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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.
21

Traffic-Related Metals in Soil and Sediment in Mauritius / Trafikrelaterade metaller i jord och sediment på Mauritius

Petersson, Liselott January 2005 (has links)
Trafik utgör en stor föroreningskälla av tungmetaller i vägnära jordar och särskilt är det koppar (Cu), bly (Pb) och zink (Zn) som associeras med fordonstrafik. I ett historiskt perspektiv härrör blyutsläpp främst från bränsleförbränning, medan kopparemissioner (i första hand från slitage av bromsbelägg) och zinkutsläpp (från däck) från trafik står för så mycket som hälften av det urbana utsläppet av koppar och zink till omgivningen. Koppar-, bly- och zinkkoncentrationer i vägnära jord och sediment undersöktes inom avrinningsområdet för Grand River North West i Mauritius. Eftersom totalmetall utgör en dålig indikator på den mängd metall som finns potentiellt tillgänglig för biota användes extraktion med hjälp av 0.5 M HCl tillsammans med totalkoncentrationer. Den rumsliga variationen längsmed transekt vinkelrätt mot vägar undersöktes liksom variationen med djupet. Observerade kopparkoncentrationer var jämförbara med bakgrundsnivåer. Till skillnad från Cu var koncentrationer av Pb och Zn förhöjda i den omedelbara närheten till vägar med relativt stor trafikintensitet, men halterna minskade snabbt med avståndet. Resultat från platserna för jordreferenser visar på storskalig förorening av Pb på ön. Uppmätta kopparkoncentrationer kunde inte knytas till trafikens påverkan. Vid regn kan metaller som finns i förorenat vägdamm och förorenad jord övergå till löslig form, eller sköljas bort i partikulär form, och transporteras till närliggande vattendrag. I Mauritius är det här av speciell vikt eftersom flodsediment till slut kommer att deponeras i de känsliga kustområdena som omger ön. Dock tyder inte resultaten på förhöjda metallhalter i sediment nära de studerade vägarna. Även om erhållna resultat av Cu inte visar på någon förhöjning och zonen med hög förorening av Pb och Zn är relativt smal, är det angeläget att följa utvecklingen eftersom antalet fordon växer snabbt i Mauritius, vilket kan förändra dagens situation och ge upphov till större miljöpåverkan. För att undvika eventuella ekologiska skador är det därför av stor vikt att i fortsättningen övervaka situationen längs landets vägar. / Traffic has been identified as a significant heavy metal polluter of roadside soils, and copper (Cu), lead (Pb) and zinc (Zn) in particular are associated with road travel. In a historic perspective, the Pb contribution from anthropogenic sources to nature has predominantly been a result of fuel combustion. There are indications that Cu (mainly through braking system) and Zn (emissions from tires) released from traffic give rise to as much as half of the total urban contribution of copper and zinc to the environment. Concentrations of Cu, Pb and Zn in roadside soils and sediment have been determined at selected roads within the Grand River North West watershed in Mauritius. As total metal concentrations are not a suitable indicator of the metal concentrations that are potentially available to biota, metals extractable in 0.5 M HCl have been determined along with total concentrations. The spatial variation in metal concentration along soil transects perpendicular to roads were investigated, as was the variation with depth. Observed Pb and Zn concentrations exhibited elevated levels in topsoil in the immediate vicinity of roads with relatively large traffic densities, but the decrease in concentration with distance was rapid. Results from soil reference sites pointed to a large scale Pb pollution on the island. In comparison, observed Cu concentrations could not be assigned any influence from traffic at the selected study sites. In the event of rain, metals contained in polluted road dust and soil may be released into soluble form, or flushed from roadways as particulate matter, and transported to nearby water courses. In Mauritius, this is of particular importance as sediment in rivers eventually may be deposited in the sensitive coastal areas of the island. However, results do not indicate that there were any elevated levels of heavy metals in sediment close to roads that were investigated in this study. Although Cu concentrations in roadside soils did not show any enrichment and the zone of elevated Pb and Zn concentrations was not wide, there is a concern that the continuing rapid increase in the number of vehicles in Mauritius will change the situation, possibly resulting in greater impact on the surrounding environment. Hence, in order to avoid any ecological damage, it is desirable to continue monitoring the situation along highways in the country.
22

