• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 59
  • 3
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 72
  • 72
  • 72
  • 18
  • 12
  • 10
  • 10
  • 9
  • 9
  • 8
  • 7
  • 7
  • 6
  • 6
  • 6
  • 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.
61

Phosphorus and iron loading to Lake Ontario from waste water treatment plants in Hamilton and Toronto /

Medeiros, Andrew. January 2005 (has links)
Thesis (M.A.)--York University, 2005. Graduate Programme in Environmental Studies. / Typescript. Includes bibliographical references (leaves 96-100). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url%5Fver=Z39.88-2004&res%5Fdat=xri:pqdiss &rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR11861
62

Analysis for certain selected trace inorganic ions in York-Prairie Creek Pond

Mapetla, Shadrack K. January 1980 (has links)
As a result of rapid growth in technology, efforts to remove pollutants from the natural environment have not been able to keep pace with the increasing amount of waste materials and a growing population that further aggravates the situation. This has resulted in the transformation of lakes and ponds into pollution depots. A pilot study for monitoring certain selected trace elements entering and leaving YorkPrairie Creek Pond, situated inside the campus of Ball State University, was undertaken with the view to establishing whether or not this pond has been polluted, like many lakes and ponds, by metal corrosion, engine exhaust gases, and runoff from fertilizers and streets.This investigation involved sampling pond waters at two sites, viz., Influx surface and Effluent surface. Samples were collected once daily at the same time over a total time period of 23 days. Each sample was analyzed, in duplicate, for the heavy metal cations iron, lead, and cadmium, and for the inorganic anions nitrate, orthophosphate, and chloride. Metals were analyzed by atomic absorption spectrophotometry (A. A. S.), while titrimetric and cotorimetric procedures were utilized for the anion analyses.Results have indicated that iron and chloride are the most abundant of all analytes. Precipitation tends to Increase concentrations of analytes in general, possibly due to increased runoff and the lowering of the pH of these waters; leading to increased elemental release into solution. The relative responses of the analyzed ion levels in pond influx and effluent waters have been shown to be similar although their levels were significantly different.Analyte levels were found to be generally higher in effluent than in Influx waters; only chloride was found to depart from this general behavior. This finding led to the conclusion that the selected Ions, with the exception of chloride, tend not to accumulate in the waters of the pond but rather to escape with its effluent. This conclusion is subject to modification by future researchers, to whom the author has recommended a more expanded sampling program that would include the surface and sediment of the pond's interior since the nature of the results (especially for Pb and Cd) would seem to indicate not only that the pond does not exhibit thorough mixing of its constituents (homogeneity) but also the presence of an active remobilization process within its interior.
63

Assessment of trace element contamination in streambed sediment and spatial associations in Palolo Valley watershed, Honolulu, Oʻahu, Hawaiʻi

Hotton, Veronica K January 2005 (has links)
Thesis (M.A.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaves 146-156). / Also available by subscription via World Wide Web / xxi, 156 leaves, bound ill., maps 29 cm
64

Antimony and acetaldehyde migration from Nigerian and British PET bottles into water and soft drinks under typical use conditions : concentration of migrants and some trace elements in polyethylene terephthalate and in bottled contents

Tukur, Aminu January 2011 (has links)
Also aged bottles are safer to use than new bottles because their chemical leaching was found to be lower than that of new bottles. This study recommends the reassessment of the absence of international guidelines for acetaldehyde in water and foods. The study also recommends that the amount of acetaldehyde that can be added to soft drinks as flavouring agent should be below the specific migration limit (SML) for migration of acetaldehyde from PET bottle into bottle contents. This is essential since the SML was designed to ensure that exposure to acetaldehyde, as a result of intake of bottled water and soft drinks in PET bottles, is below the tolerable daily intake (TDI) for acetaldehyde. As antimony was reported to go beyond the safe limits in some Nigerian bottled water and soft drinks after 11 months of storage this study discourages the use of bottle contents stored for a very long time.
65

