INTEGRATION OF GEOPHYSICAL METHODS IN THE STUDY OF ACID DRAINAGE IN URANIUM MINING WASTE

ABSTRACT. Among the potential environmental impacts in mining activities, acid mine drainage (AMD) is a relevant problem caused by reactive minerals, such as sulfides, due to their exposure to the surface conditions. This is the context of contamination of a waste pile (BF-04) at Osamu Utsumi mine, closed in 1995 after years of physical and chemical processing of the uranium ore and currently under decommissioning plan. This study is based on the application of the combined geophysical methods of Electrical Resistivity and Induced Polarization and the analysis of previous geochemical data, aiming the evaluation of zones related to the generation of AMD and groundwater flux into the waste pile BF-04, containing sulfide minerals and uranium. The association of high resistivity and high chargeability zones is related to disseminated sulfide minerals in rock with silica cement. Infiltration of meteoric water through those zones induces the oxidation of sulfides, high sulfur concentration in groundwater followed by a drop in pH values, which results in a higher leaching capacity and solubility of ions and heavy metals. In addition, high chargeability zones (higher than 10 mV=V) represent portions of generation of AMD, while the low resistivity anomalies (under 70W:m) are related to preferential flow zones of the contaminated groundwater.Keywords: minning, sulfides, uranium, electrical resistivity, chargeability.RESUMO. Dentre os potenciais impactos ambientais em mineração, a drenagem ácida de mina (DAM) é um problema grande onde ocorrem minerais instáveis como os sulfetos, outrora isolados em subsuperfície. É neste contexto de contaminação do meio físico que está inserido uma pilha de rejeitos (BF-04) pertencente à mina de urânio Osamu Utsumi, cujas atividades de mineração, processamento físico e processamento químico foram encerradas em 1995, seguidas pela etapa de descomissionamento até os dias atuais. Neste estudo foram aplicados os métodos geofísicos da Eletrorressitividade e Polarização Induzida combinados com dados geoquímicos prévios, com o intuito de avaliar zonas de geração e fluxo de drenagem ácida de mina na pilha de rejeitos de mineração BF-04 com sulfetos e urânio. A combinação de zonas de alta resistividade e alta cargabilidade revela sulfetos disseminados em rochas com cimento silicático. A infiltração de águas meteóricas nestes locais induz a oxidação de sulfetos, liberação de enxofre nas águas subterrâneas seguida pela queda no pH, que resulta num efluente com alta capacidade de lixiviação e solubilidade de sais e metais. Neste sentido, zonas de alta cargabilidade (acima de 10 V=V) representam locais de geração de drenagem ácida de mina, enquanto que zonas de baixa resistividade (abaixo de 70 W:m) revelam zonas preferenciais de fluxo do efluente.Palavras-chave: mineração, sulfetos, urânio, resistividade, cargabilidade.

CONTROL OVER LUBRICATION OF CYLINDERS ON MARINE LOW SPEED DIESEL ENGINES

The article focuses on the problem of organizing control over oil supply to the cylinders of a marine diesel engines during slow speed operation. In the instructions for diesels with mechanical lubricators manufacturers strongly recommend to recalculate the actual specific oil consumption at share load and to reduce it to full operational load when evaluating oil consumption. The obtained specific oil consumption should be compared with the standard value, which was assigned for the full load regime. Manufacturers use different symbols for these parameters and different principles of oil supply regulation in their manuals. The variety of symbols and formulas makes it difficult to understand the technique, which is the reason why it is not applied on many vessels, as evidenced by the experience of certification of ship mechanics in the Maritime Qualification Commission of the port of Vladivostok. There have been proposed measures for wider application of the technique on ships, as it allows generalizing the experience of using oil on one-type engines in their operation on different types of ships with different load and practice to correct the recommendations about the cylinder oil dosage. Much attention is given to the features of the control organization over the lubrication of the cylinders on new generation ME S and G MK 8 type engines and later types with electronic control and regulation systems for continuous operation at super-low loads. When using a fuel with high sulfur concentration, these engines suffer from excessive wear of the cylinder bushings in their upper part due to acid corrosion because of hypernormal cooling of bushings. Therefore, the designers of diesel engines have developed special manuals on cylinder lubrication. There has been given the justification for applying the universal symbol qMR g/kW (h/kW) to indicate the initial rate of specific consumption of cylinder oil in relation to the full load of the marine low-rate diesels and the symbol qMR for “actual specific consumption reduced to a full load”. The details of oil dosage in the new generation S and G MK 8 type diesel engines are given, in which the effect of cold corrosion of bushes at low loads is manifested.