Ecological Risk Assessment of Heavy Metal Content in the Hatillo River, Costa Rica

Pham, Vivian G 01 January 2015 (has links)
Rivers all around the world have become increasingly polluted with heavy metals, largely due to industrialization and urbanization. Organisms exposed to high concentrations of heavy metals have shown evidence of biotoxicity and physical deformities. With biomagnification in mind, the possibility that this contamination may soon directly affect humans is a real concern, and policies in manufacturing industries worldwide may have to be reformed. In this study, we measured the concentrations of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), and lead (Pb) in the Hatillo River and compared these values to those measured in the Tarcoles River, a highly polluted river, and Terciopelo Creek, a relatively clean river. The results showed that the Hatillo River had significantly lower levels of most detected heavy metals than both the Tarcoles and Terciopelo. Overall, sediments in all rivers showed high levels of heavy metal content--especially in chromium, copper, nickel, and lead--which could build up and affect organisms over a long period of time.
23

Undersökning av miljöpåverkan från järnsand i en sedimentstudie i Inre-viken, Skellefteå / Using sedimentary records to investigate iron sand’s environmental impact in Inre-viken, Skellefteå (English)

Rikard, Haldebo January 2015 (has links)
With rapidly urbanizing societies, waste management needs attention. In 2008, EUs Waste Framework Directive (WFD) set new concepts, like reducing usage of natural materials. Thus, the interest for alternative materials increased. In Skellefteå, since the 1970’s, iron sand has often substituted natural gravel in road construction. But, today stricter regulations might forbid iron sand for further use. The issue is whether leachate from iron sand causes heavy metal pollution or not. This thesis tried to provide more knowledge into iron sand’s environmental impact. In order to investigate this, a sediment sample (<53 cm deep) collected in Inre-viken, a lake 50m from a road with iron sand, were analyzed for Zn, Pb and Cu concentrations. Enrichment factor (EF), national benchmarks, and reference data were used to evaluate anthropogenic impact and age-determine the sediment. The results showed: (1) Inre-viken has elevated heavy metal levels compared to pre-industrial levels, with highest Cu (133 mg/kg) and Zn(204 mg/kg) concentrations found in the surface layer. (2) Zn and Cu showed an increase between 41-0 cm depth (1970-2015), but only Cu reaches high concentrations, while Zn and Pb range between low to very low concentrations. (3) The metal enrichment is low compared to the reference lake. The findings show that there are elevated levels in Inre-viken compared to pre-industrial levels. However, identifying the main source of pollution is difficult, because many pollution sources exist in the area. To determine if iron sand is the culprit, further studies are necessary.
24

Mobilization of metals from mining wastes and the resuspension of contaminated sediments

Thuy Nguyen, Lan January 2008 (has links)
In some environmental situations, environmental effects caused by elevated metals resulting from past mining and smelting activities can be observed in nearby receiving water bodies several decades after mine and smelter closure. There is a growing need for managing the hazardous solid wastes such as mining wastes as well as for assessing water quality and for sustainable management of sediment quality. The work presented in this thesis examined the mobilization of metals from two metal sources: mining wastes from a mine site in Vietnam and sediments from a contaminated lake in Sweden in order to test the hypothesis that mobilization of metals will be increased, when the environmental conditions change by e.g. exposure of mining wastes to oxidative weathering, change of redox conditions at the water-sediment interface and resuspension of sediments. The results from this work under field and laboratory conditions have verified the hypothesis. The exposure of sulphidic mining wastes in oxidative weathering conditions may cause long-term production of ARD and the resultant long-term mobility of metals. The oxidation/resuspension of sediments is an important factor for the release of trace metals Zn, Cu and Cd into the solution and substantial amounts of particles and, hence, associated metals into overlying water. The concomitant changes in pH during oxidation/resuspension of sediment play a significant role in the metal release both to redox sensitive elements Fe and Mn and trace elements Zn, Cu and Cd. The concomitant change in DOC during oxidation/resuspension can also contribute to the increased mobility of study metals. The field study was coupled to intermittent operation of a hydropower plant. The mobility of the metals was higher under operation compared to non-operation and, thus, the potential impacts on dispersal of metal pollution to downstream aquatic environments. The sudden increase in water flow upon the hydropower plant upon shifts from inactive to active state could cause immediate release of particles and thus particulate metals in the overlying water. However, the magnitude and its integrated effects in fluxes of metals over the season call for further research. There is a need to further investigate the impacts of hydropower generation in a longer period of time and at a higher frequency of observations at the very start of the hydropower operation. The results from this multidisciplinary approach would give a basis for an optimal operation of the hydropower plant to minimize the metal pollution associated with the water flow. / <p>The series number is changed from 410 to 430 and the ISBN is changed from 978-91-85895-56-4 to 978-91-7393-926-3.</p>
25

