• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 80
  • 37
  • 9
  • 5
  • 5
  • 5
  • 5
  • 5
  • 5
  • 4
  • 3
  • 1
  • 1
  • 1
  • Tagged with
  • 173
  • 173
  • 63
  • 55
  • 47
  • 21
  • 21
  • 17
  • 16
  • 16
  • 15
  • 14
  • 14
  • 14
  • 13
  • 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.
131

Vulnerabilidade e perigo de contaminação dos aquíferos nas sub-bacias do Alto Aguapeí e Alto Peixe - SP

Montero, Rafael Carrion [UNESP] 14 December 2012 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:26:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-12-14Bitstream added on 2014-06-13T19:13:18Z : No. of bitstreams: 1 montero_rc_me_bauru.pdf: 2401420 bytes, checksum: edf8873c33a227bcb3f0d5bb72554719 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A crescente demanda por recursos subterrâneos nas Bacias Hidrográficas dos Rios Aguapaí e Peixe, localizadas no oeste do Estado de São Paulo e a presença cada vez maior de substâncias em condições de acesso e contaminação das águas em subsuperfície têm pressionado de forma negativa a disponibilidade hídrica nessas bacias. Neste contexto de degradação, esta Dissertação objetiva a caracterização e avaliação da vulnerabilidade natural e dos perigos de contanimação das unidades aquíferas aflorantes nas subunidades de gestão de recursos hídricos denominados Alto Aguapeí e Alto Peixe. A caracterização da Vulnerabilidade foi realizada com aplicação do método GOD (Foster & Hirata, 1988). O perigo de contaminação dos aquíferos foi avaliado mediante a interpolação da vulnerabilidade natural com as fontes potencias de contaminação, identificadas e classificadas quanto o seu potencial de gerar carga contaminante, a partir da aplicação do método POSH (FOSTER et al, 2006). Os procedimentos de geoprocessamento foram realizados com auxílio do SIG ArcMap TM 9.3. Os resultados demonstraram que vulnerabilidades de classificação Extrema estão restritas as planícies fluviais dos rios Aguapeí e Tibiriça, ocupando cerca de 2% da área de estudos, as classes de vulnerabilidade Alta e Alta Baixa ocupam 41,5% e 23,7% respectivamente, enquanto 28,4% da área correspondem à vulnerabilidade Média. Para o restante da área obteve-se a classificação Média e Média Baixa Vulnerabilidade. A correlação das vulnerabilidades com as fontes potenciais de contaminação demonstraram que independente da localização, os postos de combustível e os locais de disposição de resíduos sólidos apresentam Alto perigo de contaminação. As atividades da indústria, por sua vez, apresentam Alto perigo de contaminação para os distritos... / The increasing demand for groundwater resources in the Watersheds of Aguapeí and Peixe Rivers, located in the western part of São Paulo province, and also the increasing presence of substances in access condition and water contamination in the subsurface have been pressuring negatively the water availability in both basins. In this degradation context, this dissertation aims to characterize and evaluate the natural vulnerability and contamination risks of aquifers outcropping units in the sub water resources management units called. Alto Aguapeí and Alto Peixe. The vulnerability characterization was made applying the GOD method (Foster & Hirata, 1988). The aquifers contamination risk was estimated by interpolation of the natural vulnerability and the potential contamination sources that was identified and classified by their potential to generate contaminant load, using the POSH method (Foster et al, 2006). The geoprocessing producers were performed with assisting of some tools from the GLS ArcMap TM 9.3. The results evidenced that extreme classification vulnerability are restricted just for river plaints of Aguapeí and Tibiriça rivers, occupying around 2% of the studied area. The High and High Low vulnerability classes occupy 41.5% and 23.7% respectively and average vulnerability 28.4%. For the rest of the area was obtained medium and low vulnerability classification. The correlation of vulnerabilities and potential sources of contamination demonstrated that regardless of location, gas stations and solid waste disposal spots have high risks of contamination. The industrial activities have a high risk of contamination due the industrial district of Garça and Marilia and moderate for units in the food sector, located outside these districts. Furthermore, it is evident the importance of introducing the territory management policies... (Complete abstract click electronic access below)
132

Potencial tóxico da água intersticial de lagoas costeiras e água subterrânea sobre caenorhabditis elegans, Osório - Rio Grande do Sul

