A method of removing SO.sub.2 from a flue gas stream including SO.sub.2 includes providing a source of trona and injecting the trona into the flue gas stream. The temperature of the flue gas is between about 600.degree. F. and about 900.degree. F. The trona is maintained in contact with the flue gas for a time sufficient to react a portion of the trona with a portion of the SO.sub.2 to reduce the concentration of the SO.sub.2 in the flue gas stream.