Challenges and opportunities of urban food production : a case study from Victoria, British Columbia

McLeod, Heather 09 September 2011 (has links)
Food production in urban areas has been conducted worldwide as a subsistence strategy and source of income. Recently, however, it is recognized that urban agriculture has the potential to contribute to the development of sustainable urban environments. This study examines the benefits of urban food production in North American cities, as well as focusing on some of the critical barriers to its widespread expansion and acceptance. It also explores the potential for contamination of produce from the ambient atmosphere in mid-sized urban centres. Through interviewing nine urban farmers and one urban planner, in the city of Victoria, British Columbia, I documented each producer’s knowledge of the benefits and limitations associated with urban food production. Each interviewee impressed upon me the numerous benefits that can be accrued through the practice of urban agriculture, but they also painted a picture of the struggles that urban farmers face. Issues identified included: a real and perceived risk of contamination, problems with land ownership and access, and lack of meaningful support for urban farmers. Although urban agriculture has been accepted in principle by the City of Victoria and other Canadian cities, there are many challenges that must be overcome for urban food production to truly produce a viable, sustained food system. A coordinated, comprehensive government policy for involvement in the urban food system is critical to effectively addressing urban food issues. Investigations of heavy metal levels in lettuce (Lactuca sativa) grown in sampling sites across an urban/rural gradient showed that atmospheric contamination by heavy metals is greatest at urban sites, but also affects residential and rural sites. Sampling site types included: a control area (rural farms and properties outside of Victoria); residential sites (yards in residential neighbourhoods in the City of Victoria); and, industrial/business sites (heavily trafficked and industrialized areas in downtown Victoria). Site types were intended to reflect areas perceived as safe, probably safe, and probably not safe, and were selected based on expert opinion and land use. Results indicate that caution should be exercised in growing leafy greens at downtown sites, and that growing food in most residential neighbourhoods and green spaces is typically no worse than growing greens in rural Victoria. In fact, due to the proximity of urban agriculture to the market, growing food locally eliminates the need for transportation and extra processing; reducing the extra exposure crops otherwise might face during these phases. Urban food production requires the support of communities and governments in order to contribute to both urban food security and urban sustainability. The City of Victoria has started on a path to ensuring that this food system receives the required support, but it requires concerted effort and action. Further research into urban food systems is necessary to ensure that urban food production is able to become a viable, sustained food system. / Graduate
26

Biomarkers of Cadmium, Lead and Selenium Toxicity in the Marine Bivalve Molluscs Tellina deltoidalis and Anadara trapezia: Linking Exposure, Dose and Response

