Translocation and distribution of mercury in biomasses from subtropical forest ecosystems: evidence from stable mercury
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ORIGINAL ARTICLE
Translocation and distribution of mercury in biomasses from subtropical forest ecosystems: evidence from stable mercury isotopes Yi Liu1,2
•
Che-Jen Lin1,3,4 • Wei Yuan1,2 • Zhiyun Lu5 • Xinbin Feng1
Received: 25 September 2020 / Revised: 25 September 2020 / Accepted: 15 October 2020 Ó Science Press and Institute of Geochemistry, CAS and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract To understand its source, distribution, storage, and translocation in the subtropical forest ecosystems, mercury (Hg) concentrations and stable isotopes in forest biomass tissues (foliage, branch, bark, and trunk) were investigated at Ailao Mountain National Nature Reserve, Southwest China. The total Hg (THg) concentrations in the samples show the following trend: mature foliage (57 ± 19 ng g-1) [ bark (11 ± 4.0 ng g-1) [ branch -1 (5.4 ± 2.5 ng g ) [ trunk (1.6 ± 0.7 ng g-1). Using the measured THg concentrations and the quantity of respective biomasses, the Hg pools in the forest are: wood (60 ± 26 lg m-2) [ bark (51 ± 18 lg m-2) [ foliage (41 ± 11 lg m-2) [ branch (26 ± 8.3 lg m-2). The tree biomasses displayed negative d202Hg (- 1.83% to - 3.84%) and D199Hg (- 0.18% to - 0.62%). The observed D200Hg (- 0.08% to 0.04%) is not significantly from zero. A D199Hg/D201Hg ratio of 1.05 was found in tree biomasses, suggesting that mercury has undergone Hg(II) photoreduction processes. A Hg-isotope based binary & Che-Jen Lin [email protected] & Xinbin Feng [email protected] 1
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
2
University of Chinese Academy of Sciences, Beijing, China
3
Center for Advances in Water and Air Quality, Lamar University, Beaumont, TX, USA
4
College of Environment and Energy, South China University of Technology, Guangzhou, China
5
National Forest Ecosystem Research Station, Ailaoshan, Yunnan, China
mixing model suggests that Hg in the tree biomasses mainly originated from foliage uptake of atmospheric Hg0, constituting 67%, 80%, and 77% of Hg in wood, branch, and bark, respectively. Our study sheds new light on the transportation and sources of Hg in the subtropical forest ecosystems. Keywords Hg Subtropical forest ecosystem Hg stable isotope Hg-isotope based binary mixing model
1 Introduction Mercury (Hg) in the atmosphere mainly exists ([ 90%) in the form of gaseous elemental Hg (GEM) (Gratz et al. 2010), whose atmospheric lifetime (0.5 - 1 year) allows long-range transport globally (Selin 2009). Forest ecosystems play an important role in the biogeochemical cycling of Hg on a global scale. Oxidation of Hg0 followed wet deposition (e.g., precipitation and/or throughfall), or Hg0 uptake by vegetation followed by litterfall deposition are the main pathways for Hg deposition. Recent studies suggested that the forest ecosystems act as a major sink of atmospheric Hg0 through litterfall Hg deposition (Johnson and Lindberg 1995; Laacouri et al. 2013; Louis et al. 2001; Wang et al.
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