Trace organics pollution in the aquatic environment

Wong, Wang-wah., 黃宏華. January 1993 (has links)
published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management
66

Internal cycling in an urban drinking water reservoir /

Raftis, Robyn R. January 2007 (has links)
Thesis (M.S.)--Indiana University, 2007. / Department of Earth Sciences, Indiana University-Purdue University Indianapolis (IUPUI). Advisor(s): Gabriel M. Filippelli, Catherine Souch, Lenore P. Tedesco. Includes vitae. Includes bibliographical references (leaves 80-83).
67

Avaliação da contaminação de Poecilia reticulata e Hypostomus ancistroides por elementos-traço na Bacia do Ribeirão Cafezal (Município de Rolândia - PR) / Contamination evaluation of Poecilia reticulata and Hypostomus ancistroides for trace elements in Ribeirão Basin Cafezal (City of Rolândia - PR)

Balestri, Máira Renata Dias 08 September 2015 (has links)
A qualidade da água é um fator importante para o bem-estar do ser humano, e equilíbrio dos ecossistemas naturais. Com o aumento populacional e a consequente industrialização, se intensificou a produção de esgoto doméstico e de efluentes industriais, os quais podem conter metais e acentuar a poluição ambiental. Alguns elementos-traço são considerados essenciais para o desenvolvimento e manutenção dos organismos, porém, se forem ingeridos em concentrações acima das recomendadas, podem ser tóxicos. O objetivo desse estudo foi avaliar o grau de contaminação de duas espécies de peixes (Poecilia reticulata e Hypostomus ancistroides) abundantes do Ribeirão Cafezal (Rolândia - PR) pelos elementos Zn, Cd, Cr e Pb. A coleta dos peixes foi realizada em três pontos ao longo do trecho superior da bacia do Ribeirão Cafezal, utilizando os métodos de pesca elétrica e manual, com esforço amostral de 40 min para cada método. Para a detecção dos elementos traço no material coletado, as amostras foram devidamente preparadas para emprego da técnica de Espectrometria de Emissão Óptica por Plasma Indutivamente Acoplado (ICP-OES). As concentrações apresentadas pelos indivíduos da espécie Poecilia reticulata (pontos 1 e 2) amostrados do ribeirão foram: Zn (107,63; 91,89 mg/kg) , Cd (0,12; 0,42 mg/kg), Cr (2,17; 4,96 mg/kg) e Pb (0,71; 0,44 mg/kg); enquanto que para a espécie Hypostomus ancistroides (pontos 2 e 3) foram: Zn (93,11; 76,97 mg/kg), Cd (2,22; 0,10 mg/kg), Cr (16,05; 2,23 mg/kg) e Pb (2,83; não determinado mg/kg). Todos os valores estão acima dos limites permitidos pela ANVISA (Agência Nacional de Vigilância Sanitária). Não houve diferenças significativas nas concentrações dos metais entre os pontos de amostragem avaliados. Como se trata de um Ribeirão onde as pessoas utilizam a água para recreação e se alimentam dos peixes que colonizam o local, é preciso continuar a atividade de monitoramento, bem como realizar análises sistemáticas com diferentes espécies de peixes, água e sedimento. / Some trace elements are considered essential for the development and maintenance of living organisms. However, if those trace elements are ingested in higher concentrations than recommended can be toxic. The aim of this study was to evaluate the degree of contamination for two abundant species of fish from Ribeirão Cafezal (Poecilia reticulata and Hypostomus ancistroides) with Zn, Cd, Cr and Pb elements. The fish collection was performed at three points along the upper stretch of the basin of Ribeirão Cafezal using electric and manual fishing methods, with sampling effort of 40 minutes for each method. In order to detect the trace elements in the collected material, the samples were properly prepared to the Inductively Coupled Plasma by Atomic Emission Spectroscopy (ICP-OES). The concentrations presented by the species Poecilia reticulata in the two first points of the stream were: Zn (107.63; 91.89 mg / kg), Cd (0.12, 0.42 mg / kg), Cr (2.17; 4.96 mg / kg) and Pb (0.71, 0.44 mg / kg), sampled in 1 and 2 respectively. And individuals of Hypostomus ancistroides species sampled in points 2 and 3 had the following values: Zn (93.11; 76.97 mg / kg), Cd (2.22, 0.10 mg / kg), Cr (16.05; 2.23 mg / kg) and Pb (2.83; nd mg / kg). All values are higher than the limits allowed by ANVISA. There were no significant differences in the metals concentrations among the sampling points assessed. In consideration for Ribeirão Cafezal being a stream where people use water for recreation and feed on the existing fish, we need to continue monitoring it, as well as performing systematic analysis with different species of fish, sediment and water.
68

