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Mercury Isotopic Fractionation during Pedogenesis in a Tropical Forest Soil Catena (French Guiana): Deciphering the Impact of Historical Gold Mining

By S. Guédron, David Amouroux, Emmanuel Tessier, C. Grimaldi, Julien Barre, S. Berail, Vincent Perrot and M. Grimaldi

Abstract

ISI Document Delivery No.: GX5UI Times Cited: 0 Cited Reference Count: 65 Guedron, S. Arnouroux, D. Tessier, E. Grirnaldi, C. Barre, J. Berail, S. Perrot, V Grimaldi, M. Guedron, Stephane/0000-0003-4229-1566 Agence National pour la Recherche (ANR) through the project Interconnect [ANR-CESA 020 06] This study was funded by the Agence National pour la Recherche (ANR) through the project Interconnect (ANR-CESA 020 06 coordinated by Noureddine Bousserrhine from UPEC in Creteil). The authors gratefully acknowledge Cayian Feng from IPREM in Pau, Max Sarrazin and Patrick Seyler from the IRD center in Cayenne, Nicolas Gilliet from INRA in Rennes, and Tchia and Bruno Levessier from Qimbe Kio for their help in the laboratory and with field work and logistics. The authors thank the CMB company (Compagnie Miniere Boulanger) for providing us the access to the mine as well as the high-resolution topographic map used in Figure 1'. The authors also gratefully acknowledge Daniel Sabatier for his help in the identification and characterization of palm trees and leaves. The authors finally gratefullly thank the anonymous reviewers (especially reviewer 3) for their constructive reviews that allowed us to greatly improve the manuscript. 0 11 Amer chemical soc Washington 1520-5851International audienceWe used natural mercury (Hg) stable isotopes to investigate the Hg cycle in a rainforest soil catena (French Guiana) partially gold-mined during the early 1950s. Litterfall showed homogeneous Δ199Hg values [-0.18 ± 0.05‰, i.e., a modern gaseous elemental Hg (GEM) isotopic signature]. After litter decomposition, Hg bound to organic matter (OM) is mixed with Hg from pristine (-0.55 ± 0.22‰) or gold-mined (-0.09 ± 0.16‰) mineral materials. Negative Δ199Hg values in deep pristine mineral horizons (-0.60 ± 0.16‰) suggest the transfer of Hg bound to dissolved OM depleted in odd isotopes due to mass-independent fractionation during Hg abiotic reduction. Perennial palm tree leaves collected above gold-mined and pristine soil recorded contrasting Δ199Hg signatures likely resulting from GEM re-emission processes from soils and leaf surfaces. Upslope, soil δ202Hg signatures showed a negative shift (ϵ ∼ -1‰) with depth attributed to mass-dependent fractionation during Hg sorption and complexation onto iron oxides and dissolved OM. Downslope, higher δ202Hg values in soils resulted from hydromorphy [lower humification, greater Hg(II) reduction, etc.]. The unique Hg isotopic signatures of Amazonian soils probably result in multistep fractionation processes during pedogenesis (millions of years) and in a potentially different Hg isotopic signature of preanthropogenic background GEM

Topics: gaseous elemental mercury, atmospheric mercury, rain-forest, dry, hg isotopes, geochemistry, hg(ii), Engineering, deposition, signatures, transformation, accumulation, Environmental Sciences & Ecology, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, [CHIM.ANAL]Chemical Sciences/Analytical chemistry, [CHIM.POLY]Chemical Sciences/Polymers, [CHIM.MATE]Chemical Sciences/Material chemistry
Publisher: 'American Chemical Society (ACS)'
Year: 2018
DOI identifier: 10.1021/acs.est.8b02186
OAI identifier: oai:HAL:hal-01895454v1
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