niton XLt 700 and Niton Xli 700. Results from measurements of lead, zinc and copper have been analysed. This study has shown that a greater moisture content will give a lower measured concentration for the same sample. If the moisture content is known, it is possible to make good approximations of concentrations in dry samples. No obvious differences were found between different metals. Proper homogenisation of samples was found to be one of the most critical issues. It should be noted that laboratories do not usually homogenise samples prior to analysis, so samples sent for laboratory verification should therefore be homogenised before sending. Sample preparation, including drying, sieving to finer grain-sizes and analysing in a special sample cup was found to increase the measured concentrations and decrease the variation between measurements. The concentrations differed with different sample matrices and with sample preparation. Because of the differences, measurements should always be correlated with laboratory analysis before any conclusions can be made. In situations when metals are well within detection range of the XRF instrument, the only preparation needed is in most cases homogenisation. If metal levels are just at the limit, or just below the detection limit, further preparations of samples should be made. When drying samples makes detection possible, more preparation is usually not worth the effort. If detection limits still are a problem after drying, the samples should be sieved and analysed in sample cups. In situations where concentrations still are below the detection limit when analysing in sample cups, or if the measurements are disturbed for other reasons, another method than XRF-analysis must be used. When XRF analysis is possible, the method is preferable compared to only laboratory analysis. This cost- and time effective method makes a larger number of measurements possible, and gives a more complete overview of a polluted area. / Analys med röntgenfluorescensdetektor (XRF) är en snabb och kostnadseffektiv fältmetod för detektion av tungmetaller i mark. Nackdelen är att mätningarna inte är tillförlitliga i alla sammanhang och att detektionsgränsen för många ämnen är förhållandevis hög. Det är sedan tidigare känt att olika former av provbearbetning påverkar mätresultaten. I detta examensarbete har undersökts hur olika faktorer påverkar mätresultaten vid analys av jordprover med XRF instrument. Faktorerna som undersökts är inverkan av vattenkvot, kornstorlek, provpåsar och olika provbearbetningsmetoder. Vid provbearbetningsförsöken skickades prover även in till externt laboratorium för jämförande analys. Metaller som undersökts är bly, zink och koppar. Vid undersökningen konstaterades att en ökad vattenkvot ger upphov till lägre mätvärden. Vid kännedom om vattenkvot kan halt per torrsubstans med god överensstämmelse uppskattas utifrån mätningar på fuktiga prov. Är precisionskraven stora och vattenkvoten varierande och okänd bör dock proverna torkas innan mätningar görs. Ingen avsevärd skillnad sågs mellan de olika metaller som undersöktes. Vid undersökningen om provbearbetningens betydelse visade det sig att homogeniseringen av proverna är mycket viktig, inte minst av prover som skickas till laboratorieanalys. Ökad provbearbetning med torkning och siktning till mindre kornstorlek tenderar att ge högre mätvärden med XRF instrument. Storleksmässigt är mätvärden vid obearbetade prov mest överensstämmande med laboratorieanalys. Mest skiljer sig analys på finsiktade prover i provkopp. Korrelationsmässigt finns i en del fall en tendens till bättre överensstämmelse med mer bearbetade prov. Den största vinsten med ökad bearbetning av prover konstaterades i detta arbete vara att mark med lägre metallkoncentrationer då kan analyseras. I de fall där halterna av metaller ligger väl inom XRF instrumentets detektionsområde visade det sig att det oftast är tillräckligt att endast homogenisera proverna innan analys görs. I de fall där koncentrationen av metaller är på gränsen till vad XRF instrumentet kan detektera rekommenderas att proverna torkas, eller om nödvändigt torkas, siktas och analyseras i provkopp. Där nivåerna av metaller ligger under detektionsgränsen för XRF instrument trots provbearbetning, eller där andra ämnen till exempel järn stör mätningarna, måste en annan analysmetod väljas.

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