Toxicity of urban stormwater runoff

Anderson, Bruce Campbell January 1982 (has links)
This work involves the study of the effects of land use on the chemical composition of urban stormwater runoff, and its subsequent acute toxicity to the aquatic invertebrate Daphnia pulex. Samples were obtained from the Brunette drainage basin of Burnaby, British Columbia, from a variety of sites in the land use classifications commercial (C), industrial (I), residential (R) and open/greenspace (0). Results indicate that the toxicity to D. pulex and the chemical composition of the stormwater (measured by such parameters as COD, alkalinity, hardness, hydrocarbons and trace metals) were influenced by land use and the interval between rainfall events. The industrial and commercial land use sites were the major source of those trace metals most often considered toxic to aquatic organisms, with runoff from the commercial sites proving most toxic to the test organism (toxicity followed the sequence C>I>R»0). Bioassays with synthetic stormwater (Cu, Fe, Pb and Zn, at concentrations observed from field samples) demonstrated that pH and suspended solids helped to regulate the toxicity of the trace metals, and implicated the importance of these elements in natural stormwater toxicity. Statistical comparison between synthetic and natural stormwater runoff toxicity yielded poor correlation; however, this was expected due to the inherent differences between the laboratory and field environments. A detailed study of a single storm event indicated that while the "first-flush" of the storm may be contributing to toxicity through the physical scouring of insoluble pollutants, the soluble pollutants proved to be more toxic and were washed out of the area over the entire duration of the event. This prompted the author to propose the complete treatment of all stormwater runoff, and not simply the slug load of the first hour. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate
69

Heavy metals in the overlying water and bottom sediments of Shing Mun River and inner Tolo Harbour.

