Iron Quadrangle stream sediments, Brazil : geochemical maps and reference values.
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2015
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Resumo
Geochemical mapping and the determination of
reference values receive increasing attention. The need to
know regional geochemical background data as well as the
spatial allocation of areas with anomalous geochemical
concentrations and chances to identify their major sources
motivate the interest. Here, results from a high-density
geochemical mapping exercise and derived related reference
values are presented; 541 stream sediment samples
have been collected across the Iron Quadrangle (IQ),
Brazil, with a density of one sample per 13 km2. Geochemical
maps were compiled using the inverse distance
weighted interpolation method. ‘‘Normal’’ concentrations
were distinguished from anomalies with the separation-byconcentration-
range technique, where positive anomalies
are defined by the ‘‘boxplot’’ Upper Inner Fence (UIF) rule.
More than 70 % of the IQ show exclusively geogenic
concentration ranges for the elements studied. About 20 %
represent positive anomalies, likely related to both near
surface rock types and to human interference. Distinct
anthropogenic anomalies, notably from mining activities
explain 5–10 % of all samples. This first high-density
sampling in the IQ allows delineating the role of lithology
on the elemental composition of stream sediments, and to
establish reference values for the main river basins—thus
pinpointing localities, cities and fluvial basins that are exposed
to environmental risks and need to be protected.
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Palavras-chave
Geochemical background, Reference values, High-density geochemical mapping, Minas Gerais
Citação
VICQ, R. de. et al. Iron Quadrangle stream sediments, Brazil: geochemical maps and reference values. Environmental Earth Sciences, v. 74, p. 4407–4417, 2015. Disponível em: <https://link.springer.com/article/10.1007/s12665-015-4508-2>. Acesso em: 20 de jun. 2017.