Translocation of Hg-203 labelled HgCl2, and CH3HgCl in an iron-humus podzol studied by radio-analytical techniques

Since increased Hg-concentrations in fish in lakes and rivers in northern Europe, northern parts of the U.S.A. and Canada were found, environmental Hg research has focused intensively on the factors determining leaching of mercury from soil into water systems. This article presents the results of a leaching experiment with undisturbed soil columns treated with HgCl2 and CH3HgCl using radio-analytical techniques. The columns were irrigated with rain of different acidity, rain volumes and irrigation intensities. The leaching of mercury was traced volumes and irrigation intensities. The leaching of mercury was traced by detecting the vertical distribution of Hg-203 in the soil profiles. Advantages and disadvantages of radioanalytical scanning techniques are discussed. The results of Hg leaching in the soil columns indicate a considerably stronger leaching of monomethyl mercury compared to inorganic mercury. Leaching of the two Hg-species is ruled by competition of H+ induced soil-Hg desorption with DOM-Hg complex formation; both being affected by rain acidity. Rain intensity had no visible effect on leaching of Hg2+ and CH3Hg+. An extended rain duration increased the leaching of CH3Hg+.