Geochemical mapping of potentially hazardous elements in surface waters and stream sediments of the Quadrilátero Ferrífero, Brazil.
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2018
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Resumo
Geochemical mapping and the determination of baseline concentrations of
potentially hazardous elements in the environment receive increasing
attention. The need to know regional geochemical background data as well as
the spatial allocation of areas with anomalous element concentrations and
chances to identify their major sources motivate the interest. Here, results
from a geochemical mapping exercise and derived related baseline values are
presented. 541 stream sediment and surface waters samples have been
collected across the Iron Quadrangle (IQ), Brazil, with a density of 1 sample
per 13 km2. Geochemical maps were compiled using the inverse distance
weighted (lDW) interpolation method. “Normal” background concentrations
were distinguished from anomalies with the separation-by-concentrationrange
technique, where positive anomalies were defined by the “boxplot”
Upper Inner Fence (UIF) rule. The results demonstrate that more than 70% of
the IQ area shows geogenic background concentration ranges for the elements
studied. About 20% of the area represent positive anomalies, likely related to
both near surface rock types and to human interference. Distinct
anthropogenic anomalies, notably from mining activities are identified in 5–
10% of all samples. This first sampling in the IQ allows delineation of the role of lithology on the elemental composition of stream sediments, and to
establish baseline 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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Geoquímica ambiental, Valores de referência, Background values, Iron Quadrangle, Environmental geochemistry
Citação
COSTA, R. de V. F. da et al. Geochemical mapping of potentially hazardous elements in surface waters and stream sediments of the Quadrilátero Ferrífero, Brazil. Geochimica Brasiliensis, Rio de Janeiro, v. 32, p. 243-267, 2018. Disponível em: <http://www.geobrasiliensis.org.br/geobrasiliensis/article/view/553>. Acesso em: 11 fev. 2019.