• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 146
  • 47
  • 29
  • 14
  • 13
  • 13
  • 4
  • 4
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 345
  • 345
  • 103
  • 72
  • 53
  • 41
  • 40
  • 37
  • 29
  • 28
  • 27
  • 26
  • 25
  • 23
  • 22
  • 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.
31

Undersökning av metallhalter i vattendrag till och från sjön Råsvalen : En studie på uppdrag av Länsstyrelsen i Örebro län

Warnicke, Caroline January 2014 (has links)
The aim of this study was to examine the metal contributions to and from the lake Råsvalen, in northern Örebro County in Sweden, from incoming and outgoing streams.  The main questions were: what is the metal concentration in the streams? How large is the metal transport from the streams, do the concentrations imply a risk for the biota, and can any source be identified. Water was sampled at six locations at six occasions with two-week intervals. The water samples were analyzed for total metal concentrations. The results were compared to environmental quality standards; EQS and from Swedish environmental protection agency suggested class limits. The concentrations were also compared to deviations from background levels and estimations of risk for biological effects. Metal transport was calculated from the average measured concentrations and water flow data from SMHI. Data from sediment analysis in 1989 was included for information about temporal trends. Zn, Cu, and Pb had concentrations above the limits and therefore they could have an effect on biota in water. Zn had a maximum concentration of 39 µg/l in Storån, which is 12 times higher than limits. Pb was found in a maximum concentration of 4,3 µg/l in Hammarskogsån downstream, which is more than twice as high as EQS. Cu was found in concentration of 6,1 µg/l in Storån downstream. Comparison with estimations of biological effects showed no or little effects except for Pb in Hammarskogsån downstream and Storån showing moderate risk. The stream that contributes most to metal influx is Storån. The stream stands for >80% of the total estimated metal transport. Possible sources could be historical mining, and higher levels upstream may contribute to the metal levels found in Storån.
32

Groundwater surface water interactions in a wetland rich, low relief Boreal environment

Tattrie, Kevin 04 August 2011 (has links)
This study investigates surface water and groundwater interactions in a wetland/peatland region surrounding Fort McMurray, Alberta. This work measured local meteorology, water table variation, and isotope and geochemistry concentrations over a two year period. Results from vertical water budget calculations showed episodic runoff events ranging between 0 and 38 mm/yr. Groundwater evaluations showed limited groundwater gradients with mean hydraulic conductivities of 1.01*10-5 cms-1 (NE7) and 1.78 * 10-5 cms-1 (SM8). Overall, groundwater flux estimates were variable and heterogeneous across the catchments areas. Isotopic composition showed mixing between winter precipitation, groundwater and surface water, with groundwater representing the average input signature. This study showed that runoff events were largely associated with spring freshet and significant summer storm events. / Graduate
33

Ocorrência de compostos farmacológicos no Córrego da Onça, município de Três Lagoas - MS /

