A Two-Year Study on Mercury Fluxes from the Soil under Different Vegetation Cover in a Subtropical Region, South China

In order to reveal the mercury (Hg) emission and exchange characteristics at the soil-air interface under different vegetation cover types, the evergreen broad-leaf forest, shrub forest, grass, and bare lands of Simian Mountain National Nature Reserve were selected as the sampling sites. The gaseous elementary mercury (GEM) fluxes at the soil-air interface under the four vegetation covers were continuously monitored for two years, and the effect of temperature and solar radiation on GEM fluxes were also investigated. Results showed that the GEM fluxes at the soil-air interface under different vegetation cover types had significant difference (p < 0.05). The bare land had the maximum GEM flux (15.32 +/- 10.44 ng<bold>m</bold>-2<bold>h</bold>-1), followed by grass land (14.73 +/- 18.84 ng<bold>m</bold>-2<bold>h</bold>-1), and shrub forest (12.83 +/- 10.22 ng<bold>m</bold>-2<bold>h</bold>-1), and the evergreen broad-leaf forest had the lowest value (11.23 +/- 11.13 ng<bold>m</bold>-2<bold>h</bold>-1). The GEM fluxes at the soil-air interface under different vegetation cover types showed similar regularity in seasonal variation, which mean that the GEM fluxes in summer were higher than that in winter. In addition, the GEM fluxes at the soil-air interface under the four vegetation covers in Mt. Simian had obvious diurnal variations.