Page 202 - 00. Complete Version - Progress Report IPEN 2014-2016

202 Nuclear Science and Technology | Progress Report

centrations average for the eight monitoring Inorganic chemical characterization of
stations at non-contaminated locations varied sediment cores from Pantanal da Nhecolândia,
210
from 22 ± 4 kBq·m3 to 39 ± 4 kBq·m3. For the MS, dated by the Pb method
two monitoring stations assumed as contam-
inated locations, radon concentrations aver- Pantanal da Nhecolândia, geographically locat-
age were 1.4 ± 0.4 kBq·m3 and 13 ± 9 kBq·m3. ed in the state of Mato Grosso do Sul, is part
The results have shown good agreement be- of the Brazilian Pantanal, and has its specific
tween the used method and the convention- characteristics, one being the existence of sa-
al environmental investigation techniques, line lakes, commonly known as Salinas. There-
for the majority of the monitoring stations in fore, to estimate a possible human influence, a
different seasons. Results obtained with CR39 study was initiated in Pantanal da Nhecolândia
detectors varied over the exposure time due in 2010, where four sediment cores were col-
to the different seasons. No relation was ob- lected in Salinas A, 6, M, and V. The elements
served between radon activity concentrations As, Ba, Ca, Ce, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Na,
and rain volume accumulated over the differ- Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th, U, Yb, and Zn were
ent CR39 exposure times. The lowest 222Rn determined using instrumental neutron acti-
activity concentrations occurred in “G” and vation analysis (INAA), in the fine (silt + clay)
“H” monitoring stations, also verified by gam- and coarse (medium sand + fine sand) fractions
ma-ray spectrometry, that the low activities of the sediment. The sedimentation rates and
are not related to the activity concentration of age of the sediments were determined using
210
238
its father Ra from the U decay chain, rein- the Pb method. The grain size analysis and
226
forcing the theory that radon gas is retained in the water content of the sediment samples
sites where NAPL contamination is present. Re- were also determined to assist in the interpre-
sults obtained during environmental remedi- tation of the results. The four sediment cores
ation proved that the methodology employed showed different sedimentation rates, which
in this study was more efficient than the con- is probably related to drought and flood peri-
ventional investigation techniques, especially ods. The grain size analysis showed that the
for the “D” and “G” monitoring stations to the Salinas have a percentage of the fine fraction
investigated site. oscillating from 3.5% in Salina M to 70% in Sali-
na A, which is characteristic of this region. The
results were compared with the values of the
Upper Continental Crust – UCC and the North
American Shale Composite – NASC, and some
elements showed values above these, includ-
ing the elements As, Hf, Rb and Sb, in the two
fractions of the sediment. These results of con-
centration of the elements in the four Salinas
suggest the existence of natural deposits of
these elements. The results of concentration
of the studied elements in the present work
suggest that there is no anthropogenic influ-
ence in the region. To evaluate these concentra-
tion values the enrichment factor – EF was cal-
Figure 4. Salina and vegetation in Pantanal da Nhecolândia, MS. culated using reference values from the UCC,

Instituto de Pesquisas Energéticas e Nucleares