AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Contribution of Organic Nitrogen to Secondary PM at a Semi-Rural Site in the Southeastern US
QUENTIN MALLOY, Prakash Doraiswamy, R.K.M. Jayanty, Jonathan Thornburg, RTI International
Abstract Number: 506 Working Group: Aerosol Chemistry
Abstract Previous studies have reported significant contributions of organic nitrogen (ON) species to aerosol in rural and urban regions throughout the world. The role of ON within the total atmospheric aerosol budget is important to understand because of its potential to alter terrestrial and aquatic nitrogen balances. These previous studies have not distinguished between secondary ON and primary ON. This issue is especially relevant in areas known to have large amounts of secondary particulate matter (PM) such as the southeastern US. The lack of data about the contribution of ON to secondary PM is currently a large gap in determining critical nitrogen loads needed for an ecosystem. A part of this critical gap is the role human land management practices (such as cutting) have in cycling of nitrogen within an ecosystem.
Preliminary analysis of data from this mid-summer field study indicate that a significant amount (~11%) of ON can be classified as secondary in nature. Furthermore, data collected immediately after the grass cutting episodes shows no significant deviation from background aerosol with regards to the NO$_3$^- or NH$_4$^+ concentrations. The strong correlation between NO$_3$^- and total organics coupled with the high degree of oxidation (f44/f43 = 1.6) indicate the most likely source of NO$_3$^- in the aerosol is from secondary processing. Measured NH$_4$^+ concentrations show a high degree of correlation with SO$_4$^(2-), indicate the majority of ammonium and sulfate are bound together in the aerosol as ammonium sulfate.