Mercury Release Flux and Its Influencing Factors Under Four Typical Vegetation Covers at Jinyun Mountain, Chongqing

Abstract

In order to reveal the characteristics of mercury release flux and exchange across the soil/atmosphere interface under different vegetation cover types, four of these types (evergreen broad-leaved forest, bamboo forest, shrub, and grassland) were chosen as research samples at Jinyun Mountain National Nature Reserve, Chongqing, Continuous monitoring of the different vegetation covers, soil/atmosphere interface, and mercury release flux was conducted, at the same time as the effects of environmental factors were also considered. Results show that the annual average Hg emission flux for the four kinds of forest cover have obvious differences. The overall emission performance of Hg is ranked as:bamboo forest[17.77 ng·(m2·h)-1] > grassland[17.58 ng·(m2·h)-1] > shrubbery[16.87 ng·(m2·h)-1] > evergreen broad-leaved forest[14.32 ng·(m2·h)-1]. There are obviously seasonal differences between Hg emission and the four kinds of forested stands in Jinyun mountain and there are significant differences among the different forests. These differences mainly reflect that emissions in the warm season are higher than in the cold season. There is also an obvious diurnal variation of soil mercury release flux from different forested stands in Jinyun Mountain. Meteorological factors of light intensity, air temperature, soil temperature, and relative humidity also effects the soil/air interface meaning that mercury flux is not the same across land cover types. Temperature is the main factor affecting evergreen broad-leaved forest, shrub forests, and bamboo forests. Light intensity is the main influencing factor for grasslands.