Major and trace elements in sediments from Viração Logoon, Fernando de Noronha Archipelago, Brazil
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2004
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INTERNATIONAL SYMPOSIUM ENVIRONMENTAL GEOCHEMISTRY IN TROPICAL COUNTRIES, 4th
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Resumo
Fernando de Noronha is an isolated group of 21 volcanic islands and
located in the South Equatorial Atlantic, approximately 545 km from
Recife, PE, Brazil. This archipelago is a protected and isolated habitat
with restrict access. Viração Lagoon, a small lake located at Fernando
de Noronha Island, 20 meters above the sea level, is a pristine lake
located in the main island. The local drainage is restricted and
ephemeral, and no connection with the general insular drainage is observed. Two sediment cores (27 and 41 cm-Iong) were extracted in
this lagoon in 2000, in order to determine the chemical and
mineralogical composition of the sediments. The sediments are made
up of smectite, and Fe and Ti oxides. Trace elements As, Ba , Br, Co, Cr,
Cs, Rb, Sb , Sc, To , Th , U, Zn and rare earths (Ce, Eu , La , Lu, Nd, Sm, Tb
and Vb) were determined by instrumental neutron activation analysis
(lNAA). All samples, previously dried at 60oC, were passed through a
0.065 mm sieve. The cores were sliced at every two centimeters. For the
multi elemental analyses approximately 200 mg of sediment (duplicate
samples) and about 150 mg of reference material and synthetic
standards were accurately weighted and sealed in pre-cleaned
double polyethylene bags, for irradiation ., Single and multielement
synthetic standards were prepared by pipetting convenient aliquots of
standard solutions (SPEX CERTIPREP) onto small sheets of Whatman no
41 filter paper. Sediment samples, reference material and synthetic
standards were irradiated for 16 hours, under a thermal neutron flux of
1012 n cm-1 s- l in the IEA-R 1 nuclear reactor at Instituto de Pesquisas
Energeticas e Nucleares fi IPEN. Two series of counting were made: the
first after one-week decay and the second, after 15-20 days. The
counting time was 2 hours for each sample and reference material,
and 30 min for each synthetic standard. Gamma spectrometry was
performed using a Canberra gamma X hyperpure Ge detector and
associated electronics, with' a resolution of 0.88 keV and 1.90 keV for
57Co and 60Co, respectively. The validation of this methodology was
performed by means of Buffalo River Sediment SRM 2704 (NISD , Soil-7
(lAEA) and BEN (Basalt-IWG-GID reference material analysis. The major
elements were determined by XRF technique at IG/USP and the
validation was carried out by means of JB-1 a and JG-1 a (Geological
Survey of Japan) reference materials analysis. Their concentrations are
similar to those reported for NASC (North American Shale Composite), except for Ba, REE , Cr, Zr and Zn , with higher concentrations.
Enrichment factors for major and trace elements were calculated ,
using the composition of the surrounding rock (source of the sediments)
as a normalizer. Results show that Cr, U, Th, Rb, and Zn are enriched
and Hf, Co, Eu and Tb are depleted relative to the rock.
Como referenciar
FAVARO, D.I.T.; OLIVEIRA, S.M.B.; DAMATTO, S.R.; MENOR, E.A.; MORAES, A.S.; MAZZILLI, B.P. Major and trace elements in sediments from Viração Logoon, Fernando de Noronha Archipelago, Brazil. In: INTERNATIONAL SYMPOSIUM ENVIRONMENTAL GEOCHEMISTRY IN TROPICAL COUNTRIES, 4th, 25-29 Oct., 2004, 2004, Buzios, RJ. Abstract... p. 388-390. Disponível em: http://repositorio.ipen.br/handle/123456789/22555. Acesso em: 24 Mar 2026.
Esta referência é gerada automaticamente de acordo com as normas do estilo IPEN/SP (ABNT NBR 6023) e recomenda-se uma verificação final e ajustes caso necessário.