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A picture of artisanal and small-scale gold mining (ASGM) in Brazil and its mercury emissions and releases

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Zuleica Carmen Castilhos at Centro de Tecnologia Mineral
Zuleica Carmen Castilhos
Lillian Maria Borges Domingos
Lillian Maria Borges Domingos
Lillian Maria Borges Domingos
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Abstract and Figures

This study presents a picture of ASGM in Brazil and prospective numbers on mercury emissions and releases in 2016, when the country declared production of about 90 tonnes of gold, of which circa 25 tonnes came from ASGM. However, it is also necessary to consider the illegal production of ASGM which is estimated to vary between 10% and eight times more than the legal production. The proposed method included: organization of spatial data on legal ASGM output, stakeholder identification and meetings, mercury metallurgical balance, quantitative measurement of mercury in the atmosphere and qualitative social aspects such as the miners' economic dependence on the managers and scenarios of illegal ASGM annual production. The main results revealed that the initial mercury (Hg)–gold (Au) production ratio was higher for the primary whole ore than for the concentrate secondary ore, which is the most frequent type of Brazilian ASGM. The amalgam filtering technique followed by mercury recovery is routine, decreasing the Hg releases to tailings ponds or to soil and water bodies. The mercury emissions by thermal decomposition of amalgam are independent of the initial mercury mass, depending only on the mercury in the amalgam and the (adequate) use or not of emission control systems. Illegal activities reduce the availability and proper use of these systems, resulting in higher emissions. Mercury emissions from ASGM in Brazil may increase the global mercury emissions estimates, while their mercury releases may represent a marginal increase. As the mercury emitted may be trapped by the rainforests added to the mercury released, the environmental contamination may pose health risks to Amazonian population, which requires immediate action.
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Environ Geochem Health (2024) 46:101
https://doi.org/10.1007/s10653-024-01881-z
ORIGINAL PAPER
A picture ofartisanal andsmall‑scale gold mining (ASGM)
inBrazil andits mercury emissions andreleases
ZuleicaCarmenCastilhos·
LillianMariaBorgesDomingos
Received: 31 January 2023 / Accepted: 23 January 2024 / Published online: 2 March 2024
© The Author(s), under exclusive licence to Springer Nature B.V. 2024
filtering technique followed by mercury recovery is
routine, decreasing the Hg releases to tailings ponds
or to soil and water bodies. The mercury emissions
by thermal decomposition of amalgam are independ-
ent of the initial mercury mass, depending only on
the mercury in the amalgam and the (adequate) use
or not of emission control systems. Illegal activities
reduce the availability and proper use of these sys-
tems, resulting in higher emissions. Mercury emis-
sions from ASGM in Brazil may increase the global
mercury emissions estimates, while their mercury
releases may represent a marginal increase. As the
mercury emitted may be trapped by the rainforests
added to the mercury released, the environmental
contamination may pose health risks to Amazonian
population, which requires immediate action.
Keywords Amazon· Metallurgic balance·
Participant observation· Minamata Convention
Introduction
Mercury (Hg) is a global pollutant. Its biogeochemi-
cal cycle shows that Hg emitted to the atmosphere can
travel long distances, since its half-life may be more
than one year. Once deposited from the atmosphere in
soil and water bodies, it can be re-emitted and remain
for long periods in this state. In aquatic environ-
ments, Hg can be biotransformed into methylmercury
(MeHg), which bioaccumulates and biomagnifies in
Abstract This study presents a picture of ASGM
in Brazil and prospective numbers on mercury emis-
sions and releases in 2016, when the country declared
production of about 90 tonnes of gold, of which circa
25 tonnes came from ASGM. However, it is also nec-
essary to consider the illegal production of ASGM
which is estimated to vary between 10% and eight
times more than the legal production. The proposed
method included: organization of spatial data on
legal ASGM output, stakeholder identification and
meetings, mercury metallurgical balance, quantita-
tive measurement of mercury in the atmosphere and
qualitative social aspects such as the miners’ eco-
nomic dependence on the managers and scenarios of
illegal ASGM annual production. The main results
revealed that the initial mercury (Hg)–gold (Au) pro-
duction ratio was higher for the primary whole ore
than for the concentrate secondary ore, which is the
most frequent type of Brazilian ASGM. The amalgam
Supplementary Information The online version
contains supplementary material available at https:// doi.
org/ 10. 1007/ s10653- 024- 01881-z.
Z.C.Castilhos(*)
Centre forMineral Technology (CETEM/MCTI), Av.
Pedro Calmon, 900, Cidade Universitária, RiodeJaneiro,
RJ21941-908, Brazil
e-mail: zcastilhos@cetem.gov.br
L.M.B.Domingos
EcoHealth Approach atMining Sites - EHM/CNPq,
Research Member, RiodeJaneiro, Brazil
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
ResearchGate has not been able to resolve any citations for this publication.
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