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Environmental problems - Chemical approaches
RESEARCH ARTICLE

Mosses and lichens enhance atmospheric elemental mercury deposition in a subtropical montane forest

Xin Li A B , Xun Wang B , Hui Zhang B and Zhiyun Lu https://orcid.org/0000-0001-9488-3366 A C *
+ Author Affiliations
- Author Affiliations

A CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Xishuangbanna, Yunnan 666303, China.

B State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, Guizhou 550081, China.

C National Forest Ecosystem Research Station at Ailaoshan, Jingdong, Yunnan 676209, China.

* Correspondence to: luzy@xtbg.ac.cn

Handling Editor: Jing Ming

Environmental Chemistry 20(3) 105-113 https://doi.org/10.1071/EN22124
Submitted: 27 November 2022  Accepted: 25 February 2023   Published: 20 June 2023

© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing.

Environmental context. Mosses and lichens are widely distributed in montane forests and their important role in global biogeochemical cycles has been increasingly recognised. This study of mercury accumulation and sources in mosses and lichens, using mercury isotopic data, provides evidence that they promote atmospheric mercury deposition in these forests, which is an important function that should be incorporated into current mercury mass balance budgets for forests.

Rationale. Mosses and lichens, which are widely distributed in montane forests, are often used to monitor the atmospheric mercury (Hg) depositions. In this study we hypothesised that atmospheric Hg uptake by mosses and lichens could greatly promote Hg depositions in montane forests.

Methodology. We comprehensively determined the Hg concentration and isotopic signatures of various species of mosses and lichens in a subtropical montane forest, to quantify the Hg accumulation, influencing factors and potential Hg depositions induced by mosses and lichens.

Results. Our results show that the higher Hg concentrations in mosses than in lichens are mainly due to their species-specific, morphological and physiological differences. Hg isotopic mixing model results display that uptake of atmospheric elemental Hg (Hg0) contributes 89.2 ± 22.8% of Hg in mosses and 88.4 ± 24.4% in lichens. The lichens growing on trees have a lower atmospheric Hg0 source contribution than on the ground (61.3 ± 42.5% versus 93.6 ± 10.0%) because of the elevated rainfall Hg uptake on trees. The Hg storage in live moss and lichen is 28.0 ± 16.5 and 0.9 ± 1.0 μg m−2, respectively. Given the 1–2-year lifespan of moss, the moss induced atmospheric Hg deposition is almost equivalent to litterfall Hg deposition which was previously used as a proxy for atmospheric Hg0 deposition in forests.

Discussion. Overall, we suggest mosses and lichens play an important role in atmospheric Hg depositions and recommend more research in montane forests.

Keywords: lichen, mercury deposition, mercury isotopes, mercury pool, mercury sources, mercury concentration, moss, subtropical forest.


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