Michalski, Elias Zientarski 18 December 2017 (has links)
Submitted by cmquadros@ucs.br (cmquadros@ucs.br) on 2018-03-22T17:27:06Z No. of bitstreams: 1 Documento confidencia Elias.pdf: 815556 bytes, checksum: 36814b2a7bfc419a360108beccbea95f (MD5) / Made available in DSpace on 2018-03-22T17:27:06Z (GMT). No. of bitstreams: 1 Documento confidencia Elias.pdf: 815556 bytes, checksum: 36814b2a7bfc419a360108beccbea95f (MD5) Previous issue date: 2018-03-22
133

Potencial tóxico da água intersticial de lagoas costeiras e água subterrânea sobre caenorhabditis elegans, Osório - Rio Grande do Sul

Michalski, Elias Zientarski 18 December 2017 (has links)
No description available.
134

Avaliação de risco à saúde humana decorrente da contaminação da água subterrânea por BTEX provenientes de postos de revenda de combustíveis em Manaus

Lima, Rita Mileni de Souza 07 December 2010 (has links)
Submitted by Elaine Lucia (lucia.elaine@live.com) on 2015-06-26T18:02:33Z No. of bitstreams: 1 Dissertação - Rita Mileni de Souza Lima.pdf: 2126876 bytes, checksum: a214fbd9d08a6c1dcf4fc81b0c2d44db (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-06-29T14:13:28Z (GMT) No. of bitstreams: 1 Dissertação - Rita Mileni de Souza Lima.pdf: 2126876 bytes, checksum: a214fbd9d08a6c1dcf4fc81b0c2d44db (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-06-29T14:32:10Z (GMT) No. of bitstreams: 1 Dissertação - Rita Mileni de Souza Lima.pdf: 2126876 bytes, checksum: a214fbd9d08a6c1dcf4fc81b0c2d44db (MD5) / Made available in DSpace on 2015-06-29T14:32:10Z (GMT). No. of bitstreams: 1 Dissertação - Rita Mileni de Souza Lima.pdf: 2126876 bytes, checksum: a214fbd9d08a6c1dcf4fc81b0c2d44db (MD5) Previous issue date: 2010-12-07 / CAPES / Nowadays, Manaus has 175 gas stations, and it is estimated that de lifespan of them, that is around 25 years it is near to the end. This increase the probability of gasoline spills that contains Benzene, Toluene, Methylbenzene and Xylenes (BTEX), and, because of their toxicity and potentially adverse health effects it may become a risk for the general population, if groundwater is contaminated. Hence, the main goal of this study was estimate BTEX exposure through groundwater, as well as the human health risks associated with this exposure. A total of 38 gas stations were visited, and samples of groundwater were taken. Samples were analyzed by gas chromatography fitted with a flame ionization detector (FID), after headspace solid phase microextraction. Human exposure was estimated as a combination of three pathways: inhalation, direct ingestion, and dermal absorption during bath for adult men and women, children and babies. Deterministic and probabilistic risk was assessed. Cancer risk for benzene was estimated in 70% of gas stations from south zone and in 40% from north zone, for all genders and ages. At central-south and west zone, no cancer risk associated with benzene was determined. Cancer risk for benzene was estimated to be between 5xE−05 and 105xE−05 above the limit value of 1xE-05. The children were exposed a higher risks. Non-cancer risk associated with benzene were determined in North and South zones, and associated with xylenes in CentralSouth zone. For probabilistic assessment the 95th percentile of risk was estimated to be 6E−05, indicating that cancer risk is not negligible. Non-carcinogenic risks for toluene, ethylbenzene, and xylenes were lower than the specified level of 1.0. Since health risk associated to BTEX was identified, a monitoring routine need to be implemented by environmental and public health agencies. / Em Manaus existem atualmente 175 postos de gasolina, e estima-se que a vida útil dos tanques de armazenamento de combustíveis desses postos, que é de aproximadamente 25 anos, esteja próxima do final. Assim, aumenta a possibilidade de ocorrência de vazamento ou derramamento de gasolina que contém Benzeno, Tolueno, Etilbenzeno e Xilenos - BTEX, substâncias tóxicas que podem colocar em risco a saúde da população se houver contaminação da água subterrânea, importante fonte de abastecimento domiciliar. Desta forma o objetivo deste trabalho foi avaliar os riscos à saúde humana decorrentes da contaminação da água por BTEX a partir da gasolina provenientes dos postos de revenda de combustíveis da cidade de Manaus. Para isso foi realizado um levantamento dos postos de revenda com poços de água subterrânea, bem como suas condições e tempo de funcionamento. Para quantificação de BTEX na água foram amostrados 38 poços. A análise dos BTEX foi realizada por cromatografia gasosa com detector FID após micro - extração em fase sólida – SPME com headspace. A exposição pela ingestão da água, absorção dérmica e inalação durante o banho foram estimadas para homens, mulheres, crianças e bebês. Foi avaliado o risco de forma determinística e probabilística. Riscos carcinogênicos pela exposição ao benzeno foram encontrados em 70% dos postos na zona sul e 40% da zona Norte para todas as faixas etárias e gêneros. Nas zonas centro-sul, leste e oeste não foram detectados riscos carcinogênicos pela exposição ao benzeno. Nas zonas onde foi encontrado risco de câncer, o mesmo variou de 5 a 10 casos a cada 100.000 habitantes, estando estes valores acima do limite estabelecido de 1 caso para cada 100.000 habitantes. As crianças são o grupo etário exposto a maiores riscos. Em relação aos riscos não carcinogênicos pela exposição aos BTEX, a exposição ao benzeno representou riscos nas zonas norte e sul, e a exposição aos xilenos na zona centro sul. Na avaliação probabilística, o risco carcinogênico para o percentil de 95% da população foi menor que 6 casos por zona, confirmando os dados da avaliação determinística. Os riscos não carcinogênicos com exceção do benzeno, não foram significativos para os demais TEX. Assim, a avaliação indicou riscos à saúde relacionados aos BTEX oriundos de vazamentos de combustíveis de posto de revenda existentes na cidade. As zonas centro-sul, norte e sul são as zonas onde os riscos aos BTEX foram significativos, logo a implantação de uma rotina de monitoramento por parte da agência de controle ambiental bem como da vigilância à saúde se faz necessário, uma vez que o uso da água subterrânea oferece riscos carcinogênicos à população.
135

