For pH < 8, the here proposed mechanism for the generation of Hg0 is the
reduction of aqueous Hg2+ by residual SO3
2- according to Eq1. Further evaluation indicates additional
evidence for the assumption for SO3
2- being the dominant reducing agent in the low pH region. Almost
identical dependency on pH of both Hg0 formation and share of SO3
2- on total Sulfites, calculated using the acid constant of H2SO3 in water is presented by Figure 1b). For the high pH range (> pH 8), a differing
mechanism is proposed. Due to the maximized share of SO3
2-, it is likely that OH- is a possible second
corresponding electron donor for the reduction of Hg2