A method for treating flue gas may include adding iron to a slurry in a
ratio between approximately 20-to-1 and 5000-to-1 by weight of iron to a
weight of mercury, selenium or other heavy metal to be removed from the
flue gas, and contacting the slurry with the flue gas in a flue gas
desulfurization system. A system for treating flue gas may include a
scrubber, a slurry tank, and a water source. Water and limestone may be
combined in the slurry tank to form a limestone slurry. At least a
portion of the limestone slurry may be used to treat flue gas in the
scrubber. Iron may be added to at least a portion of the limestone slurry
used to treat flue gas in the scrubber. The iron used in either the
method or system may be a ferrous or ferric salt, or elemental iron.