Assessment of the effects of gold-mine effluent on the natural aquatic environment

Venter, Andries J.A. 21 May 2014 (has links)
D.Phil. (Zoology) / South Africa is a major gold-producing country with the 43 larger mines processing approximately 120 x 106 ton of milled and processed ore and about 30 x I06 ton of mined waste rock. Pollution of both surface and ground water, which can be attributed to the influences of gold-mining, are well known. Acid mine drainage, characterized by a low pH and high concentrations of dissolved metals, and seepage, from active and disused mine-tailings, are two of the main environmental problems associated with gold mining operations in South Africa. A growing concern for the environment and a stricter approach to water pollution by government agencies have made it necessary to investigate the type of effects which the gold mining industry is responsible for, and to develop action to reduce these impacts. The present study focused on procedures to access the effect of gold-mining effluent on the natural surface environment. The study is divided into three separate identities. The mine represented as Ccse study Mine One is considered to be a major contributor of salt loads to the natural stream on the property of the mine. This stream confluences with the Klip River outside the mined area. This mine has only one discharge point of underground mine service water, and is considered to be the main point source of pollution for the mine. As the mine makes use of an open water circuit, the quality and quantity of effluent have a direct effect on the downstream users. It appears that one of the main water quality problems of this open water circuit is the creation of surface water with a very low pH. Part of the problem is the geology of the area which consists of shales, which has a natural low buffering capacity. Because of the low pH the wetlands are not very effective. Metal concentration changes are possibly the direct result of the low pH of the both the water column and sediment. Improving the pH of the surface water can leads to reduced metal concentrations in the water, with possible increased concentrations in the sediment and wetland vegetation. Case Study Mine Two was conducted at a gold mine in the Far West Rand Mine region. The mine can be classified as having a closed water circuit, in that only excess water is discharged. The volume of water discharged is dependent on a number of factors, such as rainfall, wash-down service water and changing demands in sewage treatment systems. The advantage in this type of circuit is that water which has accidentally been spilled can be retained in one of the boundary dams, without the possibility of endangering the downstream users. From the assessment it appears that although the mining activities have influenced the water within the mining area this impact is only confirmed to certain areas. Biotic environmental conditions at certain sites resemble the conditions of the two control sites while other, notably those in contact with processing plants (e.g. metallurgical plant), are far more deteriorated. pH does not seem to be a problem at this specific mine. The main reasons are that the underlying geology of the mine is dolomitic in nature, while the sulphate concentration in the ore appears to be lower than those' found at the Witwatersrand mines. Case study Mine Three is situated in the Klerksdorp gold-mining region. The mine has a complex water circuit as a percentage of the service water is being reused or/and discharged via effluent streams into the Vaal River. Metal concentrations in the sediment core samples indicate a large variability between seasons, sites and depth. Sites in close proximity of slimes dams have high iron and manganese concentrations, whilst those in contact with effluent water from metallurgical plants have relatively high nickel, copper and in concentrations. This can be related to the type of processing material used in the gold-mining process.
136

