TITLE:
Pb Isotopes Study in Recent Sediments from Paraty Bay (Rio de Janeiro, Brazil): Antropogenic Versus Oceanic Signatures
AUTHORS:
M. C. Geraldes, S. D. Pereira, H. H. Villena, F. W. e Herms
KEYWORDS:
Pb Isotopes, Paraty Bay, Metal Pollutants
JOURNAL NAME:
International Journal of Geosciences,
Vol.6 No.7,
July
16,
2015
ABSTRACT: We carried out Pb isotopes
studies in sediments fromParatyBaylocated in the SE area of theRio de
JaneiroStateto discriminate the signature of metal contamination from domestic
sewage, industries, shipyards and geogenic sources. The studied samples have
been chosen in two sectors of the Bay, including the Paraty area
andJuatingaBay. Sample preparation procedures included: 1) drying and
granulometric separations (200 mesh); 2) weighting; 3) complete dissolution and
4) Pb isotope analysis obtained by MC-ICP-MS (ratios 208Pb/204Pb,207Pb/204Pb, 206Pb/204Pb).
Preliminary results when plotted in the 207Pb/204Pbversus 208Pb/204Pb and 207Pb/206Pb versus 206Pb/204Pb
diagrams showed three groups of signatures. The first group (samples PY-01,
PY-03 PY-106 and PY-127) presented 207Pb/206Pb
values in the range from 1.191 to 1.209. The isotope values may be interpreted
as contribution of a pollutant sources of Pb not yet identified. The second
group (PY-11, PY-13, PY-21, PY-22, PY-46, PY-51, PY-109 and PY-111) showed 207Pb/206Pb
values in the range from 1.188 to 1.222. The last group (samples PY-123 and
PY-135) presented higher 207Pb/ 206Pb values from 1.321 to
1.322 and probably represented oceanic signature. The Pb isotope data of the
second group may be interpreted as the result of oceanic water and pollutant
sources mixture from the continent. According to the literature the anomalous Pb
signature is similar to anthropogenic source. The Pb isotope results here
reported are coherent with the reported data from the continent area. We may
conclude that significant isotopic differences in Pb signatures are consequence
of anthropogenic Pb isotope signature. In this way, Pb isotope is an important
tool to trace the changing sources of pollutant Pb (and other metals) in ocean
environment.