AVALIAÇÃO DA ALTERABILIDADE DAS ROCHAS DA FACHADA LATERAL DIREITA DO MOSTEIRO DE SÃO BENTO

ResumoO Centro da cidade do Rio de Janeiro revela importantes monumentos históricos construídos durante o período colonial em rochas ornamentais, principalmente utilizando blocos de gnaisse facoidal e de leptinito, que são rochas metamórficas características do Estado. Um exemplo desse tipo de construção é o Mosteiro de São Bento, cujas fachadas são compostas por estas rochas, que se encontram em processos de degradação. A deterioração pode ser decorrente da influência de diversos agentes de intemperismo, como a salinidade, poluição atmosférica e alta umidade, fatores resultantes da localização deste imóvel, na zona portuária do Rio. Atualmente o Mosteiro está passando por uma restauração interna e externa, com o intuito de preservar este importante patrimônio. O presente trabalho aborda a fachada lateral direita e apresenta discussões sobre os processos de intemperismo e as alterações encontradas nos materiais rochosos. Por meio da caracterização química (FRX) foi observada uma alta concentração de enxofre, e através da avaliação mineralógica (DRX) foi constatado o aparecimento da gipsita. Sendo assim, tais resultados apontam um processo de alteração da rocha.Palavras Chave: Mosteiro de São Bento, degradação, intemperismoAbstractEVALUATION AND ALTERABILITY OF RIGHT LATERAL ROCK FACADE FROM SÃO BENTO MONASTERY. The Center of Rio de Janeiro reveals important historical monuments built with ornamental stones during the colonial period. The mainly stones used on their architectural structure were the facoidal gneiss and leptinite, both are metamorphic types and belong to the local geologic context of the city’s landscape. A good exemple of the use of those stones on ancient building is visible on Monastery of St. Benedict, which facades are composed by leptinite and facoidal gneiss. Due to many factors and the time of exposure a lot of degradation process occurs on those stones leading to their decay. The decay of those stones may have a strong influence of various chemical and physical weathering agents, such as salinity, air pollution and high moisture. Those factors can result from for example, the city’s tropical climate and the location of this property nearby the port area in downtown of Rio de Janeiro. Today, the monastery is undergoing an internal and external restoration and in order to better understand the weathering processes and changes found on its stones materi.als, this work focus on the study of the right facade and presents some discussions about the results that were found through the chemical compounds (XRF), such as high sulfur concentration and mineralogical evaluation (XRD) which had showed the presence of gypsum. These technical results associated to the weather and the surroundings of this monument indicates the process of alteration in the stonesKeywords: Monastery of S Bento, alterability of dimension stone, conservation

GEOCHEMICAL CHARACTERIZATION OF SATELLITE HYDROCARBON FORMATIONS IN PRINOS-KAVALA BASIN (NORTH GREECE)

Conditions favoring generation, migration and trapping of hydrocarbons generated economically significant reservoirs in Prinos-Kavala Basin. Prinos oil field and South Kavala gas field are characteristic examples. The submarine fan packed the basin during Upper Miocene. The hydrocarbons were accumulated in turbidites, deposited in a strongly reducing environment, with high sulfur concentration. Evaporates are also deposited before and after the turbidite system. In this study, which is part of a doctorate thesis, extracts retrieved from cored samples of two satellite formations in Prinos-Kavala Basin, Epsilon and Kalirahi, selected at the "Prinos equivalent" formations, have been analyzed, using geochemical methods, and found to exhibit common compositional characteristics. The analysis of biomarkers indicates that the bitumens are immature and non-biodegraded, while their origin is considered mainly algal, with minor terrestrial contribution. Variations on characteristic geochemical ratios between formations, such as Pr/Ph, Ts/Tm, oleanane/hopane and steranes index, are attributed to differences on the type of organic mater input, or the depositional setting of sediments. The identification of the organic matter type, the hydrocarbons generation, migration paths and traps of each structure within the basin is vital for the evaluation of a reliable model of the basin and further hydrocarbon exploration in North Aegean basins

Electron Spin Resonance of Hydrogenated Amorphous Silicon Alloyed with Sulfur

ABSTRACTElectron spin resonance (ESR) and light-induced electron spin resonance (LESR) measurements were performed on sulfur-doped hydrogenated amorphous silicon (a-SiS:H). At low S doping levels (H2S/SiH4 ≤ 10−3 in gas phase), the ESR and LESR line shapes are similar to those observed in undoped a-Si:H. The dark spin density generally increases with S doping and reaches 5×1016 cm−3 at H2S/SiH4 ≈ 10−3. On the other hand, at high S concentration, the dark spin density increases significantly with S concentration. The ESR and LESR line shapes become identical and asymmetric, a fact that implies the ESR and LESR signals result from the same kind of ESR center. Since S doping is very inefficient, the ESR signals probably are due to defects instead of trapped carriers in band tails. The asymmetry of the ESR and LESR line shapes at high sulfur concentration may result from either more than one type of defect or an asymmetry in the g tensor of a single defect. The photo-excitation of H-passivated, S-related defects could also contribute to the LESR.