- (D) Sulfur dioxide (SO 2 ) leads to the formation of sulfuric and sulfurous
acid. Ammonia (NH 3 ), although a base, does form the ammonium ion
(NH 4 +) which can react with sulfates and nitrates, forming slightly acidic
ammonium salt particles (ammonium sulfate and ammonium nitrate), which
can enter water supplies or the soil. Nitrogen oxides can form nitrous and
nitric acid. Lead does not contribute to acid deposition.