A method for reducing mercury emission and/or re-emission in cleaned flue gas through control of dissolved mercury species concentration within a wet flue gas desulfurization (WFGD) system is disclosed. One method for reducing mercury emission and/or re-emission through control of dissolved mercury species concentration is to measure the dissolved mercury species concentration of an aqueous alkaline slurry used in a WFGD system and/or measuring mercury concentration of cleaned flue gas from a WFGD system and comparing the same to a predetermined dissolved mercury species concentration value and/or a predetermined mercury concentration value. If the comparison reveals the measured dissolved mercury species concentration or mercury concentration is above the predetermined values therefor, the amount of cyclodextrin additive supplied to the system is increased. If the comparison reveals the measured dissolved mercury species concentration or mercury concentration is below the predetermined values, the amount of cyclodextrin additive supplied to the system is decreased.