Impact of recent artisanal small-scale gold mining in Senegal: Mercury and methylmercury contamination of terrestrial and aquatic ecosystems

Niane Birane, Guédron Stéphane, Feder Frédéric, Legros Samuel, Ngom Papa Malick, Moritz Robert. 2019. Impact of recent artisanal small-scale gold mining in Senegal: Mercury and methylmercury contamination of terrestrial and aquatic ecosystems. Science of the Total Environment, 669 : 185-193.

Quartile : Q1, Sujet : ENVIRONMENTAL SCIENCES

Résumé : In Senegal, the environmental impact of artisanal small-scale gold mining (ASGM) using mercury (Hg) is poorly documented despite its intensification over the past two decades. We report here a complete dataset including the distribution and speciation of Hg in soil, sediment, and water in pristine and ASGM impacted sites of the Gambia River ecosystem (Kedougou region - eastern Senegal). Selective extraction showed that soils surrounding ASGM activities were contaminated with elemental Hg [Hg(0)] at concentrations up to 3.9 mg kg−1. In the Gambia River, high total Hg (THg: 1.16 ± 0.80 mg kg−1) and methylmercury (MeHg: 3.2 ± 2.3 ng g−1) were also measured in sediment samples collected at ASGM sites. Along the stream, THg concentrations in sediment decrease with distance from the ASGM sites, while those of methylmercury increase downstream. The study of THg and MeHg partitioning between filtered surface water and suspended particles demonstrate that particulate transport is responsible for the downstream dissemination of the Hg contamination from ASGM sites. Sedimentation of fine particles enriched in Hg downstream ASGM sites likely favors MeHg production and accumulation in sediment. Although elemental Hg is weakly labile, surface soil erosion may also provide important and long-term Hg inputs to downstream aquatic ecosystems, where it can be oxidized and methylated. Finally, the dissemination of THg and MeHg downstream from the ASGM sites in the Gambia River may constitute a long-term source of contamination and can have a large scale impact on the aquatic ecosystem through biomagnification.

Mots-clés Agrovoc : artisanat, or, pollution du sol, pollution de l'eau

Mots-clés géographiques Agrovoc : Sénégal

Mots-clés complémentaires : Exploitation minière

Mots-clés libres : Mercury, Methylmercury, Kedougou region, Artisanal small-scale gold mining, Soil contamination

Classification Agris : P02 - Pollution
E80 - Économie familiale et artisanale

Champ stratégique Cirad : CTS 4 (2019-) - Santé des plantes, des animaux et des écosystèmes

Auteurs et affiliations

• Niane Birane, UNIGE (CHE) - auteur correspondant
• Guédron Stéphane, Université Grenoble Alpes (FRA)
• Feder Frédéric, CIRAD-PERSYST-UPR Recyclage et risque (SEN) ORCID: 0000-0001-8434-5193
• Legros Samuel, CIRAD-PERSYST-UPR Recyclage et risque (SEN) ORCID: 0000-0001-7081-6679
• Ngom Papa Malick, UCAD (SEN)
• Moritz Robert, UNIGE (CHE)

Source : Cirad-Agritrop (https://agritrop.cirad.fr/591702/)

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