Derivation of agricultural gas-phase ammonia emissions and application to the Cache Valley

Gas-phase ammonia, although not regulated under the Clean Air Act, is a pollutant of concern because it may photochemically react to form fine particles, act as a nutrient after deposition, and negatively impact human and animal health. In this study, whole-facility ammonia emissions from a deep-pit swine-finishing facility near Ames, Iowa and a research dairy in Cache Valley, Utah were derived using inverse-modeling (ISCST3) and an ammonia sampling array. Cache Valley ambient ammonia was characterized through both modeling and measurement during winter and summer conditions. Ambient ammonia samples were collected using Ogawa passive samplers and analyzed via ion chromatography. The ammonia emission rates derived within this study and other literature-reported emission rates were combined with animal counts/activity levels, and wastewater treatment, automobile, and industrial releases to create an ammonia emissions inventory for Cache Valley. A box model and ISCST3 were applied to the Cache Valley for comparison with the measured concentrations.; The calculated swine-finishing facility emission rate was 10.3 +/- 1.9 g/day/pig or 112.7 +/- 20.9 g/day/AU, where 1 animal unit (AU) was set equal to 500 kg of live weight. Dairy emissions were 161 +/- 42.0 g/day/AU for pens not scraped and flushed daily, 6.6 +/- 1.7 g/day/AU for pens that were scraped and flushed daily, 4.1 +/- 1.1 g/d/m 2 for an active lagoon, and 1.3 +/- 0.3 g/day/m2 for an inactive lagoon. If the active lagoon emissions were attributed to those cattle that contributed to it, the emission rate for the pens scraped and flushed daily was 133 +/- 34.5 g/day/AU.; The overall average measured concentration during the Cache Valley ammonia characterization study was 26.7 +/- 3.7 mug/m3, with slight seasonal differences. Concentration patterns were consistent during both seasons, with the highest values measured in the area of the highest livestock density. Total ammonia emissions estimated for Cache Valley were about 12400 kg/d, with 98.1% attributed to livestock. The box model predicted an overall average concentration of 4.4 +/- 4.2 mug/m3. The ISCST3 model predicted an overall average concentration of 19.6 +/- 7.8 mug/m3. Moreover, ISCST3-predicted concentrations followed the same spatial patterns as the measured concentrations.