Pinheiro, Juliana Heloisa Pinê Américo. January 2010 (has links)
Orientador: Sérgio Luís de Carvalho / Banca: Alessandro Minillo / Banca: Cristiano Poleto / Resumo: A contaminação dos ecossistemas aquáticos por compostos farmacológicos intensificou-se nos últimos anos devido ao aumento da produção e ao consumo desenfreado destas substâncias pela população. Estes compostos são encontrados em águas naturais e em efluentes de Estações de Tratamento de Esgoto (ETE), comprovando que sua presença em águas naturais é um indicativo de contaminação por águas residuárias de ETE. A presente pesquisa avaliou a ocorrência de compostos farmacológicos no Córrego da Onça, município de Três Lagoas (MS), bem como as relações específicas entre os pontos de monitoramento do corpo d'água. Assim, foram coletadas mensalmente, em um período de 12 meses amostras de água (1L) em seis pontos distintos representando diferentes seções do córrego. As amostras foram submetidas ao processo de extração em fase sólida e analisadas por cromatografia líquida de alta eficiência. Fármacos como atenolol, diclofenaco, ibuprofeno, naproxeno, paracetamol e piroxicam foram detectados nos pontos de coleta do corpo d'água. Com auxílio de uma ferramenta estatística, os pontos amostrais foram reunidos em duas classes, observando-se maior similaridade entre P1(Lagoa do Meio) e P2 (Lagoa Maior), e entre P4 (Jusante da ETE) e P5 (Novas Nascentes). Os resultados evidenciam a contaminação no córrego por compostos farmacológicos, possivelmente devido aos indícios de ligações clandestinas de esgoto sanitário e/ou não eficiência do sistema utilizado pela ETE do município de Três Lagoas. / Abstract: The contamination of aquatic ecosystems by pharmacological compounds has intensified in recent years due to increased production and consumption of these substances by population. These compounds are found in natural waters and effluents from sewage treatment plants (WTP), confirming that their presence in natural waters is indicative of contamination by wastewater from WTP. This study investigated the occurrence of pharmacological compounds in the Stream of Onça at TrêsLagoas (MS), and the specific relationships between the monitoring points of the waterbody. Water samples were collected monthly, over a period of 12 months (water samples 1L) at six different points representing different sections of the stream. The samples were subjected to the process of solid phase extraction and analyzed by high performance liquid chromatography. Drugs such as atenolol, diclofenac, ibuprofen, naproxen, paracetamol and piroxicam were detected in the sampling points of the waterbody. A statistical tool aided to divide the sites into two classes, with a greater similarity between P1 (Middle Pond) and P2 (Major Pond), and between P4 (Downstream of WTP) and P5 (New springs). The results show that the stream contamination by pharmacological compoundsis an indication of illegal connections of sanitary sewer and/or inefficiency of the system used by WTP of Três Lagoas (MS). / Mestre
34

Ocorrência de compostos farmacológicos no Córrego da Onça, município de Três Lagoas - MS

Américo, Juliana Heloisa Pinê [UNESP] 01 October 2010 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:29:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-10-01Bitstream added on 2014-06-13T19:59:00Z : No. of bitstreams: 1 americo_jhp_me_ilha.pdf: 1150853 bytes, checksum: 22eb0045ed6531c06a06108c015b424b (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A contaminação dos ecossistemas aquáticos por compostos farmacológicos intensificou-se nos últimos anos devido ao aumento da produção e ao consumo desenfreado destas substâncias pela população. Estes compostos são encontrados em águas naturais e em efluentes de Estações de Tratamento de Esgoto (ETE), comprovando que sua presença em águas naturais é um indicativo de contaminação por águas residuárias de ETE. A presente pesquisa avaliou a ocorrência de compostos farmacológicos no Córrego da Onça, município de Três Lagoas (MS), bem como as relações específicas entre os pontos de monitoramento do corpo d’água. Assim, foram coletadas mensalmente, em um período de 12 meses amostras de água (1L) em seis pontos distintos representando diferentes seções do córrego. As amostras foram submetidas ao processo de extração em fase sólida e analisadas por cromatografia líquida de alta eficiência. Fármacos como atenolol, diclofenaco, ibuprofeno, naproxeno, paracetamol e piroxicam foram detectados nos pontos de coleta do corpo d’água. Com auxílio de uma ferramenta estatística, os pontos amostrais foram reunidos em duas classes, observando-se maior similaridade entre P1(Lagoa do Meio) e P2 (Lagoa Maior), e entre P4 (Jusante da ETE) e P5 (Novas Nascentes). Os resultados evidenciam a contaminação no córrego por compostos farmacológicos, possivelmente devido aos indícios de ligações clandestinas de esgoto sanitário e/ou não eficiência do sistema utilizado pela ETE do município de Três Lagoas. / The contamination of aquatic ecosystems by pharmacological compounds has intensified in recent years due to increased production and consumption of these substances by population. These compounds are found in natural waters and effluents from sewage treatment plants (WTP), confirming that their presence in natural waters is indicative of contamination by wastewater from WTP. This study investigated the occurrence of pharmacological compounds in the Stream of Onça at TrêsLagoas (MS), and the specific relationships between the monitoring points of the waterbody. Water samples were collected monthly, over a period of 12 months (water samples 1L) at six different points representing different sections of the stream. The samples were subjected to the process of solid phase extraction and analyzed by high performance liquid chromatography. Drugs such as atenolol, diclofenac, ibuprofen, naproxen, paracetamol and piroxicam were detected in the sampling points of the waterbody. A statistical tool aided to divide the sites into two classes, with a greater similarity between P1 (Middle Pond) and P2 (Major Pond), and between P4 (Downstream of WTP) and P5 (New springs). The results show that the stream contamination by pharmacological compoundsis an indication of illegal connections of sanitary sewer and/or inefficiency of the system used by WTP of Três Lagoas (MS).
35

