56
R. Ferrara
2.S
Mercury in the Sediment
In the years 1974-1975, the ORNL measured mercury concentration in the
sediment >1000 ~lg/g in the rivers near the mine; these values decreased
downstream from the rivers. The remarkable levels present in the sediments are a
clear index of the intense activity of the mining complex of Almaden. In the study
performed by the Institute of Biophysics, the value of mercury in the sediment at
the confluence of the rivers Arroyo Azogado and Rio Valdeazogues was of the
order of 650 ~lg/g. The sediment of the Rio Gualdamez, sampled at about 15 km
from the mine complex, presented concentration values of 3-4 ~lg/g.
2.6
Mercury in the River Water
In Table 1 the mercury concentrations of surface water (mean annual value)
measured during the years 1988-1993 by the laboratory of Minas de Almaden are
reported.
The annual decrease in mercury concentration in the waters is attributable
to both the productivity reduction and the installation of an abatement plant.
The maximum value reported by the ORNL (1974-1977) is higher than 300 pg/l.
The determination performed by the Institute of Biophysics in the years 19931994 yielded concentration values in the range 10-20 ng/l, with a maximum
value of 80 ng/l at the confluence of the rivers Arroyo Azogado and Rio
Valdeazogues.
2.7
Mercury in the Biota
In the ecological survey of the concentration and distribution of mercury in
terrestrial and aquatic life performed by the ORNL, the mean concentration in
plants ranged from >100 ~lg/g within 0.5 km of the mine to 1 ~lg/g 20 km distant
from the mine.
Total mercury concentration in fish muscle tissue decreased with distance
downstream from the mine. Levels ranged from 2.4 ~lg/g in Barbo to 0.3 ~lg/g
(boga) at the control station. In the recent field campaign performed by the
Institute of Biophysics on plants (Maserti et al. 1996) mercury concentrations
Table 1. Mercury concentration (~lg!l) in the waters of the rivers Arroyo Azogado and Rio
Valdeazogues
1988
1989
1990
1991
1992
1993
Arroyo Azogado
0.114
0.093
0.008
0.016
0.001
<0.001
Rio Valdeazogues
<0.001
R. Ferrara
2.S
Mercury in the Sediment
In the years 1974-1975, the ORNL measured mercury concentration in the
sediment >1000 ~lg/g in the rivers near the mine; these values decreased
downstream from the rivers. The remarkable levels present in the sediments are a
clear index of the intense activity of the mining complex of Almaden. In the study
performed by the Institute of Biophysics, the value of mercury in the sediment at
the confluence of the rivers Arroyo Azogado and Rio Valdeazogues was of the
order of 650 ~lg/g. The sediment of the Rio Gualdamez, sampled at about 15 km
from the mine complex, presented concentration values of 3-4 ~lg/g.
2.6
Mercury in the River Water
In Table 1 the mercury concentrations of surface water (mean annual value)
measured during the years 1988-1993 by the laboratory of Minas de Almaden are
reported.
The annual decrease in mercury concentration in the waters is attributable
to both the productivity reduction and the installation of an abatement plant.
The maximum value reported by the ORNL (1974-1977) is higher than 300 pg/l.
The determination performed by the Institute of Biophysics in the years 19931994 yielded concentration values in the range 10-20 ng/l, with a maximum
value of 80 ng/l at the confluence of the rivers Arroyo Azogado and Rio
Valdeazogues.
2.7
Mercury in the Biota
In the ecological survey of the concentration and distribution of mercury in
terrestrial and aquatic life performed by the ORNL, the mean concentration in
plants ranged from >100 ~lg/g within 0.5 km of the mine to 1 ~lg/g 20 km distant
from the mine.
Total mercury concentration in fish muscle tissue decreased with distance
downstream from the mine. Levels ranged from 2.4 ~lg/g in Barbo to 0.3 ~lg/g
(boga) at the control station. In the recent field campaign performed by the
Institute of Biophysics on plants (Maserti et al. 1996) mercury concentrations
Table 1. Mercury concentration (~lg!l) in the waters of the rivers Arroyo Azogado and Rio
Valdeazogues
1988
1989
1990
1991
1992
1993
Arroyo Azogado
0.114
0.093
0.008
0.016
0.001
<0.001
Rio Valdeazogues
<0.001