Navegando por Autor "OLIVEIRA, Simone Pereira de"

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Acesso aberto (Open Access)
Aplicação da composição isotópica de multielementos no monitoramento ambiental de área circunvizinha à barragem de rejeito: o caso da mina de cobre da Serra do Sossego, Canaã dos Carajás – PA
(Universidade Federal do Pará, 2017-06-09) OLIVEIRA, Simone Pereira de; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
Tailings dams from ore mining activities are relevant compartment for environmental monitoring because the dam can present undesirable forms of water outlets such as infiltration. The present thesis proposed multielement isotope study in order to evaluate the use of the isotopic composition of oxygen, hydrogen, strontium and lead as a tool for the environmental monitoring of groundwater vulnerable to the tailings dam. This research was conducted in the area of the Serra of Sossego copper mine and, in addition to the isotope study, the hydrochemical characterization of groundwater and surface water was caried out. Besides, the direct reading of the isotopic composition of lead (without chemical treatment of the water sample) was applied for the first time, using multicollector inductively coupled plasma mass spectrometry, in the laboratory Para-Iso. The hydrochemical characterization of groundwater in the Serra do Sossego mine area showed that it is moderately acid (pH ~ 6). Only the AP15 and PS32 wells, under the influence of the drainage of the mixed pile (ore waste + sterile), presented high electrical conductivity (599 μS / cm2 and 694 μS / cm2) and the higher sulfate content (1.82 to 6.57 Meq/L). In general, iron (29.7 mg/L), manganese (69.7 mg/L) and copper (24.9 mg/L) present the highest metal content in the groundwter. In terms of the isotope studies, the groundwater of PS17, PS04, AP15 and PS32 wells and the water of the Dam present the least radiogenic lead isotopic composition. The water sampled in the AP15 and PS32 wells would be representative of the lead isotope signature of groundwater in the mine area (206Pb/207Pb = 1.1481 to 1.1663) and, probably, is indicative of the lead isotope composition of the meteroric water. The lead isotope composition of the groundwater of the wells PS04 (206Pb/207Pb = 1.1784-1.1850) and PS17 (206Pb/207Pb = 1.2100 to 1.2160) may indicate a small contribution of the rocks of the region (206Pb/207Pb > 1.6807). In turn, the lead isotope signature of water of the Dam (206Pb/207Pb = 1.2279) suggests, as expected, a slightly more pronounced contribution of the ore and the rocks. On the other hand, the lead isotopes of the water sampled in the wells MNA23 and PS06 show a more radiogenic signature (206Pb/207Pb = 1.6741 to 1.9196), which is similar to those of the chalcopyrite and the diabase of the Sequeirinho open pit, revealing a more significant contribution of the ore and rocks. As the lead isotope composition of water from the dam is different from that of the groundwater, it can be used for the environmental monitoring of the influence of the water from the dam in groundwater in the Serra of Sossego mine area. In those wells with less radiogenic lead isotope signature, a possible contribution of the water from the dam would result in a more radiogenic lead isotope composition in the groundwater. Conversely, in those wells with more radiogenic lead isotope signature, a contribution of the water dam for the groundwater would decrease the values of the measured lead isotope ratios. On the other hand, the application of the sulfur isotopes for environmental monitoring presented some limitation in the study area, due to the lack of contrast of the sulfur isotope composition among the sulfides of the Sossego deposit (δ 34S ~ 2-7 ‰), the water from the dam (δ 34S ~ 2 ‰), and the drainage of the mixed pile (δ 34S ~ 2‰). This prevents the recognition of a possible contribution of the tailings dam to groundwater. Mixing models using the 87Sr/86Sr ratio as a function of the strontium concentration and δ 18O values, also showed some limitations, since there is no contrast between the values of the 87Sr/86Sr ratio of the water from the dam (0. 7458 to 0.7539) and the rocks of the mine area (granite ~ 0.7474). Such similarity, in principle, would not allow identifying the contribution of the water from the dam. However, since groundwater generally exhibits less radiogenic values of the 87Sr/86Sr ratio (0.7161 to 0.7283) and well below the dam values, the strontium isotopic composition can be used for environmental monitoring of groundwater. Hydrogen and oxygen isotope data revealed that, in the rainy season, the groundwater presented values of δ 18O and δ D varying from -2.74 to -7.17‰ and from -15.6 to -46.0‰, respectively. In turn, an enrichment of 18O and D, with values of δ 18O between -1.67 and -7.29 ‰ and of δ D between -0.23 and -46.1 ‰, is observed in the dry season. Hydrogen and oxygen isotope composition of the water from the dam (δ 18O from 1.24 to 2.79 ‰ and δ D from 1.40 to 7.0 ‰) is very different from those of the groundwater and of the drainage of the pile. A mixing model performed with oxygen and hydrogen isotopes showed that these elements are the ones that best respond as indicators of the contribution of the waters from the dam to groundwater. The application of this model revealed no influence of the water from the dam on the groundwater during the period of this study. The results obtained in this multielement isotopic study suggest that the environmental monitoring of the groundwater of the Serra do Sossego mine to investigate the possible contribution of the water from the dam, can be done more efficiently with the oxygen and hydrogen isotopes. The isotopic compositions of lead and strontium can also be used for monitoring the groundwater, but this has to be done more systematically due to the small contrast between the isotopic composition of these elements in the dam water and in the groundwater. Finally, the isotopic composition of sulfur is the one that would contribute least to the environmental monitoring of the groundwater of the study area.
