Abstract
Abstract. The mid-subtropical forest area in southwest China was affected by anthropogenic mercury (Hg) emissions over the past 3 decades. We quantified mercury dynamics on the forest field and measured fluxes and pools of Hg in litterfall, throughfall, stream water and forest soil in an evergreen broadleaved forest field in southwestern China. Total Hg (THg) input by the throughfall and litterfall was assessed at 32.2 and 42.9 µg m−2 yr−1, respectively, which was remarkably higher than those observed from other forest fields in the background of North America and Europe. Hg fluxes across the soil–air interface (18.6 mg m−2 yr−1) and runoff and/or stream flow (7.2 µg m−2 yr−1) were regarded as the dominant ways for THg export from the forest field. The forest field hosts an enormous amount of atmospheric Hg, and its reserves is estimated to be 25 341 µg m2. The ratio of output to input Hg fluxes (0.34) is higher compared with other study sites. The higher output / input ratio may represent an important ecological risk for the downstream aquatic ecosystems, even if the forest field could be an effective sink of Hg.
Highlights
Mercury (Hg) can cause damage to the environment and human health due to its extreme toxicity
Canopy density did have an effect on total Hg (THg) and methyl Hg (MeHg) concentrations
The mass balance and transport of Hg in southwestern China were first measured at a subtropical forest, Chongqing, China
Summary
Mercury (Hg) can cause damage to the environment and human health due to its extreme toxicity. Atmospheric deposition is the principal form of total Hg (THg) input to aquatic systems in remote pristine regions. Forest ecosystem is generally regarded as an active pool of Hg. Hg transformation processes in the forest is considered a vital part of global Hg cycling (Ericksen et al, 2003; Sigler et al, 2009). Most of the Hg accumulated in canopy foliage comes from atmospheric sources, rather than root uptake (Ericksen et al, 2003; Stamenkovic and Gustin, 2009). Hg accumulated in the forest soil may be considered a source of both total and methyl Hg (MeHg) to aquatic ecosystems through runoff and/or stream flow. The release of Hg compounds from the forest field can be considered an initial step of Hg mobilization in forested catchments, and seems to be of high importance for its mobility
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