HR: 0800h
AN: H51A-02 [Abstracts]
TI: Occurrence of 226Ra in Ground Waters From a Granitic Aquifer at the City of Itatiba, Eastern Sao Paulo State, Brazil
AU: Santos, R N
EM: rosanans@iag.usp.br
AF: Department of Physics, Catholic University of Sao Paulo, Rua Marques de Paranagua, 111,
Sao Paulo, SP 01303-050, Brazil
AU: Santos, R N
EM: rosanans@iag.usp.br
AF: Department of Geophysics, University of Sao Paulo, Rua do Matao, 1226, Cidade
Universitaria, Butantan, Sao Paulo, SP 05508-090, Brazil
AU: Lucas, F d
EM: lucas@iag.usp.br
AF: Department of Physics, Catholic University of Sao Paulo, Rua Marques de Paranagua, 111,
Sao Paulo, SP 01303-050, Brazil
AU: * Brenha Ribeiro, F
EM: brenha@iag.usp.br
AF: Department of Physics, Catholic University of Sao Paulo, Rua Marques de Paranagua, 111,
Sao Paulo, SP 01303-050, Brazil
AB:
Among the naturally occurring radionuclides, 226Ra play an important role in establishing the ground water
radioactivity level. In this work, it is presented the 226Ra activity concentration measured in ground water drawn
from a granitic fractured aquifer at the Ribeira Folded Belt, eastern Sao Paulo State, Brazil.
The ground water samples were collected twice in the same well in June, 2nd and July 6th, 2005. After discarding
about fifteen minutes of continuous well pumping, ground waters samples are collected in 50 L polyethylene
containers, previously conditioned with nitric acid, 0.03 mol/L. The water temperature, pH and Eh are measured at
the sampling site. The water samples were preserved by addition of 2.0 mL of concentrated nitric acid to lower its
pH to less than 2.
In laboratory, three 20 L aliquots were selected for independent radiochemical processing.
Radium is precipitated from water samples in the form of barium-radium sulfate. The barium-radium precipitate
is filtered and dried over the filter paper. The radium containing filter is then sealed with an adhesive plastic film
and hermetically closed in a rigid polystyrene sample holder. The sample is left at rest for at least 40 days to
allow the short lived daughters (222Rn, 214Pb and 214Bi) reach secular radioactive equilibrium with 226Ra. The
radium activity is then indirectly measured by gamma-ray spectrometry through the full absorption peaks from the
214Pb and 214Bi.
The gamma-ray spectrometry activity measurements are made by comparison with 226Ra standards. These
standards were prepared by the radium precipitation from secondary standard solutions obtained by dilution of a
(19.52 +/- 0.72) Bq/g 226Ra solution. The precipitate standards were prepared following the procedure adopted
for the ground water samples. The observed 226Ra activity concentration were (43 +/- 2) mBq/L and (46 +/- 3)
mBq/L, for the first and second water sampling campaigns, respectively.
DE: 0478 Pollution: urban, regional and global (0345, 4251)
DE: 0496 Water quality
DE: 1040 Radiogenic isotope geochemistry
DE: 1831 Groundwater quality
DE: 1880 Water management (6334)
SC: Hydrology [H]
MN: 2007 Joint Assembly