January 1996 (has links)
Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 113-120). / Abstract --- p.i / Acknowledgement --- p.iii / Table of Contents --- p.iv / List of Tables --- p.viii / List of Figures --- p.xii / Chapter CHAPTER 1. --- INTRODUCTION --- p.1 / Chapter 1.1 --- Previous Heavy Metal Studies of Hong Kong Marine Waters and Sediments --- p.4 / Chapter 1.2 --- Speciation of Metals in Aquatic Environment --- p.6 / Chapter 1.2.1 --- Speciation of Metals in Water --- p.7 / Chapter 1.2.2 --- Speciation of Metals in Bottom Sediments --- p.7 / Chapter 1.3 --- AVS in Marine Sediments --- p.10 / Chapter 1.3.1 --- Formation of AVS --- p.10 / Chapter 1.3.2 --- Seasonal and Spatial Variation of AVS --- p.11 / Chapter 1.3.3 --- AVS as Mediator of Metal Toxicity --- p.13 / Chapter 1.3.4 --- Chemical Basis for AVS Sediment Normalization --- p.15 / Chapter 1.3.5 --- Analysis of Pore Water Metals --- p.17 / Chapter 1.4 --- Significance of the Research --- p.18 / Chapter 1.4.1 --- Importance of Metal Bioavailability Study in Hong Kong --- p.18 / Chapter 1.4.2 --- Importance of AVS Study in Hong Kong --- p.19 / Chapter 1.4.3 --- Approach of the Present Study --- p.21 / Chapter 1.5 --- Organization of the Thesis --- p.22 / Chapter CHAPTER 2. --- METHODOLOGY --- p.23 / Chapter 2.1 --- Study Area --- p.24 / Chapter 2.2 --- Sampling Strategy --- p.25 / Chapter 2.2.1 --- Sampling Locations --- p.25 / Chapter 2.2.2 --- Sampling Dates --- p.28 / Chapter 2.2.3 --- Sample Collection and Handling --- p.28 / Chapter 2.3 --- Sample Analysis --- p.32 / Chapter 2.3.1 --- Sediment Analysis --- p.32 / Chapter 2.3.2 --- Pore Water and Overlying Water Analysis --- p.34 / Chapter 2.3.3 --- Limitations --- p.36 / Chapter 2.4 --- Statistical Analysis --- p.39 / Chapter CHAPTER 3. --- METALS IN WATER AND BOTTOM SEDIMENTS --- p.40 / Chapter 3.1 --- Metals in the Water --- p.40 / Chapter 3.1.1 --- Variation of Metal Concentrations --- p.41 / Chapter 3.1.2 --- Metal Pollution Level of the Overlying Water --- p.42 / Chapter 3.2 --- Metals in Bottom Sediments --- p.44 / Chapter 3.2.1 --- Spatial Distribution Pattern of Heavy Metals --- p.44 / Chapter 3.2.2 --- Temporal Variation of Metal Content in the Bottom Sediments --- p.48 / Chapter 3.2.3 --- Metal Pollution Level of the Bottom Sediments --- p.49 / Chapter 3.3 --- Conclusion --- p.50 / Chapter CHAPTER 4. --- SPECIATION OF METALS IN THE OVERLYING WATER AND BOTTOM SEDIMENTS --- p.51 / Chapter 4.1 --- Speciation of Metals in the Overlying Water --- p.51 / Chapter 4.1.1 --- Concentration of Labile Metals in the Overlying Water --- p.52 / Chapter 4.1.2 --- Seasonal and Spatial Variation in the Concentration of Labile Metals in the Overlying Water --- p.54 / Chapter 4.1.3 --- Percentage of Labile Fraction in Total Metals --- p.55 / Chapter 4.2 --- Speciation of Metals in the Bottom Sediments --- p.59 / Chapter 4.2.1 --- Proportion of Various Metal Species in the Sediments --- p.60 / Chapter 4.2.2 --- Variation of the Overlying Water Properties --- p.63 / Chapter 4.2.2.1 --- Chemical Properties of the Water in the Study Area --- p.63 / Chapter 4.2.2.2 --- Seasonal Variation of Water Properties --- p.67 / Chapter 4.2.2.3 --- Stratification of the Water Column --- p.69 / Chapter 4.2.3 --- Implication of the Changes of Water Quality on Metal Remobilization --- p.73 / Chapter CHAPTER 5. --- VARIATION OF AVS AND ITS ROLE IN METAL TOXICITY MEDIATION --- p.77 / Chapter 5.1 --- Variation of AVS in the Study Area --- p.78 / Chapter 5.1.1 --- Spatial Variation of AVS --- p.78 / Chapter 5.1.2 --- Seasonal Variation of AVS --- p.81 / Chapter 5.1.3 --- Vertical Variation of AVS --- p.85 / Chapter 5.1.4 --- Effects of AVS Variation on Metal Bioavailability --- p.88 / Chapter 5.2 --- Role of AVS in Metal Toxicity Mediation --- p.91 / Chapter 5.2.1 --- SEM/AVS Molar Ratio --- p.91 / Chapter 5.2.2 --- Fraction of SEM in Total Metals of the Sediments --- p.94 / Chapter 5.2.3 --- Labile Metals in Pore Water --- p.96 / Chapter 5.2.4 --- Dissolved Sulfides in the Pore Water and Overlying Water --- p.99 / Chapter 5.3 --- Conclusion --- p.100 / Chapter CHAPTER 6. --- CONCLUSION --- p.102 / Chapter 6.1 --- Introduction --- p.102 / Chapter 6.2 --- Major Findings --- p.103 / Chapter 6.3 --- Practical Implication of the Findings --- p.108 / Chapter 6.4 --- Suggestion for Further Studies --- p.110 / Bibliography --- p.113 / Appendix A. AVS Extraction and Detection Method --- p.121 / Appendix B. Sequential Extraction Method for Metals Speciation Analysis --- p.123 / Appendix C. Instrument List for the Experiments --- p.125 / Appendix D. Monthly Total Rainfall and Mean Temperature of1995 --- p.127 / Appendix E. Analytical Results of the Overlying Water --- p.128 / Appendix F. Analytical Results of the Bottom Sediments --- p.132 / Appendix G. Analytical Results of the Pore Water --- p.136 / Appendix H. Concentration (μg/g) and Fraction (%) of Pbin Sediments --- p.140 / Appendix I. Concentration (μg/g) and Fraction (%) of Cuin Sediments --- p.142 / Appendix J. Concentration (μg/g) and Fraction (%) of Cdin Sediments --- p.144 / Appendix K. Concentration (μg/g) and Fraction (%) of Znin Sediments --- p.146 / Appendix L. Concentration (μg/g) and Fraction (%) of Niin Sediments --- p.148 / Appendix M. Fraction of Different Speciations of Metals in the Sediments --- p.150 / Appendix N. Vertical Profile of Dissolved Oxygen in the Overlying Water --- p.155 / Appendix O. Vertical Profile of Salinity in the Overlying Water --- p.159 / Appendix P. Vertical Profile of Temperature in the Overlying Water --- p.163 / Appendix Q. Vertical Profile of pH in the Overlying Water --- p.167
70

