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Adapted Sequential Extraction Protocol to Study Mercury Speciation in Gold Mining Tailings: Implications for
João Pedro Rudrigues de Souza1, Jeremie Garnier2, Julia Mançano Quintarelli2
1Institute of Chemistry, University of Brasília, Asa Norte, Brasilia 70910-900, Brazil.
Toxics
|May 24, 2024
Summary
Artisanal small-scale gold mining releases mercury into the Amazon. A new sequential extraction method reveals significant bioavailable mercury in tailings, highlighting risks to the ecosystem.
Area of Science:
- Environmental Science
- Geochemistry
- Ecotoxicology
Background:
- Artisanal small-scale gold mining (ASGM) is widespread in South America.
- ASGM releases mercury-contaminated tailings into the environment.
- Mercury bioaccumulates in ecosystems and food webs, posing risks.
Purpose of the Study:
- To study geochemical processes of mercury desorption and dissolution in ASGM tailings.
- To evaluate mercury contamination in Amazon basin tailings.
- To propose and test a modified sequential extraction procedure (SEP) for mercury analysis.
Main Methods:
- Developed a modified four-step sequential extraction procedure (SEP).
- Analyzed mercury contamination in tailings from the Amazon basin using the modified SEP.
- Measured exchangeable mercury (F1), oxidizable mercury (F2), mercury bound to Fe oxides (F3), and strongly bound mercury (F4).
Main Results:
- Total mercury concentration in tailings was 103 ± 16 mg·kg⁻¹.
- A significant portion (28%) of mercury was found in the bioavailable F1 fraction.
- Mercury bound to Fe oxides (F3) accounted for 36%, indicating retention by these minerals.
Conclusions:
- The modified SEP effectively characterizes mercury partitioning in tailings.
- High levels of bioavailable mercury in tailings pose an immediate environmental risk.
- Responsible tailings management and surveillance of ASGM are crucial for mitigating mercury contamination in the Amazon.
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