Mercury accumulation in leaves of different plant types – the significance of tissue age and specific leaf area
<p>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 wel...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2021-12-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/18/6313/2021/bg-18-6313-2021.pdf |
| Summary: | <p>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 characterized. 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 and needles over time. Measurements of [Hg] were made for deciduous and
conifer trees in Gothenburg, Sweden (botanical garden and city area), as well
as for 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 from the current year up to 4-year-old needles in the
literature data, there was no sign of Hg saturation in conifer needles with
age. Thus, over timescales of approximately 1 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 led 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 negatively and non-linearly correlated with SLA,
while mass-based [Hg] had a somewhat weaker positive relationship with SLA.
An elaborated understanding of the relationship behind [Hg] and SLA may have
the potential to support large-scale modelling of Hg uptake by vegetation
and Hg circulation.</p> |
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| ISSN: | 1726-4170 1726-4189 |