With the extensive utilization and disposal of flue gas desulfurization (FGD) gypsum, Hg-0 re-emission and Hg2+ dissolution could cause severe atmospheric and groundwater contaminations. The present study employed two precipitating agents: sodium dithiocarbamate (DTCR) and 2,4,6-trimercaptotiazine, trisodium salt monohydrate (TMT) to prevent mercury in FGD gypsum from releasing into the environment as Hg-0 and Hg2+. The results indicated that in the presence of DTCR and TMT, Hg2+ in leachate decreased to nearly 10%, while the amount of released Hg-0 declined by over 2/3. Hence, it demonstrated an apparent effect of precipitants on the inhibition of Hg2+ dissolution and Hg-0 re-emission. However, precipitation efficiencies represented better inhibitive performance of DTCR than that of TMT. Further increase of initial pH value and the precipitant dosage had an outstanding effect on the decline of total dissolved Hg2+, released Hg-0 and Hg2+ remaining in leachate. Thus, in some severe conditions such as acid rain prone areas, the stabilization of mercury in FGD gypsum from dissolving and releasing could be extraordinarily controlled by the addition of DTCR and TMT, which is highly promising for future applications. (C) 2012 Elsevier B.V. All rights reserved.