Desenvolvimento e validaÃÃo de um mÃtodo analÃtico (SPEâHPLC) para determinaÃÃo de compostos emergentes em Ãguas superficiais. / Development and validation of an analytical method (SPE- HPLC) for determination of emerging compounds in surface waters

Sarah de Abreu Moreira AraÃjo 31 January 2014 (has links)
CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Poluentes orgÃnicos emergentes (POEs) ou simplesmente contaminantes emergentes referem-se a qualquer composto quÃmico presente numa variedade de produtos comerciais como medicamentos, produtos de uso veterinÃrio, embalagens de alimentos, produtos de higiene, agrotÃxicos, ou alguns microrganismo. Os POEs podem ser encontrados em matrizes ambientais e biolÃgicas, nÃo sÃo usualmente monitorados ou ainda nÃo possuem legislaÃÃo regulatÃria correspondente, e apresentam risco potencial à saÃde humana e ao meio ambiente. Neste trabalho, foi desenvolvido e validado um mÃtodo para a determinaÃÃo de cafeÃna, ciprofloxacina, 17β-estradiol, 17α-etinilestradiol e dietilestilbestrol, considerados interferentes endÃcrinos. O mÃtodo desenvolvido utilizou extraÃÃo em fase sÃlida (SPE) e cromatografia lÃquida de alta eficiÃncia acoplada a um detector de arranjo de diodos. Foram estabelecidas condiÃÃes cromatogrÃficas com eluiÃÃo por gradiente utilizando acetonitrila e Ãgua ultrapura pH 2,0. O planejamento fatorial realizado por SPE indicou que melhores respostas sÃo alcanÃadas quando utiliza-se o cartucho C18, 500 mL de volume de amostra, pH 3,0 e volume de eluiÃÃo igual a 2,0 mL de metanol 100%. As figuras de mÃrito de validaÃÃo do mÃtodo indicaram seletividade, sensibilidade, linearidade, precisÃo, exatidÃo e robustez satisfatÃrias para a maioria dos compostos estudados. Os limites de detecÃÃo (LD) variaram entre 0,283 e 1,543 μg/L (ppb) e os limites de quantificaÃÃo (LQ) variaram entre 0,944 e 5,142 μg/L (ppb). Foi proposta uma nova estratÃgia de controle de qualidade utilizando padrÃo surrogate, e estabelecido um fator de relaÃÃo (FR) a fim de corrigir as concentraÃÃes dos compostos de interesse em amostras reais. O mÃtodo validado foi aplicado nas anÃlises de Ãgua superficial dos aÃudes que fazem parte do abastecimento de Ãgua da RegiÃo Metropolitana de Fortaleza/CE. Os compostos 17β-estradiol, 17α-etinilestradiol foram detectados numa concentraÃÃo mÃxima de 989 e 980 ng/L, respectivamente. / Emerging organic pollutants (EOP), or Emerging Contaminants, is a term that is used to refer any chemical compound insert in variety of comercial products such as medicines, veterinary products, food packaging, pesticides, or any microorganism. The EOP can be found in environmental and ecological arrays not usually monitore or government unregulated, and poses risks to human health na environment. The methodological approach of this thesis included a developed and validated method to determine caffeine, ciprofloxacin, 17β-estradiol, 17α-ethinylestradiol and diethylstilbestrol, considered endocrine disruptors. The method uses a Solid-Phase Extraction (SPE) and high performance liquid cromatography coupled to a diode array detector. Chromatografic conditions were established by gradiente elution using acetonitrile and ultrapure water (pH = 2). The experimental design performed by SPE showed that better responses are achieved when it is used the cartridge C18, 500 mL sample volume, pH 3,0 and 2,0 mL 100% methanol elution volume. The method validation parameters indicated satisfatory selectivity, sensitivity, linearity, precision, accuracy and robustness. Detection limits (DL) ranged from 0,283 to 1,543 μg/L (ppb) and quantification limits (QL) ranged from 0,944 e 5,142 μg/L (ppb). A new quality control strategy using surrogate standard was proposed, and a relation factors (RF) was established to correct of concentrations of compounds of interest in real samples. The validated method was applied to the analysis of surface waters reservoirs from water supply system in metropolitan region of Fortaleza. The compounds 17β-estradiol, 17α-ethynyl estradiol was detected in a maximum concentration of 989 to 980 ng / L, respectively.
36

