Atmospheric concentrations of ammonia and ammonium aerosols in eastern North Carolina

Fate and transport of ammonia (NH3) emitted from effluent lagoons, housing units, or land application of animal wastes (effluent or litter) is dictated in part by partitioning between ammonia and ammonium aerosols (e.g. NH4NO3, NH4HSO4, (NH4)(2)SO4, NH4Cl) in the atmosphere. Annular denuders were used to measure the atmospheric concentrations (sampling height = 2.6 m) of ammonia and ammonium aerosols in Sampson Co., NC, where there is a high density of large-scale swine and poultry production facilities. From May I, 1998, to July 1, 1998, the mean daytime (12-hr) concentration of NH3 was 5.0 (+/- 1.7) mug N m(-3). Mean nighttime (12-hr) concentration of NH3 was 7.5 (+/- 4.6) mug N m(-3). From Oct. 14, 1998, to Dec. 15, 1998, daytime concentrations of NH3 ranged from 0.4 to 9.9 mug N m(-3), and nighttime concentrations ranged from 0.3 to 7.5 mug N m(-3). From Jan. 20, 1999 to Sept. 13, 1999, the mean daytime concentration of NH3 was 5.17 (+/- 4.51) mug N m(-3), and the mean nighttime concentration was 5.02 (+/- 4.98) mug N m(-3). Ammonium aerosols account for less than 25% of the inorganic nitrogen species in the atmosphere. The relatively high concentrations of atmospheric concentrations of NH3 at this location are consistent with the increase in ammonium (MH,) concentrations in rainwater, and the fraction of NH4-N in wet deposition, which has been recorded during the past 10 years by a nearby (< 0.25 km) National Atmospheric Deposition Program collector (NC35).