Ammonia Emissions from a Large Dairy in California's San Joaquin Valley

摘要

Ambient PM_(10) measurements in California's San Joaquin Valley frequently exceed state and federal PM_(10) air quality standards. During the winter months, a large fraction of the PM_(10) is attributed to secondary particles, including ammonium nitrate and ammonium sulfate. These particles are formed in the atmosphere by chemical reactions between ammonia gas and SO_2 and NO_x gases. They are also primarily in the PM_(2.5) size range, and may lead to violations of the recently promulgated fine particle standard. Although it is believed that up to 60% of the total ammonia emissions result from livestock facilities, including large dairies and feedlots, there is little experimental data to verify it. The University of California has conducted several field studies on dairies and feedlots in the San Joaquin Valley to measure the concentrations of ammonia upwind and downwind. These data have been used to estimate the emissions of ammonia from a large dairy during the winter. We have found that the emissions are highly variable from different parts of the dairy, and that it is necessary to spatially characterize the emissions. This paper describes the results of this preliminary effort to calculate ammonia emission rates from a California dairy.