Determination of groundwater-surface water interaction, upper Berg River catchment, South Africa

Madlala, Tebogo Eugene January 2015 (has links)
>Magister Scientiae - MSc / The present study investigated the application of a multi-method approach to determine groundwater-surface water (GW-SW) interactions to quantify and characterize the quality of water resources in a fractured rock aquifer system in upper catchment of the Berg River (G10A). Demonstrating methods for improved understanding of groundwater and surface water interactions is important for informing development of strategies that ensure effective utilization and management of water resources. Applying a single method to inform innovative strategies for water resources has proved futile. The current study shows how the use of several methods can provide the basis for devising practical strategies for water resource utilization and management. The three methods were applied as follows: First, the base flow separation was used whereby the Chapman and Lynne & Hollick digital filter algorithms were applied to time-series streamflow data from four stream gauging stations in the catchment. The computation from algorithms on three sites (gauging stations) showed that the mean Base Flow Index (BFI) value ranged between 7%-8% for the 2012-2014 periods. This means that discharges from subsurface water storages dominate stream flows throughout the study period. Secondly, the quality of groundwater and surface water was sampled using standard methods. Piper Diagrams generated on Aquachem™ software and radial charts were used to identify the predominant hydrochemical facies. Results showed that Na-Cl was the predominant GW and SW water-type. This means that both GW and SW are mainly influenced by recharging surface water as well as interaction occurring between the rock matrices and infiltrating water. Multivariate statistical analyses were used to evaluate the factors controlling GW and SW chemistry in the upper Berg River catchment and the results showed that GW and SW are influenced by natural processes. Two main factors (a. & b.) were extracted which explained 71.8% of the variation in both GW and SW physicochemical parameters. These factors include water-rock interactions and the recharge of surface water. Cluster Analysis extracted four major clusters that grouped sites with similar physicochemical characteristics together. Finally, differential stream gauging was applied to a 600m reach above the Berg River Dam. Three 200m sub-reaches were used to compute differences in flows between sub-reaches. Stream flow at each sub-reach was estimated using mass balance equations with electrical conductivity measurements during instant salt tracer injection tests. Results indicated that during both the wet season (high flow) dry season (low flow), the river continuously lost water to the subsurface. This was demonstrated by the 0.91m³/s and 2.24m³/s decrease in stream flow along the 600m reach. Dry season flow decreases were less than wet season flow decreases, indicated by markedly lower flow loss in respect to the wet season. This confirms results of the analysis of base flow separation, which indicated that discharges from subsurface storages dominate stream flows during low flow periods. The differential stream gauging approach did not provide distinct points along the selected stream reach where GW-SW interaction occurred; rather it provided a holistic representation of seasonal flow variations along the selected reach. This study showed that upper Berg River catchment is dependent on discharges from subsurface water storages to maintain dry season flows. Furthermore, this study showed that infiltration of surface water and discharge of subsurface water transfers the respective chemical signature of the contributor, meaning that the transfer of water of suitable quality will reduce contamination in the receiving water body (i.e. surface water). Transfer of water between subsurface and surface water contributed an average of 8% of the gauged flows in the catchment between 2012 and 2014, suggesting that the groundwater recharge process dominates this catchment.
37

Integrated Surface-Ground Water Modeling in Wetlands With Improved Methods to Simulate Vegetative Resistance to Flow

