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Mercury inputs into the Amazon Region, Brazil
a
W. C. Pfeiffer & L. Drude de Lacerda
b
a
Lab. Radioisótopos, List, de Biofísica Carlos Chagas Filho, UFRJ, Rio de Janeiro, RJ, 21941,
Brazil
b
Departamento de Geoquímica, UFF, Niterói, 24.210, RJ, Brasil
Published online: 17 Dec 2008.
To cite this article: W. C. Pfeiffer & L. Drude de Lacerda (1988): Mercury inputs into the Amazon Region, Brazil,
Environmental Technology Letters, 9:4, 325-330
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Environmental Technology Letters, Vol. 9, pp. 325-330
©Publications Division Selper Ltd., 1988
MERCURY INPUTS INTO THE AMAZON REGION,
BRAZIL
W. C. Pfeiffer* and L. Drude de Lacerda**
*Lab. Radioisótopos, List, de Biofísica Carlos Chagas Filho,
UFRJ, Rio de Janeiro, RJ, 21941, Brazil
**Departamento de Geoquímica, UFF, Niterói, 24.210, RJ., Brasil
Downloaded by [University of Chicago Library] at 11:39 21 June 2013
(Received 11 September 1987; in final form 27 October 1987)
ABSTRACT
Mercury inputs into the Brazilian Amazon ecosystem due
to goldmining activities are quantified based on data from various
Brazilian Mineral and Environmental Agencies as well as field
works. Total losses of Hg were estimated to be 1.32 kg Hg/kg Au
from which 45% are released into rivers and 55% into the
atmosphere. Total Hg input to the Amazon may contribute with up to
6% of the global anthropogenic Hg emissions to the atmosphere and
the releases into the rivers are at the same order of magnitude as
the inputs into the North Sea.
INTRODUCTION
Goldmining has become a major activity in the Brazilian
Amazon Region involving presently circa 400 thousand men (Pig. 1).
In all sites mercury is used in the extraction to amalgamate the
fine gold particles (1). Although this
activity exists at least for the last 10 years, only recently the
potential threat of Hg contamination of the Amazonian ecosystems
has been considered by local environmental authorities. Some
attempts to evaluate the problem have been made (1, 2) however,
lack of reliable informations, logistic difficulties and the
inexistance of a central environmental authority for the majority
of Amazon States have lead to some misinformations and a number of
conflictive data of diflcult use for scientific purposes.
The present paper aims to quantify Hg inputs into the
Amazon
ecosystems. Results are based on data from various
Brazilian Mineral Production Authorities, local Environmental or
Geological Survey Agencies and field work performed by the authors
in various mining sites.
Mercury is used in the process of gold complexing either
manually
or
mechanically in all sites. Losses
of mercury
occurs during the gold amalgamation" process in pans and in riffles •
(woden boxes
with inclined stair-like bottoms covered with
cloths) both along the river banks and on boats. In the pans
process losses of metallic Hg reaches circa 5-10% of the used
amount, while in the riffles it can be doubled (10-20%), entering
the
rivers directly as metallic Hg. The Au-Hg complex is
gravimetrlcally separated and the excess of Hg is recovered by
325
squeezing the mixture in a cloths for reutillzation. The amalgam
is then burnt to .separate the gold and the totality of Hg used Is
lost into the atmosphere as Hg° vapour. The percentage from the
initial mercury retained in the amalgam and therefore lost to the
atmosphere is circa 20%. The initial amount used by the miner
depends on the gold content estimated by eye. In general this
relationship Au:Hg is 1:3 to 5 (W.C.P. and L.D.L., personal
observations).
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SCALE 1 17000 0 0 0
Sludv
Ar»q: BRAZIL
I Gotfmintng Areas
FIGURE 1 I
MAJOR GOLDMINtNG AREAS IN THE BRAZILIAN
AMAZON REGION
However, other losses can, and problaby due occur,
during the process. During the recovery step, losses of metallic
Hg are very common. In general the gold produced by this process
still contains small quantities of Hg and are normally reburned by
the gold dealer. Since high temperatures ( 40° C) are easily
reached in the gold mining sites and boats, losses of Hg also
occur by evaporation during the entire process. These losses are
difficult to estimate but can easily account for about 5% of the
initial Hg amount used in the process. Figure 2 presents a diagram
326
of the entire gold production process in the Amazon region through
Hg- amalgamation and the estimated Hg losses to the environment.
The final
ratio of Au:Hg of 1:1.32 is probably very
undersestiraated since rough field conditions difficult Hg recovery
and miners frequently use Au:Hg ratios of 1:6 and even 1:10 (1).
The Hg recovered in the process is normally reused only 3 or k
times and then thrown away into the rivers. However, here we will
use the 1:1.32 ratio as the best approach to reality even if in
the future, optimization of the process would occur.
