The kinetics of Hg volatilization indicated that humus (including fulvic acid, brown humic acid and grey humic acid) have either suppressing or activating effect on the volativity of mineral bound Hg. Initially the volatilization of mineral bound Hg is depressed and then is promoted, but eventually it turns into a stable state. The effect is characterized by long term and gradual change. Various kinds of humic acids have different rate and intensity to depress or promote the volatilization of mineral bound Hg. The type of mineral bound to the Hg is the internal factor that will determine the progress of the volatilization reaction.