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Fine‐scale simulation of ammonium and nitrate over the South Coast Air Basin and San Joaquin Valley of California during CalNex‐2010
Author(s) -
Kelly James T.,
Baker Kirk R.,
Nowak John B.,
Murphy Jennifer G.,
Markovic Milos Z.,
VandenBoer Trevor C.,
Ellis Raluca A.,
Neuman J. Andrew,
Weber Rodney J.,
Roberts James M.,
Veres Patrick R.,
Gouw Joost A.,
Beaver Melinda R.,
Newman Sally,
Misenis Chris
Publication year - 2014
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2013jd021290
Subject(s) - san joaquin , environmental science , air quality index , national ambient air quality standards , plume , air pollution , structural basin , hydrology (agriculture) , atmospheric sciences , nitrate , criteria air contaminants , meteorology , geography , air pollutants , geology , chemistry , geotechnical engineering , organic chemistry , soil science , paleontology
National ambient air quality standards (NAAQS) have been set for PM 2.5 due to its association with adverse health effects. PM 2.5 design values in the South Coast Air Basin (SoCAB) and San Joaquin Valley of California exceed NAAQS levels, and NH 4 + and NO 3 − make up the largest fraction of total PM 2.5 mass on polluted days. Here we evaluate fine‐scale simulations of PM 2.5 NH 4 + and NO 3 − with the Community Multiscale Air Quality model using measurements from routine networks and the California Research at the Nexus of Air Quality and Climate Change 2010 campaign. The model correctly simulates broad spatial patterns of NH 4 + and NO 3 − including the elevated concentrations in eastern SoCAB. However, areas for model improvement have been identified. NH 3 emissions from livestock and dairy facilities appear to be too low, while those related to waste disposal in western SoCAB may be too high. Analyses using measurements from flights over SoCAB suggest that problems with NH 3 predictions can influence NO 3 − predictions there. Offline ISORROPIA II calculations suggest that overpredictions of NH x in Pasadena cause excessive partitioning of total nitrate to the particle phase overnight, while underpredictions of Na + cause too much partitioning to the gas phase during the day. Also, the model seems to underestimate mixing during the evening boundary layer transition leading to excessive nitrate formation on some nights. Overall, the analyses demonstrate fine‐scale variations in model performance within and across the air basins. Improvements in inventories and spatial allocations of NH 3 emissions and in parameterizations of sea spray emissions, evening mixing processes, and heterogeneous ClNO 2 chemistry could improve model performance.