The use of neutral aqueous solutions of glyoxal (pH approximately 6 to 8.5) scavenges H2S that is present in natural gas and in oil better than glyoxal alone or base alone. The resulting scavenger combination significantly increases the reaction rate and the overall scavenging efficiency, i.e. capacity over glyoxal used alone. A buffer may be optionally used. In another embodiment, the combination of non-nitrogen-containing surfactants and glyoxal results in a significant increase in the reaction rate and the overall scavenging efficiency, i.e. capacity as compared to glyoxal used alone.