Disclosed are sorbents having superior water leachability performance characteristics especially when used as sorbents in semi-dry (CDS), high moisture (SDA), and fully wet SO2 scrubbers. Also disclosed are methods for the production of such performance-enhanced sorbents, and methods for the use of such sorbents in the removal of mercury and possibly one or more other heavy metals or other contaminants from various gaseous streams. The sorbents are carbonaceous substrates treated with a bromine-containing compound, especially gaseous bromine, and with at least one organic compound that contains at least one olefinic double bond.