Taylor, Anne Marie, n/a January 2009 (has links)
The relationships between metal exposure, dose and response were investigated in two sediment dwelling marine bivalves: a deposit feeder Tellina deltoidalis and a filter feeder Anadara trapezia. The bivalves were exposed in the laboratory to individual metal spiked sediments: Cadmium 10 and 50 Ag/g; lead 100 and 300 Ag/g; selenium 5 and 20 Ag/g dry mass, T. deltoidalis for 28 days A. trapezia for 56 days. A. trapezia was also exposed in the laboratory for 56 days to sediments from three sites along a metal contamination gradient of cadmium, lead, selenium, zinc and copper from Lake Macquarie, NSW. Metal total tissue dose was measured in whole tissue of T. deltoidalis over 28 days and in gill, hepatopancreas and haemolymph tissues in A. trapezia over 56 days. Subcellular metal distribution, biologically active metal (BAM) versus biologically detoxified metal (BDM) was measured in whole tissues of T. deltoidalis at day 28 and in gill and hepatopancreas tissues of A. trapezia at day 56. Biomarkers of response measured in spiked sediment exposed, at day 28 T. deltoidalis and day 56 A. trapezia were: total antioxidant capacity (TAOC); glutathione peroxidase enzyme activity (GPx); total glutathione concentration (GSH+2GSSG); reduced to oxidised glutathione ratio (GSH:GSSG); lipid peroxidation (TBARS); lysosomal membrane stability and micronuclei frequency. Response indices measured in A. trapezia exposed to Lake Macquarie sediments were: TAOC, TBARS, lysosomal membrane stability, micronucleus frequency and condition index. Native A. trapezia and sediments were also collected from Lake Macquarie and measured for sediment and tissue metal concentrations, TAOC, TBARS, lysosomal membrane stability and condition index to allow comparison between chronically exposed and previously unexposed organisms. T. deltoidalis and A. trapezia accumulated metal over time in all sediment metal exposures with most reaching equilibrium tissue metal concentrations by the end of the exposure period. T. deltoidalis generally reached equilibrium with the exposure concentration for cadmium and lead but had significantly higher selenium tissue concentrations than the sediment metal at the 5 Ag/g exposure. A. trapezia tissue lead was below the sediment concentration for all exposures including in the native organisms. A high proportion of accumulated lead and copper in A. trapezia was in the haemolymph, probably associated with haemoglobin which has a high affinity for these metals`. A. trapezia cadmium tissue concentrations were higher than the sediment metal in the 10 Ag/g spiked sediment exposure and between half and one eighth the sediment concentrations in other treatments, including in native organisms. A. trapezia including the native organisms exposed to selenium sediment concentrations at or below 5 Ag/g in the Lake Macquarie mixed metal sediments accumulated significantly higher than ambient selenium tissue concentrations while those exposed to 5 and 20 Ag/g selenium spiked sediments had lower than ambient selenium tissue concentrations. The majority of accumulated cadmium, selenium and zinc was associated with the gill/mantle tissues. A. trapezia hepatopancreas contributed significant selenium concentrations in the later part of the exposure period indicating and increased contribution from dietary derived selenium. Native A. trapezia had significantly lower tissue concentrations of selenium, copper and zinc, higher cadmium and approximately equal lead compared to organisms exposed to similar sediment metal concentrations in the laboratory. T. deltoidalis detoxified around 50 % of accumulated cadmium and 70 % of lead while A. trapezia detoxified around 70 % of accumulated cadmium and 60 % of lead. Much of T. deltoidalis BDM cadmium was converted to metal rich granules (MRG), while A. trapezia had most in the metallothionein like proteins (MTLP) fraction. The conversion of lead to MRG was 75 % of the total BDM in T. deltoidalis while A. trapezia had an even distribution between MRG and MTLP. The majority of recovered selenium in both species was associated with the nuclei+cellular debris fraction, probably as protein bound selenium associated with plasma and selenium bound directly to cell walls. Selenium exposed organisms had increased BDM selenium burdens which were associated with both MRG and MTLP fractions, indicating selenium detoxification. The majority of BAM cadmium, lead and selenium was associated with the mitochondrial fraction in both species with increases in cadmium burden in this organelle of T. deltoidalis up to 7200 fold; lead 154 fold; and selenium 7 fold and in A. trapezia up to 84 fold cadmium, 50 fold lead and selenium 7 fold in exposed organisms compared to controls. The subcellular distribution of all three metals in T. deltoidalis and A. trapezia indicates active metal detoxification processes which at these exposure concentrations were unable to prevent significant metal burdens from accumulating in sensitive organelles. A contamination gradient of zinc, lead, copper, cadmium and selenium was established in Lake Macquarie sediments which emanated from the same source. A. trapezia accumulated all metals in each sediment exposure. Accumulation and tissue distribution patterns of cadmium, lead and selenium were similar to those of the single metal spiked sediment exposures. Cadmium and lead BAM burdens increased at all exposures while selenium, zinc and copper did not. T. deltoidalis and A. trapezia in the spiked sediment metal exposures generally had reduced GPx activity. This resulted in an increase in total glutathione concentrations which the reduced GSH:GSSG ratios indicated was due to a build up of oxidised glutathione. T. deltoidalis and A. trapezia had reduced TAOC in all laboratory sediment metal exposures which corresponded with increased TBARS concentrations, lysosomal destabilisation and micronucleus frequency. A. trapezia exposed to Lake Macquarie metal contaminated sediments also had a reduction in physiological condition, indicated by the reduced condition index, after 56 days at the higher metal exposures. Clear exposure - dose - response relationships have been demonstrated for T. deltoidalis and A. trapezia exposed to single cadmium, lead and selenium spiked sediments and for A. trapezia exposed to Lake Macquarie mixed metal contaminated sediments. Detoxification of all metals was evident in both T. deltoidalis and A. trapezia but detoxification capacity was exceeded for cadmium, lead and selenium leading to significant accumulation of these metals in sensitive organelles. The significant relationships, in the laboratory exposed T. deltoidalis and A. trapezia, between TAOC reduction with increased TBARS, lysosomal destabilisation and micronuclei frequency and between increased TBARS with lysosomal destabilisation and micronuclei frequency indicates that increased tissue metal dose and BAM burdens caused significant impairment of the antioxidant reduction capacity which resulted in a cascade of effects from lipid peroxidation to cellular perturbation and genotoxic damage. The reduction in physiological condition in the organisms with the highest tissue metal doses suggests the response goes beyond subcellular perturbations to whole organism and potentially population effects. Chronically metal exposed native Lake Macquarie A. trapezia did not show a clear metal exposure - dose - response relationship. Accumulation of the essential elements zinc, copper and selenium appeared to be regulated while cadmium and lead were not. TAOC was significantly reduced and TBARS significantly increased compared to reference organisms but lysosomal stability and condition were not significantly affected. The suite of interrelated biomarkers used offers a weight of evidence approach for demonstrating adverse effects of metal tissue accumulation in T. deltoidalis and A. trapezia
27

