Abstract:The results of the laboratory pot experiments on soil mercury (Hg) immobilisation with a non-toxic and price-reasonable agent -colloidal sulphur (S) water suspension, are presented. It was shown that fertilisation with small agrochemical doses of colloidal S reduces excess Hg effectively as follows: in interstitial waters by a factor 2 − 12 times for total Hg, and 22 − 680 times for "reactive" Hg; in stems and leaves of oats -7 − 22 times; and in moss bags, reflecting soil Hg degassing, 7 − 15 times, for the most heavily Hg-spiked soils. The results obtained allowed to conclude that the immobilization of Hg occurs through Hg binding to the newly formed S-bearing functional groups in humic acids and/or sulphides.