Ecological Indicators 13 (2012) 178–183 Contents lists available at ScienceDirect Ecological Indicators jo ur n al homep ag e: www.elsevier.com/locate/ecolind Lichen and soil as indicators of an atmospheric mercury contamination in the vicinity of a chlor-alkali plant (Grenoble, France) Sylvain Grangeon a,∗ , Stéphane Guédron a , Juliette Asta b , Géraldine Sarret a , Laurent Charlet a a ISTerre, UMR 5275, CNRS, IRD, Université Joseph Fourier, BP 53, 38041 Grenoble Cedex 9, France b Laboratoire d’Ecologie Alpine, UMR 5553, Université Joseph Fourier, 38041 Grenoble Cedex 9, France a r t i c l e i n f o Article history: Received 23 March 2011 Received in revised form 11 May 2011 Accepted 23 May 2011 Keywords: Mercury Soils Lichens Xanthoria parietina Chlor-alkali France a b s t r a c t Atmospheric mercury (Hg) deposition around a mercury cell chlor-alkali plant located near Grenoble, south-east France, was assessed using Hg concentrations in lichens and soils. Hg content in the epi- phytic Xanthoria parietina lichen ranged from ∼0.07 to ∼2.51 g g -1 , and concentrations decreased with increasing distance to the plant, with a contamination radius of ∼2 km. Soil Hg concentration profiles were consistent with an atmospheric origin, with higher concentrations in the upper part of the profiles. Concentration of Hg in lichens and top soils (0–10 cm depth) as a function of the distance to the chlor-alkali plant exhibited highly similar variations. Using a simple first-order deposition model, mean Hg fallouts for the whole history of chlor-alkali plant are estimated to ∼36 g Hg day -1 in this area, compatible with values reported for reactive gaseous mercury (RGM) emissions of similar industrial plants. Using literature data on RGM to total Hg emission ratio, we estimate that the plant emitted ∼650 kg Hg year -1 . Two kilometres away from the plant, Hg content in top soils falls to values of (0.13 ± 0.07) g g -1 Hg, which is the local anthropogenic geochemical background level, but higher than unperturbed geochemical background found at the bottom of soil profiles (below 40 cm depth) estimated to (0.04 ± 0.01) g g -1 Hg. The present study evidences that lichens are a pertinent proxy for soil Hg contamination around chlor-alkali plants. They are attractive biomonitoring tools since sampling and preparations protocols for lichens are less time consuming than those used for soils. © 2011 Elsevier Ltd. All rights reserved. 1. Introduction Mercury (Hg) is a toxic element which bio-accumulates in the food chain, and may be a threat to human safety (Morel et al., 1998). Hg sources are of both natural and anthropogenic origin. Natural sources include volcanoes, soil erosion and oceans, whereas anthro- pogenic sources are various and have changed with time. Fossil fuel combustion dominates emissions, but gold mining activities and metal or cement production contribute significantly. Although their contribution have significantly decreased at the end of the 20th century, chlor-alkali plants still represent ∼2% of total anthro- pogenic Hg emissions (Pacyna et al., 2001, 2009; Roos-Barraclough et al., 2002b). In these plants, elemental mercury is used as a flowing cathode in electrolytic cells that produce Cl 2 from NaCl. Because the whole process uses heated solutions, elemental mercury volatilizes and escapes the plant (Kinsey et al., 2004), leading to mercury emis- sions in the range of ∼40–180 ng/m 3 (Dommergue et al., 2002; ∗ Corresponding author. Tel.: +334 76 63 59 28; fax: +334 76 63 52 00. E-mail addresses: Sylvain.Grangeon@ujf-Grenoble.fr (S. Grangeon), Stephane.Guedron@ujf-Grenoble.fr (S. Guédron), jasta@ujf-grenoble.fr (J. Asta), Geraldine.Sarret@ujf-Grenoble.fr (G. Sarret), Charlet38@gmail.com (L. Charlet). Landis et al., 2004; Wängberg et al., 2005). Hg is emitted under different chemical forms: mainly as elemental gaseous mercury (Hg ◦ ), but also as reactive gaseous mercury (RGM) and mercury bound to particles (Hg-p). RGM and Hg-p are rapidly removed from the atmosphere by wet and dry depositions, whereas Hg ◦ is only affected by dry deposition (Lee et al., 2001; Wängberg et al., 2005). As the contribution of Hg-p to total Hg emissions from chlor-alkali plants is low (Wängberg et al., 2005), it will be neglected in the present study. Since RGM may deposit close to the emission source, it may accumulate in soils and be a threat to many living organisms, including humans. As a support to this hypothesis, contamination of fungi, vegetables, fishes or humans living in the vicinity of such plants has been reported (Bravo et al., 2009, 2010; Dufault et al., 2009; Lodenius and Herranen, 1981; Ullrich et al., 2007). Some living forms do not take up metals via transfer from soils, but via direct absorption from the atmosphere, both by dry and wet deposition. Among them, lichens and mosses are certainly the most studied and are often used as “bio-monitors” of different met- als emissions, including Hg, from point sources such as industries (Bargagli, 1998; Szczepaniak and Biziuk, 2003). Lichens have the advantage to better record Hg signal than mosses, and Hg content is not influenced by their substrate (Bargagli et al., 2002; Loppi and Bonini, 2000; Sloof and Wolterbeek, 1993). They are thus species of 1470-160X/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.ecolind.2011.05.024