Seasonal variation of mercury concentration of ancient olive groves of Lebanon

[摘要] This study investigates the seasonality of the mercury (Hg)concentration of olive tree foliage, an iconic tree of the Mediterraneanbasin. Hg concentrations of foliage, stems, soil surface, and litter wereanalyzed on a monthly basis in ancient olive trees growing in two groves inLebanon, Bchaaleh and Kawkaba (1300 and 672 m a.s.l. respectively). Asignificantly lower concentration was registered in stems ( ∼7 –9 ng g −1 ) in comparison to foliage ( ∼35 –48 ng g −1 ) in both sites,with the highest foliage Hg concentration in late winter–early spring andthe lowest in summer. It is noteworthy that olive fruits also have low Hgconcentrations ( ∼7 –11 ng g −1 ). The soil has the highest Hgcontent ( ∼62 –129 ng g −1 ) likely inherited through the cumulatedlitter biomass ( ∼63 –76 ng g −1 ). A good covariation observedbetween our foliage Hg time series analysis and those of atmospheric Hg concentrations available for southern Italy in the western Mediterraneanbasin confirms that mercury pollution can be studied through olive trees.Spring sampling is recommended if the objective is to assess the trees'susceptibility to Hg uptake. Our study draws an adequate baseline for theeastern Mediterranean and the region with similar climatic inventories on Hgvegetation uptake, in addition to being a baseline to new studies on olivetrees in the Mediterranean to reconstruct regional Hg pollutionconcentrations in the past and present.

[学科分类] 大气科学