NORM levels in Spanish pit lakes and their impact on
neighboring environments
Guillermo Manjón*, José Antonio Galván, Juan Mantero, Inmaculada Díaz, Rafael García-Tenorio
Grupo de Física Nuclear Aplicada. Universidad de Sevilla, Spain
Centro Nacional de Aceleradores, Sevilla, Spain
1. INTRODUCTION
The
Iberian Pyrite Belt (IPB) is a part of
the South Zone of the Hercynian Iberian
Massif (SW of Iberian Peninsula), being
pyrite (FeS2) the main mineral associated
to this volcano-sedimentary complex. The
intensive mining activities in the area,
which started in the Roman Empire, have
generated mine pits where underground
and/or rainwater are stored.
These
Pit lakes in former mines located in the IPB have been studied in this work.
stored waters have produced
oxidation of pyrite and, consequently, the
pH of pit water has become acid (pH
In the Figure pit lake of San Telmo mine
nowadays.
around 2), causing the dissolution of
metals and natural radionuclides.
Nowadays new mining projects are being
implemented in this zone.
The main objective of this work is to show
and discuss the levels found for different
natural radionuclides (mainly uranium
isotopes and daughters via α-sectrometry)
in water samples and sediments collected
from several mine pit lakes located in the
south-west of Spain.
2. EXPERIMENTAL
water samples were acidulated just after they were collected and stored
100.00
µg/ℓ
Alfa-spectrometry
ICP-MS
in plastic bottles. Once in the laboratory, a 1 liter aliquot was separated
for analysis.
10.00
The
first step of analysis was the addition of well known activity of
tracers (232U, 229Th and 209Po) to obtain the radiochemical yield of the
process. Actinides and polonium separation was obtained by coprecipitation with iron hydroxide.
1.00
0.10
1
2
3
4
5
6
7
8
9
10
In the case of water samples, firstly 10 mg of Fe
11
3+
ICP-MS technic has been applied to the determination of
were added into the
aliquot and pH is adjusted to 8-9 with ammonia. The precipitate is
separated by centrifugation. Once dried, the precipitate is dissolved with
HNO3 8M.
heavy metal concentrations. In this figure U concentrations
determined by ICP-MS and α-spectrometry are compared.
Sediment and sulfate efflorescent salts samples pretreatment was an
For both types of samples, U-isotopes, Th-isotopes and polonium were
separated by solvent extraction with TBP. Alternatively a UTEVA
chromatographic resin was used for isotope separation.
Radioactivity sources were obtained by autodeposition on a silver disc,
in the case of polonium, or by electrodeposition on stainless steel disc, in
the case of uranium or thorium.
Radioisotope
activity was determined by alpha-spectrometry using
Alpha Analyst with PIPS detectors.
Gamma-ray
spectrometry was made using two detectors (Xtra and
REGe) with a typical electronic associated. Spectra treatment was made
using a Genie 2000 software.
atmospheric digestion using aqua regia, H2O2 and HNO3. Actinides and
3. SAMPLING
Mine San
Telmo
polonium were co-precipitated with iron hydroxide.
5. RESULTS: IMPACT ON NEIGHBORING ENVIRONMENT
Mine
Confesionarios
4.1
Mine San
Miguel
Mine
Concepción
b
Mine Esperanza
7
Mine La Zarza
a
6
89
1 Mine El Soldado
3 2 Mine La Poderosa
4
5 10
Odiel River
Odiel River (natural)
Odiel River
AMD
11
Agrio Creek
Mines at Ríotinto
Mine Tinto Santa
Rosa
Villar Creek
Mining
wastes
Mine Sotiel
Map where have been remarked the sites of sampling along Odiel River. Pit lakes sampled in 2012 and surface water
sampled in 2013. Samples a and b were sampled in 2009.
