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An investigation of ammonia and inorganic particulate matter in California during the CalNex campaign
Author(s) -
Schiferl Luke D.,
Heald Colette L.,
Nowak John B.,
Holloway John S.,
Neuman J. Andrew,
Bahreini Roya,
Pollack Ilana B.,
Ryerson Thomas B.,
Wiedinmyer Christine,
Murphy Jennifer G.
Publication year - 2014
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2013jd020765
Subject(s) - particulates , environmental science , air quality index , ammonia , aerosol , deposition (geology) , atmospheric sciences , ammonium , nitrate , sulfur dioxide , nox , sulfate , ammonium nitrate , environmental chemistry , hydrology (agriculture) , chemistry , meteorology , geography , geology , inorganic chemistry , paleontology , geotechnical engineering , organic chemistry , sediment , combustion
Airborne observations from the California Research at the Nexus of Air Quality and Climate Change (CalNex) campaign in May and June 2010 are used to investigate the role of ammonia (NH 3 ) in fine particulate matter (PM 2.5 ) formation and surface air quality in California and test the key processes relevant to inorganic aerosol formation in the GEOS‐Chem model. Concentrations of ammonia throughout California, sulfur dioxide (SO 2 ) in the Central Valley, and ammonium nitrate in the Los Angeles (LA) area are underestimated several‐fold in the model. We find that model concentrations are relatively insensitive to uncertainties in gas‐particle partitioning and deposition processes in the region. Conversely, increases to anthropogenic livestock ammonia emissions (by a factor of 5) and anthropogenic sulfur dioxide emissions in the Central Valley (by a factor of 3–10) and a reduction of anthropogenic NO x emissions (by 30%) substantially reduce the bias in the simulation of gases (SO 2 , NH 3 , HNO 3 ) throughout California and PM 2.5 near LA, although the exact magnitudes of emissions in the region remain uncertain. Using these modified emissions, we investigate year‐round PM 2.5 air quality in California. The model reproduces the wintertime maximum in surface ammonium nitrate concentrations in the Central Valley (regional mean concentrations are three times higher in December than in June), associated with lower planetary boundary layer heights and colder temperatures, and the wintertime minimum in the LA region (regional mean concentrations are two times higher in June than December) associated with ammonia limitation. Year round, we attribute at least 50% of the inorganic PM 2.5 mass simulated throughout California to anthropogenic ammonia emissions.