Mucorales de solo contaminado com metais pesados na região do pólo cerâmico de Santa Gertrudes, SP: ocorrência e capacidade de biossorção de chumbo e zinco

Souza, José Ivanildo de [UNESP] 05 December 2006 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:32:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-12-05Bitstream added on 2014-06-13T18:44:34Z : No. of bitstreams: 1 souza_ji_dr_rcla.pdf: 1254068 bytes, checksum: 64378d1c217e577afa6ca9eebcf6200f (MD5) / Em solo contaminado com metais pesados na região do pólo cerâmico do município de Santa Gertrudes, Estado de São Paulo, Brasil, foi realizado o levantamento taxonômico de fungos da ordem Mucorales (Zygomycota) utilizando-se o método da placa-de-solo, modificado pela aplicação de uma suspensão de solo (10%, p v-1) sobre malte agar (2%, p v-1) acrescido de Pb(NO3)2 ou Zn(NO3)2 nas concentrações de 0 (controle), 100, 200, 500 e 1000 mg L-1. As identificações e descrições taxonômicas foram realizadas utilizando-se SMA (synthetic Mucor agar), sendo obtidos os táxons: Absidia cylindrospora v. cylindrospora Hesselt. & Ellis, Cunninghamella phaeospora Boedijn, Mucor circinelloides Tiegh. f. circinelloides, M. circinelloides Tiegh. f. lusitanicus (Bruderl.) Schipper, M. circinelloides Tiegh. f. janssenii (Lendn.) Schipper, Mucor hiemalis Wehmer f. hiemalis, M. hiemalis Wehmer f. luteus (Linnem.) Schipper, Mucor racemosus Fresen. f. racemosus, Rhizopus oryzae Went & Prins. Geerl., Zygorrhynchus moelleri Vuill. e Mucor bainieri Mehrotra & Baijal, que é citado pela primeira vez para o Brasil. Análises químicas de amostras de solo coletadas em quatro locais na área estudada confirmaram a contaminação severa por metais pesados em alguns dos locais, sendo que comparações entre o número de táxons obtidos no presente estudo com os dados de literatura permitiram concluir que houve prejuízo à diversidade de fungos na região. As biomassas secas e pulverizadas (2 g L-1) de Mucor hiemalis f. hiemalis (SPC 2040) e de Mucor hiemalis f. luteus (SPC 2044) foram colocadas em contato, sob agitação a 120 rpm por 14 h, com soluções aquosas (pH 4) de Pb(NO3)2 e Zn(NO3)2 nas concentrações de 0,06, 0,13 e 0,17 mM e de 0,08, 0,16 e 0,23 mM, respectivamente, sendo comparadas ao carvão ativado (CA), utilizado como material adsorvente de referência. / In a heavy metal contaminated soil at ceramic pole of Santa Gertrudes region, São Paulo State, Brazil, a taxonomic survey of fungi of the order Mucorales (Zygomycota) have been done using the soil plate method, modified for a soil suspension (10%, p v-1) application on malt agar (2%, p v-1) added with Pb(NO3)2 or Zn(NO3)2 at 0 (control), 100, 200, 500 and 1000 mg L-1 concentrations. Taxonomic identifications and descriptions have been done with SMA (synthetic Mucor agar), obtaining the taxa: Absidia cylindrospora v. cylindrospora Hesselt. & Ellis, Cunninghamella phaeospora Boedijn, Mucor circinelloides Tiegh. f. circinelloides, M. circinelloides Tiegh. f. lusitanicus (Bruderl.) Schipper, M. circinelloides Tiegh. f. janssenii (Lendn.) Schipper, Mucor hiemalis Wehmer f. hiemalis, M. hiemalis Wehmer f. luteus (Linnem.) Schipper, Mucor racemosus Fresen. f. racemosus, Rhizopus oryzae Went & Prins. Geerl., Zygorrhynchus moelleri Vuill. and Mucor bainieri Mehrotra & Baijal, that is cited first time for Brazil. Chemical analyses of soil samples taken from four sites in the studied area confirm a severe contamination of heavy metals in some of the sites, and comparisons between taxa numbers obtained in the present study with literature data allowed conclude that there was fungal diversity disturbance in the region. The dry and grounded biomasses (2 g L-1) of Mucor hiemalis f. hiemalis (SPC 2040) and Mucor hiemalis f. luteus (SPC 2044) was kept in contact, under agitation at 120 rpm during 14 h, with aqueous solutions (pH 4) of Pb(NO3)2 and Zn(NO3)2 at 0.06, 0.13, 0.17 mM and 0.08, 0.16, 0.23 mM concentrations, respectively, being compared with activated charcoal (AC) as the reference adsorbent. The percentages amounts of metals removed from solutions, express by q% index, had presented the following adsorption sequences: AC > SPC 2044 > SPC 2040 for Pb and AC > SPC 2040 > SPC 2044 for Zn.
28

Ficedula hypoleuca hemoglobin levels in lead contaminated areas. : Is bird health affected by invertebrate community composition and abundance?

