Atmospheric mercury incorporation in soils of an area impacted by a chlor-alkali plant (Grenoble, France): Contribution of canopy uptake

This study focused on the fluxes of mercury (Hg) and mechanisms of incorporation into soils surrounding a chlor-alkali plant suspected to have emitted up to ~600kgHgyear−1 for decades into the atmosphere. Comparison of vertical Hg soil profiles with As, Cu, Ni and Zn (which were not emitted by the p...

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Bibliographic Details
Published in:The Science of the total environment 2013-02, Vol.445-446, p.356-364
Main Authors: Guédron, Stéphane, Grangeon, Sylvain, Jouravel, Glorianne, Charlet, Laurent, Sarret, Géraldine
Format: Article
Language:English
Subjects:
Atmospheric mercury
Biodegradation, Environmental
Canopy uptake
Chemical Industry
Chlor-alkali
Crop
Crops, Agricultural
Ecosystem
Environmental Monitoring
Environmental Pollutants - analysis
Environmental Pollution - analysis
Food Chain
Mercury - analysis
Metals, Heavy - analysis
Risk Assessment
Soil
Soil - chemistry
Species Specificity
Trees - metabolism
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Summary:This study focused on the fluxes of mercury (Hg) and mechanisms of incorporation into soils surrounding a chlor-alkali plant suspected to have emitted up to ~600kgHgyear−1 for decades into the atmosphere. Comparison of vertical Hg soil profiles with As, Cu, Ni and Zn (which were not emitted by the plant) support Hg enrichment in surface horizons due to atmospheric Hg inputs from the chlor-alkali plant. Based on chemical extractions and elemental correlations, Hg was found to be weakly leachable and bio-available for plants, and most probably strongly bound to organic matter. In contrast, other trace elements were probably associated with phyllosilicates, iron oxides or with primary minerals. Hg stocks in the surface horizon of a forested soil (1255mgHgm−3) were two-fold higher than in an agricultural soil (636mgHgm−3) at a similar distance to the plant. The difference was attributed to the interception of atmospheric Hg by the canopy (most likely gaseous elemental Hg and reactive gaseous Hg) and subsequent litterfall incorporation. Some differences in the ability to trap atmospheric Hg were observed between tree species. The characterization of the litter showed an increasing Hg concentration in the plant material proportional to their degradation stage. In agricultural soils, very low Hg concentrations found in corn leaves and grains suggested a limited uptake via both the foliar and root pathways. Thus, the short-term risk of Hg transfer to agricultural crops and higher levels of the trophic chain appeared limited. A possible risk which remains to be evaluated is the possible transfer of Hg-rich particles from the forest topsoil to downstream aquatic ecosystems during rain and snowmelt events. ► Mercury incorporation in soil and vegetation near a chlor-alkali plant was studied. ► Perennials accumulate ten times more atmospheric Hg than annual crops. ► Foliar uptake is a major pathway for atmospheric Hg incorporation to forest soil. ► Litter-fall Hg input to soil was equivalent to the input by direct deposition. ► Canopy Hg inputs to soil near the plant were 6 times those of pristine environment.
ISSN:0048-9697
1879-1026
DOI:10.1016/j.scitotenv.2012.12.084