Nalesso, Mauro 04 November 2009 (has links)
This dissertation focused on developing an integrated surface – subsurface hydrologic simulation numerical model by programming and testing the coupling of the USGS MODFLOW-2005 Groundwater Flow Process (GWF) package (USGS, 2005) with the 2D surface water routing model: FLO-2D (O’Brien et al., 1993). The coupling included the necessary procedures to numerically integrate and verify both models as a single computational software system that will heretofore be referred to as WHIMFLO-2D (Wetlands Hydrology Integrated Model). An improved physical formulation of flow resistance through vegetation in shallow waters based on the concept of drag force was also implemented for the simulations of floodplains, while the use of the classical methods (e.g., Manning, Chezy, Darcy-Weisbach) to calculate flow resistance has been maintained for the canals and deeper waters. A preliminary demonstration exercise WHIMFLO-2D in an existing field site was developed for the Loxahatchee Impoundment Landscape Assessment (LILA), an 80 acre area, located at the Arthur R. Marshall Loxahatchee National Wild Life Refuge in Boynton Beach, Florida. After applying a number of simplifying assumptions, results have illustrated the ability of the model to simulate the hydrology of a wetland. In this illustrative case, a comparison between measured and simulated stages level showed an average error of 0.31% with a maximum error of 2.8%. Comparison of measured and simulated groundwater head levels showed an average error of 0.18% with a maximum of 2.9%.
38

Spatial and Temporal Mapping of Distributed Precipitation, Surface and Groundwater Stable Isotopes Enables Insights into Hydrologic Processes Operating at a Catchment Scale

Cole, Alison 29 October 2019 (has links)
Isotopic analyses of d18O and d2H of water through the hydrologic cycle have allowed hydrologists to make better interpretations related to climate and relationships between precipitation, surface water, and groundwater. In this study 394 precipitation samples 1917 surface water samples and 1405 groundwater samples across Massachusetts was used to create an isoscape for each respective water. All samples have been collected by volunteers throughout Massachusetts. A state meteoric water line: d2H = 7.7*d18O + 9.8, surface water line: d2H = 5.7*d18O – 4.2, and groundwater line: d2H = 6.5*d18O + 2.9 was created for the state of Massachusetts. The d18O isoscape for each of the above-mentioned waters shows an isotopic separation along an east-west topographic gradient where isotopes were enriched in the eastern portion of Massachusetts and depleted in the western portion of Massachusetts. Precipitation, surface water, and groundwater show unique isotopic variability. The isotopic variability of precipitation is primarily due to seasonality, moisture source and differences in topography across Massachusetts. The d18O and d2H isotopic variability of surface water is due to a biasing of precipitation as well an enrichment due to an open water system as the surface water dataset correlates with surface water type and precipitation isotopic values. The d18O and d2H isotopic variability of groundwater is due to the dampening of surface water and precipitation because of hydrogeologic processes and the biasing of surface waters that have gone through open water isotopic variability.
39

A Novel Infield Metagenomic Approach to Evaluating Surface Water Quality in Lake Warner

