Definitions
Ammonia: Ammonia is a colorless, pungent, nitrogenous gas. It volatilizes from a solid or liquid material when the ammonium ion is present and other physical conditions exist. Ammonia gas can react in the atmosphere with gaseous acidic species to form fine particulates (ammonium [NH4+] aerosols), which are a health concern. Atmospheric NH3 can be deposited during rain events and lead to soil acidification and increased concentrations of nitrogen in surface waters, potentially contributing to eutrophication.