AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Development of a Highly Specific and Sensitive Technique to Measure Organic Nitrogen in Atmospheric Aerosols
JACQUELINE HAMILTON, Mustafa Ozel, Lewis Alastair, University of York
Abstract Number: 120 Working Group: Instrumentation and Methods
Abstract Atmospheric particles typically have high concentrations of nitrogen and are a significant source of fixed nitrogen to the environment. While the sources, formation and composition of oxygenated organics in the atmosphere have been extensively studied in recent years, organic nitrogen (ON) has not received the same attention, in part due to a lack of suitable analytical techniques. We have developed a sensitive and quantitative method for the speciation of ON within atmospheric aerosol. Aerosol filter samples were extracted into water followed by solid phase extraction, before analysis by comprehensive gas chromatography with a nitrogen chemiluminescence detection system (GCxGC-NCD). The GCXGC-NCD instrument shows high selectivity, only giving a response for ON compounds and thus removing the complex aerosol matrix. In addition, it gave an equimolar response for most organic nitrogen species, which allowed quantification of total ON content in aerosol samples even when the exact molecular structure was unknown or where standards were not available. It shows high sensitivity, with limits of detection determined to be in the range of 0.16-0.27 pgN. A range of organic aerosol compositions have been analysed including urban aerosol, household dust and secondary organic aerosol formed in simulation chamber experiments. For example, a total of 57 ON compounds were found in urban aerosol collected in Birmingham, UK, (including 10 nitriles, 9 alkyl nitro compounds, 4 nitro-phenols, 4 amides, 3 nitrosamines and 2 nitro-PAHs). The average mass loading of the total identified ON was 532 ngON m$_(-3). The average ON:OC (in terms of ngN:ngC) was 0.022:1 which equates to a C:N ratio of 53. The high sensitivity and selectivity demonstrated by the GCXGC-NCD, makes the technique a significant improvement over previous laboratory methods for ON analysis and it shows promise as a technique to study ON throughout the atmosphere.