NOVELTY - A plasma-based removal apparatus for removing contaminants from a gas stream has a non-thermal plasma generation device for installation in a conduit; an electrical power source supplying electrical power to the plasma device; a source of plasma gas to create an activated species that reacts with the contaminant to form reactant compound(s); and a removal device for removing the reactant compound from the gas stream.    USE - Used for removing contaminants from a gas stream e.g. from incinerators, boilers, other combustors, utilities, refineries, smelters, manufacturing and other facilities.    ADVANTAGE - The apparatus effectively captures and removes mercury and other volatile and semi-volatile metals and trace species from the gas streams. It can also effectively convert elemental mercury to ionic mercury to aid in capture of the mercury. It results in the capture of gas phase mercury by conversion into mercury compounds that are highly water-soluble. It utilizes highly reactive species in either gas or liquid phase chemistry to ensure a kinetically favored process.    DETAILED DESCRIPTION - A plasma-based removal apparatus for the removal of contaminants from a gas stream comprises a non-thermal plasma generation device (16') adapted for installation in a conduit, where the plasma device is a first treatment device located in a gas stream without an intervening treatment device in the gas stream between a source of gas and the plasma device, and where the gas stream contains contaminant(s); an electrical power source supplying electrical power to the plasma device; a source of plasma gas in fluid communication with the plasma device to create an activated species within the plasma device and discharge the activated species into the gas stream, where the activated species reacts with the contaminant to form reactant compound(s); and a removal device in direct communication with the plasma device for removing the reactant compound from the gas stream.    DESCRIPTION OF DRAWING(S) - The figure is schematic drawing illustrating a plasma-based removal apparatus in which a flue gas treatment system having a gas phase reaction scheme is used with plasma devices distributed radially into a ductwork.    Duct (12')    Non-thermal plasma generation device (16')    Supply lines (22', 24', 26')