Stebbins, Brooke 29 October 2019 (has links)
In January 2010, a magnitude 7.0 earthquake devastated Haiti, one of the poorest countries in the Western Hemisphere. Haiti’s weak sanitation infrastructure and limitations in the public health system made the country susceptible to the spread of waterborne diseases. Following the earthquake, cholera rapidly spread through Haiti, killing 4,672 people in 5 months and leaving thousands hospitalized (MSNBC, 2010). Cholera is an infectious diarrheal disease caused by the pathogen, Vibrio cholerae, which results in severe dehydration with a high mortality risk. The source of the epidemic was traced to the Artibonite River, the island’s longest and most essential drinking water source (Encyclopaedia Britannica. n.d.). The origin of the contamination was later discovered to be unsanitary conditions left from United Nations peacekeepers from Nepal. Eight years later, cholera cases are still prevalent, although numbers have declined recently due to aid from private organizations (Dowell, S.F. et al 2011, Katz, J.M. 2013). However, with climate-related increases in ocean water temperatures, scientists expect hurricanes to intensify and increase damage to developing countries (Center for Climate and Energy Solutions. n.d.). Natural disasters promote the spread of waterborne illness by isolating people from safe drinking water and destroying public health infrastructure such as happened with the cholera outbreak in Haiti (Funari, E. et al 2013). To prevent future waterborne disease epidemics in such areas with limited resources, it would be beneficial to improve environmental surveillance through development of rapid, reliable, and portable detection methods for waterborne pathogens. The advent of high-throughput sequencing technologies has enabled the detection and characterization of microbial communities in their natural environments, an approach known as metagenomics. Metagenomic sequencing, unlike more traditional PCR methodologies, is capable of sequencing thousands of organisms in a sample. This metagenomic shotgun sequencing approach detects the abundance of microbes and bacterial diversity in the environment (Illumina, n.d.). The Oxford Nanopore MinION is a shotgun sequencing device that is optimal for portable, rapid detection of the microbial diversity in an environmental sample (Oxford MinION, n.d.). This handheld device has enormous potential for field use in emergency preparedness and disease response, particularly in developing countries where more advanced analytical equipment may be inaccessible due to lack of facilities or damaged infrastructure. Having access to quick, infield assessment technology for rapidly emerging outbreaks would be beneficial to a disease-specific public health response. Current protocols recommend that DNA is extracted from environmental samples as rapidly as possible after collection. If cooling is available with an insulated ice chest, samples may be transported/stored for periods ranging from 6 to 24 hours. The shorter timeframes minimize unwanted shifts in microbial structure (U.S. Geological Survey, 1997, WHO, n.d.). Access to cold storage in remote areas is unlikely, and the use of liquid preservation methods could assist in maintaining quality of DNA, and hence produce more accurate data in metagenomic analyses. In the absence of cold storage facilities, infield filtration coupled with preservation techniques are necessary to maintain samples integrity for transport to laboratory facilities. This thesis aimed to develop an infield filtration and sequencing protocol, coupled with the Oxford Nanopore MinION sequencing platform, to identify the potential bacteria, viruses, protozoa, fungi, antimicrobial resistance (AMR), pathogenic strains, and virulence associated genes for use in remote locations. Five locations across Lake Warner, Massachusetts were used for method development, coupled with Millipore Sterivex filters for field filtration to determine the most effective method for sample preparation in remote locations. Additionally, a chemical preservation method was assessed using dimethyl sulfoxide, disodium EDTA, and saturated NaCl (DESS). A study by Gray et al, found that liquid preservation methods (DNAgard, RNAlater, and DESS) outperformed the card-based preservatives (FTA cards and FTA Elute cards) in terms of bacterial recovery (Gray, M.A., et al 2013). DESS was selected for investigation in this thesis because of the low cost compared to the other liquid-based preservatives. Lake Warner in Hadley, Massachusetts, which is heavily used for fishing and boating activities, flows into the Connecticut River via the Mill River. Historically, the lake experienced high Escherichia coli (E. coli) levels due to pollution from primary effluent released in the 1950s from the Amherst Wastewater Treatment Plant (Johnson, J., 2015). Similar to Vibrio cholerae, E.coli spp is a waterborne bacteria caused by fecal contamination. Although most E.coli are natural inhabitants of the gastrointestinal tract, pathogenic serotypes can result in severe complications in vulnerable populations such as kidney failure in children and the elderly adults. (Todar, K., 2012). Lake Warner was chosen for the method development because of its history of E. coli pollution and recreational traffic as well as its general accessibility for study. Designing a methodology for rapid detection of pathogenic bacteria using a metagenomic approach could help improve surveillance for environmental pathogens that pose future epidemic risk. These tools are becoming increasingly important for prediction and response to waterborne diseases as climate impacts increase the frequency, intensity, and duration of extreme weather events that damage critical infrastructure for vulnerable populations (van Aalst, M.K. 2006).
40

Investigation Into the Source of Contamination of Surface Waters Flowing Through The WrightState University Woods

Okeke, Nnadozie Kennedy 20 August 2021 (has links)
No description available.

Page generated in 0.0388 seconds