Global forest ecosystems account for 31% of global land areas, and the cycling of materials in the forest has been considered the most complicated among all terrestrial ecosystems also from the perspective of mercury (Hg). Elucidation of the Hg biogeochemical processes in the forest ecosystem yields insights on how atmospheric mercury is evaded and sequestered in terrestrial landscapes and the fundamental understanding of Hg biogeochemical processes in such an environmentally complex system also bridges the knowledge gap in quantifying global mercury budgets driven by global biogeochemical processes. However, there is a large knowledge gap in the role of forest ecosystem whether as a sink or source in global atmospheric Hg cycling. The review represents the current new understanding of the interacting processes of multiple Hg exchange, transformation and Hg isotope fractionation in this environmentally important compartment on the basis of studies during last two decades about Hg mass balance in global forest ecosystems, the processes of Hg accumulation in forest soil and the Hg isotope fractionation during Hg biogeochemical processes in such ecosystems. Finally, forthcoming research emphasis and directions of the field are proposed at the end of the review given the existing knowledge gap in this area.
Contents
1 Introduction
2 Mercury biogeochemical processes in the forest ecosystems
3 Traditional mass balance studies of mercury in forest ecosystems
3.1 Elucidation of high litterfall mercury deposition in China:implication on global forest mercury cycling
3.2 Elucidation of low mercury runoff in forest ecosystems of China
4 Mercury accumulation in forest soil
4.1 Mercury loss during initial decomposition
4.2 Mercury accumulation during decomposition
5 Mercury isotopes chemistry in forest ecosystems
5.1 Isotope fractionation during air-foliage mercury flux
5.2 Isotope fractionation during air-soil mercury flux
5.3 Application of mercury isotopes in forest ecosystems
6 Conclusion and outlook