Weathering versus atmospheric contributions to mercury concentrations in French Guiana soils |
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| Institution: | 1. Department of Environmental Geochemistry, Fluminense Federal University, Outeiro São João Baptista, s/n., Centro, 24020-007 Niterói, RJ, Brazil;2. Embrapa Forestry, Estrada da Ribeira km. 111, C.P. 319, 83411-000 Colombo, PR, Brazil;3. Embrapa Agrobiology, BR 465 km. 7, 23890-000 Seropédica, RJ, Brazil;1. Departamento de Geoquímica, Universidade Federal Fluminense, Niterói, RJ 24020-007, Brazil;1. Civil, Environmental and Architectural Engineering, University of Colorado at Boulder, UCB 428, Boulder, CO 80309-0428, United States;2. U.S. Geological Survey, 3215 Marine St, Bldg 6, Boulder, CO 80309, United States;3. Desert Research Institute, Division of Atmospheric Sciences, 2215 Raggio Parkway, Reno, NV 89512, United States;1. Earth and Environmental Sciences, University of Geneva, rue des Maraîchers 13, CH-1205 Geneva, Switzerland;2. Institut des Sciences de la Terre Université Joseph Fourier, F-38041, Grenoble, France;3. Département de Géologie, Université Cheikh Anta DIOP, Dakar, Sénégal;4. Institut des Dynamiques de la Surface Terrestre, Université de Lausanne, Geopolis, CH-3871 Lausanne, Switzerland |
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| Abstract: | This work focuses on two possible sources of Hg in tropical soils, (i) lithogenic Hg from in situ weathering of soil parental material, and (ii) exogenic Hg from natural long-term atmospheric inputs and anthropogenic input from past and present industrial activities. The concentration of lithogenic Hg Hg]lithogenic was based on comparison of measured Hg concentration with those of elements resistant to weathering such as Nb, U, Zn, Fe. Exogenic Hg was quantified by subtracting Hg]lithogenic from total Hg concentrations. This calculation was applied to 4 French Guiana soil profiles, 3 profiles on the same toposequence (ferralsol, acrisol, hydromorphic soil) and one acrisol close to a Au mine, where elemental Hg is used. In all profiles, Hg]lithogenic varied slightly and was always below 40 μg kg?1, whereas Hg]exogenic varied considerably and reached 500 μg kg?1. The highest Hg]exogenic was calculated for the upper horizon of the acrisol close to Au mining activity, but also in the ferralsol. Concentrations of Hg were insignificant in the compact alterite in acrisols. It was concluded that pedogenesis processes that affect the natural Hg supply, combined with anthropogenic sources, explain the Hg concentrations in these tropical soils. |
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