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Nuclear Science and Technology | Progress Report 197
22 ± 4 kBq•m to 39 ± 4 kBq•m . For the two Inorganic chemical characterization of
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monitoring stations assumed as contaminated sediment cores from Pantanal da Nhecolândia,
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locations, radon concentrations average were MS, dated by the Pb method
1.4 ± 0.4 kBq•m and 13 ± 9 kBq•m . The results
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have shown good agreement between the used Pantanal da Nhecolândia, geographically locat-
method and the conventional environmental ed in the state of Mato Grosso do Sul, is part
investigation techniques, for the majority of of the Brazilian Pantanal, and has its specific
the monitoring stations in different seasons. characteristics, one being the existence of sa-
Results obtained with CR39 detectors varied line lakes, commonly known as Salinas (Figure
over the exposure time due to the different 33). Therefore, to estimate a possible human
seasons. No relation was observed between influence, a study was initiated in Pantanal
radon activity concentrations and rain volume da Nhecolândia in 2010, where four sediment
accumulated over the different CR39 exposure cores were collected in Salinas A, 6, M, and V.
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times. The lowest Rn activity concentrations The elements As, Ba, Ca, Ce, Co, Cr, Cs, Eu, Fe,
occurred in “G” and “H” monitoring stations, Hf, K, La, Lu, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th,
also verified by gamma-ray spectrometry, that U, Yb, and Zn were determined using instru-
the low activities are not related to the activity mental neutron activation analysis (INAA), in
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concentration of its father Ra from the U the fine (silt + clay) and coarse (medium sand
decay chain, reinforcing the theory that radon + fine sand) fractions of the sediment. The
gas is retained in sites where NAPL contam- sedimentation rates and age of the sediments
ination is present. Results obtained during were determined using the Pb method. The
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environmental remediation proved that the grain size analysis and the water content of
methodology employed in this study was more the sediment samples were also determined
efficient than the conventional investigation to assist in the interpretation of the results.
techniques, especially for the “D” and “G” mon- The four sediment cores showed different sed-
itoring stations to the investigated site. imentation rates, which is probably related
to drought and flood periods. The grain size
analysis showed that the Salinas have a per-
centage of the fine fraction oscillating from
3.5% in Salina M to 70% in Salina A, which is
characteristic of this region. The results were
compared with the values of the Upper Con-
tinental Crust – UCC and the North American
Shale Composite – NASC, and some elements
showed values above these, including the el-
ements As, Hf, Rb and Sb, in the two fractions
of the sediment. These results of concentration
of the elements in the four Salinas suggest the
existence of natural deposits of these elements.
The results of concentration of the studied ele-
ments in the present work suggest that there
is no anthropogenic influence in the region.
To evaluate these concentration values the
Figure 33. Salina and vegetation in Pantanal da Nhecolândia, MS. enrichment factor – EF was calculated using
