Abstract. Mercury (Hg) concentrations and deposition fluxes in precipitation and litterfall were measured at multiple sites (six rural sites and an urban site) across a broad geographic area in China. The annual deposition fluxes of Hg in precipitation at rural sites and an urban site were 2.0 to 7.2 and 12.6 ± 6.5 µg m −2 yr −1 , respectively. Wet deposition fluxes of Hg at rural sites showed a clear regional difference with elevated deposition fluxes in the subtropical zone, followed by the temporal zone and arid/semi-arid zone. Precipitation depth is the primary influencing factor causing the variation of wet deposition. Hg fluxes through litterfall ranged from 22.8 to 62.8 µg m −2 yr −1 , higher than the wet deposition fluxes by a factor of 3.9 to 8.7 and representing approximately 75 % of the total Hg deposition at the forest sites in China. This suggests that uptake of atmospheric Hg by foliage is the dominant pathway to remove atmospheric Hg in forest ecosystems in China. Wet deposition fluxes of Hg at rural sites of China were generally lower compared to those in North America and Europe, possibly due to a combination of lower precipitation depth, lower GOM concentrations in the troposphere and the generally lower cloud base heights at most sites that wash out a smaller amount of GOM and PBM during precipitation events.

Litterfall plays an important role in carbon and nutrient cycling of a forest ecosystem which is generally affected by climate, vegetation, forest type and age. The majority of the subtropical forests of China are occurring in nutrient poor environment, and thus there is a need to understand the role of litterfall on the recycling of C and nutrients in these forests for their proper management. We measured litter production, and carbon and nutrient return in an evergreen broad-leaved primary forest (Mt. Ailao, SW China) and a deciduous broad-leaved secondary forest (Mt. Damei, East China). The annual litterfall productions were 1124 and 490 g m -2 at the primary evergreen forest and secondary deciduous forest, respectively. Carbon return in primary evergreen forest was approximately three times greater than that in secondary deciduous forest. Litter N concentrations in the secondary deciduous forest were higher than that of the primary evergreen forest and consequently, the use efficiency of N of the secondary deciduous forest was lower than the primary evergreen forest. This reflects a stronger nutrient conservation mechanism in the primary evergreen forest than in the secondary forest.