19 Jul 2022
19 Jul 2022
Status: this preprint is open for discussion.

Seasonal variation of mercury concentration of ancient olive groves of Lebanon

Nagham Tabaja1,2,3, David Amouroux4, Lamis Chalak2, François Fourel5, Emmanuel Tessier4, Ihab Jomaa6, Milad El Riachy7, and Ilham Bentaleb1 Nagham Tabaja et al.
  • 1ISEM, Univ Montpellier, CNRS, IRD, Montpellier, France
  • 2Faculty of Agronomy, Plant Production Department, The Lebanese University, Dekwaneh, Lebanon
  • 3Plateforme de Recherche et d'Analyses en Sciences de l'Environnement (PRASE), Ecole Doctorale de Sciences et Technologie, Université Libanaise, Hadath, Liban
  • 4Université de Pau et des Pays de l’Adour, E2S/UPPA, CNRS, Institut des Sciences Analytiques et de Physico-Chimie pour l’Environnement et les Matériaux (IPREM), PAU, France
  • 5UMR CNRS 5023 LEHNA, Université Claude Bernard Lyon 1, Villeubanne, France
  • 6Department of Irrigation and Agrometeorology, Lebanese Agricultural Research Institute (LARI), P.O. box 287, Zahle, Lebanon
  • 7Department of Olive and Olive Oil, Lebanese Agricultural Research Institute (LARI), P.O. box 287, Zahle, Lebanon

Abstract. This study aimed to investigate the olive, iconic tree of the Mediterranean basin, seasonality of (Hg) mercury pollution. Hg concentrations of foliage, stems, soil surface, and litter were analyzed on monthly basis in ancient olive trees growing in two groves in Lebanon, Bchaaleh and Kawkaba (1300 and 672 m.a.s.l respectively). A significantly lower concentration was registered in stems (~7–9 ng/g) with respect to foliage (~35–48 ng/g) in both sites with the highest foliage Hg concentration in late winter-early spring and the lowest in summer. It is noteworthy that olive fruits also have the lowest Hg concentration (~7–11 ng/g). The soil has the highest Hg content (~62–129 ng/g) likely inherited through the cumulated litter biomass (~ 63–76 ng/g). good covariation observed between our foliage Hg time-series analysis and those of pCO2 and Hg concentrations of the atmospheric Northern hemisphere confirms that mercury pollution can be studied through olive trees. More precisely, spring sampling is recommended if the objective is to assess the tree's susceptibility to Hg uptake. This may draw an adequate baseline for global inventories on Hg vegetation uptake and for new studies on olive trees in the Mediterranean for reconstructing regional Hg pollution concentrations in the past and present.

Nagham Tabaja et al.

Status: open (until 10 Sep 2022)

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  • RC1: 'Comment on egusphere-2022-174', Håkan Pleijel, 11 Aug 2022 reply

Nagham Tabaja et al.


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Short summary
This is the first study conducted on monumental olive trees in a non-contaminated site of the MENA region and followed at a monthly basis over 18 months. Findings of our study indicate a higher uptake of Hg in the olive foliage compared other tissues and a remarkable Hg seasonal variation in foliage in the studied sites. The main source of foliage Hg is the atmospheric Hg and the main factor explaining the seasonality is due to the photosynthetic activity and stomatal conductance of olive.