[Mercury fluxes from conifer-broadleaf forested field in central subtropical forest zone]

Total gaseous mercury fluxes of forested field soils in the subtropical forest zones, Chongqing, Southwestern China were continually monitored from April 2011 to March 2012 to provide insights into the characteristics of gaseous mercury flux with conifer-broadleaf forest covers. Samples were collected from surfaces of forest fields as the most representative terrestrial surfaces in Jinyun Mountain. Simultaneously, meteorological parameters at the soil level relating to GEM fluxes, such as soil temperature, air humidity, and solar radiation were analyzed, and variations of atmospheric GEM concentration were examined. The results showed that annual averaged fluxes from soils in the forest and open-air site were (16.82 +/- 6.70) ng x (m2 x h)(-1), which was significantly higher than that in the natural background area. Moreover, there was a clear seasonal variation on the forest field. In growing season, the average mercury flux was (22.23 +/- 13.19) ng x (m2 x h)(-1), while in dormant season the value was (6.01 +/- 4. 05) ng x (m2 x h)(-1). Diurnal variation characteristics of mercury fluxes were closely related to solar radiation on the forest field. Mercury fluxes of the soils were significantly correlated with soil temperature, air temperature and relative humidity, which may be caused by the relationship between solar radiation intensity and mercury emission fluxes from soils.