Effects of ammonia emissions on California air quality

Speaker: John Nowak, CU CIRES & NOAA ESRL CSD

When: Wednesday, October 17, 2012, 3:30 p.m. Mountain Time
Location: Room 2A305, DSRC (NOAA Building), 325 Broadway, Boulder
Directions: Refer to More Information under our Seminar Schedule

ALL Seminar attendees agree not to cite, quote, copy, or distribute material presented without the explicit written consent of the seminar presenter. Any opinions expressed in this seminar are those of the speaker alone and do not necessarily reflect the opinions of NOAA or ESRL CSD.


Ammonia (NH3) from agricultural and urban sources effects terrestrial ecosystems and atmospheric composition, and some of these sources have increased substantially in recent decades. Over the last 50 years world usage of NH3-derived fertilizers has increased by an order of magnitude, resulting in a major increase of NH3 to the ecosystem from agriculture. Major NH3 sources from agricultural activity include animal waste and crop fertilization. In urban areas automobiles equipped with three-way catalytic converters have become a source of atmospheric NH3. These anthropogenic sources increase the burden of NH3 to the atmosphere, where NH3 is the dominant gas-phase base. NH3 in the atmosphere contributes to particle formation. For example, emissions of NH3 and NOx (NO + NO2), which can be oxidized in sunlight to form nitric acid (HNO3), can react to form atmospheric ammonium nitrate particles.

NH3 from agricultural activity and urban centers results in ammonium nitrate formation in both the Los Angeles-South Coast Air Basin (SoCAB) and the San Joaquin Valley (SJV) of California. These regions are designated by the US Environmental Protection Agency (EPA) as being in non-attainment of the National Ambient Air Quality Standards (NAAQS) for both PM2.5 and PM10. Since formation of fine aerosol nitrates from NH3 and HNO3 accounts for a significant fraction of the PM2.5 mass, quantifying the sources of NH3 in theses regions is important for developing aerosol control strategies. Fast-time resolution observations of NH3 and traces gases and aerosols made aboard the NOAA WP-3D aircraft during the CalNex 2010 campaign are used to quantify and compare NH3 sources in California, evaluate their representation in emissions inventories, and determine their impact on particle formation.