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Environmental fate & pathways

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Atmospheric levels of ammonia in urban areas around the world are on average about 20 pg/m3. Non-urban sites have average levels of 4-5pg/m3.  Areas close to point sources (e.g., large animal feedlots or industrial sites) may have local atmospheric concentrations exceeding 200pg/m3. Limited data are available on the concentrations of ammonia in soil. In general, natural levels in soil are low (< 1 mg/kg) because of the rapid conversion of ammonia to nitrite and nitrate by Nitrosomonas and Nitrobacter, respectively. Several studies have been conducted to measure conditions in the injection zone following the field application of anhydrous ammonia. These studies commonly show in excess of 1000 mg/L of ammonia nitrogen and a pH more than 9.0 in the center of the injection zone. These effects rapidly decrease as the distance from the injection point increases, e.g., at 7 cm the ammonium concentration and pH levels are not usually above background.