Preprints
https://doi.org/10.5194/bg-2021-117
https://doi.org/10.5194/bg-2021-117

  17 May 2021

17 May 2021

Review status: this preprint is currently under review for the journal BG.

Mercury accumulation in leaves of different plant types – the significance of tissue age and specific leaf area

Håkan Pleijel1, Jenny Klingberg2,3, Michelle Nerentorp4, Malin C. Broberg1, Brigitte Nyirambangutse5,6, John Munthe4, and Göran Wallin1 Håkan Pleijel et al.
  • 1University of Gothenburg, Biological and Environmental Sciences, P.O. Box 461, SE-40530 Göteborg, Sweden
  • 2Gothenburg Botanical Garden, Carl Skottsbergs Gata 22A, SE-41319 Göteborg, Sweden
  • 3Gothenburg Global Biodiversity Centre, Carl Skottsbergs gata 22B, 413 19 Gothenburg, Sweden
  • 4IVL Swedish Environmental Research Institute Inc., P.O. Box 53021, SE-40014 Göteborg, Sweden
  • 5University of Rwanda, KK 737 Street, Gikondo, Kigali, PO Box 4285, Kigali, Rwanda
  • 6Global Green Growth Institute, 19F Jeongdong Building, 21-15 Jeongdon-gil, Jung-gu, Seoul 04518, Republic of Korea

Abstract. Mercury, Hg, is one of the most problematic metals from an environmental perspective. To assess the problems caused by Hg in the environment it is crucial to understand the processes of Hg biogeochemistry, but the exchange of Hg between the atmosphere and vegetation is not sufficiently well characterised. We explored the mercury concentration, [Hg], in foliage from a diverse set of plant types, locations and sampling periods to study whether there is a continuous accumulation of Hg in leaves/needles over time. Measurements of [Hg] were made in deciduous and conifer trees in Gothenburg, Sweden (Botanical Garden and city area) as well as of evergreen trees in Rwanda. In addition, data for wheat from an ozone experiment conducted at Östad, Sweden, were included. Conifer data were quantitatively compared with literature data. In every case where older foliage was directly compared with younger, [Hg] was higher in older tissue. Covering the range of current year up to four-year old needles, there was no sign of Hg saturation in conifer needles with age. Thus, over time scales of approximately one month to several years, the Hg uptake in foliage from the atmosphere always dominated over Hg evasion. Rwandan broadleaved trees had generally older leaves due to lack of seasonal abscission and higher [Hg] than Swedish broadleaved trees. The significance of atmospheric Hg uptake in plants was shown in a wheat experiment where charcoal filtrated air lead to significantly lower leaf [Hg]. To search for general patterns, the accumulation rates of Hg in the diverse set of tree species in the Gothenburg area were related to the specific leaf area (SLA). Leaf area based [Hg] was strongly negatively and non-linearly correlated with SLA, while mass-based [Hg] had a somewhat weaker positive relationship with SLA (both relationships with p < 0.001). An elaborated understanding of the relationship behind [Hg] and SLA would support large-scale modelling of Hg uptake by vegetation and Hg circulation in general.

Håkan Pleijel et al.

Status: open (until 28 Jun 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-117', Anonymous Referee #1, 10 Jun 2021 reply
  • RC2: 'Comment on bg-2021-117', Lena Wohlgemuth, 10 Jun 2021 reply

Håkan Pleijel et al.

Håkan Pleijel et al.

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Short summary
Mercury is a problematic metal in the environment. It is crucial to understand the Hg circulation in ecosystems. We explored the mercury concentration in foliage from a diverse set of plants, locations and sampling periods to study the accumulation of Hg in leaves/needles over time. Mercury was always higher in older tissue: in broadleaved trees, conifers and wheat. Specific leaf area, the leaf area per unit leaf mass, turned out to be critical for Hg accumulation in leaves/needles.
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