Acesso aberto (Open Access)
Estudo da composição isotópica de Pb em organismo bentônicos, poliquetas (Namalycastis abiuma) e oligoquetas, da Baía do Guajará e rio Guamá
(Universidade Federal do Pará, 2009-06-24) OLIVEIRA, Simone Pereira de; ROSA FILHO, José Souto de; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
In Guajará bay (Terminal Petroliferous do Miramar and mouth of Una Canal) and in Guamá river (mouth of Tucunduba creek), three samples of bottom sediments, three of polichaetes (Namalycastis abiuma) and five samples of oligochaetes (Tubificidae) were collected. In the biological samples lead (Pb) concentration and isotope composition were determined, whereas in the sediments samples only the Pb isotope composition was. Pb content was quantified in two representative samples of oligochaetes and polichaetes. Concentrations of 5 mg.kg-1 and 3 mg.kg-1, was obtained for these organisms, respectively. Pb concentration determined in oligochaetes was equivalent to 13% of the lead’s level of the bottom sediments of its habitat (38 mg kg-1). In spite of the Pb content of the bottom sediments of Guajará bay may suggest moderate pollution, this proportion can be considered high when it is compared with the percentual relation of 1,7% of oligochaetes and sediments of very polluted environments (p. ex. botton sediment lakes of India with lead content reaching 2.260 mg.kg-1 and oligochaetes with until 23 mg.kg-1). This result suggests that, proportionally, oligchaetes may assimilate greater amount of lead of its habitat in less polluted environments. However, the lead level in oligochaetes compared with the lead level in sediments of its habitat, showed a positive correlation, and it indicates that oligochaetes can be used as a bioindicator. The polychaetes (Namalycastis abiuma), did not show a trend that indicates any type of connection or correlation between lead level in organisms and lead level in sediments. This result indicates that polichaetes cannot be used as bioindicator of the enrichment of lead (and metals) in its habitat. Lead isotope composition of the bottom sediments in Guamá river, gave the value of 1,193 for the 206Pb/207Pb ratio which is different to the suggested a value of 1,194 for the bottom sediment of the Guamá river, and interpreted as the natural value (geogenic). This indicates a anthropogenic origin of lead in Guamá river in the sampled point (mouth of the Tucunduba creek). In Guajará bay, the sample of sediment in the mouth of the Una Canal, presented a value of 1,167 for the reason 206Pb/207Pb. In previous works, this value had been suggested as indicative of lead of anthropogenic origin. This value of 206Pb/207Pb ratio shows that the Una canal is contributing to lead level in the sediments of the Guajará bay, through of discharge of domestic effluent and solid residues. Finally, in a sediment sample collected in the Terminal Petroliferous do Miramar, also in the Guajará bay, the value of the 206Pb/207Pb ratio was 1,188. This value is lower than that suggested as natural value of the 206Pb/207Pb ratio in the bottom sediments of the Metropolitan Region of Belém, which is of 1,200. This lower value can be related to activities of the Terminal Petroliferous do Miramar. The products originated in oil have an important potential of heavy metal (including lead) dissemination to environment. In order to compare the lead isotope signature of the organisms with that of the sediments the values of the isotopic ratio 206Pb/207Pb of the organisms were divided by the respective values of thIs ratio in the sediments. If the resultant quotient, represented as R, had a value of 1± 0,004 (0,996 ≤ R ≤ 1,004), it was considered as indicative that the lead isotope signature of the organisms reflected the signature of the bottom sediments of its habitat. The values of R in 75% of the biological samples were within the interval (0,997 ≤ R ≤ 1,001). The other 25% that remain outside of this tolerance interval, correspond to the two samples of oligoquetas collected in the mouth of Una Canal. Thus, the three samples of polichaetes collected next to the Terminal Petroliferous do Miramar, and the three samples of oligoquetas collected in the Guamá river next to the mouth of Tucunduba creek show values of R within the tolerance interval. This suggest that the polichaetes (Namalycastis abiuma) and oligochaetes reflected the lead signature isotope of the environment in which they are inserted, and are good bioindicators of lead isotope composition in its habitat.