Dry processes, apparatus, compositions and systems are provided for reducing emissions of mercury and optionally sulfur oxides and/or HCl. In an embodiment the copper-based mercury remediation composition comprises a copper ammonium complex having an empirical formula of C2H7CuNO2 or any of the other materials described, which include compositions defined by the formula Cu(NH3)x(lower carboxylate)y, wherein the lower carboxylate is selected from the group consisting of formate, acetate and propionate, x is an integer from 0 to 4, y is an integer from 0 to 2, and x+y is equal to or greater than 1. Sulfur oxides and/or HCl can be additionally reduced by introduction of dolomite hydrate sorbent, and additional mercury remediation chemicals as manganese oxides can be employed. The treated gas stream is treated with a particulate removal device.