Fate and Transformation of a Conjugated Natural Hormone 17β-Estradiol-3-Glucuronide in Soil-Water Systems

Shrestha, Suman Lal January 2011 (has links)
The objectives of the study were to investigate the sorption and degradation of a glucuronide conjugated natural hormone, 17β-estradio1-3-glucuronide (E2-3G), and its estrogenic metabolites in soil-water systems. Radiolabeled E2-3G was first synthesized in the laboratory. Soil-water batch experiments were then conducted using natural and sterilized topsoil (0-6 cm) and subsoil (18-24 cm) with the radiolabeled E2-3G to investigate the effects of soil organic matter content and microbial activity. The aqueous dissipation of 14C in the batch experiments followed a biphasic pattern with an initial rapid dissipation phase followed by a second slower phase. Significant differences in total aqueous 14C dissipation were observed for the different initial concentrations for both soils, with greater persistence of intact E2-3G at higher initial concentrations. / National Science Foundation [Grant No. 0730492]
137

Perfluorooctane acid (PFOA) and perfluorooctane sulfonate (PFOS) in the Plankenburg (Stellenbosch) and Diep (Milnerton) Rivers, and potential remediation using vitis vinifera leaf litter

Fagbayigbo, Bamidele Oladapo January 2017 (has links)
Thesis (DTech (Environmental Health))--Cape Peninsula University of Technology, 2017. / This study represents the first monitoring campaign to assess the seasonal trend of nine perfluorinated compounds (PFCs) in surface water and sediment from the Plankenburg and Diep Rivers in the Western Cape, South Africa. An analytical protocol was developed and validated for qualitative and quantitative routine determination of nine perfluorinated compounds (PFCs), in water and sediment samples using Ultra performance liquid chromatography-mass spectrometry quadrupole time of flight (UPLC-QTOF-MS). This method was applied to determine levels of PFOA and PFOS in environmental samples. Samples were collected along the Diep (Milnerton) and Plankenburg (Stellenbosch) Rivers respectively. Samples were pre-treated, cleaned-up and extracted using solid-phase extraction (SPE) procedures with hydrophilic-lipophilic balance (HLB) C-18 cartridges. Seasonal variation and distribution of PFCs in surface water and sediment was also investigated. Levels of PFCs were monitored in four seasons (summer, autumn, winter and spring) to establish their trend in the environment. The removal of PFOA and PFOS from aqueous solutions using agro-waste biomass of Vitis vinifera (grape) leaf litter was also studied. Activated carbons were produced from the biomass and chemical activation achieved with phosphoric acid (H3PO4) and potassium hydroxide (KOH) for the modification of the carbons’ (AC-H3PO4 and AC-KOH respectively). Activated carbons were characterized using Fourier Transform infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Brunauer- Emmett-Teller (BET) in order to understand the removal mechanisms of the contaminants by activated carbons. The effects of solution concentration, pH, adsorbent dosage, contact time, and the temperature were optimized for evaluation of the removal efficiency of the activated carbons. Adsorption isotherm models were used to analyze the equilibrium data obtained and kinetic models were applied to study sorption mechanisms. A fixed bed column study was conducted using: AC-H3PO4 adsorbent. Experimental parameters such as initial concentration of the solution, column bed height, flow rate and initial concentrations of the influent were optimized to establish the best adsorption efficiency parameters of the column system. Breakthrough curve and exhaustion time were predicted using Adam-Bohart, Yoon-Nelson, and Thomas models for the fixed bed column under varying experimental conditions.
138