Figure X
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Gold production through Hg amalgamation in the Amazon rivers
(Number in parenthesis are minimum estimated Hg losses for
the production of 1 kg Au)
Hg losses
Gravimetric Au preconcentration
X
Concentrate
Addition of Hg to pans or
riffles, Au:Hg ratio = 1 : 4
Losses to rivers
(0.40 kg)
Au-Hg amalgam
Squeezing of excess
Vaporization to
atmosphere
(0.72 kg)
Burning of Amalgam
Hg recovery
c.a. 70%
Evaporation by
handling and
reburning
(0.20 kg)
Total losses: 1.32 kg Hq for 1 kg Au
The second, and major difficulty in calculating Hg
losses is the estimation of the actual gold production. Most of
the produced gold is sold locally and send to non official gold
dealers in Rio de Janeiro and Sao Paulo. This non- official market
represents about 80% of total gold production and local gold
dealers believe that only 10$ of the total gold production is sold
to the government (L.D.L. per.obs). This would give a relationship
between official data and the real production of circa 1:8 to 10.
The official gold production in the Madeira River in 1985 was
1,471 Kg, as can be seen from Table 1 where official gold
production data for the major mining areas in the Amazon region
are presented. Local gold dealers and the Miners Union estimates
this number around 14 to 17 tons. The local geologists from the
327
National Department
between 8 and 10.
of Mineral Production estimate
this
number
Table 1
OFFICIAL GOLD PRODUCTION IN THE AMAZON REGION
Mato Grosso
3 ,822
Roralma
65
4 ,925
Para-Goias
Amapa
124
Para.
1 ,80-0
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Amazonas-Para.
52
1 ,359
Madeira
Total:
k g . y - 1 . (4)
(Average between 1979 and 1982)
(Value for 1981)
(Average between 1979 and 1982)
(Value for 1982)
(Average between 1981 and 1982)
(Value for 1981)
(Average between 1979 and 1985)
12,147
Another way to approach the problem and reach a number
as close as possible to reality is to calculate the minimum gold
production necessary to mantain a dredge and i t s crew. Considering
the equipment and the local difficulties, a minimum of 40 g of
gold per day would be necessary. The mining activity last for
circa 200 days a year, although some dredges carry on working even
during the rainy season. In 1985 circa 1,400 boats were working in
the Madeira River, which would give a total production of 11,200
tons of gold per year, close to the estimated real gold production
in the area. Therefore a relationship between official and real
production would be of 1:8. Although probably underestimated, this
number is used in this paper to estimate Hg releases into the
environment.
Table 2 presents the estimates of Hg fluxes to the
Table 2
ESTIMATES OF Hg FLUXES TO THE ENVIRONMENT
Official Production
Minimum estimated*
Maximum estln
Au production
12,147
72,882
97,176
Hg loss t o rivers
Kg.y" 1
7,288
43,729
58,306
Hg loss t o Atmosphere
1
8,746
52,475
69,967
Total Hg loss
Kg.y- 1
16,034
96,204
128,873
Kg.r
*Based on the minimum Au production/Hg losses
**Based on the maxium Au productlon/Hg losses
328
environment based on the official and the above estimated
real
gold production of the region. Prom this data one can see that Hg
fluxes to the Amazon environment are at the order of 128 ton.y-1,
from which about 55# enters the atmosphere as Hg° vapour and
H%
enters the rivers as metalic Hg.
Table 3
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GLOBAL
MERCURY EMISSION TO THE ATMOSPHERE COMPARED
EMISSIONS IN THE AMAZONIAN GOLD MINING AREAS
Source
ton.y"1 Hg
Author
Natural Sources
2,700
6,000
(5)
(6)
Anthropogenic
630
2,000
(5)
(6)
Amazonian Goldralning
Areas
50-70
WITH
This study
Based on this data, comparing Hg emission to the
atmosphere in the Amazon goldmining areas with the most
recent
estimates of global Hg emissions to the atmosphere the Amazon area
presently contributes with circa 1% of the total global emissions
and with about 6% of the anthropogenic emissions. On the other
hand Hg
releases in the Amazon are already of the same order of
magnitude as the Hg input into the North Sea (3) (Table 3 ) .
The situation described above may
represent a real
threat of Hg contamination to the Amazonian environment, since if
contamination of local fisheries occurs, a great portion of local
population would be affected. On the other hand, the study
Hg
biogeocheralsty in this region should give important insights to
the understanding of the global Hg cycle.
ACKNOWLEDGMENTS
The authors wich to thank the Federal University
Rondonia, Ene G. da Silveira, Ana A. P. Boischio and Luiz
Femandes for local support. This research was supported
SUDECO, FIPEC, FINEP and CNPq.
of
C.
by
REFERENCES
(1) Mallas, J. & Benedicto, N. Mercury and Goldmining
Brazilian Amazon. Ambio. 15: 248-249 (1986).
in
the
(2) UNIR. I Seminário sobre contarainação por mercúrio no Rio
Madeira. Univ. Fed. Rondônia. Porto Velho (in press) (1986).
(3) Salomons, W. & Förstner, V. Metals in the hydrocycle. Springer
Verlag, Berlin, 249 p. (1984).
329
1
(4) DNPM. Garimpos do Brasil. Dept. Nac. Prod. Mineral Publ.
Avulsa n°. 5, Brasilia, DP,, 301 p. (1983).
(5) Pacyna, J.M. Atmospheric trace elements from natural and
anthropogenic sources, In: Nriagou, J.O. and Davidson, C.I.
(eds.). Toxic Metals in the Atmosphere. Wiley. New York
(1984).
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(6) SCOPE.
I
International SCOPE Metals Cycling Workshop.
Rapporteur's Report on Mercury. Sclent. Comm. Problems of the
Environment. Toronto. 16 p. (1985).
330