Quantifying the impacts of artisanal gold mining on a tropical river system using mercury isotopes. (March 2019)

• Record Type: Journal Article
• Authors: Goix, Sylvaine; Maurice, Laurence; Laffont, Laure; Rinaldo, Raphaelle; Lagane, Christelle; Chmeleff, Jerome; Menges, Johanna; Heimbürger, Lars-Eric; Maury-Brachet, Régine; Sonke, Jeroen E.
• Is Part Of: Chemosphere. Volume 219(2019)
• Page Start: 684
• Page End: 694
• Publication Date: 2019-03
• Subjects: Mercury stable isotopes -- Mercury speciation -- Artisanal and small-scale gold mining (ASGM) -- French Guiana; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2018.12.036
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: In some locations, artisanal and small-scale gold-mining (ASGM) represents a significant source of anthropogenic Hg to freshwater environments. The Hg released from ASGM can contaminate aquatic fauna and pose health risks to downstream populations. Total Hg (THg) concentrations, speciation, and isotopic compositions were analyzed in water, suspended particulate matter, soil, and bottom sediment samples from pristine areas and in places of active and legacy gold mining along the Oyapock River (French Guiana) and its tributaries. Mass-independent fractionation (MIF) of even Hg isotopes in top soils (Δ 200 Hg = −0.06 ± 0.02‰, n = 10) implied the uptake of gaseous Hg(0) by plants, rather than wet deposition, as the primary Hg source. Odd isotope MIF was lower in deep soils (Δ 199 Hg = −0.75 ± 0.03‰, n = 7) than in top soils (Δ 199 Hg = −0.55 ± 0.15‰, n = 3). This variation could be attributed to differences between the isotopic signatures of modern and pre-industrial atmospheric Hg. Combining a Hg-isotope binary mixing model with a multiple linear regression based on physico-chemical parameters measured in the sediment samples, we determined that active mined creek sediments are contaminated by ASGM activities, with up to 78% of THg being anthropogenic. Of this anthropogenic Hg, more than half (66–74%) originates from liquid Hg(0) that is released during ASGM. The remaining anthropogenic Hg comes from the ASGM-driven erosion of Hg-rich soils into the river. The isotope signatures of anthropogenic Hg in bottom sediments were no longer traceable in formerly mined rivers and creeks. Graphical abstract: Image 1 Highlights: Hg isotope ratios measured in soils and river sediments from French Guiana. Hg isotope ratios coupled to multiple linear regression to quantify anthropogenic Hg. Active ASGM activities increase THg in sediments by 78%. Up to 70% of anthropogenic Hg originates from liquid Hg used in ASGM.