Internal Cycling in an Urban Drinking Water Reservoir

Raftis, Robyn R. 12 October 2007 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / The focus of this study was to document phosphorus (P) and metal cycling in the Eagle Creek Reservoir (ECR), located in Indianapolis, central Indiana. Eagle Creek Reservoir serves the drinking water needs of over 80,000 residents. Within the last several years, algal blooms have created stress to the local treatment facility. The objective of this study was to examine how P cycling from oxygen deprived bottom sediments affects the algal bloom productivity. As such, cores were retrieved from different water depths (7 and 16 m) from portions of the reservoir where high surficial concentrations of organic matter and P were found to occur. The dried samples were analyzed for P, sulfur, iron, barium, cadmium, copper, lead, and zinc, using a strong acid digestion technique. The samples were also analyzed for iron-bound P (Fe-P), authigenic P (A-P), detrital P (D-P), organic P (O-P), reducible iron, and reducible manganese, using a sequential extraction technique. The results from the study showed moisture contents ranged from 16 to 76% and organic matter contents ranged from 2 to 12 wt%. The dry bulk densities were determined to be between 0.27 and 1.68 g cm3. The average percentages of P in ECS-1, as determined by the sequential extraction method, were as follows: Fe-P, 66.2%; A-P, 8.1%; D-P, 4.8%; and O-P, 20.9%. The average percentages of P in ECS-3, as determined by the sequential extraction method, were as follows: Fe-P, 77.0%; A-P, 6.5%; D-P, 2.8%; and O-P, 16.7%. To determine relationships between elements, correlations were calculated. When looking as the relationships between the P fractions and reducible Fe, differences were observed between the different water depths. There was less correlation between reducible Fe and Fe-P, and between O-P and Fe-P, in ECS-3, indicating that Fe-P is more efficiently dissolved and recycled in the deep portion of ECR. The study shows that the Fe-P flux, caused by the iron redox cycle, is persistent and will continue to influence algal bloom productivity in the deeper portions of ECR.

Page generated in 0.1428 seconds