Mercury fluxes, budgets, and pools in forest ecosystems of China: A review

Abstract

Mercury (Hg) retention in forest ecosystem plays a key role in global biogeochemical cycling. We present a comprehensive review of the research status of forest Hg in China to characterize the Hg budgets and pools. Averaged total Hg (THg) inputs at remote forests and rural and suburban forests in China are about 2–4-fold and 2.5–5-fold higher than the observed values in Europe and North America, respectively. The highly elevated THg inputs are mainly derived from the elevated atmospheric Hg concentrations and litterfall biomass. THg outputs from the forest ecosystems are much lower than the atmospheric depositions. The annual THg retentions range from 26.1 to 60.4 µg m⁻² at subtropical forests and from 12.4 to 26.2 µg m⁻² at temperate forests. Given the large areal coverage, THg retention in forest is ∼69 t year⁻¹ in China and is much high than that in global scale estimated by models. The much higher THg retention has elevated the THg pools in Chinese subtropical forests. This study has implication for the role of China forests in the global Hg biogeochemical cycle and the optimization of atmospheric Hg transport and deposition models.

Graphical Abstract

Keywords:

• Atmospheric deposition
• input–output
• risk assessment
• storage
• trace metals

Additional information

Funding

This work was supported by the National Natural Science Foundation of China under Grant (41807385); and National Key Research and Development Program of China under Grant (2018YFD0800302).