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environmental science & technology 44, 3 (2010) 1036-1042
Foliar Lead Uptake by Lettuce Exposed to Atmospheric Fallouts
Gaelle Uzu 1, Sophie Sobanska 2, Geraldine Sarret 3, Manuel Muñoz 4, Camille Dumat ( ) 1

Metal uptake by plants occurs by soil−root transfer but also by direct transfer of contaminants from the atmosphere to the shoots. This second pathway may be particularly important in kitchen gardens near industrial plants. The mechanisms of foliar uptake of lead by lettuce (Lactuca sativa) exposed to the atmospheric fallouts of a lead-recycling plant were studied. After 43 days of exposure, the thoroughly washed leaves contained 335 ± 50 mg Pb kg−1 (dry weight). Micro-X-ray fluorescence mappings evidenced Pb-rich spots of a few hundreds of micrometers in diameter located in necrotic zones. These spots were more abundant at the base of the central nervure. Environmental scanning electron microscopy coupled with energy dispersive X-ray microanalysis showed that smaller particles (a few micrometers in diameter) were also present in other regions of the leaves, often located beneath the leaf surface. In addition, submicrometric particles were observed inside stomatal openings. Raman microspectrometry analyses of the leaves identified smelter-originated Pb minerals but also secondary phases likely resulting from the weathering of original particles. On the basis of these observations, several pathways for foliar lead uptake are discussed. A better understanding of these mechanisms may be of interest for risk assessment of population exposure to atmospheric metal contamination.
1 :  Laboratoire Ecologie Fonctionnelle et Environnement (EcoLab)
PRES Université de Toulouse – Institut National Polytechnique de Toulouse - INPT – Université Paul Sabatier (UPS) - Toulouse III – Observatoire Midi-Pyrénées – CNRS : UMR5245
2 :  LAboratoire de Spectrochimie Infrarouge et Raman (LASIR)
Université Lille I - Sciences et technologies – CNRS : UMR8516
3 :  Laboratoire de géophysique interne et tectonophysique (LGIT)
CNRS : UMR5559 – Institut de recherche pour le développement [IRD] – LCPC – OSUG – INSU – Université de Savoie – Université Joseph Fourier - Grenoble I
4 :  Laboratoire de géodynamique des chaines alpines (LGCA)
CNRS : UMR5025 – OSUG – INSU – Université de Savoie – Université Joseph Fourier - Grenoble I
Sciences du Vivant/Ecologie, Environnement
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