THE SULFUR-MERCURY(II) SYSTEM IN NATURAL-WATERS

Sulphur is an essential element for aquatic biosystems, the life processes of which lead to the formation of low moelcular weight S compounds in the water. The results of our calculations indicate a pronounced tendency for Hg(II) to form HgS (or HgOHSH) and Hg(SR)2 complexes in the presence of H2S and thiols. Likewise, MeHg will form CH3HgSH and CH3HgSR complexes, but in this case the chloride complex will dominate at low concentrations of H2S and thiols. In acidic low salinity water, CH3HgCl is the dominant MeHg species at the lowest concentration of sulphide/thiols (0.1 nM), whereas a hundredfold increase of the sulphide/thiol concentration, or an increase of the pH to neutral or slightly alkaline conditions, will result in a total dominance for CH3HgSH and CH3HgSR.