Arsenic Mobility and Compositional Variability in High-Silica Ash Flow Tuffs

Savoie, Courtney Beth Young 22 July 2013 (has links)
Volcanic rocks typically have only low to moderate arsenic concentrations, none-the-less, elevated levels of arsenic in ground waters have been associated with pyroclastic and volcaniclastic rocks and sediments in many parts of the world. The potential for arsenic leaching from these deposits is particularly problematic as they often comprise important water-bearing units in volcanic terrains. However, the role that chemical and mineralogical variations play in controlling the occurrence and mobility of arsenic from pyroclastic rocks is largely unexplored. This study uses chemical and X-ray diffraction data to characterize and classify 49 samples of ash-flow tuffs, and 11 samples of tuffaceous sediments. The samples exhibit a range of devitrification and chemical weathering. Total and partial digestion, and water extractions of samples are used to determine the total, environmentally available, and readily leachable fractions of arsenic present in all tuff samples. Leaching experiments were also performed with buffered solutions to determine the influence of elevated pH levels on arsenic mobility. The 49 tuff samples have a mean arsenic content of 7.5 mg kg-1, a geometric mean arsenic content of 4.8 mg kg-1, a median arsenic content of 5.2 mg kg-1, and a maximum arsenic concentration of 81 mg kg-1. The mean and median values are 2.8 - 4.4x the average crustal abundance of 1.7 mg kg-1 (Wedepohl, 1995), and consistent with previously reported values for volcanic glasses and felsic volcanic rocks (Onishi and Sandell, 1955; Wedepohl, 1995), although the maximum arsenic content is higher than previously reported (e.g., Casentini et al., 2010; Fiantis et al., 2010; Nobel et al., 2004). In addition, the arsenic concentrations of tuffs were found to be highly heterogenous, both between and within individual units, and in some cases, individual outcrops. Results of whole rock and leachate analyses indicate that there is no significant difference in the total arsenic content of tuffs as a result of devitrification or weathering, but both devitrified and weathered tuffs contain higher levels of environmentally available arsenic than unweathered glassy tuffs. Glassy tuffs did not produce any readily leachable arsenic, while individual devitrified and weathered tuffs both generated aqueous concentrations that exceeded regulatory limits after 18 hours. Leaching of weathered tuffs produced higher levels of arsenic at high (~9-11) pH than in tests conducted at circum-neutral pH. Devitrified and glassy tuffs showed no increase in leachable arsenic with increasing pH. The results of this study indicate that devitrification and weathering processes determine the host phases, degree of adsorption, and overall mobility of arsenic from ash-flow tuffs. Tuffs that have undergone different types of alteration are likely to have different host phases of arsenic, and different mechanisms that mobilize arsenic into the environment. Potential host phases and mobility mechanisms are discussed, and a conceptual model of arsenic behavior in ash-flow tuffs is proposed.
139

A mathematical model for simulating pesticide fate and dynamics in the environment (PESTFADE) /

Clemente, Roberto Sulit January 1991 (has links)
No description available.
140

Numerical modelling of transport of pollutant through soils

Ahmad, Faheem 18 August 2009 (has links)
Prediction of subsurface migration of contaminant through soils involves analyses of unsaturated and saturated flow of water and advective dispersive transport of contaminant species. A finite element model is developed here for such an analysis. It is based on the transient nonlinear Richard's equation for the unsaturated flow and the mass transport equation using advective dispersive transport phenomenon. The model makes it possible to make advance predictions of the spread of the contaminant with respect to time and space, into the ground water system. The hydraulic properties of the unsaturated soils and the dispersion characteristics need to be obtained for such an analysis. The unsaturated flow parameters are obtained from a functional relationship between capillary pressure head and moisture saturation, and can be determined from laboratory tests on simple column samples of soils. A general expression is assumed to account for the effect of velocity dependence of the hydrodynamic dispersion coefficient in the mass transport problem. A computer program POLUT2D is developed based on the above assumptions. Pre and post processors for the computer program POLUT2D are also developed for interactive input of data and graphics displays of results. The computer program is first evaluated by comparing the results of a problem given in the literature with the results obtained by POLUT2D. The factors affecting the contaminant movement and distribution such as dispersivities, hydraulic conductivities and the effect of cutoff walls in controlling the spread of contaminant plume are studied. Also in this regard, the movement and spread of a contaminant at a landfill site in New Castle County, Delaware, is studied by comparing the simulated pattern of plume with the observed pattern. / Master of Science

Page generated in 0.1128 seconds