Berggren, Andreas January 2018 (has links)
Mining is a widespread industrial activity that in many cases, via mining wastes, leads to altered concentrations of metals in close vicinity to the mining activities. Metals in mining waste can have high toxicity and may persist in environments for long time periods. The presence of metals, such as lead (Pb), is known to contaminate and cause damage to nearby organisms and ecosystems. Birds are at risk of metal contamination and, since they are predators high up in the food chain, may face accumulation of metal in tissue over time, via consumption of contaminated prey. Small passerine species, such as the pied flycatcher (Ficedula hypoleuca), are suitable for studying metal contamination as they are ubiqutious, and high up in the food chain. Pied flycatchers feed exclusively on invertebrates, making the abundance, quality, and potential contamination of invertebrates interesting to study with regard to the health of the birds. Studies have shown that hemoglobin (Hb) levels in young pied flycatchers are reduced by high background levels of Pb.  This may be linked to prey availability and quality, as invertebrates are known to alter their composition, and contain higher Pb concentrations in Pb contaminated areas. Here, I investigated how invertebrate abundance and community composition, and pied flycatcher Hb concentrations (i.e. health), in reference and Pb contaminated areas, were related to each other. Invertebrate traps were set and sampled twice during the summer of 2018 to provide invertebrate data to the study. Bird Hb levels was acquired by taking blood samples from nearly fledged chicks in birdhouses placed in the different areas. I found a potential trend towards higher Hb levels in reference areas (p=0.110), suggesting that bird health is reduced by the presence of Pb, but this could not be explained by differences in invertebrate community composition or abundance (p&gt;0.05). Hence, based on this study, high Pb concentrations in the soil does not directly, or indirectly via potential impacts on the prey community composition, influence the health of pied flycatchers.
29

Chemistry, Detection, and Control of Metals during Silicon Processing

Hurd, Trace Q. 05 1900 (has links)
This dissertation focuses on the chemistry, detection, and control of metals and metal contaminants during manufacturing of integrated circuits (ICs) on silicon wafers. Chapter 1 begins with an overview of IC manufacturing, including discussion of the common aqueous cleaning solutions, metallization processes, and analytical techniques that will be investigated in subsequent chapters. Chapter 2 covers initial investigations into the chemistry of the SC2 clean - a mixture of HCl, H2O2, and DI water - especially on the behavior of H2O2 in this solution and the impact of HCl concentration on metal removal from particle addition to silicon oxide surfaces. Chapter 3 includes a more generalized investigation of the chemistry of metal ions in solution and how they react with the silicon oxide surfaces they are brought into contact with, concluding with illumination of the fundamental chemical principles that govern their behavior. Chapter 4 shows how metal contaminants behave on silicon wafers when subjected to the high temperature (≥ 800 °C) thermal cycles that are encountered in IC manufacturing. It demonstrates that knowledge of some fundamental thermodynamic properties of the metals allow accurate prediction of what will happen to a metal during these processes. Chapter 5 covers a very different but related aspect of metal contamination control, which is the effectiveness of metal diffusion barriers (e.g. Ru) in holding a metal of interest, (e.g. Cu), where it is wanted while preventing it from migrating to places where it is not wanted on the silicon wafer. Chapter 6 concludes with an overview of the general chemical principles that have been found to govern the behavior of metals during IC manufacturing processes.
30

Evaluation of the levels of selected trace metal pollutants in groundwater and soil from protected springs in peri-urban Kampala, Uganda.

Moulodi, Shler, Thorsell, Jessica January 2013 (has links)
The current urban infrastructure and demographic development of Uganda and in particular of Kampala city is rapid and does not correspond to the planned socio-economic and industrial infrastructure. This project was justified by the existence of numerous peri-urban areas with unplanned and no monitored san-itary as well as water supply systems. The unsanitary handling and disposal, of domestic and industrial solid waste, sewerage and small car related industries pose a serious threat to the quality of the groundwater resources. Field studies were conducted at different occasions between February and March 2012. These included soil and water sampling in and around five protected springs for analysis of the concentrations of four trace metals: Cu, Pb, Cd and Zn. The method used for leaching tests of the soil samples was the European Standard ISO/TS21268-1, and the samples produced were analyzed in a ICP-MS. Addi-tionally, metal concentrations and dissolved organic content of water samples were analyzed. The ICP-MS results showed that the concentration of the trace metals in the waters were below guideline values stated by the WHO, which implies that the residents are not exposed to notable trace metal contamination in the drinking water. As the total metal content in the soils were below the Swedish Environmental Protection Agency (Swedish EPA) guidelines, it was assumed that trace metal contamination was not of significance under the pre-vailing circumstances. However, the leachable metal contents in a number of the soils were high, which may pose a future risk to groundwaters.

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