CODE
a
b
1
2
3
4
5
6
7
CODE
8
9
10
11
SITE
NOT CONTAMINATED
NOT CONTAMINATED
NOT CONTAMINATED
BEFORE AMD LA ESPERANZA
AFTER AMD LA ESPERANZA
BEFORE AMD PALOMINO
AFTER AMD PALOMINO
BEFORE AMD AGRIO
AFTER AMD AGRIO
SITE
MINE LA ESPERANZA
MINE LA ESPERANZA
PALOMINO CREEK
AGRIO CREEK
Concentration of
KIND OF SAMPLE
ODIEL RIVER
ODIEL RIVER
ODIEL RIVER
ODIEL RIVER
ODIEL RIVER
ODIEL RIVER
ODIEL RIVER
ODIEL RIVER
ODIEL RIVER
KIND OF SAMPLE
AMD
RECYCLING POOL
AMD
AMD
238U
(mBq/ℓ)
2,1 ± 0,2
1,8 ± 0,2
3,7 ± 0,7
4 ± 1
6 ± 1
4 ± 1
5 ± 1
4,1 ± 0,2
133 ± 10
238U (mBq/ℓ)
102 ± 5
258 ± 6
152 ± 8
1117 ± 29
234U/238U
1,41
1,42
1,24
1,75
1,50
2,25
1,68
1,85
1,55
± 0,18
± 0,17
± 0,32
± 0,50
± 0,30
± 0,75
± 0,38
± 0,12
± 0,15
234U/238U
2,14 ± 0,14
1,26 ± 0,04
1,58 ± 0,11
1,54 ± 0,06
238U
in surface water (Odiel River, tributaries and AMD’s). 210Po activity concentration was also
measured and levels can be considered not affected by mining activities. AMD means “Acid Mining Drainage”.
4. RESULTS: PIT LAKES
Pit lake water
Pit lake sediments
238U
MINES
CONCEPCIÓN
234U/238U
MINES
238U
234U/238U
14 ± 3
mBq/ℓ
2,79 ± 0,70
CONCEPCIÓN
5,55 ± 0,77 Bq/kg
2,59 ± 0,43
CONFESIONARIOS
247 ± 18
mBq/ℓ
4,48 ± 0,37
CONFESIONARIOS
0,74 ± 0,14 Bq/kg
4,62 ± 0,95
SAN TELMO
219 ± 11
mBq/ℓ
2,28 ± 0,14
SAN TELMO
4,95 ± 0,3
Bq/kg
2,22 ± 0,16
1094 ± 20
mBq/ℓ
1,60 ± 0,04
LA ZARZA
5,1 ± 0,56 Bq/kg
1,90 ± 0,26
LA ZARZA
Results of activity concentration of U-isotopes and
234U/238U
activity ratio in pit lake water collected in
2012 in former mining facilities.
Results
of activity concentration in pit lake
sediments collected in 2012 in former mining
facilities. Measured by α-spectrometry.
Pit lake sulfate efflorescent salts
MINES
234U
230Th
210Po
232Th
(mBq/ℓ)
(mBq/ℓ )
(mBq/ℓ)
(mBq/ℓ)
MINES
CONCEPCIÓN
39 ± 5
14 ± 3
< 0.5
18 ± 3
CONFESIONARIOS
1100 ± 43
133 ± 8
13± 1
57 ± 4
SAN TELMO
500 ± 17
171 ± 10
<6
39 ± 6
LA ZARZA
1750 ± 30
390 ± 20
33 ± 4
122 ± 12
CONCEPCIÓN
238U
234U/238U
17,53 ± 1,22 Bq/kg
1,97 ± 0,17
6,08 ± 0,43 Bq/kg
4,63 ± 0,33
SAN TELMO
14,58 ± 0,15 Bq/kg
3,16 ± 0,04
LA ZARZA
13,58 ± 0,79 Bq/kg
1,59 ± 0,09
CONFESIONARIOS
Concentration of most abundant heavy metals in surface waters determined by ICP-MS. The number of site
corresponds to Table and Map.
6. CONCLUSIONS
Former mining facilities have been studied and levels of natural radionuclides (U-isotopes, Th-isotopes and
210Po)
have been determined. Water, sediment and sulfate efflorescent salts samples were analyzed in this work. The
levels of U-isotopes in water have a wide range depending on the facility. However the activity concentrations in
sediment s are similar in three of studied facilities (about 5 Bq/kg). Acid pH of pit lake water causes the mobility of
actinides from sediment to water.
Surface waters (the Odiel River, its tributaries and low-flow AMD’s) have been also studied. In these cases, only Uisotopes show a clear radioactive impact of facilities on the neighboring environment.
Results of activity concentration of Th-isotopes and
Results of activity concentration in pit lake sulfate
Heavy metal concentrations have been determined by ICP-MS in water samples. A same pattern, in the case of Fe,
210Po
efflorescent salts (FeSO4·7H2O) collected in 2012 in
former mining facilities. Measured by α-spectrometry.
Cu, Zn, U and Th, with low concentrations in the Odiel River and higher concentrations in AMD’s, has been clearly
observed.
in pit lake water collected in 2012 in former
mining facilities.
*Author for correspondence: Guillermo Manjón. Universidad de Sevilla. ETS Arquitectura. Departamento de Física Aplicada 2. Av. Reina Mercedes 2. 41080 Sevilla, Spain. E-mail: manjon@us.es