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

Publié dansScience of the Total Environment, vol. 669, p. 185-193
Date de publication2019
Résumé

In Senegal, the environmental impact of artisanal small-scale gold mining (ASGM) usingmercury (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 andMeHg partitioning between filtered surfacewater 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 longtermHg inputs to downstreamaquatic 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
  • Soil
  • Kedougou region
  • Artisanal small-scale gold mining
  • Mercury
  • Methylmercury
Financement
  • Autre - Schmidheiny Foundation, Geneva, Switzerland
  • Autre - Augustin Lombard Foundation, Geneva, Switzerland
Citation (format ISO)
NIANE, Birane et al. Impact of recent artisanal small-scale gold mining in Senegal: Mercury and methylmercury contamination of terrestrial and aquatic ecosystems. In: Science of the Total Environment, 2019, vol. 669, p. 185–193. doi: 10.1016/j.scitotenv.2019.03.108
Fichiers principaux (1)
Article (Published version)
accessLevelRestricted
Identifiants
ISSN du journal0048-9697
421vues
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Informations techniques

Création18/03/2019 10:04:00
Première validation18/03/2019 10:04:00
Heure de mise à jour15/03/2023 15:59:45
Changement de statut15/03/2023 15:59:45
Dernière indexation17/01/2024 05:06:44
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